2-page abstracts booklet

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Long Abstracts of Presentations Table of Contents Tuesday 18 December Session 1: Sinter and ironmaking Session 2: Oxygen Steelmaking Session 3: Electric arc furnace Session 4: Flat product hot rolling Session 5: Blast furnace Session 6: Continuous casting Session 7: Long product rolling Session 8: Coating and finishing line Wednesday 19 December Session 9: Energy Session 10: Secondary metallurgy and refractory Session 11: Product and quality management Session 12: Pickling and cold rolling Session 13: Cokemaking Session 14: Slab continuous casting Session 15: Environment and by-products Session 16: Cold rolling FFA – Immeuble Le Cézanne – 6 rue André Campra – F-93212 La Plaine Saint-Denis CEDEX www.acier.org The long abstracts are published in the present CD under the authors' responsibility. They have been printed as drafted by the authors.

Transcript of 2-page abstracts booklet

Page 1: 2-page abstracts booklet

Long Abstracts of Presentations

Table of Contents

Tuesday 18 December

Session 1: Sinter and ironmaking Session 2: Oxygen Steelmaking Session 3: Electric arc furnace Session 4: Flat product hot rolling Session 5: Blast furnace Session 6: Continuous casting Session 7: Long product rolling Session 8: Coating and finishing line

Wednesday 19 December Session 9: Energy Session 10: Secondary metallurgy and refractory Session 11: Product and quality management Session 12: Pickling and cold rolling Session 13: Cokemaking Session 14: Slab continuous casting Session 15: Environment and by-products Session 16: Cold rolling

FFA – Immeuble Le Cézanne – 6 rue André Campra – F-93212 La Plaine Saint-Denis CEDEX www.acier.org

The long abstracts are published in the present CD under the authors' responsibility. They have been printed as drafted by the authors.

Page 2: 2-page abstracts booklet

Session 1: Sinter and ironmaking

Table of Contents

1.1 From ore to steel - Ironmaking processes P. SCHMÖLE (ThyssenKrupp Steel), H.B. LÜNGEN (Steel Institut VDEh), Germany

1.2 HIsarna in the context of alternative ironmaking C. ZEILSTRA, K. MEIJER, C. TEERHUIS, M. OUWEHAND, J. VAN DER STEL (Tata Steel Europe), The Netherlands

1.3

Study of degradation of sinter and method of preventing fines generation D. MITRA, B. DWIVEDI, M. SINHA, U. CHAKRABORTI, P. PRASAD (Tata Steel), India

1.4

The clarification of the effect on sinter productivity with coke split addition method K. KATAYAMA, K. HIGUCHI (Nippon Steel Corporation), Japan

1.5

Selective Granulation Facility Operation in Sinter Plant J.S. PARK, Y.C. KWON, M.S. CHOI, G.R. YOO (POSCO), Korea

1.6

Rogesa's new blast furnace No 5 with a modernised top charging system - 24 months of high performance ironmaking W. HARTIG, H. ZEWE (AG der Dillinger Hütte), Germany, E. LONARDI, G. THILLEN, J. HOLLMAN, L. HAUSEMER, B. MULLER (Paul Wurth SA), Luxembourg

1.7

The EFATM Process - State-of-the-Art DeSOx Technology at ROGESA, Dillingen-Germany W. HARTIG, G. MAURER (AG der Dillinger Hütte), F. REUFER, T. WEISSERT (Paul Wurth Umwelttechnik GmbH), Germany

1.8

The effect of mixing nut coke in the ferrous burden in the ironmaking blast furnace Q. SONG, Y. YANG (Delft University of Technology), H. HAGE (Tata Steel), R. BOOM (Delft University of Technology), The Netherlands

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From ore to steel: Ironmaking processes

Prof. Dr.-Ing. Peter Schmöle (ThyssenKrupp Steel Europe, Duisburg)

Dr.-Ing. Hans Bodo Lüngen (Steel Institute VDEh, Düsseldorf)

Introduction

In principle there are existing four alternative ways to produce steel, figure 1. Three are based on virgin raw materials, like oxydic iron ores and reductants like coal, oil and gas. One is based on the recycling of steel scrap. Amongst the conventional iron ore re-duction route via the blast furnace there exist alterna-tives like the smelting reduction processes Corex and Finex which produce liquid hot metal like the blast furnace, as well as the processes for direct reduction of iron ores which produce solid sponge iron in form of DRI (Direct Reduced Iron) and/or HBI (Hot Briquetted Iron). All gangue materials of the iron ores are re-leased in the sponge iron and need to be separated via the slag during steel making process in an electric arc furnace.

DR - EAF - CC

Scrap

EAF - CC

BF - BOF - CC

Coke

Corex/Finex - BOF - CCCoke

Virg

in ra

w m

ater

ials

Scra

p

Figure 1: Alternative ways to produce steel

To compare the different ironmaking process routes with respect to pre-agglomeration steps integrated export/import energy and material balances are re-quired, figure 2. The charge materials for the shaft process blast furnace need to be prepared and agglomerated. The coking plant produces high quality coke from coking coals. In sinter plants fine grained iron ores are agglomerated. The operation of a blast furnace without coke is not possible, as the coke

guarantees permeability of the burden column in the cohesive zone, where the iron ores soften and melt, and drainage of the produced liquids hot metal and slag.

Coking coal

Sinter Coke

Electric power

Oxygen

Non Coking coal

Crude steel via BF

Non Coking coal

Coking coal

Briquetting

Oxygen

Electric power

Drying

PSA

Coke

Crude steel via Finex Crude steel via DR

Oxygen

Electric power

Natural gas

Fine ore, pellets,lumps

Coal Coal

Briquetting

Drying

PSA

Fine ore Fine ore, pellets, lumps

Figure 2: Export/import energy and material balance

The agglomeration of fine grained iron ores is also necessary for use in the Corex smelting reduction process and in the shaft furnaces of direct reduction processes, for example Midrex and HyL III process. The fluidized bed based smelting reduction process Finex and the direct reduction process Finmet are able to directly reduce fine ores without agglomera-tion. The direct reduction processes are able to pro-duce without the use of coke. The smelting reduction processes Finex and Corex need some minor amounts of coke especially to guarantee the perme-ability of the hearth of the melter gasifier and the process stability.

Process developments

The coke based blast furnace has a development history of 303 years. In 1709 the daily hot metal pro-duction of a blast furnace amounted to 2 t, production of large sized blast furnaces today amounts up to 15000 t hot metal per day. The daily production record known by now is 17000 t HM/d hold by POSCO’s blast furnace 4 in Pohang.

The development of alternative ironmaking processes was driven by the target to avoid the need of coke. Since the 1950ies around 72 processes for direct reduction of iron ores were invented and tested; some of them are today in industrial application, like the shaft furnace processes Midrex, Danarex and HyL III, the fluidized bed reduction process Finmet, some rotary kiln processes and rotary hearth processes as well as the multiple hearth furnace Primus (Primorec). As the direct reduction processes do not produce liquid hot metal quality like the blast furnace the de-velopment of iron ore reduction processes which pro-duce hot metal without coke started in the 1980ies. 59 process developments are listed of which up to now only the Corex and Finex processes reached indus-

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trial application. It has already been mentioned, that these do not operate up to now 100 % coke-less.

Status Quo

The world steel industry produced 1.517 billion t crude steel in 2011, for which 1.690 billion t metallic charge materials were needed, figure 3. The major amount, 64.7%, was hot metal supplied by blast furnaces, 0.4% was hot metal from smelting reduction plants. 30.6% was supplied by the recycling of steel scrap and 4.3% by DRI/HBI.

15171690

0

500

1000

1500

2000

Crude steel production Metallic charge

Prod

uctio

n [

Mill

. t /

y ]

Oxygensteel

69.6 %

Electricsteel

29.2 %

Hot metalBF

64.7 %

Steelscrap30.6 %Hot metal

COREX /FINEX 0.4 %

DRI / HBI 4.3 %OH

steel 1.2 %

Figure 3: World crude steel production, 2011

The existing capacity of worldwide operated iron ore reduction modules are in a wide range, figure 4. Blast furnaces produce up to 5.3 mill t/y, shaft furnace direct reduction processes HyL III 1.95 mill t/y and Midrex 1.8 mill t/y. Corex and Finex smelting reduction plants in operation produce up to 1.5 mill t/y hot metal. The third Finex plant under construction at POSCO in Pohang is designed for a production of 2.0 mill t/y HM.

5.30

1.95 1.801.50

0.55 0.500.25

0

2

4

6

Blast F

urnac

eHyL

Midrex

Corex / F

inex

Finmet

Rotary H

earth

Rotary K

iln

Cap

acity

[ M

ill. t

pro

duct

/ y

]

Figure 4: Module capacities of reduction processes

Ideas for the future

Future developments for iron ore reduction processes are – especially for the region Europe and Asia – di-rectly linked to the request to decrease CO2 emissions in steelmaking. The European ULCOS project, figure 5, includes a blast furnace process with top gas re-

cycling, the HIsarna smelting reduction process as a combination of the HIsmelt process and the CCF process (converted cyclone furnace), natural gas based steel production and hydrogen based steel production. Efforts are on the way on the level of ex-perimental scales or pilot plant scales. The first trials showed that specific plant operation CO2 mitigation is on the level of 20 % compared to the conventional blast furnace. Massive CO2 mitigation requires CCS (CO2 Capture and Storage). The top gas recycling blast furnace process requires a new evaluation of the total energy network of an integrated iron and steel works.

Figure 5: European ULCOS project (Ultra Low CO2 Steel Making)

Conclusions

There are really existing many ways to produce steel. Looking to the S-Line-Model it is questionable where the way goes, figure 6.

Formation Growth Maturation Seniority

Tech

nolo

gy p

erfo

rman

ce

Corex

Blast furnace

Finex

Finmet

Rotary kiln

ITmk3

Rotary hearth

?Midrex, HyL

DR processes in combination with EAF

Figure 6: The S-Line-Model

The further evolution of process acceptance is not only driven by technical development, economy and efficiency but also by policy requirements mainly based on CO2 arguments. It is also questionable which effects price factors regarding raw materials, reductants and energy may have. With respect to the production routes based on iron ore reduction processes there are no winners, there are just best solutions with respect to the boundary conditions. The developers of all production routes are doing pioneer work for finishing good solutions.

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HIsarna in the context of alternative ironmaking C. Zeilstra (Tata Steel Europe)

K. Meijer (Tata Steel Europe)

C. Teerhuis (Tata Steel Europe)

M. Ouwehand (Tata Steel Europe)

J. van der Stel (Tata Steel Europe)

1. INTRODUCTION

2. WHY SMELTING REDUCTION?

3. HISARNA

4. PILOT PLANT

5. OUTLOOK

1. Introduction

The blast furnace has been the ironmaking production route of choice for centuries and especially in the last fifty years, many optimizations have been made to increase productivity and minimize reducing agent requirements.

Despite the enhanced performance, ironmaking routes other than the blast furnace are in development as well. These routes - although sharing a common denominator (‘alternative ironmaking’) - include processes using coal as well as natural gas and processes producing a solid product (HBI/DRI) as well as processes producing liquid iron. This contribution, however, will focus on a smaller group of these processes, named Smelting Reduction.

As the name suggests smelting takes place in these processes and a liquid product is produced. A further characteristic is that these processes use coal as reductant, not coke or gas. Some of the processes that can be considered Smelting Reduction processes are: Corex, Finex, Tecnored, AISI Direct Steelmaking, DIOS, Romelt, Ausiron, HIsmelt, CCF and HIsarna.

The blast furnace is well established and even a development promising to match its performance is not good enough. In order to justify the development risk of such new technologies, blast furnace performance needs to exceeded, for example in the fields energy efficiency, raw material flexibility, maintenance performance and costs.

In this contribution, the different aspects of new Ironmaking technologies are discussed, in order to establish why these developments are worthwhile to pursue.

2. Why smelting reduction?

In the 1980s and 1990s, expected shortages in high quality coking coal were considered threats to blast furnace Ironmaking and an important reason for developing smelting reduction technology, which could use thermal coals. However, in the last decade several other factors came up as well.

In order to develop more sustainable products and processes, the steel industry took its responsibility and all over the world projects were initiated to investigate CO2 lean production methods. These projects quickly focussed on the ironmaking process, for being by far the most CO2 intensive step in the production chain. The drive for sustainability caused a renewed interest in smelting reduction.

The iron ore supply has drastically changed as well. Due to the rapid growth of the steel industry in Asia the demand for iron ore strongly increased and so did the price. A process capable of using iron ores outside the standard quality range, that appeared uninteresting 10 years ago, would be a highly sought after asset today.

iron

Coal

Oxygen

Iron oreOxygen

CO2

iron

Coal

Oxygen

Iron oreOxygen

CO2

Figure 1: HIsarna process

3. HIsarna

The HIsarna process is a development of the ULCOS (Ultra Low CO2 Steelmaking) project in cooperation with HIsmelt. The ULCOS program was launched in 2004 on initiative of the major players in the European Steel Industry to find innovative and breakthrough solutions for reducing CO2 emissions of steel makers. Since the Ironmaking step is responsible for the major part of these emissions, research is mainly focused in that area. Many different technologies have been evaluated after which the four most promising ones where selected for further evaluation and testing. One of these is the smelting reduction technology named HIsarna.

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The HIsarna process can use fine ores and fine coals directly with drying and grinding as the only pre-processing requirements. This means that neither coking nor iron ore agglomeration processes are needed. HIsarna further combines the HIsmelt bath smelting technology with ore smelting and pre-reduction in a cyclone (see Figure 1). This cyclone technology originates from an earlier development, the Cyclone Converter Furnace (CCF), a development from, at that time, British Steel, Hoogovens and Ilva. In contrast to other pre-treatments steps, such as a reduction shaft or fluidized bed, the cyclone is directly connected to the smelter and the smelter gases are neither cooled nor cleaned before they enter the cyclone. It is the only pre-reduction technology that allows integration of both stages into a single reactor vessel. The chemical, as well as the thermal energy of the smelter gas is utilised in the cyclone. (See Figure 2)

5. Outlook

What is the outlook of smelting reduction? Will we see it any differently 20 years from now?

The blast furnace is still by far the dominant ironmaking technology. Replacement of the blast furnace is unlikely to happen and shouldn’t be the measure of success for smelting reduction. Even a niche application of smelting reduction in coexistence with the blast furnace, must be considered a success and can justify a new development.

The environmental challenges appear manageable with improved but existing technologies. The CO2 issue is more complicated and will require substantial development efforts.

The high costs of high quality iron ore (high quality from the point of view of the blast furnace operator) form a new and compelling reason to investigate processes with the capability to operate with lower grade ores. The blast furnace will also be driven in this direction. The question remains: Can the blast furnace reduce its dependency on prime iron ore qualities like it did with coking coals or is this the opportunity for smelting reduction?

Fluid bedCyclone

The HIsarna process, like the HIsmelt smelter technology it incorporates, is capable of using iron ores with higher levels of P and Ti than allowed in the blast furnace.

Other benefits of the HIsarna process are: • Reduction of the CO2 emissions per ton with 20 %,

with 80% if the process is combined with CCS. Figure 2: Pre-reduction of iron ore for different temperatures and CO2 / (CO + CO2) [%] • Elimination of coke and sinter/pellet plant

emissions Although developed with CO2 mitigation in mind, HIsarna is capable of using non-coking coal qualities and low cost iron ores as well.

• Use of non-coking coal qualities • Use of low cost iron ores, outside the blast furnace

quality range • Economically attractive even at small unit size (0.8

– 1.2 M thm/y) 4. Pilot plant

Although the two parts of the HIsarna process have both been experimentally tested before, the combination of both reactors (CCF cyclone and HIsmelt bath) is new. Furthermore, the HIsmelt operation with pure oxygen has also never been tested. Therefore a pilot plant was designed and constructed to investigate the new process.

The first experimental campaign with the HIsarna pilot plant has been a major step in the development of this process, but it will require further campaigns at pilot plant scale and most likely one additional scale up step to bring the technology to maturity.

The challenges and development risks are high but so are the expected rewards. In April 2011 the HIsarna pilot plant was completed

and the first experimental campaign started. 3 start-ups were successfully carried out and on May 20th 2011 the first metal was tapped from the pilot plant. It was a major milestone for the technology and for the HIsarna team. However, a technology like this does not achieve technical viability in one campaign. Two more trial campaigns for the pilot plant have been scheduled. One of the objectives will be to achieve longer stable operating periods.

Acknowledgements

The authors like to acknowledge the partners in the ULCOS project, ArcelorMittal, ThyssenKrupp Stahl Europe, LKAB, SSAB, Voestalpine, Rautaruukki, Dillinger Hüttenwerke, Saarstahl, Riva, Paul Wurth, Küttner, and Rio Tinto for their active participation and other contributions to the HIsarna project. The authors further like to acknowledge the European Commission 6th Framework Programme, the European Research Fund for Coal and Steel and the Dutch Government for their financial support.

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Study of degradation of sinter and method of preventing fines

generation

Debanik Mitra, B K Dwivedi, Ujjal Chakraborti, P R Prasad

(Tata Steel Ltd, Jamshedpur Works, India - 831001)

INTRODUCTION Sinter is a brittle substance which breaks into smaller fraction during its transfer from sinter plant to the blast furnace. The bonds in sinter are not strong enough to withstand shock and impact during handling. Therefore, no matter how much care is taken, sinter will produce some amount of undersize, i.e. -5 mm fraction, during its transit from a sinter plant to the blast furnace. This undersize, also called the Return Fines (RF), is recycled into sinter mix converting it back to product sinter. Thus RF is a reject, which needs rework. Higher amount of RF reduces throughput and increase cost of sinter. To control RF from blast furnace is a common problem faced by sinter plants around the globe. Sinter RF varies from 8% to 30% at various sinter plants of Tata Steel Ltd (TSL). The factors affecting generation of RF are summarized in Table 1. Sl No

Factor Impact

1 Collision at transfer points with other sinter and / or metal plate

Low

2 Momentum of sinter particle at the time of impact

Medium

3 Strength of sinter given by the shape, size and strength of the bonds formed

High

Table 1 : Factors affecting RF Generation Factors 1 and 2 depend on the hardware and spatial arrangement of the transfer points. It varies from one location to other. However, factor 3 is fundamental of sinter making process and is independent of the physical condition of a plant. The present work is related to factor 3. It was inspired by a spell of high RF from G blast furnace of TSL Jamshedpur works (Fig. 1). A preliminary investigation revealed that the past work concentrated on improving the transfer chutes and breakage of sinter during handling. A study on improving sinter strength by process optimization was carried out in Tata Steel in 2009[1].

However, no work could be found which directly attempted to reduce the sinter return fines.

Fig 1: High RF from blast furnace G Existing measures of sinter strength is ISO Tumbler Index (TI). However, there is no direct correlation between the amount of return fines with strength, as shown in Fig 2.

10

15

20

25

30

75 75.5 76 76.5 77 77.5Tumbler Index (+6.3 mm), %

RF

from

G B

F, %

Fig. 2: Effect of Tumbler Index on RF Experiment Set-up : A new experimental set-up was designed. A sample box having dimension 300x300x 450 mm was made of mild steel. When a piece of sinter was allowed to fall freely into the box from a fixed height, it disintegrates but remains within the sample box. The amount of return fines produced is known by measuring the weight of -5 mm fraction after each fall.Number of experiments were conducted using plant samples. Result shown in Fig 3.

Fig. 3: RF generated for height & size range

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Fraction-wise Tumbler Index, SP2

74.7

78.7

77.3

79 3

75

76

77

78

79

80

76.7

72

73

74

10-15 mm 15-25 mm 25-40 mm 40-50 mm +50 mm

Fig 4: Special Tumbler Test Special tumbler test was conducted to confirm of size effect (Fig. 4). Fig 3 and 4 revealed that sinter of size range 15-40 mm is most stable and generates minimum return fines. In other words, to reduce RF it is necessary to increase the proportion of sinter in the size range 15-40 mm. Process Optimization: To find out the optimum process parameters, Design of Experiment (DOE) was conducted. The factors chosen for DOE (Table 2) was derived from the past work(1). For better reliability full factorial experiment with one repetition of each experiment was done with plant sinter sample. Factor Low High Bed Height, mm 560 580 Machine speed, m/min 2.20 2.80 Carbon rate, kg/t 32 40 Table 2: DOE factors and levels Result of DOE was analysed using ANOVA table and response surface method (Fig 5).

t ed Su ace Va able R _Med2**(3-0) design MS Residua = 0542507

DV R _Med

3 6 3 2 2 8 2 4 2 6

558 560 562 564 56 574 576 578 580 5823

32

33

4

5

6

7

8

39

40

4

t ed Su ace Va able R _Med2**(3-0) design MS Res dual= 0542507

DV R _Med

3 2 8 2 6 2 4 2 2 2 8

558 560 562 564 566 568 570 572 574 576 578 580 5822 5

2 55

2 60

2 65

2 20

2 25

0

5

0

0

Spee

d

Optimu

Fig 6: Microstructure analysis of sinter RF Following facts were revealed by this analysis. As the sinter size decreases from 40 mm to 10 mm:

1) Hematite phase in RF decreases 2) Slag phases (ferrite+silicate) in RF increases 3) Smaller fractions of sinter produced after

impact is primarily the brittle slag phases 4) Sinter of size 25-40 mm is strong because of

a good balance between relict hematite & slag phases present in it.

Based on the above analysis, following actions were taken in the plant:

(a) Bed height speed and carbon rate optimized based on DOE

(b) Top size of iron ore fines reduced to <8 mm from <10 mm

(c) Finer crushing of lime powder. Minus 1 mm in lime increased from 75% to >85%

(d) Improve bed filling at SP3 and SP4 by improving the charging station

Effect on RF is shown in Fig 7. Tumbler index also increased.

1617181920212223242526

Dec

-09

Feb-

10

Apr

-10

Jun-

10

Aug

-10

Oct

-10

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-10

Feb-

11

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-11

Jun-

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-11

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-11

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-12

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12

Sint

er R

F, %

Sinter Return Fines of G BF

Step 1: SP2 only

Expt Stage 1

Expt Stage 2

Step 2: SP2+SP3

Stabilization by DM

Target <20

Project start

C_R

ate

Fig 5: Analysis using DOE data

Bed Ht Bed Ht

Based on the above analysis, the optimum band of operation was determined as

• Bed height 560-570 mm • Speed 2.3-2.5 m/min Fig. 7: Lowering of RF at TSL Blast Furnace • Carbon rate 32-37 kg/t

Conclusion: Microstructure Analysis: In order to to know the fundamental difference among various size fractions of sinter, microstructure of the sinter fines was analysed. Sample was screened to have various size fractions (+40 mm, +25, +15 mm etc) and then modified tumbler test was performed. The various size fractions after tumbler test were separated and then subjected to microstructure analysis. Results are summarized in Fig 6.

1) Sinter Return Fines (RF) depends on inherent sinter strength

2) Strength varies across the size spectrum; 15 to 40 mm being the most stable

3) The finer fraction generated are mainly the slag phase and/or the loosely bound partial sinter matrix

4) Sinter RF can be controlled by optimizing process parameters such as bed height, machine speed and carbon rate

Ref: 1) Mitra D et al, Tata Search 2010, pp 157-162

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The clarification of the effect on sinter productivity with coke split

addition method

K. Katayama, K. Higuchi

(Nippon Steel Corporation)

1. INTRODUCTION

Coke combustion influences sintering speed and product yield in sintering process, and increase of coke combustion rate can be effective for improvement of sintering speed. As increasing technology of coke combustion rate, coke split addition method has been developed1). With this method, sintering speed will be increased, but the influence on product yield has not been clear because the relation between coke combustion rate and product yield has not been clarified. In this study, increment factors of coke combustion rate were identified from gas volume and oxygen concentration in exhaust gas. In addition, product yield on each bed height was measured with X-ray CT2). These items were also measured in burnt lime addition condition where gas volume and combustion rate can be increased, the relation between combustion rate and product yield was clarified by comparison of coke split addition and burnt lime addition.

2. EXPERIMENT

2-1. Blending and granulation conditions

Table1 shows blending conditions for raw material. Blend1 and blend2 were used where these burnt lime ratios were different and the sinter chemical properties were the same.

Table1 Blending conditions for raw material

Fig.1 shows granulation conditions. On base condition, blend1 was mixed for 60 seconds and granulated for 240 seconds with drum mixer. In burnt lime addition case (case1), blend2 was mixed and granulated with the same operation. In coke split addition case

(case2), blend1 without coke was mixed for 60 seconds and granulated 220 seconds, and then it was granulated for 20 seconds with coke. Moisture of raw mixture was 7.5% in all cases.

Granulation 240s

Mixing(dry) 60s

Blend1/Blend2

Base/Burnt lime

addition (case1) Coke split addition (case2)

Granulation 20s

Coke breeze

Blend1(without coke)

Granulation 220s

Mixing(dry) 60s

Fig.1 Granulation conditions

2-2. Sintering condition

Sintering test for measure of coke combustion properties and sinter cake density was carried out with suction 12.0kPa constant and CO, CO2, O2 concentrations of exhaust gas were analysed per 5 seconds. Density of sinter cake was measured per 30mm with X-ray CT. According to the density, Solid matrix and pore were classified. The density of solid area was more than 1.6g/cm3. The density of un-sintered part was especially more than 1.6g/cm3 and less than 2.2g/cm3. In addition, the test for temperature measuring in sintering bed was done in base and case2. Total bed height was 600mm, and temperature was measured at 450mm, 300mm and 110mm each in height with thermocouples.

2-3. Calculation of coke combustion properties

CO and CO2 in exhaust gas were derived from coke, ignition gas and lime stone. It was assumed that all ignition gas was combusted and all lime stone was decomposed, coke combustion rate rc after ignition calculated with equation (1).

rC=(CO+CO2)/100×Q×1000/60×CaCOKE/( CaLS+CaCOKE) / 22.4 -----------(1)

CaCOKE=(CaTOTAL–CaLPG–CaLS) --------------------(2)

CaTOTAL=(CO+CO2)×Q×T×1000/22.4--------------(3)

CaLS=CbLS---------(4), CaLPG=CbLPG----------------(5)

Where, rC :coke combustion rate (mol/s) CaCOKE :consumed carbon by coke combustion (mol) CaTOTAL :total carbon in exhaust gas (mol) CbLPG :input carbon derived from ignition gas (mol) CaLPG :consumed carbon of ignition gas (mol) CbLS :input carbon derived from lime stone (mol) CaLS :consumed carbon by LS decomposition (mol) CO : exhaust gas CO (%), CO2 : exhaust gas CO2 (%)

Blend1 Blend2 Blending ore (%) 82.85 83.55 Lime stone (%) 13.10 11.40 Burnt lime (%) 1.00 2.00 Peridotite (%) 3.05 3.05 Return fine (%) 15.00 15.00 Coke breeze (%) 5.00 5.00 Total (%) 120 120

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Q : gas volume (Nm3/min), T : sintering time (min)

Additionally, gas volume Q and oxygen availability by combustion ηO2 were selected as factors which were related with combustion rate, and ηO2 was calculated with equation (6).

ηO2 = ( 21-O2 ) / 21 ---------------------------(6)

Where, O2 : exhaust gas O2 (%)

3. RESULTS AND DISCUSSION

3-1. Comparison of coke combustion rate

Table2 shows flame front speed FFS, product yield η and rc. In both case1 and case2, FFS was improved by increment of rc. Fig.2 shows time series variation of ηO2 and Q. It was found that rc was increased by ηO2 improvement in case2, and increment factors were different between case1 and case2. Fig.3 shows microscopy images of raw mixture. ηO2 could be improved without adhering layer on coke surface.

Table2 FFS, product yield η and rc

0.0

0.1

0.2

0.3

0.4

ηO2

(%)

1.0

1.5

2.0

2.5

3.0

0 5 10 15 20

Q (

Nm

3 /min

)

Sintering time after ignition (min)

BaseCase1Case2

Fig.2 Time series variation of ηO2 and Q

Fig.3 Images of raw mixuture (base and case2)

3-2. Comparison of product yield

Fig.4 shows CT images of sinter cake and fig.5 shows CTL on each bed height. CTL was ratio of un-sintered area to total solid area, and product yield was low when CTL was high. In both case1 and case2, rc was higher and CTL on upper part was improved. But

especially in case2, CTL on upper part was furthermore improved. This could be due to ηO2 improvement. Table3 shows maximum temperature in base and case2. Temperature on upper part was increased in case2. From these results, it was found that CTL on upper part where temperature was lower was improved by increasing temperature with coke split addition method.

Fig.4 CT images of sinter cake

Base Case1 Case2 FFS (mm/min) 31.0 35.0 34.1 η (%) 63.1 66.4 73.9 rc (mol/s) 0.065 0.078 0.081

Fig.5 CTL on each bed height

Table3 Maximum temperature (base and case2)

4. CONCLUSIONS

Sintering test and density measurement of sinter cake with X-ray CT were done to clarify the relation between coke combustion properties and product yield. It was found that ηO2 was improved with coke split addition. As the results, FFS was increased by increment of coke combustion rate and product yield on upper part was improved by increasing maximum temperature in sintering bed.

REFERENCES 1)Y. Ishikawa et al., The 2nd International Symposium on Agglomeration Proceedings , 6 (1977), 503

2)T. Inazumi et al., Tetsu-to-Hagane, 78 (1992), 1061

Maximum temperature (K) Base Case2 at 450mm height 1414 1433 at 300mm height 1564 1569 at 110mm height 1587 1524

Case2Case1 Base

0

100

200

300

400

500

600

20 30 40 50 60 70

Bed

Hei

ght

(mm

)

CTL (%)

BaseCase1Case2

Base Case2

Coke Coke

500μmAdhering layer

Page 11: 2-page abstracts booklet

Selective Granulation Facility Operation in Sinter Plant

Ji-Sung Park (Pohang Works, POSCO)

1. INTRODUCTION

Looking at the recent international environmental change on steel Industry, first of all, quality of iron ore is getting worse due to iron ore depletion. As a result of that, using ratio of ultrafine ore such as pellet feed, MAC is continuously increased. This kind of ultrafine raw materials cause productivity down by decrease of permeability in sinter process. To conclude, increase of productivity is needed by enhancing granulation against deteriorating material conditions. For this reason, we decided to install selective granulation facility at Pohang works. I’ll introduce outline of selective granulation facility, optimization of operation and result in this paper.

2. OUTLINE OF FACILITY

When we decided type of granulator and facility layout, strong mixing and granulation power are needed considering using dust and sludge about 40% as raw material of selective granulation facility. Furthermore , there is no enough area, because the facilities are added on existing sinter machine. After investigation and several experiments, we decide to use ‘High Speed Agitation Mixer’ which have a very strong mixing power and ‘pelletizer’. And the new type granulator line which somewhat different from the conventional pelletizer is developed. Explaining the difference, after screening iron ore, a couple of hoppers are installed to feed dust and sludge and then green balls are added after first drum mixer to prevent pseudoparticle from breaking in drum mixer. Next, taking a look at capacity of facility, cutting point of screen is 5mm in light of granulation efficiency and blocking of screen. Inner volume of high speed agitation mixer is 6.3m3 and this large inner volume and powerful agitation ability is reflected against dust and sludge usage. Pelletizer diameter and rim height have direct influence on granulation because those factors decide residense time in pan. So, pelletizer capacity was designed as big as possible that diameter is 7.5m, rim height is 800mm.

Fig. 1 Outline of Selective Granulation Facility

3. OPTIMIZATION OF OPERATION

There are several factors to improve granulation such as watering quantity, position, pelletizer RPM and dust ratio. I’ll explain how to opimize operation

3.1 Adjustment of Moisture

Moisture is major determinant for size and strength of green pellet. For example, moisture of green pellet and watering position should be optimized. First, moisture of green pellet should be adjusted in accordance with material condition such as size and crystal water of raw material. Fig2 shows that using ratio of ultrafine material such as pellet feed and dust is increased, more water is required for binding to maintain green pellet size because of surface area rise. The correlation between dust ratio and the moisture of green pellet is defined by the follwing Eqs.

y = 0.08x + 10.2

x: Dust Ratio, y: Green Pellet Moisure

Fig. 2 Relationship between dust ratio and moisture

And, specific size of green pellet should be managed because the size increses with water but strength is degraded, excessive moisture of green pellet also

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causes decrease of permeability by accumulation of moisture in the lower part of sinter cake. Standard mean size at Pohang works is about 4mm. Second, position of watering also is handled for uniform moisture of green pellets. We tested change of agglomeration with watering position. From the test, watering in hight speed agitation mixer than pelletizer is more effective in formation of Pseudoparticle. The reason why watering in hight speed agitation mixer is easy for uniform agglomeration is strong agitation between raw materials and water by beater of mixer. And, it is necessary that water addition must be performed preferably in the place where core formation is started in pelletizer. If adding water to particles which already formed cores makes excessively large green pellets.

3.2 Fine/Core Ratio for Green Pellet Strength

As mentioned above, size of green pellet is managed by controlling moisture. But strength improvement is improtant as well. If strength of green pellet is weak, it is easy to be broken on the process of transportation or sintering, And it causes deterioration of both productivity and quality of sintered ore due to suction pressure deviation. The one of the most important factor for strength is Fine/Core ratio becasue this ratio decides density. The graph in the Fig.3 is illustrated on the supposition that fine is same with dust. As seen Fig.3, strength increases with dust usage untill specific level. But strength is dramatically declined after the critical point. Comparing with microscope picture, the green pellet which mixed over 50% dust has a lot of pores. this is why strength decreases after specific point. For this reason, dust using ratio over 50% is sublated. And waterful by-product such as sludge is dried under 10% moisture on the yard for using in selective granulation facility.

Fig. 3 Strength Change with Fine/Core Ratio

3.3 Pelletizer RPM

Pelletizer RPM has a close relation with efficiency of granulation because pseudoparticle is formed by falling from upper part of pelletizer to lower part. So the key point of adjustment in RPM Is maximizing the distance of falling on the rotation process of pelletizer.

Thus, it is absolutely needed to find optimized RPM because underspeed than optimized RPM can’t raise raw materials to the highest point and over speed causes continuous rotation not falling with frictional force in pelletizer. Optimum RPM depends on kinds of raw material and productivity of green pellet. For example, pelletizer RPM increase is required if dust ratio and productivity are increasd, to avoid deterioration of raw material flow .

4. EFFECTS

Compared before and after Pseudoparticle size distribution change, great change of 3~5mm and 0.25~0.125mm ratio is showed. Indicating quantitative data, 3~5mm ratio increases about 22% and 0.25~0.125mm ratio decreases about 20%. As a result of operation using selective granulation facility productivity is increased about 1.1~1.2t/d/m2 due to significant improvement of permeability in sinter bed.

Fig. 4 Effects of Selective Granulation Facility

5. REFERENECES

[1] Pelletizing of Iron Ores (Kurt Meyer, 1980)

[2] Size Enlargement by Agglomeration (Wolfgang Pietsch, 1990)

[3] Mechanism of agglomerate growth in green pelletisation (K.V.S. Sastry and D.W. 1973)

[4] Industrial Minerals & Rocks (Kogel, 2007)

Page 13: 2-page abstracts booklet

Rogesa's new blast furnace No 5 with a modernised top charging

system - 24 months of high performance ironmaking

W. Hartig, H. Zewe (Dillinger Hütte)

E. Lonardi, G. Thillen, J. Hollman, L. Hausemer and B. Muller (Paul Wurth S.A.)

INTRODUCTION

During the general overhaul of ROGESA’s blast furnace n°5 in Germany, the latest Paul Wurth G3 Chute Transmission Gearbox (CTG-G3) was installed. At the same time Dillinger Hütte took the opportunity to modernize its pulverized coal injection plant and installed the most advanced Paul Wurth PCI technology using individual flow rate control. The CTG-G3 is based on proven principles and incorporates an extensive 40 years of experience in BLT® charging technology. A cost-effective design ensuring reduced maintenance and increased lifetime potential has been developed by combining know-how with the use of modern simulation tools.

Figure 1: CTG-G3 on BF-5 at Dillinger Hütte

The first industrial implementation on Rogesa’s BF5 has been in successful operation since October 2010 [1]. A second CTG-G3 has been through full testing in Luxembourg and will be delivered in fall 2012 for BF-1 of the new TATA Kalinganagar plant in India. This paper highlights technical features and advantages of the new CTG-G3 and PCI plant.

DEVELOPMENT OF THE CTG-G3

Today’s blast furnace operation requires additional cost management by decreasing the coke rate and maximizing the pulverized coal injection rate. More stringent regulations and ethical considerations require responsible handling of resources and demand a reduced environmental footprint, including the reduction of CO2 emissions, water consumption and pollution. Simultaneously, greater flexibility in blast furnace operation is required to accommodate greater raw material quality variability, while ensuring

higher productivity and increased availability through improved reliability.

Key process characteristics such as shaft permeability, gas utilization and burden descent can be mainly controlled by the BLT charging system, guaranteeing maximum burden distribution flexibility. In order to ensure perfect pulverized coal distribution around the blast furnace perimeter, injection hoppers being equipped with fluidising chambers and downstream installed flow rate measurement devices and GRITKO® flow rate control valves for each injection line have been installed close to the blast furnace. Due to this latest technology a deviation from injection line to the mean value of all injection lines of ± 2 % can be guaranteed. This ensures homogenous tuyere conditions and symmetric operation of the furnace. Growing operational and environmental challenges have been anticipated with the introduction of the CTG-G3. This equipment supplements the existing selection of five conventional gearboxes and is especially but not solely suited for medium to large size furnaces.

TECHNICAL DESCRIPTION OF THE CTG-G3

Among the outstanding features of the CTG-G3 are the newly designed cooling system, the G3 burden distribution chute, the maintenance isolation valve and the condition monitoring system. The overall design has been optimized to increase long-term reliability under high top gas temperatures in a heavily dust-laden atmosphere. The surface area of the rotating part of the equipment exposed to the BF is reduced, providing a simple and effective reduction in the demand on the cooling power requirements of the rotating part. The bottom is now stationary removing it from previous sources of vibration or shocks, which in the past contributed to damage in the lower insulation.

The CTG-G3 incorporates a single, larger diameter bearing to encapsulate both the tilting and rotating motion of the chute apparatus. This provides the benefit of increased maximum load capacity, a reduced number of mechanical components and superior durability under the harshest conditions.

Compact individual drive units are utilized for chute rotation and tilting. Access is excellent. Space requirements reduced to a minimum and gas tightness is improved. The new drives have a greater capacity to cope with higher burden flow rate, and higher chute rotation speed.

The new closed body distribution chute introduces a number of advantages. The structural benefit of a closed body creates higher rigidity which addresses higher top gas temperatures by improving resistance to thermo expansion differentials. This in turn leads to an increased lifetime. The closed body eliminates material spillage at higher rotational speeds and can support increased flow rates. As a result of increased flow rate potential and higher rotational speed of the

Page 14: 2-page abstracts booklet

distribution it is possible to explore more complex charging patterns. Depending on the case a greater number of burden materials can be used or more rings can be used to distribute the burden in the furnace.

A large maintenance door allows quick access and simple “at-a-glance” inspection. It can be removed quickly using one or more pneumatic socket drives. Newly designed hinges facilitate easy opening. This concept keeps inspection times to a minimum.

The new cooling system consists of two pressurized cooling circuits. The first circuit is closed-loop and self-contained in the gearbox rotating components. The second circuit is dedicated to the stationary bottom; it can be connected either to the BF cooling circuit or to a standalone heat exchange system. The direct contact and increased surface area of the cooling system produce higher efficiency (35-50%), and lower operating temperatures compared to traditional gravity fed systems.

The bolt connection to the blast furnace top has been modified to reduce installation time. As a result, the cost of on-site high precision machining of the top flange has been designed-out. In addition, the related sealing gasket is no longer required. These cost reducing measures are achieved, while maintaining the gas tightness guarantee, even in cases of blast furnace top cone distortion.

The conventional isolating “goggle plate”, located at the top of the gearbox has been replaced with a combined isolation valve and compensator. This unit provides gas tightness with structural rigidity and is less sensitive to the dusty environment. The refined design also eliminates adjustment and alignment requirements of the previous system.

Overall dimensions of the CTG-G3 provide interchange-ability with any conventional gearbox. This minimizes the time frame for upgrades.

Key summary characteristics:

Chute length: 3.5 - 5 [m]

Chute rotation speed: 0 - 10 [rpm] Figure 2: Second built BLT® CTG-G3 on test rig

Burden flow rate: 0.3 – 1.1 [m3/s] The closed-loop eliminates contamination of the cooling water from blast furnace dust or debris of any other nature as it is not in contact with blast furnace atmosphere. Possible slow clogging of piping or other cooling devices is thus avoided. As a result, the traditional lower water collecting trough, prone to sludge build-up, is now obsolete, as well as the water-slurry paddles seen in other recently developed systems. Consequently it is maintenance free as the previous periodic cleaning is not required anymore and water consumption is reduced to around 25 [l/day]. Additionally the back flush filter unit and the buffer tank components common to the conventional cooling circuit can be eliminated. The piping and routing have been simplified.

Operating pressure: 1 – 3.5 [bar(g)]

Max. top temp.: 600 (uptakes) / 1000 (centre, short)

An additional benefit of the CTG-G3 gearbox development provides older type gearboxes with some potential for cooling system upgrade during overhaul projects.

CONCLUSION

Successful BF operation is dependent on several key factors, some of which include: use of reliable and predictable equipment, process data recording and analysis, collective know-how and the potential to learn through process simulation with the latest in software models. The design considerations in the new CTG-G3 and modernized PCI plant align very well with each of these factors and are proven in their successful implementation at Dillinger Hütte.

The improved cooling of the tilting gearboxes significantly reduces the risk of seizing in the event of greasing failures. In addition greasing points have been added to the main bearing and tilting gearboxes to increase redundancy. The tilting gearboxes are now greased during shaft rotation with a pump enabling greasing through the full range of chute movement, not solely in a specific greasing position. Maintenance intervals are extended by utilizing new higher volume grease tanks. Implementation of these techniques in cooling and lubrication, ultimately lead to longer equipment lifetime and higher availability. This approach provides a reduction in the total cost of ownership.

REFERENCES

[1]: D. Berdusco, W. Hartig, E. Lonardi, G. Thillen, L. Hausemer, The new BLT® High Performance Chute Transmission Gearbox – results of the first 18 months of operation at Rogesa’s BF5. [2]: E. Lonardi, W. Hartig, G. Thillen, J. Loutsch, S. Devillet, D. Rocchi, L. Hausemer,“The Bell Less Top® GEN3 Chute Transmission Gearbox - A result of 40 years experience”, METEC InSteelCon, 2011.

Page 15: 2-page abstracts booklet

The EFA™ process – State of the Art DeSOx Technology

at ROGESA, Dillingen Germany

Dr. W. Hartig, G. Maurer (ROGESA Roheisengesellschaft Saar mbH, Dillingen

Germany) Dr. F. Reufer, Dr. T. Weissert (Paul Wurth Umwelttechnik GmbH, Essen Germany)

ABSTRACT:

Paul Wurth is very well known in the Iron and Steel industry as an engineering company and supplier of blast furnace equipment and complete blast furnace plants. The German subsidiary, Paul Wurth Umwelttechnik GmbH in the centre of Essen together with ROGESA GmbH, have developed the EFA™ process to industrial maturity in the field of environmental protection. Until now three plants at two locations are in operation to ensure environmental friendly production and low emissions of the sinterplants according to the German clean air act (TA Luft).

The 1st EFA™ plant were built together with the pioneering company ROGESA in Dillingen, to finally reduce the sulfur (and other acid components), dust and dioxin emissions of their sinterplants. The EFA™ technology is the state-of-the-art process for such kind of application in terms of additive and energy consumption, reliability and availability. The report gives an overview of the EFA™ process at Dillingen, the operating installations and the performance results of both plants.

1 Introduction

The process routes for steel making are mainly distinguished by raw material input: Based on iron ore sintering or pelletizing through the blast furnace to produce hot metal, direct or melting reduction and through the electric arc furnace route with mainly scrap and DRI.

Based on the iron ore deposits, more and more fine ores and concentrates are produced which need to be agglomerated for the blast furnace operation. Accordingly, sinter and pellet production increased over the recent years.

2 The Sinterplants of ROGESA

During the last twenty years there have been no new sinterplants commissioned in Europe, therefore, most of the operated sinterplants are already relatively old and their environmental equipment is different from plant to plant. However, the environmental problems

of the sinterplants can be solved to the necessary extent.

At the site of ROGESA which is a joint venture of two steelmaking companies: AG der Dillinger Hüttenwerke and Saarstahl AG, two sinter strands (No. 2 from 1961 and No. 3 from 1981) are in operation. The total sintering capacity amounts to 5 Mio. t/a where strand No. 2 has a suction area of 180 m² and strand No. 3 of 258 m².

3 The Driving Force - Legislative Aspects

Due to the age of the sinterplants the existing gas cleaning systems were no more suitable to fulfil the actual emission limits of the German clean air act (TA – Luft 2002). The local environmental authorities did consequently claim for the renewal of the gas cleaning systems in order to respect the new legislation within a deadline until July 2006 for strand No. 2 in and January 2010 for strand No. 3 at ROGESA in Dillingen. Therefore the new PAUL WURTH Entrained Flow Absorber (EFA™) process has to fulfil the simultaneous removal of dust ( 20 mg/m³ STP), SOx

500 mg/m³ STP), HCl ( 30 mg/m³ STP), HF 3 mg/m³ STP), and dioxins (PCDD/F 0,4 ng/m³

STP). Thereby it has to be flexibility regarding flow and temperature fluctuations and simultaneously regarding the optimization of the reaction temperatures and consequently to minimize the consumables. At least the technology has to be a future oriented safe technology.

The emissions of heavy metals vary between 0,05 to 1 mg/m³ (STP) depending on their classification. The NOx must be lower than 400 mg/m³ (STP). The volatile organic compounds (VOC) measured as total carbon content have to be below 75 mg/m³ (STP).

4 The EFA™ Process

ROGESA (Salzgitter Flachstahl and Longteng, China) have chosen the PAUL WURTH EFA™ technology as a so-called end-of-pipe-solution resp. as a by-pass solution. Together with the existing electrostatic precipitator which kept in operation the Entrained Flow Absorber technology was finally deemed as best and optimum solution for all clients‘ sinterplants due to its best efficiency and flexibility even for the future.

The principle of the PW Entrained Flow Absorber technology is highlighted in Fig. 1 which shows a simplified process flow sheet. The key part of the process is the Entrained Flow Absorber (EFA™). Inside the EFA™ a fluidized bed of recirculated material mixed with fresh additives establishes ideal conditions for the evaporation of the injected water and the removal of the pollutants. Measurements have shown that more than 90 % removal takes place inside the EFA™ and less than 10 % at the filter bags. The EFA™ itself is a rather simple construction consisting of an inlet pipe, the so-called nozzle, where the gas is accelerated, a diffuser and a cylindrical pipe. There are no internal built in components inside

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the EFA™ absorber. At the upper end of the diffuser one spill back nozzle is located, injecting the water cross wise to the gas/solid flow. Due to the well-known excellent mixing conditions in the fluidized bed, the solid particles keep absolutely dry even at high water flow rates. A small layer of water vapor at the surface of the solid particles is responsible for the enhancement of the chemical reactions taking place inside the EFA™.

Fig. 1 The EFA™ process flow sheet

The removal and thus reaction of hydrated lime Ca(OH)2 with the acid components has the following descending order: SO3 > HCl > HF > SO2 > CO2. After Absorber there is no SO3 anymore measurable. Even the HCl and HF amounts are below gauging range.

The desulphurisation efficiency of Ca(OH)2 depends mainly on the gas temperature, moisture content and retention time of the sorbent inside the filter system.

For the temperature control there is an injection of high pressurized water which evaporates and strongly accelerates the reaction of the acidic components. There is no agglomeration of the dust and the temperature is always kept above the dew point.

As an example for the consumption of the additives and the amount of residues: with a raw gas volume of 500.000 m³/h (STP) in order to surely fulfill the actual legislation and guaranteed limits of less than 500 mg/m³ (STP) [from 900 mg/m³ (STP)] of SO2 and 0.1 ng/m³ (STP) [from 4 ng/m³ (STP)] of Dioxins/Furans, 280 kg/h of hydrated lime and approx. 30 kg/h of activated lignite is needed. The expected quantity of residues amounts to 530 kg/h which has to be deposited underground or can be injected via PCI into the blast furnace.

5 Operational Results

With the first installation (PAN1) Paul Wurth faced all problems which are linked to the sinter process and unique. These different challenges with regard to the flow and temperature fluctuations, the bag filter material, adjustment of the closed control circuits in conjunction with the automation system and especially the chemical und physical dust behaviour during operation are all satisfied solved. All optimizations of the process are almost done and the operational results are beyond the expectations in particular regarding the consumables. The value of the stoichiometric relationship is an extraordinary achievement of the optimization progress. Fig. 3

shows the operational results of the emissions in the clean gas of both installations.

Fig. 2 Plant view of the two ROGESA EFA™ plants. (PAN2 in front and PAN1 behind)

Both EFA™ plants are completely in accordance with the German clean air act TA-Luft. The second plant (PAN2) is in operation since Jan. 2011, final acceptance certificate is issued and the plant is operating to full satisfaction of the client. The first installation is in operation since 2006.

PAN1 Guarantee data

PAN1 Actual data

PAN2 Guarantee data

PAN2 Actual data

Flow rate m³/h (STP) wet 600000 480000 810.000 760.000 Temperature outlet °C 120 100 100 100 Dust mg/m³ (STP) dry < 10 < 5 < 10 < 5 SO2 mg/m³ (STP) dry < 500 480

< 500 / 350 < 350

HCl mg/m³ (STP) dry < 10 < <10 < 10 < <10 HF mg/m³ (STP) dry < 1 < 1 < 1 < 1 PCDD/F ng/m³ (STP) < 0,1 << 0,1 < 0,1 < <0,1 (stoichiometric factor) 1,6 1,1 1,6 1,1 - 1,2

Fig. 3 Operat. results of the ROGESA EFA™ plants

6 Summary and Outlook

Sinter plants are important facilities in the production chain of iron making. They are not only producing sinter as iron bearing burden for the blast furnace, but also recycle a lot of valuable secondary materials even to avoid their landfilling. However, the environmental legislation has been continually and strictly tightened concerning the emissions of pollutants in waste gases. ROGESA et al. have chosen to face this liability with maintaining of the existing electrostatic precipitator in conjunction with the Paul Wurth EFA™ process. With these installations the sinterplants are at the top of the environmental development for waste gas, sinterplant off-gas cleaning in accordance with the strict environmental rules even for the future. This technology, the EFA™ process, has become a milestone in sinterplant desulphurization, dedusting and de-dioxination.

Page 17: 2-page abstracts booklet

The effect of mixing nut coke in the ferrous burden in the ironmaking blast furnace

Q. Song1, Y. Yang1, H. Hage2 and R. Boom1 (1. Delft University of Technology, 2. Tata Steel, The

Netherlands)

INTRODUCTION

Ore-coke mixed charging is known as one of the successful techniques for optimizing the charging pattern in ironmaking blast furnace. Traditionally blast furnace is operated with thick coke layers for maintaining a relatively high permeability in the cohesive zone. In recent years, charging small size coke (nut coke) into the burden layer is applied for saving raw materials and decreasing the production cost [1-5]. Although the mixed charging, especially charging nut coke into the burden layer, has many advantages, for various reasons the mechanisms for this phenomenon are still not very clear and the mixing ratio is still limited in actual blast furnace operation. Thus, the authors studied the effects of nut coke on the reduction, softening and melting, and permeability in this paper and aim to reveal the mechanism of the effect of nut coke on the performance of blast furnace.

EXPERIMENT

The experiment was conducted in RSM (Reduction, Softening and Melting) facility under simulated blast furnace conditions as shown in Figure 1. A graphite crucible with a sandwiched sample bed locates in the hot zone of the furnace. The gas flow rate of CO, H2, CO2 and N2 are controlled by four mass flow controllers (MFC) and a computer. The off-gas is analysed continuously by an online gas analyser. Pressure drop over the sample bed is measured by pressure sensor. The expansion and contraction of the sample bed is measured by a displacement sensor. All the data are logged by a data logger and a computer. The molten iron and slag are collected by a sample collector under the furnace tube.

The weight of pellet and total coke rate are kept constant in all cases. Mixing nut coke into pellet layer means that decreases the thickness of both top and bottom coke layer. The size range of pellet and nut coke are 10~15mm, respectively. The reduction

experiment was conducted in a changing temperature and gas profile following an actual blast furnace.

Figure 1 Schematic view of RSM

RESULTS AND DISCUSSIO

Macro structural

Figure 2 is a typical macroscopic picture of mixed burden cross section (quenched firstly then cutting the crucible). The experiment was interrupted at different temperature (900oC, 1100 oC, 1200 oC, 1300 oC, 1400

oC) under the conditions of RSM temperature and gas profile. When two pellets contact each other very closely (zone A), the interface is difficult to be reduced by CO and H2 due to the diffusion resistance. But in zone B, a nut coke locates between two pellets. Although the two pellets are located in the upper zone, there is still a thin metallic shell generated. It is proved that nut coke mixed with pellets improves the reduction behavior. On the other hand, it means that the reduction degree increases, compared with non-mixed charging under the same conditions.

Figure 2 Macro structure of mixing layer of pellets and

nut coke (Quenched at 1200oC)

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Figure 5 shows the softening and melting temperature of mixws charging burden for different mixing nut coke ratio. It is obvious that the softening and melting temperature increases when mixing nut coke ration changing from 0% nut coke to 20% nut coke. The SM (softening and melting) range of 0% and 20% nut coke is 320oC and 391oC, respectively. The narrower SM range means better SM behavior.

Micro structure of the partially reduced pellets

Pressure drop

Figure 3 Micro structure of the pellet (SEM-EDS, Quenched at 1100oC)

Figure 3 shows the mineralogy of two individual pellets. It can be seen that the metallic iron area of 20% nut coke is bigger than 0% nut coke. It means that the reduction degree is improved by adding 20% nut coke.

Off-gas analysis

Figure 4 shows the composition of off-gas of the quenching test. It is obvious that the CO potential of 20% nut coke is higher than 0% nut coke in the temperature range of 900oC to 1100oC. It can explain that why the reduction degree increased. This is caused by Boudouard reaction (Nut coke reacting with CO2) in the pellet layer.

Figure 6 Pressure drop as a function of temperature

From Figure 6, it can be seen that the pressure drop of 20% nut coke is lower than 0% nut coke when iron ore melting and dripping. It reveals that mixing nut coke into pellet layer can improve the permeability of the blast furnace.

CO

CO2

CONCLUSIONS • The reduction characteristics are enhanced. • The softening and melting temperature range is

narrowed. • The permeability of cohesive layer could be

improved.

REFERENCE [1] Z. Yang, J. Yang: “Effect of coke-ore mixed charging on reduction and gas flow characteristics in the softening-melting zone”, Ironmaking and Steelmaking, 22 (1995), 161-165.

Figure 4 Off-gas profile (Quenched at 1100oC) [2] M. Isobe, T. Sugiyama, and S. Inaba: “The reaction caused by the mixing of coke into ore layer in a blast furnace”, Proceeding of the sixth international iron and steel congress, Nagoya, Japan, 1990, 439-446.

Displacement of burden

[3] M. Naito, et al: “Improvement of Blast Furnace Reaction Efficiency by Temperature Control of Thermal Reserve Zone” (Nippon Steel Technical Report, No. 94. July 2006) [4] M. Gono, K. Iwatsuki, K. Nojima and T. Miwa: “The charging method of lumpy ore in blast furnace, Tetsuto- Hagané, 68 (1982), S709 [5] L. Hsieh and K. Liu; “Influence of material composition on the softening and melting properties of blast furnace materials”, Proceedings of ICSTI Steelmaking conference, Toronto, Canada; 1998, 1623-1632.

Figure 5 Displacement curve of sample bed

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Session 2: Oxygen Steelmaking

Table of Contents

2.1 Raw material flexibility secures bright future for integrated steelmaking J. KLUGE, J. SPIESS, A. FLEISCHANDERL, G. WIMMER, K. PASTUCHA (Siemens VAI Metals Technology), Austria

2.2 A study on estimation of phosphorus capacities of molten slags using a neural network approach B. DERIN, E. ALAN, O. YÜCEL (Istanbul Technical University), Turkey, M. SUZUKI, T. TANAKA (Osaka University), Japan

2.3

Metal emulsion formation in low-melting-point metal/molten salt system N. MARUOKA, D.Y. SONG, H. SHIBATA, S.Y. KITAMURA (Tohoku University), N. SASAKI, Y. OGAWA (Nippon Steel Corporation), Japan

2.4

A novel data-driven prediction model for BOF endpoint N. UEBBER, H.J. ODENTHAL, J. SCHLÜTER (SMS Siemag AG), H. BLOM, K. MORIK (Technical University of Dortmund), Germany

2.5

New approaches for efficient dedusting of basic oxygen furnaces K. MARX, S. RÖDL (VDEh-Betriebsforschunginstitut), Germany

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Raw material flexibility secures bright future for integrated

steelmaking

K. Pastucha, J. Spiess, A. Fleischanderl, G. Wimmer, J. Kluge,

(all Siemens VAI Metals Technologies, Linz)

HOT METAL PRETREATMENT

Desulphurization of hot metal

This process is standard practise in almost all integrated steel plants in the world. Nevertheless a continuously enhancement of the efficiency and productivity takes place. Depending on the region some preferences for different technologies can be found:

• EU – Co-injection lime/Mg or CaC2/Mg

• USA – Co-injection lime/Mg

• Asia – KR with lime/CaF2

Based on available information including the latest developments SVAI has done a comparison between KR and injection technology.

Flexibility in material usage (CaO, CaC2, Mg)

Material cost optimization due to variable material ratios

Production time optimization due to variable material flow rates

Less hot metal losses

Less slag amount

S-target according required steel quality

Small free board required

Injection TechnologyAdvantagesFlexibility in material usage (CaO, CaC2, Mg)

Material cost optimization due to variable material ratios

Production time optimization due to variable material flow rates

Less hot metal losses

Less slag amount

S-target according required steel quality

Small free board required

Injection TechnologyAdvantages

Maximum slag-metal phases contact

High CaO–efficiency

Cheap and available deS-agents

Simple process and short treatment time

No injection equipment (valve stand, lances)

KR–TechnologyAdvantages

Maximum slag-metal phases contact

High CaO–efficiency

Cheap and available deS-agents

Simple process and short treatment time

No injection equipment (valve stand, lances)

KR–TechnologyAdvantages

SVAI latest introduction for the desuphurization of hot metal by injection is the Simetal Feldhaus conveyor what guarantees superior accurate dosing of the magnesium.

Dephosphorization of hot metal

This technology is widely sprayed within Asia today.

There are three main reasons applying the dephosphorization of hot metal for the production of carbon steels:

• Overcoming of increasing P-input from iron ore

• Achievement of lowest final phosphorus in the LD/BOF with given phosphorus level in the available hot metal

• Absolute save and predictable BOF operation with highest productivity through direct tapping

Dephosphorized hot metal is also used during stainless steelmaking as premelt for the AOD at most of the big Chinese stainless steelmakers. By this route ferrites as well as austenitic stainless steel can be produced.

For this reason the dephosphorization of hot metal has importance for a large amount of steel produced worldwide. Therefore the advantages and short comes of the dephosphorization of hot metal in the converter or in the charging ladle are discussed.

FLEXIBLE CONVERTER

The ternary diagram shows the operation area of LD/BOF, KMS as converter technologies and EAF. The latter domain within the wide span of 100 % scrap, 100 % DRI/HBI and up to 60 % hot metal charge.

100% scrap 100% DRI/HBI

100% hot metal

EAF

KMS

LD

In the opposite the area of the conventional LD/BOF is restricted to the corner of hot metal charge. The scrap rate varies in a range of 15 – 25 %. The charge of DRI/HBI is quite uncommon yet and the experiences with this material are rather small.

Page 21: 2-page abstracts booklet

Basically, with increasing rates of scrap and DRI/HBI the material costs decline, but on the other hand the additional costs increase. Advantageously the credit of the off gas increases as well because rising coal addition generates a surplus of CO. This way increasing metallic charge and addition cost will be compensated.

The KMS process gives the possibility to flexible react on the changes on the market because it can work with a much wider range of different raw materials. The operation range of the scrap rate increases beyond 25 % till 50 % for instance.

The KMS process The magenta column shows the special case where the hot metal production keeps constant and the unused HM can be sold as pig iron. This case is a big fortune and leads to a huge cost reduction. In a similar manner the additional production of steel would increase marginal income.

The proven ability of the pneumatic injection of solids into the OBM and K-OBM converter led to the development of the KMS process (Klöckner-Maxhütte-Steelmaking). With beginning of the 1980’s there was solid coal powder injected through submerged bottom tuyeres. If the price difference of hot metal to scrap decreases

again the meltshop can return to lower scrap rates and the standard LD/BOF practise.

The KMS process can adjust the energy balance by varying the amount of coal injection to meet the economically optimum combinations of hot metal, scrap and other metallic materials respectively. This restores the flexibility of raw material selection in steelmaking.

SCRAP PREHEATING

Usually the LD/BOF process has a modest flexibility in scrap rate from 15 to approximately 25%. Beside the KMS process described above there is another way to increase scrap rate in the charge mix by increasing its physical energy through scrap preheating.

With flexible converter of KMS-type among others following plant operation scenarios are possible:

• Flexible raw material charge in a large scatter band (hot metal, scrap, DRI/HBI) depending on theirs current price and availability Scrap preheating in an external container or

vessel. The converter process itself would be less influenced by external preheating, but the handling of preheated scrap has several disadvantages.

• Maintaining steel production even if a slow down in blast furnace production occurs or some blast furnace is put out of operation

Scrap preheating directly in the vessel. For this case the energy losses are less and the handling is much easier. One option is preheating of charged scrap by burner lances from the top.

• Increasing steel production capacity without increasing hot metal production

KMS – flexible charge material mix The second option refers to the given presence of a bottom or combined blown converter. Since the tuyeres are already installed, waiting times could be used to preheat the scrap using the tuyere as burners. For this purpose natural gas or recycled converter off gas could be used as fuel like schematic shown in the diagram below.

The diagram below shows for different cases the material and production cost depending from the KMS charge mix. Case 1 represents the standard LD/BOF operation. Case 2 and 3 are KMS process using hot metal with 30 % and 40 % scrap charge respectively. The last case stands for KMS with 40 % DRI/HBI charge.

$381

$373

$365 $364

$350

$355

$360

$365

$370

$375

$380

$385

$390

$395

MET ADD OFF PI MET ADD OFF PI MET ADD OFF PI MET ADD OFF PI

Mat

eria

l and

pro

duct

ion

cost

, US$

/tst

eel

- HM - scrap = $50 per ton- HM - DRI/HBI = $75 per ton- Pig iron - HM = $50 per ton

Assumed market price difference

Cost per toncrude steel

1 3 42

In principle there is the simple calculation of the sum of charge material (green) plus the cost for further expenses (tan) like gases, energy and additions. In blue is shown the credit by the off gas. The assumptions of the price relations are on top.

The blue section indicates a lack in the thermal heat balance which must be closed by the preheating of the scrap.

Page 22: 2-page abstracts booklet

A study on estimation of

phosphorus capacities of molten slags using a neural network

approach

B. Derin1), E. Alan1), O. Yücel 1), M. Suzuki2), T. Tanaka2)

1) Metallurgical and Materials Eng. Dept.,

Istanbul Technical University, Maslak, Turkey 2) Division of Materials and Manufacturing Science, Osaka University, 2-1 Yamadaoka,

Suita, Osaka 565- 0871 Japan.

INTRODUCTION Phosphorus exists in the raw materials used in iron and steel industry such as iron ore, coke, and limestone. Due to the deleterious effect on the mechanical properties, lowering the phosphorus content in steel is of great importance during blast furnace, electrical arc furnace as well as secondary steelmaking operations. High oxygen potential, low temperature and high slag basicity are very well-known requirements for the dephosphorization during steelmaking furnace operations. In slags, phosphorus exists as phosphate (PO3-

4) or phosphide (P3-) depending on oxygen partial pressure in the furnace environment [1]. A large enough oxygen potential results in formation of phosphate in slags; whereas phosphide existence in slags occurs at lower oxygen potentials as shown in Eqs (1) and (2).

, (1)

, (2) In above reactions, dissolved oxygen [O] and phosphorus [P] in metal and oxygen ion in slag phase (O2-) react to form phosphate (PO3-

4) or phosphide (P3-) ions in the slag phase. Based on reaction (1), Wagner [2] introduced the phosphate capacity (PO3-

4) as; (3)

is activity of oxygen anion in slag phase, is

activity coefficient of phosphate ion, are partial pressures of phosphorus and oxygen.

Similarly to the phosphate capacity ( ), at lower partial oxygen pressures, phosphide capacity ( ) is calculated by reaction given by Eq (4);

(4) An artificial neural network simply means a computational model that is inspired by functions of biological neural network elements. As shown in Fig. 1, a brain cell (neuron) is composed of synapse, dendrite, soma and axon. When signal input is received from a previous neuron or an external environment, dendrites transmit it to soma. If the intensity of the signal is higher than a certain critical value, an output signal with stimulation is conveyed through axon and synapse to the next neuron or external environment.

Synapse

SomaAxon

Dentrite (a)

WeightsInputs

Summing junction

X2

X3

Xi

W2

W3

Wi

X1 W1

Sigmoid function

( )∑ −hWXf ii

Fig. 1. Schematic diagrams of a) a biological neuron and b) a simple artificial neuron The state that the intensity of signal exceeds the threshold is called “ignition” and it can be expressed in a sigmoid function shown in Eq. (5) in the neural network concept.

(5)

Here, x is an input value and y is the output, η is a coefficient which determines the shape of the sigmoid curve. In the present study, the neural network approach was applied for the estimation of phosphide and phosphate capacities ( and ) in binary and multi-component melts at different temperatures. The calculated results obtained using neural network computation was plotted against the experimental values for comparison comparative purposes. Similar

Page 23: 2-page abstracts booklet

study was carried out for sulfide capacities of slags elsewhere [3]. Phosphate capacity ( )

Yang et al. [1] has developed a thermodynamic model of phosphate capacity for CaO, MgO, FeO, Fe2O3, MnO, Al2O3 and P2O5 slags equilibrated with molten steel during a top-bottom combined blown converter steelmaking process based on the Ion and Molecule Coexistence Theory. In the present study, an artificial neural network was generated with using the experimental data and then the results compared with IMCT Model given in Fig.3.

The computation was carried out by using The Mathworks’ MATLAB R2012a Neural Network Toolbox. The experimental data that were taken from the previous studies were introduced to neural network and then results were compared with other approaches. MODELING STUDIES

Phosphide capacity ( ) Maramba and Eric [4] has recently derived a regression model for phosphide capacities of ferromanganese smelting slags at 1500 �C with using Statistical Analysis Software (SAS) system and compared the results with the experimental results. The derived model for the CO atmosphere (partial pressure of oxygen = 1.22x 10-16 atm) is shown in Eq. (6);

log =-27.539+39.130(XCaO)–31.551(XMnO)2-418.754(XAl2O3)2+19.375(XSiO2)2+65.788(XMgO)2+

180.607(XMgO.XMnO)-4.721((XCaO+XMgO)/XSiO2) (6) In the present study, an artificial neural network was generated with using the experimental data and then the results compared with regression model in Fig.2. The results are also compared with experimental values by using Root Mean Squared Error (RMSE) calculation tabulated in Table 1.

Fig. 3. Comparison between experimental and

calculated logCp values obtained by IMCT and Neural Network Models.

The results are again compared with experimental values by using Root Mean Squared Error (RMSE) calculation tabulated in Table 2. Table 2. Calculated RMSE values of models in Fig.3.

Model RMSE Value IMCT Model 0,1251

Neural Network Model 0,1019

It was shown in Table 1 that better results can be obtained with neural network approach compared to regression model. References

1) X.M. Yang, C.B. Shi, M. Zhang, J.P. Duan, J. Zhang, Metall. Trans. B, Vol.42B, 951-977. Fig. 2. Comparison between experimental and

calculated logCp values obtained by Regression and Neural Network Models.

2) C. Wagner, Metall. Trans. B, 1975, vol. 6B, pp. 405-409.

3) B. Derin, M. Suzuki, Toshihiro Tanaka ISIJ International, Vol. 50 (2010), No. 8, pp. 1059-1063.

Table 1. Calculated RMSE values of models in Fig.2.

Model RMSE Value Regression Model 0,1748

Neural Network Model 0,1332 4) B. Maramba, R.H. Eric, Minerals Engineering

21 (2008) 132-137. It was shown in Table 1 that better results can be obtained with neural network approach compared to regression model.

Page 24: 2-page abstracts booklet

Metal emulsion formation in low-melting-point metal/

molten salt system Nobuhiro Maruoka (Tohoku University)

Duk-Yong Song (Tohoku University)

Hiroyuki Shibata (Tohoku University)

Shin-ya Kitamura (Tohoku University)

Naoto Sasaki (Nippon Steel Corporation)

Yuji Ogawa (Nippon Steel Corporation)

INTRODUCTION

In the steelmaking process, it is well known that many metal droplets are dispersed in the slag phase by gas bubbling, giving a so-called metal emulsion. The metal emulsion plays an important role in increasing the reaction rate because it has a large interfacial area for the metal/slag reaction. In our previous studies, the influence of the bubbling rate on the formation of this metal emulsion was evaluated using Pb-salt1) and Al-salt2) systems, and the results showed that a local maximum amount of metal emulsion existed as a function of the bottom bubbling rate. In this study, the rate of emulsion formation in the Pb-salt system is evaluated on the basis of the mathematical model reported in a previous paper2) and compared with the results of the Al system, and an empirical equation is proposed.

EXPERIMENTAL

Figure 1 shows a schematic diagram of the experimental apparatus used to investigate the formation of the metal emulsion by bottom bubbling, the details of which are described in previous papers1-

2). 1.9 kg of Pb or 450 g of Al-5%Cu alloy and 300 g of mixed salt (KCl–LiCl–NaCl=50:42.1:7.9 mass%) were melted in a Pyrex container (60 mm I.D. × 180 mm) at 723 and 973 K for the Pb and Al systems, respectively. The heights of the metal and molten salt phases were 60 and 70 mm, respectively. After the complete melting of the metal and salt, Ar-H2 gas was introduced from the bottom center of the container.

Fig.1 Schematic diagram of experimental apparatus

After the start of bubbling, approximately 1 g of molten salt was collected from the center position of the salt phase at given intervals, for the evaluation of the formation and sedimentation rates of the metal droplets. The metal droplets were separated using a 2-μm pore filter after the dissolution of the sampled salt in water. The sizes of the droplets were measured with an optical digital microscope. The behavior of bubble detachment was observed using a high-speed camera.

RESULTS

Around 106 droplets in the Al-salt system and 104 droplets in the Pb-salt system were observed in 1 g of salt, and the size distributions of the droplets were obtained. The peak of the size distribution was 3–4 μm in both systems1-2). The total weights of the droplets in 1 g of salt were calculated by using the droplet diameters and numbers of droplets. Figure 2 shows the change in weight of metal droplets per gram of salt with time after the start of bubbling. The weights of the metal droplets increased with bubbling time, and then become more or less constant within experimental error. Therefore, 8 and 15 min are considered to be the times taken by the system to reach a steady state after the start of gas bubbling. In this state, the formation and sedimentation rates of the metal droplets are the same.

0 10 20 3010-7

10-6

10-5

10-4

10-3

10-2

10-1

Time [ min ]

Wei

ght o

f dro

plet

s [ g

/1g-

salt

]

mL/min Pb-salt Al-salt 50 100 300 500 800

Fig.2 Change in weight of metal droplets per gram of salt with time after the start of bubbling.

0 200 400 600 80010-6

10-5

10-4

10-3

10-2

10-1

Gas flow rate [NmL/min]

Wei

ght o

f dro

plet

s [ g

/1g-

salt

]

Al-salt (15min) Pb-salt ( 8 min)

Fig.3 Comparison of the weight of emulsified droplets in salt at steady state as a function of gas flow rate

Page 25: 2-page abstracts booklet

Figure 4 shows a comparison of the formation rates as a function of gas flow rate. The formation rates increased with flow rate, reached maximum values at 500 NmL/min, and then decreased in both systems. These trends are in agreement with the relations show in Fig.3.

Figure 3 shows a comparison of the weight of the emulsified droplets in salt at steady state as a function of the gas flow rate. The weights increased with gas flow rate, and had maximum values at 500 NmL/min in both systems. The weight in the Al-salt system was around 100 times higher than that in the Pb-salt system. According to the direct observation using the

high-speed camera, it is clarified that metal droplets are formed by the rupture of the metal film around the bubble. The rupture mode can be classified as one of three modes: Mode A, metal dome rupture; Mode B, metal column rupture; and Mode C, bubble column rupture1-2). In the Pb-salt system, only Modes A and B were observed. On the other hand, all modes were observed in the Al-salt system. Mode-C rupture might contribute less to droplet formation2). Figure 5 shows the relation between vf ρsalt/ρmetal and the frequencies of rupture modes A and B on the logarithmic scale. With increasing frequency, vf ρsalt/ρmetal increased, and a linear relation was observed. The relation can be expressed as follows:

DISCUSSIONS

The metal droplets are formed by gas bubbling and settle down into the bulk phase simultaneously. In the previous study2), the rates of the former and latter processes by weight are named “Formation rate, vf,” and “Sedimentation rate, vs,” respectively, and are defined as follows:

constdt

dWv Form

f == )( (1)

)(')( dim)( tWCdt

dWtv Se

s ×== (2)

( 24)(

11107.2/ BAqmetalsaltf Fv +− ××=ρρ ) (5) where W(Form) is the dimensionless weight of the metal

droplets formed by bubbling in 1 g salt (–), W(Sedim) is the dimensionless weight of the metal droplets that have settled down in the bulk phase during gas bubbling, and W(t) is the dimensionless weight at time t. C' is the sedimentation coefficient (min–1). By the method of separation of variables, the following equations are obtained as a function of time:

where Fq,A and Fq,B are the frequencies of rupture modes A and B, respectively.

0.2 0.4 0.6 0.8 1 1.2-10

-9

-8

-7

-6

-5

log Fq(A+B) [ s-1 ]

log

(vf ρ

salt /

ρm

etal

) [ s-1

]

Al-salt Pb-salt

( ) stC WetW '1)( −−= (3)

sf WCv '= (4)

where WS is the dimensionless weight of the droplets after steady state is reached (–). The application of the above equations to the experimental results for the change in weight with time during gas bubbling (as shown in Fig.2) allows C' and vf to be obtained. The fitted lines based on these relations are shown in Fig.2. The effect of the gas flow rate on C' is small under the gas bubbling condition, and the values of C' are around 0.2 and 0.1 in the Pb-salt and Al-salt systems, respectively.

Fig.5 Relation between vf ρsalt/ρmetal and frequencies of film rupture modes A and B.

CONCLUSIONS

The formation rates of metal droplets increased with the gas flow rate, and showed local maximum values at 500 NmL/min in the Pb-salt and Al-salt systems. The formation rate in the Al-salt system was about 100 times higher than that in the Pb-salt system. The formation rates of both systems can be expressed as a function of the frequencies of rupture modes A and B.

0 200 400 600 80010-7

10-6

10-5

10-4

10-3

10-2

Gas flow rate [NmL/min]

Form

atio

n ra

te [

min

-1 ]

Al-salt Pb-salt

REFERENCES

1) D.Y.Song, N.Maruoka, T.Maeyama, H.Shibata and S. Kitamura, ISIJ Int., 50, p.1539-1545 (2010)

2) D.Y.Song, N.Maruoka, H.Shibata, S.Kitamura, N.Sasaki, Y.Ogawa and M.Matsuo, ISIJ Int., 52, p.1018-1025 (2012) Fig.4 Comparison of the formation rates of droplets as

a function of gas flow rate

Page 26: 2-page abstracts booklet

A novel data-driven prediction model for BOF endpoint

N. Uebber1), H.J. Odenthal1), J. Schlüter1), H. Blom2), K. Morik2)

1) SMS Siemag AG, Germany 2) TU Dortmund University, Germany

INTRODUCTION

Modern data mining algorithms have been developed for a statistical prediction model in a cooperative effort of SMS Siemag AG, AG der Dillinger Hüttenwerke, and the Chair for Artificial Intelligence of the Technical University of Dortmund. The data-driven prediction model is obtained from the specific conditions of the BOF process. In contrast to metallurgical models, the new model makes good use of a variety of static and dynamic process and measurement variables as well as their characteristics for predicting selected target variables. In the present case, four target criteria have been defined: end-of-blowing temperature T, carbon content [%C] and phosphorous content [%P] of the melt at the end of blowing and the iron content of the slag (%Fe). The prototype of the data-driven process model was installed and successfully tested at the DH 190 t converter. The model can be adapted to other converters automatically with low effort. The expendi-ture for maintaining the model is low.

CONVERTER SYSTEM

BOF endpoint detection determines profitability and productivity to no small degree [1]. If the endpoint is not exactly achieved, time- and cost-intensive correc-tion measures will be required such as re-blowing or addition of heating/cooling agents. Moreover, this results in a reduced yield and an increased wear rate of the refractory lining. The endpoint detection relies on predicting the target data, e.g. T, [%C], [%P] and (%Fe). A good endpoint is one, where the target quantities achieve their optimal values.

The challenge posed by a prediction of the endpoint with the aid of mathematical models consists in the fact that many BOF conditions and their impact are unknown. Metallurgical models for the calculation of charge materials and their pre- and post-calculation are based on manually derived regression equations for one influencing variable each. Here, an online data mining model was developed which is based on a Support Vector Machine (SVM). The SVM is a math-ematical method to obtain regression and classi-fication functions based on process data.

The DH 190 t converter without sublance was equipped with additional measuring sensors. Apart from the existing off-gas analysis (CO, CO2, O2) and

the lance cooling system, this also comprises innova-tive wireless, 3d-acceleration sensors for the blowing lance, a sound system for acoustic monitoring and a pyrometer for detection of the converter flame, Fig. 1. The dynamic variables are detected by an IBA-PC with a sampling rate of up to 25 kHz, are processed in block-wise mode and are stored. Moreover, approx. 50 static process variables (mass of HM/scrap, HM analysis, converter age, lance age, etc.) are available from the data base system as well as singular process events, e.g. addition of heating/cooling agents.

Fig.1. Infrastructure of the measuring equipment

DATA MINING MODEL

Using the SVM requires suitable BOF characteristics to be defined as input variables. As the transient data have different sampling rates, these variables are prepared and synchronized. Possible transformations are the formation of minimum, maximum, average and fluctuation values. Based on the static and dynamic variables it is also possible to construct new features, such as, e.g., time series for additional materials which were formerly only available as mass value. Furthermore, the main blowing sequence is identified by the course of the oxygen flow rate.

Fig.2. SVM example of non-linear regression

The analysis of the data shows that no linear relation between the input data and the target values exists. Thus, a kernel function, here the radial basis function, is applied by the SVM. The SVM is trained on the basis of the measured process variables. First, a hy-per-plane is fitted to the training data. If a linear fit is impossible, the data are transferred into a higher di-mensional space. The model is a scalar product of weighted input variables in the transformed space. A

Page 27: 2-page abstracts booklet

linear function in this space corresponds to a non-linear function in the original space [2]. Outliers are taken into account. The principle SVM approach is illustrated for a non-linear regression in Fig. 2. Fitting certain mathematical expressions, e.g. the variables ξi in Fig. 2, the balance between the fit of the model to the available data (all target values are included in the regression region) and the generalization ability of the model (“narrow area”, if possible) can be attained.

IMPLEMENTATION OF THE DATA MINING MODEL

A real-time version of the data mining model, operat-ing in parallel to the L2 system, was installed in the control room. The implementation of the Java soft-ware was carried out in two steps. First, process data for several converter campaigns were gathered, the relevant input variables determined, and the model for endpoint prediction automatically acquired. Second, the model was applied online: what would the target values be like if the process ended now?

In contrast to the installed static model the target vari-ables of the new model are predicted every second on the basis of the current process conditions and moni-tored on the prototype interface in the control room, Fig. 3. For the orientation of the operator, the oxygen blowing rate and the off-gas analysis are displayed as a function over time. Apart from the instantaneous data for oxygen consumption, T, [%P], [%C] and (%Fe) predicted by the model, the measured values attained at the end-of-blowing are also shown.

Fig.3. Prototype interface of the SVM prediction mod-el, graphically showing the oxygen rate, as a table showing the predicted target variables, here, at the end-of-blowing

From both, desired target values and current predic-tions, a clear endpoint control can be defined. The differences between desired and predicted values of the target variables are converted into an optimization problem that has to be minimized. As soon as an ap-proximate optimum solution has been reached, the blowing process can be finished. Using the optimiza-tion problem, different scenarios such as the addition of heating/cooling agents can be evaluated according to their efficiency and the converter process can be

controlled. The model also determines the influence of the input variables on the respective target value by means of weighting factors.

FIRST RESULTS

Table 1 shows the standard deviation of the target values determined in off-line mode on the basis of 1400 training charges. The data are ten-fold cross-validated, i.e. successively a larger number is de-clared as training data, a smaller number as test data; the error of all test data is averaged. This statistical standard guarantees a high reliability of the results.

Target value Standard deviation UnitTemperature +/- 18.8 °C [%P] +/- 0.0041 % [%C] +/- 0.0050 % (%Fe)slag +/- 1.49 %

Tab.1. Offline results for the target variables of the BOF endpoint for 1400 successive training charges

For the BOF converter without sublance this proce-dure leads already to good results, although not all dynamic process variables have been fully operative during the first 1400 charges. Currently, additional sensors are installed at the BOF system and the se-lection of input variables for the SVM is further opti-mized. It is expected that the results will become even better as a result of these measures.

CONCLUSION

For the first time, a data-driven model on the basis of modern high-efficiency algorithms is used to predict the conditions at the BOF endpoint. The accuracy in predicting the temperature and other target variables is not only equal but even better than using metallur-gical models. The prediction model operates in a sta-ble and reliable manner, enhances the understanding of the process by exposing process relations between input and target variables, and thus supports the met-allurgical model. In the next development stage, a multi-objective control tool will be developed that cor-rects the running BOF process in real-time, so that the target values are optimized.

ACKNOWLEDGEMENT

The authors gratefully acknowledge the AG der Dillin-ger Hüttenwerke for the excellent cooperation within the scope of this project.

REFERENCES

[1] Chukwulebe, B. O., Robertson, K., Grattan, J.: The methods, aims and practices (MAP) for BOF endpoint control, Iron & Steel Technology (2007), p. 60-70 [2] Smola, A.J.; Schölkopf, B.: A tutorial on support vector regression, Statistics and Computing (2004), p.199-222

Page 28: 2-page abstracts booklet

New approaches for efficient dedusting of basic oxygen

furnaces

K. Marx, S. Rödl (VDEh-Betriebsforschungsinstitut Düsseldorf)

STATE OF THE ART

Secondary off-gas cleaning systems are normally installed to evacuate the hot fumes produced during the converter operation steps scrap charging, hot metal charging, steel tapping and slag dump. Environmental issues are requiring efficient dedusting systems, but the capital costs as well as the operation cost for dedusting systems in steel industry are high, so that an optimum design with regard to an eco-nomical operation is very important.

Installing auxiliary hoods requires special adaptation of the design and precise positioning. Objective criteria to choose the optimum hood design are missing. Large amounts of energy are wasted, if hood geometry and the fume evacuation volume do not fit properly to the different operating conditions.

Suppression of the emissions at the source normally requires less expenditures than a complete fume capture with hoods. The basic idea is to eliminate contact of the liquid metal and atmospheric oxygen. Developing systems for supplying inert gas to the metal jet and meniscus, so as to eliminate such contact, is complicated by the high temperature and the great quantity of mobile equipment. There is a lack of experience, especially for the use of this technique during BOF charging.

Studies were performed to compare and optimize different types of suction hoods (with and without swirl) and to develop effective techniques for fume and flame suppression.

DOCUMENTATION OF THE PRESENT PRACTICE

In order to document the conditions at the converter video photographs were taken from different views. Plume photography has proven an effective method of estimating buoyant plume volumes for hot emissions sources. BFI uses advanced image analysis software called Structural PIV for the quantification of fume flow rates. This methodology differs in several points from the classical PIV (Particle Image Velocimetry) tech-nique. Instead of using a laser for creating a light sheet, white light or even day light is sufficient. The second difference is the seeding method used. PIV is

working with tracer particles. Structural PIV on the other hand works with small structures for example in smoke clouds. The analysis of images of smoke clouds is done by ensemble correlation averaging, which makes it possible to receive a mean flow field with a sufficient high signal-to–noise ratio. The advantages of Structural PIV are that it can be used on full-scale objects in the plant, less safety precautions are necessary and the equipment is cheaper.

COMPARISON OF DIFFERENT HOOD TYPES

Several hood types for the secondary off-gas system were studied. The ratio of suction flow rate through the charging hood Vhood to fume flow rate Vfume for complete fume capture was used to judge the fume capture efficiency of the hood variants. For the old hood the ratio Vhood/Vfume had to be increased to 14.0 to achieve complete fume capture for scrap charging. With the optimized hood the fume can be captured completely with a ratio of Vhood/Vfume of 7.4. If the scrap chute is covered, the flow ratio Vhood/Vfume can be further reduced to 3.6.

The process phase “hot metal charging” was calculated for the old hood with the planned flow rate of at least 750 000 m³/h (S.T.P.) through the charging hood. The flow velocities are very high in the vortex type hood because the swirl in the hood produces an additional circumferential velocity component in the hood. This leads to a high pressure loss.

In spite of the high velocity values in the hood, complete fume capture is not achieved. So this hood geometry could not be recommended for the planned flow rates. Efficient charging hoods for small available space and techniques for fume suppression were developed and installed in 2011

The performance of the hoods verified the results of the numerical simulation. The new hoods allow nearly complete fume capture during all process phases.

From preliminary results can be estimated that the new secondary dedusting system captures about 720 t of dust per year. Before the installation of the new secondary dedusting system occasionally brown smoke was visible above the steelplant. These pollutions can now be avoided nearly completely.

The workers confirmed that the dust concentration in the aisle was reduced by the optimised dedusting system. The intervals for cleaning the converter plat-form were extended. So it is expected, that measure-ments of dust concentration in the working environ-ment will show a significant improvement of the working conditions.

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FUME SUPPRESSION

It can be assumed that a considerable amount of oxygen is in the converter vessel before hot metal charging. Therefore field trials were performed to flood the vessel with inert gas. In the time between slag dump and blowing 850 m³/h (S.T.P.) of argon were injected through the bottom tuyeres of the converter vessel. The time of injection lasted between six and eleven minutes. Reactions during scrap charging were suppressed. The duration of the hot metal charging could be reduced by about 30% in the cases with pre-inertization. Since fume and flames were suppressed by the injection of inert gas the crane operator was able to tilt the hot metal ladle faster. In one case the ladle could be emptied in only 40 s. No security risks like slopping or ignition of unburnt gases occurred during the trials with pre-inertization.

Fume suppression with injection of CO2 during hot metal charging was tested in further trials. Liquid CO2 was stored in an insulated pressurized tank (20 bar, -20°C) on a road tanker. Lances (snow tubes) were constructed and built, in which the liquid CO2 was expanded through a nozzle and a jet of gas and CO2-crystals (snow) was discharged into the converter vessel. The CO2-snow sublimates to CO2-gas, when it is heated up.

Outside the dog house a scaffold was put up on the 10 m-level. A lance was inserted through a hole in the dog house wall and was moved with a special developed manipulator. The road tanker was placed in a save place between the converters on 0 m-level.

Normally brown smoke is produced during hot metal charging. During injection of CO2 with a lance in the flames a white fog was rising and the flames were brighter.

During this trial 900 kg of CO2 were injected. It can be expected that a better fume and flame suppression can be achieved for small and medium sized con-verters.

CONCLUSIONS

Measurements, observations and operational trials in the plant, physical model trials and calculations with a computational fluid dynamics programme were performed to give the necessary basic information for planned and existing secondary dedusting systems. It can be concluded that model trials and numerical simulation are important powerful tools for the optimization of dedusting systems. Possible optimizing measures can be evaluated already in the planning stage and the results can be transferred to the plant with good success. With these tools BFI developed effective solutions to optimize dedusting systems for a great number of BOF shops.

Efficient charging hoods for small available space were developed and optimized by physical model trials and numerical simulation. The simulation tools are adequate to study and compare different types of suction hoods. The boundary conditions for the simulation can be gained by video documentation (plume photography and image analysis with Structural PIV) as well as measurements in the plant. The results are transferable to a great number of other BOF shops. A flare during scrap charging can be suppressed by a cover on the scrap chute. The method for fume suppression during hot metal charging with inert gases is expensive but probably applicable especially for small or medium sized converters with weak exhaust systems. The new secondary dedusting system is independent from the primary system. The hoods, which were constructed based on the findings of the project, have a very good performance.

The knowledge gained can be used within the steel industry to provide cost-effective emissions reductions on the majority of BOF shops, where similar problems are encountered.

ACKNOWLEDGEMENT

The work for the study was carried out with a financial grant from the Research Fund for Coal and Steel of the European Union (RFCS Contract Number RFSP-CT-2007-00045). The authors want to thank the staff of both steel plants for the good collaboration and allowance as well as the Research Fund for Coal and Steel for the financial support.

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Session 3: Electric arc furnace

Table of Contents

3.1 Plant measurement and numerical simulation of EAF operational data P.V. GRYGOROV, M. LÜTTENBERG, H.J. ODENTHAL, M. REIFFERSCHEID, F. THEOBALD, N. VOGL (SMS Siemag AG), Germany

3.2 Spectrometer-based real time measurement of the electric arc radiation in a DC-EAF V. HAVERKAMP, K. KRÜGER (Helmut Schmidt University), B. DETTMER, H. SCHLIEPHAKE (Georgsmarienhütte GmbH), Germany

3.3

The holistic approach for efficient scrap melting M. DORNDORF, M. ABEL, M. HEIN (Siemens VAI Metals Technologies GmbH), Germany, H. AFLENZER, M. TRATNIG (Siemens VAI Metals Technologies GmbH), Austria, D. VAILLANCOURT (Siemens Industry), USA

3.4

LINDARC™ Real time EAF off-gas analysis system M. MEDEOT, M. IACUZZI (MORE s.r.l.), Italy

3.5

Industrial application of chemical energy for special steel grades and processes L. HACQUARD, A. GROSSE, K. LIBERA (Badische Stahl Engineering), A. OPFERMANN (Badische Stahlwerke), Germany, R. ERIKSSON (Ovako), Sweden

3.6

Efficient energy recovery from electric arc furnace offgas F. ZAUNER, G. ENICKL, A. FLEISCHANDERL (Siemens VAI Metals Technologies GmbH), T. STEINPARZER, M. HAIDER (Technical University of Vienna), Austria

3.7

Improvement of Cr yield in the EAF by use of briquetted Al containing filings G. STUBBE, G. HARP (VDEh-Betriebsforschung Institut), K. VAMVAKAS (BGH Edelstahl Siegen), Germany

3.8

Direct reduced iron production from EAF slags in fixed bed furnace I. BILEN (KTH Royal Institute of Technology), Sweden, A. TURAN, O. YUCEL (Istanbul Technical University), Turkey, P. JÖNSSON (KTH Royal Institute of Technology), Sweden

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Plant measurement and numerical simulation of EAF operational data

P.V. Grygorov, M. Lüttenberg, H.J. Odenthal, M. Reifferscheid,

F. Theobald, N. Vogl

SMS Siemag AG, Germany

INTRODUCTION

The electric arc furnace is a complex system combin-ing electrical, mechanical and hydraulic components. In this work the results of online measurements of EAF parameters as well as numerical simulations of the EAF process in Matlab/Simulink and Computa-tional Fluid Dynamics (CFD) are presented.

PLANT MEASUREMENTS

The process data recorded on a 150 MVA AC 135 t EAF comprise three groups of signals. The electrical signals, e.g., the secondary currents and phase voltages were recorded with 20 kHz sampling rate, thus a non-sinusoidal waveform of currents and voltages can be investigated in details. The second group involves the accelerations of electrode arms, measured on the outer and central arms close to the electrode holders. By using the state of the art accelerometers for 3D measurements and wireless data transmission, a sampling rate of 500 Hz was achieved. This rate provides a high resolution for all vibration modes of electrode arms and allows a detailed analysis of the measured oscillations in time and frequency domain (Figure 1). Thus the eigenfrequencies of the electrode supporting arm can be precisely measured. The third group, recorded at 1 Hz, comprises the rms values of the currents, voltages, electric power, power factor, pressure in hydraulic cylinders and other signals used to control the EAF melting process. In the following these signals are used to validate a mathematical model of the EAF.

MATHEMATICAL MODEL OF EAF

In parallel with the plant measurements a mathemati-cal model of the EAF was implemented in Matlab/ Simulink (Figure 2). The input parameters of the mod-el are the secondary transformer voltages. The equiv-alent electric circuit is described by the system of dif-ferential equations that can be found elsewhere [1].

Fig.1: Measured oscillation spectrum in frequency domain

The electric arc is described as an impedance load, whose resistance is modelled by the phenomenologi-cal ansatz by Remus [2]. The movement of the sec-ondary system of the EAF (vertical mast, electrode supporting arm and graphite electrode) are described by a set of equations of motion, where the measured values of the damping coefficient, eigenfrequency and the net force acting on the secondary system are used. A special attention in the model is paid to the hydraulic system, which consists of hydraulic cylin-ders, pressure tank, pumps and the control valves. The last element, the electrode control, is described by proportional (P-) controllers, which operate the control valves. The objective of the controller is to maintain the current difference as close to zero as possible.

Fig.2: Schematic representation of the EAF model

The developed EAF model was used to simulate the EAF process. In Figure 3 the simulated operational data during the scrap boredown are shown. These are the position of electrodes, power factor, electric pow-er, valve opening, hydraulic pressure and the horizon-tal acceleration of the electrode supporting arm. The power factor cos φ = 0.75 and the total power of about 95 MW are reached after 8 s of dynamical simulation, whereas the measured parameters are 0.7 and 105 MW, respectively. Since the geometry and material properties of the secondary system in the model have been adjusted to those of the real EAF, the simulated total pressure in hydraulic cylinders reproduces ex-actly the measured value of 75 bar. The simulated horizontal accelerations of electrode arms reach 3 m/s2 in amplitude. After the experimental validation the EAF model was used for simulation of mechanical resonances in the secondary system. This allows developing a damping strategy by changing mechani-cal and electrical furnace parameters.

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Fig. 4. CFD simulation of a 250 t AC HDRI-EAF

Fig. 3. Simulated process data: position of electrode, power factor, electric power, valve opening, hydrau-lic pressure, horizontal acceleration of electrode 1.

CFD SIMULATION Figure 4 shows the result of an incompressible, tran-

sient, multi-phase, and non-isothermal CFD simulation for a 250-ton AC HDRI-EAF (HDRI - Hot Direct Re-duced Iron) with three Injectors (SIS1-3) and three carbon injectors (C1-3). The arrangement of additional lance manipulators in the slag door or EBT (Eccentric Bottom Tapping) area is possible. A special feature here is the addition of HDRI through the fifth EAF hole. According to the furnace operating practice, approx. 600°C hot briquetted HDRI (∅ ≈ 6 - 20 mm, ρ = 2100 kg/m3) is charged into the hot area between the electrodes. The SIS injectors are designed for

= 3300 m3/hstp and p0 = 10 bar taking into account the metallurgical process inside the furnace.

0V&

In the CFD model the electrodes touch the melt sur-face. The wall temperature rises to 2500°C towards the tip of the electrode. The influence of the foamy slag is taken into account by a slag layer. Figure 4 shows the oxygen jets and the velocity distribution in the melt; the slag phase is hidden. The jets of the SIS units and carbon injectors can be rec-ognized as light green iso-volume that includes the velocity range between 6 and 100 m/s. The SIS jets induce a transient movement of the melt surface (yel-low). The penetration depth of the impinging jets var-ies between 0.25 m and 0.41 m. Compared with theo-retical values by Koria and Lange [4] CFD predicts slightly higher results. Among others, the CFD simula-tion yields statements on the wall shear stress which, together with the melt temperature and dynamic pressure ρ/2⋅u2, are used to predict the local refractory wear.

The oxygen is homogeneously distributed in the fur-nace and the decarburization reaction [C] + ½ {O2} → {CO} is accelerated by the intensive motion of the melt. In addition, carbon is injected into the slag via the carbon injectors, with air used as conveying gas. The intention is to produce a foamy slag that contains CO gas bubbles in order to enable long arcs and to protect the panels against radiation.

SMS Siemag uses a combined strategy of plant test and numerical simulation to continuously improve the design and the operating conditions of the EAF.

REFERENCES The CFD simulation for the EAF is based on the URANS (Unsteady RANS) equations with the k-ω-SST-SAS model of Menter et al. [3].

[1] Bowman, B.; Krüger, K.: Arc Furnace Physics, Stahleisen GmbH (2009), p.246

For the multi-phase flow of melt, slag, and gas the VoF (Volume of Fluid) model is use. The DPM (Dis-crete Phase Model) is used to add HDRI and/or coal particles to the computational domain. The DPM model performs Lagrangian trajectory calculations for the dispersed phases, i. e. particles, droplets or bub-bles, including coupling with the continuous phase. The carbon particles (∅ ≈ 1 to 3 mm, ρ = 600 kg/m3) are injected at a maximum of Ma = 1 in the form of a Rosin-Rammler distribution from the carbon injectors.

[2] Remus, B.: Analyse elektromechanischer Bean-spruchung von Elektroden in Lichtbogenöfen, PhD Thesis, Univ. Hamburg-Harburg (1984), p. 98

[3] Menter, F.R.; Egorov, Y.: Turbulence modeling of aerodynamic flows, Intern. Aerospace CFD Conf., Paris (F), 18.-19.06.2007, p. 1

[4] Koria, S.C.; Lange, W.: Penetrability of impinging gas jets molten steel bath, steel research 58 (1987) 9, p. 42

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Spectrometer-Based Real-Time Measurement

of the Electric Arc Radiation in a DC-EAF

V. Haverkamp (Helmut-Schmidt-University Hamburg Germany)

K. Krüger (Helmut-Schmidt-University Hamburg Germany)

B. Dettmer (Georgsmarienhütte Steel Plant Germany)

INTRODUCTION AND AIM

The electric arc is the main energy carrier into the EAF, transferring about 100 MW of electric power into the steel charge in the form of radiation and convection. At the beginning of the melting process, solid scrap shields the arc. Later on, foamy slag is built up in order to cover the arc and thereby prevent radiation from directly hitting the water-cooled furnace wall panels and refractory. However, the scrap or slag level may vary extensively and thus leave portions of the arc temporarily uncovered. This generally undesirable condition causes unnecessary heat losses and undue furnace wear. Therefore, it needs to be counteracted upon promptly, for example by reducing the arc voltage and thus the arc length and maybe by increasing the slag level by means of coal or oxygen injection. A number of methods for the detection of the uncovered arc already exist, including measurements of acoustic emissions, electrical variables or the cooling panels’ temperatures. Although these methods render a counter-action possible, a time delay is inherent in each of them. This is due to the fact that none of the said methods is based on a direct observation of the arc radiation itself but rather on measuring an effect it causes in another variable. This paper presents the development and measurement results of a spectrometer-based sensor being mounted on the 130 MVA DC-EAF of the Georgsmarienhütte GmbH. The advantage of this sensor is the possibility to directly measure and evaluate the radiation spectrum of the electric arc in

real-time, facilitating a very fast reaction to free-burning arc conditions. Consequently, heat and energy losses can be decreased while the service life of the furnace vessel and refractory is increased. Additionally, the spectrometer-based approach opens up further possibilities in EAF process optimisation, e. g. real-time determination of the steel-bath temperature or elements analysis.

MEASUREMENT SETUP

Instrumentation at the Furnace

The main challenge in taking direct measurements of the electric arc radiation with a spectrometer arises from the extreme environmental conditions present inside or in close proximity of the furnace. Especially dust, electromagnetic fields, mechanical vibration and high temperatures considerably stress the equipment. In this project, a water-cooled box is integrated in one of the cooling panels lining the interior furnace wall. This box has two small openings pointing at the furnace centre at slightly different angles, allowing two commercially available CCD-based spectrometers with different bandwidths a direct view either onto the steel bath surface or at the electric arc. The sight holes are continuously flushed with nitrogen in order to keep them clear of splashing slag and other possible obstructions during the melting process. For the studies underlying this paper, only one spectrometer is installed as shown in figure 1.

Fig. 1: Measurement Setup at the Furnace

Data Transmission and Recording

The spectrometer data is transmitted from the furnace to a control room via a standard USB extension set, which also supplies the spectrometer with electric power. This set-up is depicted in figure 2.

Fig. 2: Spectrometer Electrical and Data Link-Up

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The advantage of this solution is that the data recording and processing device, an embedded PC, does not need to be exposed to the said extreme conditions at the furnace. Furthermore, the future integration of the spectrometer data into the process control system of the furnace is facilitated. However, the data is fed through a network cable over a distance of about 100 m through the furnace shop, raising the possibility of electromagnetic interference or mechanical stress disturbing the signal.

RESULTS

First, the described set-up is used to record a sample of 427 melts during a period of four weeks.

Long-Term Stability of the Set-Up

Figure 3 shows the mean value of the measured arc radiation intensity for each melt, averaged over the entire spectrometer bandwidth, ranging from 195 to 1127 nm.

Fig. 3: Long-Term Mean Spectral Intensity

Neglecting the indicated downtimes and interruptions, it can be observed that the spectrometer data is consistently greater than zero and assumes varying values. This allows the conclusion that the chosen equipment installation is generally capable of continuously collecting well-suited measurements for further use directed at the above mentioned aims. Moreover, this result verifies the sufficiency of the installed nitrogen flushing at keeping the sight hole clear over a period long enough to sustain spectrometer operation between the standard furnace maintenance intervals. However, there is considerable fluctuation in the intensity curve and even a slightly declining tendency is noticeable. Both may be due to the stochastic nature of the melting process and to the fact that free-burning arc conditions, causing high intensity values, do not occur in every melt.

Informative Value of the Spectrometer Data

Comparing the mean measured arc radiation intensity Ispect, mean with the furnace electric power Pel, the mean cooling panels’ temperature TPanels and the wall

thermal power yields the curves shown in figure 4 for an exemplary melt.

Fig. 4: Mean Spectral Intensity and Further Process

Data During an Exemplary Melt

The spectrometer intensity curve rises steeply at 13:52 and at 14:07. Both incidents are followed by an increase in temperature and thermal power about 60 to 120 s later. Similar results are observed in numerous other melts, which strongly suggests the following conclusions. Firstly, a free-burning arc condition is present in each of these cases and secondly, the spectrometer data is generally suitable for the detection of this condition.

CONCLUSION AND OUTLOOK

Aiming at raising the thermal efficiency of a DC-EAF, it is shown in this paper that a measurement set-up built up of commercially available components integrated into a water-cooled box at the furnace is generally qualified for detecting free-burning arc conditions. The gain in time compared to established detection methods is about 60 to 120 s. Next steps will include the examination of possible correlations between radiation intensity values at different wavelengths and free-burning arc conditions as well as slight alterations of the viewing angle of the spectrometer. Thus, detection accuracy will be further improved. The subsequent connection of the spectrometer measurement system with the melting process control system will thus allow precise counteractions to be taken, which will ultimately help reduce thermal power loss and furnace wear. Due to its operating principle, the presented spectrometer-based approach furthermore holds potential for on-line melt temperature and composition analysis.

ACKNOWLEDGEMENT

The authors greatly appreciate the funding of the research project by the German Ministry of Education and Research.

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The holistic approach for efficient scrap melting

Dr.-Ing. Markus Dorndorf, Head of R&D Electric Steelmaking, Siemens VAI Metals Technologies

GmbH Dipl.-Ing. (FH) Markus Abel, Senior Expert Electric Steelmaking, Siemens VAI Metals Technologies

GmbH Dipl.-Ing. Helmuth Aflenzer, Process Automation Steelmaking, Siemens VAI Metals Technologies

GmbH & Co B.Sc.- Ing. Denis Vaillancourt, Process Metallurgist,

Siemens Industry, Inc. Dr.-Ing. Mark Tratnig, Project Manager Lomas,

Siemens VAI Metals Technologies GmbH & Co

Michel Hein, Head of Metallurgy & Process Technology, Siemens VAI Metals Technologies

GmbH

Keywords: Holistic approach, electric steelmaking, off-gas measurement, Lomas gas analysis, closed loop control, SAM, holistic process model, Heatopt

THE CHALLENGE Today most existing solutions only deal with specific sub-systems of electric arc furnaces. Controls are separately performed for burners, electric arc power, post-combustion and carbon management. These controls are time or energy related; an integrated, closed-loop solution for all energy and material flows has been implemented only partly. This low level of automation and the restriction on specific elements lead to a suboptimal use of resources like electric power and chemical additives. The Electric Arc Furnace is mainly managed by the experience of the operating staff. Therefore it is difficult to comply with a constant efficiency. For a continuous and cost-efficient operation of an electric arc furnace the following requirements for a new closed-loop control can be defined:

• Holistic approach for all furnace sub-systems and components

• Modular composition of the system allowing specific furnace configurations

• Application of modern sensors and measurement technology to get a high level of transparency, especially using off-gas composition, flow analysis and slag level measurement.

• Immediate feedback by closed-loop control of all material flows

Figure 1: Electric arc furnace – the initial part for efficient and sustainable steel making OUR SOLUTION Our solution is to use of information from the Lomas - Low maintenance gas analyzing system - that gives the composition of the furnace off-gas consisting of oxygen, hydrogen, carbon monoxide and carbon dioxide and natural gas. Further, the output of the SAM (Single Air Measurement) off-gas flow measurement and the FOX300 slag level indication are used for an advanced holistic process model. The model itself comprises of algorithms and prediction strategies for closed loop control of injection of natural gas, oxygen, carbon as well as the electrical power input. Main difference of the holistic control to most existing systems is the closed loop reaction corresponding to the actual process conditions respectively the actual furnace behaviour. This represents a significant progress compared to the usual, rigid time and energy related control diagrams. Main features of Heatopt are a minimized and efficient process-related use of natural gas, oxygen and carbon, based on proper adjustments of main operating parameters. Further, the saving of energy input (electric and / or fossil) based on process conditions and the reduction of the tap-to-tap time as well as a higher level of transparency of the process. GENERAL SYSTEM ARRANGEMENT The general system arrangement and function is visible in the electrics & automation hardware layout (Figure 2). A communication network between measurement systems (Lomas, SAM, FOX300), the Heatopt control unit and the customer PLC is realized via Profibus and Ethernet. Based on the fact that all measurement systems are integrated in a Siemens PLC, an easy implementation in the existing furnace periphery is given. Combined with the furnace conditions and status information of the customer’s

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The system further contains a self-checking, logic which automatically induces different switching/cleaning steps if different gas analysis and gas treatment parameters (e.g. gas flow, temperature, …) reaches critical values.

PLC, all detailed process information for the holistic process model with the included algorithms - for modification of set values for oxygen, carbon and natural gas - are available.

Extremely short response time (t90) of far less than 15 sec. (depending on site conditions) and continuous, high-available and accurate measurement of CO, CO2, H2, O2 and CH4 make this probe leading in EAF operation. Routine checks are required only twice a month and maintenance work will not exceed eight hours for two times a year. A further benefit of this system is its fast warning procedure for dangerous situations i.e. high contents of CO and H2 during melting and refining process as well as CO/ H2 detection for protection of the plant’s dedusting system.

Figure 2: General system arrangement for flexible and fast installation in existing furnace periphery

For an accurate and easy to implement slag foaming monitoring system, the FOX300 solution made by Siemens VAI is included. The system uses Rogowski coils to analyze the high current harmonics to measure and calculate a slag foaming index.

MEASUREMENT TECHNOLOGIES The Lomas system with its patented gas sampling probe represents a sophisticated low maintenance gas analyzing system, performing with highest availability and providing safety and explosion protection. The probe has proven its reliability and sustainability in numerous installations of more than 140 BOF primary off-gas ducts worldwide. For the EAF application the probe was further improved and adapted, especially with focus on abrasion protection, cooling and thermo-mechanical stress like thermal expansion.

The Heatopt-system was successfully implemented and tested in cooperation with Steel Dynamics Inc., Roanoke (USA) for an 100t electric arc furnace with 65 minutes tap-to tap time and 3 injector units each for carbon, oxygen and fine coal. Customer Benefit The closed loop control of the Heatopt system combines all measurements of the tools mentioned above to calculate a holistic process model of the current heat. These data are used for controlling the furnace inputs like energy, oxygen, natural gas, and carbon.

By continuously monitoring the EAF off-gas and off gas flow rate and by processing the measured values with the holistic process model the operational benefits could have been improved by the tests in SDI. The main difference of the holistic control to most existing systems is the ability to react corresponding to the actual process conditions respectively the actual furnace behaviour. This represents a significant progress compared to the usual, rigid time and energy related control diagrams and in consequence, the process is individually managed and optimized.

Figure 3: Lomas probe retrofit in the off-gas duct The probe is located in the off-gas duct (figure 3) and is purged automatically. The Lomas system offers high accuracy in measurement and data evaluation and could demonstrate an availability of more than 99%, even under extremely hot (up to 1.800 °C) and dust-laden (up to 2.000 g/Nm3) gas conditions.

This system was successfully implemented and tested in cooperation with Steel Dynamics Inc., Roanoke (USA) and the overall targets were achieved and exceeded.

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LINDARCTM

Real time EAF off-gas analysis system

M. Medeot (MORE s.r.l - Italy)

INTRODUCTION

In today’s competitive market, it is of utmost importance for EAF steel makers to perfect their processes in order to reduce operating costs and improve the safety and reliability of their equipment. The innovative off-gas analysis technology, with laser units installed on the fixed duct, just after the combustion gap, uses the technique of “Tuneable Diode Laser Absorption Spectroscopy” (TDLAS). It performs real-time off-gas emissions measurements of CO, O2, H2O and temperature of off-gas. A closed-loop operation is in place for dynamic control of the chemical energy package and dedicated post-combustors to perform CO, H2 and CH4 combustion into the EAF furnace shell. The system has, so far, proven its reliability, resulting in a maintenance free operation, and the optimization of carbonaceous fuels combustion with subsequent electric energy, oxygen and natural gas reduction. This paper describes off-gas analysis technology TDLAS laser technology, the laser on-site installations, the post-combustion injectors, the closed-loop-control strategy and future developments of the system.

TUNABLE DIODE LASER SPECTROSCOPY – THEORY AND BACKGROUND

The laser emits a monochromatic light which contains one specific wavelength of light with a very narrow frequency band. Every molecule has a special frequency of absorption (single absorption line). If the light source emits the same frequency, the molecules will start moving and absorbing the emitted energy; energy absorption leads to a reduced signal on the receiver. The amount of energy absorbed is based on the Beer Lambert Law and depends upon the number of molecules between the transmitter-receiver and the measurement path length.

The off-gas analysis system uses the technique of “Tuneable Diode Laser Absorption Spectroscopy - TDLAS”. This single-line absorption spectroscopy measuring technique is based on the selection of one single absorption line (in the near infrared spectral range) for the specific gas to analyse (fig.1). The spectral width of the diode laser is considerably narrower than the one of the absorption line for the chosen gas. By varying the diode laser current, its wavelength is scanned across the absorption line. The light detected in the receiver unit varies due to

the absorption of light from the specific gas molecules in the optical path between the diode laser and receiver. The detected shape and size of this single absorption line is used to calculate the amount of gas in the measurement path.

Fig. 1: Tuneable Diode Laser Absorption Spectroscopy

Absorption lines from other gases are not present at this specific wavelength, and therefore will not interfere with the single absorption line or the resulting gas concentration. Dust only weakens the light without interfering with the measurement if a minimum quantity of emitted light is reaching the receiver.

Currently, laser base off-gas analysis technology is reading the following species:

Carbon Monoxide (CO) 0÷100%

Oxygen (O2) 0÷25%

Water (H2O) 0÷100%

Off-gas temperature 0÷1600°C

EQUIPMENT INSTALLATION AND RESULTS

Laser off-gas analysis technology is installed directly after the combustion gap, on the fixed water cooled duct, to analyse the off-gas which is drawn off from the 4

th hole (Fig. 2). To have a correct analysis of the

conditions inside the furnace (avoiding false readings caused by the false air entering the gap) only the centre of the off-gas stream is analysed. To do so, two water cooled lances protruding inside the off-gas duct to “shield” the laser light and expose the off-gas, only along a well-defined measuring path length. The location of these lances is established by Computational Fluid Dynamics (CFD) analysis. Lances are water cooled and kept clean by nitrogen purging cycles, which do not interfere with the measurement.

The main advantages of the TDLAS technology compared to conventional measurement techniques are:

Measurement of the real off-gases volume (no sampling and gas conditioning is needed);

Fast response time (less than 2 seconds compared to more than 20 seconds of the extractive method);

Direct H20 content measurement (not possible with conventional extractive method);

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Maintenance free (no movable parts, no gas conditioning systems or filters to be maintained).

.

Fig. 2: equipment scheme

The automation system includes a LINDARC Control Computer (LCC) with specially designed HMI and Closed Loop Control (CLC) and Dynamic Water Leak Detection (DLWD) software. EAF and off-gas measurement data are stored into a SQL server and a powerful database is used for the analysis of historical process data, which can be either performed locally or on remote computers via Internet or Intranet connections.

Fig. 3: off-gas analysis technology automation scheme.

Since November 2009, two systems have been in operation with successful results (fig. 4) together with MORE chemical injection system.

Fig. 4: on-site installation

The following table describes the average results achieved, compared with the performances before the off-gas analysis technology installation.

average results

Electrical Energy consumption -5,0%

Oxygen consumption -10%

Natural Gas consumption -6,0%

Injected carbon consumption - 10%

Table 1: Average results

Moreover, additional benefits are: reduced skulls (un-melted scrap) on the furnace walls, with consequent better scrap charging and a better knowledge of the furnace melting process.

By adopting the laser off-gas analysis, savings of 2 USD/t have been generated thanks to the precise control of all melting phases and the reduction of the overall transformation costs.

CONCLUSIONS

The laser off-gas analysis technology has proven to be a highly precise and extremely fast tool to obtain exact data for the various gas species in the EAF off-gas system. It improves carbonaceous fuel combustion with subsequent electric energy, oxygen and natural gas reduction.

From the safety point of view, the system enables the monitoring of real-time water content in the off-gas to prevent explosions generated by water leaks. Moreover, real-time signal of CO value in the off-gas will prevent explosions in the dust settling chamber or bag house and it is possible to set-up gap/dumper positions.

The system has proven its reliability resulting in a maintenance free operation due to the application of design and manufacturing details base on more than 25 years of experience in the steelmaking industry by MORE engineers.

The following benefits can be expected by adopting the off-gas analysis technology:

Reduction of Power On time

Reduction of electrical energy consumption

Optimization of oxygen, fuel and carbon consumption

Increased productivity and yield

Increased meltshop safety

REFERENCES

S. Marcuzzi, D. Tolazzi, S. Beorchia – “LINDARCTM

EAF off-gas analysis system – Installation at Gerdau Ameristeel Jacksonville, AisTech 2011, 2-5 May 2011, Indianapolis, U.S.A.

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Industrial application of chemical

energy for special steel grades and processes.

L. Hacquard (Badische Stahl Engineering, Kehl, Germany)

Oxy-fuel burners are nowadays almost standard equipment on Electric Arc Furnaces all over the world. The implementation of those burners began more than 30 years ago. The main reason for oxy-fuel burner installations is supporting scrap melting at the cold spots common to UHP operation.

Today most burners are operated as multi-function tools, i.e. they operate as burners as well as oxygen lancing tools. The application of those multi-function tools is mainly in carbon steel production as it enables the utilisation of high oxygen levels together with carbon injection. This has lead to a boost in productivity together with a reduction in electrical energy.

However, the application of multi-function side wall tools has not yet been introduced much on EAF’s which produce special steel grades or stainless steels.

This paper describes operational results together with fundamentals for the application of chemical energy at a stainless steel producer and a special steel producer.

In addition an example will be given from a shaft furnace. An optimised chemical energy usage has shown an improved productivity together with lower consumption figures.

For the stainless steel makers, a P-ON-time reduction by 10.6% was achieved and a reduction of electrical energy consumption by 6% at no losses of yield was achieved.

For the Special steel maker Ovako, a P-ON-time reduction by 13,5% was achieved and a reduction of electrical energy consumption by 13,3% was achieved.

For the optimisation on the shaft furnace process, the productivity increased by 1,84% and a reduction of electrical energy consumption by 4,43% with a reduced fuel consumption of 28,70% was achieved.

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Efficient energy recovery from electric arc furnace offgas

Florian Zauner, Gerhard Enickl, Aalexander

Fleischanderl (all Siemens VAI)

Thomas Steinparzer, Markus Haider (all Technical University of Vienna)

1. INTRODUCTION

For decades operators of electric steelmaking plants have been well aware of the vast amount of thermal energy contained in the hot offgases from electric arc furnaces (EAFs). Various attempts have been made to capture this source of energy, but the widely varying offgas flow and temperature caused them to abandon their efforts in the past. Due to steadily increasing costs for electricity future-oriented meltshop owners are revisiting this topic now. Local environmental restrictions regarding greenhouse-gas (GHG) emissions make these solutions even more attractive. The improved overall process efficiency helps to cut GHG emissions hence saves costs for CO2 certificates.

2. TODAYS SITUATION AND POTENTIALS FOR OFFGAS ENERGY RECOVERY

Electric arc furnace based steelmaking represents about 1/3 of Europe’s steel production. Regarding the charged materials (e.g. scrap, hot metal, DRI, HBI) and the produced steel grades EAFs are quiet flexible and will continue to increase their share in steel production. Error! Reference source not found. shows the energy balance (Sankey diagram) for a typical scrap operated EAF. The offgas related losses amount for almost 31% of the whole energy inputs. It is obvious that an efficient heat recovery system from the hot offgas would contribute enormously to improve the energy balance of the process.

Figure 1: Specific energy balance per ton of liquid steel tapped for a typical electric arc furnace.

3. TAILOR MADE HEAT RECOVERY STEAM GENERATORS (HRSGs) FOR THE STEEL INDUSTRY

The steam generator must be able to cope with the highest inlet temperature and offgas flow. If it would be designed too small in terms of heat exchange area troubles with the maximum filter inlet temperature might occur. On the other hand side a boiler with far too much heat exchange area than necessary would influence the payback period badly. For this task a proprietary boiler design tool was developed. All relevant types of heat exchangers and their combination within a HRSG can be designed with its help. The results of the tool showed good match with commercially available software packages.

Depending on the intended offgas temperature at the outlet of the steam boiler it has to substitutes the whole cooling system comprising water cooled duct, quenching tower or forced draft cooler and the air cooled connecting duct. Other than these cooling devices the steam generator behind the EAF uses also heat exchanger surfaces (tube bundles) perpendicular to the flow direction of the offgas. This leads to improved efficiency of heat transfer and a compact design of the boiler. However sometimes there is not enough space available to situate the HRSG directly next to the furnace which calls for a horizontal duct between the drop out box for the coarse dust settlement and the vertical steam generator outside of the meltshop. The offgas at the drop out box outlet is still relatively hot. To achieve a maximized steam output of the energy recovery system the horizontal duct has to be designed as an evaporator which could cause troubles with stratification of the water/steam mixture and or plugging of single pipes [1]. A unique design for this heat exchanger section was developed which ensures a uniform flow distribution from the headers to each pipe and also sufficient gas cooling and steam production at all modes of operation of the furnace.

The vertical steam generator behind outside the meltshop consists of a water-cooled membrane wall in tube-bar-tube construction. As mentioned above the

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steam boiler can be put right on top of the drop out box if there is enough space available (Figure 2). The first section of the vertical boiler is an empty pass. Due to the high offgas temperature under maximum load the heat transfer is dominated by radiation. With decreasing offgas temperatures the amount of heat exchanger surface perpendicular to the offgas flow direction in the steam generator increases. The heat transfer by convection begins to govern the energy exchange gradually. The cross-current bundle heat exchangers in the offgas flow make use of this phenomenon and help to keep the HRSG as compact as possible.

Figure 2: 3D-Layout of a HRSG for a 150 ton DRI-based EAF situated right on top of the drop out box.

A waste heat recovery steam generator designed like described above is able to turn a certain portion of the cooling water into steam. Nevertheless the steam mass flow leaving the steam drum on top of the boiler shows the same unsteady behaviour like the offgas enthalpy flow but in a blurred way. Since almost all downstream consumers call for a constant supply of steam a buffer storage has to be part of the energy recovery system.

4. ELECTRIC POWER GENERATION FROM SATURATED STEAM

The system uses a turbine running on saturated steam to drive a generator for electric power generation. Ruths buffer storages are used to level the steam production of the HRSG to provide the turbine with a constant steam mass flow at e.g. 50 bar(a). The steam boiler works at e.g. 80 bar(a) whereas the Ruths accumulators float between 80 and 50 bar(a).

Figure 3: Process flow diagram: Electric power generation from saturated steam [2]

The simulations resulted in a constant power output of about 7,7 MWel (Basis: 150 t tapping weight, scrap charged, tap-to-tap time 43 min).

5. ADVANCED SOLUTIONS FOR POWER GENERATION USING THERMAL ENERGY STORAGE

The steam turbine could produce even more power if it runs on superheated steam. Since the thermal power of the offgas is quiet unsteady during the process one could not maintain the necessary energy for steam superheating at all times. Hence some energy storage has to be foreseen in case that no extra chemical energy should be wasted. Sophisticated solutions using molten salts for thermal energy storage are currently under investigation (Figure 3).

Figure 3: On site demonstrator plant using molten salt for thermal energy storage.

REFERENCES

[1] VDI-Gesellschaft Verfahrenstechnik und Chemieingenieurwesen (Hrsg.), VDI Heat Atlas Second Edition (2010), p.841-844

[2] M. Haider et al., Technical Report: Dampferzeugung hinter Elektroöfen (unpublished), Technical University of Vienna - Institute for Energy Systems and Thermodynamics (2010)

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Improvement of Cr yield in the EAF by use of briquetted Al containing

filings

G. Stubbe (VDEh-Betriebsforschungsinstitut GmbH, Germany)

G. Harp (VDEh-Betriebsforschungsinstitut GmbH, Germany)

K. Vamvakas (BGH Edelstahl Siegen GmbH, Germany)

INTRODUCTION

BGH operates a 40 t EBT-EAF with a transformer power of 35 MVA at Siegen works (Figure 1). The furnace is equipped with several side wall injectors/burners used for solid material injection. The total liquid steel production of BGH is around 130000 t/a, including a large range of speciality steel and stainless steel products.

Figure 1 EAF with lifted electrodes - BGH in

Siegen

For improvement of the chromium yield in the EAF during stainless steel making, the use of briquetted metal residuals from light metal machining as reductant has been investigated combined with the use of granulated aluminium injection. The aim of the investigations is to substitute the more costly injected granulated aluminium by the cheaper Al-Mg briquettes in order to achieve a chromium oxide content in the EAF slag below 2 wt.-%. Another important aspect is the stabilisation of the remaining chromium oxide within non-leachable compounds (spinel minerals), turning the slag into an environmentally safe material.

OPERATIONAL TRIALS – USE OF AL-MG BRIQUETTES

Established slag treatment procedure at BGH Siegen

At BGH Siegen, during stainless steelmaking granulated Al injection is performed for slag treatment and chromium reduction. For that a solid material injector is used. The amount of the injected Al during stainless steel making is < 10 kg per tonne of liquid steel.

Procedure of operational trials

For the operational trials, secondary Al-Mg briquettes are used made of turnings and filings from the light metal machining industry. The briquettes are of cylindrical shape (diameter: 100 mm, height: around 100 mm) with a density of around 1.9 kg/dm³ (Figure 2).

Figure 2 Photo of an Al-Mg briquette

The Al-Mg briquettes contain 27 wt.-% Mg, 41 wt.-% Al and 22 wt.-% Fe. Based on stoichiometry of the chromium reduction reactions, the Al equivalent content of the briquettes has been calculated to 61 %. Therefore 1.6 kg of the Al-Mg briquettes are needed for substitution of 1 kg pure Al.

The operational trials concerning the balanced use of Al-Mg briquettes and injected Al have been performed during more than 20 EAF heats. The Al-Mg briquettes have been charged to the EAF by the last scrap basket. Aim of the trials is to substitute the costly injected Al by low cost Al-Mg briquettes.

The amount of the Al-Mg briquettes has been varied in the range of 4 – 18 kg/t of liquid steel, while the amount of the injected aluminium was varied in the range of 0 – 8 kg/t of liquid steel.

For each EAF heat, data from the operational system (e.g. input amounts; electric energy consumption) have been analysed, chemical analyses of the final slag have been performed and the EAF heat- and dust output by the exhaust gas, has been measured.

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Results

The target chromium oxide percentage of < 2 wt.-% in the EAF slag was only achieved within the range of 11-17 kg Al-Mg briquettes per tonne of liquid steel, indicating that the optimum amount is within this range. In this case, the amount of the injected Al has to be adjusted within the range of 2.4 – 3.5 kg/t of liquid steel.

The dust discharge via exhaust gas increases with the amount of added Al-Mg briquettes. The average measured dust discharge for an optimum amount of around >14 kg/t of Al-Mg briquettes is in the range of 10-13 kg/t of liquid steel. The increasing dust discharge indicates that a significant part of the added Al-Mg briquettes are simply burnt off during the scrap melting phase. This prevents chromium oxidation because in the EAF the oxygen is consumed by oxidising the Al-Mg briquettes.

The heat loss via the exhaust gas increases slightly from around 60 to 80 kWh/t of liquid steel with increasing amount of added Al-Mg briquettes in the range of 5 to 18 kg/t of liquid steel. This behaviour again is an indication that compared to normal operational procedure a larger part of the added Al-Mg briquettes are oxidised during the scrap melting phase, releasing more heat energy to the exhaust gas.

The chromium elution behaviour of the solid slag is an important aspect for later usage of the EAF product slag for building applications or for dumping of the slag. For estimation of the chromium elution of a solid slag, the “Factor SP” has been defined by FEhS, which is calculated from the chemical composition of the slag. For the optimum addition of > 14 kg Al-Mg briquettes per tonne of liquid steel, the Factor SP is mostly above 25, which means that the CrVI+ elution is below the environmental limitation. This result proves that by addition of Al-Mg briquettes an EAF product slag is produced, which fulfils the strict CrVI+ elution limits.

CONCLUSIONS

The use of Al-Mg briquettes at the EAF during stainless steelmaking has clearly demonstrated its ability to recover chromium from the liquid slag leading to chromium oxide content in the slag below 2 wt.-%. The improvement of the chromium yield is explained by the prevention of chromium oxidation during the scrap melting phase on the one hand as well as the reduction of chromium oxide within the formed slag on the other hand.

The optimal amount of the reductants for the new procedure is > 14 kg/t of Al-Mg briquettes and 2.4-3.5 kg/t injected aluminium. With this procedure, a chromium oxide content of lower than 1 wt.-% was achieved. The resulting solid slag product has extremely low Cr elution below the environmental

threshold value, which is the prerequisite for a use as building material.

In total, cost savings are gained by application of the new operational procedure using the Al-Mg briquettes. Up to 20 % of the consumption costs for injected Al and charged FeCr may be saved. The charging of the Al-Mg briquettes can easily be applied by charging of a big-bag with the briquettes to the last scrap basket.

In contrast to solely injection of granulated Al (normal operational procedure) the efficiency of the chromium reduction in the slag is lower, because a significant part of the Al-Mg briquettes oxidise during the scrap melting at the EAF atmosphere. This behaviour is reflected by the increasing dust discharge and heat loss by the EAF exhaust gas.

Improved chromium reduction efficiency is expected by direct charging of the Al-Mg briquettes during the flat bath period to the liquid slag via the 4th hole of the EAF. Therefore the shape and size of Al-Mg briquettes has to be adapted to the requirements of the EAF alloying system, with which the briquettes are weighed and charged. In order to make the briquettes float at the surface of liquid metal and slag an increased density (> 3 kg/dm³) is necessary which is achievable by raising metallic iron content in the briquettes.

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INTRODUCTION

Previously, the most common process in iron and steel production was blast furnace in the integrated steel plants but complexity of the blast furnace process caused to become widespread of EAF and alternative production technologies in the latest growth of iron and steel industry. Investment and production cost advantage of EAF, leads to the growth of EAF usage rather than blast furnace[1]. In addition, lower negative environmental effect and possibility to produce in smaller amount make EAF more preferable. EAF slag consists of metallic oxides mainly as CaO, FeO, SiO2, MgO, Al2O3 and MnO as well as oxides of other metallic additives such as Cr, Ti etc. including in scrap.

According to result of survey performed by The European Association Representing Metallurgical Slag Producers and Processors (EUROSLAG) in 2010, 8.5 million tons of EAF slag is produced in Europe[2]. Although slag is an inert waste, slag is still stocked without any precautions against environmental effects. Therefore, it has a crucial importance to focus on recycling of slag.

High percentage of EAF slag is re-used in road construction as aggregate[2]. However it can be re-cycled in the internal use for metallurgical processes as well. In order to re-use EAF slag in the process as a raw material, direct reduction is a new approach. ��� ���������� direct reduction conditions of 39% Fe2O3 containing EAF slag were investigated in a tube furnace. Direct reduction is reduction of iron containing raw materials with gas or solid reductants without melting of charge. For the direct reduction process of iron generally process is limited at 1200°C since melting may be observed over this temperature before liquidus temperature of Iron due to pressure of the experiment chamber[3].

EXPERIMENTAL STUDY

The experiments were performed by using EAF slag as raw material and metallurgical coke as reducing agent according to its easiness to use and low ash and volatile content. EAF slag, used in the experiments, consists of 39% Fe2O3. Materials were

milled in order to achieve powder form. Milled slag was mixed to get homogenous batch and pelletized to reduce the surface area for protection from oxidation after the furnace stage. Chemical analysis of slag and metallurgical coke are given in Table 1.

Table1. Chemical Analysis of EAF Slag and Coke

Slag Analysis

FeMet% Fe2O3% CaO% SiO2% Al2O3%

0.84 39.26 25.45 16.81 7.53

MgO% Na2O% ZnO% K2O% S% C%

5.79 0.18 0.13 0.04 0.57 1.28

Experiments were based on three variables; coke stoichiometry, temperature and duration. 150 and 200% coke stoichiometrically calculated by using Cfix, added for each charge. 1050, 1100 and 1150°C were defined as the temperature steps by taken into consideration the direct reduction temperature limits. Five slag pellets and coke powder charged to fixed bed type tube furnace in a graphite boat for each trial. 5, 10, 15, 30, 60, 90 and 120 minute duration steps were applied for each temperature and stoichiometry combination. After each charge, graphite boat was cooled to 700-500°C in the furnace and then air-cooled. Each charge that is taken from furnace experiment, weighed and saved for further calculations. 3 of 5 pellets were milled for chemical and XRD analysis and 1 pellet was cut into 2 pieces for optical analysis.

RESULTS

Optical Analysis Results

In figure 3 the 20X magnification micrographs, which illustrate the change in metallic iron content in the samples with respect to increasing experiment duration. As the sample set, 1150°C and 200% stoichiometrically added coke trials were chosen since the highest metallization were obtained.

Figure3. 20X magnification micrographs of 1150°C and 200% stoichiometrically added coke trials

Coke Analysis

Cfix% Ash% Volatile% Humidity%

87.78% 8.83% 3.39% 3.07%

5mins 10mins 15mins 30mins

60mins 90mins 120mins

Direct Reduced Iron Production from EAF Slags in Fixed Bed

Furnace

Idil Bilen*, Ahmet Turan**, Pär Jönsson*, Onuralp Yücel**

*Royal Institute of Technology, Sweden **Istanbul Technical University, Turkey

Page 45: 2-page abstracts booklet

Chemical Analysis Results

Metallization was calculated by the chemical analysis results as given in the Figure 1 and 2.

Figure1. Metallization of 200% stoichiometry and at different temperatures

Figure2. Metallization of 150% stoichiometry and at different temperatures

In Figure 3 metallic iron, FeO and Fe2O3 ratio of the best resulted trial set which is 1150°C and 200% stoichiometrically added coke.

Figure3. Fe, Fe2O3 and FeO Ratio at 1150°C and 200% stoichiometry

XRD Analysis Results

Figure 4 demonstrates the XRD analysis result of 1150°C and 200% stoichiometrically added coke trials with respect to time. Metallic iron phase formation change can be observed by the metallic iron peak change in the graph.

Figure4. XRD result of 1150°C and 200% stoichiometrically added coke trials

CONCLUSION

Results indicate that increased temperature, process duration and stoichiometry have a positive impact on direct reduction of EAF slag in terms of iron metallization. 90% metallization degree has been achieved as the result of the study with the process conditions of 200% stoichiometry and 90 minutes process duration at 1150 °C. After 90 minute trials, it was observed that reduction efficiency start to decrease since the carbon in the environment became insufficient as indicated in the Graph 1 and 2 as well as XRD analysis result. Micrographs of the 200% stoichiometry at 1150°C experiment set, show the distribution of iron in the pellets and reduction efficiency which increases by increasing process duration.

REFERENCES

1. Anameric, B., 2007. Pig Iron Nugget Process. PhD Thesis, Michigan Technological University.

2. EUROSLAG, The European Association Representing Metallurgical Slag Producers and Processors, 2010

3. Zervas, T., McMullan, J. T. and Williams, B. C., 1996. Developments in Iron and Steel Making, International Journal of Energy Research, 20, 69-91.

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Session 4: Flat product hot rolling

Table of Contents

4.1 New Hot strip mill of Colakoglu Metalurji - Design, project execution and operational results O. ÖZSOY, H. BULUT (Çolakoglu Metalurji), Turkey, H. HÖFER, H. HARTMANN, K. HOEN (SMS Siemag AG), Germany

4.2 Standardization concept for the main drives of the hot rolling mills of ArcelorMittal in Europe C. DELCOURT, H. JUNGFER, F. KIEFER, M. SARRAZYN (Siemens Belgium), Belgium

4.3

Development and application of a new virtual mill-stand analysis software tool K. MAYRHOFER (Siemens VAI Metals Technologies GmbH), S. HUBINGER, K. SHERIF (Austrian Center of Competence in Mechatronics, Linz), R. GRUBER, L. PICHLER (Siemens VAI Metals Technologies GmbH), Austria

4.4

A transducer for normal pressure, friction stress and contact length measurements in hot and cold flat rolling of metals A. NILSSON (Mefos), N.G. JONSSON (Jernkontoret), J. LAGERGREN (Åkers), Sweden, T. LUKS (Brno University of Technology), Czech Republic

4.5

Oil free lubrication in steel hot and cold strip rolling T. REICHARDT, H. DELI (VDEh-Betriebsforschung), S. MYSLOWICKI, C. MÜLLER, M. RAULF (ThyssenKrupp Steel Europe AG), M. HERRMANN (Chemische Werke Kluthe GmbH), P. DAHMS (Bilstein GmbH & Co KG), C. MÖMMING (Hydro Aluminium Deutschland GmbH), Germany

4.6

Study of tribological oxide layer behaviour during the hot rolling of ferritic stainless steels É. LUC (Aperam), M. DUBAR, A. DUBOIS (Laboratoire TEMPO, Université de Valenciennes et du Hainaut Cambrésis), A. HERMANT, A. DESSIS, J.M. DAMASSE (Aperam), L. DUBAR (Laboratoire TEMPO, Université de Valenciennes et du Hainaut Cambrésis), France

4.7

Development of the prediction model for hot strip flatness after coil cooling M. MIYAKE, Y. KIMURA, T. KAWAI, T. HIRUTA (JFE Steel Corporation), Japan

4.8

Hot rolled coil cooling and availability system G. PAULUSSEN, A. KOORN, P. SEIJTS, H. HOOGLAND, L. STORTELDER (Tata Steel), The Netherlands

4.9 Striving for ultra high-strength and direct-quenched hot band. Modernization of SSAB's hot strip mill M. THURGREN, R. HÖGBERG, E. JOHANSSON, P. SIXTENSSON (SSAB), Sweden, K. ECKELSBACH, H. METZ, M. WAGENER (SMS Siemag AG), Germany

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NEW HOT STRIP MILL OF COLAKOGLU METALURJI -

DESIGN, PROJECT EXECUTION AND OPERATIONAL RESULTS

O. Özsoy, H. Bulut (Çolakoğlu Metalurji, Gebze, Turkey)

H. Höfer, H. Hartmann, K. Hoen (SMS Siemag AG, Hilchenbach, Germany)

INTRODUCTION

The hot strip mill of Çolakoğlu Metalurji, situated on the outskirts of the Turkish metropolis of Istanbul, is the most up-to-date rolling mill in Turkey with a capacity of 3 million tons per year. With its commissioning in June 2010, Çolakoğlu Metalurji extended its portfolio from long products to high-quality hot strip.

The commissioning of the hot strip mill was characterized by a steep start-up and good strip quality right from the start.

ÇOLAKOGLU METALURJI

Çolakoğlu Metalurji is a Turkish family-run business which involvement in the iron and steel business began with the steel trade in 1945. In 1960, the first Çolakoğlu rolling mill was comissioned in Sütlüce, Istanbul. The first meltshop went into production in Dilovası in 1969 to supply billets to the domestic market. The company now called Çolakoğlu Metalurji strengthened its sectoral leadership when it started wire rod production in 1985. In 1990, Çolakoğlu added reinforcing bars to its production line. In 2007, Çolakoğlu Metalurji decided to extend its portfolio to flat products by investing in a new meltshop and a hot strip mill.

PLANT LAYOUT

The location of the new hot strip mill is in Gebze, directly on the Sea of Marmara, where Çolakoğlu Metalurji previously operated a long products rolling mill. To prepare the site for the new plants, extensive civil works had to be carried out.

To accommodate the new hot strip mill on these premises, it is designed as a compact hot strip mill. Main components are a 4-high reversing roughing stand with edger, a mandrel-less coilbox, a 7-stand finishing mill, the laminar cooling system, two downcoilers and the pallet-type conveyor system. The total length of the mill is only 330 meter. The rolling mill is designed as a stilting unit, in order to avoid

ground water problems that may arise due to the nearby sea. This also has the advantage of the supply systems, e.g. for hydraulic oil and pressure water, to be accessible from the floor level.

Fig. 1: Plant layout of the hot strip mill of Çolakoğlu Metalurji.

The entire hot strip mill operates with the electrical and automation package by SMS Siemag including the drive system, level 1- and level 2-systems, technological measuring systems, instrumentation, sensors and the HMI.

Capacity 3.0 million t/year

Steel grades Carbon steels, HSLA grades, tube and pipe grades, DP and TRIP steels

Slab thickness 180 – 250 mm

Strip thickness 1.2 – 25.4 mm

Strip width 800 – 1,650 mm

Table 1: Main technical data

TECHNICAL HIGHLIGHTS

To avoid transfer-bar camber as a result of thickness and temperature deviations in the slab, “camber-free rolling” was implemented in the roughing stand. It is based on the interaction of the roll alignment control (RAC) and the heavy position-controlled side guards in the exit and entry section of the mill. The side guards actively counteract the formation of strip camber. RAC keeps the roll gap in the roughing stand perfectly parallel also in case of slabs with temperature or thickness wedge, thus forcing a mass flow transverse to the rolling direction to arise in the transfer bar.

The mandrel-less coilbox serves to coil the transfer bar after the last pass and to then uncoil it during finishing rolling. This significantly reduces the distance between roughing and finishing mill. Also temperature equalization in the transfer bar takes place in the coilbox. The strip enters the finishing mill at almost constant temperature, thus allowing a particularly stable rolling process.

In the finishing mill, strip profile, flatness and contour are set by the CVC® plus system in combination with work roll shifting. Hydraulic loopers between all stands safeguard a stable strip travel. The roll gap lubrication in stands F2-F6 reduces friction in the roll gap and thus the roll force.

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The two hydraulic downcoilers feature Automatic Step Control preventing marks on the inner windings of the coil and protecting the coiler’s mechanical equipment. The coils are transferred with horizontal coil eye by pallet-type conveyor system to the coil yard.

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The technological process models – pass schedule calculation (PSC), profile and flatness control (PCFC®) and the cooling section control (CSC) – are based on mathematical-physical models which provide the settings for the various mechanical actuators of the mill under consideration of the material properties. Fig. 3: Thickness deviation (n = 5,725) The automation system of the hot strip mill was tested and optimized by SMS Siemag before delivery using the Plug & Work method.

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OPERATIONAL RESULTS

The hot strip mill of Çolakoğlu Metalurji started production in June 2010, two weeks earlier as scheduled. Already in the second month after commissioning, the hot strip mill attained about a third of its nominal production. Considering the Turkish steel industry's modest business in 2010, Çolakoğlu Metalurji did not expand its production proportionately during the subsequent weeks. The mill demonstrated its full potential just four months after commissioning, when the rated capacity was exceeded in several production shifts.

Fig. 4: Crown deviation (n = 5,725)

Already seven weeks after the start of production, Çolakoğlu Metalurji rolled strip with the aimed-at minimum final thickness of 1.2 mm. In this rolling operation, too, the gauge, width and final rolling temperature over the whole length of the strip were within a narrow tolerance window. The coiling profile of the strip demonstrates the high quality of the downcoilers. Around four months after commissioning, Çolakoğlu Metalurji reduced the final strip gauge even further, producing 1.1 mm thick strip. Despite the large thin-strip volume produced, the amount of strip scrap during this month was just 0.3%.

Fig. 2: Start-up curve.

Concerning strip quality, already after three weeks, 99% of all measured values were within the agreed tolerances for strip thickness, width, profile and flatness.

Fig. 5: Measured data of the first strip with a gauge of 1.2 mm

Figures 3 and 4 show the thickness and profile deviation during a start-up period.

CONCLUSION AND OUTLOOK The new hot strip mill of Çolakoğlu Metalurji in Turkey started production in June 2010 and achieved good operational results right from commissioning. Due to the supply of the complete plant technology by SMS Siemag, all systems were already fine tuned and matched very well already during commissioning.

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Standardization concept for modernization of main drives of the hot rolling mills of ArcelorMittal in

Europe

C. Delcourt, H. Jungfer, F. Kiefer, M. Sarrazyn Siemens is to replace existing DC main drives in the finishing mills of the hot rolling mills with more powerful AC systems in the ArcelorMittal plants in Dunkirk, France, and Ghent, Belgium. The two projects are part of comprehensive modernization plans for boosting productivity and reducing costs, within the scope of which the two hot rolling mills are also to be modernized for the processing of steel grades that demand more sophisticated production technology.

Finishing mill in the ArcelorMittal plant in Ghent, Belgium. The integrated production sites of ArcelorMittal Atlantique in Dunkirk, and ArcelorMittal in Ghent, belong to the Flat Carbon Europe Division. The Dunkirk site has an annual capacity of 4.5 million tons of hot strip. An important customer for the end products is the automobile industry. Siemens will modernize the drives of seven finishing stands over four stages. Initial commissioning on one of the mill stands is planned for December 2012. ArcelorMittal Ghent has a wide hot-strip mill and produces around five million tons of flat steel a year for applications in the automobile industry and domestic appliance industries, for example. In Ghent, a total of six finishing stands will be modernized in three stages, the first in December 2012 within a shutdown time of only twelve days.

Standardization of motors for different operation requirements Siemens will supply the motors, converters and transformers for all 13 mill stands, and will handle on-site activities like installation and/or erection

supervision, commissioning and customer training. The focus of the project is the standardization of the drive system across different plant locations. The challenge is to supply a single motor which covers the requirements of all stands of both production sites. Detailed analyses of the current and future production schedules of the plants as regards motor power, torque and speed facilitate the choice of an optimized motor. These points determine the size of the motor in terms of electrical operation data but do not take into account the limitation of the mechanical dimensions and the available shutdown times. These are quite different between the plants. The plants were built at different times and have a different technology and modernization history. Therefore adapting the existing structural environment presents a special challenge. In Dunkirk, each stand has three DC machines coupled on one shaft, while in Ghent the stands are equipped with one or two DC motors in series. Furthermore over the years one of the plants received an additional stand which was already equipped with AC technology. This has resulted in completely different motor pit dimensions. Additionally, the motor design has to cater for different axis heights. The decisive limiting mechanical parameters are the minimum axis height and the minimum motor pit dimensions. Siemens had to design a single AC motor with a higher total power but outer dimensions which allows the motor to fit on the same foundation as a single DC machine. Modifications of the foundation had to be minimized to realize the required short shutdown times. Main drive motors are usually designed as 6 up to 24 pole machines. Siemens optimized the motor design especially for the modernization application. Only thanks to the non-salient design of the Siemens rotors is it possible to dimension the motors in 6 to 12 pole design to meet the requirements of a hot strip mill application. The 12 pole motor in particular offers the benefit of outer dimensions close to a DC machine and additionally savings in weight due to smaller lamination packages. This flexibility of the Siemens motor design makes it especially suitable for modernizations. For the chosen 12 pole version, the outer dimensions fit on all motor pits and the special design of the motor feet allows the installation of the motors on multiple base frames with different bore masks. This also facilitates the use of just one spare motor for all stands, to minimize fixed assets and required shutdown times. The usual design of Siemens motors in this power range features pedestal bearing design. This brings with it the advantages of an optimized force flow into the foundation and minimized weight of the motor. An alternative solution is the compact design of the machines. For this design, the base frame and housing of the motor has to absorb the high forces. This requires a very solid and rigid design of the motor frame and housing. Consequently, it is significantly

Page 50: 2-page abstracts booklet

heavier. The advantage of the compact machines is the installation and also the replacement can be performed in a very short shutdown time with less effort.

Motor in compact design

Limitations of standardization – Customized standardization Besides the standardization aspect, and a very short shutdown time, the main target of ArcelorMittal is to produce a new product mix of higher strength steels. Different product mixes at both sites finally led to the decision to install two kinds of motors with different power. The use of a single motor would have had the highest degree of standardization but would have meant an overdimension and non cost-optimized solution for one site. The final choice is a 12 MW compact machine for the Dunkirk site and a 14 MW pedestal bearing machine for the Ghent site to meet their higher requirements regarding achievable rolling torques. Despite the longer shutdown times usually required for pedestal bearing machines, Siemens as the full service supplier developed a concept to keep the shutdown for the replacement of 2 drive trains within 12 days. The motor requirements showed the challenging character of the standardization over different plants or even different stands within one single plant. But the standardization concept does not stop with the motor but also sets demanding challenges to the converter technology.

Highest flexibility for converter systems The electrical requirements for the converter system mainly result from the necessary motor power and torque, which are different for the two sites. The Siemens SINAMICS SM150 voltage source converters are based on IGCT technology. The optimized pulse pattern (ROTOS) minimizes the switching losses and results in an efficiency of up to 99%. Through the installation of capacitor cubicles for the converters at the Ghent site, the output current can additionally be increased. These properties together with the high overload capability allow both required power ranges to be achieved by the identical

SINAMICS SM150 medium voltage source converter based on 5.0kA IGCT technology without overdimensioning it for one of the sites. Thereby the converter system has been perfectly optimized to the site-specific motor requirements. New installation locations outside the former electrical room result in long cable runs between the converter and the motor or transformer and converter. This creates an increased cable capacity which causes higher peak voltages and therefore higher stress for the stator insulation system. Only special filter systems can reduce the stress and deliver the flexibility for the location of installation. Not only the location but also the available space has been a significant parameter. Only being able to realize cabling from top and/or bottom and the opportunity to install the converter in one row or separated in single power units offers sufficient flexibility to the special conditions of each plant.

Highly flexible SINAMICS SM150 converter system

Cooperation of customer and supplier

Open-mindedness on the part of the customer and the willingness of the supplier to act as a consultant and also be open and flexible to the ideas of the customer results in an optimized revamp concept with a maximum degree of standardization but still customized to the operator requirements. This shows that standardization might be limited but that it is not incompatible with customization.

As a single source full service supplier, Siemens is able to cover all the different modernization requirements thanks to its long experience and professional knowledge in the field of engineering, commissioning, installation, supervision, service, after-sales service and project execution. The close cooperation with the customer from the very beginning results in an optimized modernization solution and a high level of customer satisfaction.

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Development and application of a new virtual mill-stand analysis

software tool

K. Mayrhofer (Siemens VAI GmbH Linz)

S. Hubinger (ACCM GmbH Linz)

K. Sherif (ACCM GmbH Linz)

R. Gruber (Siemens VAI GmbH Linz)

L. Pichler (Siemens VAI GmbH Linz)

INTRODUCTION

Hot and cold rolling processes aim at delivering metal strips within low dimensional tolerances. Mill dynamics have a major impact on the output product. Achievement of the strip dimensional requirements thus demands careful analysis of the dynamic behaviour of new mill designs.

MOTIVATION

Most mills are unique (Fig.1) and representative test rigs or trial systems are lacking. Numerical simulation is hence the most suitable instrument for system analysis and design optimization.

Fig.1: 4-hi Mill Stand and Drive Train Assembly

The dynamic behavior during practical operation strongly depends on the specific rolling pass parameters (e.g. gauge draft, strip speed and strip tensions), which cause time dependent rolling loads (forces and torques). These loads may excite the eigenmodes of the coupled mill stand and drive train system. It is thus desirable to predict the mill and drive train dynamics by use of a fast and precise numerical simulation tool with adequate graphical features.

GOAL

The goal is the development of a new PC based offline mill-stand simulation tool, with C++ model coding and integration in the powerful MATLAB/SIMULINK architecture. Application of this

tool to sheet rolling mills (single reversing or tandem mills) is foreseen.

THEORY

It is postulated that real rolling mill assemblies follow the governing differential equation of motion (1).

( )txxFxNKxGDxΜ ,,)]([)]([ &&&& =Ω++Ω++ (1)

The used symbols represent the physical properties: mass matrix M, damping matrix D, gyroscopic matrix G, stiffness matrix K, non-conservative force-matrix N and non-linear excitation force F caused during strip rolling operation. The vector x represents the generalized coordinates which contains the suitable chosen degrees of freedom (DOF) for proper motion description. The natural frequencies and the associated modal shapes of the analysed system depend directly upon these matrices.

MODEL ISSUES

Equation (1) is a powerful instrument to assess the relative importance of various parameters. This allows focus on the dominant terms and parts.

Note that the gyroscopic (G) and non-conservative force (N) matrices may not be linear in order to account for the non-linear behaviour of given mill components. In particular non-linear sub-models have been developed for the MORGOIL fluid bearings, roll contacts, hydraulic cylinders, rolls, spindles, shafts, roller bearings as well as for the gear-mesh stiffness variation during torque transmission. Furthermore, a specific roll-gap model has been developed which can cope with the three-dimensional load transfer between rolling force, rolling torque and strip tensions.

Use of DOF-reduced matrices of substructures based finite elements (FE) models, which are beneficial for modeling of arbitrary shaped components, e.g. gear-box housing, is emphasized.

SIMULATION CHALLENGE

The main challenge in the field of dynamic simulation is the achievement of accurate results together with fast computational and short analysis times. Note that taking gyroscopic effects into account requires three-dimensional models which make FE simulations very time consuming. This justifies the choice of a semi-analytical model with C++ implementation.

ROTORDYNAMIC CONTINUUM ROLL MODEL

During sheet rolling several unsteady speed phases exist, e.g. the head-in and tail-out phase. During these phases the rolls deform due to the spin effect (gyroscopic rotors) with major impact on the roll-gap geometry.

For a correct and fast simulation of such effects a new semi-analytical continuum model has been developed and coded in C++. This model allows the processing of various cross sections and is also applicable in the

Page 52: 2-page abstracts booklet

case of non-spinning parts, e.g. mill stand housings or other beam-like components of the mill.

ROTORDYNAMIC BENCHMARK TEST

The benchmark test of the continuum roll model is focused on the run-up simulation of a slender shaft with disks on both ends and supported by two roller bearings (Fig.2).

Fig.2: Benchmark test rig

The spinning part is accelerated from rest to full speed via constant torque loading through the run-up period. In order to boost the gyroscopic effects an initial impact load on the greater disk introduces bending vibrations of the shaft. The problem was analyzed by means of the C++ continuum model and the FE program ABAQUS.

The transient FE results converge smoothly against the C++ solution. And of major importance, the FE calculation time is about some hours compared to a few seconds with the new simulation tool. This promising preliminary result opens way for simulation of a complete rolling mill.

TANDEM COLD MILL (TCM) SIMULATION

Creation of a proper TCM model is summarized as follows:

a) Execution of a series of modal impact tests during erection and commissioning of a TCM.

b) Establishment of the 3D FE model of the TCM (Fig.3).

Fig.3: Tandem Cold Mill (TCM): 3D FE Model

c) Update of the FE model in some steps. Due to the lack of some model parameters (e.g. masses, local stiffnesses, damping effects) the FE model has to be

d) Transfer of the tuned FE model into the C++ simulation program by

tuned so that its dynamic response matches the measured values.

creation of the related input file.

ted for ialization and control of the mill model

By this way the mill assembly has been successfully created (see e.g. Fig.1 for the 1st TCM stand).

SIMULATION

Suitable control features have been implementhe dynamic initaccording to the pass preset values. Fig.4 shows a speed variation during a typical run-up and run-down period. The corresponding strip thickness variation after stands G1 and G2 is shown in Fig.4 b.

(a)

Fig.4: Strip speed and exit thickness [m] vs. time [s]

O

he future work belongs to the final model tuning n-up simulations during kissed-rolls and

upport of the present work in the framework of the Center of Competence in

Mechatronics (ACCM) is gratefully acknowledged.

(b)

UTLOOK

Tbased on ruTCM strip rolling state.

ACKNOWLEDGEMENT

Speer reviewed Austrian

Page 53: 2-page abstracts booklet

A Transducer for Normal Pressure, Friction Stress and Contact Length

Measurements in Hot and Cold Flat Rolling of Metals

A. Nilsson (Swerea MEFOS, Sweden)

N-G. Jonsson (Jernkontoret, Sweden)

J. Lagergren (Åkers Sweden AB, Sweden)

T. Luks (Brno University, Czech Republic)

ABSTRACT

In this work the contact stresses during hot and cold rolling has been measured with the “ROLLSURF” device [1]. The “ROLLSURF” device is a work roll having an internal sensor with strain gauges. With this sensor contact stresses and contact length during rolling can be measured.

THE ROLLSURF SENSOR

The sensor can be described as a contact arc on two “legs”, Figure 1. The strain in the legs is measured with strain gauges. Two signals, one vertical and one horizontal signal are measured on each leg, V1, H1, V2 and H2. By using a calibration procedure a relationship between the signals and the normal and tangential forces is established. In this work the measured contact forces are results of predictions made through a neural network trained on data from the calibration.

Figure 1. The “ROLLSURF” work roll with the insert.

A typical pattern of measured contact signals are shown in Figure 2. The V1 and V2 signal are the vertical forces measured in the two “legs”. The total load is approximately the sum of the vertical signals. This assumption is used when calculating the centre of gravity which is needed as a position value in the model.

Figure 2. Transducer signals during rolling

The neural network uses 5 input signals; the load position along the sensor arc, and the four measured signals. The output from the neural network is the normal load and the tangential load. A prediction is made for each time step of the measured data. The contact force distribution along the contact length can be extracted by studying the force increment in the beginning and at the end of the contact with the sensor. The sensor is in contact with the material during the arc length (40 mm) + the contact length in the roll gap. (A correction for possible pre- and post- contact is needed).

TRIALS

Hot and cold rolling tests were made in Swerea MEFOS section rolling mill, 2 meter long, 30 mm wide bars were rolled. The work roll diameter was 230 mm.

Table 1. Examples of trial data

Cold trial Entry thickness, Hin (mm)

Red (%) Contact length, L (mm)

M06-al 9.99 13.5 18.5

M07-al 8.65 18.4 17.5

Hot trial Hin (mm) Red (%)

M13-steel 9.88 5.8 11.3

M14-steel 9.88 13.4 15.6

M15-steel 9.88 20 17.5

Steel bars were heated to 1000°C and then rolled at different reductions. Contact pressures are shown in Figure 3- 5. The 13% and 18% reductions give similar results for the contact shear stress as well as for the shape of the frictional stresses. The low reduction 6%, has a slightly different shape of the force distribution. In experiment M13 in Figure 3 a double pressure peak is present. Note that the two pressure peaks in M13 is independent of the friction stress seen in Figure 4. This research and earlier measurements [2-3] shows that a pressure peak in the normal pressure does not mean a change of the friction stress direction, in the

Page 54: 2-page abstracts booklet

position for the peak value as often assumed. There is no coupling between the maximum pressure value and the neutral point. The “double-peak” has been explained by J .Lagergren, [2-3]. Under the rolling

geometry of 1 < L/hm 3 and 1 w0/h0 4 this phenomena is most likely to occur. For M13 L/hm = 1.18 and w0/h0 = 3,03, within the “probability limits” given. The first peak - “the indentation hill” - is by Lagergren assumed to be imposed by the material threshold resistance to deform in the first contact within narrow and thick bar rolling - the second peak- is controlled by the well - known “the friction hill”.

Figure 3. Contact pressure for three different reductions when rolling hot steel bars

Figure 4. Contact shear stress for three different reductions when rolling hot steel bars

Figure 5. Friction coefficient calculated as the ratio of horizontal stresses and normal pressure.

Cold rolling tests were also made, here is an example for aluminium, trials with brass and steels were also made.

Figure 6. Contact normal and friction stress for the cold rolled aluminium bars M6 and M7.

Figure 7. Friction coefficient calculated as the ratio of horizontal stresses and normal pressure.

ACKNOWLEDGEMENTS

The authors want in memorial to thank Prof. Tarras Wanheim, at Denmark Technical University, a world-famous scientist in the friction theory field. He was the inventor for this transducer design. The authors also want to acknowledge the research work performed by Dr Poul Henningsen, earlier at DTU and Dr Mogens Arentoft at DTU/IPU, Denmark. Thanks for industrial support from Ruukki, Sandvik Materials Technology and Åkers. The Nordic Innovation Centre, Norway, VINNOVA, Sweden and the Research Found for Coal and Steel are also gratefully acknowledged.

REFERENCES

1.“A surface transducer for roll gap measurements of friction and load in both hot and cold rolling”. N-G.Jonsson,J.Lagergren,T.Wanheim. The International Conference on Tribology in Manufacturing Processes (ICTMP), 13-15 June, 2010, Nice, France, pp.845-855.

2.”Measurements of Multiple normal pressure peaks in flat rolling”. By Jonas Lagergren. Steel Research 68, 1997, No. 7, pp. 313-325

3. ”Double normal pressure peaks in flat rolling”. By Jonas Lagergren. Scandinavian Journal of Metallurgy, 1998, Vol. 27, No. 3, pp. 103-111

Page 55: 2-page abstracts booklet

Oil free lubrication in steel hot and cold strip rolling

1. Reichardt, Tilo; VDEh-Betriebsforschunginstitut, Head of department

2. Deli, Housein; VDEh-Betriebsforschungsinstitut, Project Group leader

3. Myslowicki, Stefan; ThyssenKrupp Steel Europe AG, Material, coordinator development –

division auto

4. Müller, Christian; ThyssenKrupp Steel Europe AG, Engineer process technology – R&D

5. Raulf, Martin; ThyssenKrupp Steel Europe AG, Head of department FuE-C organic chemistry

6. Herrmann, Michael; Chemische Werke Kluthe GmbH, Development and application metal

working and metal protection

7. Dahms, Philipp; Bilstein GmbH & Co KG, Engineer production

8. Mömming, Cornelia; Hydro Aluminium Rolled Products GmbH, Project Manager

Research & Development

INTRODUCTION

Lubrication in metal rolling for steel is used for different purposes. In hot rolling lubricants are applied as oil in water dispersions to decrease of rolling force, to reach more stable process conditions, to decrease wear rates of used work rolls and generate therefore smother surface qualities. Conventional lubrication is based on oil-in-water dispersions applied at strip entry side on the work roll. Work roll cooling on the entry side has to be decreased or shut down to prevent irritation of spreading lubricant film on the work roll body. Oil-in-water emulsions are applied in cold rolling of steel to guaranty a stable lubrication process, cooling of the work rolls and strips and removal of abrasive wear particles produced during the rolling process. Filter aid containing cleaning procedures remove this wear debris but also oil from the emulsion phase. Additionally adhered oil on strip surface generates more losses and has to be removed in degreasing lines before entering subsequent processes New opportunities in already commercial available lubricants and new developments on aqueous oil free lubricants enables new variants of application due to revised mechanism of work. Higher surface qualities in hot rolled strip by coupled cooling and lubrication effect were generated and solutions applied in cold have the advantage, that only one irreversible phase exists which is not miscible with strange oils (hydraulic oil, morgoil). Therefore strange oils can be skimmed

off very easily and filter aid containing care steps will not affect composition – emulsion oil losses which has to be balanced continuously can be avoided.

Secreening of promising lubricants

Beside standardised tests on laboratory stage as SRV, Pin-on-disc, MTM, Block-on-ring etc., which are suitable for a pre-selection pilot mill testing have been performed on most promising lubricants.

For pilot hot rolling test an application of all chosen lubricants directly into the roll bite have been chosen. Different concentration levels at constant flow and pressure rates were used. An overview about achieved results can be seen in Fig 1. Rolling force as well as torque reduction were logged and used for generating mean values over the rolling campaign of 5 sec in the final pass.

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Figure 1 : Results pilot hot rolling trials

Oil lubrication with 5% dispersion showed best reduction values, then Lub 4 and Lub1 over all chosen concentration levels. By varying application from work roll to roll bite to strip surface, it was noticed that application of oil dispersion only work properly on roll surface and roll bite and is more sensitive against cooling water irritation. Furthermore cooling effect for

Page 56: 2-page abstracts booklet

lub1 and 4 was increased about 30 % compared to unlubricated process.

Based on these positive laboratory results H4P2t (with increased additive package), C1Pe and the C2O have been chosen for performance of pilot cold rolling trials. Table 1 indicates the process parameters of the 4 pass schedule with 100mm width carbon steel.

Table 1 : Schedule for pilot cold rolling trials

Pass 1st 2nd 3rd 4th

Entry thickness (mm)

2 1,25 0,75 0,43

Exit thickness (mm) 1,25 0,75 0,43 0,24

Entry tension (MPa) 8 10 10 8

Exit tension (MPa) 10 10 8 5

Rolling speed (m/s) 2,5 5,2 10 7

Rolled length 240 380 640 1120

Lubrication flow was constant at 2.4 m3/h at the entry side, applied with one central nozzle top- and bottom-side and 3.2 m3/h at the exit side, applied with three nozzles each. Cleaning properties of applied lubricants have been examined additionally after each pass and all three chosen lubricants have been applied on one strip in the same campaign. Therefore the behavior in the same process conditions can be compared directly. Up to the third pass, figure 2, performance of the glycolbased lubricants (H4P2t and C1Pe) and the recycled oil (C2O) are quite similar or even slightly better compared to the performed reference trials. For cleaning ability clear advantages of the glycols compared to the standardized lubricants in the reference trials have been observed. The very thin material is very sensitive against tension variation. In the last pass problems occurred which leds to strip failures and a final comparison of process parameters and achieved strip surface qualities was not possible.

Figure 2: Rolling parameter evolution for steel cold rolling with glycolbased lubricant, 3rd pass

Summary

Oilfree lubricants are an alternative to conventional oil containing lubricants for hot rolling due to less sensitivity against irritation by cooling water on tools regarding lubricity and potential of application. Further advantages by additional cooling aspect and improved environmental impact are given. The overall performance and economic aspects have to be further improved.

Glycolbased lubricants are a promising alternative to conventional oil containing emulsions applied for cold rolling of steel either hot rolling of aluminium. Comparable rolling properties, increased surface and cleaning aspects as well as significant simplified care aspects enables annual costs savings due to less costs for oil losses and deposition by continuous treatment. Further targeted development and longterm effects have to be evaluated.

Acknowledgments

The authors gratefully acknowledge the funding by the research fund for coal and steel (RFCS) of the research projects CHILLUB, contract no. RFCS-CT-2008-00012, and LUBWORK, contract no. RFCS-CT-2008-00011.

Page 57: 2-page abstracts booklet

Study of tribological oxide

layer behaviour during the hot rolling of ferritic stainless

steels

Luc Emilie a,b, Dubar Mirentxua, Dubois Andréa, Hermant Alexandreb, Dessis Arnaudb, Damasse

Jean-Michelb, Dubar Laurenta

a - Laboratoire Tempo EA 4542, Institut Carnot ARTS, Université de Valenciennes et du Hainaut Cambrésis, Le Mont Houy 59313 Valenciennes

cedex 9 b – Aperam, Centre de Recherche, BP15 62330

Isbergues

The evolution of engines (new fuels, new engine technologies…) induces a modification in combustion parameters and the major modification results in an increase in exhaust gas temperature. As a result, we need to design new grades with higher corrosion and creep resistance. The design of a new grade is made by changing the rate of definite chemical elements known for their impact on corrosion and mechanical resistance. Chromium is known for increasing drastically the corrosion resistance. In ferritic stainless steel, its rate varies from 11 to 22 %. The Molybdenum added to the Chromium confers also a higher corrosion resistance. As these high alloyed steels have different behaviors compared to the standard ferritic grade 430, their design induces new challenges in their production.

New defects occur in the production of hot rolled flat products on the grades containing more than 17% Chromium. These defects lead to a constellation of rolled-in particles on the sheet surface which cannot be removed during the final cold rolling sequences. The presence of these defects induces two major problems:

• the product does not meet standard esthetics requirements for the high quality market,

• corrosion preferentially appears on the incrusted particle area leading to a decrease in the product life.

The origin of these defects is linked to the sticking of the hot rolled product on working cylinders of finishing mill [1,2]. The sticking is due to the high chemical affinity between the product, which contains

at least 17% Cr, and the cylinder, which approximately contains 6% Cr. Sticking can only occur when there is a direct metal-metal contact between the two antagonists. Due to the high temperature of the product during this process step (between 950°C and 1070°C), an oxide layer grows on the product surface and prevents direct metal-metal contact, so decreases the sticking phenomenon. As a result, the product temperature is an industrial actuator to limit the defect occurrence. In order to set up the appropriate temperature condition on the hot strip mill line and understand how the oxide layer protects the product surface, the effect of temperature on the tribological system has been investigated.

A new testing device has been designed in order to simulate the contact conditions encountered on the industrial finishing line [3] (Fig.1). In order to understand the behaviour of the product in the finishing mill, the use of a real slab is essential. So, the tribological test involves cylinders machined from real work rolls and tests are performed on specimens machined from industrial slabs in order to respect the physicochemical properties of the contact (Fig.2).

Test parameters are adjusted in temperature and reduction ratio by means of FEM to respect industrial thermo-mechanical conditions.

Fig.1 hot rolling testing device

• specimen: 4 mm thickness, machined from an

original ferritic slab (445 grade) • Induction heating up to 1100°C • Bi-chromatic pyrometer • 80 mm diameter work cylinders: HSS grade,

machined from original work rolls • normal and tangential forces acquisition

Page 58: 2-page abstracts booklet

REFERENCES:

[1] C.Y Son, C.K. Kim, D.J. Ha, S. Lee, J.S. Lee, K.T. Kim, Y.D. Lee, Mechanisms of sticking phenomenon occurring during hot rolling of two ferritic stainless steels, Metallurgical and materials transactions A, vol 38A, nov. 2007, pp. 2776 – 2787. Fig. 2: specimen extracted from the original slab [2] D.J Ha, C.Y. Son, J.W. Park, J.S Lee, Y.D. Lee, S. Lee, Effects of high temperature hardness and oxidation on sticking phenomena occurring during hot rolling of two 430J1L ferritic stainless steels, Materials science and Engineering A, 492, 2008, pp. 49 – 59.

The first tests were performed on the hot rolling testing device with temperature increasing from 880 to 1080°C. The thickness reduction was equal to 14%. Specimens were in 445 steel grade. Figure 3 presents the cross section of the sample in the rolling direction.

[3] Deltombe R., Dubar M., Dubois A., Dubar L. (2010). Toward Oxide Scale Behavior Management At High Temperature, AMPT 2010, Paris, F, AIP Conference Proceedings, pp. 793-798

On the 1080°C specimen, the scale layer seems to be more homogenous and the average thickness is very small (3 µm) compared to the other specimens (around 15 µm). This layer is able to prevent the two antagonists from direct contact.

A transient temperature in oxide layer behaviour is highlighted at 1070°C. From this temperature the oxide layer is co-rolled onto the product, which could be linked to the enrichment of Cr oxide in the scale layer, as confirmed on [1,2].

Fig.3: Cross section of the specimens in the rolling

direction.

Page 59: 2-page abstracts booklet

Development of the prediction

model for hot strip flatness after coil cooling

M.Miyake,Y.Kimura,T.Kawai,T.Hiruta

(JFE Steel Corporation, Japan)

1.INTRODUCTION:

Quality assurance for the flatness of hot strip is of great importance for steel manufacturers because customer’s requirements for the flatness have been getting severe. Rolling and inhomogeneous cooling on the run-out table are well known factors which deteriorate strip flatness. Besides aforementioned factors, we have focused on the thermal history after coiling till room temperature. Hot coils have large temperature distribution because their external sur-faces are cooled down by heat transfer and radiation to the atmosphere. On the contrary, temperature of the core part of the coil changes very slowly by heat conduction toward external side. This generates residual stress in the coil due to inhomogeneous thermal shrinkage. Slow deformation under high temperature condition induces creep phenomena and this may lead to the large elongation of the strip.

In this paper, numerical analysis model for thermal and deformation of hot strip on the run-out table and in the coil till room temperature are presented. And the flatness of final strip product was estimated by the difference of eternal strain in the width direction.

2. OUTLINE OF THE ANALYSIS MODEL:

2-1 Run-out table model

To predict thermal transition of the strip on the run-out table, thermal analysis and phase transformation analysis were coupled. Thickness profile, steepness

and temperature distribution in the strip just after the last rolling stand were used as initial conditions for the analysis on the run-out table. To shorten the computational time, only one element was adopted in the thickness direction under the assumption of uniform temperature. In this way, one dimensional thermal analysis in the width direction was conducted at each time step under each assumed boundary condition. Time-temperature-transformation diagram was utilized and the additivity rule was adopted for incremental analysis. Volumetric strain εT, creep strain εc and plastic strain εP were considered. As for stress analysis, slit model was employed. Summation of longitudinal stress σe along width direction should be equilibrium with total strip tension and average strain in the longitudinal direction εm can be decided with this relation.

2-2 Laminated cylinder model for a hot coil

Symmetrical and laminated cylindrical condition were assumed for coiling model. To express the contact conditions between each cylinder during coiling, strip crown profile and the shape of outer surface of each cylinder were considered. For the analysis of tension distribution in the width direction, modified slit model was adopted by considering the strip thickness profile and pre-wrap cylinder surface. In the same way with the run-out table model, longitudinal stress σe and average strain εm were derived from tension equilibrium conditions and neighboring interaction.

2-3 Thermal and deformation analysis of a hot coil

Temperature transition in a hot coil was analysed with finite differential method. Two dimensional model in the width direction versus radial direction was employed under the assumption of axial symmetry. Contact condition between each cylinder was judged by contact pressure at each position in the width direction. If the strip crown is large enough to make clearance around strip edge, the conductivity of air was considered.

Stress components can be calculated with pressure acting on the inner and outer surface of each cylinder. Pressure was decided with coiling tension, equilibrium conditions for each cylinder and compatibility conditions. Contact analysis was continued iteratively until all contact pressure became compression or

Coil yardCoil yard

・Phase transformation analysis・Thermal analysis・Visco-plastic analysis(Laminated cylinder model)

・Phase transformation analysis・Thermal analysis・Visco-plastic analysis(Laminated cylinder model)

# Initial conditions・Temperature distribution・Strip shape & thickness profile

ThermometerShape meter Run-out table

Coiler

ThermometerShape meter

Finishing mill

【Longitudinal stress】⇒ Plastic deformation

Width

Longitudinal

Width

Longitudinal

Thermal shrinkage

【Temperature】Low at strip edge

・Phase transformation analysis・Thermal analysis・Visco-plastic analysis

(Slit model)

Radial

Compression【Radial stress】Tighten by winding

Width

Consideration of contactcondition due to strip profile

【Temperature】High at inside

【Radial stress】

CompressionLow

HighTension

【Circumferential stress】⇒ Creep stress

W dth

Radial

Thermal shrinkage

Radial

Compression

Radial

W dth Width

Coil yardCoil yard

・Phase transformation analysis・Thermal analysis・Visco-plastic analysis(Laminated cylinder model)

・Phase transformation analysis・Thermal analysis・Visco-plastic analysis(Laminated cylinder model)

# Initial conditions・Temperature distribution・Strip shape & thickness profile

ThermometerShape meter Run-out table

Coiler

ThermometerShape meter

Finishing mill

【Longitudinal stress】⇒ Plastic deformation

Width

Longitudinal

Width

Longitudinal

Thermal shrinkage

【Temperature】Low at strip edge

・Phase transformation analysis・Thermal analysis・Visco-plastic analysis

(Slit model)

Radial

Compression【Radial stress】Tighten by winding

Width

Consideration of contactcondition due to strip profile

【Temperature】High at inside

【Radial stress】

CompressionLow

HighTension

【Circumferential stress】⇒ Creep stress

W dth

Radial

Thermal shrinkage

Radial

Compression

Radial

W dth Width

Figure1 Schematics of the prediction model for hot strip flatness after coil cooling

Page 60: 2-page abstracts booklet

almost uniform in the whole coil. So the variation of eternal strain is almost dominated by creep strain.

zero. After the convergence was achieved, each stress and strain at every evaluated point was calculated. This routine was continued until coil temperature became room temperature. Steepness of the strip was evaluated with the variation of longitudinal strain in the width direction.

3. ANALYTICAL RESULTS AND DISCUSSTION:

3-1 Analytical conditions

Employed analytical conditions are shown in Table1. Actual change in parameters from strip head to tail end, for example strip thickness profile, velocity pattern, temperature transition at width center and tension history, were used in this analysis. Temperature dependency was considered for mechanical properties such as young’s modulus and yield stress(0.2% proof stress). Also phase transformation was considered in the yield stress model.

Table1 Analytical conditions Grade Mild steel (C0.09%) Strip size 2.62mmt x 1229mmw x 1084mL Coil size Outer diameter : φ2050mm

Inner diameter : φ762mm Heat transfer coefficient

Water: 1163 W/m2K Air: 15 W/m2K (run-out table) 9 W/m2K (coil)

Temp. FDT: 1143K, CT:863K Coiling

tension 12MPa → 8MPa (decline in a

linear manner along strip)

3-2 Analytical results and discussion

Figure2 shows circumferential stress component in the coil after cooling. During air cooling, high compressive stress in the radial and circumferential direction are generated due to thermal shrinkage caused by heat removal from outmost, innermost and width edges of the coil. High compressive stress can be seen around width center of inner area but it is almost zero around width edge area. This is because strip crown profile was taken into consideration in this analysis and zero stress state indicates the existence of air gap. Figure3 shows eternal strain distribution in the coil at room temperature. Plastic strain is not generated with this condition and volumetric strain is

-0.0095

In order to evaluate the flatness of hot strip product, the difference of elongation strain between width center and 100mm position from width edge Δε was defined. It is well known that steepness of the strip can be expressed with Δε. Figure4 shows the transition of steepness along longitudinal direction which was gotten with the eternal strain distribution. Flatness of the strip changes from edge wave to center buckle in this case. This tendency seems to be quantitative nature because the difference of cooling speed in the hot coil generates it. This phenomena depends greatly on the creep behaviour as stated before, but more study is needed to verify the mechanism with other steel grade, coiling temperature and so on.

4. CONCLUSIONS:

Numerical analysis model which enables to predict the flatness of final hot strip products along whole length is presented. It appeared that resulting temperature difference in the hot coil during cooling causes large stress distribution and this has large influence on the strip flatness through creep deformation. As a result, strip flatness changes from edge wave to center buckle along longitudinal direction with the studied conditions.

-0.01

00

-0.0095

-0.0095

-0.0090

-0.0095

-0.0100

-0.0105

-0.0110

Coil outer surface

Coil inner surface Width

Radial

Eternal strain

Figure3 Eternal strain in the coil after cooling (room temperature)

λ

-2.0%

-1.5%

-1.0%

-0.5%

0.0%

0.5%

1.0%

1.5%

2.0%

0 200 400 600 800 1000 1200

Stee

pnes

s

Longitudinal position (m)

Edge wave

Center buckle

Size:2.62t x 1229w mm

Figure4 Transition of strip flatness in the longitudinal direction

Leading end Tail end

επ

λ Δ±=2

-5050

50

150

-50

50

50

150

50

-50

-150

-250

-350

Coil outer surface

Coil inner surface Width

Radial

Circumferential stress (MPa)

0

Figure2 Circumferential stress in the coil after cooling (room temperature)

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PROBLEM OUTLINE When producing steel strip, one of the inherent delays in production is the cooling of the coil between hot rolling and cold rolling. For metallurgical reasons, the hot rolled strip is coiled at various coiling temperatures ranging from 200°C to 750°C. However, for following installations coil temperatures need to be lower than 80°C. This means that some time is needed for the coil to cool down sufficiently for down stream processing.

PROCESS OVERVIEW In the Tata Steel integrated steel plant in IJmuiden two installations produce hot rolled strip, the Hot Strip Mill (see Figure 1) and the Direct Sheet Plant. The coils coming off the lines are transported to indoor cooling bays.

Figure 1, Hot Strip Mill, producing hot rolled coils Some of the coils can be cooled faster by routing them through water basins. When in the indoor cooling bay, coils can be moved to and from outside areas.

The coils can be scheduled for a number of following processes, such as: Hot rolled coil cooling and

availability system

Geert Paulussen, Arnold Koorn, Piet Seijts, Henk Hoogland, Louis Stortelder

• Skin passing • Sample taking • Pickling for cold rolling • Pickling for customer • Direct shipment to customer. For each of these processes different maximum coil temperatures apply.

OLD SOLUTION In the past, the cooling time was predicted once, based on a worst case scenario. The cooling period was taken sufficiently long for the biggest coils to be ready for processing on the most demanding installation. As a result, the average cooling time was significantly longer than strictly necessary.

NEW SOLUTION With the new coil cooling time prediction, the cooling time is predicted taking into account many additional parameters to improve the prediction reliability. The calculation produces a “producible” date-time stamp for the scheduled next installation. Parameters taken into account are: • Coiling temperature • Remaining austenite to transform • Coil dimensions: width, diameter and gauge (see

Figure 2) • Ambient temperature: indoor or outdoor • Ambient condition: water basin or air cooling • Target temperature, dependent on scheduled

following process

Figure 2, coil cooling prediction system with dependencies Changes in the ambient condition or target installation will trigger a recalculation of the “producible” date-time stamp. A change in coil location, moving from an indoor to an outdoor stock area, will result in the coil cooling down faster and becoming available for the next installation sooner. Similarly, when a target installation changes, the coil target temperature may change which is reflected in a new “producible” date-time stamp.

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CALCULATION IMPLEMENTATION IT IMPLEMENTATION Because the actual cooling process evolves as an exponential cooling curve, the basis of the calculation is an exponential curve equation. By combining measured coil temperatures and modelling results, the coil dimension parameters were fitted for air and water cooling. By combining calculations for each ambient step, the total cooling can be calculated (see Figure 3). In combination with the coil start temperature, coil end temperature and ambient temperature the calculation can be used for all cases, such as air cooling indoors, water cooling and air cooling outdoors (see Figure 4). The coil temperature evolution is given by the following equation:

As part of the implementation of the new cooling equation, all hot rolled coil tracking and availability calculation functionality was consolidated into a single IT system (see Figure 5).

( ) ( )( ) ambient

tambientcoilcoil TeTTtT +⋅−= ⋅α0

Figure 5, schematic overview of the "hot rolled coil cooling and availability system"

The calculation is called initially when the hot rolled coil enters the system to produce a “producible” date-time for the scheduled next installation. Changes in the coil location or target installation spark an event that causes the calculation to look back in time, calculate the coil temperature at the time of the event, and produce a new “producible” date-time for the changed ambiance or installation. With this method, the “producible” date-time stamp remains correct and current for the latest coil status.

Figure 3, cooling prediction with subsequent air and water cooling phases

IMPLEMENTATION RESULTS The equation can be easily inverted, allowing its use to calculate the coil temperature as a function of time, or the time as a function of coil temperature. In addition, the calculation can be used in sequence for changing ambient condition (α) or ambient temperature (Tambient). Remaining austenite transformation is modelled as an offset on the coil start temperature (Tcoil(0)).

Although the increased entry temperature at the pickling lines was some cause for concern, implementation has not resulted in additional rejects. Implementation of the Hot Rolled Coil Cooling and Availability System has led to an average reduction of the scheduled cooling time of 21%. In addition some energy savings are achieved in the pickling lines because of the increased coil temperature at entry.

If the reduction in cooling time is not utilized, the number of available coils increases. This improves the schedule quality for following installations because of the large scheduling population.

Figure 4, outdoor cooling and stock area

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Striving for ultra-high strength and direct quenched hot band.

Modernization of SSAB’s hot strip mill

M. Thurgren, R. Högberg, E. Johansson, P. Sixtensson

(SSAB, Borlänge)

K. Eckelsbach, H. Metz, M. Wagener (SMS Siemag AG)

INTRODUCTION

As part of its strategic development, SSAB have renewed the delivery section of its hot strip mill at Borlänge, Sweden, over the recent past years. In several modernization steps new down coilers, a new coil transportation system with inspection line, a new run-out table with new laminar cooling and a new water treatment plant were installed. In addition new level 2 systems for the finishing mill and the laminar cooling were put into operation.

All modernization steps were performed during the scheduled annual shut downs in order to minimize production losses. Target of all investments was the production of high strength steel with a tensile strength in excess of 1,100 MPa and direct quenched (DQ) hot band in the thickness range of up to 8 mm.

NEW DOWN COILERS

In a first step of the comprehensive modernization the existing down coilers were replaced. The new down coiler no. 4 went into operation before the summer shut down 2008. The right sequencing of the modernization steps ensured that times where only one coiler was available were minimized to 11 working days. Down coiler no. 5 was commissioned during autumn 2010.

Both new down coilers are capable to wind high strength steel (1,100 MPa) up to 8 mm, mild steel up to 25.4 mm.

NEW COIL CONVEYOR WITH INSPECTION LINE

The existing chain type conveyor with transportation of the coils with vertical axis was replaced by a walking beam system with the coil axis horizontal.

In addition an inline inspection station was integrated in the conveyor system to inspect strip sections up to 7 m length from both sides. The station can also be used to remove defective strip ends.

The new coil conveyor was put into operation together with down coiler no. 5 after summer shut down in 2010.

NEW RUN-OUT TABLE WITH LAMINAR COOLING

The new cooling line provides the high cooling rates needed for the DQ grades but also the sensitive control for the other grades of the product mix. The ROT-cooling line consists of twelve cooling zones, 11 zones with six valves (2 headers per valve) and one “trimming” zone with 12 valves (one per header).

The complete run-out table with laminar cooling was pre-assembled adjacent to the mill and was integrated into the hot strip mill section by section during summer shut down 2011.

NEW WATER TREATMENT PLANT

The water treatment plant has a capacity of 15,500 m³ per hour. The water coming from the cooling line flows into an entry basin via a scale flume and is then pumped into a sedimentation basin. Part of the water is then further purified in a sand filter system.

Water cooling is achieved by heat exchangers in a closed circuit in a highly efficient way. The purified and cooled water is then pumped into a high water reservoir and can be reused for strip cooling. Water used for strip cooling is in a closed circuit and is not in contact with other process water for the hot strip mill.

NEW SET-UP MODELS

New level 2 set-up models were implemented for the finishing mill and the cooling section, based on physical-mathematical calculations. These models were integrated in the existing automation structure with only small adaptions on the present basic automation systems.

The pass schedule model PSC® delivers all necessary data for the pass schedule set-up and additional information regarding the microstructure evolution such as austenite grain size and accumulated strain. The model for profile, contour and flatness (PCFC®) is responsible for the set-up of CVC® shifting and work roll bending. Both models are interacting in order to achieve an optimal and stable overall mill setup.

The cooling line model CSC® describes the micro-structure as a function of the chemical composition at different temperatures and cooling rates. For each chemical composition the model ascertains the transformed shares of ferrite, pearlite, bainite and martensite which are important to set the desired mixed structure when producing e.g. DQ material.

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The new model for the cooling line is an upgraded version with the latest developments and adapted to the new cooling line. Commissioning was extremely short: After only 18 test strips for different steel grades, continuous production for the market was recommenced. The performance of the model is shown in figure 4.

OPERATIONAL RESULTS

Only three weeks after start-up of the new laminar cooling, the first Hardox® steel was produced, requiring coiling temperatures of approx. 100°C (fig. 1). During autumn 2011, the dimensions and grades were extended.

Fig. 1: Example on result of coiling temperature for a DQ steel

During 2012, Hardox® 400 and 450 were produced in the hot strip mill and established in the market.

Fig. 4: Head end coiling temperature performance  Hardness HBW

425-475

Mechanical Properties Yield strength Tensi le strength Elongation

Typical values for Re Rm A5

Mpa Mpa %Width = 1600 mm and thickness 3-6 m m lo ngitudial

1250 1450 8

Impact Properties

Testtem perature

Impact e nergyCharpy-V, longitudinal

Impact energy halfs ize te st specimenCharpy-V, Transvers e

Typical value for C J JW idth = 1600 mm and thickness3-6 m m -40 - 25 Fig. 2: Technical data of Hardox® 450

The new Water Treatment Plant is able to keep the outgoing water temperature to the cooling line at target within ± 4°C. This is a big improvement compared to the old system which was dependent on the river water temperature and the outgoing water temperature could vary between 15 - 35°C.

CONCLUSION AND OUTLOOK

With the implementation and successful commissioning of the new delivery section of the hot strip mill, SSAB has now reached its strategic target to extend the product and dimension range for high strength steels (DQ and HSLA). The complete SSAB Hardox® wear plate program now covers the thickness range from 0.7 to 130 mm.

With the new set up models the performance of the hot mill has improved further. The main benefits of the new set up model for the finishing mill are improved threading stability and thickness performance (fig. 3). The new systems allow SSAB now to easily develop

new products and dimensions.

In addition SSAB and SMS Siemag have a strong basis for further development of a model for calculating the micro structure evolution over the complete process, which can be used for predicting material properties online and for analysing/improving mill stability problems.

Fig. 3: Head end thickness performance

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Session 5: Blast furnace

Table of Contents

5.1 Dry Slag Granulation - The Environmentally friendly way to making cement I. McDONALD, A. WERNER (Siemens VAI Metals Technologies Ltd), United Kingdom

5.2 Results of the co-injection of PCI and synthetic titanium dioxide products for protection of the hearth of Rogesa blast furnace Nr. 5 after stop for relining W. HARTIG (AG der Dillinger Hütte), D. AMIRZADEH-ASL (Sachtleben Chemie), D. FÜNDERS (Gesellschaft für Synthetische Rohstoffe), Germany

5.3

Reduction kinetics of fine hematite ore particles in a high temperature drop tube furnace Y. QU, Y. YANG, R. BOOM (Delft University of Technology), The Netherlands

5.4

Control technique of material discharge behavior on center feed type top bunker Y. KASHIHARA, A. MURAO, Y. SAWA, M. SATO, K. YAMAMOTO (JFE Steel Corporation), Japan

5.5

Logistic model of hot metal distribution by torpedo ladles at Rogesa in Germany H. RAUSCH, R. LIN (AG der Dillinger Hütte), Germany

5.6

World's first laser profile-measurement-system for the refractory lining of hot torpedo-ladles R. LAMM (MINTEQ International GmbH), Germany

5.7

Optimised operations to improve slag skimming of hot metal desulphurisation slag G. PARKER, H. THOMSON, A. FERGUSON (Tata Steel), United Kingdom

Page 66: 2-page abstracts booklet

Dry Slag Granulation – The Environmentally Friendly Way

to Making Cement

Ian McDonald, Andrea Werner (Siemens VAI Metals Technologies)

INTRODUCTION Currently the state-of-the-art practice to solidify molten blast furnace slag is by rapidly cooling in granulation plants using large volumes of water or by simple tipping in open slag pits. In the case of a wet product, the granulate produced has to be dried with significant input of energy before further processing in the cement and concrete industry. Furthermore, both with this conventional granulation technique and with the alternative pen cooling which forms a crystalline lump slag, there is no possibility of utilizing the considerable heat potential of liquid slag. As liquid slag bears one of the largest high-temperature reserves in the steel industry that is still not utilized, heat recovery from slag is a matter of great relevance. Accordingly, the aim of the project is to develop a reliable dry quenching technology for molten blast furnace slag to recover the high-temperature waste heat (about 1.5 GJ/t) while reaching the process conditions required for the production of glassy slag suitable for use in the cement industry. Substitution of Cement Clinker with Slag Sand Traditional manufacturing of cement clinker from limestone, sand, clay and other components requires a high-temperature process (around 1450°C). It is also associated with high demand for raw materials, high input of primary energy and high specific CO2 emissions (roughly 1 t of CO2 per ton of clinker). The substitution of cement clinker by blast furnace slag sand is an attractive economic alternative for the cement industry, because it reduces high energy costs and considerably improves the company’s CO2 balance. Approximately 1 ton of CO2 can be saved for each tonne of clinker substituted by slag sand because not only primary energy is saved, but also the release of the carbon dioxide chemically bound in the limestone is avoided.

DRY GRANULATION – Alternative Technique to wet granulation for Producing Vitreous Blast Furnace Slag. Huge amounts of water and of drying energy can be avoided by dry dispersion and quick cooling of the liquid slag. The essential prerequisite for the introduction of an alternative dry technique is that the obtained product needs identical or even better properties compared to the slag sand produced conventionally using wet granulation. This applies in particular to the glass content (target > 95%), which is a key parameter for the reactivity and hence the quality of the slag sand. The glass content has a direct impact on the strength of the cements and concretes. However, the required glass content can only be achieved by sudden cooling below the transformation temperature of approximately 900°C. Due to the less efficient cooling mechanism of water-free quenching, the dry process is technically more challenging than conventional water based granulation. Obviously “dry” granulation requires no subsequent drying of the product. This leads to a CO2 reduction of roughly 30 kg/t in comparison with wet process. Given global production of approximately 210 million t of slag sand (2007), this is equivalent to a potential CO2 reduction of over 6.3 million t per year. The Concept

Spinning cup

Slag Runner

Modified Fluidised Bed

Granulated Slag

Cooling air in

Main drive shaft & bearings

Hot Air to Chimney

Static water jacket

Fig.1 Dry Granulation Concept

Dry slag granulation is based on molten slag atomisation using a variable speed rotating cup or dish (see Fig.1). The slag is delivered on to the centre of the cup from a slag runner via a vertical refractory lined pipe. The rotation of the cup forces the slag outwards to the cup lip where it is atomised. The resulting slag droplets cool in their flight towards the water jacketed chamber wall. On impact with the wall, the droplets are sufficiently solid to ensure they do not stick to the wall. This characteristic is further enhanced by the presence of the water jacket. The solidifying granules fall into a mobile bed of granules that is designed to ensure that there is no

Page 67: 2-page abstracts booklet

agglomeration. The bed is kept in motion by the design of the cooling air distributor that imparts a circumferential motion to particles.

Block Crushing Strength (N/mm3) Curing Time(Days) 100% OPC* 50% OPC / 50%

DSG 1 3 7 28 90

14.9 28.0 39.3 49.2 50.1

3.5 9.4 14.7 36.4 51.1

Notes OPC – Ordinary Portland Cement DSG – Dry Granulated Slag

Chemical and Mechanical Properties Blast furnace slag is considered unfriendly when fresh because it gives off sulphur dioxide, and in the presence of water Hydrogen Sulphide (rotten egg smell) and Sulphuric acid are generated. These are at least a nuisance and at worst potentially dangerous. Fortunately the material stabilises rapidly when cooled, and the potential for obnoxious leachate diminishes very rapidly after the ‘first flush’. However, the generation of sulphuric acid causes considerable corrosion damage in the vicinity of Blast Furnaces. The dry granulation process eliminates H2S and significantly reduces sulphur emissions, furthermore the leachability of sulphur and other compounds is also reduced due to the glassy nature of the product.

Heat Recovery Developments Several systems capable of utilising the energy in hot air delivered from the granulator have been considered. The major complication is the intermittent availability of molten slag. The temperature of air leaving the granulator is estimated at 400° C. By tuning the cooling air distribution this could be increased significantly, perhaps to 650° C. The hot air could be used for direct heating or drying or for steam raising, in which case an accumulator would be necessary to even out the steam flow. Recovery systems are applicable to both blast furnace slag granulators and to slag pot systems.

The product quality is as follows:- +95% Glass A typical size analysis is given below: Sieve sizes & % passing mm 4.74 2.36 1.18 The crucial advantage of dry granulation, however, is

the additional heat recovery. % 100 85 46

Depending on the plant setup the energy can be used directly for preheating or heating purposes (Fig.4), or for the production of process steam and/or electricity (Fig.5). An energy potential of more than 20 MWth or alternatively a power generation of about 6 MWel was calculated for a slag mass flow rate of 1 t/min - which is the average slag flow for a blast furnace with an annual production of 1,7 Million tonnes and a slag rate of 30%.

Fig.6 Dry Granulated Slag

In addition, since slag granulate is to be used as feedstock for the cement industry, the following parameters are also important: Grinding time to achieve 424 m2/kg = 105 min (Using ball mill) Fig.5 Dry slag granulation with steam / power

generation – In case of power generation a potential of ~ 6MWel was calculated for a slag

mass flow rate of 1t/min

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RESULTS OF THE COINJECTION OF PCI AND SYNTHETIC TITANIUM DIOXIDE PRODUCTS FOR PROTECTION OF THE HEARTH OF BLAST FURNACEES AFTER STOP FOR RELINING Walter Hartig, Djamschid Amirzadeh-Asl, Dieter Fünders ROGESA; DILLINGEN HÜTTE; DILLINGEN-SAAR; GERMANY SACHTLEBEN CHEMIE; DUISBURG; GERMANY SUMMARY Wear protection by local synthetic Titanium dioxide materials injection at various blast furnaces has been investigated intensely with very successful results in the past years. At ROGESA (Dillinger, Germany) blast furnaces No. 4 and No. 5 a mixture of pulverized coal and synthetic Titanium dioxide (RUTILIT NF) has been injected simultaneously in order to protect the hearth from premature erosion. This paper is a common report from AG der Dillinger Huettenwerke (ROGESA, Dillingen, Germany) and SACHTLEBEN Chemie GmbH (Duisburg, Germany). KEYWORDS Blast furnace hearth repair, synthetic titanium dioxide injection, RUTILIT, TiCN protection layer. Comparison of different methods to use Titanium containing materials The injection of fine-particulate TiO2 (RUTILIT) sources via the tuyeres directly in the vicinity of the hearth zone is a more effective method of importing TiO2 into the BF. This technique offers a lot of advantages: • Injection occurs in the immediate vicinity

of the endangered areas of the masonry. This means that best possible results can be achieved systematically well spotted and with low input quantities.

• The delay period before the reparative action occurs is much shorter, even in case of "hot spots" in the furnace wall.

• Lower input rates and higher efficiency of conversion to Ti(C,N) compounds result in improved slag quality, thanks to lower TiO2 contents in the slag, and therefore easier marketing of the ultimate blast furnace sand product.

Input of titanium bearing products at ROGESA blast furnaces Time interval BF No.4 BF No.5 Input Average

addition/ Injection rate

Lump Ilmenit June 4th to Nov. 1th 2005

Repair of Hot Spot

Charging with the burden

5- 9 Kg/t HM

RUT LIT F 50

July 1th to Oct. 7th 2005

Repair of Hot Spot

Separate Injection Sytem

3 Kg/t HM

RUT LIT NF July 20th 2008 to July 17th 2010 (BF No. 5) July 20th 2008 till now (BF No. 4)

Preventive application

Preventive application

with PCI 1 to 2 Kg/t HM

Table 1: Time interval of titanium bearing products Example of blast furnace No. 5 in 2005 before interim hearth repair Former investigations at ROGESA blast furnace No. 5 in 2005 showed that the injection of RUTILIT F50 over single tuyères is much more effective than the feeding of lumpy Ilmenite with the burden Because of the good results using the RUTILIT F50 in 2005 to reduce local hot spot formation and for preventive action, ROGESA and SACHTLEBEN developed the coinjection of RUTILIT NF together with the pulverized coal. Pulverized coal injection (PCI) installations and preparation of mixture with RUTILIT NF The new process results in a constant concentration of RUTILIT NF in the fed raw coal. After the transportation of the mixture to the raw coal bin, a simultaneous grinding, drying and further mixing of the two components takes place in a vertical Loesche mill. The injection into the blast furnaces takes place by single line controlled coal quantity with coaxial oxygen lances for each tuyere with a Paul Wurth injection plant . Injection conditions of RUTILIT NF/PCI coinjection Long-term test: - Injection period: (start: July 20th 2008 to July 17th 2010 (BF No. 5) and July 20th 2008 till now (BF No. 4)) - Addition of RUTILIT NF to raw coal at various levels in the range of 0,8 – 1,6 % referred to raw coal

Page 69: 2-page abstracts booklet

- After grinding and drying the mixture was injected continuously into BF No. 4 and Nr. 5 via all tuyeres.

- Daily production: 6200 t HM BF No. 4 and 6700 t HM BF No. 5 - Total injection quantity of PCI and RUTILIT NF per day: 2000 t/day; 155 kg of pulverized coal and RUTLIT NF / t HM; During the long term test started from July 2008 the total injection quantity of RUTILIT NF was in the range of 1 to 2 kg / t HM; The Titanium dioxide input by RUTILIT NF was in average 0,6 kg TiO2/t HM. Figure: 1 Temperature measurements and

operation data Results of coinjection Electron-microscopic examination and chemical analysis from 2 core samples of BF No. 5

The normal input level of TiO2 in the burden was at 2,0 kg/t HM and was increased to about 3,0 kg/t HM depending on the added quantity of RUTILIT NF. It could be noticed that there was no detrimental effect over the entire coinjection period on the permeability of the Blast Furnace process because the overall pressure drop has not changed.

3 series of core hole drilling at 5 different levels were performed in order to study the behaviour of the different carbon qualities. After the campaign the samples were examined chemically and physically and also the existence of titanium compounds could be detected

The coinjection of pulverized RUTILIT NF and coal with a flow-rate 155 kg/t HM, i. e. 1 - 2 kg RUTILIT NF/t HM did not show any negative influence on the reductants consumption. The HM temperature has a constant level of 1465 – 1485 °C). The slight fluctuation of the Ti content in the hot metal, which has been in the range of 0,04 – 0,08 %, has been caused both by the thermal state of the blast furnace and by the RUTILIT NF coinjection. The TiO2 content in the slag during RUTILIT NF coinjection was maintained below 0,9 %.

These examinations indicate that by the infiltration of liquid hot metal and slag high refractory TiCN/TiN compounds are formed and deposited on the microscopic porosity of carbon block surfaces. The Titanium content in both sample are approximately at the same level. These findings deliver the necessary evidence of a continuous coinjection of PCI and RUTILIT NF contributed to the formation of protective skulls at the critical locations in hearth and bottom. Conclusions Figure 1 shows the operational data which can

influence the hearth temperatures: The long-term industrial test at blast furnace of ROGESA of the coinjection RUTILIT NF with the coal indicated a uniform reduction of temperature at critical BF hearth zones. A good mixing, grinding and drying inclusive a perfect pneumatic conveying into the blast furnaces by all tuyeres has been done without any negative influence and abrasion problems and therefore is still continued. After stopping the hearth walls were examined. Titanium residuals were analysed also in core borings which formed a protective layer during the coinjection periods. The preventive protection with this new and simple technique increases the productivity while saving energy and raw materials costs. At ROGESA the coinjection of RUTILIT NF together with coal will be a measurement to extend the blast furnace hearth life time.

– CSR-value of the coke; low CSR-values increase the hearth temp. because of the increase of the peripheral flow of the hot metal

– Downtime percentage influences the hearth temp. when the furnace is stopped

– RUTILIT NF addition to the injected pulverized coal

Hearth temperatures are significantly influenced by coke quality, number and length of stoppages and the amount of Rutilit injection.

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Reduction kinetics of fine hematite ore particles in a high temperature

drop tube furnace Y. Qu, Y. Yang and R. Boom

(Delft University of Technology)

INTRODUCTION

HIsarna is one of the most promising coal based smelting reduction technologies. It mainly consists of coal preheating and partial pyrolysis in a reactor, a smelting cyclone for ore melting and partial reduction and a smelter reduction vessel (SRV) for final ore reduction. The reduction degree of iron ore in the cyclone reactor is about 20 % through thermal decomposition and reduction by the SRV gas. Up to now, most of the previous studies focused on the iron ore reduction mechanism in the blast furnace process. This study focuses on the individual fine particle reduction behaviour in the cyclone reactor at high temperature, which has not been well investigated in the literature.

EXPERIMENTAL

The kinetic experiment of fine iron ore reduction was carried out in the high temperature drop tube furnace (HDTF) shown in Figure 1. The core of the experimental set-up mainly consists of 6 parts: an electrically heated tube furnace, a syringe pump particle feeder, a particle injection probe, a sampling probe, a gas pre-heater and a sample collector. The alumina tube (Alsint) is adopted as the reactor tube, which is fixed in the electrically heated tube furnace with top and bottom cooling flanges.

The average temperature of the furnace was set at 1380 oC (nominal at 1400 oC). The residence time of the particles ranged from 200 ms to 2100 ms, which was controlled by the gas flow rate. The composition of the raw materials is shown in Table 1. In order to simulate the real gas composition in the cyclone reactor, the iron ore reduction experiments were carried out in the gas mixture (H2, CO, CO2, N2) with different post combustion ratio (PCR, shown in Equ.(1)) which are 38.9 %, 57.8 % and 80.4 %, respectively. The reduction degree f is defined as the ratio of mass loss of oxygen from the iron oxides

in the sample to the total initial removable

mass of oxygen in the iron oxides as shown in Equ.(2). The reduction degree is determined by chemical titration.

oxygenmΔ

oxygen-orem

2 2

2 2 2

CO %+H O%PCR = 100%CO %+H O%+CO%+H %

× (1)

Δ oxygen

oxygen-ore

mf =

m (2)

Figure 1 Schematic diagram of the HDTF

RESULTS

Fractional reduction

The reduction degree increases with the increase of residence time as shown in Figure 2. At the same residence time the reduction degree decreases with the increase of PCR. If hematite is reduced to magnetite completely, the reduction degree is 11.1 %. If hematite is reduced to wüstite completely, the reduction degree is 33.3 %. From the figure, it can be found that all the results are between 11.1 % and 33.3 %. The reduction of hematite to magnetite takes place quickly in the first 200 ms.

0 400 800 1200 1600 2000

12

14

16

18

20

22

24

26

28

Frac

tiona

l red

uctio

n (%

)

t, time (ms)

PCR = 38.9 % PCR = 57.8 % PCR = 80.4 %

Figure 2 Effect of PCR on the reduction of fine iron ore, T = 1380 oC, Particle size: 45-53 μm

Figure 3 gives the effect of particle size on the fractional reduction of iron ore. The results show that the reduction degree of iron ore is almost a linear decrease with the increasing of particles size. It’s also

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observed that the reduction degree is higher with low PCR than with high PCR.

40 50 60 70 80 908

1012141618

2022242628

Fr

acio

nal r

educ

ion

(%)

PCR = 38.9 % PCR = 57.8 % PCR = 80.4 %

Particle size um Figure 3 Effect of particle size on the reduction of fine iron ore with different PCR, T = 1380 oC

Morphology study

Figure 4 Cross-sectional view of iron ore

particle, PCR = 57.8 % a) before reduction, particle size: 75-90 μm; b) after reduction, particle size: 45-53 μm, t=0.21 s; c) after

reduction, particle size: 45-53 μm, t=2.02 s; d) after reduction, particle size: 45-53 μm, t=0.97

s; etched: light area is wüstite

Figure 4 shows the examples of the cross-sectional structure of the iron ore particles before and after reduction. The raw materials of hematite ore has irregular shape but dense crystal structure that is called close-packed hexagonal as shown in Figure (a). But the structure of magnetite is the cubic spinal [1]. The particle in Figure (b) has experienced the reaction time of 0.21 s. The micropores inside the particle were formed during the reduction from hematite to magnetite due to crystal lattice reconstruction. On the other hand, the micropores increase the reacted surface area. It is one of the reasons that cause the quick reduction from hematite to magnetite. As the increase of reduction degree, the dense wüstite increases. This results in the decreasing of the microspores as shown in Figuire 4 (c). It is difficult to

distinguish between magnetite and wüstite. However, after etching for 30 s, wüstite generated by topochemical growth could be identified. The method of etching is given elsewhere [2]. The reduction from magnetite to wüstite takes place at a shrinking core model interface, which is also observed with other reaction times.

Energy Dispersive Spectroscopy (EDS) allows one to identify what those particular elements are and their relative proportions as shown in Figure 5. This particle experiences the same reaction conditions as in Figure 4 (c). The weight proportion of Fe at the centre of the particle is lower than that in the outer layer of the particle. It reflects the shrinking core. The analysis of the original hematite ore has also been done with EDS and it shows that the Fe % is between 67.4–68.9 %.

Point Fe % 1(ring) 72.17 2(core) 70. 86 3(core) 70.86 4(ring) 72.58 5(ring) 74.29 6(ring) 72.90 7(ring) 74.27 8(ring) 74.83

*Weight %

a) c)

b) d)

Figure 5 Iron element contents in the cross-sectional area of the particle by EDS

CONCLUSIONS

The individual particle reduction behaviour was studied in the high temperature drop tube furnace. Through the analysis of chemical titration and optical microscope, the following conclusions are obtained.

• The PCR has significant influence on the reduction degree of the very fine iron ore. The reduction degree increases with the decrease of PCR.

• The reduction from hematite to magnetite takes place quickly in the first 200 ms. Some microspores are formed due to the crystal lattice reconstruction. However, as the increase of dense wusitte formation, the micropores decrease gradually.

• Through the morphology study, the reduction from magnetite to wüstite takes place at the shrinking core interface.

REFERENCE:

[1] M. Bahgat: Materials Letters, 61 (2007), 339-342.

[2] B. Weiss; J. Sturn, S. Voglsam, S. Strobl: Ironmaking and Steelmaking, 38 (2011), 65-73.

Page 72: 2-page abstracts booklet

Control Technique of Material Discharge Behavior on Center

Feed Type Top Bunker

Y. Kashihara, A. Murao, Y. Sawa, M. Sato, K. Yamamoto

(JFE Steel Corporation)

INTRODUCTION It is an important issue to decrease CO2 emission from steel industry. Low RAR (Reducing Agent Rate) operation of blast furnace is one of the effective measures to decrease CO2 emission. In order to achieve low RAR operation of blast furnace, development of burden distribution control technique was carried out with the aim of increasing gas utilization and decreasing heat loss. In this technique, it is important to control particle size distribution discharged from top bunker1). In past study, it was investigated to control particle size distribution discharged from the parallel type top bunker2). And, by improvement of discharged particle size distribution, it was achieved improvement of permeability and increase of gas utilization. In this study, it was investigated about particle size behavior discharged from the center feed type top bunker by scale model experiment. And it was examined about effect of particle size distribution discharged from the top bunker on blast furnace operation by using a two-dimensional mathematical simulation model3). EXPERIMENTAL CONDITIONS Scale model experiment was carried out to investigate effect of segregation in the top bunker on particle size distribution discharged from the top bunker. Figure 1 shows experimental apparatus. The experimental apparatus is a 1/18.8 scale model of Keihin No.2 blast furnace, which has a bell-less type charging system with center feed type top bunker. The scale model consists of an ore bin, a coke bin, a surge hopper and belt conveyers to recreate the charging system of the actual blast furnace. The experimental conditions such as particle size of burden materials and rotating speed of rotating chute were decided based on the scale factor of the experimental apparatus. The Froude number, which is the ratio of inertia to gravity, was set for the charging burden materials and was matched with that of actual blast furnace. Figure 2 shows schematic illustrations of segregation behavior of particle by shape of raw materials heap in

Upper bunker

Lower bunker

Surge hopperOre bin Coke bin

Belt conveyerBelt conveyer

Model furnace

Rotating chute

Fig.1. Experimental apparatus.

lower bunker. In this experiment, raw materials were charged in the lower bunker as changing the shape of the raw materials heap as shown in Fig. 2. Base is the condition that the shape of raw materials is flat, Case 1 is the condition that the height of raw materials heap at central part was the highest (convex shape) and Case 2 is the condition that the height of raw materials heap at peripheral part was the highest (reentrant shape). Larger particles were segregated to the peripheral part in the lower bunker in case of convex shape, and it was segregated to the central part in the lower bunker in case of reentrant shape. In this experiment, raw materials discharged from top bunker were collected in a series of boxes moving on the belt conveyer to measure the change in the raw materials diameter.

Base:Flat shape

Case1:Convex shape

Case2:Reentrant shape

Furnace top

Upper bunkerRotating chute

Charging BC

No segregation

Segregation of large particles

Lower bunker

Fig.2. Schematic illustrations of shape of raw

materials heap in lower bunker. EXPERIMENTAL RESULT Figure 3 shows the change in the relative particle size discharged from the top bunker. In case of Base condition, the relative particle size at the beginning and middle of discharging was large, and the relative particle size at the end of discharging was small. In case of Case1, relative particle size gradually increased during discharging. And in case of Case2,

Page 73: 2-page abstracts booklet

relative particle size gradually decreased during discharging.

0.8

0.9

1.0

1.1

1.2

0.0 0.5 1.0Discharged weight ratio (-)

Rel

ativ

e pa

rticl

e si

ze (

-) BaseCase1Case2

BaseCase1Case2

Fig.3. Change in relative particle size discharged from

top bunker. Figure 4 shows relative particle size distribution of the raw materials charged in the model furnace. In these cases, charging method was changed as larger particles was charged in the central part of the model furnace. In case of Case1, it was charged by conventional tilting, and in case of Base and Case2, it was charged by reverse tilting. In Case1 and Case2, particle size in the central part of the model furnace was larger than particle size in the central part of the model furnace in Base condition. As a result, by controlling the shape of raw materials heap in the lower bunker and changing to the suitable charging method, it is expected that central gas flow volume increases and permeability in the blast furnace is improved.

0.7

0.8

0.9

1.0

1.1

1.2

1.3

0.0 0.2 0.4 0.6 0.8 1.0r/R (-)

Rel

ativ

e pa

rticl

e si

ze (-

)

Case2Case1Base

Case2Case1Base

Fig.4. Relative particle size distribution of raw

materials charged in model furnace. SIMULATION RESULT To examine the effect of the particle size distribution at the top of blast furnace after charging raw materials on blast furnace operation, a two-dimensional mathematical simulation model was used. In this simulation, inner volume of blast furnace is 5000m3. In this study, to estimate the change in particle size distribution at the top of the blast furnace, blast conditions are constant in the all conditions. Figure 5 shows calculation result of total pressure drop in the blast furnace. Total pressure drop of Case1 (convex shape and conventinal tilting) and Case2 (reentrant shape and reverse tilting) decreased from Base (flat shape and reverse tilting). It is due to

increase in central gas flow volume by increase in particle size in the central part.

113

114

115

116

Pre

ssur

e dr

op (k

Pa)

Base Case1 Case2 Fig.5. Calculation result of total pressure drop.

Figure 6 shows calculation result of gas utilization of the blast furnace. In the calculation of Case1 and Case2, it was calculated as conditions that the total pressure drop is equal to that in the Base by increase in ratio of ore to coke (O/C). Gas utilization of Case1 and Case2 increased by 0.2% from Base. Thus, decrease in RAR can be expected by increase in O/C, utilizing the increment of permeability improvement resulting from particle size distribution at the top of the blast furnace.

46.9

47.0

47.1

47.2

Base Case1 Case2

ηco

(%)

47.3

Fig.6. Calculation result of gas utilization.

CONCLUSIONS To investigate effect of particle size distribution discharged from top bunker, scale model experiment was carried out. And calculation by using a two-dimensional mathematical simulation model was carried out based on the experimental results. The following conclusions were obtained. (1) Particle size distribution discharged from the top bunker could be controlled by controlling the shape of raw materials heap in the lower bunker. (2) Permeability in the blast furnace was improved by controlling the particle size distribution discharged from the top bunker and changing to the suitable charging method. (3) Increase of gas utilization was expected by increase in O/C utilizing permeability improved by change in particle size distribution at the top of the blast furnace. REFERENCES 1) S. Miyagawa et al: Kawasaki Steel Giho, 23 (1991), 130. 2) T. Sato et al: Tetsu-to-Hagane, 86 (2000), 648. 3) T. Sato et al: Kawasaki Steel Technical Report, 38 (1998), 24.

Page 74: 2-page abstracts booklet

Logistic model of hot metal distribution by torpedo ladles at

ROGESA in Germany

H. Rausch , R. Lin (AG der Dillinger Hüttenwerke)

Intruduction ROGESA, a blast furnace plant located in Dillingen in Germany, is a joint venture of the two steel producers Dillinger Hütte in Dillingen and Saarstahl in Völkingen. The hot metal is produced by two blast furnaces in Dillingen and has to be distributed in equal parts to the steel shops at two locations. Two sizes of torpedo ladles are used for hot metal transportation. In order to cope with such logistic challenge, a simulation model was developed. Model target was the quantification of the type and the number of torpedoes required for various production situations in order to ensure an undisturbed process. Moreover, the needs for future production in the blast furnaces and the steel works were simulated and quantified. 1. The production plants Two blast furnaces in Dillingen supply both the steel plant in Dillingen and the steel plant in Völklingen, which is about 40 km remote. This is done by torpedo ladles of different filling capacities. Figure 1 shows a survey of production plant location including railway connection for torpedo circulation.

Figure 1: Sketch of the production plants in Dillingen together with torpedo circulation

It turned out that under current production conditions, especially inhomogeneous or irregular production, the number of active torpedo ladles was not sufficient. As the problem to determine a suitable amount of active torpedoes for different production conditions is nontrivial, a model was established to answer that question. 2. The model In a first step of model construction the positioning of blast furnaces and steel plants as well as the transport connections (railways) was mapped on an array structure that is suitable for computer handling. Second the torpedoes were inserted in this structure by extending the array to a matrix. By that construction each matrix elements finally represents one torpedo. Now the model starts with randomly distributed torpedoes on the two blast furnaces in Dillingen as well as the steel plants in Dillingen and Völklingen. In time steps of one minute the torpedoes do their foreseen job, i.e. at the BF they are filled by corresponding amount of hot metal or simply wait; torpedos on their way to steel plant move accordingly forward and torpedos at the steel plant deliver a corresponding amount of hot metal. In the course of time the whole ladle configuration moves in that manner. In practice it is mandatory that for security reasons minimum one torpedo is positioned per blast furnace. So to be even a little bit more secure, the model was defined to stop when a situation occurred that only one torpedo was placed at any of the blast furnaces. Additionally the model was stopped when no more torpedo was situated at the steel plant in Dillingen because of a succeeding enforced production stop in the steel shop. 3. The production A first calculation was performed with the actual production conditions. Table 1 gives a survey of the BF and steel production conditions.

Hot metal productionBF4 BF5 ∑ BF

6120 t/d 7020 t/d 13140 t/d 4,68 Mio t/a

Steel productionProduction conditions

In DillingenProduction inDillingen [t/d]

Production inVölklingen [t/d]

1-converter 5360 77802-converter

1: 44/44/44 (homogeneous)2:44/41/47 (normal)3 36/48/48 (inhomogeneous)

6900 6240

2-converter

4 36/44/44 (irregular) 6482 6658

Table 1: Actual BF and steel plant production

Page 75: 2-page abstracts booklet

In the simulation the hot metal production is not changed. The situation of the steel plant in Dillingen is considered more differentiated: The steel plant in Dillingen is equipped with only two converters, in 75 % of time the production is achieved by two converters, 25 % of time is produced with only one converter while the other is in relining. Moreover the daily steel plant producing rates vary depending on e.g. the steel quality produced. The daily variation is given in terms of charges variation: e.g. case 1:44/44/44 marks a continuous production with 44 heats/d constantly over time, whereas e.g. 3:36/48/48 means an inhomogeneous production of 36 heats followed by two days of 48 heats. Finally an irregularity in the steel plant has to be considered (4:36/44/44) with a lack of four heats the 2nd and 3rd day of production compared to case 3. 4. Simulation results For the simulation two types of torpedoes with different filling capacity were used, 260 t for the DH torpedoes (circulate only within DH works) and 160 t for the VK torpedoes (transport the hot metal to the remote Völklingen steel plant by using public railway network). Figure 2 shows the result for the case of homogeneous production in the Dillingen steel plant: minimum 10 DH-torpedoes and 18 VK-torpedoes are needed; alternatively it also works with 8 DH-torpedoes and 19 VK-torpedoes. For fewer then 8 Dillinger and 21 VK-torpedoes the circulation stops at the blast furnaces. For fewer then 8 Dillinger and more or equal 22 VK torpedoes the circulation stops due to lack of torpedoes at the Dillinger steel plant.

5

6

7

8

9

10

11

12

13

18 19 20 21 22 23 24 25 26VK-Torpedos [-]

DH

-Tor

pedo

s [-]

1:44/44/44

stop due to lack of torpedos at the Dillinger steel plant

successful torpedo circulation

stop due tolack of torpedos

at the blast furnaces

Figure 2: Minimum number of torpedoes needed for current homogeneous DH steel production Similar to Figure 2 all the simulation results are plotted for different steel plant production conditions (Figure 3): it is obvious that the situation gets worse for inhomogeneous (case 3:36/48/48) and even worser for irregular production (case 4:36/44/44). In the case of one-converter production in Dillingen, even

minimum 23 VK torpedoes for successful torpedo circulation are needed.

5

6

7

8

9

10

11

12

13

18 19 20 21 22 23 24 25 26VK-Torpedos [-]

DH

-Tor

pedo

s [-] 1:44/44/44

2:44/41/473:36/48/484:36/44/441-Konverter

Figure 3: Minimum number of torpedoes needed for current non-homogeneous DH steel production A second investigation concerned one possible production option for the future. The simulation result with the minimum number of necessary torpedoes in that case is given in Figure 4:

5

6

7

8

9

10

11

12

13

18 19 20 21 22 23 24 25 26

VK-Torpedos [-]

DH

-Tor

pedo

s [-] 1:45/45/45

2:45/42/483:36/49/494:36/45/451-Konverter

Figure 4: Minimum number of torpedoes needed for possible future production 5. Conclusions The circulation of torpedo ladles was simulated with a model developed in Dillingen. The minimum number of torpedoes that are needed for an undisturbed circulation under current and possible future production conditions could be quantified. This study delivers a strong support for optimal usage and maintenance schedule of torpedo ladles.

Page 76: 2-page abstracts booklet

World´s first Laser-Profile-Measurement-System for the

Refractory Lining of hot Torpedo-Ladles

Rolf Lamm (Minteq International GmbH-Ferrotron Division, Duisburg, Germany)

ABSTRACT

Torpedo ladles are used to transport liquid iron from a blast furnace to the steel plant via rail. The Torpedo measuring system has an innovative, yet simple and rugged design that allows immersion of a laser head into a hot torpedo ladle with surrounding temperatures of more than 1.150 °C. The system’s laser-beam rapidly scans the lining thickness of the entire surface, collecting millions of data points that are generated in a wide range of computer displays from simple tabular reporting to a virtual walk-through of configurable 3D images. This new development allows steel makers to measure refractory-lining thickness in hot torpedo ladle cars in less than three minutes and improves safety, increases ladle availability and capacity, extends refractory life and cost savings in energy, material and the maintenance of hot torpedo ladles.

INTRODUCTION

High speed laser scanners become more and more important for determination of the brick thickness of converter vessels and steel ladles. The laser measuring units are used as mobile measuring units or fixed installed systems worldwide. Besides economic aspects for the use of laser scanners, the increased safety of the aggregates by avoiding of dangerous break-through are important criterions as they have top-ranking significance for pig-iron transport from the blast furnace to the steel making plant. An outage of one torpedo ladle already results in severe disturbance of the production process.

Ferrotron, a division of Minteq International GmbH, introduced the newly developed laser measuring unit LaCam®-Torpedo, which for the first time enables the laser measurement of hot torpedo ladles from inside the torpedo ladle.

TODAYS PRACTICE

Today most of the steel-plants are doing a “cold inspection” of their torpedo ladles. That means after a certain lifetime or number of “heats” the torpedo ladle will go to an inspection stand where it cools down up to three days. An inspector will climb into the cold torpedo ladle and does a manually measurement of the brick-thickness with a ruler to decide if it is necessary to repair the torpedo ladle, replace the entire lining of the torpedo ladle or just put the torpedo

ladle back in the production cycle. After this break, which can take up to seven days, the torpedo ladle is ready again for further transport of pig iron.

Figure 1. Set up of LaCam® Torpedo during laser measurement

NEW METHOD

Doing regular measurements in hot conditions, methodical cold inspections can be reduced and four to five days availability of the torpedo ladle can be attained. Furthermore, energy costs can be saved and emissions reduced. The measurement in hot condition was the target of the introduction of the new LaCam®-Torpedo technology.

LaCam® - LASERSCAN-TECHNOLOGY

The LaCam® -profile measuring system has been developed for non-contact measurement of hot refractory linings in metallurgical reaction and transport vessels. Rapid scanning (135.000 measurements /sec.) of the object is possible via a pulsed laser beam which is deflected by a rotating mirror system. Thus a three dimensional frame of the vessel´s inner surface is created within a few seconds.

Operational application

The first set up was installed in an European steel-plant with an annual production of pig iron around 11 million tons. The plant uses 73 torpedo for daily operation. The average charging weight of the torpedo ladle is 270 tons. The system was constructed where the torpedo ladle cars stop to be cleaned (Figure 1).

The system consists of a 3-D laser profile measurement- head mounted on top of a cooled movable boom, a cooling system, automated mechanical manipulator and the determining and evaluation industrial PC station. The easy but sturdy construction and the fast measurement time enable

Page 77: 2-page abstracts booklet

Additionally, the laser measurement enables the determination of the ladle volume so that plants using rail-car scales at the tapping position of the blast furnace can fill the torpedo ladle at an optimum knowing the bath-level. (Figure 4),

the laser head to be immersed into the hot torpedo ladle with ambient temperatures of more than 1.150 °C without getting damaged. The entire measurement takes less than 3 minutes and more than 3.9 million points with accuracy better than 5 mm are created in the torpedo ladle scan. . Evaluation and presentation of the results

Figure 4. Indication of bath level in brick thickness presentation

The evaluation possibilities allow a wide choice on presentation alternatives from tabular reports to virtual walk-throughs by means of configurable 3D-images.The measurement results are presented on a Graphical User Interface GUI and can be documented in various ways. (Figure 2)

RESULTS AND CONCLUSIONS At the steel-plant where the first LaCam® Torpedo installation is installed this major observation were made:

Increased Safety: Safety will increase significantly. The risk of break-through on public rail ways or important locations that could stop the whole steelworks or blast furnace and would lead to dramatic incidents can be reduced.

Figure 2. Graphical User Interface – GUI, shows different presentations of the measuring results Increase of availability: Discontinuation of 30% of

cold inspections will increase the charging capacity to 62% of one torpedo ladle campaign.

A 3-D scatterplot is created, which describes the entire surface of the refractory lining. If this measured surface is compared to the former measured safety lining (reference), the current thickness of the wear lining is maintained. By means of importing former wear measurements, tendencies and trend lines of the refractory lining can be seen and graphically presented. Areas of Interests can be zoomed in on and presented vividly within the 3-D presentation. (Figure 3)

Cost Savings in Energy-/Material-Maintenance: Discontinuation of cold inspections will save enormous amount of energy costs.

Extended Refractory Lifetime: An increase of 7% of refractory lifetime gains the throughput of iron, which is equal to 3.5 ladle linings per year.

Downsizing of ladle fleet: Increase of availability allows reduction of the number of torpedo ladles. Thus the maintenance cost for the torpedo ladles will go down.

The economic benefits of such a measuring system can be easily achieved by the regular measurement of hot torpedo ladles, resulting in raised efficiency, torpedo fleet reduction and increased production volume. Even if the safety aspect, which is difficult to define in economic figures, is not considered, and the lifetime-increase of the refractory lining is implemented with a low percentage, energy savings, reduction of maintenance costs as well as the increased availability result in a very short payback period.

Figure 3. Examples of 3D evaluation pictures colors represent refractory lining thickness

Page 78: 2-page abstracts booklet

Optimised operations to improve slag skimming of hot metal

desulphurisation slag G.Parker, A. Ferguson and H. Thomson

Tata Steel, Long Products Business, Scunthorpe, North Lincolnshire, UK.

ABSTRACT

In difficult economic times more focus is applied to control of costs and efficiency, rather than absolute output.

With requirements to reduce costs, increase rate of operation and improve efficiency ever increasing, a range of initiatives to help minimise the levels of metal loss from desulphurisation slag skimming at our lime/magnesium co-injection station have been studied and adopted.

Multiple factors combine in the hot metal desulphurisation process to give the slag skimming efficiency. Several studies and streams of work were carried out to successfully improve the characteristics of the slag resulting from desulphurisation: (1) Steps were taken to enhance hot metal temperature, through study of torpedo car and ladle logistics, refractory systems and plant operations; (2) Focus was placed on optimising the desulphurisation injection system to minimise the required reagent for sulphur removal by adapting model inputs and injection rates; (3) Slag viscosity has been adjusted to reduce direct skim losses and minimise slag metallisation by commissioning a system to dispense recycled slag modifying agents. Flexible additions levels have been modelled to maintain skimming operations and alterations in operators skimming techniques have aided reducing the level of losses across the range of hot metal chemistry and steel grades required.

The combined practices have yielded significant reductions in the losses associated with the hot metal skimming operations and increases in productivity.

PRODUCTION CHANGES

In September 2011 the site moved to lower output, using a two blast furnace operation. Focus switched to manufacturing a higher proportion of high specification steels, such as quench and temper plate, rails, tyre cord and spring steels.

Steel plant operations also adapted to the changes, closing billet and large bloom casting facilities to

improve efficiency and reduce costs, focussing on three casting machines, two six strand bloom casters and a twin strand slab machine.

BLAST FURNACE AND TORPEDO OPERATIONS

The output changes required analysis of resources to minimise costs and if possible improve thermal state.

With the drop in total hot metal output from 3.5Mt to 2.8Mt, alterations to the total number of operational torpedo cars was made.

To improve flow through the whole site, blast furnace tapping rates and steel plant output became more aligned, to minimise hot metal stock, but also allow for periods with high rate steel plant output.

With the reduced number of torpedoes available at any one time, a torpedo tracking system, linking torpedoes to particular site zones is used. Plant operations are then aware of full casts arriving and empty torpedo positions to ensure they are available in the right place at the right time (see Figure 1).

Figure 1. Section of Torpedo Tracking Screen.

To ensure a greater understanding of where the temperature losses are during torpedo operations a torpedo was instrumented with thermocouples and a data logger during reline. Thermocouples 1-6 were positioned through existing breather holes between safety lining bricks, just behind the interface with the working lining and 7-10 drilled into the working torpedo shell. A mirror image set were installed on the opposite side (11-20) (Figure 2).

Even though there was the obvious time lag between the temperature measured at the thermocouples and the working lining the data indicated that during operations the refractory system was relatively stable when full of iron, but on emptying, the loss of heat was much more rapid than expected and emphasised the requirement for rapid return for refilling or improved preheating of the torpedo.

Without this rapid operation it can take several hours full of iron to stop the reduction in temperature within the brickwork (Figure 3).

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Analysis of historic data showed that in a number of areas the control model over-predicted for the aim sulphur level. Also, at low sulphur aims, around 0.002%, laboratory analysis rounding prevented the aim from being met. This sometimes meant that operator adjustments were increasing the usage of reagent unnecessarily. Adjustments in the model and operator displays resulted in a reduction in consumption of around 12-15% across the range of sulphur aims, with no detriment to the steel sulphur.

DESULPHURISATION SLAG SKIMMING Figure 2. Position of thermocouples in torpedo.

Due to excess metal loss on slag skimming, generally attributed to low hot metal temperature (<1300oC) and low sulphur aims, trials with a recycled material added directly to the ladle, to aid slag fluidisation were successful. The fluidising agent is a SiO2-CaO-Na2O material with a low melting point and is able to lower the basicity (%SiO2-%CaO) and MgO content in the desulphurisation slag. The addition of agent was successfully implemented with a silo system, with ability to flex addition timing and level into the hot metal ladle.

Losses from skimming have been improved in two ways, a reduction in the metallic fraction contained with the slag and from direct molten metal loss. The metal content in the skimmed slag has been reduced from around 75% to less than 30%, and the direct metal loss by around 35-45% (Figure 5).

Figure 3. Example of torpedo thermocouple trace.

With the improvements in tracking and scheduling of the torpedoes and improved understanding of the refractory heat losses a discernable 10-12oC improvement in hot metal temperature has been observed (Figure 4).

Tata Scunthorpe - Skim Iron Index - Weekly Average - Jun 2011 - Oct 2012

45

55

65

75

85

95

105

115

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135

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30/5/11 9/7/11 18/8/11 27/9/11 6/11/11 16/12/11 25/1/12 5/3/12 14/4/12 24/5/12 3/7/12 12/8/12 21/9/12 31/10/12

Iron

Skim

Inde

x (%

)

Installation of Silo for Additions of Slag Fluidiser

Tata Scunthorpe Hot Metal Pour Temperature - Weekly Average - Sept 2011 - Oct 2012

1310

1320

1330

1340

1350

1360

1370

30/09/11 30/10/11 29/11/11 29/12/11 28/01/12 27/02/12 28/03/12 27/04/12 27/05/12 26/06/12 26/07/12 25/08/12 24/09/12

Hot

Met

al T

empe

ratu

re (D

egre

es C

)

Figure 5. Skim loss from Hot Metal Ladle.

CONCLUSIONS

The focus on hot metal operations has yielded significant improvements in understanding of temperature losses across the steelworks. This has improved temperature, aided desulphurisation efficiency and the installation of a slag fluidising agent has greatly reduced the metal losses from the hot metal ladle.

Figure 4. Initial Hot Metal pour temperature.

DESULPHURISATION OPTIMISATION

To aid desulphurisation slag skimming, operations at the CaO/Mg co-injection station were also analysed for any improvement to reduce time, temperature loss and reagent consumption.

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Session 6: Continuous casting

Table of Contents

6.1 World first wide thick amorphous alloy coils production by using a newly ultra rapid cooling transit controlled large-scale thermal spraying gun J. TAKEHARA, T. MIMURA, Y. FUKUDOME, H. MATSUMOTO, R. KURAHASHI (Nakayama Steel Works), M. KIUCHI (University of Tokyo), Japan

6.2 Electromagnetic mold level measurement on bloom continuous casting machines equipped with electromagnetic mold stirrer J. ROHÁČ, A. PAWLIK (VÚHŽ a.s.), Czech Republic, J.E. ERIKSSON (ABB AB Process Automation), Sweden, D.A. DOMANSKI (ABB Inc.), Canada, K. VÄLIMAA (Ovako Imatra Oy), Finland, D. BOCEK, J. CUPEK (Třinecké železárny), Czech Republic

6.3

Why oxides intensify spray cooling? M. RAUDENSKY, M. HNIZDIL, P. KOTRBACEK (Brno University of Technology), Czech Republic

6.4

Increasing the productivity of the vertical continuous casting machine at Hagondange Plant J. DEMURGER, J. GREMILLET, M. MATTEI, M. STILGENBAUER, V. SEEMANN, G. BOI, P. GIBONDI (Ascométal), France

6.5

The new generation of Danieli thin slab casting and rolling plants: lay out concepts breaking all actual parameters in CAPEX and OPEX for advanced markets and product mix C. PIEMONTE, A. PIGANI (Danieli & C Spa), Italy

6.6

Arvedi ESP - Three years of successful operation A. JUNGBAUER, G. WERSHING, G. WINDNER, A. BUMBERGER (Siemens VAI Metals Technologies GmbH), Austria

6.7

CSP® flex - New CSP® concepts for future market requirements C. KLEIN, C. BILGEN, C. KLINKENBERG, J. MÜLLER (SMS Siemag AG), Germany

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World first wide thick amorphous alloy coils production using by a newly ultra rapid cooling transit controlled large-scale thermal

spraying gun TAKEHARA Junji (Nakayama Steel Works)

MIMURA Tsunehiro (Nakayama Steel Works) FUKUDOME Yoshihisa (Nakayama Steel Works) MATSUMOTO Hiroshi (Nakayama Steel Works) KURAHASHI Ryuro (Nakayama Steel Works)

KIUCHI Manabu (Kiuchi Laboratory)

1. INTRODUCTION Amorphous alloys have higher tensile strength,

better anticorrosion and easier soft-magnetism. As conventional amorphous alloy strips are produced mainly by the single rolling method or the twin rolling method, their thickness is less than 100 microns and width is less than 200 mm. Thus, they have never been widely used in industrial products. NAKAYAMA STEEL WORKS has already advanced

the development of amorphous-alloy-film processing technique using the thermal-spraying method[1]. In succession, ultra rapid cooling transit controlled large-scale thermal spraying gun was newly developed. Then, over 300 microns thick and 300 mm wide amorphous alloy strips were produced at the world first. 2. DEVELOPMENT TECHNIQUE AND ITS PERFORMANCE 2.1 Concept of ultra rapid cooling transit controlled large-scale thermal spraying gun Fig. 1 shows a schematic view of the thermal-spray

system with a water vapor cooling unit used for this development. Fig.1 Schematic illustration of ultra rapid cooling

transit controlled large-scale thermal spraying gun.

Oxygen and propane gas were mixed with the alloy powder in the gun before combustion and ejection from the gun, after which the melted powder rapidly cooled to become an amorphous alloys owing to the nitrogen and water vapor outside gun. The alloy

powder was uniformly sprayed onto the substrate in the width direction. A reducing atmosphere was used to control the oxygen to propane gas ratio, and thus prevent the generation of oxides. Fig.2 shows measured cooling rate using water vapor. Cooling rate was more than 1 million °C/s. Fig.2 Measured cooling rate of ultra rapid cooling transit controlled large-scale thermal spraying gun with a water vapor. 2.2 Amorphous alloy strip production line On the acid and lever preheating steel substrate in about 300 °C, alloy powder was thermally sprayed and became amorphous alloy films. Then, immediately they were rolled to diminish holes and smooth surface by a single roll driven mill. Fig.3 shows construction of amorphous alloy strip production line. Fig.3 Illustration of amorphous alloy production line. Sprayed amorphous alloy and steel substrate should adhere during rolling. On the other, after rolling, they should be separated smoothly. When amorphous alloy was not stick on the substrate, substrate surface initially was grinded to 5 microns roughness. While, amorphous alloy and substrate were well adhere, exfoliation powder was initially sprayed before thermal spraying. 3. EXPERENCE RESULT OF AMORPHOUS ALLOY Ni-base alloy (Ni65-Cr15-P16-B4-C %Atom) was

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used. This alloy has both anticorrosionability and conductivity owing to its passivation layer and carbon additon. Fig. 4 shows appearance of wide amorphous alloy coils. Its width was over 300 mm.

Fig.4 Appearance of Ni-based amorphous alloy coil. The result of X-ray diffraction measurement of the

amorphous-alloy film and optical image were shown at Fig. 5. A clear halo peak is observed by that measurement and no hole and crack is confirmed by the metallographic micrograph. Fig.5 Optical image and X ray diffraction analysis of

Ni-based amorphous alloy strip. Sulfuric acid immersion test result was good to

indicate high corrosion resistance of the film owing to passivation layer as shown in Fig.6. Also contact resistance was lower to indicate good conductivity owing to its carbon addition as shown in Fig.7. Figure 8 shows a separator for fuel cell, which was warmly pressed from Ni65-Cr-15-P16-B4-C amorphous alloy strip. Our amorphous alloy coils production by a newly ultra rapid cooling transit controlled large-scale thermal spraying gun is very efficient and fit to industrially production. Thus, it will cost one-tenth to produce fuel cell separator than conventional one. 5. Conclusion Nakayama steel works produced world first 300 micron thickness, 300 mm width and 5 m length

amorphous coils using a newly developed ultra rapid cooling transit large-scale thermal spraying gun.

0

50

100

150

0 100 200 300 400

Immersion time,t /hr

Cor

rosi

on s

peed

, c/μ

m/y

ear

Passivation layer occur

Sulfuric acidpH=3, 80 ℃

100 Fig.6 Corrosion speed of amorphous alloy strip

owing to its passivation layer. Fig.7 Conductivity of Ni65-Cr15-P16-B4-C %Atom

amorphous alloy strip. Fig.8 Separator for fuel cell made from Ni65-Cr15-

P16-B4-C %Atom amorphous alloy strip. Acknowledgements This work was carried out as an innovation promotion program. Financial support from NEDO (New Energy and Industrial Technology Development) is gratefully acknowledged. Reference [1] R.Kurahashi,M.Komaki,N.Nagao,K.Hakomori,M Kozaki,A.Yanagitani,Revue de Metallurgie 105 (2008) 575-583

mm100mm

0

100

200

300

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500

0 2 4 6 8

Contact pressure,P /kgf/cm2

Con

tact

resi

stan

ce, R

s/mΩ

No carbonCarbon addition

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Electromagnetic Mold Level Measurement on Bloom

Continuous Casting Machines Equipped with Electromagnetic

Mold Stirrer

J. Rohac (VUHZ Dobra)

A. Pawlik (VUHZ Dobra)

J.E. Eriksson (ABB Västerås)

D.A. Domanski (ABB Whitby)

K. Välimaa, (Ovako Imatra)

D. Bocek (Třinecké železárny Třinec)

J. Cupek (Třinecké železárny Trinec)

ABSTRACT The paper describes solutions how to assure the mold level control on the continuous casting machine (CCM) equipped with edge type of electromagnetic mold level measurement under the influence of the mold electromagnetic stirrer (MEMS). The description of realizations in two steelworks is presented including the discussion of the results from metallurgical point of view. BACKGROUND OF ELECTROMAGNETIC MOLD LEVEL MEASUREMENT AND MOLD ELECTROMAGNETIC STIRRER COEXISTENCE AND TECHNIQUES FOR SOLVING OF ISSUES They could occur following issues while the electromagnetic mold level measurement is used together with MEMS: 1) Interference by the noise in the range of working frequency of level measurement 2) Interference by harmonics of stirring frequency 3) Offset (shift) of level signal 1) Noise The noise is caused by direct penetration of the interfering voltages with frequencies close to the working frequency of the mold level measuring system - the working frequency of edge types of level sensor is around 1 kHz to enable the penetration of sensor electromagnetic field through the metal body of the sensor. Source of this interference is the power source – inverter providing the power for the MEMS. Some types of inverters produce very low noise that

has practically no harmful influence on the level signal, but other types generate wideband noise which could occur at the level output signal. Following technique are used for elimination of extra noise in level signal: - Increasing of level sensor excitation and improvement of immunity of electronic part of the level measuring system to the noise out of the measuring system working frequency band (applied in the VUHZ new level measuring system; approx. twice lower noise in comparison with the old one). - Suitable philosophy of switching of power transistors in MEMS inverter (applied by ABB in Ovako Imatra; noise suppressed approx. three times). - Suitable arrangement of the MEMS coils with shielding (a method patented by ABB; applied in Trinecke Zelezarny; noise suppressed approx. three times). - Insertion of passive LC (chokes-capacitors) filter between the inverter and MEMS coils (filter designed and manufactured by VUHZ and applied in Ovako Imatra; noise suppressed approx. ten times).

Fig. 1. Comparison of level signal at Ovako Imatra 2) Harmonics and 3) Offset Both issues 2) and 3) are the result of interaction between the MEMS electromagnetic field and mold level sensor field in ferromagnetic areas near the mold level sensor. Due to a non-linear magnetization curve of ferromagnetic particles in these areas: - New fields are generated with frequencies equal to combination of frequencies of the sensor and MEMS and the mold level signal is jammed by even multiples of MEMS frequency (issue 2), - Distribution of the sensor field is modified by MEMS field which causes the shift of level signal (issue 3). It is obvious that the magnitude of unwanted harmonics in the level signal and the extent of signal offset depend especially on volume of ferromagnetic areas in the sensor vicinity and the magnetic properties of these areas. Magnetic properties are

Page 84: 2-page abstracts booklet

determined by chemical composition and mechanical stress in ferromagnetic materials. It means in practice that the extent of MEMS influence depends on thickness and chemical composition of ferromagnetic coating of the mold plate below the sensor, because the water cooling jacket is made of nonmagnetic steel while MEMS in used.

INSTALLATION OF MOLD STIRRER AT TRINECKE ZELEZARNY The round blooms diameters 320 mm, 410 mm and 525 mm are produced at Trinecke Zelezarny. To improve the internal quality of blooms round 525 mm the ABB MEMS was installed in the molds equipped with VUHZ electromagnetic mold level measuring system. The basic evaluated parameter was size of equiaxed crystals area on Baumann prints, mainly for medium alloyed steel (Cr-Ni-Mo). The area of equiaxed crystals significantly increased while MEMS was used (Fig. 3).

Special extremely narrow and precisely tuned “comb” filter embedded in the electronic part of VUHZ mold level measuring system suppresses the harmonics at Ovako Imatra only. No special technique is necessary to be used for offset suppression in both installations because no ferromagnetic coating of the top part of the mold is used and the offset is invisible. However the mold level detector evaluation unit is ready for offset suppression if needed.

INSTALLATION OF ELECTROMAGNETIC MOLD LEVEL MEASUREMENT AT OVAKO IMATRA At Ovako Imatra there has been a long-standing interest in improving the mold level control. Excessive meniscus level fluctuation is one source for exogenous inclusions found in steel, and is also a possible cause for surface defects in the blooms. Today, also the customers place increasingly strict demands for the mold level control.

Fig. 3. Comparison between stirred and no stirred steel 34CrNiMo6. There are no equiaxed crystals when the bloom is cast without MEMS. Reduction of central segregations without degradation of micro purity was obtained as well. Evaluation is shown in Fig. 4. The electromagnetic mold level measurement was

installed already in 2003, but the interference caused by MEMS prevented its use in mold level control. A solution for decreasing the interference was found in cooperation between VUHZ, ABB and Ovako.

In 2012 the updated electromagnetic mold measurement system was commissioned and adopted into the mold level control loop with good results (Fig. 2).

30

40

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60

70

80

90

0 1 2 3 4 5

Mol

d le

vel [

mm

]

Time [min]6

radiometric (control loop) electromagnetic (measurement)electromagnetic (control loop)

±1.1mm (3σ-sigma)±5.8mm (3σ-sigma)

±6.1mm (3σ-sigma)

Mold powder additions

Fig. 4. C segregation. Comparison between stirred and no stirred steel 42CrMo4. According to suitable result with format diameter 525 mm with MEMS CCM was equipped with MEMS also for format dia 410 mm. RESUME Unfortunately there is no universal solution to ensure the trouble-free coexistence of the edge type of electromagnetic mold level detector and MEMS. The paper shows two solutions of it as the result of cooperation among all participants - the end-user, the MEMS manufacturer and the mold level measuring system manufacturer.

Fig. 2. A Comparison between radiometric and electromagnetic measurement. Mold level deviation was reduced with electromagnetic mold level measurement.

Page 85: 2-page abstracts booklet

Why oxides intensify spray cooling

M. Raudensky, M. Hnizdil, P. Kotrbacek

(Brno University of Technology)

EXPERIMENTAL EVIDENCE

Introduction

Oxides layer at steel surface has much lower thermal conductivity (0.1-3 W/mK) than is conductivity of steel (15-60 W/mK). In addition the contact between basic steel material and oxide layer may not be perfect (see Fig. 1). Physically, from the point of heat transfer, can be scale considered as thermal resistance layer.

Description of 1st experiment

Austenitic steel plate size 300x300 mm covered by about 60 µm layer of oxides was heated to 800 °C and then sprayed by water nozzle. From the recorded temperatures was computed the heat transfer coefficient (HTC) as a function of surface temperature [1], [2]. The result is shown in Fig. 3, line O1.

64.5 µm Fig. 1 Layer of porous oxides on austenitic steel (one hour of oxidation in air at temperature 1000 °C), light grey - steel, dark grey - oxides

The used test plate was then mechanically brushed. The surface after cleaning by steel brush was shiny but the microscope analysis showed that on the steel surface remained in average 20-30 µm layer of sticky scale (see Fig. 2). The plate was then heated in protective atmosphere to 800°C. The experiment was repeated several times. The results are shown in Fig. 3 and marked as OP2 to OP5. The results show that the cooling intensity with thick oxide layer is higher than with thin layer.

31.4 µm

19.7 µm

Fig. 2 Steel surface with reduced thickness of scale

Fig. 3 Measured cooling intensity for surface with original thickness of scale (O1) and reduced thickness (OP2-OP5)

Description of 2nd experiment

Two types of surfaces of a steel plate were used in spray cooling tests. The first sample was cleaned by pickling (Fig. 4, left). The second sample was covered by compact layer of oxides of average thickness of 15 µm (Fig. 4, right). The both samples were initially heated in protective atmosphere to 500°C and then cooled by same water nozzles. The results are shown in Fig. 5. This test confirmed that the cooling intensity for perfectly clean surface is lower than for surface covered by oxides.

15 μm

Fig. 4 Steel surface after pickling (left), steel surface with about 15 µm layer of oxides (oxides – dark grey)

Both from the above results are contradictory to the idea that oxides with the low thermal conductivity protect the cooled surface and decrease heat transfer intensity. Numerical analysis was used to explain the discrepancy.

Fig. 5 Measured cooling intensity for clean surface (magenta) and for surface with oxides (red)

NUMERICAL ANALYSIS

Model introduction

Let us consider two simple models (Fig. 6). The reference model is steel body with clean surface and the second model is the steel body with layer of oxides (Fig. 6, right). Thickness of oxide in model is considered from very thin (3 µm) to relatively thick (1000 µm). Surface temperature of steel is Ts and surface temperature of oxide is Tp. Heat flux through steel surface is marked Qs and through oxide surface Qp respectively. Initial temperature of the samples is 1000 °C. Heat transfer coefficient used in numerical modelling is plotted in Fig. 7.

Page 86: 2-page abstracts booklet

STEEL STEEL

OXIDE

Qs Qp Tp Ts

Ts Qs

Fig. 6 Scheme of symbols in computation, clean steel surface and steel body with layer of oxide

Tab. 1 Material properties used in numerical model Thermal

conduction [W/mK]

Specific heat [J/kgK]

Density [kg/m3]

scale steel scale steel scale steel

0.17 60 970 434 5700 7850

Numerical results

Cooling starts at time of 0.1 s and evolution of temperatures is shown in Fig. 8. Clean steel surface is considered as reference. Thin oxide layer (3 µm) has almost no influence. Surface temperature of thick oxide layers falls drastically down to 300°C in 0.1 s but steel covered by thick layer of oxide is hotter than clean steel. Oxides act as thermal insulation in this case. Interesting is behaviour of medium-thick oxides. The surface temperature of layer 30 µm thick starts to drop at time 0.4 s when the surface temperature reaches 800 °C. For explanation see Fig. 7. At the same time starts to fall temperature of steel under oxides. Heat flux from the steel surface covered by 30 µm oxides is 0.5 second after start of cooling about THREE times higher than heat flux from the clean surface (see Fig. 9). Thickness of scale in presented example causes that surface temperature of steel covered by 10 µm scale drops in 1 second of cooling by 100°C and surface temperature of steel covered by 30 µm scale drops in 1 second of cooling by 600°C.

CONCLUSION

Scale layer on steel surfaces can have enormous influence on cooling intensity of sprayed hot surfaces. The effect depends on thickness and thermal conductivity of oxides, on performance of nozzles and on duration of cooling. Heat fluxes from steel surfaces covered by oxides can be several times higher than from clean steels.

Fig. 7 Dependence of cooling intensity (HTC) on surface temperature used in numerical model

Fig. 8 Temperature history at surface of oxide and steel surface - numerical analysis

Fig. 9 Heat fluxes history - numerical analysis

ACKNOWLEDGEMENT

The research in the presented paper has been supported within the project No. CZ.1.07/2.3.00/20.0188, HEATEAM-Multidisciplinary Team for Research and Development of Heat Processes.

REFERENCES

[1] M. Raudensky: Heat Transfer Coefficient Estimation by Inverse Conduction Algorithm, Int. J. Num. Meth. Heat Fluid Flow, Vol. 3, No. 3, 1993, p. 257-266.

[2] M. Raudensky, M. Druckmuller, J. Horsky: Inverse Heat Conduction Problems and Generalisation of Experimental Results, ASME Int. Mech. Engineering Congress, Anaheim, Vol. 5, 1998, ISBN 0-7918-1597-8, p. 65-72.

Page 87: 2-page abstracts booklet

Increasing the productivity of the vertical continuous casting

machine at Hagondange plant.

J. Demurger, J. Gremillet, M. Mattei, M. Stilgenbauer, V. Seemann, G. Boi, P. Gibondi

Ascometal, Hagondange

INTRODUCTION

At Hagondange, a 4-strand vertical continuous caster produces 240x240 mm2 square blooms, mainly dedicated, after rolling and finishing, to the automotive industry (gearbox component, injection ramp…). The grade mix for these applications is made of 37% of grades sensitive to cracking and of 36% of grades sensitive to breakout during casting. To reduce both risks, the casting speed has been reduced. A research project has been launched to improve the productivity of the caster, without increasing the defect occurrences.

Different revamping solutions were designed by plant suppliers to increase the casting speed: increase of the mould length and/or different modifications of the secondary cooling (cooling length, sprays types, spray position, flow rate…) have been proposed.

Modelling has been used to compare the different proposals and to choose the best investment guaranteeing the productivity and the reduction of cracks occurrences.

The billet corner is mostly affected by subsurface cracks. Subsurface cracks are particularly dangerous because they can cause surface cracks and breakouts. Cracks are due to tension in the mushy zone close to the end of solidification when the dendritic network is unable to sustain the tensile stresses. A thermomechanical model and precise boundary conditions are needed to be able to compute and compare strain and stresses for the different solutions.

THE MODELLING

The Thercast® software has been used for years at Ascometal for the thermomechanical modelling of the casting processes. Thercast® uses a non steady state approach for the continuous casting simulation. Detailed description of the software and of the constitutive model can be found in previous publications [1]. Concerning boundary conditions, measurements are needed to precisely characterise the heat transfers in the mould and in the secondary cooling.

Primary cooling

The quantity of heat extracted in the mould, in the so-called primary cooling zone, is directly linked to the cooling water temperature variation. The 4 sides of the mould were equipped with temperature-sensitive sensors. Data were recorded for 51 casts at different casting speeds. All results are plotted in Figure 1 versus casting velocity. A linear function between casting velocity (V in m.min-1) and heat flux density ( aver in MW.m-2) can be written:

BVAaver . with A=5.5 10-1 MW m-3.min-1 and B=0,59.10-1 MW.m-2.

y = 0.5711x + 0.5264R2 = 0.7069

0.8

0.850.9

0.951

1.051.1

1.151.2

0.5 0.6 0.7 0 8 0.9 1 1.1

Casting velocity (m.min 1)

Heat

flux

den

sity

(MW

.m-²)

Figure 1 Heat flux density in the mould versus casting

velocity

Heat withdrawal in the secondary cooling zone

Our model must be precise enough to compute strain and stresses due to spray impacts on the bloom and due to reheating between the different rows of sprays. In the 3D model, each spray is introduced with its own cooling variation in the target. Heat exchange coefficients were deduced of spray characteristics and of data available in the literature [2] giving the relation between flow rate and heat exchange coefficient.

066

114162

210

0 12 24 36480

500

1000

1500

2000

2500

h (M

W/m

²/°C

)

X

Z (mm)

0

66

11

162

210

032

696

1280

200

00

600

800

1000

1200

1 00

h (W

/m²/°

C)

X

Z mm)

Figure 2: Variation of heat transfer coefficient with position on spray target (left water flow rate of 465 l.m-2.min-1 and

right water flow rate of 223 l.m-2.min-1).

This relation has been adjusted, for the Hagondange caster, using temperature measurements at the bloom surface in the secondary cooling zone. For these measurements, air cooled optical fibres, were fixed in the secondary cooling zones. Figure 2 shows the heat exchange coefficient variation with the position on spray target for two values of water flow rate and Figure 3 shows a comparison between the thermal

Page 88: 2-page abstracts booklet

profile at mid face calculated with Thercast and a temperature measurement.

800

900

1000

1100

1200

1300

1400

1500

1600

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6Distance from meniscus (m)

Tem

pera

ture

(°C

)

THERCASTPyrometer measurement

Mould

SC (Secondary Cooling)Mould

SC

Meniscus

Meniscus

Figure 3: Comparison between the thermal profile (mid face) calculated with Thercast and a temperature measurement.

Damage criterion

The criterion of Yamanaka et al. [3] is pertinent to forecast the location of hot tears in solidification conditions. This criterion is expressed as follows:

2

1

ˆs

s

f

fc dt

where 21, ss ff are two characteristic solid fractions

and ̂ denotes a norm associated to the damaging components of the strain rate tensor, that is those orthogonally exerted with respect to the crystal growth direction

RESULTS

Figure 4: Bulging of the solid shell (left) and Yamanaka criterion contours (right),

The damage criteria contours obtained with the existing configuration was compared to the criteria values obtained with different modifications. It has been found a direct link between the bulging of the solid shell and the damage value as illustrated on Figure 4. Figure 5 shows that the best reduction of the bulging, and consequently of the damage, was obtained both with a mould length increase and with a strand support modification (addition of a mould foot roll). The second solution was chosen because cheaper and easier to install. New water flow rates adapted to the increased casting speed were calculated with the model.

F Bulging contours: current (left), with a mould length increase (middle), with a strand support modification (right).

PLANT REVAMPING AND PRODUCTIVITY RESULTS

Depending on the modelling result, a technological modification was made on primary cooling and on secondary cooling zones. The number of foot rolls directly under the mould was increased. Figure 6 shows the new design of foot rolls.

Figure 6: New design of the primary cooling zone.

With a prototype machine on one strand, a trial plan on casting speed was carried out. Trials have shown that the maximal achievable increase in casting speed was approximatly 14%. Quality controls on blooms and bars were made. No crack on blooms and bars have been detected by ultra sonic test. The number of breakout was equal with both systems. In 2012, an investment to full equip the machine was made. The result is an increase of 4% of the productivity on the complete steel grade range. Next step is to extend the calculations to a new set of special steels to increase 1% more the productivity. Authors want to thank Romain Forestier for his major contribution to this work.

[1] F. Costes, Modélisation thermomécanique tridimension-nelle par éléments finis de la coulée continue d'aciers, Ph.D. thesis, Ecole Nationale Supérieure des Mines de Paris (2004).

[2] R. Jeschar, U. Reiners, R. Scholz, Heat transfert during water and water-air spray cooling in the secondary cooling zone of continuous casting plants, 69th Steelmaking Conference, Washington, Vol. 69, Book 1, 6.-9. April 1986, pp 511-521.

[3] Yamanaka, K. Nakajima, K. Yasumoto, H. Kawashima, K. Nakai, Measurement of critical strain for solidification cracking, Model. Cast. Weld. Adv. Solidification Processes V, (M. Rappaz et al. eds., TMS, 1991) 279-284.

00.0010.0020.0030.0040.0050.0060.0070.0080.0090.01

00.0010.0020.0030.0040.0050.0060.0070.0080.0090.01

Eps Yamanaka

00.10.20.30.40.50.60.70.80.91

00.10.20.30.40.50.60.70.80.91

mm

00.10 20 30.40 50 60.70 80 91

00.10 20 30.40 50 60.70 80 91

mm

Page 89: 2-page abstracts booklet

Thin slab casting and rolling has been originally developed as a “low cost” alternative to conventional casting and rolling process route for the production of Hot Rolled Coils. However , due to the technological restrictions of the “first generation plants” , limited quality and productivity goals could be achieved, questioning the further application of this technology to more advanced applications. Since the first developments of this process route, back in 1984, Danieli clearly identified these as limitations that must be overcome, in order to guarantee investment profitability. It is well known that the original idea that generated this concept was to establish a viable economical alternative to conventional process route, with the target to limit both capital investment and operational transformation cost involved by the huge conventional complexes that till that time have been the only way to produce hot rolled coils. This concept has been a winning concept, however, due to technological limitations of what Danieli calls “ First generation plants” , involved also some substantial limitations in his applications, namely: • a limited range of grades could be produced

according to market requirements • a limited productivity could be reached, mainly due

to the limitation in caster productivity, hence limiting to “a regional approach” the market that can be targeted.

The success of this technology has been guaranteed in recent years by: • a tremendous increase the productivity level • a dramatic extension the product mix: • a significant increase of the quality of the

products: • the Introduction of new products in the range of

hot rolled coils, normally not targeted by conventional mills, such as ultra thin gauges production.

Among others these are the results that have been progressively reached adopting Danieli technology: The new generation of Danieli

thin slab casting and rolling plants: lay out concepts breaking

all actual parameters in Capex and Opex for advanced markets

and product mix.

Carlo P. Piemonte, Danieli Wean United, Executive VP Thin Slab Rolling

Alessandro Pigani, Danieli Wean United, Manager Technology Hot Rolling Mill

Productivity: From 0.8 Mtpy (per casting strand) of first generation plants, to present target productivity already consolidated at 2 Mpty ( per casting strand). Tangshan Iron & Steel plant, (P.R. China) has been the first plant in the world able to produce in excess of 3.0 Mtpy of coils adopting thin slab casting and rolling process , since 2005. Posco Gwangyang plant( Korea) in production since 2009 demonstrated the possibility to reach 4 Mtpy, with 2 casting strands in operation. Mix grades: From low and medium carbon grades targeted by first generation plants we have been able to progressively produce in industrial conditions, among others: Peritectic and Advanced High Strength Steel, ( Essar Algoma plant since 199.) ,Silicon steel grades and weather resistant grades ( Benxi China, since 2007), API grades( Omk, Russia , since 2009) The latter being the first thin slab casting and rolling plant in the world specifically conceived for the production of top quality pipe grades, like API X70 and X80 even for arctic applications with workink temperatures as low as -60 C Environmental aspects Thin slab casing and rolling technology can give a substantial contribution to social acceptance of steel plants, with his reduction down to 35% of the carbon dioxide emissions, generated by the absence of intermediate reheating process of the slabs. The Danieli approach to thin slab casting and rolling. Danieli, since its first pioneering experiences in 1984, developed his own design concepts based on the following principles: • Definition of the slab thickness according to quality

and productivity requested by the mill • Definition of mill lay outs that allow the application

also of advanced rolling practices, such as thermo mechanical rolling.

Two are the areas where Danieli differentiate its product compared to other available solutions. • Caster design • Mill arrangement

The Danieli “flexible” Thin slab Caster : fTSC Since the first pioneering applications, Danieli adopted a thin slab caster the following solutions, adopted in ALL his thin slab casters ( versus solutions adopted in other “first generation”design available on market) • Vertical curved design vs. vertical design

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• H2 long funnel mould vs. conventional short funnel mould

• Dynamic soft reduction vs. static soft reduction • Air mist secondary cooling vs. water only • Independent cooling of all rolls and wear sensitive

elements vs no cooled elements All Danieli fTSC embody these concepts in casting thin slabs ranging in thickness from 45 up to 110 mm (ALWAYS after dynamic soft reduction application) selected according to final product quality requirement The Danieli rolling mill lay out The following solutions, targeting different market needs, have been developed and installed. TSR Thin Slab Rolling: it resembles the first generation of thin slab casting and rolling plant, which is mainly composed by a 60 mm slab caster followed by tunnel furnace and a finishing mill consisting of 6 / 7 rolling stands in “cluster “configuration.

fTSR flexible Thin Slab Rolling; in this layout a physical separation between roughing and finishing stands has been introduced to allow the installation in between of: - a crop shear, to improve the rolling stability, for better production of thin gauges and improvement of finishing mill conditions - a proper descaler station, to improve the strip quality by cleaning the transfer bar prior to enter into the finishing mill. - an intensive cooling system, to increase the variety of steel grades which can be produced, by ferritic and thermo mechanical rolling.

QSP Quality Strip Production lay out;, the first lay out allowing the real “two step” rolling in roughing and finishing process. Here, roughing stands and finishing stands are completely independent allowing to adopt in each unit the proper optimal rolling conditions ( rolling speed/rolling temperature). Thanks to intermediate strip temperature control tools, is possible to perform the real thermo mechanical

rolling process, compulsory for superior quality grades, such as API for ARCTIC applications. ETR The most recent developments in plant configuration and Ultra High Speed casting led Danieli to develop

the ETR lay out , which means Extra Thin Rolling, specifically conceived to produce ultra thin gauges via “endless” process.

With Danieli ETR solution, both “coil to coil” and endless rolling modes can be adopted. Conclusions and outlook In the last 20 years this technology has been developing into new configurations for thin slab casting and rolling, abandoning the first generation approach, ultimately reaching comparable performances of conventional plants, both in productivity and quality. At present the “coverage” of the flat product market applications by thin slab casting route is almost completed, only specific areas are still fundamentally excluded, such as the ones where metallurgy imposes very high reduction ratios in rolling, or where process temperatures are not compatible with an uninterrupted process. Thanks to these consolidated results, customers can adopt this process route as: “Regional approach”: serve local markets i.e. also with limited productivity but with high added value production, hence high marginal value. “Global approach”: enter in the global market of large scale multi million tons per year plants , up to now domain of the large conventional mills, but with the strength of an unbeatable transformation cost, hence playing as “transformation cost winner” . Target the ultimate production niches, let’s say the “aristocracy of the steel family” as epitomized by the automotive exposed market.

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Arvedi ESP – Three years of successful operation

Andreas Jungbauer - General Sales Manager ESP, Siemens VAI/Austria, Wersching Günther - Sales Manager ESP, Siemens VAI Bumberger Armin – Integrated Plants Development, Siemens VAI

Introduction Invented by Giovanni Arvedi and implemented together with Siemens VAI, the vision of producing hot-rolled coils directly from liquid steel in an uninterrupted production process has become reality at the Arvedi ESP (endless strip production) plant in Cremona. Already during the first year of industrial operation, a number of milestones were achieved that included casting speeds of 6 m/min; the continuous production of strip coils at widths of up to 1,580 mm and at thicknesses down to 0.8 mm; products characterized by excellent dimensional, metallurgical and mechanical properties; high yield figures; and particularly reliable and stable operating conditions. The plant has a minimum nominal capacity of 2.0 million tons and is capable of producing a wide range of premium steels.

Today, production sequences comprising eleven ladles with a total of 2,750 tons of liquid steel are routinely processed in a single line to approximately 100 hot-rolled coils. Continuous casting operations are especially dependable with only five breakouts registered during all of 2010 as well as in 2011. In fact, no breakout incidence occurred whatsoever for half a year during continuous production beginning September 2010. More than 30% of the coils ready for dispatch have a strip gauge of less than 1.5 mm, thus commanding premium sales prices. Once the desired minimum gauge is reached, usually in the early stage of a production sequence, rolling at this thin gauge is typically carried out for the rest of the production campaign. Strip lengths of 170 km and more are normally generated. A cobble rate of less than 0.06% was demonstrated as a monthly average during rolling operations – underlining the stability and reliability of the process. The yield from liquid steel to good coil exceeds 98%.

Alternative production routes One of the most important issues steel producers interested in ESP technology deal with is the configuration of overall plant integration, including the type of melt shop, the ESP line (direct sales of high-quality coils) and further processing.

The compactness and flexibility of Arvedi ESP offers owners of conventional minimills and operators intending to manufacture flat steel products the perfect opportunity of entering the high-quality steel segment and producing ultra-thin hot-rolled strip with the advantage of the high contribution margins discussed below.

An Arvedi ESP line can also be integrated into a BOF-based minimill. Because of the very short line length, integration is possible in parallel with continuous casting lines without interfering or compromising the typical melt shop logistics in green field projects or even brown field projects with space restrictions.

ESP offers the unique option of expanding the product portfolio to a larger number of value-added products. The ESP line can also be a means to produce hot-dip galvanized strip based directly on HRC feedstock, because the required strips have a typical thickness of roughly ranging between 0.8 and 1.0 mm. The combination of a compact pickling tandem line with three mill stands facilitates the production of thin-gauge cold-rolled strip in a second production step, e.g. 0.2 mm.

The unique product dimensions and quality of ESP strips most economically serve the market from thin and wide strips and are the reason that the endless ESP process was designed. Full width, ultra-low exit thicknesses, excellent quality, no strip heads and outstanding performance in geometrical dimensions (crown, wedge, flatness) are other advantages of this innovative process.

Plant economics Investment costs – Arvedi ESP is the shortest process route for the production of prime hot-rolled coils directly from liquid steel and in thicknesses ranging between 0.8 and 12 mm. The most important advantage of an ESP plant is its investment costs, which is strongly related to its compact plant design. The length from the center line of the ladle turret to the center line of the second down coiler is only approximately 180 m. Both a minimum of processing equipment and significantly less space requirements result in minimized civil works and less steel structure in the bays. Significantly less effort and volume for interconnecting piping and cabling are required.

Conversion costs – A calculation of the specific cost types (yield losses, energies, other supplies and personnel) for an Arvedi ESP plant indicates overall conversion costs of €28.4 per ton of hot-rolled coils.

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Specific Cash Conversion Cost Liquid Steel to Hot Rolled Coil

16,5 €/t

6,8 €/t8,3 €/t

17,5 €/t

14,4 €/t

18,3 €/t

1,8 €/t

2,2 €/t

2,4 €/t

9,0 €/t5,0 €/t 7,9 €/t

44,9 €/t

28,4 €/t

37,0 €/t

Conventional ESP Other Thin Slab

Material costs (yield losses) Energies Other op. supplies Personnel

Below is a detailed evaluation of the advantages of Arvedi ESP in relation to the individual cost types as used in the above calculation.

1. Yield – Operational results of the new Arvedi ESP plant during the past months confirm an average yield (liquid steel to prime hot-rolled coils) of 98% based on minimum accumulation of scale during reheating due to the very short inductive heating track of roughly 10 m only and no head and tail losses in the finishing mill.

2. Energy costs – The heat after casting is optimally utilized for rolling operations, thus reducing the demand for deformation energy to a minimum since the strip is still soft in the center during initial reduction steps thus reducing energy consumption by more than 50% as compared to conventional processes.

3. Other operating supplies – The most important savings are roll consumption in all parts of the line due to continuous processing of material in 2-step rolling or less maintenance in reheating section due to compact design of Arvedi ESP inductive heater

4. Personnel costs – Specific personnel cost savings in the operation of an ESP line as compared to other production lines are due to the following factors like one caster operation group only or avoidance of slab storage staff

Value added

High proportion of high-quality thin gauges – Market prices for thin gauge flat products show increasing premiums. Hot-rolled flat products below 1.5 mm are already sold in the market segments of cold-rolled coils. As the productivity of most hot rolling processes decreases significantly below 2.5 mm, the ESP process shows practically no decrease in the thin gauge rolling segment and can even go down to 0.8 mm. Unique to Arvedi ESP is that production of these ultra-thin and wide strips is independent of the final gauge thickness.

Cold-rolled strip substitute – The use of thin-gauge hot-rolled strip instead of cold-rolled strip is even more promising because this saves the energy required for cold rolling, annealing and skin passing. The high-quality thin gauges provided by the endless process route contribute to the steadily growing acceptance of thin-gauge hot-rolled coil.

Starting from a thin hot rolled product with excellent precision, dimensional and flatness characteristics, Arvedi ESP offers the advantage of obtaining gauges as thin as 0.3 and 0.2 mm with a limited number of cold-rolling steps with lower investment and lower processing costs.

Contribution margin and return on investment – Such positive results are also reflected by the IRR (internal rate of return) calculation comparing ESP technology to other thin slab casting and rolling technologies, based on the sensitivity of variation in annual production. Arvedi ESP leads to >30% IRR, which is more than a quarter higher than in other thin slab technologies.

Summary The arguments in favor of ESP technology are summarized in four main aspects that are advantageous to both the contribution margin and rate of return:

• Sales revenue premium of up to 30% for 0.8-1.5 mm hot-rolled coils • Lowest conversion costs per ton (€ 28.4) • Highest flexibility and productivity • Low investment and maintenance costs due to compact plant layout

Arvedi ESP technology is the No. 1 technology for add-on investments of integrated plants in the thin-gauge market. Other important advantages are backward integration, the creation of one’s own hot-rolled feedstock and entrepreneurial diversification in the area of flat steel products.

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CSP® flex - New CSP® concepts for future market requirements

C. Bilgen, C. Klein, C. Klinkenberg, J. Müller (SMS Siemag AG)

INTRODUCTION

Since more than two decades, CSP® is the most successful thin-slab concept worldwide. Recently, expanded market demands led to new developments. Today, CSP® offers extended possibilities regarding production capacity and product mix - especially of high-strength grades. These new developments are summarized under the label CSP® flex. In addition, energy consumption is reduced drastically, so that CSP® is the most economical plant concept for the production of high-quality hot strip.

These developments had to be made without forfeiting the strong points of CSP® such as low operating costs, high availability and yield, absolutely uniform product properties and a wide range of different steel grades. To fulfil this, new components for casting, heating and rolling were added to the CSP® concept. This allows new, tailor-made technological solutions to be provided.

PROVEN CSP® TECHNOLOGY

Today, the 27 CSP® plants account for some 10% of the entire global hot strip production. The product range covers all of the steel grades demanded by the market including low-carbon IF, HSLA and pipe grades, acid and heat resistant special steels as well as Si-alloyed electrical grades.

Just one example of many successful commissioning projects is the CSP® plant at Severstal Columbus (USA). With a nominal width of 1,880 mm, this plant is currently the world’s widest. Severstal Columbus uses it to produce strip with widths of up to 1,918 mm. The slab thickness, at 65 mm, is equivalent to that of a typical CSP® plant. Despite the high width/thickness ratio, the caster has a high availability and an extremely low breakout rate. Severstal Columbus has achieved a maximum production of approx. 140,000 t per month on one strand. The total production in 2010 was 1.54 million t per strand.

Another strong point of CSP® is the production of thin strip with some plants producing 30% of their annual output in gauges of 1.2 mm or less. At Essar Steel (India) sequences of more than 30 strips in final gauges of ≤ 1.1 mm were rolled as early as the fourth month after commissioning. The optimum final rolling temperature was achieved for all strips (fig. 1).

Fig. 1: Thin-strip rolling campaigns at Essar Steel.

CASTING MACHINE CONCEPTS FOR A WIDE CAPACITY RANGE

The key to boosting the annual capacity and increasing final strip thicknesses is the casting machine. So far VSB (Vertical Solid Bending) casting machines have been used. These casters, which operate with a solid core in the bending zone, achieve production volumes of about 1.5 million tons per year per strand. Typical features of VSB casters are symmetrical strand cooling and solidification, short mold and segment change times and ease of maintenance.

Production is raised by increasing the cast thickness. This requires a greater metallurgical length in the casting machine, which can be economically achieved by the use of a VLB (Vertical Liquid Bending) casting machine. VLB-type casters operate with a liquid core in the bending and straightening zones. Production volumes of 2.0 million tons per year per strand are possible.

ROLLING MILL CONCEPTS FOR THE PRODUCTION OF PIPE GRADES

A major development focus was on the production of pipe grades. High-strength pipe grades with excellent toughness properties up to a thickness of more than 12.7 mm can already be manufactured from slabs of thicknesses between 50 and 60 mm on the compact CSP® rolling mill. With the new Vario Mill (fig. 2), the final thickness of e.g. API X70 grade can be increased to 20 mm.

Fig. 2: CSP® Vario Mill

For the production of high-strength pipe steel strip, it is essential that the hot strip features an entirely homogeneous, fine-grained microstructure. Otherwise it will not be possible to attain an optimal combination of strength and toughness. This can only be achieved by a two-stage hot rolling process. In the first stage, rolling takes place in the recrystallizing and, in the second stage, in the non-recrystallizing temperature

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range. During the first stage, the irregular cast structure must be transformed into a homogeneous recrystallized microstructure. This procedure achieves a fine-grained, very homogeneous hot strip with excellent strength and toughness properties.

By suitably setting the pass reductions and temperatures, the CSP® Vario mill guarantees that the microstructure completely recrystallizes at least two times (fig. 3). An induction heating system is installed in the gap between M1 and F1. The intermediate strip is fed into the induction heating system via a pre-leveler. The temperature of the strip and its transfer time between M1 and F1 are controlled such that complete recrystallization will take place after the two stands. This technique enables the production of thicker hot strip with higher strengths and at the same time superior toughness properties. In comparison with concepts with one or two decoupled roughing stands, there is no premature precipitation of micro-alloying elements or substantial grain growth. Thus, higher micro-alloy contents can be attained enabling hot strip of higher strength classes to be produced. Thanks to the complete elimination of non-homogeneities originating from the cast structure, thicker strip can be obtained from slabs of a given thickness.

Fig. 3: Temperature control during isothermal rolling on a CSP® Vario Mill and sampling point.

This result was proven by intensive scientific research. The microstructure of an API grade X70 sample produced on the Vario Mill consists of uniformly recrystallized grains and is free from non-homogeneous constituents. The grain size distribution shows a scatter band closely grouped around the mean grain size.

CSP® ENDLESS ROLLING

For customers aiming at a production with a very high proportion (above 50 %) of thin and ultra-thin hot strip below 1.2 mm thickness, then the endless mode of operation can be added.

To achieve acceptable final rolling temperatures in endless operation, inductive reheating is required in the rolling mill. Consequently, for energy-related reasons, batch operation should be applied to all products and final gauges which do not benefit from the endless casting and rolling mode. Main

components of this plant concept are a caster of VLB type for high production, a Core Reduction (CR)-stand, the Vario Mill including inductive heating and a high-speed shear.

ENERGY EFFICIENCY

Rising energy costs put pressure on steel producers. Thus, SMS Siemag further developed CSP® with respect to energy efficiency and reduced consumption to a minimum. This ambitious goal was realized by analyzing the complete production process as well as all components.

Concerning the process, the temperature of the thin slab is no longer increased up to a temperature which is ideal for all grades and dimensions, but is kept on a lower level close to the temperature after casting. With this lower temperature the overwhelming part of grades and dimensions can be rolled without constraints in process stability and product quality. This leads to drastic savings in energy.

The reduction of the tunnel furnace temperature goes along with the installation of inductive heaters in front of the rolling mill. When rolling grades or dimensions requiring a higher rolling mill entry temperature, it can be set precisely by means of inductive heaters. With this solution, the large product spectrum typical for CSP® and a reduction of energy consumption can be realized at the same time.

On the level of plant components, largest energy savings can be realized by installation of dry-type furnace rollers. With new high-temperature alloy furnace rollers by SMS Siemag, the heat extraction out of the tunnel furnace can be reduced by 50 percent compared to water cooled rollers. Further measures to reduce energy losses are the installation of a rotary descaler in the entry of the mill and the reduction of stand distance in the CSP® mill (fig. 4).

Fig. 4: CSP® plant with inductive heating at mill entry.

With the installation of dry-type furnace rollers, a rotary descaler and the reduction of the tunnel furnace temperature in combination with the inductive heatings, parts of this concept can also be applied to existing CSP® plants. This modernization concept will be for the first time realized at the Nucor Steel plant at Berkeley (USA).

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Session 7: Long product rolling

Table of Contents

7.1 WinLink® innovative concept for direct rolling of long products E. COLOMBO, U. ZANELLI (Siemens VAI Metals Technologies Srl), Italy

7.2 Installation of Direct Rolling Mill K. OHUCHI, S. HIGO, M. MINAMI (Godo Steel), Japan

7.3

Outline and operating results of the first Heavy Duty Reducing & Sizing Block (RSB) in France J.Y. VERNEDAL, G. MATHIEU (Ascométal), France, S. SCHWARZ, B. ZUTER (Friedrich Kocks Gmbh), Germany

7.4

The closed loop size control system in combination with the advanced 3-roll PSM® at DEW Siegen-Geisweid T. HELSPER, J. EISBACH (Deutsche Edelstahlwerke), G. SCHNELL (SMS Meer), Germany

7.5

Revamping of Ascométal Fos-sur-Mer Wire Rod Mill F. LECOUTURIER, J.Y. VERNEDAL, B. ONDE (Ascométal), A. BORYSOWICZ (Fives Stein), France, L. CAVALETTI (SMS Meer S.p.A.), Italy, A. OLSSON (Sund Birsta), Sweden

7.6

Improving reliability of mill drive gear boxes at New Bar Mill, Tata Steel R. MALHOTRA, G.R.P. SINGH, M.N. SHUKLA, P.K. BANERJEE, B.K. DAS (Tata Steel), India

7.7

Latest developments in drawing and peeling technology K. VAN TEUTEM (Danieli & C Officine Meccaniche S.p.A.), Italy, P. MARESCH (Danieli & C Officine Meccaniche S.p.A.), Germany

7.8

Major improvements of the piercing mill at Vallourec & Mannesmann Tubes J.P. BRANCART (Vallourec & Mannesmann), P. ROBLIN, G. MUZARD (GE Energy Power Conversion), France

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WinLink® Innovative Concept for Direct Rolling of Long Products

E. Colombo (Siemens Vai Metals Technologies Srl)

U. Zanelli (Siemens Vai Metals Technologies Srl)

INTRODUCTION

WinLink is the name of the innovative technology from Siemens Metals Technologies for the endless production of long products from liquid steel. Through the direct linking of a high speed/high productivity billet caster to a rolling mill in a highly compact production line, producers benefit from low investment expenditures, reduced transformation costs, significant energy savings, reduced CO2 emissions and higher-profit production of long products. WinLinkcombines proven high-tech solutions with the experience acquired in more than two years of industrial operation of the Arvedi ESP (Endless Strip Production) plant. Compared to similar solutions, WinLink additionally offers the possibility of using a full-size meltshop and balancing the production among rolled product and saleable billets. WinLink is a registered trademark of Siemens VAI Metals Technologies GmbH.

Figure 1. WinLink-based minimill

A WINNING LINK OF ADVANCED TECHNOLOGIES

The current economic crisis has led steel producers to reconsider the advantages of small minimill plant in

the range of 300,000 to 600,000 t/a such as the use of locally available scrap; the sale of final product on the regional market to reduce the transportation costs; a low impact on the electrical energy grid; a high degree of flexibility to adjust production rates to market requirements; and comparably low investment expenditures. Despite these advantages, the relatively long payback period due to low-output has been the main obstacle for a much broader application of minimills for long products producing standard carbon-steel grades primarily for use in the construction applications.

A NEW MINIMILL CONCEPT

In response to this situation, Siemens VAI is now introducing WinLink, a new minimill concept for the production of long products that combines the advantages of small plant sizes with a fast payback period. In WinLink, a billet caster is directly linked to the rolling mill whereby liquid steel is processed to rebars or other long products in a continuous, endless production line. To ensure optimum utilization of the respective EAF (electric arc furnace), continuous casting and rolling facilities, the WinLink solution foresees a high-speed billet caster equipped with at least two casting strands (Figure 2). The additional billet strands support a full production capacity of the steel shop, ensure that the rolling mill is reliably supplied for the required product mix, and additionally allows billet semis to be separately cast for external sales. This solution approach maximizes the plant throughput while providing a high degree of flexibility to rolling – in addition to rebars, small flats and profiles – or billet semis as required by the market. A WinLink-based minimill can produce between 400,000 t/a and 500,000 t/a of billets, of which 300,000–400,000 t/a are rolled to rebars and 100,000 t are available as saleable-quality billets for external sales. Siemens VAI offers different plant configurations and process options, to enable the casting of a broad range of strand sizes and shapes, including rectangular and round formats. Thus, producers benefit from the flexibility to produce a wide range of product dimensions to meet also orders of small lots. The main features of the individual plants installed in a WinLink-based minimill are here outlined.

Figure 2. General flow sheet of a WinLink-based minimill

Crane acti ity charging -teeming Crane acti ity Casting - Rolling

Coon

be

Approx 300 mLength

Billets for Sale 110x100-150x150mm

EAF LF

CCM

Rolling mill

Patentpending!

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EAF AND LADLE FURNACE

The Ultimate EAF is designed for performance. All of the latest electric steelmaking solutions from Siemens VAI are applied to maximize productivity. For example, the single-point roof-lifting system supports fast and efficient roof movements during scrap charging. The high sidewalls of the furnace shell allow single-bucket charging, which reduces scrap-charging times. The application of RCB (Refining Combined Burner) technology fulfils numerous functions such as scrap preheating with a powerful burner at the start of the melting process; post-combustion to promote exothermic reactions; and supersonic oxygen injectionfor steel-refining purposes. These and other features promote a high degree of efficiency, low consumption and short tap-to-tap times down to nearly 30 minutes. An Ultimate EAF furnace installed in a WinLink-based minimill would have a tapping weight in the range of 35–50 tons. Adjustment of the required liquid-steel temperature for continuous casting and minor alloy additions then take place in the ladle furnace.

HIGH-SPEED BILLET CASTER

High-speed billet casters from Siemens VAI are installed with the latest equipment packages and systems to allow casting speeds of up to more than 7 m/min. Special design features include an implemented version of DynaFlex hydraulic oscillation. Casting speeds as required in a direct rolling application were already obtained with such an oscillation unit in billet casters.This proven technology, based on leaf spring guidance of oscillation is suitable for the optimum adjustment of the oscillation parameters over a wide range of casting speeds and gives complete freedom for on line adjustment of stroke and frequency. The system is maintenance-free.Additional features include an enhanced generation of the patented DiaMold mold tubes, designed for accelerated heat removal at high casting speed without detrimental effects for product quality and to ensure correct shape and dimensions of the as cast product. It optimizes the strand containment and guidance at high speed. A proven secondary cooling system for high speed applications is promotes the uniform shell growth, andavoids reheating problems and excessive temperature loss; this minimizes the need for subsequent temperature equalization of the strand prior to rolling. Suitable design of straightening unit avoids risk of excessive strain of the billet.

INDUCTION FURNACE

A high-performance induction furnace is installed between the billet caster and rolling mill to equalize the temperature of the billet. This setup represents the best technical solution to rapidly achieve the required rolling temperature. The induction furnace replaces the conventional gas-fired reheating furnace, thereby

reducing CO2 emissions and the environmental impact.

ROLLING MILL

Long-rolling mills supplied by Siemens VAI for the production of rebars are equipped with all the required advanced mill components. Well-proven, highly rigid Red-Ring stands, Morgan-Ashlow guides and dedicated equipment such as the Power Slitter guide, high-performance PQS (Pomini quenching system), stand presetting equipment and inline gap control,allow producers to operate long rolling campaigns, as required in an endless process.

ELECTRIC AND AUTOMATION

Siemens’ experience in the electrical and automation fields is unsurpassed. Its automation and process-control are the customer's guarantee for smooth plant operations, reliable process control, exact temperature regulation throughout the WinLinkproduction line. The careful tracking throughout the process from scrap to final product dispatch, contributes to maximum plant productivity.

MAIN BENEFITS AT A GLANCE

In comparison with conventional minimill plant configurations, WinLink offers a number of decisive advantages for producers (see also Figure 3): Lower capital expenditures for main equipment;Lower operational expenditures up to $40/t of rolled steel;Low inventory and working-capital requirements;Reduced manpower requirements;Reduced civil works and infrastructure costs;Reduced energy consumptionHigher product yield due to long uninterrupted casting and rolling sequences;Low CO2 emissions and fluid consumption;Smaller minimill footprintProduction of final products from scrap in less than 2 hours.The successful experience from the Arvedi ESP process for the flat products is now available for a WinLink-based minimill facility. The future integrationwith high efficiency production systems in EAF field, such as Quantum, is being developed.

Figure 3. Comparison of key factors between a conventional minimill and a WinLink-based minimill

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Installation of Direct Rolling Mill Katsuhiro Ohuchi

Masamichi Minami, Seikichi Higo

(Funabashi Works, Godo-Steel,Ltd. Japan)

1. Introduction

Godo steel, Ltd. Funabashi Works, Chiba Japan, produces deformed bars. Direct rolling facility was set up in September 2010 in order to reduce fuel consumption. The direct rolling facility has high-power mill motor and roller table with heat-cover which connect continuous casting and roughing mill. The high-power mill motor was necessary for low-temperature rolling. At the same time, billet scale was updated for the purpose of preventing weight unevenness of billet.

2.Company profile

Godo steel, Ltd. has three works located in Osaka, Himeji, and Funabashi with community-based managements. Funabashi works produces deformed bars (reinforced bars). The production totals about 400,000 tons per year.

3.Profile of Direct rolling mill

3.1 Design concept

① Without reheating facilities.

② Prevent temperature decrease of billet in continuous casting facilities.

③ Enhance the mill performance corresponded to billet temperature decrease.

3.2 Outline of installation construction

In March 2007, rolling mill and cooling bed were renewed. In September 2008, a conveyor facility was installed, which conveys billets from continuous casting facilities to heating furnace directly. Based on the data of this facility operation, a direct rolling facility was designed. The construction took 16 days, and the facility was put into operations in September 2010. Fig.1 shows the layout of the facility.

3.3 Outline of facility

In order to reduce the billet temperature decrease at the downstream operation after shearing at continuous casting facility, a table was set up with a built-in roller cover with ceramic fiber insulation. In addition, a branch was set up in the conveyor table from the continuous casting machine to the reheating furnace charging line, which enabled billets to be conveyed directly to the rolling mill. In order to accommodate the increased load due to billet temperature decrease, No. 10 (8th pass) mill stand motor output was enhanced from 650kW to 950kW. Table .1 shows the specifications of the direct rolling facility.

Continuous casting facilities

Direct rolling facilities

Reheat i ng f u r n a c e

Fig.1 Layout of Direct Rolling Mill

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Table.1 Specification of direct rolling facilitiesFacility Specification

Run out table-roller Billet size:130square× 12m6strandsCovered with ceramic fiberMax speed:27m/min

Direct transport table-roller Length:36.9mCycle-time:37sec/pieceProductivity:150t/h

No.10 (8th pass) Mill motor AC950kWRotation velocity:800/1,500rpm

Fig.3 Power consumption (Assume the results 100% at 2010-2Q) 4.Results

4.3 Yield rate 4.1 Reduction of fuelconsumption

At the outset of the direct rolling equipment installation, billets had been rolled from the hot side edge, due to the insufficient space in the layout. The variation in tolerance resulted from the temperature difference of above 80 degrees between the tip and the rear edge of a billet; consequently, the yield had deteriorated. Therefore, by reversing the direction of rotation, billets were made to be conveyed in swivel table, and the layout insufficiency was solved. This solution enabled billets be rolled from the cold side edge. As a result, billet temperature difference was reduced to 40 degrees, and variation in tolerance was improved equivalent to the operation with heating furnace. Fig 4 shows the temperature distribution for the longitudinal direction of the product.

The installation of a direct rolling equipment greatly reduced fuel consumption. Fuel consumption at the time of direct rolling has fallen to zero. However, reheating furnace is still used only for stock billets and for billets produced during rolling facility troubles. The fuel consumption was abled to be reduced to 25%, compared to previous direct rolling. Figure 2 shows the changes in fuel consumption.

Fig.2 Fuel comsumption (Assume the results 100% at 2010-2Q)

4.2 Reduction of power consumption

Electric power of the hydraulic pump and the combustion blower and the compressor has been reduced with diminished use of reheating furnace. This electric power reduction has exceeded the power consumption of rolling mill equipment and direct rolling facilities. The electric power consumption was reduced by about 10%, compared to the previous installation. Figure 3 shows the transition of electric power consumption.

Fig.4 Changes of material temperature

5. Issues to be addressed in the future

Significant production cost reduction has been able to be achieved by the installation of direct rolling equipment. In the future, the yield aims to be further improved in order to reduce the variation of billet temperature.

Page 100: 2-page abstracts booklet

Outline and Operating results of the first Heavy Duty

Reducing & Sizing Block (RSB) in France

Jean-Yves Vernedal (ASCOMÉTAL)

Mathieu Gilles (ASCOMÉTAL)

Stefan Schwarz (Fr. Kocks GmbH & Co KG)

1. INTRODUCTION

ASCOMÉTAL is one of the main European producers of high quality bars particularly for automotive industry.

In 2007, ASCOMÉTAL decided to revamp its Bar Mill in Hagondange to give a better answer to this very rigourous and demanding market (shorter delivery time, important variation of the lot sizes, highest quality standard, and competitive price) The aims of this modernization were:

- to obtain a better flexibility of the bar mill (supply any requested diameter in a shorter time) and simplify the products flows to lower inventories

- to increase the diameter range (Ø16-80 mm.) up to diameter 100 mm

- to simplify or eliminate operations at finishing shop (heat treatment, straightening, peeling, inspection,...)

and thus to reduce the operating costs of the Hagondange plant.

2. SCOPE OF THE MODERNIZATION PROJECT

The exit of the mill (finishing mill and cooling facilities) has been completely redesigned and the rolling mill bay considerably extended.

The order was placed with the Italian company DANIELI & C. OFFICINE MECCANICHE SpA, while the finishing mill was supplied by the German company FRIEDRICH KOCKS GmbH & Co KG.

The electrical equipment and automation for the finishing mill was supplied by Danieli Automation SPA.

The new line starts after the existing 6 H/V intermediate mill and includes :

- 5 stand Heavy Duty 3-roll RSB 370

o able to roll diameters 16 to 100 mm with 8 feeders (simplifying pass design of roughing and intermediate mill),

o high flexibility (size change within a free size range within 1 min, by stand change within 5 min.)

o size accuracy better than ¼ Din 1013

- combined cooling bed shear

- cooling bed with 3m straightening grid and adjustable hooding

o straightness of the bars at the exit of the bar mill better than 2mm/m

o control of the cooling rate

- 3 abrasive cutting machines and associated wheeled stops

o length accuracy (+0, +50 mm)

- finishing facilities

LAYOUT ASCOMÉTAL

Bar Mill with Reducing & Sizing Block (RSB) Technical Data: Furnace capacity: 90 t/h Billet Size: sq. 240mm Weight: 1.720 kg Finished sizes rd. 16 – 100mm Rolling speed: 15 m/s Material grades: alloyed steel, bearing steel,

carbon steel, spring steel

Further controlled rolling developments have been prepared.

A central component of this modernization was the installation of the 5-stand KOCKS 3-roll 370mm Reducing & Sizing Block [RSB] in Heavy Duty Design, which replaced the existing four-stand 2-high finishing line as well a 3-stand 500mm Kocks Precision Sizing Block [PSB].

This block with non-adjustable stands has been operating successfully in the same works since its commissioning in 1992.

Page 101: 2-page abstracts booklet

Allowable roll separating forces: + 45 % 3. 370MM KOCKS HEAVY DUTY REDUCING & SIZING BLOCK (RSB) Allowable rolling torque: + 54 % Max. bar diameter: + 25 % The main differences compared with the replaced 3-roll Kocks Precision Sizing Block (PSB) are:

4. OPERATIONAL RESULTS AND COMMENTS AFTER 4 YEARS - C-Module drive system; each C-module is

individually driven by a separate motor and reduction gear set 4.1 Modernization results

The operational results can be summarized with following features: - the stands are adjustable, and each roll is

individually driven, which means no more bevel gears as before - All finished bar products show highest

tolerance accuracy, better than ¼ DIN EN 10060 (DIN 1013) - grease lubrication replaces the expensive oil

circulation. All the stands are identical and can be operated in all stand positions - Stepless free-size rolling for any size between

rd. 16 and rd. 100mm leads to a high reduction of peeling costs in the down-stream process

- the block is operating as a reducing and sizing unit

- thanks to quick roll changing: no need to machine the rolls in the stands by means of a special turning lathe

- Free size rolling leads to reduce number of passes and flexible production of small lots through multi-cycle rolling (average time for size changing decreased and size changes per month increased)

- therefore no need to roll from smaller to bigger sizes

- The flexibility of the mill being given by free-size rolling leads to a drastic reduction of inventories

- new "free-size" pass design

- computer-aided adjustment system for stands and guides (in roll shop)

- one-pass-family rolling throughout roughing and intermediate mill feeding the RSB

4.2 Rolling operation

From the very first bar and on the complete diameter range, ASCOMÉTAL has been able to roll immediately saleable products with the new Heavy Duty RSB and to reach 1/4 DIN EN 10060 (DIN 1013).

The Heavy Duty RSB is a further development of the well-proven RSB 370mm in flange-type execution.

The challenge of the new development became to keep the roll diameter of the stand as small as possible but reaching maximum rigidity of the stands while keeping the minimum roll ring size. As a consequence 370++ stands (oil pressure shrink fit type) have the same outside dimensions as the conventional stands (axial clamping by flange) of the same size and can be inserted in the same stand support as used for the conventional stands.

The Reducing & Sizing Block meets all the expectations concerning operational liability and performance.

However, it has to be admitted, that the operation of a new RSB 370 with 5 adjustable stands and a total reduction of approx. 64% is completely different as compared to the previous PSB 500 with 3 non-adjustable stands and a total reduction of approx. 15%.

This especially relates to the application of the free-size rolling concept, optimization of roll usage with higher wear and respective roll shop procedures requiring know-how and understanding by the operators and staff of the rolling mill.

5. SUMMARY

The targets of the retrofit of ASCOMÉTAL`s Bar Mill in Hagondange were all fulfilled. Besides an excellent finished quality the operating costs and the economy of the mill could be reduced, while rolling with smaller lot sizes and an increased number of finished sizes. This enhanced development leads to following results:

Page 102: 2-page abstracts booklet

The closed loop size control system in combination with the advanced 3-roll PSM® at DEW

Siegen-Geisweid

Dr. Thomas Helsper (DEW, Siegen-Geisweid) Jens Eisbach (DEW, Siegen-Geisweid)

Günther Schnell (SMS Meer, Mönchengladbach)

In 2006 the world wide first 3-roll block for SBQ production with adjustment under load feature was placed into operation at Deutsche Edelstahlwerke (DEW) Siegen-Geisweid/Germany.

The new 3-roll Precision Sizing Mill (PSM®) with six stand positions has replaced two existing 3-roll blocks of the first generation. The great key features of the advanced 3-roll technology can be summarized as follows:

adjustment under load

rolling force detection

single roll ring positioning

free size rolling

single pass family rolling

quick stand change

The combination of such features opened up operation possibilities in most modern SBQ production which were so far not available on the market. After the implementation of the new 6-stand PSM® the operation of the mill line could be drastically simplified due to the outstanding key features and flexibility of the advanced 3-roll technology.

The production portfolio at Siegen-Geisweid works comprises more than 300 different special steel grades. More than 120 different sizes in a range from Ø22-85mm are rolled whereas several size changes from large to small diameters and vice versa are carried out during a monthly rolling sequence.

From time to time highly sophisticated grades with lot sizes of one or two billets must be even rolled on short notice. Before the PSM® such production flexibility was unthinkable. Taking all that in account, a production increase per operation hour of 7% since the installation of the PSM® is quite impressive. Today the monthly availability of the mill is 89% and the installation of the PSM® can be considered definitely as a great success.

In order to further expand the capabilities of the advanced 3-roll technology, SMS Meer and DEW successfully implemented in joint cooperation a highly dynamic closed loop size control system for the PSM®.

Meergauge®

The MEERgauge® is a fully automatic size control system. It is able to directly react online under load on real time measured deviations from the target size. It interactes in closed loop mode with the hydraulic gap adjustment system of the PSM®.

The basis for the closed loop operation is the adjustment under load capability. This is realized by the advanced design of the 3-roll cassette in combination with three hydraulic cylinders.

An online measuring system at the exit side of the PSM® operates on the basis of the light cut technology. Based on laser/image technology four sensors measure synchronous and contact free the entire cross section of the bar.

With a scanning rate of 500 scans per second a true-shape cross-section is established of up to 400 measuring points and displayed with highest precision.

During operation rolling loads are transferred via hydraulic cylinders into the stiff housing and due to the inimitable design concept of the PSM® wear and maintenance is reduced to an absolute minimum.

Entry side 3-roll PSM® at DEW Siegen - Geisweid

PSM® 3-roll cassette

MEERgauge® at the exit side of the 3-roll PSM®

Page 103: 2-page abstracts booklet

The essential characteristic values of the individual measurements are sent to the Technological Control Centre (TCS®) of the PSM® via a direct process field bus connection in real time. The TCS® logic analyses the values and assigns relevant adjustment set points for gap corrections if required.

With the MEERgauge® due to a combination of a highly dynamic control system and a true-shape measuring system, fully automatic rolling operation of the PSM® could be successfully realized - independent from the operator.

Operational Results

Since the beginning of 2012 the closed loop size control system has been in successful operation - interacting with the new precise true-shape measuring system. The commissioning was uneventful and shortly after start up expectations about the system have already been exceeded.

Thanks to the advanced automation level and reliability of the PSM® excellent results across the whole size range can be reached in fully automatic mode independent of the skill/experience of the operators. Recent achievements are shown in the following screen shots.

Based on the advanced 3-roll cassette characteristics the roll gap adjustment system can adjust all three rolls but in case it is required is also able adjust individually only one or two rolls. Thus symmetrical as well as unsymmetrical positioning adjustments of individual rolls under load offer possibilities for fine optimization of the net shape tolerances.

Outlook

Thanks to the great flexibility of the PSM® an alternative production mode is under evaluation at DEW. Different steel grades are grouped based on reheating and in-line water cooling requirements within the free size rolling mode to minimize downtime. Today it is common practice at DEW that rolling lots are grouped according to (similar) finishing sizes and rolled in a sequence with minimum setup changes in the mill independent from the steel grades. But this requires certain heating procedures and waiting cycles due to free zones in the reheating furnace. This increases substantially the specific gas consumption and also creates mill downtime if water cooling facilities must be reconfigured for steel grades with different water cooling requirements from the sequence. Thanks to the free size rolling capability of the PSM® and the closed loop control, special steel grades with substantially different spreading behaviour can be rolled out of the same groove just by pass adjustment, achieving the required tight tolerance and with minimum downtimes in the mill. Thus specific production costs can be minimised by reduced gas consumption and production can be further increased due to decreased down times.

Conclusion

The advanced 3-roll technology represented by the PSM® offers unique operation possibilities based on the adjustment under load capability. Full process transparency during rolling supports the operators to achieve reliable and reproducible excellent results. The MEERgauge® was the next evolutionary step to a most modern automation level to react on-line under load on varying rolling parameters. Wear of rolls, variations in feeder sizes, temperatures and steel grades fed to the Precision Sizing Mill® can be compensated fully automatically by the closed loop control independent of the operators.

The close cooperation and joint efforts of technology provider and technology user made the installation a great success. Further joint inventive ideas and solutions for highly economic production with the highest flexibility are under consideration.

Light-cut sensor arrangement and true-shape cross section display

Screenshot PSM®:

rolling Ø22mm

Screenshot PSM®:

rolling Ø80mm

Page 104: 2-page abstracts booklet

Revamping of ASCOMETAL Fos sur Mer Wire Rod Mill

Fabrice Lecouturier (ASCOMÉTAL)

Jean-Yves Vernedal (ASCOMÉTAL)

Bertrand Onde (ASCOMÉTAL)

Agnieszka Borysowicz (FIVES STEIN)

Lorenzo Cavaletti (SMS Meer)

Arne Olsson (SUND BIRSTA)

1. INTRODUCTION

ASCOMÉTAL is a major European player active in the following markets: Automotive, Bearings, Spring, Oil and gas and Mechanics.

Fos sur Mer plant produces (from ingots up to 7.5T) blooms and billets (square 50 to 400 mm), and bars (round 80 to 325 mm) as well as wire rod (5 to 14mm), bars in coil (14.5 to 32 mm) and drawn wire.

In 2009, ASCOMÉTAL decided to revamp its Wire Rod Mill in order to be able to deliver coils up to 1.8T weight instead of 1.1T. As a consequence, the billet size had to be increased to 140mm square (from 110 mm)

The aims of this modernization were: - to be able to roll coils (diameter up to 16 mm)

from 140 mm square billets for springs - to improve economical competitiveness of the

wire rod production

2. SCOPE OF THE MODERNIZATION PROJECT

The Wire Rod Mill has been completely redesigned due to the increased cross section and weight of the billets:

- Modification of reheating furnace and charging table

- Modification of roughing mill and removal of 2 stands at the entry of the Intermediate mill to ensure decoupling of roughing and intermediate mills

- New crank shear and new induction furnace at the entry of the intermediate mill to compensate temperature drop between head and tail

- Replacement of the entire Garret line - Modification of the Stelmor line (laying head,

new collecting station) - New handling system and new compactor to

obtain heavier and more compact coils

3 orders were placed with: - FIVES STEIN for the furnace revamping - SMS Meer for the roughing mill modernization - SUND BIRSTA for coiling, handling and compacting equipment.

As can be seen in this picture, most of the mill was modified but there was few interaction between the 3 different parts

FIVES STEIN SMS MEER SUND BIRSTA

The main orders were placed in December 2009 and the commissioning of the new mill was planned in January 2011. Only 2 production stops (3 weeks in August 2010 and 4weeks in January 2011) were possible..

3. FIVES STEIN PROJECT

3.1 Layout and scope of supply

The transformation of the furnace was divided into two phases:

• - Handling part in August 2010: new charging and discharging rollers, hydraulic modifications and reinforcement of the beams, and automation system

• - Heating part in January 2011 including the suppression of roof nose, enhancement of product heat pattern through modification of combustion system (power distribution and burners), new heat recuperator, new automation system for heating and level 3 system Heating Optimization Terminal (HOT).

3.2 Special features of this project

Advanced technologies have been introduced during this revamping including:

- new PC based level 3 HOT - new heating and handling automation

systems with security PLC solution, integrating all automatic operations and securities in line with the latest standards. In particular, automatic positioning system of discharged billets based on 3 laser detectors.

SAFETYHANDLING

Working stations Redondant servers HOT

Page 105: 2-page abstracts booklet

- transformation of the existing roof burners into the new generation of Advantek® low NOx burners.

The main challenges were managing all necessary construction and process modifications in very tight schedules. Very little time was left for cold and hot commissioning.

4. SMS MEER PROJECT 4.1 Layout and scope of supply

The project consisted in complete revamping of the 35 year old roughing mill area. SMS supplied the following equipment: descaler, 2 new HL stands, insulated roller table, nose and cobble shear, induction furnace. 2 old stands were repositioned at the entry of the intermediate mill.

4.2 Special features of this project

Revamping of a 35 year old mill meant a lot of risks (drawings not always updated) particularly for the relocation of old stands and the electrical/automation part. These risks have been overcome thanks to a very detailed analysis.

Two important area modifications for the new equipment (dismantling and casting of new foundations) were achieved, mostly with the old mill in operation. There were only 2 short shut-downs

Automation of the complete roughing mill including the old existing stands was carried out.

An equalizing SMS Elotherm Induction Furnace was installed behind nose and cobble shear 5. SUND BIRSTA PROJECT 5.1 Layout and scope of supply

This project is the largest project supplied by Sund to date. It includes Garrett equipment from Danieli Morgårdshammar, a control system for the Garrett supplied by Danieli Automation, coil distributor with collecting station on the Stelmor line, a combined vertical/horizontal SUNDCO coil handling system, trimming station, a soaping station, a coil compactor PCH-Alfa, weighing and unloading stations.

5.2 Special features of this project

For Sund this project is the most important reference of a turn-key project: main contractor supplying equipment from other companies within the Danieli group, in charge of erection and commissioning, with a particularly short project period Some specific technical problems were solved:

- High temperature of Garret coils: the well-proven SUNDCO-V/H system was adapted to withstand the intense heat without deviating largely from the standard one. - Compactness ratio length/weight below 0,7: this ratio was achieved by using state-of-the-art distribution technology, lubrication in a soaping station and finally by pressing the material in the new PCH-Alfa coil compactor

6. ASCOMETAL PROJECT MANAGEMENT

The most difficult points in the management of 3 different suppliers (in fact 4 with Civil engineering) were: - to remain equally focused on all suppliers, which was difficult to manage particularly during civil engineering period. During the last shut-down, schedules of all the suppliers were checked by the same person in charge of planning. - to optimize the use of the only overhead crane ot the mill for handling activities: a manager was assigned for coordination and hiring of specific means - to be able to read correctly all the detailed functional analysis which arrived at the same time

7. RESULTS

Safety: There was no accident requiring time off during the approximate 100000 working hours; only 8 minor accidents

Planning: Priority was given to the Stelmor line and the first billets were rolled on time (January 27th). Garret line was started 1 month later and optimization for diameter less than 16mm was postponed at the end of the year

H PR2

6H 7V 8H 9V 10HVDK R4 VR5 VR3

V PR1 21

H H 4H 5V V0

2 CV

3V

VR1 FI

FR Automation

Roll Shop

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Ramping: since the mill had been almost entirely modified, ramping went on further than end 2011:

- the new processes (heating, rolling, coiling,..) had to be tuned step by step with a specific concern for product quality

- the operators had to learn about the new equipment and particularly automation

8. SUMMARY

This project was an important challenge for all parties, considering the short schedule for the complete revamping of a 35 year old rolling mill.

We can now consider it has been a big experience and success for everybody.

Page 107: 2-page abstracts booklet

Improving reliability of mill drive gear boxes at New Bar Mill, Tata Steel

Rajeev Malhotra, G.R.P. Singh, M.N. Shukla, P.K.Banerjee, B.K. Das

Introduction:

Gear Box is the heart of any mill drive and any outage can result in heavy loss as the down time cost in present day high production unit is very high. With advancement in Gear Design, Gear Boxes are getting smaller and smaller for a given horse power rating resulting in much more aggressive surface loading in the Gear Boxes. While this reduces frictional losses and improves efficiency, it tends to run hot, increasing the need for managing the lubricant more effectively.

The gearboxes are subjected to:

Continuous heavy loads associated with frequent shock loads. High-speed operations Harsh working environment like temperature / dust / fumes. The load fluctuations in process equipment due to operational requirements may

cause the gears to work in boundary lubrication regimes. This needs very reliable design, operation and maintenance of the gear drives. Due to urge to be competitive, OEMs make the designs very marginal which further reduces the margin of error while operating and maintaining the gear boxes.

New Bar Mill has total 16 numbers of Mill Stand reduction gear boxes. Right from the commissioning of New Bar Mill, following issues related with Gear Boxes were faced.

Oil leakage from the gear boxes Foaming in the gear oil High vibration levels, teeth damage etc.

This set the maintenance group to take a holistic look at the whole system for improvement.

Analysis & Corrective Action:

Stage 1: In stage 1, following maintenance practices were adopted to overcome the problems mentioned above which were suspected to be because of marginal design of gear boxes.

1) TBM implementation: By taking the inputs from previous failures in the gear boxes, a TBM schedule was made for overhauling of mill stand gear boxes based on inspection and condition monitoring to avoid breakdowns.

2) Implementation of daily management to monitor the health of gear boxes to detect any abnormality in the gear box so that timely action can be taken.

3) Specially designed inspection of gear boxes is done at every three months frequency by expert agency to know the conditions of bearings and gear teeth profile.

A Check Sheet for Mill Stand Gearboxes and Abnormality Action Plan is shown below.

Page 108: 2-page abstracts booklet

Stage 2: In Stage 2, an analysis was done to find out actual safety factor (considering actual torque) in all the mill stand gearboxes. Study showed that most of the gearboxes had very low safety factors (ranging from 1.02 to 1.80). Based on discussion with OEM, it was decided to increase safety factor to >2 in all the gearboxes. Gearboxes of Mill Stand 3,4,9,10,15 and 16 have already been changed and other gearboxes will also be upgraded in due course of time.

Centralised Lubrication System Design was also evaluated and it was found that oil was having dwell time of only 20 minutes against minimum requirement of 30 minutes leading to foaming of oil. It has been decided to increase the oil retention time by increasing the tank size of lubrication system (under implementation).

Results:

All the above actions have resulted in Zero Delay because of Gear Boxes in the Mill.

Page 109: 2-page abstracts booklet

Latest Developments in Drawing and Peeling Technology

K. van Teutem

Executive Product Manager

P. Maresch Peeling Process Technology

(Danieli & C Officine Meccaniche SpA)

HIGH SPEED CHAIN TRACK DRAWING OF STEEL BARS OF DIAMETER 4 TO 25 MM: Traditional Cam Based Technology Limitations To calibrate hot rolled steel in coil format, coil to bar drawing lines traditionally make use of a reciprocating carriage pulling system to pull the rolled material through a drawing die. The carriages are driven by means of a rotating cam that engages the lower supports of the carriage. Gripping jaws that are hydraulically controlled are mounted on the carriages to “handover” the material from one carriage to the next. The main limitation of this system is that the speed of the drawing action is limited by the maximum speed of the reciprocating motion of the carriages. Material production drawing speeds of up to 100 metres/min are normally possible, with peak speeds of up to 150 m/min for limited periods (within the normal process limitations of drawing for each particular material). Another drawback of this system is that during the “handover” when one drawing carriage releases the material to be gripped by the next carriage, a substantial material speed variation is experienced. Chain Track Innovative Drawing Technology By replacing the traditional cam based pulling unit with a chain track pulling unit (see figure), the pulling speed of the material is virtually unlimited by the mechanical constraints of the pulling system. The only limitation becomes the maximum speed allowed by the drawing process, which is determined by the drawing area reduction, material yield strength, die design, die lubrication and hot rolled material tolerance. In this way, material drawing speeds of up to 200 metres/min for ferrous materials have already been achieved (and 500 metres/min for non ferrous

applications). Furthermore the constant speed pulling action guarantees a greater cut to length precision (0 to + 2 mm) in the flying shear unit placed downstream of the drawing unit.

TIME

DRAW

ING

SPE

ED (m

/min

)

150

200

2-4%

1st carriage pul

1st carriage pull

2nd carriage pull

2nd carriage pull

80

1st carriage pull

2nd carriage pull

1st carriage pull

2nd carriage pull

1st carriage pul

6-8%

The net result is a higher productivity of the combined drawing line due both to the increase in drawing speed and also to the reduced maintenance required by the constant speed chain track system relative to the reciprocating cam type pulling system.

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IMPROVEMENTS IN PEELING TECHNOLOGY: While cold-drawn material can be produced in many sections, (round, square, rectangle, hexagon or special shapes) peeling and center less grinding can only produce round shapes. Contrary to the drawing operation, surface defects can only be safely removed by peeling. Work hardening, which often is unwanted for further processing does not occur after peeling. Therefore peeling is an attractive process for producing wires even when drawing will reach a higher output. In the range of diameter bigger than 50 mm in any case drawing is not successful because of increasing forces. There is no really economic alternative to peeling in the case of producing rods with close diameter tolerances. The target of diameter tolerance, which has to be reached by a peeling process, is usually IT9. With special arrangements and under well conditions IT 8 is achievable for a lot of materials, but often with reduced productivity. The achieved roundness is about 30% to 50% of the diameter tolerance.

Roughness after peeling and straightening A surface roughness of Ra = 0,75 μm up to 1,5 μm normally can be achieved. With a subsequent straightening operation by a two roll straightener the surface quality will improve down to Ra = 0.15 μm to

0,3 μm generated by the polishing effect. However the straightening will downgrade the diameter tolerance because the plastic forming normally will cause a growth or thinning of the material. Even the peeling

result is able to perform tolerances of IT8 the straightened and polished diameter only meets IT9 quality. Improving the diameter tolerance by additional operations, such as grinding, will raise the costs. If grinding is used as an in-line operation the production speed is ten times less than peeling. Off-line processing with numerous grinding machines will require enormous costs for investment and operating. Therefore improvements of the peeling process itself are necessary to step forward to higher quality. When grinding the peeled material afterwards the improving of tolerance will reduce the number of passes required for grinding and will lowering the overall costs But before taking action for improvements it is absolutely essential to understand the technical and physical reasons for the appearance of diameter tolerances and roundness deviations. In the following the results of the latest research are briefly described and specified, which design features are incorporated during the development of our new generation of peeling machines.Compared with the stiffness of the bar (ideal stiff guiding were assumed) for diameter below 150 mm the tool stiffness is in the background and the bar will determine the stiffness of the complete system. In between 150 mm to 250 mm both components are affecting the resulting stiffness in a similar share. For diameter over 250 mm the tool system itself is limiting the stiffness.

Bar Tool system

Resulting stiffness

The conclusion is, that high stiffness of the tool system (tool holders and adjusting mechanism) and the bar guiding units is critical to reach the highest end quality bar tolerances. To increase the stiffness of the bar itself the guides have to be placed to the cutting tool as close as possible when processing bar diameters less than 30 – 40 mm. Processing bigger material the stiffness of the guiding design is more important than the need to maintain short distances.

Page 111: 2-page abstracts booklet

Major Improvements of the Piercing Mill at Vallourec

Pierre Roblin (GE’s Power Conversion

business), Guy Muzard (GE’s Power Conversion business),

Jean-Paul Brancart (Vallourec)

INTRODUCTION Vallourec is a world leader in premium tubular solutions primarily serving the energy sector, as well as other industrial applications. With over 22,000 employees, integrated manufacturing facilities, advanced R&D, and presence in more than 20 countries, Vallourec offers its customers innovative global solutions to meet the growing energy challenges of the 21st century. Vallourec has a tube works in Aulnoye-Aymeries, North of France (under the name of Vallourec & Mannesmann Tubes). Their Piercing Mill is used to pierce steel rounds which are first heated at about 1250°C.The mill was originally commissioned in 1930. This paper describes the recent modernization of the Piercing Mill, in order to meet the latest requirements of the industry. The modernization project was undertaken by GE’s Power Conversion business (hereinafter referred to as Power Conversion). The project’s scope included electrical upgrades, i.e. the re-motorization of the Piercing Mill with a power increase, and a move to variable speed drive technology.

The main installation work took place in August 2011, with commissioning and product tuning continuing through to the beginning of September 2011.

VALLOUREC’S OBJECTIVES

Vallourec’s long term aim is to develop “premium” products and widen the feasibility of alloy and high alloy products. These objectives will be realized over 3 phases. Power Conversion’s modernization project implemented Phase 1 of Vallourec’s objectives which are summarized as follows:

• Improve product quality: by improving tolerance, reliability and process control

• Raise productivity

• Develop new products: equipment sized for future products e.g. 425mm diameter rounds

• Reduce energy consumption

• Enable new functionalities for better process management, such as:

o Low speed at the start of the motor, and threading speed when the product enters the stand (see fig.2)

o Control of the transition from threading to nominal speed, even with the most restrictive product

o Reduce time to stop the motor

o Control of the torque during the different phases of the rolling

o Communication with the existing automa-tion system

• Improve motorization of the Piercing Mill by replacing the old fixed speed AC motor with a variable speed AC induction motor (higher power) with Medium Voltage drive system.

PROJECT MANAGEMENT Power Conversion provided a turnkey project, including technical leadership with responsibility for the design, specification, review, inspection and planning of all aspects of the project, excluding civil works. Power Conversion also led the commercial responsibility of the contracts with local sub-contractors for cabling and installation of the new equipment. Power Conversion’s prime responsibility remained the achievement of the performance parameters and the project timescales. After the commissioning phase, Power Conversion provided its remote maintenance system, VISOR, associated with a maintenance contract in order to guarantee the optimum operating of the mill. TECHNICAL SUMMARY Upgrade of the Piercing Mill:

• Replacement of the old motor by an induction Motor 8500 kW 1500 rpm, able to be mounted at the same place as the old one (the old motor can be reused if necessary). Overload capacity requirements: 1.5 time nominal torque

• New IGBT 3.3 KV Converter type MV7312 24 pulses configuration (max current 3200A) to supply the new motor

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CONCLUSION • New Transformers (2) - Primary : 10500/21000V Secondary : 2x1900V Rating : 5 MVA each The electrical modifications of the Vallourec’s Piercing

Mill have been completed as planned. Vallourec is very satisfied with the quality of the achieved products, which match their expectations. The “difficult” products were rolled without defects and the mill is ready to process new products.

• New High Voltage Cells (2)

• New Braking Resistor

PROJECT IMPLEMENTATION The project objectives were reached thanks to the

close cooperation between the project teams of Vallourec and Power Conversion, the main contractor.

Planning and design were jointly developed by Power Conversion and Vallourec’s project teams during the course of the project.

The project was launched in December 2010 and the requirement specification phase started, with the aim of collecting all the information required for hardware and software procurement and design.

The motor was designed by Power Conversion according to the Piercing cycle delivered by Vallourec. The design, code and test period for the new equipment were completed in a six months period. Vallourec witnessed a complete Factory Acceptance Test (FAT) in June 2011. All new electrical equipment were manufactured, tested, proved and delivered on site in June and July 2011. Figure 1 – Picture of a produced tube This installation work was implemented during the production phase of the mill, except for the high voltage cabling, and commissioned without affecting the normal rolling operations. In this way, the system was largely pre-commissioned with real plant signals, allowing a high degree of confidence before the shutdown.

The motor was installed and connected during the shutdown of August 2011. The duration (2 weeks) and detailed activities of this shutdown were planned jointly by Power Conversion and Vallourec. Mill start-up, on 24 August 2011, was achieved on schedule. The production resumed immediately with an improved quality. Figure 2 - Piercing cycle

PERFORMANCE AND QUALITY ACHIEVEMENTS Guarantees were provided to V&M for each key product quality parameter: - product quality - cycle times and production rate control - installation reliability A rapid improvement of the settings was achieved since the total product range has been processed.

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Session 8: Coating and finishing line

Table of Contents

8.1 New developments for hot- and cold-strip processing lines H.G. HARTUNG, L. KÜMMEL, C. SASSE (SMS Siemag), Germany

8.2 Side trimmer with Dynamic Width Adjustment system (DWA) T. VALLÉE (Siemens VAI Metals Technologies), France

8.3

Electromagnetic strip stabilization: eMASS® – results, experiences, and future objectives out of more than 30 industrial applications M. IRLE, S. DOMBROWSKI (EMG Automation GmbH), Germany, T. KLING (Nova sarl), France

8.4

Industrial benefits of dynamic air knives implementation on continuous galvanizing lines J.J. HARDY, B. GRENIER (Siemens VAI Metals Technologies), France, S. ÖZER, M. BARAS (Borcelik Celik Sanyii Ticaret S.A), Turkey

8.5

Processing approaches for continuous hot-dip galvanizing of high manganese alloyed steel G. PARMA, M. BLUMENAU, M. NORDEN, T. WUTTKE (ThyssenKrupp Steel Europe AG), Germany

8.6

Control of bake-hardening level and aging properties in a hot-dip-galvanizing-line K. MACHALITZA, R. GERLACH, C. ESCHER¸ M. NORDEN (ThyssenKrupp Steel Europe AG), Germany

8.7

Innovative flameless regenerative burners for direct fired furnaces on hot dip galvanizing line - up to 15 % lines productivity increase C. VILLERMAUX, N. RICHARD, T. BELLIN-CROYAT, G. DAILL, P. BUCHET (GDF SUEZ), K. BEAUJARD, A. DANDA, B. LOUIS, H. SAINT-RAYMOND (ArcelorMittal Global R&D), France

8.8

Continuous performance evaluation of control systems for reducing energy consumption in annealing lines A. WOLFF (VDEh Betriebsforschungsinistitut), M. JELALI (Cologne University of Applied Sciences), Germany

8.9 Simultaneous measurement of strip surface emissivity and temperature (SMOTE) G. KUIPER, F. MUILWIJK, R. VAN BUREN, J. WESSELINK (Tata Steel R-D & T), The Netherlands

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New Developments for Hot- and Cold-Strip Processing Lines

Hans Georg Hartung, Lutz Kümmel, Caesar Sasse

(all SMS Siemag, Hilden, Germany) INTRODUCTION Always adopting the best-technology, SMS Siemag designs its strip processing lines to meet not only today’s standards, but tomorrow’s challenges as well. This presentation will give an overview of the latest developments. These developments ensure that strip processing lines will save resources while also complying with the more advanced quality demands of the future. It will contain information about the following technologies and references:

Hot-strip processing lines - X-pro® laser welding machine - Recuperator tank for turbulence pickling - Reference Example: Continuous pickling line for Tokyo Steel, Japan

Cold-strip processing lines - Concept universal annealing and galvanizing line - FOEN DEMCO strip stabilization - Ultra Fast Cooling system - Water-spray cooling system - Reference example: Hot-dip galvanizing line and universal annealing and galvanizing line for MMK, Russia

HOT-STRIP PROCESSING LINES: X-pro® Laser Welding Machine SMS Siemag developed the X-pro® laser welding machine for hot-strip and received already five orders for this machine. Three machines are now successfully commissioned.

X-pro® laser welding machine

Technologically, the laser welding machines are equipped with a whole range of innovative extras, many of which are unique features:

Welding of hard-to-weld steel grades such as C67 without filler wire

Determination of the weld parameters based on material cast analysis

Patented inductors for inline heat treatment used in welding special steels

Fully automated joining gap adjustment based on gap measurement

Fully automated and controlled laser head positioning according to measurement of the joint position

Recuperator tank for turbulence pickling The strip runs through this patented recuperator tank and is sprayed with waste acid from the pickling process before it enters the turbulence pickling tank. The recuperator tank increases the capacity of a pickling plant. The main reason is that this pre-cleaning removes large scale particles before entry into the pickling tank, so they do not contaminate the pickling acid. Furthermore, the strip is pre-heated and activated in the tank, making the pickling process more effective. In this way, the recuperator tank effectively uses waste acid and also recovers heat before the waste acid is transported to the regeneration unit.

A recuperator tank increases the pickling-capacity

Reference example: Tokyo Steel, Japan The new continuous pickling line for Tokyo Steel was successfully put on stream in August 2011. The highlight of the line is the new X-pro® laser welding machine. In course of the commissioning phase, already all contracted material combination had been joined, including strip with thickness differences of up to 1.5 mm. Furthermore, the line features a turbulence pickling section with recuperator tank and an acid regeneration plant by SMS Siemag. The design and foundations of the plant were made in due consideration of a future coupling with a tandem mill.

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COLD-STRIP PROCESSING LINES:

Universal annealing and galvanizing line

The universal annealing and hot-dip galvanizing line is a further big step towards increasing the flexibility of cold-strip processing plants. In this type of line, the cold strip, after undergoing recrystallization annealing, runs either into a zinc pot or an overaging zone. Thus, the line can be used in a flexible manner while satisfying high quality requirements for two different product groups (annealed and galvanized). This type of plant is characterized by particularly high cost efficiency owing to the enlarged product range and the rapid adaption of production to the requirements of the market.

Water-quench cooling system FOEN DEMCO electromagnetic strip stabilization The FOEN DEMCO system is an electromagnetic strip stabilization system for strip galvanizing lines, which is already installed in five lines. Using inductive measurement of the strip position, the electromagnetic strip stabilization for strip galvanizing lines controls the magnetic forces in such a way that they immediately equalize unwanted movements or shapes of the strip. The adjustment is contact-free in the area above the air-knives that adjust the zinc coating. In particular, the movable outer coils correct cross bows in the strip. In this way the DEMCO system makes high zinc savings possible.

Universal annealing and galvanizing line

Ultra Fast Cooling system The Drever Ultra Fast Cooling system for high-strength steel grades delivers cooling rates of 100 to 120 K/s/mm. This cooling performance is necessary to manufacture high-strength, multiphase, and TRIP steels with yield strengths of up to 1,000 MPa.

The cooling system uses the properties of hydrogen (low density and high heat transfer) to increase cooling capacity. What’s special about the patented Ultra Fast Cooling method from Drever is the direct introduction of pure hydrogen into the cooling chamber. That results in a hydrogen content of 20 to 30% inside the chamber, enabling the high cooling performance. Due to the natural diffusion of the gas into the other areas, there is no need for a complicated separation between the cooling and the neighboring zones. That means the process does not use any more hydrogen than conventional furnace operation, with 5% hydrogen in the protective gas.

FOEN DEMCO system in operation with five magnets Reference example: MMK, Russia For the new cold strip complex of MMK in Magnitogorsk SMS Siemag has built some rolling and processing facilities - among them a hot-dip galvanizing line and a universal annealing and galvanizing line. This both lines are able to process more the 1 million t of cold-strip per year. A point to be stressed here is the wide range of materials from soft to high-strength grades. The lines feature Drever furnaces with Ultra Fast Cooling systems and FOEN DEMCO strip stabilization systems. Both lines are operating since June respectively July 2012.

Water-quench cooling system The manufacturing of ultra-high-strength steel grades – especially martensitic grades – requires cooling rates of more than 120 K/s/mm. The only way of producing these steels is to integrate a water-quench cooling system for rapid cooling after annealing. Water is sprayed onto the strip in a nozzle chamber for very high cooling rates. A special slot-nozzle configuration ensures even cooling over the entire strip width. That prevents flatness deviations, strip distortions, or faults. Anti-crimping rolls upstream of the nozzle chamber monitor strip shape. This configuration makes cooling rates of more than 1,000 K/s/mm possible, a performance that is necessary for the production of martensitic steel grades with yield strengths of more than 1,000 MPa.

CONCLUSION: Our continuous development of process components and technologies as well as line concepts ensures cost-effective production of high-quality steel strip now and in future. Apart from increased profitability and efficiency of our plants and the manufacture of innovative steel grades, we focus on minimizing emissions and consumption of resources.

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SIDE TRIMMER DYNAMIC WIDTH ADJUSTMENT

(DWA)

T. Vallée (SIEMENS Metals Technologies France)

PARAGRAPH TITLES:

1. FUNCTION OF THE SIDE TRIMMER MACHINE

2. TECHNICAL DESCRIPTION OF THE DWA SYSTEM

3. MAIN BENEFITS & INDUSTRIAL RESULTS

1. FUNCTION OF THE SIDE TRIMMER MACHINE

The aim of the Side Trimmer machine is being used to remove the strip edge defects and to assure a constant width of the latter.

Various processing lines have their own dedicated machines such as:

ST21H (CPL, PPPL, PLTCM) .Heavy load (0.7 to 8 mm / 850 MPA) .Turret Type (45 sec automatic head swap) .Strip driven knife (Continuous process) .AC Motor driven knife (PPPL) .Fast width change cycle (8 sec / 100 mm change) .Ultra precise Gap/Lap (Close loop servomotor) .Ultra fast Gap/Lap (3x high overtorque) .DWA (100 mm / 2m dynamic width change) .Super fast knife change (10 min) .Zero hydraulic

ST21M (CAL, CGL, TLL) .Medium load (0.3 to 3 mm / 850 MPA) .Turret Type (45 sec automatic head swap) .AC Motor driven knife .Fast width change cycle (8 sec / 100 mm change) .Ultra precise Gap/Lap (Close loop servomotor) .Ultra fast Gap/Lap (3x high overtorque) .DWA (100 mm / 2m dynamic width change) .Super fast knife change (10 min) .Zero hydraulic

The Side Trimmer knives go inside the strip thanks to a notch generally done on the weld axis (Fig.2).

As it is installed on continuous process the cycle time and the reliability are critical and must be optimized, particularly on the following points:

Knife change: When knives are worn it must be possible to safely replace them as fast as possible, with the use of “turret type” with 2 embedded cutting heads each side (Fig. 3). The use of servomotor enables to lower the line stoppage time.

Fast and precise width change thanks to servomotor driven preloaded micrometric screw insuring up to 300 mm stroke in 8 sec with a precision +/- 0.25 mm.

Jam: This is a major problem which occurs most of the time when the trimmed edge is very thin during threading. The scrap is no more guided inside the chutes and generates cobbles. This results human interventions and long stoppage on the line.

Fig.1 ST21H Heavy type Side Trimmer body

Fig.2 ST21M Medium type Side Trimmer section

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The cobbles risk is drastically decreased. The trimmed edge becomes continuous and therefore it is always pulled by the scrap chopper.

Conclusion the DWA brings: Reduction of the trimmed edge width Lower the cobbles ratio Lower production scrap Improvement of the production yield of 3%

Fig. 3 Head rotation

2. TECHNICAL DESCRIPTION OF THE DWA SYSTEM

When featuring the Dynamic Width Adjustment “DWA”, the side trimmer no longer stops during a strip width change.

The head frame rotate accurately just under the cutting axis along the width change without unlocking the heads. The cutting angle is controlled by a servomotor (Fig.4).

Fig.4 DWA Mechanical system

Fig.5 E&A system

The new product information (thickness, new strip width, new thickness, weld position, line speed…) are sent by the line material tracking PLC.

According to these values the Side Trimmer PLC generates a motion profile. On every point, it calculates the traverse speed and the cutting angle value in a small cycle time (Fig.5).

The line decelerates between 30 mpm and 60 mpm in the Side Trimmer area and the side trimmer PLC launch the on-fly width change motion according to the weld position (Fig.6).

The DWA can be done up to 100 mm on a maximum of 2 m strip length (Fig.7). The lost strip length is optimised according to the required width change.

3. MAIN BENEFITS & INDUSTRIAL RESULTS Fig.6 DWA Motion The DWA system runs in full automatic mode only and it is operation free. The main advantages are:

The cycle time is improved and the process speed can be increased. This is particularly interesting for line which have a reduce looper size as the strip is never stopped.

It lowers strip break especially on small strip width. The notch can be removed and consequently it’s a big advantage for strip rolling. When the weld will move to the mill, the force will vary smoothly.

Fig.7 DWA 100 mm / 2m

Vertical

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Electromagnetic strip stabilization: eMASS® – results, experiences,

and future objectives out of more than 30 industrial applications

Matthias Irle, Steffen Dombrowski, EMG Automation GmbH, Germany

Thomas Kling, NOVA sarl., France

INTRODUCTION

Homogeneous surfaces and minimal coating thickness at high production outputs are the production targets in hot-dip galvanizing. Electromagnetic strip stabilization became a proven solution in the last 5 years with in the meantime more than 30 installations of the EMG-eMASS® system. Over-coating is drastically reduced and eMASS® ensures a flat, stable strip position between the air knives. The good experiences with electromagnetic strip stabilization based on eMASS® lead to the development of a new concept targeting to the full integration of EMG-eMASS® into the design and mechanics of a state of the art air jet design. This presentation concentrates on the industrial application experiences and results with eMASS® and the concept of the integrated eMASS® solution based on the DUMA air jet system.

BASIC DESIGN

EMG-eMASS® is an electromagnetic system for improving the shape and reducing oscillations of the steel strip production lines in the steel industry.

The air knife uses pressurized air or nitrogen to blast across the entire width of both sides of the strip. The smaller and more even the distance between the air knife lips and the strip, the more advantageous the entire process.

Strip deformations such as C- or W-shapes, passline shifts and overlaid strip oscillations naturally occur based on the properties of the line and the strip material. Due to these strip shape variations in the coating area, in-homogeneities of the zinc or aluminum layer over the strip width and strip length are unavoidable. The air knife system has to take these conditions into account.

The EMG-eMASS® system is to be installed as close as possible above the air knife, usually directly on the existing air knife device, to cover the entire strip width spectrum with its setup. The position and movement of the strip is measured at up to 8 strip sectors. Electromagnets with a dynamically adjustable power amplifier are used to correct and stabilize strip position, strip shape, and to limit strip oscillations.

Figure 1 shows a typical installation directly on the air knife device.

1. Mechanical adaptation to the air knife system

(green brackets) and quick release clamps 2. Cooling air connection 3. Crane lugs 4. Base frame with linear units and internal

servomotors 5. One separate mobile stainless steel housing (air-

cooled) on each side of the air knife 6. Industrial connector

RESULTS OF INDUSTRIAL APPLICATIONS The application of an automatic strip stabilization leads to two major benefits:

• The damping of strip vibrations and by that a much more homogeneous coating profile in longitudinal direction and

• The optimization of the strip shape, i.e. the elimination of the crossbow, leading to a much closer operation of the air knife lips and an optimal crosswise coating profile.

In summary the results of the eMASS® application lead to at least:

1. A damping of >= 50 % measured between the

actuator boxes (for an initial standard deviation of the strip position signals >= 0.9 mm)

2. A strip shape correction which forces the strip to a position constancy of +- 1.5 mm over strip width (for an initial shape deviation of <= +-5 mm over strip width)

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Figure 4 shows the dramatic effects on the crossbow elimination in one of the more recent applications at GalvTech, Pittsburg, USA, 2012 (upper image: eMASS® on, lower image eMASS® off, strip position signals and envelope at actuator level). The envelope of the strip shape was reduced by a factor 3!

SPECIFIC APPLICATION RESULTS

Effects on coating homogeneity over complete coils (Fig. 2)

Application summary

The following benefits of the eMASS® solution have been confirmed so far: • Vibration and damping targets achieved • Standard deviation of coating weight distribution

reduced accordingly • Lower coating weights possible • Air knives can operate closer to the strip (less

nitrogen consumption, less noise, less zinc splashes, less cleaning cycles)

Fig. 2 shows the typical effect on coating homogeneity over a complete coil. With eMASS® turned on the standard deviation of the coating weight is reduced by a factor > 2 (target coating 145 g/sqm/side).

OUTLOOK: THE INTEGRATED SOLUTION (Fig. 5)

In order to get the best out of two worlds the combination of EMG-eMASS® and a leading air knife design is a consequent step in the further technological roadmap. EMG Automation GmbH and DUMA-Bandzink GmbH – the leading provider of high end coating equipment – formed a technology partnership to provide an integrated system solution for the coating industry.

Effects to coating setup (Fig.3)

The integrated system can offer full control of the wiping and coating process using a closed loop control at minimum vibrations to reach minimum coating weights and highest coating homogeneity.

Figure 3 shows the effects on the coating weight targets after the application of eMASS® at the hot dip galvanizing line of ArcelorMittal Columbus, USA, 2010. After set-up of the eMASS® system the target coating could be reduced by 1 g/sqm/side in average, leading to a significant material cost reduction.

Crossbow reduction (Fig. 4) The integrated system (concept Fig. 5) combines four high end technology elements: the DUMA air knife and air jet equipment, the EMG-eMASS® as strip stabilization system, the EMG-eBACS baffle blade control system and the DUMA automatic air knife wiping system. This combination provides the optimum with respect to the coating process quality, process control, and operational safety.

The integrated system eMASS®/DUMA will be available for production use in 2013.

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Industrial benefits of Dynamic Air Knives implementation on

Continuous Galvanizing Lines Jean-Jacques Hardy, Benjamin Grenier (Siemens

VAI Metals Technologies SAS)

Sertaç Özer, Mahmut Baraş (Borcelik)

INTRODUCTION

Borçelik is a joint venture between Arcelor Mittal and Borusan. Located on Marmara sea coast, Borçelik is Turkey’s first private and second largest flat steel producer.

The new continuous hot dip galvanizing line CGL 3 (see Figure 1) is a part of the investment to increase the plant capacity to 1 520 000 metric tons per years. Annual production of CGL 3 is 350 000 t/y for building, appliance and automotive products, with high flexibility. Borçelik granted Siemens Metals Technologies as supplier of this line end 2007.

Figure 1: View of Borçelik CGL N°3

DAK®E TECHNOLOGY

One of the key process equipment is the zinc coating wiping system, called Dynamic Air Knives system (DAK®E) which allows the best characteristics of coating products. This technology permits managing, automatically and on-line, the opening of the lips across the width of the strip. This leads to reach an accurate controlled width homogeneity of the zinc coating thickness.

Main objectives of DAK®E are to save zinc within coating thickness target with lip gap adjustment, to improve surface quality with air cushion and to improve strip weldability with a more consistent distribution on zinc coating. DAK®E equipment is able to control on-line lip profile, air pressure and distance strip/nozzle according to operation and process

condition variation: strip shifting, strip cross-bow and strip section changes. In addition and to improve coating surface quality, DAK®E system is supplied with an automatic lip cleaning, a contactless baffle including an autocentering device.

As seen in Figure 2, customer target is to have a minimum coating everywhere on the strip. So due to the process variations, the mean coating deposited is generally much higher than forecast target. Thanks to the remote lip gap profile supplied by DAK®E system, the coating dispersion across the strip can be reduced (from d1 to d2). Then the mean coating deposited can be consequently also reduced. In addition, coating thickness is also more homogeneous along and across the strip thanks to the Transversal Coating Control with less dipersion observed.

Target with conventional air knives

Coating profile withconventional air knives

Zinc savings

Strip

Zinc

Coating mini requested by the customer

d1 Coating profile with DAK® E

Target with DAK®E

d2

Target with conventional air knives

Coating profile withconventional air knives

Zinc savingsZinc savings

Strip

Zinc

Coating mini requested by the customer

d1d1 Coating profile with DAK® E

Target with DAK®E

d2

Figure 2: Potential performances of DAK®E on coating

profile, compared to conventional air knives

RESULTS OBTAINED ON BORCELIK CGL3

After start-up of the CGL3, numerous jet line issues have been observed, which has lead to downgrading of products. Since the start-up, Borçelik have observed several points which can be improved on the line, as the right and efficient maintenance to do on equipments, especially on key equipment as the air knives. So a high strategy and politic of maintenance has been carried out by Borçelik team on wiping step: Operators skills have been transformed to expertise with a harsh training plus the elaboration of specific maintenance process procedures.

Since the start-up, Borçelik team has improved its knowledge of CGL3 and of the air knives system installed. They reach some production stabilization stages with significant improvements observed on zinc coating targets and tightening measured on coating targets from 2010 to 2012. In the same period, regulation loops and presets have also been optimized according to the product mix (very large in terms of section, products and coating) and the specificity of the line.

As operation example in Table 1, mean weight coating of few g/m² above the mean coating target means that the operators manually correct the setting probably for

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safety results regarding coating performance. So, it was possible to save zinc by reducing this value through a better management of presets by the operators, which has been done on site.

But due to safety reasons to stay above minimum target, Borçelik has decided to apply a reduction of 2% on zinc thickness target which can lead to interesting and significant zinc savings, in the frame of the requested coating thickness tolerances target (as shown in Figure 3).

Real

Coating g/m²/side

Target g/m²/side

Delta g/m²/side

Improvemtg/m²/side

May 2010 59,16 57.43 1.72 /

May 2011 63.61 62.59 1.02 0.7

June 2012 62.27 61.74 0.53 0.49

Total 1.19

With these examples, we have shown that a system like DAK®E proposing remote lip gap profile, we can manage a decrease on zinc coating thickness target. This additional reduction of 2g/m² decided by Borçelik on zinc coating thanks to Transversal Coating Control can lead to an additional reduction of about 120t of annual zinc consumption.

POTENTIALS IMPROVEMENTS Table 1: Improvements observed on zinc coating targets from 2010 to 2012 Among potential improvements, the DAK®E wiping

system can be improved with the addition of: This reduction of zinc coating mean of 1.19 g/m²/side has lead to a better efficiency, as a global reduction of about 140t of zinc consumption (about 1,5-2% of annual zinc consumption depending of the product mix).

- An on-line control to optimize the target in function of coating standard deviation transversal.

- A distance sensor to continuously know the strip position, then to adjust more quickly the air knives horizontal position when the strip is moving (rear – front direction), in case of strip speed & strip tension variation, submerged rolls adjustment and product change.

ADDITIONAL PERFORMANCES OBSERVED THANKS TO DAK®E

To better observe the benefits of the remote gap profile, we have used the air knives system with the Transversal Coating Control (TCC) then we have stopped this control and set up the lip gap parallel across the strip as done with conventional air knives. We can note a mean improvement of about 2.1g/m²/side in this trial during normal operation thanks to TCC.

CONCLUSIONS

Thanks to this new line CGL3, Borçelik can supply the best quality products to his customers in the very wide range of product mix. Furthermore the close and friendly cooperation between Borçelik and Siemens Metals Technologies allows continuous improvements to increase the quality of the products and to get lower operation cost on this line.

Considering global statistical analysis for coatings measurements for several months, we can observe a tightening distribution on coatings between conventional system and DAK®E. It would be possible to reduce the zinc coating target up to 6%. DAK®E air wiping system contributes to these

performances. Thanks to this specific device, Borçelik has decided to lower their coating targets of 2g/m² (2 sides). In comparison with other conventional air wiper system, this equipment of new Dynamic Air Knife generation allows to lower the target coating thickness and consequently to have a rapid return of investment.

80 85 90 95 100 105 110 Coating thickness

Coating Mini - 3σ Conventional Air Knives (100%) DAK®E (94%)

6%

= 100%σ = 6%

= 94%σ = 4%

80 85 90 95 100 105 110 Coating thickness

Coating Mini - 3σ Conventional Air Knives (100%) DAK®E (94%)

6%

= 100%σ = 6%

= 94%σ = 4%

Figure 3: Potential zinc savings

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Processing approaches for continuous hot-dip galvanizing of

high manganese alloyed steel

G. Parma (ThyssenKrupp Steel Europe AG)

M. Blumenau (ThyssenKrupp Steel Europe AG)

M. Norden (ThyssenKrupp Steel Europe AG)

T. Wuttke (ThyssenKrupp Steel Europe AG)

ABSTRACT:

Modern automotive concepts require an enhanced level of passenger safety in combination with a reduced body-in-white weight. In order to serve these needs, high Mn alloyed TWIP steel concepts (15 – 30 wt. % Mn), providing high strength with excellent forming properties, were created. On the other hand, cost-effective hot-dip galvanizing of such manganese alloyed austenitic steels is challenging due to intrinsic surface coverage of compact oxide layers during continuous annealing prior to hot- dipping. Based on fundamental investigations, two processing approaches for improved reactive wetting have been conducted in laboratory studies. In the so-called bright annealing process, at a high annealing temperature and a low H2O/H2-ratio of the annealing atmosphere, external oxidation can effectively be avoided. However, such annealing parameters are far from realistic conditions in production lines. Alternatively, the pre-oxidation process promotes reactive wetting by exposing the steel to an adapted oxidation/reduction treatment while annealing. Therefore, a model, stating reactive wetting on top of a covering MnO layer with dissolved Fe in the metallic state resulting from pre-oxidation, has been proposed. Within the scope of an industrial trial, the pre-oxidation technique for high Mn alloyed steels has successfully been implemented in the continuous hot-dip galvanizing process. Coating characterization of this industrially hot-dip galvanized Fe-Mn-C TWIP steel confirmed the proposed model for reactive wetting of high manganese alloyed steels. The results from both laboratory investigations and the industrial trial demonstrate that the pre-oxidation technique, applied for the hot-dip galvanizing of high-alloyed advanced high strength steels, proved quite promising for series production.

INTRODUCTION:

High Mn alloyed TWIP steel concepts have been designed to provide high strength in combination with excellent forming properties for an application in safety-relevant automotive construction parts. The hot-dip galvanizing process has been chosen to apply a surface refinement implementing a corrosion protection for these high strength steels. Unfortunately, Mn, the most important alloying element for an improvement of the mechanical properties, tends to selectively oxidize at the surface during continuous annealing prior to hot-dipping. Therefore, the application of a cathodic protection coating turns out to be rather challenging due to a hampered reactive wetting [1].

Based on fundamental investigations two processing approaches for an improved reactive wetting have been conducted in laboratory studies. The bright annealing concept aims at a suppression of external oxidation by creating an annealing condition with a high temperature and a low H2O/H2-ratio. On the other hand, the pre-oxidation concept focuses on the reactive wetting by exposing the steel to an adapted oxidation/reduction treatment while annealing.

LABORATORY TRIALS:

For laboratory studies, the sample material was a modern industrial steel grade called X-IP® 1000, which contains about 23 wt. % Mn, with small amounts of other alloying elements. More details about the chemical composition can be found in literature [1-2, 6]. For all annealing and galvanizing trials, an IWATANI SURTECH hot-dip process simulator type V has been utilized.

Bright annealing concept:

In the bright annealing process all samples were heated up with 10 K s−1 to 1100 °C, soaked at 1100 °C for 60 s, subsequently cooled down with ~40 K s−1 to 480 °C as the strip entry temperature, followed by overaging at 480 °C for 30 s prior to hot-dipping. During this close-to-production annealing cycle, the samples were exposed to 5.0 vol. % H2 balanced to N2 at a dew point (DP) of −50±2 °C.

Surface analysis of a bright-annealed sample prior to hot-dipping confirms the absence of external MnO. Only a few insular oxides could be detected along the grain boundaries. The analysis of the coating after hot-dipping revealed that FeZn13(ζ)-phase has formed at the interface steel/Zn(η) coating indicating an hampered reactive wetting despite of the absence of

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external MnO. Therefore, a model explaining the hampered formation of the Fe2Al5 interface layer and the appearance of the ζ-phase has been proposed. Herein, hampered Fe2Al5 formation supposedly results from a local depletion of bath-Al next to the steel surface caused by dissolution of metallic-bound Mn out of the steel surface. The resulting inhibition layer consists of a Fe2Al5 interface layer penetrated by ζ-phase.

Regarding the results gathered in laboratory trials it is proven that a high Mn alloyed TWIP steel can be hot-dip galvanized without coating defects using the bright-annealing concept. However, ζ-phase can be detected within the coating. Additionally, the annealing parameters are industrially not practicable and therefore no further trials have been conducted [2].

Pre-oxidation concept:

The established model of pre-oxidation of alloyed steel grades describes a 2-step oxidation/reduction procedure during continuous annealing. In a first step, the steel strip is exposed to an atmosphere, which is oxidative with respect to Fe, to systematically create a continuous FeO layer on the steel surface. This oxidation step should be conducted during strip heating (at T ≥ 550 °C) before a considerable amount of selectively oxidizing alloying elements can migrate to the external surface. The second step is determined by exposing the strip to an atmosphere, which is reductive with respect to FeO for re-reducing the FeO layer to metallic Fe (Femetal). This reduction step is typically conducted while soaking the strip at recrystallization temperatures in H2-N2. To ensure a complete FeO reduction during soaking, the FeO layer thickness should not be more than ~200 nm. After this oxidation/reduction procedure, the strip is cooled down to strip entry temperature and hot-dipped [3].

If a high Mn alloyed TWIP steel is exposed to such a pre-oxidation treatment, a continuous MnO layer with embedded Femetall (MnO�Femetall layer) can be observed at the steel surface. Interestingly, by hot-dipping pre-oxidized high Mn alloyed TWIP steel into a galvanizing bath, reactive wetting can be obtained on top of this MnO�Femetall layer. Coating quality was significantly improved compared to conventionally annealed samples as well [4-6]. Based on these encouraging results, which describe a change to the paradigm that reactive wetting will fail, if the steel surface is mainly covered by oxides, an industrial trial was conducted.

INDUSTRIAL TRIALS USING PRE-OXIDATION:

The atmospheres in the different furnace sections of a continuous galvanizing line were adjusted to meet the pre-oxidation/reduction conditions known from laboratory trials as close as possible. Resulting from this procedure a GI coating could successfully be applied on high Mn alloyed steel without uncoated areas.

Coating and interface characterization of the produced high Mn alloyed TWIP steel coil revealed that a continuous Mn-based oxide layer appeared at the interface steel/ Zn(η) in a manner similar as had been reported in previous laboratory examinations. The hot-dip coating was completely composed of Zn(η) phase. Coating adhesion tested by ball impact test was good concerning the complete strip width and on both sides of the strip [5]. These results clearly demonstrate that pre-oxidation is a useful method for the industrial hot-dip galvanizing of high Mn alloyed steel grades using the existing plant technology without performing any pre-treatment of the steel strip.

REFERENCES:

1. M. Blumenau, “Schmelztauchveredelung von

hochmanganlegiertem TWIP-Stahl unter Berücksichtigung der wasserstoffinduzierten Rissbildung nach Umformen“, ISBN 987-3-8322-9541-7, Shaker-Verlag, 2010

2. M. Blumenau, M. Norden, F. Friedel, K. Peters, „Reactive wetting during hot-dip galvanizing of high manganese alloyed steel“, Surface and Coatings Technology 205 (10) (2011) 3319

3. S. Zeizinger, R. Leuschner, “Controlled oxidation of advanced high strength steels (AHSS) in hot-dip galvanizing lines”, 27. Journée Sidérurgiques International, 2006, Paris, France

4. M. Norden, M. Blumenau, R. Schönenberg, K. Peters, „Chances and challenges of using pre-oxidation in hot-dip galvanizing of AHSS”, 8th International Conference on Zinc and Zinc Alloy Coated Steel Sheet “Galvatech”, 2011, Genova, Italy

5. M. Blumenau, “Industrial use of pre-oxidation during continuous hot-dip coating of (high) alloyed steels”, AISTech 2012, Atlanta, GA

6. M. Blumenau, M. Norden, F. Friedel, K. Peters, “Use of pre-oxidation to improve reactive wetting of high manganese alloyed steel during hot-dip galvanizing“, Surface & Coatings Technology, Vol. 206, 2011, pp. 559-567

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Control of Bake-Hardening Level and Aging Properties in a Hot Dip

Galvanizing Line

C. Escher (ThyssenKrupp Steel Europe AG)

R. Gerlach (ThyssenKrupp Steel Europe AG)

K. Machalitza (ThyssenKrupp Steel Europe AG)

M. Norden (ThyssenKrupp Steel Europe AG)

ABSTRACT:

Bake-hardenable steels have been widely applied in the automotive industry. They exhibit an additional increase of yield strength during paint-baking, thus, properties such as dent resistance are improved on the structural part. Diffusion of solute carbon to dislocations causes dislocation pinning and therefore an increase of yield strength. Both bake-hardening potential and aging are driven by this mechanism. The bake-hardenability increases dent resistance after press-forming and paint-baking. On the contrary, aging decreases formability before press-forming and increases the risk of stretcher strain marks. Therefore, the challenge in producing bake-hardenable steels is the balancing of bake-hardening potential and aging. To prevent difficulties in cold forming, controlling of aging and thus, controlling the solute carbon level in the material is necessary. The carbon content of the steel can be adjusted by regulating the dew point of the annealing atmosphere in a hot dip galvanizing line. Since the water bearing atmosphere provides a high reaction activity towards carbon at annealing temperatures, decarburization of steel takes place during the recrystallization annealing process. A reduction of the carbon content of 3 to 8 ppm can be observed. Considering the carbon level of the hot rolled strip and controlling the decarburization in the hot dip galvanizing line, the balance between aging effects and an adequate bake-hardening level can be obtained.

INTRODUCTION:

The necessity of reducing carbon dioxide emission is the driving force behind the wide use of Advanced High Strength Steels (AHSS) in the body in white (BIW) and bake-hardenable steels (BH-steels) in outer part panels. To meet future demands regarding crash, weight and mechanical properties of future cars, the

steel industry will continue to optimize present steel grades as well as developing novel AHSS [1, 2].

Novel steel grades ask for highly sophisticated production processes and modern lines. To cope with these high demands, the steel industry invests in new and modernizes existing production facilities. Especially in the field of exposed production, a lot of efforts are made to meet customers increasing demands. The interaction of AHSS with the annealing gases of a continuous hot dip galvanizing line (CGL) is well known to be the key parameter to ensure superior surface quality for AHSS. The influence of the dew point (DP) during intercritical annealing on the surface chemistry of steel strips and the impact of selective oxidation on zinc wetting is widely discussed in many research works, especially regarding Multi Phase (MP) steels [3-5].

BH-steels exhibit an additional increase of yield strength during paint-baking due to the pinning of dislocations by solute carbon. As a result, properties like dent resistance are significantly improved on the structural part. Yet, carbon diffusion to dislocations also takes place at ambient temperatures and is responsible for the so called aging. The aging phenomenon may cause surface defects known as stretcher strain marks and may also infect the formability of the material.

Therefore, the challenge in producing BH-steels is managing the balance of bake-hardening potential and aging [6].

To prevent difficulties in cold forming, controlling aging and thus controlling the solute carbon level in the material is necessary. The major step in adjusting the solute carbon is done in the liquid state in the steel shop by degasing and alloying. Yet, as known from the AHSS, water vapour bearing annealing atmosphere can encourage decarburization significantly. Thus, the aim of the development is to fine tune the carbon levels of BH-steel-grades by controlling the dew point (DP) in continuous galvanizing furnaces.

FIRST RESULTS:

A first feasibility study was conducted by purposely increasing the dew point in the annealing furnace of a continuous hot dip galvanizing line while producing a BH-steel-grade. It was assumed that a significant reduction of solute carbon in the bulk material of the steel could be achieved by the following reaction mechanism:

C + H2O ↔ CO + H2 Equation 1

Several full hard samples and corresponding coated samples of the produced steel strips were taken under two different production conditions, representing different dew points. In all samples, the carbon

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content was measured by spark ablation optical emission spectroscopy (SA-OES) and the differences after and before HDGL (∆C*) of the corresponding samples were calculated. A first contingent of samples was taken under low DP conditions of about -40 °C. This contingent was compared to sample produced under higher DP conditions of about -28 °C.

As shown in Figure 2, a good correlation was found. Thus, the possibility to fine-tune the bake-hardening and aging properties in the annealing furnace of a continuous hot dip galvanizing line by adding water vapour is proven.

Dew Point [°C]-24-26-28-30-32-34-36-38-40-42

Diff

eren

ce o

f Car

bon

Con

eten

t * [w

t.-%

] 0,0002

0,0000

-0,0002

-0,0004

-0,0006

-0,0008

SUMMARY AND OUTLOOK:

Figure 1: Difference ∆C of the carbon-content vs. dew point [∆C* = carbon content after HDGL – carbon content before CGL]

It is shown, that as proposed, the carbon content of the steel can be adjusted by regulating the DP of the annealing atmosphere in a continuous hot dip galvanizing line. As the water vapour bearing atmosphere provides a high reaction activity towards carbon at peak annealing temperatures, decarburization of steel takes place during the recrystallization annealing process. A reduction of the carbon content of about 3 to 8 ppm was observed. Considering the carbon level of the hot rolled strip and controlling the decarburization in the hot dip galvanizing line, the balance between aging effects and an adequate bake-hardening level can be obtained. In the future a close loop process for controlling the furnace DP should be developed, taking into account the chemical composition of the full hard material entering the hot dip galvanizing line. Dew point control in a wide range, starting from e.g. -45 °C (~71 ppm H2O) to 0 °C (~ 6 % H2O) is very challenging, thus new ways of controlling the furnace´s dew point in hot dip galvanizing lines need to be developed.

In Figure 1 ∆C* is plotted against the corresponding DP in the annealing furnace. As proposed, the carbon content of the steel was altered by regulating the DP of the annealing atmosphere. For water vapour has a high affinity towards carbon at peak annealing temperatures, decarburization of steel takes place during the recrystallization annealing process. A reduction of the carbon content of about 3 to 8 ppm can be observed.

REFERENCES: As the relative change of n-value* is directly linked to the solute carbon content of ultra-low carbon steel, an indirect proven effectiveness of this annealing process can be shown by plotting the n-value* over the solute carbon content of the full recrystallized annealed samples.

1. Gomez, M.; Isaac, G.-C.; Haezebrouck, D.-M.; DeArdo, A.-J.; ISIJ International Vol. 49 (2009) 2, p. 302–311

2. Heller, T.; Deinzer, G.-H.; Steinbeck, G; International Conference on Steels in Cars and Trucks (SCT 2008), Wiesbaden (2008), p. 503–509

Solute Carbon Content (Carbon measured after HDGL) [wt.-%] **0,00200,00160,00120,0008

Rel

ativ

e ch

ange

of n

-val

ue*

-0,02

-0,04

-0,06

-0,08

-0,10

-0,12

-0,14

-0,16

-0,18

3. Bellhouse, E.-M.; McDermid, J.-R; Metallurgical and Materials Transactions A Vol. 41A (2010) 6, p. 1539–1553

4. Norden, M.; RWTH-Aachen, PhD Thesis, Aachen 2010

5. Norden, M.; Blumenau, M.; Schönenberg, R.; Peters, K.-J; Galvatech 11, Genua (2011)

6. Escher, C.; Brandenburg, V.; Heckelmann, I.; International symposium on niobium microalloyed sheet steel for automotive applications, Araxa (2005), p. 383-395 Figure 2: Relative change of n-value vs. solute carbon content

after annealing [n-value *= (n-valueaged – n-valuenon-aged) / n-valuenon-aged]; [Solute Carbon Content** = Carbon content measured after HDGL – Niobium Content/7,74]

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Innovative flameless regenerative burners for Direct Flame Furnaces of Hot Dip Galvanizing lines - up to 15% lines productivity increase

C. Villermaux (GDFSUEZ, DRI/CRIGEN, Paris) K. Beaujard (ArcelorMittal Maizières Research)

N. Richard (GDFSUEZ, DRI/CRIGEN, Paris) A. Danda (ArcelorMittal Maizières Research) H. Saint-Raymond (ArcelorMittal Maizières

Research) T. Bellin-Croyat (GDFSUEZ, DRI/CRIGEN, Paris)

ArcelorMittal and GDFSUEZ focused their working forces on developing an innovative technology by launching a common project dedicated to Hot Dip Galvanizing lines, especially to preheating sections equipped with direct flame burners.

This paper describes the technological innovation performed and validated in semi-industrial conditions as well as the measured performances and expected gains for industrial lines.

On hot dip galvanizing lines, the preheating section of the furnace can be equipped by direct flame burners managed by under-stoechiometric gas combustion conditions. The lack of oxygen into the furnace atmosphere is used to control the oxides nature and oxides thickness on the steel surface depending on the strip chemical components and process conditions. Therefore mastering the strip surface at the end of the thermal treatment is the key to ensure a perfect wettability of the steel strip during the hot dip galvanizing process.

PRINCIPLE

GDF-Suez and ArcelorMittal identified the potential interest to apply flameless regenerative burners to the specific conditions of preheating section on galvanizing lines. The innovative burning technology dedicated to non-oxidizing heating atmospheres consists on a combination of an integrated post-combustion system, a regenerative system and a flameless combustion technology.

The association of those three principles should allow meeting the following requirements: - to guarantee a complete combustion at the furnace exit - to lead to high energy efficiency - to achieve a cleaner process (NOx & CO) - to obtain an homogeneous heating temperature

The working principle of these industrial burner prototypes is presented on Figure 1. During the exhausting mode, the fumes of the furnace (~1300°C), that still contains combustible (air deficiency combustion) are sucked through the burner chamber. Then the combustion of the not burnt

elements occurs thanks a second air injection to obtain a complete combustion (post-combustion in over stoechiometric conditions). Finally the fumes (~1400°C) go through the regenerator to transfer its heat to the ceramic spheres of the regenerative store so that the fumes are quite cold at the exit of the regenerator (< 300°C). When the cycle switches from exhausting phase to combustion mode, the ambient air (~25°C) is injected through the regenerator store to be preheated (~1000°C) before entering into the burner’s chamber. The preheated air is then sent into the furnace chamber at high velocity and separately from combustion natural gas so that the combustion occurs into the furnace with the flameless principle.

Figure 1: Working principle of innovative technology

The adaptation of the flameless regenerative burners to under-stoechiometric conditions of the preheating section of galvanizing lines is a European innovation by itself and raises issues like:

- How to design the regenerative burners’ technology to reach a healthy behavior in flameless combustion? What optimization of the working parameters to achieve maximal performances?

- What feasibility to implement flameless regenerative burners into heating section under sub-stoechiometric conditions? What impact on the steel surfaces?

RESULTS: BENEFITS / SAVINGS OF GAS

The pair of burner prototypes that have been tested are based on a commercial regenerative flameless burner design (300kW gas power). The regenerative storage and the post-combustion chamber between the nozzle and the regenerative tank have been adapted to investigate several technical options (size, injection...) in the perspective of this particular application.

The project was set-up following three work axes:

1- Experimental characterization of the combustion efficiency and the gas atmosphere generated by these prototypes within an semi-industrial scale furnace, optimization of operating conditions;

2- Based on previous results, impact of the generated gas atmosphere to the steel surface.

3- Evaluation of the energy savings, the environmental impact and costs savings for specific ArcelorMittal hot dip galvanizing lines with dedicated numerical tools.

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Complementary experimental means, complex measurements and numerical tools have been displayed, based on GDF Suez and ArcelorMittal expertises.

Resulting from characterization campaigns, the performances of the tested burners are already encouraging and already suitable for industrial use:

- No operating problem has been detected. The burners and its associated post combustion systems run under safe conditions, during ignition and operation.

- Performances in terms of NOx and CO emissions need a set of optimised values of the operating parameters, but have already satisfactory levels for an industrial use.

- Combustion efficiency of this innovative technology is very high and promises to reach a more energy efficient furnace compared to actual technology.

- Temperature field within the furnace, and particularly near the strip, seems to be quite homogeneous, leading to a better heating quality.

- There is no impact of the generated atmosphere on the quality of the surface of the strip

Two different real cases of ArcelorMittal industrial issues have been investigated for a demonstration operation on an industrial site. The estimation of the gains on these industrial lines have been obtained thanks to the numerical tool that have been validated as representative of existing lines and as able to model the innovative regenerative burners implemented on the line

Energy savings stakes for line A: a full conversion from standard burners to the innovative burners has been analysed.

Provided the innovative burners are located at an optimised place on the line, not simply replaced at the location of the existing burners (see figure 2), we can then have significant energy savings (up to 14% of thick strip) while respecting the constraints of the furnace such as the maximum temperature of the roof.

A productivity increase issue for line B: a retrofit of one combustion zone has been studied. The preheating furnace of this line is equipped with a classical recovery system and 3 burning zones. The first burning zone could not be used because of extraction flow rate and temperature limitations of the recovery system. This power limitation implies a bottleneck in term of production. No existing technology meets the issue except the full retrofit of the recovery system.

The computations performed to dimension the heating power repartition and the burners location show that the implementation of regenerative burners into the first burning zone, can lead to a maximum productivity increase of 15 % for the considered

product order book while additional energy savings can reach 5% (specific gas consumption)

The strip thermal profile and target temperature at the exit of the preheating furnace are respected as well the acceptable roof temperature and fumes temperature at the exhauster. In that second industrial case, this technology is the optimal candidate to solve the furnace bottleneck in order to increase productivity at lower investment’s costs.

200

00

600

800

1000

1200

1 00

1600

0 2 6 8 10 12 1 16 18 20

TE

MP

ER

AT

UR

E (

°C)

FURNACE LENGTH (m)

ROOFTEMPERATURE

STANDARD BURNERS / REFERENCE CASE

INNOVATIVE BURNERS / CASE 1

INNOVATIVE BURNERS / CASE 2

Maximal authorized roof temperature

0

100

200

300

00

500

600

700

0 2 6 8 10 12 1 16 18 20

TE

MP

ER

AT

UR

E (

°C)

FURNACE LENGTH (m)

HEATING CURVES

STANDARD BURNERS / REFERENCE CASE

INNOVATIVE BURNERS / CASE 1

INNOVATIVE BURNERS / CASE 2

Figure 2: Simulation of preheating furnace of the line A –different options of the innovative technology implement

CONCLUSION

The Research and Development program led to validate the feasibility to implement flameless regenerative burners into heating section under sub-stoechiometric conditions and to evaluate the expected energy savings, pollutant emissions and productivity gains in the case of a line retrofit:

- A saving up to 15% on gas consumption and associated CO2 emission,

- A decrease of 10% on CO emission

- A low level of NOx emission: 200 mg/Nm3 @ 3%

O2

- No impact on product quality

These encouraging results allow us to predict a productivity increase up to 15% on some bottlenecks Hot Dip Galvanizing lines, demonstrating the particular interest of the technology for continuous annealing lines.

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Continuous performance evaluation of control systems for reducing energy consumption in

annealing lines

Dr. Andreas Wolff, VDEh-Betriebsforschungsinstitut GmbH

Prof. Dr. Jelali, Mohieddine, Cologne University of Applied Sciences

INTRODUCTION

The steel processing industry is faced with ever-increasing demands on product quality, productivity, and environmental regulations. These force companies to operate their plants at higher and higher peak performance. To avoid degradation of product quality and excess of material and energy consumption, prompt recognition and correction of process-control malfunctions and identification of improvements is essential. In today’s practice, inadequate controller tuning, lack of maintenance, and man-power limitation are major causes of poorly tuned control loops in steel processing.

MONITORING PARADIGMS FOR ASSEMENT OF COMPLEX CONTROL SYSTEMS

To avoid degradation of product quality and excess of material and energy consumption in industrial environments, prompt recognition and correction of process-control malfunctions and identification of improvements is essential. This task can effectively be performed by control performance monitoring (CPM), i.e. the process of continuously measuring the performance of control loops and comparing it against benchmarks with optimal performance [3, 4].

Hierarchical procedure for control performance monitoring

Since the considered plants have many control loops located in different levels of hierarchy, it is important to first decide whether a bottom-up or top-down strategy should be followed. It is not necessary to further diagnose a process and controller when its performance is entirely satisfactory with respect to safety, process-equipment service factor, and plant profit. Only those control loops, which are not adequately performing and offer potential benefit, are considered in the subsequent diagnostic steps. Therefore, the top-down strategy seems to the most effective one.

Harris index – a standard method for CPM

CPM techniques find out whether the controller is working satisfactorily. If not, the next step is initiated to figure out the improvement potential without disturbing the running system, i.e. using normal operating data.

The standard CPM method is the minimum-variance-based performance index [2], referred to as the Harris index. The underlying principle is to compare the performance of the controller with a benchmark. In the case of the Harries index, the benchmark is a minimum variance controller (MVC), which minimizes the variance of the control error. The key point is that the MVC benchmark (as a reference performance bound) can be estimated from routine operating data without additional experiments, provided the system delay τ is known (or can be estimated with sufficient accuracy):

2MV

2

( )

y

ση

σ

τ =

where is the variance of the system output (or control error) under minimum variance control and

is the output variance under the investigated controller. The algorithm can be summarised as: Preparation. Select the time-series-model type and orders Step 1. Determine/estimate the system time delay τ. Step 2. Identify the closed-loop model from collected normal operating data.

Step 3. Estimate the minimum-variance using the closed-loop model.

Step 4. Compute the actual output-variance Step 5. Compute the (Harris) performance index η to see how far the actual performance is from the minimum performance.

MVC serves as an appropriate benchmark against which the performance of other controllers may be compared. However, this does not imply that MVC should be the goal towards which the existing control should be driven, or that it is always practical, desirable, or even possible to implement.

PERFORRMACE MONITORING OF A GALVANISING LINE

Within the RFCS project AUTOCHECK [1], methods for control performance monitoring have been developed and adapted to steel processes to the first time. Together with AMEH, BFI applied this method at the galvanising line, see Figure 1. The first process considered was the annealing furnace.

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Control structure of the annealing furnace

Figure 1: Layout of the galvanising line no. 1 at AMEH

Figure 3: Improvement of the performance caused by the tuning recommendations

CONCLUSION

An industrial case study has been presented and shown how to benefit from the application of CPM technology in metal processing. Other applications in this area can be found in [5].

Future attention will be paid to the development of automatic tuning methods based on the results of CPM and the integration of CPM with process and condition monitoring techniques towards continuous and comprehensive maintenance and asset management.

Figure 2: Structure of the analysed control system

Control-performance assessment and retuning of temperature control

The evaluation procedure applied for the assessment of the current performance of the temperature control system consists of five steps:

REFERENCES

[1] AUTOCHECK: Enhancement of Product Quality and Production System Reliability by Continuous Performance Assessment of Automation Systems. Research Project No. RFS-CR-03045, European Community, Research Fund for Coal and Steel, 2003–2007. Draft Final Report submitted in March 2007.

Step 1: Determine the appropriate sampling rate to estimate the closed loop model.

Step 2: Merge single data files together to get one file with a minimum number of samples of about 1200 data points.

Step 3: Determine the time delay. Step 4: Compute the Harris and extended

performance index. [2] T. Harris, Assessment of closed loop performance. The Canadian Journal of Chemical Engineering 67 (1989) 856–861.

Step 5: Retuning of the controller and assessing the controller performance again.

The evaluation results have led to the conclusion that the performance of the temperature control of the annealing furnace is much lower than that of the other stages of the annealing line. Thus, an emphasis was then placed on the further study of the temperature control in the annealing furnace. More details of this assessment study can be found in [1].

[3] B. Huang, S.L. Shah, Performance Assessment of Control Loops, Springer-Verlag, 1999.

[4] M. Jelali, An overview of control performance assessment technology and industrial applications. Control Engineering Practice 14 (2006) 441–466.

[5] M. Jelali, Performance assessment of control systems in rolling mills – Application to strip thickness and flatness control. J. Process Control 17 (2007) 805–816.

The performance results before tuning are shown on the left side of Figure 3 (left hand side). As one can clearly see, the performance of the temperature control of annealing furnace is quite low. A closer examination of temperature traces revealed that the strip temperature reference is not always reached and the maximum furnace temperature of 950°C is often exceeded in the last zones. This was solved by redistribution of the heating power within the annealing furnace. The obtained performance after tuning is seen in Figure 3 (right hand side).

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BACKGROUND Accurate and cost effective temperature measurement in metal strip manufacturing is a topic when highly reflective surfaces are processed. High reflectivity means consequently a low emissivity. Combined with processing at relatively low temperatures this means that the pyrometric sensor receives low levels of radiation. On top of this we need to know the emissivity of the material in order to be able to calculate the correct temperature from this radiation. The emissivity of the surface in the manufacturing process depends on the material structure of the surface (like e.g. roughness, possible oxidation), on the composition of the alloy as well as on the temperature. This means there is no general valid emissivity setting for the pyrometer. In 1999 a 2 day workshop at Hoogovens for the Aluminium industry resulted in the initiative to develop an improved radiation thermometer for aluminium within the European VIRFAB project. This project lead to a proof of principle that was extensively tested at the Tata Steel site in IJmuiden on steel strip and on at the former Corus Aluminium Site in Duffel on aluminium strip. Based on these tests, a total redesign has now resulted in a prototype for full industrialisation of a contactless temperature measurement, dealing with low levels of radiation and varying emissivity values of the object. Also a dedicated calibration device was developed, as this was required by the nature of the system.

MEASUREMENT CONCEPT The measurement principle consists of two

Figure 1. Schematic concept SMOTE

radiators that have different temperatures and are used to illuminate the object in a hemi-spherical illumination approach. Four temperatures are measured simultaneously, two thermocouples and two

meters. The tempe are Law

he radiation energy from the object (strip) is calcu

[ U2)] U = ----------------------------------------------------

eater, controlled by Th.. The cold radiator is cooled at a constant

ooler.

radiation pyrointo radiation energie

ratures s using Planck

converted . ’s

T

lated according to:

ε1 * U22*( U11 - U1) – ε2* U11 *( U22 - o

[ ε1 *( U11 - U1) – ε2* ( U22 - U2)] From the energy Uo using Planck’s Law again the surface temperature of the object is determined. In a similar way, the emissivity of the object (strip) is calculated. The hot radiator is kept at a constant temperature by using an electrical h

temperature by an external c

LABORATORY TEST RESULTS During labtests it was shown that temperature measurements can be performed with an accuracy level of +2 degrees in the low temperature range around 50oC; + 4 oC from o o150 C to 250 C, at the very low emissivity level of 0.02 (ε valid for the wavelength

ions as demanded by the measurement l conditions due to the industrial

range of: 8 < λ < 14 μm)

INDUSTRIAL OPERATING CONDITIONS Operating conditions are defined on two levels: intrinsic conditprinciple and externaenvironment. Intrinsic conditions: Radiators: the surfaces of the radiators should be homogeneous and at constant temperature. The homogeneity is ensured by proper design; the temperature control is by (electrical) heating and (water) cooling. The temperature of the cold radiator should be below the lowest strip temperature to be measured (but above the dew-point of the ambient atmosphere to avoid condensation), the temperature of the hot radiator preferably above the highest object temperature. As radiator surface degradation can be expected at temperatures above 250ºC this forms the upper temperature limit for the hot radiator. All electronics inside the SMOTE sensor have an upper operating limit of ~40ºC, necessitating a cooling jacket. The distance of the sensor to the object, ~40 mm, has to be tightly maintained to prevent on the one hand contact between strip and sensor and on

Hot radiator ThThp detector 2

thermocouple

2 energy radiator

ε2 emissivity UU22 energy detector

Cold Radiator Tc thermocouple

U1 energy radiator

bject (strip)

Tcp detector 1 ε1 emissivity

U11 energy detector

O 0 temperature

ε0 emissivity Uo energy

T

Simultaneous Measurement of StripSurface Emissivity and Temperature

Gédo Kuiper, Frans Muilwijk, Renée van Buren,

Joop Wesselink

Page 131: 2-page abstracts booklet

of hemispherical ger fulfilled.

the other hand errors due to a to large distance. At large distances the condition illumination is not lonExternal conditions: The external conditions can be divided into three categories: temperature, air flow and air composition. The outside temperature can be dealt with by using a cooling jacket, air flow between the radiators and the object will induce temperature differences over the radiators and need to be limited; air composition, water/oil content, may lead to condensation on the radiators and thereby changes in the spectral response of these radiators, leading to measurement rrors.

line to measure and control the strip mperature.

e

INDUSTRIAL IMPLEMENTATION The SMOTE system has been tested inline in Tata Steel Trostre Works, Llanelli, United Kingdom. It was mounted vertically above the coating section of a Protact coatingte

Figure 2. SMOTE sensor in operation at Trostre

orks

mperature measurement was found to be within 3 oC.

is tegrated in the SMOTE equipment configuration

Figure 3. SMART calibration system (left) and SMOTE ystem (right in parking location)

TS AT TROSTRE WORKS AND CONCLUDING EMARKS.

s

TEST RESULR

Figure 4. Results of SMOTE during test-runs in

rostre Works

system ill be made commercially available.

T The SMOTE system performed well under test conditions. The system is fast enough for closed loop control. From the experience in Trostre, additional work is specified to meet all industrial and environmental conditions to make the system industrially robust. When this is achieved, the

W The substrate strip is chromium plated tinplate, with emissivities as low as 0.05. The target temperatures are below 250 oC. The accuracy of the te

w

CALIBRATION To calibrate the system, it is necessary to aim it at a representative target. This target is a sample of the material under production and temperature controlled to the desired setpoint. It is essential that the sample is homogeneous in temperature and that the surface is absolutely virginal to avoid emissivity related errors. For this calibration the SMART (SMOTE auxiliary Reference Temperature) system was build, thisin

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Session 9: Energy

9.1 Temperature is money: How to make the plants of today comply with the

requirements of tomorrow C. FRÖHLING*, B. BÜTTENBENDER, P. HEMMLING (SMS Siemag AG), Germany

p. 144

9.2 Utilization of siderurgical gases in gas engines for power generation E. AMPLATZ*, M. SCHNEIDER, S. WOJCIK (GE Power & Water), Austria

p. 146

9.3

Reduction of Natural gas consumption after application of Nalco Fire-8252 Prep in Boosters enables Companhia Siderurgica Nacional (CSN) to reduce CO2 emissions S.A. BARROS (CSN), P. SANTIAGO*, S. RIBEIRO, F. SUBTIL (Nalco), Brazil

p. 148

9.4

Process improvements and energy efficiency projects on auxiliary equipment in Tata Steel Aldwarke Cast Products A. PATSOS*, P.A. BROOKS, A. PRESTON, A. BURGAR (Tata Steel), United Kingdom

p. 150

9.5

From the energy audit to the final performance tests: success story of a furnace revamping L. FERRAND* (CMI Greenline Europe), J.L. LAMBERT (Vallourec & Mannesmann), C. BOURGE (CMI Greenline Europe), E. CARRÉ, M. VARLEZ (Vallourec & Mannesmann), C. CONSTANT (CMI Greenline Europe), France

p. 152

9.6

Towards low energy consumption and low CO2 production: Steelmaking plants, a roadmap R. NICOLLE* (Consultant), France

p. 154

* speaker

Page 133: 2-page abstracts booklet

Session 9: Energy

Table of Contents

9.1 Temperature is money: How to make the plants of today comply with the requirements of tomorrow C. FRÖHLING, B. BÜTTENBENDER, P. HEMMLING (SMS Siemag AG), Germany

9.2 Utilization of siderurgical gases in gas engines for power generation E. AMPLATZ, M. SCHNEIDER, S. WOJCIK (GE Power & Water), Austria

9.3

Reduction of Natural gas consumption after application of Nalco Fire-8252 Prep in Boosters enables Companhia Siderurgica Nacional (CSN) to reduce CO2 emissions S.A. BARROS (CSN), P. SANTIAGO, S. RIBEIRO, F. SUBTIL (Nalco), Brazil

9.4

Process improvements and energy efficiency projects on auxiliary equipment in Tata Steel Aldwarke Cast Products A. PATSOS, P.A. BROOKS, A. PRESTON, A. BURGAR (Tata Steel), United Kingdom

9.5

From the energy audit to the final performance tests: success story of a furnace revamping L. FERRAND (CMI Greenline Europe), J.L. LAMBERT (Vallourec & Mannesmann), C. BOURGE (CMI Greenline Europe), E. CARRÉ, M. VARLEZ (Vallourec & Mannesmann), C. CONSTANT (CMI Greenline Europe), France

9.6

Towards low energy consumption and low CO2 production: Steelmaking plants, a roadmap R. NICOLLE (Consultant), France

Page 134: 2-page abstracts booklet

Temperature is money: How to make the plants of today comply

with the requirements of tomorrow

Dr. C. Fröhling (SMS Siemag, Düsseldorf)

B. Büttenbender (SMS Siemag, Düsseldorf)

Dr. P. Hemmling (SMS Siemag, Düsseldorf)

1. ENERGY RECOVERY FROM WASTE HEAT

The most important energy source in the steel industry is heat. Along the process chain from steelmaking plants to processing lines we can find several process steps where heat is required and not only waste heat, but also combustible gases are generated.

Up to 40 per cent of the energy spent in electric steelmaking leaves with the hot off-gas as sensible heat. Due to technical reasons, it is absolutely essential to cool down the primary off-gas from approximately 1250°C to values below 250°C. By using our technologies up to 85 per cent of this wasted energy can be recovered. Similar proportions also apply to the processes in the SAF, CONARC and BOF or AOD converter. Compared to a BOF converter, the thermal off-gas energy of an EAF is more than two times higher related to the liquid steel quantity.

Conventional off-gas ducts are cooled by water that circulates through membrane walls. The cooling water itself flows through a heat exchanger and the thermal energy remains unused.

In order to make use of this energy, SMS Siemag developed an energy recovery system that produces steam by means of an evaporation-cooled off-gas duct. The steam can be used for different technical purposes. Common applications are power generation in steam turbines, driving vacuum pumps or feeding the steam into an existing network.

For BOF melt shops, evaporation-cooled off-gas ducts are well-known. For other metallurgical melting units, however, this is an innovative technology. Our customers have become aware of this opportunity to maximize energy utilization.

This is why ETI KROM, a ferrochrome producer from Turkey, ordered such an energy recovery plant that will be connected to two SAFs and supplies the steam to a 5-megawatt turbine. ETI KROM expects an amortization period of less than four years.

Fuxin Special Steel has placed an order with us for the engineering and supply of a steam generation plant that uses the off-gas heat at AOD converter and EAF – the world first installation of this kind.

One of the most interesting points is the steelmaking process in a basic oxygen furnace or electric arc furnace. Therefore, several ecoplants-solutions have been developed by SMS Siemag.

With these concepts, huge parts of the wasted heat energy are transformed into steam by evaporation-cooled off-gas ducts. At the BOF converter this technology is state-of-the-art.

In a low-pressure circuit the feed water is heated up to approximately 130°C by cooling the movable off-gas elbow of the gas duct. This heat is used for deaerating the feed water. The pressurized water coming from the feed-water tank is pumped into the economizer, which is connected to the steam drum. The boiling water is circulated by pumps on natural circulation through the cooling surfaces of the off-gas system and partly evaporated.

This water-steam mixture is routed back to the steam drum and separated there. The discontinuous amount of steam generated in the EAF batch process is temporarily buffered in accumulators and delivered to the consuming units. In comparison with a 150-ton BOF with 12 to 14 tons of generated steam per heat, a typical EAF with the same tapping weight will generate an average steam flow of 42 tons per heat at a gauge pressure of 25 bar (charging material: 100% scrap). Steam generated in this way is always saturated steam. Due to rising energy costs, this proven technology depending on steam utilization, generates a low amortization time.

In comparison with a 150-ton BOF with 12 to 14 tons of generated steam per heat, a typical EAF with the same tapping weight will generate an average steam flow of 42 tons per heat at a gauge pressure of 25 bar (charging material: 100% scrap). Due to rising energy costs, this proven technology depending on steam utilization, generates a short amortization time.

Page 135: 2-page abstracts booklet

2. USAGE OF EXHAUST GAS 3. ECOPLANTS SOLUTIONS The large range of gaseous byproducts as blast

furnace gas, coke oven gas, SAF gas and converter gas, have high energy content in terms of combustible components. Utilizing these gases as primary fuel in an industrial power plant contributes significantly to increased energy efficiency in steelworks and therefore reduces the overall steel manufacturing costs and saves CO2 emissions (up to 55 kg per 1 ton steel).

For the systematic utilization of these gases, e.g. to generate steam for production and/or to generate electricity in a complete power station process, SMS Siemag offers a wide range of part-standardized steam generators. In this context SMS Siemag focuses on taking into account the many demands that influence the choice of steam generator type. Examples for these requirements are:

The new ecoplants label is our new identification symbol for sustainable solutions by SMS Siemag. The connection of sustainability and economic growth is the result of our four ecoplants- criteria:

Low Emissions Variable and fixed-pressure mode

Wide range of fuels Daily start/stop

Compact design High availability

Fast starting capability

High cost-effectiveness

Flexibility

Significant reduction in the use of raw materials

Significant reduction in the use of energy and operating media

Significant reduction in emissions

Significant improvement in the recycling quota

SMS Siemag’s range comprises suspended or self-supporting natural-circulation steam generators with high to top outputs. We supply single or multi-pass types that can be adjusted to a wide variety of tasks.

Existing plants have a high potential for the optimization of air- and fuel supply. Low calorific gas burners often operate with conservative combustion parameters that are highly prone to failures, which lead to fatal downtimes. Our experts have the required Know-how and a long lasting experience to optimize these burners and therefore ensure smooth operations.

Page 136: 2-page abstracts booklet

Utilization of siderurgical gases in gas engines for power generation

E. Amplatz*, M. Schneider, St. Wojcik

(GE Power & Water, Austria)

UTILIZATION OF SIDERURGICAL GASES IN GAS ENGINES FOR POWER GENERATION:

GE’s Jenbacher gas engines division:

GE’s Jenbacher gas engines division is a manufacturer of gas engines located in Jenbach/Austria since 1950. The product portfolio extends from 250kWel until 9.500kWel/engine. Our experience based on an installed fleet of about 13.000 engines with a total capacity of 16GWel worldwide. The engines are capable to use a wide range of different gases (LHV 0,5kWh/Nm³-30kWh/Nm³) to produce electrical energy, heat, cold and steam.

Challenge of industry:

Rising energy costs and a high demand for power with a steadily growing of flexibility are major challenges for the industry in general and especially for steel- and ferro alloy industry. Off gases created as a “free” by-product during steel- and ferro alloy production processes serve as an attractive option for efficient power generation. In addition to the economic benefit, using these gases as engine fuel reduces industrial CO2 emissions and saves natural energy sources. GE offers specially modified Jenbacher gas engines that make efficient use of three different steel- and ferro alloy off gases -Coke Oven Gas, Blast Furnace Gas, and Converter Gas- for combined generation of electricity and heat, while managing their varying compositions. The technology allows the user to expect an electrical efficiency up to 40% (simple cycle) and a total of up to 80%.

Characteristic of the off gases:

Three+one (COG, BFG, LDG, FOF) different off gases can be used in GE’s gas engines. The ferro alloy gases or furnace off gases (FOF) are similar to the converter gas group also known as LDG and show similar characteristics as the converter gas. The wide range of off gases has a different characteristic which has consequently different requirements and challenges for the combustion.

Steel- and ferro alloy gas characteristic

COG BFG LDG FOF

…O

ccur

s as

a b

y pr

oduc

t…

In th

e in

dust

rial

prod

uctio

n of

co

ke fr

om h

ard

coal

In th

e pr

oduc

tion

of

pig

iron

from

iro

n or

e

Dur

ing

the

prod

uctio

n of

st

eel f

rom

pig

iron

Dur

ing

prod

uctio

nof f

erro

ch

rom

e, fe

rro

man

agne

se,

ferro

silic

on,

titan

ium

slo

g,

calc

ium

car

bid

H2

CO

CH4

50-70%

~5%

25-30%

~3%

20%

-

1-50%

50-80%

-

5-35%

50-80%

-

[kW

h/N

m³]

~5 ~0.7-0.8 ~2.5 - 3 ~2 - 3

The main driver for utilization in an internal combustion engine is the laminar flame speed. Coke oven gas - which is easy to ignite and the combustion in a gas engine is relatively simple - the main challenge is to control the high reactivity due to the high hydrogen content (50-70%). LDG and FOF is dominated by CO (50-80%) on the other hand demands a specialised combustion process, which means to bring the combustion on speed, and therefore specific development of the gas engine. Last but not least the BFG application will top the challenges of LDG in handling of gas amount (3000Nm³/h/MWel) and of very low calorific value (LHV ~ 0.7-0.8 kWh/Nm³) of the gas. All in all GE’s R&D team for Jenbacher gas engines has found an answer on all requirements which occurred by the different off gases to secure reliable operation for the steel- and ferro alloy industry. Customers can build on almost 20 years of experience in burning off gases.

Existing solutions with gas engines for off gases

Since we commissioned our first multiple off gas engines power plant in Spain in 1995, GE has delivered 53 engines with 76MWel around the globe running with different off gases. The engines have more than 2 Mio operation hours on the clock.

Experience with COG

The company ”Profusa SA” in Bilbao has a gas with high hydrogen content available as a by-product of coke production. Since August 1995 coke gas is

Page 137: 2-page abstracts booklet

burned in 12 Jenbacher gas engine generating sets J316 and converted into a maximum of 7.1 MW electrical outputs. The special engine design as well as the appropriate gas mixing equipment makes it possible to operate the engines either on 100% coke gas, 100% natural gas or on a coke gas/natural gas mixture. The exhaust gas is partly used for waste water treatment and partly for steam production.

Experience with LDG

The majority of our off gas engines running with LDG gases are either located in Spain or in South Africa. In October 2003 the first test engine was installed at Aceralia Steel Mill Factory in Avilés, Spain. After a pilot test period of 3,000 hrs the whole operation were installed and commissioned in September 2004.

Typical LDG gas composition:

Since then 12 engines of type J620 deliver total 20MWel and 12MWth output warm water and 18t/h saturated steam at 21.5barg. Three of the twelve modules can burn either LD converter gas or natural gas. The natural gas ensures operation in case of a reduction in the fuel supply from the steel plant. The tube type heat-recovery boiler is designed for the maximum flow of a total of 16 engines working together for what the whole plant is already prepared. The boiler is equipped with an economizer, evaporator and superheater. It is arranged with a main chimney and a by-pass stack for startup and shut down of the generating sets. The boiler is prepared for co-firing, capable of increasing the steam production up to 35 t/h or 20t/h when the generating sets are at standstill. Since 2004 more than 520.000 ophs are on the clock of the twelve engines.

Experience with BFG

Blast furnace gas (BFG) is another challenge for modern gas engines. BFG exhibits an extremely low calorific value (LHV ~ 0.7 kWh/Nm³) and a challenging

ratio between the burnable components like CO and H2 and the inert components CO2 and N2.

Typical BFG composition:

  H2  N2  CO  CO2 

Vol%  3‐5  45‐50 20‐25 

20‐25 

As no blast furnace gas engine solution was commercially available, a cooperation agreement has been established between a leading steel industry company and GE’s Jenbacher gas engine division to develop a gas engine solution for blast furnace gas.

In 2008 the first BFG engine (~2MWel/engine) was built and successfully commissioned. The results met the expectations of both, the customer and GE’s Jenbacher gas engines division. As long as the BFG composition is within a certain limit no permanent enrichment by either COG or natural gas (rich fuels) is necessary.

Summary:

  H2  CH4  CO  N2  CO2 LHV 

[kWh/Nm³] 

Vol%  ~1   ~24   60‐75   ~13   ~13   2 ‐ 2.4  

Gas engines show a high flexibility regarding the utilization of metallurgical off gases and a high. In the meantime GE’s Jenbacher gas engines have more than 2 Mio operating hours with existing applications like COG, BFG, and LDG. The modular approach with multiple units per power plant offers high flexibility regarding plant operation and future growth as well as a safe and reliable operation based on the redundancy solution. The power plant can be operated in a wide range in an optimized efficiency band. This flexibility allows the economical utilization even of relatively small volumes of metallurgical gases which avoids flaring and can substitute other fossil fuels. The high efficiency safe resources and of course it has an indirect CO2 reduction impact too.

Page 138: 2-page abstracts booklet

Reduction of Natural Gas Consumption with Nalco Fireprep-8252 in Boosters enables CSN to

Reduce CO2 Emission

Paulo Santiago (Ecolab/Nalco, Brazil)

Sueli A. Barros (Cia Siderurgica Nacional)

Sebastiao Ribeiro (Ecolab/Nalco, Brazil)

Felipe Subtil (Ecolab/Nalco, Brazil)

BACKGROUND

Cia Siderurgica Nacional (CSN) is a Brazilian integrated steel mill with a production capacity of 5.6 MTonnes/year of crude steel, of which 95% are rolled products. In the hot strip mill (HSM) the steel slabs are reheated to above 1832◦F to be rolled through the rolling mill rolls. The fuels used in the reheating furnaces are natural gas and coke oven gas (COG), the latter being a by-product of pyrolysis process of coal during the coking (coke plant)

The COG flows from coke plant to three IHI boosters (centrifugal compressors) that increase the gas work pressure to be used by many users in the steel mill:

• COG flow: 28.5 dm3/h per unit @ 8,500 rpm

• Suction pressure: 480 mm water (0,68 psi)

• Discharge pressure: 4800 mm water (6.8 psi)

One major user is the HSM. The use of COG as fuel is very attractive because it is a by-product of the coke production process. On the other hand, due to its chemical components (see Table 1), the COG has a high tendency to form deposits (that may increase head loss) and promote corrosion in pipelines; both problems are related to the presence of sulphur, ammonia and cyanide compounds. Overtime these problems can reduce the boosters efficiency and that is a reason why COG use is limited in some mills.

In the reheat furnace at the HSM, natural gas replaces COG whenever the boosters shutdown. This happens mainly due to the rotor unbalancing because of deposition of COG contaminants. When the boosters shutdown, COG is sent to a gasometer to be stored or burned in the bleeder. As the cooking process is continuous and there is demand for all COG produced, the amount of carbon dioxide (CO2) generated from COG burned in the bleeder can be saved by reducing boosters shutdowns.

Table-1:

Chemical Component Composition (%/volume)

Hydrogen 48 – 55

Methane 28 – 30

Carbon Monoxide 5.0 – 7 5

Unsaturated hydrocarbons 2.5-4.0

Nitrogen 1.0-3.0

Carbon dioxide 1.5-2.5

Oxygen 0.0-0.5

Ammonia, hydrogen sulphide gas, hydrocyanic acid, aromatic compounds, tar

*

(*) Components which amount varies according the cooking process

PROBLEM

In the last years the boosters campaigns began to show a decreasing trend, due to deposits build-up in the impellers generating vibration and machines shut-down (Figure 1). Figure-1: Deposits in the boosters rotors

As a consequence of that, the average booster´s campaign was around 2,149 hours (figure 2) and CSN was studying how to increase this campaign to 4,320 hours (six months), so that the shutdown would happen simultaneously with HSM preventive turnaround, avoiding natural gas purchasing. Figure-2: IHI Boosters campaign

0

1000

2000

3000

4000

1st Qtr 2nd Qtr

Boosters Campaign in 2009 (hours)

IHI #1 IHI #2 IHI #3 AVERAGE

The outcome of this technical study was to build a new desulphurization unit (capacity of 60 dam3/h, 5 times bigger than the existing unit) to increase COQ quality and thereby reduce problems related with

Page 139: 2-page abstracts booklet

deposition and corrosion, but this project would require an investment around USD 70 - 90 million.

Figure-5: Booster´s shutdowns and campaigns

0

2

4

6

8

10

Before After

# Boosters` Shutdowns

SOLUTION

The alternative to minimize solids deposition is to disperse them with a proper dispersant. CSN started a bid requesting to the market a product to act as dispersant and corrosion inhibitor, capable also to remove existing deposits, where previous application references in the market would be considered. Nalco proposed to use the Fire-prep 8252, a patented technology developed for use in COG lines, compressors and other combustion equipment. Besides acting as a dispersant, deposit remover and corrosion inhibitor, it also retards the polymerization of the COG components. Fire-prep 8252 was selected by CSN and started to be fed through a pneumatic injection with natural gas or nitrogen via a proper injector provided by Nalco (Figure 3).

0

1000

2000

3000

4000

5000

Before After

Boosters´Campaign (hours)

Figure-3: Nalquil Injector

Due to the reduced shutdowns and the consequent increase in campaigns, the HSM could increase average COG consumption in 0.6 dam3/h, which represents a reduction in natural gas consumption of 0.3 dam3/h (considering the natural gas calorific value is approximately twice the COG value), allowing savings of above 1 million US$ per year:

There was one feed point per booster, in the suction header (closer to the rotor); coupon-test racks were also installed at the booster discharge to monitor corrosion rates. Chemical injection started up in Jun 2010 in boosters IHI #1 and #3; and in IHI #2 in Feb-2012. • Natural gas decreased usage: 304 dm3/h or

2,626 dm3/year • Natural gas cost: US$407.5/dm3 RESULT • Savings: US$1,070,095/year The deployment of this solution allowed CSN to

achieve their goals since boosters vibration and shutdown were reduced due to the strong reduction in impellers deposition (Figure-4), thereby increasing equipment campaign to 4,463 hours on average (7% above the initial target of 4,320 hours) (see Figure-5).

• Chemical treatment cost: US$93,075/year

• eROI: 1,050%

The use of Fire-Prep 8252 technology allowed CSN also to reduce CO2 emission by approximately 10,190 tonnes/year (considering the whole volume of the not used COG would be burned):

Figure-4: Booster IHI #1 after 6,405 hours running

• COG increased usage: 0.608 dam3/h or 5,253 dm3/year;

• CO2 emission factor for COG: 1.94 ton CO2/dm3 COG

• Potential reduction of CO2 emission: 10,190 tonnes/year

Conclusion: this solution has been very successful helping the company to achieve their TCO reduction and sustainability goals.

Page 140: 2-page abstracts booklet

Process improvements and energy efficiency projects on auxiliary

equipment in Tata Steel Aldwarke Cast Products

A. Patsos*, P.A. Brooks, A. Preston, A. Burgar

(Tata Steel UK)

INTRODUCTION

Aldwarke Cast Products, part of Tata Steel Speciality Steels, have recently embarked on an investment programme that will significantly reduce the energy consumed by auxiliary equipment and contribute to process improvements and plant reliability. Although the electric arc furnaces (EAFs) dominate the energy consumption at the site, auxiliary equipment, such as fans, pumps etc., collectively account for more than 10% of the overall site energy demand. The importance of efficient operation of such equipment tends to get overlooked, partly due to historical operating practice based on continuous production or in favour of larger furnace improvement projects.

Assessing production patterns, operational practices and data, the engineering team managed to quantify the benefits of employing tight control strategies for auxiliary equipment, including the installation of Variable Speed Drives (VSDs) where applicable. The proposed schemes have the potential to collectively reduce the total site specific energy consumption by approximately 5% by 2015.

This paper describes three case studies: lead plant fume extraction optimisation, EAF melting shop fume extraction optimisation and continuous caster closed water cooling energy efficiency project. The methodologies of quantifying energy savings are discussed, along with the proposed means of reducing the energy consumption and the anticipated costs. In addition, post-installation results from the lead plant fume extraction project are reported. Results have shown that the total benefits from these three projects will exceed 14 GWh/y or £1m/y.

ENERGY EFFICIENCY PROJECTS

EAF melting shop fume extraction system (FES)

The main melting shop FES comprises five centrifugal fans powered by 3.3kV, 1.2MW motors that extract fumes to a bag filter plant. The current strategy for control is to run four fans and modulate the suction pressure in a combined extraction duct by fan inlet vanes. Suction from individual processes is controlled

by dampers. Plant measurements have shown a significant spread of damper positions during the operation of the system (Figure 1), after which the relationship between motor power consumption and fan inlet vane position has been established.

Power 381.34e0 0081Damper pos tion

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 10 20 30 40 50 60 70 80 90 100

Inlet Damper Position (%)

Abs

orbe

d Po

wer

(KW

)

Fan 1 Data

Fig. 1: Power consumption vs. fan damper position

The relationship between power and flow for direct-on-line (DOL) motors and vane control is linear. If the control is changed to fixed vane and variable speed drive (VSD), the relationship between flow and power takes the form of an order three curve. Figure 2 shows these two curves (excl. equipment power losses) for the whole system along with the savings expected for this scheme as the flow is altered.

0

500

1000

1500

2000

2500

3000

3500

4000

0 20 40 60 80 100

Fan Utilisation(%)

Pow

er (K

W)

£0K

£100K

£200K

£300K

£400K

£500K

£600K

£700K

£800K

Power DOL (KW)Power VSD (KW)Savings (£Kannual)

Fig. 2: DOL/VSD comparison and expected savings

Based on logged data, the system consumes approximately 22GWh/y at an average motor power of 726kW and a cost of £1.5m/y. The chosen equipment to produce optimum savings is 690V, VSD-controlled motors. The new system comprises five new 3300/690V transformers, motors and low-harmonic drives, additional common duct pressure monitoring, control systems and software. It is expected to reduce the energy consumption to 15GWh/y (incl. equipment power losses) at an average motor power of 439kW, without affecting extraction performance. With the project cost at ~£2.1m, the payback time is expected to be ~4y (incl. reduced maintenance costs).

Lead plant fume extraction system

The bloom caster & secondary steelmaking area (‘lead plant’) has a FES that extracts fumes from 6

Page 141: 2-page abstracts booklet

zones, routed via a plenum chamber to two bag filters. The FES used 4 fixed speed 3.3kV motors (2x650kW and 2x410kW) to drive centrifugal fans, with a total extraction capacity of 126m3/sec (105m3/sec with three fans at the time of the investigation). The number of fans in operation varies according to the processes in operation at any time, the flow demand from each individual extraction zone being summated by the control system to derive a total extraction flow set-point. As with most fixed-speed, sequence-based systems, capacity exceeds demand, which is shown on a typical production day in Figure 3.

Fig. 3: Comparison between capacity and demand of the lead plant FES

The bag filter inlet pressure was controlled by fan inlet vanes and the individual zone extraction rate by dampers to modify resistance in the circuit. The individual zone controls operated accurately, but while ever the fans exceeded the required demand, the zone dampers had to be throttled back to limit flow. Based on logged data, the system consumed approximately 7.1GWh/y at a cost of £450k/y.

A new system has recently been installed, comprising four new 3300/690V transformers, motors and low-harmonic VSDs, control systems and software. Modifications to the control software enabled the inlet suction set-point to be automatically matched to process requirement, with a common pressure reference being used to control the plenum outlet pressure for each operational scenario. In addition, the use of multiple fans in parallel further reduces the energy consumption of the system without affecting extraction performance. As projected at the feasibility stage, the energy consumption has been reduced to 3.4GWh/y (incl. equipment power losses), a reduction of more than 50%. With the project cost at £700k, the payback time is expected to be ~2.5y (incl. reduced maintenance costs).

Bloom caster cooling water system

The system in question comprises two closed cooling water systems (primary side), namely “Machine” and “Mould”, and a secondary cooling water system that extracts the heat of the closed systems via heat exchangers and a cooling tower. The “Machine” system consists of 4x160kW motor-driven centrifugal pumps (MDCP, 2 or 3 on duty) and serves the two

(large and small) bloom caster machines and supporting structures, while the “Mould” system consists of 3x110kW MDCPs (2 on duty) and serves the casting moulds of the large caster. The secondary cooling water system consists of 2x160kW MDCPs (1 on duty) and a cooling tower with 2x45kW motor-driven axial fans. The total system consumes approximately 6.3GWh/y at a cost of £410k/y. Analysis has shown that water circulation temperatures were far lower than design ones, thus there was potential to reduce the flow of the water on the secondary side and hence save energy.

A trial was carried out on the secondary system pump, using a VSD and controlling the temperature of the closed cooling systems to 5oC lower than design. Results showed a drop in power consumption from 150kW to 25kW (Figure 4) with no adverse impacts on production. A similar loop control on the cooling tower fans is expected to generate extra, albeit lower, savings. It is estimated that the savings on this system only will exceed £70k/y (~70%).

0

20

40

60

80

100

120

140

160

Time

Pow

er c

onsu

mpt

ion

(kW

)

DOL

VSD

Fig. 4: DOL/VSD comparison on power consumption

Further investigation on the primary side systems showed that, depending on plant operation, cooling water is only required for 15-50% of the time, contrary to the current regime that circulates water constantly. Due to the complexity of the system and the pressure requirements of areas such as mould cooling, VSD control is not believed to be the optimum solution – rather a tight on-off control would provide optimum benefits that can exceed £150k/y or 50% of the primary system current energy consumption. Further work is required in this area, that if implemented would reduce the total energy consumption of the whole system by 3.5GWh/y.

CONCLUSIONS

Overcapacity and ageing equipment are the main causes of energy wastage in the auxiliary equipment at Aldwarke Cast Products. Investigation and recent investment has shown that by employing tight control strategies and/or VSD control, up to 50% energy and cost savings can be achieved, without impacting on plant operation.

Page 142: 2-page abstracts booklet

From the energy audit to the final performance tests: success story

of a furnace revamping

L. Ferrand (CMI Greenline Europe)

J-L. Lambert (Vallourec Groupe)

C. Bourge (CMI Greenline Europe)

E. Carré (Vallourec & Mannesmann)

M. Varlez (Vallourec & Mannesmann)

C. Constant (CMI Greenline Europe)

INTRODUCTION

The premium seamless tubes forging mill line of V&M Aulnoye-Aymeries (France) includes a heat treatment process to autenize (>900°C) and temper the tubes (between 550°C and 800°C). Two furnaces, built in 1982, were dedicated to each process. In 2010, a project was launched to improve the performances of one of the furnace. The goal was to improve the heat treatment quality (+/-5°C of heating uniformity) while reducing operating costs: only one furnace operating for all purposes, and minimized natural gas consumption1 and NOx emissions. CMI Greenline was chosen to implement this project, from the initial audit to determine the optimal technico-economical choices, to the erection of the modification and supervision of the commissioning. Main challenges were the high targets of performances, the necessity to integrate solutions in the existing frame of the furnace at lowest costs, and the short stoppage constraints for erection.

ENERGY AUDIT

Methodology

The aim of the audit is to :

• Understand the current working conditions and performances of the furnace.

• Determine the best technico-economical choices to reach the performance targets

1 The Group V&M targets 20% of energy savings on all plants by 2020, the reference year being 2008 (Greenhouse Project).

The study was done by a combination of experimental data analysis and numerical simulations. The idea was to set a virtual simulation tool of the furnace, validated by experiments, and use this tool to investigate potential solutions.

Thermal Expertise

CMI Greenline uses two complementary tools for such problems:

• CFD (Computational Fluid Dynamic) tools to properly design furnace enclosure and integration of heating technologies (cf. Figure 1).

Figure 1 : help of simulation tools to secure the

design.

• Nodal network tools (cf. Figure 2), for fast computing of thermal heat transfers and heat consumption. These tools are internally developed, and are basically based on an original combination of 1D, 2D or 3-Dimensional solvers, based on the nature of heat transfer mode (ex : 3D for radiation factors, 1D for conduction through the insulated walls).

Figure 2 : nodal network simulation tool.

Both approaches have been used to investigate potential technical solutions:

• Different furnace profiles: number of zones, roof nozes, separation screens, etc.

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• Different combinations of heating equipment solutions : centralized recuperator, regenerative burners, auto-recuperative burners, oxy-fuel burners, electric heaters

• Different ways to minimize heat losses: uncooled charging/discharging rolls, choice of insulating parts.

• Different process solutions: pulse firing vs. proportional control, furnace pressure control devices, air/fuel ratio accurate control solutions.

Figure 4 : engineering under Autodesk Inventor. Decision criteria and choices Main key data of the erection phase are the following: Through the audit study, V&M and CMI Greenline agreed on best technico-economical solutions, based on the following criteria:

• 8 weeks, 350 workers, 46 external companies • 3x8 shifts, 6 days a week • High standards of safety (“top 5” procedures), no

accident over the full period. • Energy savings (cf. Figure 3) and low NOx emissions.

• Furnace flexibility, to ensure high quality for a large spectrum of working conditions.

• Maintenance costs. • Erection risks and feasibility.

Figure 5 : new heating equipment from ELSTER-LBE, operated with ONOFFSoft by CMI.

PERFORMANCES

The furnace was qualified for production through measurement trials with tubes equipped with thermocouples. The uniformity proved to be excellent, both in austenizing mode and tempering mode. The thermal consumption was reduced by 32% (cf. Figure 6). CEE (Energy Efficiency Certificates) were delivered by EDF in 2011.

Figure 3 : energy costs of different solutions.

The basic design choices were the following :

400d-09 j-10 f-10 m-10 a-10 m-10 j-10 j-10 a-10 s-10 o-10 n-10 d-10 j-11 f-11 m-11 a-11 m-11 j-11 j-11

450500550600650700750800850900950

10001050110011501200

Con

sum

ptio

n [k

Wh/

t]

V&M Aulnoye ‐ Tubes heat treatment Furnace

Before Revamping

Tuning / Qualification

Full Production

-32% Energy Savings

• 15 control zones (8 zones previously). • 72 Auto-recuperative burners + 5 hearth burners

in the last zone to ensure uniformity.

• ONOFFSoft Pulse firing, developed by CMI for optimal firing sequences.

• Un-cooled mechanical parts with special design and choice of alloys.

Figure 6 : measured energy saving.

This project has shown that a rigorous initial audit, helped by numerical modeling, combined with efficient project management, are key factors for the final success of complex thermal process improvement.

PROJECT IMPLEMENTATION

The project was implemented between January and September 2010. The engineering was completely designed with Autodesk Inventor 3D (cf. Figure 4).

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Towards low energy consumption & low CO2 production:

Steelmaking plants, a roadmap

R.Nicolle (Consultant)

1. INTRODUCTION

Production processes of integrated steel plants, mostly based on coal as a main energy source and chemical reactant, contribute to the production of greenhouse gases. They require 18,8 GJ energy and release more than 2 tons CO2 per ton hot rolled coil. Energy saving has long been an important target with impressive results in the past. Despite the fact that most plant reactors have reached their minimum consumption, there are still strong incentives to further save energy for both environmental and cost reasons. The proper use of the plant internal gases and a strong policy of energy savings may decrease the present figures by more than 20%.

COKING COAL 423 kg/t HRCINJECTION COAL 200 kg/t HRC

ANTHRACITE 32 kg/t HRCELECTRICITY 400 kWh/t HRC

CO2 from fossil fuels 2020 kg/t HRC

56 kg/t HRCCO2 elec. 370 g/kWh

COKE SALES 0 kg/t HRC

CONSUMPTION

PRODUCTION

CO2 from bought electric

Figure 1: 6Mt integrated plant energy consumption

2. COAL BASED PRODUCTION: A DEAD-END?

From an energy viewpoint, the classical blast furnace route is characterized by:

- an almost unique source of energy: coal

- an excess of the production of process gases that are converted into electricity in the power plant with a rather low efficiency

- a deficit of the whole plant energy balance that requires buying electricity from outside. The internal and external electricity have different values in terms of cost and CO2 content.

Not only the energy consumption of the iron-making processes has reached its asymptotic line, but the remaining energy savings may be poorly valued

(mostly as increased excess gases in the power plant or low temperature fluids).

Figure 2: Materials & Energy fluxes in the 6Mt plant

The above figure give the material and energy fluxes of a classical 6Mt integrated plant; figures are given with reference to 1 ton hot rolled coil.

3. IMPROVING THE VALUE OF INTERNAL GASES & USING MORE ELECTRICITY

Indeed, gases produced by the iron and steel-making plants have rather low LCV values.

BF gas CO gas BOF gas

CO 26% 5% 72%

CO2 25% 2% 14%

H2 5% 63% 2%

CH4 25%

N2 45% 2% 12%

LCV kJ/m3N 3763 20580 9283 Figure 3: Characteristics of the plant gases

To raise up the energetic performances of blast furnace gas, it must be either enriched with high LCV value gases, or preheated or burned with oxygen enriched air.

On the other end coke oven gas be used to produce high value fuels (hydrogen, methanol, ethanol, DME...) or just as a chemical reactant to

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Flame temperature

1200

1250

1300

1350

1400

1450

0% 2% 4% 6% 8%

% Rich gas

Flam

e Te

mpe

ratu

re (°

C)

Flame Temperature

1200

1250

1300

1350

1400

1450

0 0,02 0,04 0,06 0,08

m 3 added O2/m3 air

Flam

e Te

mpe

ratu

re

Flame Temperature

1200

1250

1300

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0 100 200 300

Preheating tem perature (°C)

Flam

e te

mpe

ratu

re

For this overall production almost no further carbon source will have been used with respect to the initial reference plant, which will mean a decrease of 14% of the CO2 production and an increase of 21% of the production. But the quantity of imported electricity will increase strongly.

Figure 4: BF gas flame temperature

produce DRI. As the production of one ton DRI requires about 9GJ/t DRI, the total production of COG of the plant may produce more than 200kg DRI per ton hot coil.).

Using all the produced COG to produce DRI will imply using BF+BOF gases for the reheating furnaces, improving the heat efficiency of reheating furnaces (at present about 60%) through the use of pre-heaters or stoves, improved burners with energy recuperation, low fumes volume by oxygen enrichment and even decreasing the heat requirements of the reheating furnaces (direct charging, low temperature heating...) as well as improving the furnace dynamic management (in relation with the energy cost and availability. A target decrease of the energy consumption of the furnaces of 30% may be reached as a result of all these actions.

The production of 1,3Mt extra steel will only require 1,3MWh/t hot rolled coil. This will be the result of both the energy savings and the introduction of the short route to near net shape casting.

COKING COAL 348 kg/t HRC

INJECTION COAL 164 kg/t HRC

ANTHRACITE 26 kg/t HRC

ELECTRICITY 366 kWh/t HRC

CO2 from fossil fuels 1664 kg/t HRC

129 kg/t HRCCO2 elec. 370 g/kWh

COKE SALES 0 kg/t HRC

CONSUMPTION

PRODUCTION

+ CO2 from bought electricity

4. A NEW INTEGRATED PLANT: PRODUCING 1,3Mt EXTRA STEEL WITH ONLY ELECTRICITY

Figure 6: 7,3Mt plant energy consumption The 200kg DRI per ton hot rolled coil may be partly used either in the blast furnace or in the steelmaking plant to produce extra metal with low energy requirements, but these additions may be limited by the downstream of the plant (continuous casting, hot rolling).

5. CONCLUSIONS

Energy savings can still be achieved in the blast furnace-BOF route for steel-making, thus leading to lower CO2 emissions. With the existing techniques, a decrease of about 20% in the energy consumption and in the CO2 production is within the reach.

This will require actions to improve the use of the plant internal gases and strong decreases of the reheating furnaces specific energy requirements.

The introduction of the short DRI-EAF route into integrated plants may allow a progressive shift from the high coal energy-consuming BF route to the high electricity/natural gas-consuming DRI/EAF route that requires less energy than the BF route and even to the increased use of scraps through the much lower energy EAF furnace route in the recycling society.

Figure 5: 7,3Mt plant scheme

A new parallel line associating pre-reduction with an electric arc furnace and a near net shape casting will avoid possible plant bottlenecks and allow the production of an extra 1,3Mt hot rolled coil beyond the 6Mt coils produced by the reference plant.

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Session 10: Secondary metallurgy and refractory

Table of Contents

10.1 Optimised steel ladle upper ring technology P. TASSOT (Calderys Deutschland), Germany

10.2 Wear mechanisms of Al2O3-MgO spinel forming refractories used in steel ladle impact pads J. POIRIER (CEMHTI CNRS), T. CORDONNIER (ArcelorMittal Global R&D), P. PRIGENT (TRB), M.L. BOUCHETOU (CEMHTI CNRS), E. ARFAN, N. SCHMITT (LMT Ecole Normale Supérieure, Cachan), France

10.3

Technical improvements using air cooled staged oxy-air-gas burners for ladle heating M. BENTIVEGNI, T. BÉNARD (Vallourec Research Aulnoye), O. DESURMONT, R. BRIEND (Vallourec & Mannesmann), N. DOCQUIER (Air Liquide), P. BOUSSARD (PB Consulting), France

10.4

How to improve sustainability, safety, health and doing quality and cost-savings (up to 20%) with new injection technologies and cored wire in steelmaking? M. SCHATZ, C. LENOIR, S. GERARDIN (AFFIVAL), A. BINNINGER (Vallourec & Mannesmann), France

10.5

Inclusion thermodynamics in high Al and high Mn alloyed steels J.J. PAK, M.K. PAEK, K.H. DO, J.M. JANG (Hanyang University), Korea

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1. INTRODUCTION Steel is one of the most attractive, most robust and most sustainable materials in the world. The global steel industry is facing even more significant challenges. Many steelmakers continually focus on margin generation and optimization of production facilities. Without high performance refractories, this challenge will not be achievable. Refractories are a significant part of the process and can contribute strongly to these results, influencing the efficiency and availability of the process through improved performance. First, it is important to understand the main factors affecting the stability of the upper lip in the steel ladle : - Mechanical stress due to deskulling with an

engine on the ladle tilting device. Important properties for the material used here are hot and cold mechanical strength.

- Thermal stresses due to cycling during converter or EAF tapping. The key property in this case is good thermal shock resistance for the material used.

- Thermal expansion of the wall lining can quickly become an issue if not correctly managed.

- Corrosion, particularly in the case of aggressive vacuum treatment in a VTD, where the steel and slag can foam up to the top of the ladle and sometimes higher.

Several solutions are now available to prolong the service life of the slag line:

• Using ramming materials • Traditional LC castable • Precast shapes containing a high

amount of steel fibres This paper reviews some of these solutions and some new possibilities 2. RAMMING MATERIALS OR

CASTABLES? The most common solution for absorbing the expansion of the wall is the use of a ramming

material. The thermal expansion of magnesia-carbon bricks is 1.5% at 1000°C and, considering an average height of 4 m, the total expansion will be more than 6 cm. This expansion can be partially compensated by the joints in the MgO-C brick lining, but it is necessary to address the remainder with a material or a joint that can compensate. 2 solutions are available:

Optimised steel ladle upper ring technology

Patrick Tassot, CALDERYS

- using a ramming mix to introduce some plasticity: this is a very common solution. The drawback is the relative weakness of these materials. In the case of heavy skull and significant mechanical abuse, the strength will not be sufficient and sooner or later the joint will open. At this point it will be necessary to repair the ladle top for avoiding the dismantling of the bricks, particularly in the case of SU-shape.

- An alternative solution is to use a castable installed over a joint or a ramming material.

- A typical material for this application is an andalusite-based LC castable, which is highly resistant to thermal shock and still features good mechanical resistance.

This solution has been successful in a majority of plants for full ladle campaigns with minimal repairs. However installation time, including preheating, can be an issue. Such castables require a carefully regulated preheating schedule and a long preheating time. To minimize preheating time, precast blocks can be installed in the Lip. But a special solution also exists if mechanical resistance is particularly needed. In this case we can propose stainless steel fibre reinforced blocks in which the quantity of fibres is close to 30 % and the refractory material consists of a slurry [CALDE WIRE MIX concept]. CALDERYS can provide the entire spectrum of solutions, and is now also proposing a new generation of castable featuring mechanical properties similar to those of the LC castables, but allowing rapid preheating compatible with the typical preheating curve for bricked ladles. 3. THE NEW GENERATION OF QUICK DRY

NO CEMENT CASTABLES The set times of castables vary from one product to another depending on the binder and additive package, but generally a dense castable needs several hours to set. Gas permeability of the refractory, especially its variation with temperature in the range 20-400°C, is a critical parameter governing overall behaviour of refractory castable during drying1. The CALDERYS QD NCC bond forms due to specific surface interaction / gel formation between the ultra-fine pure mineral reactants when in contact with water.

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QD NCC bond gives the ability to formulate pure alumina, alumino silicate or basic castables that can be mixed using the same equipment as for cement bonded castables.

Fig.2: Some industrial references with QD no cement containing products

Steam pressure measurements realized on LCC or ULCC and the QD NCC until 600°C are clearly showing that CAC castable reaches the maximum steam pressure close to 20 bars in comparison with the QD materials with 6 bars. QD NCC products show permeability 2 to 5 times higher compared to CAC bonded formulations. The immediate consequence is the possibility to heat-up QD NCC products much quicker than with CAC-containing materials, permitting a reduction of 60% of this critical step of refractory lining installation. Critically the QD NCC technology is playing a positive role in energy saving and SOx reduction. 4. SOME INDUSTRIAL SUCCESS STORIES Since early 2010 CALDERYS has been using these QD products in various fields. Performance optimization in the ladle lip area has been achieved using this solution at several plants Though at some steel shops the andalusite or bauxite-based materials are suitable, these are not always sufficiently resistant to corrosion from the slag. This is the case in particular for a secondary metallurgy process using a vacuum tank degasser. During this process, it is important for the foaming of the steel and slag to reach the lip. CALDE™ CAST NT 92 QD provides the best result in this case and can be strongly recommended (Fig. 1).

Fig 2. shows some case reference steel plants using these new materials with success 5. CONCLUSIONS: In today’s competitive environment, steel production and productivity are critical issues. Therefore the availability of the processing equipment is of paramount importance. CALDERYS is leading the way in process efficiencies, lower costs, and better refractory performance. Calcium Aluminate Refractory Cement has

made it possible to improve the high temperature properties of castable refractories considerably, mainly because of the absence of low-melting phases; however, the cement is a weak point in the microstructure in particular due to the necessity to manage the hydration/dehydration during curing and preheating.

CALDERYS has recently developed a new generation of no-cement castable that is maximising the advantages and avoiding the previous disadvantages of colloidal silica. No curing is necessary and the heating-up time is much reduced. Additionally, the material has very good thermal shock resistance. A full family range including andalusite, bauxite, corundum, tabular alumina, and MgO is now available and can help to meet the new challenges of the steel making industry for the next decade.

Fig.1: Criteria of selection of the QD-products

1 P. Meunier , L. Ronsoux : Permeability and dehydration of refractory castables. Proceedings Unitecr’05, pp.799–803.

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Wear mechanisms of Al2O3-MgO spinel forming refractories used in steel ladle impact pads

J. Poirier, CEMHTI CNRS - T. Cordonnier, ArcelorMittal - P. Prigent, TRB - M.L. Bouchetou, CEMHTI CNRS

E. Arfan, LMT-Cachan ENS - N. Schmitt, LMT-Cachan ENS INTRODUCTION Alumina-magnesia/self-forming spinel castable is used successfully in impact pads of steel ladles. Its degradation is a complex and multi physical phenomenon that requires a double approach, in both thermo-chemical and thermo-mechanical domains, to be clearly understood. In order to increase impact pad, and so steel ladles lifetime, a research project was carried out by ArcelorMittal, TRB refractories, CEMHTI CNRS and LMT-Cachan ENS, the objectives being: - to understand the phenomena of degradations of

self-forming spinel castables; - to identify the key parameters controlling the wear

mechanisms; - to propose solutions to develop more resistant

refractories. DEGRADATIONS OF IMPACT PADS IN LADLE The damage of the pad (Fig.1) is characterized by: - a macro-crack, situated at around 45 mm from the

hot face and due to the thermal stresses; - micro-cracks, parallel and perpendicular to the

surface in contact with liquid steel, which deteriorate the resistance of the pad. Both types of cracks spread across the bonding phase of the castable (matrix) and in the interface matrix-aggregates.

The main mechanisms of degradations are: - a micro spalling initiated by thermal shocks; - an erosion due to the steel flow during the filling of the steel ladle; - a corrosion by rich alumina slag.

Fig. 1 Cracks and corrosion in an impact pad The thermal shock is caused by the contact between the melted steel at 1600° - 1650°C and the hot face of the pad (which has cooled down to 1200°C when the steel ladle is empty). In contact with the slag, the alumina aggregates react with the lime of the slag to produce lime aluminates: CA6 and CA2. At the same time, the matrix reacts with slag to produce spinel. Some oxides from the slag (Al2O3, FeO, MgO,

MnO) are trapped and take part in the formation of the spinel (Fig. 2). CA2

(Mg,Mn,Fe)O(Al,Fe)2O3

i lCA6Al2O3

a b

Fig.2 SEM observations of an alumina aggregate and of the matrix after slag attack

RELATION BETWEEN MICROSTRUCTURE, PHASE CHANGE AND COMPOSITION It is crucial to control the volume expansion of the castable caused by the formation of spinel, CA2 and CA6 in order to avoid the formation of cracks in service. Three major parameters have been highlighted: - the amount of lime. The lime reacts, at 1000°C, with

alumina to form CA2 with a volume expansion of +13.6%. At higher temperature, around 1400°C, CA6 formation causes a volume expansion of +3%.

- the amount of microsilica in the matrix: the microsilica can limit the volume expansion by the formation of a ternary phase (anorthite, gehlenite at high temperature).

- the size of the magnesia grains. Figure 3 plots the mineralogical and vitreous phase amounts in different matrices fired at 1600°C that were determined at room temperature, by x-ray quantitative analysis, using the “Rietveld method”.

5 cm

0 21

0102030405060

Corun-dum

CA6 Vitreous phase

M1 M2 M3 M4 M5 M6

wt%

0102030405060wt%

Anor- thite

Corun- dum

CA6 Vitreous phase

Anor-thite

Spinel Spinel

Fig. 3 Phases in different matrices, fired at 1600°C - a high micro silica content (M3,M6) increases the

spinel amount and the vitreous phase and decreases the CA6 mineral (hibonite). But, for a very high silica amount, silica formed ternary phase (anorthite) by reaction with alumina and lime

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included in the matrix. In this case, there is no formation of CA6;

- low calcium aluminate cement content (M1,M2,M3) decreases the CA6 amount. For a high amount of microsilica (M3), the lime is included in liquid phases at high temperature.

Thermal expansion analysis was performed on different matrices which were pre-heated at 1000°C (Fig.4). Higher amounts of microsilica (2 %wt) lead to a lower expansion at temperatures above 1300°C. This reduction in expansion is delayed by lowering the calcium aluminate cement content. For matrices M3 and M6 this is explained by the high amounts of vitreous phase and a liquid ternary phase at high temperature. For matrix M2, even with the small amount of CA6 formed, liquid phase appears above 1450°C. Matrices M1, M4 and M5 show a high expansion above 1450°C. These matrices are those for which the CA6 content is higher.

o

Fig.4 Thermal expansion of matrices CORROSION TEST Corrosion tests were carried out using the static crucible (Fig. 5).

Fig. 5 Corrosion of Al2O3-MgO crucibles

These corrosion tests showed that impregnation by slag has promoted the formation of expansive phases CA6 and CA2. These phases lead to thermo-mechanical strains causing cracks formation (Fig.6).

Fig. 6 Micrographs on corroded area close to a crack

The corrosion of alumina-magnesia self-forming spinel castables is depending on the cracks formation, itself depending of expansive phase formation.

THERMOMECHANICAL BEHAVIOUR Lab tests were carried out to determine the thermo mechanical properties: elasticity, inelastic strain, viscosity, toughness (Fig.7). A model (thermo-elasto-viscoplastic) taking into account phase changes was developed.

Fig.7 Stress-Strain curves at high temperature

The degradation mechanisms were analysed by finite element simulations and permitted to highlight: - the depth of expansive phase formation and the macro cracking (Fig.8); - the level of thermal stresses along the steel ladle rotation cycle and more especially brittle erosion; - the possibility to develop micro spalling during tapping at BOF thanks fracture mechanics analysis.

Fig.8 Temperature profiles allow to evaluate the depth

of the layers subjected to phase transformations

Matrix M5 Matrix M2 Before tapping at BOF, there are preexisting cracks and slag impregnation. During tapping, thermomechanical shocks lead to microcracking and opening of preexisting parallel cracks. During secondary metallurgy, ductile erosion and phase changes lead to expansion and macro cracking. At the end of continuous casting, descending thermal shock leads to opening of cracks perpendicular to the surface and slag impregnation. CONCLUSION To increase the life time of Al2O3-MgO castables, it is advised to control volume expansion to avoid the formation of cracks and to limit the slag penetration of slag. An optimized formula, based on an increase of the silica fume content, a decrease of the cement content and the use of fine seawater magnesia, was validated by thermo mechanical and corrosion tests. REFERENCES P.Prigent et al. Industrial Ceramics, 3 209 218 2010 E. Arfan et al. ICC,Verona (Italy) 2008

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Technical improvements using air cooled staged oxy-air-gas burners

for ladle heating

M. Bentivegni (Vallourec Research Aulnoye)

T. Bénard (Vallourec Research Aulnoye)

O. Desurmont (Vallourec & Mannesmann France)

R. Briend (Vallourec & Mannesmann France)

N. Docquier (Air Liquide)

P. Boussard (PB Consulting)

1-INTRODUCTION

A ladle is a container that allows the transport of liquid steel protected in the upper surface by a slag layer from the arc furnace to the continuous casting process (Figure 1).

Figure 1: ladle general scheme

The simplified structure of a ladle is composed by an external metal shield, a safety layer of bricks and an internal layer of refractory bricks. The refractory bricks layer is regularly replaced after a certain number of castings, that because the thermal shocks given by the hot liquid steel tend to damage it. In order to reduce the thermal shocks, the internal surface of the ladle is progressively pre-heated. The upper cap is also the seat for a gas burner and it is sustained by a

fix support. Typically the heating of the empty ladle is done progressively passing the ladle in different stations with different burner power and temperature set up. In the V&M steelmaking plant of S.Saulve three progressive preheating stations are used and a final station just in front of the arc furnace gives the final bricks temperature. Industry data show that two thirds of the temperature drop of the molten steel occurs in the first 45 minutes after tapping and that the temperature drop is directly attributable to heat lost to the ladle lining [ 2 ].

In this paper we will deal with the last heating station which is dedicated to ladle temperature soaking and homogenizing, waiting for the hot liquid steel casting.

2-LADLE BURNERS TECHNICAL SOLUTIONS

The simpler technology for burners uses air as oxidizing agent. The main difference between an air-gas burner and an oxy-gas burner is in the flame adiabatic temperature, the length of the flame and in the temperature of the flue gases [ 3 ]. The main reasons for these differences are in the nitrogen presence that dilutes the combustible and oxidant agent and (if we save the same burner power and the same burner dimensions) lengthen the flame [ 1 ].

The aim of using an air-oxy-gas burner is to find a compromise between a high radiative but short flame and a long and colder one. The final goal is to have a better ladle temperature homogeneity all along the heating. The air-oxy-gas burner functioning scheme is showed in Figure 2; the use of a staged combustion helps reducing NOx even using an oxygen enriched burner [ 1 ]. The ratio air/oxygen of this burner is variable, which gives more flexibility in system set up optimisation. The optimisation of burner regulation is performed experimentally on the ladle and in partnership with the AirLiquide simulation department.

Figure 2: air-oxy-gas burner functioning scheme [ 2 ].

3-VALLOUREC S.SAULVE PLANT LADLE TEST

The trial target is to measure the temperature homogeneity up-down of a ladle using three different burner functioning modes. Three ladles equipped with thermocouples were at first preheated until around 750 °C in preheating stations and put in final soaking station to reach the final temperature of 1040 °C. As shown in Figure 1 and Figure 3 the thermocouples were put in the refractory, out of direct flame

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influence, in the upper border of the ladle and in the porous plug hole. The three burners were used with the same nominal gas power (1800 kW) and using an oxidizing agent excess (air, or oxygen, or air+oxygen) of around 15 %.

Figure 3: trial preparation

The heating of the ladle can be divided in two parts: heating and soaking phase. During the heating phase the burner power is maximal, in soaking the burner regulates at lower rates as showed in Figure 4.

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T2

Figure 4: burners gas power consumption

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Regulatio  TC1

DT= T2‐T1

T2set up temp.

+240 K ↓

‐70 K ↑

Figure 5: temperatures in upper and lower side of the ladle

The measured temperatures in Figure 5 show that the oxy-gas functioning mode allows reaching the soaking temperature in 55 minutes. For the air-oxy-gas this time is 30 minutes longer, that because of the presence of the air as oxidizing agent. In the second

case the staged flame allows having more temperature homogeneity in the first phase of the heating (the difference of temperature up/down is around -10 K), that is the most important interest of using this technology. The final temperature difference for these two technologies is 70 K, with the lower part of the ladle hotter than the upper part. For the air-gas burner the heterogeneity reached at the end of the 2 hours test is + 240 K (the lower part of the ladle is colder). This high heterogeneity shows that this last technology is the less adapted to reach the wanted target.

The external surface of the ladle has also been analyzed by thermography. The air-oxy-gas and oxy-gas behaviour is more homogeneous with an estimated external temperature difference of 20 K (15 between the lower part and the middle and 5 between the middle and the upper part of the ladle). For the air-gas we found an external temperature difference of around 55 K, with the upper zone colder than the lower zone. That value seems in opposition to the temperature T1 measured by the cap burner regulation thermocouple but the colder smokes coming up from ladle and the lower radiative power of the flame give finally a lower refractory temperature.

Figure 6: external ladle IR thermography

4-CONCLUSIONS

Three burner functioning modes have been tested in V&M plant of S.Saulve. The oxygen enriched technologies show better temperature homogeneity compared to air-gas; that was confirmed also in the external ladle surface by thermography. The air-oxy-gas regulation is even more homogeneous in first part of heating, where 10 K temperature difference is reached because of the presence of the staged combustion with both oxygen and air. The impact of a better thermal homogeneity and the optimisation of the ratio air/oxygen on the life of refractory are at present under study.

BIBLIOGRAPHY [ 1 ] C.E. Baukal Jr : “Industrial burners handbook”, 2004 CRC Press

[ 2 ] AirLiquide-American Combustion: “Pyretron combustion technology”, 2005 AL-AC White Papers

[ 3 ] Kobayashi et al.: “Technical and economic evaluation of oxygen enriched combustion systems for industrial furnace applications”, in Industrial Combustion Technologies, Ed., American Society of Metals, 1986

Page 153: 2-page abstracts booklet

How to improve sustainability, safety, health and doing quality and cost saving (up to 20%) with new injection technologies and

cored wire in steelmaking?

M. Schatz, C. Lenoir, S. Gerardin (Affival Group, 59730 Solesmes, France), A. Binninger (V&M

France, 59880 Saint-Saulve, France)

PREAMBLE:

“Someday, I hope someone will have the inclination, the will and the investment to address the whole matter of increasing the efficiency of calcium in-ladle treatment… This could be an industry-wide opportunity, because it involves and require the good will and cooperation of all those with great self interest in control and maximum in-ladle efficiency in converting alumina inclusions to calcium aluminates” (E. Tugrul Turkdogan, AFFIVAL In-Ladle Treatment News, vol I, No 3, 1986)

30 year ago in France, steelmaking achieved a great improvement with the industrial development of a new technology: cored wire. This was a new process for the addition of ferroalloys and treatment of liquid steel, especially concerning the calcium treatment. Steelmakers then improved quality of liquid steel, works conditions and safety by replacing partially or totally lumpy additions which were generating lots of dust and pretty low recoveries. 30 years later, cored wire is widely spread out around the world and is still continuing to bring great advantages for the treatment of metallic liquid baths (steelmaking, foundry and other liquid metals).

Using cored wire is not taught in any university but directly on ground floor of melt shops. Nevertheless, continuous efforts of Research and Development led on cored wire allow today to reach a new stage.

Quality steelmaking and Cored Wire became now intimately linked to each other. Some recent progresses (some of them are even patented) in feeding technologies and new generations of cored wires allow steelmakers to improve the quality of steel while cost of metallurgical treatments are tremendously decreased (up to 20%) by a reduction of ferroalloys consumption and a better use. These new technologies are then true and sustainable solutions for cost-savings but as well for quality, health, safety and environment.

Cored wire has been created by steelmakers for steelmakers. 30 years ago, VALLOUREC plant in Solesmes (nowadays AFFIVAL SAS) has developed the first CaSi cored wire to be used in ladle. Since

then, cored wire is widely used for any sort of applications and processes with any kind of chemical elements:

Steel De-Oxydation Addition and Trimming Machinability Improvement Re-Nitriding Inclusion Shape Control

CORED WIRE OR LUMPS?

Most of the ferroalloys and pure elements (e.g. FeTi, FeNb, FeV, C, Ca...) as powder form can be used in cored wire. Some of them may even be blended together (for instance CaFe).

Even if for certain treatments, cored wire technology remains the unique solution for addition into liquid steel, for other cases, especially when the addition is made by lumps, an evaluation of advantages has to be settled. Then, it’s not rare that cored wire is a source of clever, quick and profitable improvements. It has been shown, for instance, that the standard deviation of recoveries with cored wire is tighter than the one obtained with ferroalloys as lumps form. The figure 1 illustrates the difference between both.

Fig. 1: cored wire vs Lumps

Thanks to a more accurate addition, steelmaker may then reduce the consumption of raw materials, synonym of huge cost-savings.

QUALITY THANKS TO RELIABLE CORED WIRE TECHNOLOGY, THREE MAIN CONDITIONS...

The first condition to get a reliable core wire is to be sure about the quality of raw materials packaged and sheath itself (too many products on the market will never be able to provide quality and cost-savings due to poor quality). Commonly, 30%-gaps of yield may be often observed between same cored wires but made of different quality of raw materials. Buying too cheap may drastically impact performances of steel plants and do easily generate extra-costs which are far away from the “cost-saving” apparently done on initial price.

The second condition is the consistency of powder metric weight in order to insure the steelmaker will add the right quantity corresponding to the

Page 154: 2-page abstracts booklet

specification to be reached. This is the way to keep under control quality of steel and cost-savings coming from cored wire use. As understood from the Fig. 1, steelmakers may save from 5% to 20 % of their consumption thanks to cored wire vs lumps, but only if the powder metric weight is mastered. In the same way, works conditions around ladle furnace are tremendously improved by reducing dusts and fumes, especially for hazardous or CMR materials such as lead for instance.

The third condition may appear secondary but finally, reveals huge advantages: feeding equipment. Nowadays, wire feeders fill a place more and more important because of their great impact on wire performances fed into liquid steel. As all reliable feeders are connectable to control room, it is also a way to reduce manpower risk and cost while safety is improved.

STEELMAKING JUMPS INTO A NEW ERA.

In a world where raw material prices are more and more volatile, where these raw materials themselves are less and less available, one of the technical solutions is to reduce their consumption while costs are reduced and the quality of the final products is stabilized or even improved.

Recent R&D works have been conducted on both cored wires and feeding technologies. A result of these efforts makes steelmaking passed into a new era, especially for calcium treatment but not only.

A new type of cored wire (initially developed thanks to the support of V&M St Saulve plant and patented), made of insulating layer, has been designed for improving calcium treatment, the key-point regarding the good castability in continuous caster. Associated to this new calcium wire, new feeding technologies (patented) have been also established as a new concept: Vertical Injection. Fig. 2 shows such equipment.

Fig. 2: Vertical Injection

This combined technology is particularly well adapted for reactive and hazardous products like calcium which reacts violently in liquid steel. Nevertheless, this concept of Vertical Injection has been extended to any kind of cored wires. Indeed, this vertical feeder / straightener can be used for the injection of standard cored wires which improves their performances (reduction of 25% of CaFe consumptions for instance) and consequently, increase cost-savings for steelmakers.

This equipment is able to straight and simultaneously to feed the wire into the ladle. The powder is then released very deeply in ladle. Calcium yields are then tremendously increased while standard deviation is reduced drastically. Nowadays, it is not unusual to feed only 70 grams of calcium per ton of liquid Silicon-free steel cast in Thin Slab Caster whereas it would need more than 500 grams of CaFe per ton for getting a good castability during casting. This difference of calcium consumption brings 20% cost-savings on the final treatment cost (according to the current prices of products). Additionally, since reactions during injection are mastered (calcium released deeply in ladle), several other advantages can be shown such very low or nil pick-up of nitrogen, less important wear of refractory bricks, less fumes, less splashing (better safety).

CONCLUSION:

Developed 30 years ago by VALLOUREC on its plant in Solesmes, continuously improved, cored wire is nowadays a reliable solution for the improvement of sustainability, safety, health and doing quality and cost saving. AFFIVAL SAS, thanks to its R&D works takes part in the changes of steelmaking into a new era. Vertical Injection has been designed initially for calcium treatment with insulated wires. Very low consumptions of calcium allow huge yearly cost-savings for end-user while steelmaking process is secured. Extended to the standard cored wires, steelmakers are now able to enhance their final costs thanks to Vertical Injection.

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Inclusion Thermodynamics in high Al and high Mn Alloyed Steels

J.J. Pak (Hanyang University, Korea)

M.K. Paek (Hanyang University, Korea)

K. H. Do (Hanyang University, Korea)

J. M. Jang (Hanyang University, Korea)

1. INTRODUCTION

Recent development of high Al and high Mn containing steels such as TRIP and TWIP steels for the next generation steels placed great challenges to steelmaking and casting processes because various inclusions such as AlN, Al2O3 and MnO·Al2O3 can be formed due to high affinity of Al and Mn with N and O in liquid steel. Among these non-metallic inclusions, AlN is a dominating inclusion and it is considered as a detrimental phase for hot ductility of steels. In order to control the formation of AlN inclusions, the thermodynamics of AlN formation in high Al-Mn alloyed steels should be known. In the present study, the N solubility and the critical [Al] and [N] contents for AlN formation in these steels were determined over wide ranges of melt composition and temperature. Thermodynamic parameters determined in the present study can be used to estimate the critical [N] content for the onset of AlN formation in normal TRIP and TWIP steels as a function of melt temperature.

2. EXPERIMENTAL PROCEDURES

The metal-nitride-gas equilibration experiments were carried out using an induction furnace to determine the thermodynamics of Al, N and AlN formation in liquid Fe-Mn-Al alloys.

After melting 500g of high purity electrolytic iron under an Ar-10%H2 atmosphere by a high frequency induction furnace, the nitrogen partial pressure was controlled by a mixture of Ar-10%H2 and N2 gases. Al addition and sampling were repeated until a stable AlN layer was formed on the surface of the iron melt. After the saturation of AlN in liquid iron, Mn was added up to 22%. After each Mn addition in liquid iron, the new equilibrium AlN solubility was attained within 2 h. The effect of Mn on the N solubility in liquid Fe-Mn alloy melts was also determined using the metal-gas equilibration technique.

The N content in the metal sample was measured by the N/O analyzer. The Al and Mn contents in the metal sample were analyzed by the ICP-AES. In order to identify the inclusions in the quenched melt, the metal

sample was cross-sectioned and examined with the SEM-EDS.

3. RESULTS AND DISCUSSION

3.1. N solubility in high Mn-Al alloyed steels

The equilibrium N solubility in Fe-Mn melts containing Mn up to 22 mass% was measured under PN2 of 0.3 atm at 1823~1873K to determine the effect of Mn on the N solubility in liquid iron. Mn significantly increases the N solubility in Fe-Mn-N melts.

The dissolution of N in liquid iron alloys can be written as

NgN =)(21

2 [1]

1 3,598 23.89 J/g atomoG TΔ = + ⋅

2

1 /2

[% ]N

N

f NKP

= [2]

where K1 is the equilibrium constant for reaction [1] and, fN is the activity coefficient of N in the 1 mass% standard state in liquid iron.

Using Wagner’s formalism, K1 can be expressed as the following relation using interaction parameters:

211log log log[% ] log2N NK f N= + − P

2 2[% ] [% ] [% ] [% ]N N Mn MnN N N Ne N r N e Mn r Mn= + + +

2

1log[% ] log2 NN+ − P [3]

where iNe and i

Nr are the first- and second-order interaction parameters of elements on N in liquid iron, respectively. The N

Ne and NNr values are known to be

zero in the present experimental temperature range.

Figure 1 shows the relation of log MnNf vs Mn content

in Fe-Mn-N melts using the relation expressed by Eq. [3]. Therefore, the values of Mn

Ne and MnNr can be

determined as -0.0233 and 0, respectively, by a linear regression analysis of the data in the figure. No temperature dependence on these values was observed in the temperature range from 1823 K to 1873 K.

Page 156: 2-page abstracts booklet

0 5 10 15 20 25-1.0

-0.5

0.0

0.5

1.0

eMnN = -0.0233

1873K, PN2=0.3atm

1823K, PN2=0.3atm

lo

gf M

nN

[%Mn]

Fig.1. Relation of log Mn

Nf vs [Mn] in Fe-Mn-N melts.

3.2. AlN solubility product in high Mn-Al alloyed steels

The reaction equilibrium for the dissolution of pure solid AlN in Fe-Mn-Al-N melts can be written as

( )AlN s Al N= + [4]

303,500 134.6 J/molAlNGΔ = −o T [5]

[% ][% ]Al NAlN Al N

AlN

h hK f f Al Na

= = [6]

where AlNK is the equilibrium constant for Reaction [4], and h and are the Henrian activities of Al and N relative to the 1 mass% standard state in liquid iron, and

Al

Al

Nh

f and Nf are the activity coefficients of Al and N,

respectively.

Figure 2 shows the effect of Mn additions on the solubility of [Al] and [N] for AlN saturation in liquid iron under PN2 of 0.5atm at 1823 K. As the Mn content increases, the N solubility significantly increases while the Al content decreases.

0.00.5

1.01.5

2.0

5

10

15

20

0.000.02

0.040.06

0.080.10

[%N]

AlN saturated

[%M

n]

[%Al]

1823K, PN2=0.5atm

Fig.2. Effect of Mn on [Al] and [N] for AlN saturation.

In order to determine the thermodynamic relation between Mn and Al from the AlN solubility product

data in Fe-Mn-Al-N melts, Eq.[6] can be expressed as the following relation. log log log log[% ][% ]AlN Al NK f f Al N= + +

[% ] [%Al] [%N] [% ]Mn Al N AlN N Al Ale Mn e e e Al= + + +

2[%Mn] [%Mn] log[% ][% ]Mn MnAl Ale r Al+ + + N [7]

Figure 3 shows the values of log MnAlf plotted vs Mn

content in Fe-Mn-Al-N melts using the relation expressed by Eq. [7]. As shown in the figure, the slope of a straight line obtained by the regression analysis of the data is zero. Therefore, the values of

MnAle and Mn

Alr can be determined as zero in high Mn-Al alloyed steel melts in the temperature range from 1823 K to 1873 K.

0 5 10 15 20 25-1.0

-0.5

0.0

0.5

1.0

logf

Mn

Al

[%Mn]

Fe-Mn-Al-N(AlN saturation)[Al]=0.6~1.8%

eMnAl = 0

1848K

1873K PN2 0.8atm PN2 0.5atm PN2 0.5atm PN2 0.5atm PN2 0.3atm PN2 0.2atm

1823K

Fig.3. Relation of log Mn

Alf vs [Mn] in Fe-Mn-Al-N melts.

Therefore, using the interaction parameters determined in the present study, one can calculate the contour lines of critical Al and N contents for the onset of AlN inclusion formation in a Fe-20 mass pct Mn steel melt at different temperatures as shown in Fig. 4. For an example, when the aluminum content is 1.5 mass pct in this alloy, the critical nitrogen content for the AlN formation is 343, 197 and 107 ppm at 1823, 1773 and 1723K, respectively.

0.0 0.5 1.0 1.5 2.0 2.5 3.00.00

0.01

0.02

0.03

0.04

107ppm

197ppm

A 1773K

1823K

1723K

AlN

[%N

]

[%Al]

Fe-20%

Mn-Al-N

No AlN

343ppm

Fig.4. AlN solubility diagram in Fe-20%Mn-Al-N melts.

In order to check the validity of AlN stability diagram for this alloys, the evolution of inclusions observed in the metal samples taken during cooling the melt temperature from 1823 to 1723K.

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4. Conclusions

The thermodynamics of nitride inclusion formation in high Al and high Mn-Al alloyed liquid steel has been investigated. Critical [Al] and [N] contents for AlN formation in Fe-Al (TRIP) and Fe-Mn-Al (TWIP) alloy steel melts has been determined in the temperature range from 1823 to 1973K. Manganese increases the solubility product of AlN in liquid iron because Mn increases the nitrogen solubility significantly. The interaction between Mn and Al in liquid iron is negligible at their high concentration range. For a TWIP steel melt of Fe-20%Mn-1.5%Al composition, AlN can be formed at its melting point of 1723K when [N] content is above 120 ppm. The solute enrichment during solidification can also enhance the driving force for AlN formation in the remaining liquid steel.

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Session 11: Product and quality management

11.1 K44X: a new ferritic stainless steel grade with improved durability for high

temperature automotive applications L. FAIVRE*, P.O. SANTACREU, A. ACHER (Aperam Europe), France

p. 170

11.2 Industrial data mining in steel industry H. PETERS*, A. EBEL (VDEh-Betriebsforschungsinstitut), J. HACKMANN (PSI Metals), T. HECKENTHALER (ThyssenKrupp Nirosta GmbH), N. HOLZKNECHT, N. LINK (VDEh-Betriebsforschungsinstitut), F. LÜCKING (QuinLogic), M. PANDER (SMS Siemag AG), Germany

p. 172

11.3

Finite element modeling of non destructive system for assessment of steel strip properties A. LEBOUC*, Y. GABI, G. MEUNIER (G2Elab - Grenoble Electrical Engineering Laboratory), P. MEILLAND (ArcelorMittal Global R&D), C. GUERIN (Cedrat SA), P. LABIE (G2Elab - Grenoble Electrical Engineering Laboratory), France, B. WOLTER (Fraunhofer Institute for non-destructive testing), Germany

p. 174

11.4

Image processing applied to inclusion detection: results for tinplate application O. DESCHAMPS*, L. DOREL (Siemens VAI Metals Technologies GmbH), France, Z. CANALEJO CATALAN (ArcelorMittal Asturias), Spain, L. SATYANARAYAN, P. PIQUEMAL (ArcelorMittal Global R&D), France

p. 176

11.5

Three-dimensional investigation of inclusion and cluster characteristics on different stages of steel production of various steel grades A. KARASEV*, A. TILLIANDER, P. JÖNSSON (KTH Royal Institute of Technology), Sweden

p. 178

* speaker

Page 159: 2-page abstracts booklet

Session 11: Product and quality management

Table of Contents

11.1 K44X: a new ferritic stainless steel grade with improved durability for hightemperature automotive applications L. FAIVRE, P.O. SANTACREU, A. ACHER (Aperam Europe), France

11.2 Industrial data mining in steel industry H. PETERS, A. EBEL (VDEh-Betriebsforschungsinstitut), J. HACKMANN (PSI Metals), T. HECKENTHALER (ThyssenKrupp Nirosta GmbH), N. HOLZKNECHT, N. LINK (VDEh-Betriebsforschungsinstitut), F. LÜCKING (QuinLogic),M. PANDER (SMS Siemag AG), Germany

11.3

Finite element modeling of non destructive system for assessment of steel stripproperties A. LEBOUC, Y. GABI, G. MEUNIER (G2Elab - Grenoble Electrical Engineering Laboratory), P. MEILLAND (ArcelorMittal Global R&D), C. GUERIN (Cedrat SA), P. LABIE (G2Elab - Grenoble Electrical Engineering Laboratory), France,B. WOLTER (Fraunhofer Institute for non-destructive testing), Germany

11.4

Image processing applied to inclusion detection: results for tinplate application O. DESCHAMPS, L. DOREL (Siemens VAI Metals Technologies GmbH), France,Z. CANALEJO CATALAN (ArcelorMittal Asturias), Spain, L. SATYANARAYAN, P. PIQUEMAL (ArcelorMittal Global R&D), France

11.5

Three-dimensional investigation of inclusion and cluster characteristics on different stages of steel production of various steel grades A. KARASEV, A. TILLIANDER, P. JÖNSSON (KTH Royal Institute of Technology), Sweden

Page 160: 2-page abstracts booklet

K44X: a new ferritic stainless steel grade with improved durability for

high temperature automotive applications“

L.Faivre, P.O. Santacreu, A. Acher

(Aperam Isbergues)

Introduction

Over the past few years car manufacturers have been considering ever higher service temperatures for the engine in order to comply with more and more constraining depollution standards. Consequently, the hot part of the exhaust system - from manifold to the catalytic converter - could be subjected to temperatures up to 1000°C, which is beyond the maximal service temperature of most stainless steel grades used nowadays in this application. Moreover, an improved durability is also required for such parts. In this context, a new ferritic stainless steel grade has been developed, named K44X, to fulfil these new specifications. It belongs to EN 1.4521 classification and could be applied on both fabricated/tubular manifolds and turbocharger shells. K44X, with a chromium content of 19% (weight) and additions of molybdenum (2%) and niobium (0.6%), offers a low thermal expansion coefficient and excellent high temperature properties like cyclic oxidation, creep and thermal fatigue resistance. Furthermore, its molybdenum content also guarantees an improved corrosion resistance that makes this grade an optimized solution for turbocharger application. The paper will presents the main high temperature properties of K44X in comparison with austenitic refractory (e.g. 309-1.4828 or S30815-1.4835) and ferritic (e.g. 441-1.4509) stainless steel grades common for this application together with the manufacturing capabilities of this new ferritic grade.

Materials & procedure

The chemical composition of K44X and most common grades used in hot end exhaust applications is given in the table 1. 1.4828 grade is the only austenitic grade due to its significant nickel content, the others being ferritic. The stabilizing elements (Ti, Nb) added to improve the intergranular corrosion resistance are also mentioned in this table since they are affecting high temperature properties such as creep resistance or tensile properties.

Grade C Cr Mo Ni Misc. Fe

1.4512 0.01 11.5 - - Ti=0,2 Bal.

1.4510 0,02 16,5 - - Ti=0,4 Bal.

1.4509 0,02 17,8 - - Ti+Nb=0,6 Bal.

K44X (1.4521) 0,02 19 1,9 - Nb=0,6 Bal.

1.4828 0,05 19,3 - 11,4 - Bal.Table 1: Chemical composition of K44X and other common

stainless grades used in exhaust applications (mass %)

Many high temperature characterizations have been carried out in this study to assess different properties separately:

- tensile test on an INSTRON 5582 equipped with a resistance furnace)

- high cycle fatigue (tension-compression, 2.106

cycles, R=-1, frequency : [10-20Hz])

- creep sag-test (self supported bending creep of initially flat samples)

- cyclic oxidation in air (automatic introduction & extraction in a furnace combined to an air-pulsed cooling)

However a more complex test in which thermal fatigue, oxidation and creep phenomena may interact has also been used. In this test, a V-shaped specimen was heated by Joule effect while being blocked at both ends to constrain thermal expansion (see fig. 1). This bench was designed to simulate on a simple laboratory device the thermo-mechanical loading that a manifold undergoes in service.

Fig. 1 : Thermal fatigue bench test

Results and discussion

Although ferritic stainless steels present lower mechanical properties than austenitic grades at high temperatures, K44X shows approximately 30% higher yield strength than 1.4509 between 750 and 1000°C (see fig. 2) thanks to its addition of molybdenum and niobium which are known to be effective solid solution alloying elements [1]. Since the endurance limit is strongly related to the proof and ultimate strengths of the material, the ranking with regards to high cycle fatigue was shown to be identical than for the tensile properties at the tested temperatures: 300, 600, 750 and 850°C (cf [2] for more details).

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0

20

40

60

80

00

120

140

160

180

700 800 900 1000

T emperature [°C ]

14828K44X-14521145091451014512

Fig. 2 : 0.2% proof strength in the range 750-1000°C

The creep resistance of K44X was significantly better than the other tested ferritic or austenitic grades, whatever the temperature was. This can be explained by the pure Nb-stabilization of K44X - unlike most 1.4521 grades - that induces a fine intermetallic Fe-Nb precipitation along the grain boundaries. These precipitates have probably a pining effect that hinders grain boundary sliding.

0

10

20

30

40

4091.4512

430Ti1.4510

4411.4509

K44X 3091.4828

3041.4301

Cre

ep def

lectio

n af

ter 1

00h [m

m] 850°C

950°C1000°C

Fig. 3 : Creep deflection (bending) after a 100h exposition

0

50

100

150

200

0 100 200 300 400 500 600

Time [h]

Mas

s ga

in [g

/m2]

1.4828K44X-1.45211.4509

Fig. 4 : Cyclic oxidation in air up to 1000°C

The difference between austenitic and ferritic grades is particularly pronounced when it comes to cyclic oxidation resistance. Therefore, one of the main parameters controlling this phenomenon is the coefficient of thermal expansion (CTE) and more specifically the difference between the metal and the oxide coefficients. Since austenitic grades have a higher CTE, the difference to the oxide thermal expansion is more pronounced and they are therefore much more sensitive to spalling at high temperatures. Besides, K44X present at least 20% less mass gain

than 1.4509 at 950°C and 1000°C (fig.4) thanks to a higher Cr content.

Finally K44X also evidenced the highest thermal fatigue resistance among the tested materials for the tested configurations (thermal cycle & sheet thickness). The test results presented previously (tensile, HCF, creep, cyclic oxidation) is useful to understand the thermal fatigue ranking since most of these properties are involved in this test. However in the case of the austenitic grade, the better mechanical properties were not sufficient to counterbalance the higher thermal stresses and the lower cyclic oxidation resistance of this grade. Within the ferritic family, K44X exhibits 10 to 40% longer lifetime than 1.4509 when no holding time was applied in the thermal cycle and even more when holding time was applied (180s at the upper temperature) as shown in fig.5.

0

2000

4000

6000

8000

10000

250-850°C2mm- hick

100-950°C1,5mm-thick

100-1000°C1,5mm- hick

Life

time

(cyc

les)

K44XK44X-180s1450914509-180s

1482814828-180s1451214512-180s

Fig. 5 : Thermal fatigue resistance for different

configurations

Conclusion

Ferritic stainless steels are not only cost effective solutions for hot exhaust applications but they also exhibit lower thermal expansion than austenitic grades. Consequently 1.4509 grade is now being widely used on manifold application up to 950°C. However, since the exhaust temperature is expected to increase beyond 950°C in the future, K44X can be an effective material solution for service temperatures up to 1000°C. It also offers longer lifetime than 1.4509 at lower temperature thanks to its better yield/tensile strengths and to improved oxidation, creep and thermal fatigue resistance. Since stainless steel manifolds are mostly fabricated solutions, forming and welding abilities are also of great interest. K44X actually presents a very good MIG/Laser weldability and a formability close to EN 1.4509. This grade could also allow thinner designs and therefore weight saving thanks to its higher thermo-mechanical fatigue resistance compared to existing solutions.

References

[1] N. Fujita et al, Scripta Materialia, Vol. 35, No. 6, 1996, pp. 705-710

[2] P.O. Santacreu, S. Saedlou, L. Faivre, A. Acher, J. Leseux, SAE Technical Paper 2011- 01-0194, 2011

Page 162: 2-page abstracts booklet

Industrial Data Mining

in Steel Industry

H.Peters, A.Ebel, N.Holzknecht, N.Link (VDEh-Betriebsforschungsinstitut GmbH)

T.Heckenthaler (ThyssenKrupp Nirosta GmbH) J.Hackmann (PSI Metals GmbH) F.Luecking (QuinLogic GmbH)

M.Pander (SMS Siemag AG)

1. MOTIVATION The continuous improvement of all steel production processes regarding the avoidance of quality deficiencies and the related improvement of production yield is an essential task of each steel producer. Therefore and inside the today popular Zero-Defect strategy several quality assurance techniques are used. The present report explains in this environment the method of Data Mining (DM) and describes its application in the industrial environment and here especially in steel industry. Beside a description of the general procedure different approaches for the realisation of the necessary software tools are discussed. 2. TECHNOLOGY OF INDUSTRIAL DATA MINING If the causes of quality defects are not directly obvious and no experience regarding possible cause&effect relationships exist, the deeper investigation of stored process variables on the hand and measured quality features on the other hand can be a tool to solve the problem. Since some years the technology of Data Mining has been applied for that purpose. DM is part of a larger process which is called “Knowledge Discovery in Databases” and combines a special order of several processing steps with different types of statistical / computational / machine learning methods to find cause&effect relationships inside a huge amount of data. Figure 1 describes the general procedure of DM. If DM is applied in an industrial environment all steps of data pre-processing are extremely important. The presentation will explain here two examples out of the large number of necessary pre-processing steps.

Figure 1: General procedure of Data Mining

In the described work the focus of DM was put to the detection of cause&effect relationships regarding quality deficiencies. The basic idea therefore is the comparison of data sets which describe defect free products and data sets which describe products with defects. The first step which is necessary therefore is the construction of a suitable data table. Figure 2 shows the necessary processing steps.

Figure 2: Construction of data table

The last point here, which is described as “aggregation and feature extraction” has always to be adapted to the special task of investigation. If e.g. the relation between surface defects on hot rolled flat strips on the one hand and the production condition in the melt shop and at continuous casting on the other hand has to be investigated, the process variables and the aggregation methods shown in Figure 3 have to be applied.

Figure 3: Aggregation of different types of data

Therefore a correct material tracking (or material genealogy) is necessary and the processing of all length related data has to be done in a suitable way. Another example is the handling of the constructed data sample. Here many preconditions have to be fulfilled to guarantee proper results from a statistical point of view. Figure 4 illustrates two problems which are relevant here: • the used data sample has to be “balanced”

regarding the number of data sets which describe defect free and defected products,

Page 163: 2-page abstracts booklet

• data sets from different steel types or out of different time ranges of production have to be distributed in the same way to training, test and validation data sets.

Figure 4: Pre-processing of data samples

Furthermore the plausibility of data and the existence of outliers have to be checked. Only after a careful performing of all these pre-processing steps the application of techniques to detect the cause&effect relationship makes sense. Therefore methods out of the groups of statistics, computational intelligence or machine learning can be applied. Which technique finally is used depends on many circumstances: the number of available data sets, the number of input variables, the complexity of the problem, etc.. 3. APPLICATION AREAS In the following short list some examples of quality features are listed for which cause&effect analysis have been done by using Data Mining technologies: • hot iron temperature at tapping of blast furnace, • surface defects on strip based on oxide inclusions

in the melt, • longitudinal cracks on rods, • surface defects on the inner part of pipes, • deviations of technological parameters like yield

and tensile strength, • deviations of layer thickness at colour coating.

It has to be mentioned that not all DM investigations regarding the detection of cause&effects between process behaviour and quality feature are successful. Sometimes the relevant information isn’t existing inside the available process variables and sometimes not enough data sets could be collected to perform a successful DM. 4. SOFTWARE SOLUTIONS As it easily can be understood software tools play an important role to speed up the DM process as much as possible. The task is here to develop tools which are completely integrated in the IT environment of the steel company and which makes the application of DM for cause&effect analysis as easy as possible. The aim has to be that many people in a company can

run DM investigations and not only one or two specialist. Together with several partners the VDEh-Betriebsforschungsinstitut has developed four different solutions for the above described application of DM in the last years: • Universal DM tool specialised for the use by

process and quality engineers (in cooperation with QuinLogic),

• Wizard-like DM tool integrated in a quality analysis environment (in cooperation with SMS-Siemag),

• Easy-to-use DM tool integrated in company information cockpit (in cooperation with ThyssenKrupp Nirosta),

• Scenario based DM tool including complete and universal material genealogy (in cooperation with PSI Metals).

Up to now not enough experience with the application of the different solutions exist to really compare their efficiencies. What can be said at the moment is that all of them are simpler to use than “standard” DM tools and are really adapted to the typical processing steps of industrial DM and cause&effect analysis regarding quality deficiencies in steel industry. 5. FUTURE DEVELOPMENTS DM is a technology to detect cause&effect relation-ships in form of statistical “correlations”. That has to be differentiated from “causality”. To handle this “causality” methods exist to store knowledge in form of “semantic networks”, which are able to describe causal relationships. A future research topic could e.g. be to combine both approaches in such a way, that a weakness of the one technology will be compensated by strength of the other (Figure 5).

Figure 5: Combination of knowledge management and

DM Finally the plant personal should get the best possible support to detect causes of quality deficiencies as fast as possible.

Page 164: 2-page abstracts booklet

Finite element modelling of non

destructive system for assessment of steel strip properties

A. LEBOUC*, Y. GABI, G. MEUNIER (G2Elab - Grenoble Electrical Engineering Laboratory),

P. MEILLAND (ArcelorMittal Global R&D), C. GUERIN (Cedrat SA), P. LABIE (G2Elab -

Grenoble Electrical Engineering Laboratory), France

B. WOLTER (Fraunhofer Institute for non-destructive testing), Germany

The 3MA (Multi-parameter Micromagnetic Microstructure Analyzer) system, has shown its potential for on-line assessment of steel strips mechanical properties, but its outputs relation (in particular the incremental permeability mode) to the magnetic behavior was not up to now well understood, and heuristics remain the only option to determine end-user properties. A finite element approach using a commercial electromagnetic simulation code with the unique integration of the hysteretic magnetic behavior manages to bridge this gap. Knowing the magnetic behavior of the different steel layers allows to compute the values of the magnetic induction and its derivative to the magnetic excitation field in each point of a hysteresis cycle. Then a standard eddy-current routine allows to derive the pick-up voltage. The application of this model yields satisfactory results, with convincing sentivity analyses for the effect of probe to sample distance, and the materials hardness. Thus the 3MA appears now with a much better understanding of its output signals, therefore providing good confidence in its ability to monitor the consistency of steel strips microstructural features.

Page 165: 2-page abstracts booklet

Image processing applied to inclusion detection: results for

tinplate application

O. Deschamps (Siemens VAI MT SAS, France)

L. Dorel (Siemens VAI MT SAS, France)

Z. Canalejo Catalan (ArcelorMittal Aviles, Spain)

L. Satyanarayan (ArcelorMittal Research, France)

P. Piquemal (ArcelorMittal Research, France)

INTRODUCTION

The quality standards in the sectors of the packaging becoming increasingly strict, it had become necessary to guarantee for the steel producers the inclusion cleanliness of rolled metal.

The ArcelorMittal group thus decided to develop equipment making it possible to control on line the internal quality of thin sheets: control by Lamb waves.

After validation by ArcelorMittal Research, the responsibility for industrialization was entrusted to the Siemens VAI Metals Technologies and Spie companies.

SYSTEM CHARACTERISTICS

In order to benefit from the results as early as possible in the production route, the system is designed to be placed on the pickling line.

The system is composed of 3 parts:

- on line sensors (lamb wave)

- acquisition hardware, based on SIAS technology

- server for archiving , database

The challenge of the installation at the pickling line had to be considered taking into account:

- the environment

- the line speed up to 600m/min

- 100% coil length inspection

- thickness up to 6mm

The sensor is composed of an ultra sonic transducer which sends/receives echos through the strip. One wheel inspects half of the strip, so 2 wheels are necessary for a complete strip inspection. An overlap

between the 2 wheels ensures that 100% of the strip width is covered.

Lamb wave sensor with 2 wheels

RESULTS

The installation at ArcelorMittal Aviles was tuned in order to monitor 2 types of inclusions:

- “small inclusion”

- “big inclusion”

The criteria to differentiate both in based on geometrical data.

A third class has been introduced, which corresponds to false echo (ie noise from the sensor), but which is well differentiated from real inclusions after classification stage.

Some deep validation has been done , with correlation between lamb wave inspection, and inclusions seen on the downstream process (eg galvanizing line) using classical camera based inspection. Not all inclusions are visible on the downstream process, but where high number of inclusions where detected in the pickling line, corresponds to local detections of inclusions on the galvanizing line.

The system allows to detect and alert on products with inclusions. With an early product re-routing (repair/downgrade), coils are not sent anymore to rolling and tinning lines. As a next stage, caster optimization will be done, by correlations between inclusions and casting parameters.

Also, coupling between lamb-waves and surface (camera based) inspection can be a next evolution.

Page 166: 2-page abstracts booklet

The electrolytic extraction method in combination with SEM can be successfully applied as a reference method for 3-D investigations of inclusions and cluster in steel samples taken on different steelmaking stages of various industrial steel grades. Moreover, the accuracy of the EE+SEM method is higher than that of the CS+SEM method by investigation of small size inclusions (<1 micron), inclusions elongated during deformation (such as MnS) and clusters.

(Ti,Mn,Si,Mg)O

(Ce,Ti)Ox and

TiN Al2O3 cluster

(Al,Mg)O +

(Ti,Nb)C +MnS

MnS in “as cast” steel

MnS in rolled

steel

REFERENCES:

1. A.V. Karasev, H. Suito. Analysis of Size Distributions of Primary Oxide Inclusions in Fe-10 mass pct Ni-M (M = Si, Ti, Al, Zr, and Ce) Alloy. Metall. Mater. Trans. B, 1999, 30B, p259-270. Fig. 1 Typical inclu usters on surface of

able 1. 3D investigation of non-metallic inclusions

Investigated Inclusions Ref*

sions and clfilm filter after electrolytic extraction. 2. Y. Kanbe, A. Karasev, H. Todoroki, P.G.

Jönsson. Application of Extreme Value Analysis for Two- and Three-Dimensional Determinations of the Largest Inclusion in Metal Samples. ISIJ Int., 2011, 51 (4), p593-602.

Tand clusters in different industrial steels and alloys by using EE+SEM method

Steels and Samples 3. Y. Kanbe, A. Karasev, H. Todoroki, P.G. Jönsson. Analysis of Largest Sulfide Inclusions in Low Carbon Steel by Using Statistics of Extreme Values. Steel Res. Int., 2011, 82 (4), p313-322.

alloys and clusters Low w liquid steel, Oxid

MI/

ulfides/PSD 2-500µm

up

3,up

carbon loalloyed steels (0.01-0.2%C,

< 1.5%Cr)

ingot, rolled steel and

final product

es, sulfides, nitrides, complex NPSD 0.05-20 µm S

4. O.T. Ericsson, M. Lionet, A.V. Karasev, R. Inoue, P.G. Jönsson. Changes in inclusion characteristics during sampling of liquid steel. Ironmaking and Steelmaking, 2012, accepted for publication.

316L stainless liquid steel 4, steel (0.02%C, 17%Cr, 10%Ni)

Oxides, sulfides, complex NMI / PSD 0.05-6 µm

up

253MA stainless steel

liquid steel, NMI/ up

(0.08-0.1%C, 19-21%Cr, 9-11%Ni)

nozzle zone Oxides, complexPSD 3-25 µm

5. Y. Bi, E. Roos, A. Karasev, P.G. Jönsson. Three-Dimensional Evaluation of Inclusions during the Production of Stainless Steel. Proc. 9th Inter. Conf. on Molten Slags, Fluxes and Salts (MOLTEN12), Beijing, China, 2012, 27-30 May.

High silicon stainless steel

liquid steel Oxides, sulfides, 5

(0.2-0.5%C, 19-24%Cr, 11-20%Ni)

complex NMI/ PSD 1-25 µm

6. H. Doostmohammadi, A. Karasev, P.G. Jönsson. A Comparison of a Two-Dimensional and a Three-Dimensional Method for Inclusion Determinations in Tool Steel. Steel Res. Int., 2010, 81 (5), p398-406.

Tool steel AISI liquid steel, Oxides, sulfides, 6, H13(0.3-0.4%C, 4-6%Cr, 1-2%

Mo)

ingot complex NMI/ PSD 2-30 µm

up

High carbon Oxides, sulfides, up steel (0.8-0.9%C)

complex NMI/ PSD 3-40 µm

Fe-alloys

(final alloy x, up

FeTi, FeCr, FeNb)

SiO2, Al2O3, TiOmetallic phases/ PSD 1-50 µm

*: up - unpublished results

ONCLUSIONS:

experience of researchers from the Divis

C

The scientific ion of Applied Process Metallurgy in KTH

obtained during the recent 4 years by application of electrolytic extraction technique for investigation of inclusions and clusters in lab and industrial steel samples, can be summarized as follows:

Page 167: 2-page abstracts booklet

Three-dimensional investigation of inclusion and cluster

characteristics on different stages of steel production of various steel

grades

Andrey KARASEV, Anders TILLIANDER and Pär G. JÖNSSON  

(KTH Royal Institute of Technology, Sweden)  

ABSTRACT:

It is well known that the properties of the final steel product (such as microstructure, mechanical properties and etc.) are significantly influenced by the non-metallic inclusion and cluster contents in steel. Therefore, an accurate quantitative analysis of inclusion and cluster characteristics (such as size, number, composition and morphology) in metal samples from different stages of steel production is very important. The well-known two-dimensional (2-D) investigation of inclusions on a polished cross section of a metal sample (CS+SEM method) has some serious disadvantages with respect to determination of inclusions (such as irregular or elongated after deformation) and clusters. This is due to the fact that the sizes of inclusion or cluster sections measured in 2D on a metal surface often do not agree with real sizes of those in a metal volume.

In this case, a three-dimensional (3-D) investigation of inclusions and clusters on a film filter after electrolytic extraction of steel samples (EE+SEM method) could serve as a reference method for more accurate determinations of inclusion and cluster characteristics in steel. In the present study, the advantages and limitation of EE+SEM method was compared to data from CS+SEM and other methods by investigation of inclusions and clusters in industrial metal samples from various steel grades from different stages of steelmaking.

INTRODUCTION:

Recently, the chemical and electrolytic extraction (EE) technique applied widely for three-dimensional (3-D) investigations of non-metallic inclusions (NMI) in steel samples along with conventional methods for two-dimensional (2-D) observations of inclusions on polished cross section of steel samples (CS+SEM method). From our point of view, the EE in combination with SEM investigation (EE+SEM method) is one of the promising techniques for evaluation of inclusions in steels. This is confirmed by the sharply increased interest of researchers and steel production companies in Japan, South Korea, Sweden and some other countries to EE method and

increased number of publications in which the EE technique is widely used for investigation of inclusion characteristics. Moreover, several authors1-3) noted that the 3-D investigation of non-metallic inclusions after electrolytic extraction is more accurate in comparison to the conventional 2-D CS+SEM method, particularly by investigation of clusters and small size inclusions.

ELECTROLYTIC EXTRACTION:

For three-dimensional (3-D) investigations of non-metallic inclusions and clusters in different steel grades, specimens (15×10×4 mm) were cut from steel samples taken at different stages of steel production.

During electrolytic extraction by using 10% AA or 2% TEA electrolytes, a conductive metal matrix is dissolved while the non-conductive inclusions are not dissolved in the electrolyte. Then, the undissolved non-metallic inclusions can be collected by filtration of the solution on a surface of membrane polycarbonate film filters with open pore sizes of 0.05-3 µm. The characteristics of inclusions and clusters (such as morphology, size, number and composition) can be investigated in 3-D and analysed on a film filter by using a SEM. The volume of the dissolved metal during the electrolytic extraction was varied from 6 to 51 mm3. In this case, the depth of a dissolved metal layer on surface of metal specimens could be varied from 0.05-0.50 mm depending on the purposes of electrolytic extraction and steel grade. 300-5000 inclusions were analysed for determination of the particle size distribution in steel specimens. The size range of investigated inclusions varied from 0.05 to 500 microns.

RESULTS:

In the frame of this study, the EE+SEM method was used as an accurate reference method for determination of various inclusions (oxides, sulfides, nitrides and complex NMI) and clusters in steel samples taken by production of different steel grades. The typical inclusions and cluster in different steel samples observed by using EE+SEM method are shown in Figure 1.

One of the main limits of electrolytic extraction technique is a precipitation of some compounds during dissolution of steel samples with C > 0.2% (carbides) and high alloyed steels (Cr-compounds or metallic phases). In this case, the investigation of inclusions (particularly, small size inclusions, <2 microns) is significantly difficult because the NMI are covered by these precipitates. However, the large size inclusions (>3-5 µm) can be analysed. Some examples of successful 3-D investigations of inclusions and clusters in different steel grades after electrolytic extraction are given in Table 1.

Page 168: 2-page abstracts booklet

The electrolytic extraction method in combination with SEM can be successfully applied as a reference method for 3-D investigations of inclusions and cluster in steel samples taken on different steelmaking stages of various industrial steel grades. Moreover, the accuracy of the EE+SEM method is higher than that of the CS+SEM method by investigation of small size inclusions (<1 micron), inclusions elongated during deformation (such as MnS) and clusters.

(Ti,Mn,Si,Mg)O

(Ce,Ti)Ox and

TiN Al2O3 cluster

(Al,Mg)O +

(Ti,Nb)C +MnS

MnS in “as cast” steel

MnS in rolled

steel

REFERENCES:

1. A.V. Karasev, H. Suito. Analysis of Size Distributions of Primary Oxide Inclusions in Fe-10 mass pct Ni-M (M = Si, Ti, Al, Zr, and Ce) Alloy. Metall. Mater. Trans. B, 1999, 30B, p259-270. Fig. 1 Typical inclusions and clusters on surface of

film filter after electrolytic extraction. 2. Y. Kanbe, A. Karasev, H. Todoroki, P.G. Jönsson. Application of Extreme Value Analysis for Two- and Three-Dimensional Determinations of the Largest Inclusion in Metal Samples. ISIJ Int., 2011, 51 (4), p593-602.

Table 1. 3D investigation of non-metallic inclusions and clusters in different industrial steels and alloys by using EE+SEM method

3. Y. Kanbe, A. Karasev, H. Todoroki, P.G. Jönsson. Analysis of Largest Sulfide Inclusions in Low Carbon Steel by Using Statistics of Extreme Values. Steel Res. Int., 2011, 82 (4), p313-322.

Steels and alloys

Samples Investigated Inclusions and clusters

Ref*

Low carbon low alloyed steels (0.01-0.2%C,

< 1.5%Cr)

liquid steel, ingot, rolled steel and

final product

Oxides, sulfides, nitrides, complex NMI/ PSD 0.05-20 µm Sulfides/PSD 2-500µm

up

3,up

316L stainless steel (0.02%C, 17%Cr, 10%Ni)

liquid steel Oxides, sulfides, complex NMI / PSD 0.05-6 µm

4, up

253MA stainless steel (0.08-0.1%C, 19-21%Cr, 9-11%Ni)

liquid steel, nozzle zone

Oxides, complex NMI/ PSD 3-25 µm

up

High silicon stainless steel (0.2-0.5%C, 19-24%Cr, 11-20%Ni)

liquid steel Oxides, sulfides, complex NMI/ PSD 1-25 µm

5

Tool steel AISI H13(0.3-0.4%C, 4-6%Cr, 1-2%

Mo)

liquid steel, ingot

Oxides, sulfides, complex NMI/ PSD 2-30 µm

6, up

High carbon steel (0.8-0.9%C)

Oxides, sulfides, complex NMI/ PSD 3-40 µm

up

Fe-alloys (FeTi, FeCr,

FeNb)

final alloy SiO2, Al2O3, TiOx, metallic phases/ PSD 1-50 µm

up

4. O.T. Ericsson, M. Lionet, A.V. Karasev, R. Inoue, P.G. Jönsson. Changes in inclusion characteristics during sampling of liquid steel. Ironmaking and Steelmaking, 2012, accepted for publication.

5. Y. Bi, E. Roos, A. Karasev, P.G. Jönsson. Three-Dimensional Evaluation of Inclusions during the Production of Stainless Steel. Proc. 9th Inter. Conf. on Molten Slags, Fluxes and Salts (MOLTEN12), Beijing, China, 2012, 27-30 May.

6. H. Doostmohammadi, A. Karasev, P.G. Jönsson. A Comparison of a Two-Dimensional and a Three-Dimensional Method for Inclusion Determinations in Tool Steel. Steel Res. Int., 2010, 81 (5), p398-406.

*: up - unpublished results

CONCLUSIONS:

The scientific experience of researchers from the Division of Applied Process Metallurgy in KTH obtained during the recent 4 years by application of electrolytic extraction technique for investigation of inclusions and clusters in lab and industrial steel samples, can be summarized as follows:

Page 169: 2-page abstracts booklet

Session 12: Pickling and cold rolling

Table of Contents

12.1 Eco Pickled Surface (EPS) - An Environmentally Preferred Alternative to Acid Pickling of Flat Rolled Steel: Production Experience and Economic Performance R. THOMAS, K. VOGES (The Material Works, Ltd), W. PERRY (Mercury Business Development Services Corporation), USA

12.2 Steel pickling, acid regeneration and plastic corrosion in steel rolling mills F. RÖGENER (VDEh-Betriebsforschungsinstitut), Germany, K. JACOBSON, P. BERGSJÖ (Swerea KIMAB), Sweden, G. HARTMANN (ThyssenKrupp Nirosta GmbH), M. SARTOR, T. REICHARDT (VDEh-Betriebsforschungs-institut), Germany

12.3

New Siemens VAI pickling model helps to improve surface purity - FAPLAC® APM K. KOFLER, S. WALTER, P. BARBIERI (Siemens VAI Metals Technologies GmbH), Austria

12.4

Pickling line / tandem cold mill with electrical and automation systems from SMSSiemag successfully commissioned at MMK D. EHLERT, M. BÜHREN (SMS Siemag AG), Germany, S.N. USHAKOV (Magnitogorsk Iron & Steel Works), Russia

12.5

Asolid laser welder H. THOMASSON (Siemens VAI Metals Technologies), France

12.6

Benefits of chrome plating and long-term viability of use in the rolling industry G. PENZES (Nord Chrome), France

Page 170: 2-page abstracts booklet

Eco Pickled Surface (EPS): An Environmentally Preferred Alternative To Acid Pickling Of

Flat Rolled Steel

Kevin Voges, The Material Works, Ltd.

Rick Thomas, The Material Works, Ltd.

INTRODUCTION Acid pickling is the primary method for removing mill scale – the oxide layer formed as steel strip cools from hot rolling. As acid pickling evolved from a batch to a continuous process, and from use of sulfuric acid to hydrochloric acid, its economics have improved. However, despite the ability to ‘regenerate’ the acid, issues with this hazardous substance – worker safety, storage and transport, disposal, special permitting and reporting – make acid pickling an environmental and safety liability. Alternatives have been researched, from chemical reduction processes to continuous dry shot blasting, but none proved economically attractive or capable of matching acid pickling’s consistency.

In 2005, The Material Works, Ltd. (TMW) of Red Bud, Illinois USA began research and development of an environmentally ‘friendly’ alternative to acid pickling, based on Slurry Blasting technology. TMW refined Slurry Blasting, developing equipment and processes to apply it in a continuous manner to strip steel, while achieving consistency of surface finish. TMW named the process Eco Pickled Surface, EPS for short, and has been awarded five patents on this technology.

TMW built a commercial-scale EPS production line in 2009. It was a ‘working laboratory’ for advancements in component design and process control. The line also produced samples of EPS-processed strip steel which were evaluated for their metallurgical properties and compatibility with steel enhancement processes (cold rolling, galvanizing, annealing, etc.), as well as fabricating and finishing operations. This first EPS line also established production economics that indicated a cost advantage over acid pickling.

Today, EPS is considered a complete replacement for acid pickling and is fully commercialized. Lines of various capacity operate in North America and Asia.

SLURRY BLASTING TECHNOLOGY In Slurry Blasting, fine-particle steel abrasive (grit) is mixed with water to produce a ‘slurry’. The mixture is pumped into a rotating impeller which hurls it against the surface of the steel strip, dislodging particles of scale. The components and function of EPS ‘Slurry Turbines’ are shown in Figure 1.

Figure 1: EPS Slurry Turbines Blast Hot Rolled Strip The slurry is propelled onto the strip in a uniform stream that removes scale, but not substrate. Grit is automatically captured and re-used. Water is filtered continuously, rinsing both the grit and the steel strip. This makes Slurry Blasting a very clean process and the ease/efficiency of pumping, collecting and filtering grit and water makes an EPS system very compact.

CHARACTERISTICS OF EPS-PROCESSED STEEL To replace acid pickling, Slurry Blasting must produce steel that’s interchangeable with acid pickled material. The EPS process does not alter steel chemistry or appreciably harden the surface, so EPS-processed steel is metallurgically identical to acid pickled steel.

EPS-processed steel differs from acid pickled steel in surface texture and appearance. Acid pickling doesn’t affect the strip’s surface texture; it retains the texture from the hot rolling process. By contrast, the EPS process creates an optimized ‘engineered’ surface:

1. It has a lustrous, stainless steel appearance that is very uniform across the strip.

2. Many mill defects such as pitting, roll marks and silicon streaks are markedly reduced by EPS processing. ‘Pickling stain’ – a surface blemish introduced by acid pickling – is removed by EPS.

3. This more uniform texture results in an overall smoother painted finish for EPS processed strip. In testing, different samples of acid pickled strip and EPS-processed strip were chromated, then e-coat painted in an identical manner. At each stage (bare steel, chromated and painted) the average roughness, (Ra) and surface ‘waviness’, (Wa), of the samples were measured by optical profilometry. The results, shown in Figure 2, show that the e-coated EPS-processed strip has a markedly lower Wa value, which is indicative of the smoother, more uniform paint finish that the surface trace clearly depicts.

Page 171: 2-page abstracts booklet

Figure 2: Surface Traces After Chromate and E-Coat A remarkable benefit of EPS-processed steel is it resists rusting in its ‘dry’ state, with no protective oil film or coating. So long as dry EPS-processed steel is stored in an enclosed, non-condensing environment where it does not come into contact with moisture, no observable rust will develop over prolonged periods.

Two factors account for this resistance to rusting:

1. In acid pickling, the acid’s reaction with surface oxides leaves residual chloride salts on the steel surface. These salts react with any moisture, promoting rusting and resulting in early, and often catastrophic, paint failures. EPS leaves no such chloride salts on the steel surface.

2. EPS slurry solution uses an additive to reduce "smut" on the strip. This additive contains a rust inhibitor, a trace amount of which remains on the surface after rinsing. It has no impact on paint performance, but enhances rust resistance.

With no rust-preventative film of oil, EPS-processed steel offers cost savings and process improvements relative to hot rolled pickled and oiled (HRPO) steel:

• No need to clean off oil when using EPS steel; • Paint pre-treatment systems designed for HRPO

can be ‘leaned down’ when using EPS; • Laser/plasma cutting run faster, with less smoke; • Welding EPS steel reduces potentially hazardous

welding fumes relative to HRPO. The significant experience accumulated in processing, fabricating and finishing EPS processed steel has demonstrated that it is functionally interchangeable with HRPO, acid pickled dry and hot roll black, but offers significant advantages and opportunities for cost savings relative to those other categories of steel.

EPS CONFIGURATIONS AND ECONOMICS The first commercial-scale EPS production line led to enhancements and standardization of the design into the EPS ‘Cell’. An EPS Cell uses 8 Slurry Turbines –

4 for descaling the top surface and 4 for the bottom. It is a self-contained system, incorporating slurry supply, water filtering and recirculation functions. The pickling capacity of a single EPS Cell is approximately 18,000 tons per month. Figure 3 shows a single EPS Cell.

Figure 3: EPS Production Line With One EPS Cell

This modular design of the EPS Cell offers flexibility in configuring EPS production lines:

1. EPS Cells placed in series increase production speed and line output in proportion to the number of cells. Scale removal is a function of exposure to the Slurry Blast stream, so more blast streams (more cells) means greater exposure. EPS lines using 3 and 4 cells are being built and started up.

2. Cells can replace acid or rinse tanks in aging acid pickle lines. This is attractive for pickling lines where maintenance or economics are becoming unattractive but the line’s terminal equipment has plenty of remaining service life. An EPS Cell fits easily inside the footprint of a typical acid tank.

3. EPS Cells added to an existing acid pickling line. This involves placing the EPS Cell(s) before the acid pickling tanks to perform a first pass removal of scale. This lessens the duty on the acid tanks and increases speed/output of the pickling line.

EPS production economics are attractive compared to acid pickling. Analysis of EPS processing versus acid pickling of comparable capacity shows that, as a general rule:

• EPS capital cost is 20% less than acid pickling;

• EPS operation (variable) cost is 30% less;

• EPS floor space needs half that of acid pickling.

EPS COMMERCIALIZATION STATUS The first production line using the new EPS Cell began operation in 2011. By 2Q 2013, seven EPS production lines utilizing a total of 14 EPS Cells are expected to be in operation, including lines using three and four cells each. These lines will be in North America and Asia, but interest in EPS technology is strong in all steel processing markets of the world.

Page 172: 2-page abstracts booklet

Steel pickling, acid regeneration and plastic corrosion in steel

rolling mills

F. Rögener (VDEh-Betriebsforschungsinstitut Düsseldorf)

K. Jacobson (Swerea KIMAB Kista)

P. Bergsjö (Swerea KIMAB Kista)

G. Hartmann (ThyssenKrupp Nirosta Krefeld)

M. Sartor (VDEh-Betriebsforschungsinstitut Düsseldorf)

T. Reichardt (VDEh-Betriebsforschungsinstitut Düsseldorf)

BACKGROUND:

Pickling is the chemical removal of oxide layers (scale) and other impurities from steel surfaces prior to subsequent production processes. The acids applied for pickling - mainly hydrochloric acid, sulfuric acid and mixtures of hydrofluoric acid and nitric acid - are highly corrosive. Thus, all components of the pickling line - such as tanks, pipes, valves and regeneration systems - are affected. If material deterioration occurs, acid can be released and may lead to accidents. Non-metallics are preferred choice of material to be used in the process equipment of pickling plants to cope with the aggressive environment of the pickling process. Due to the highly corrosive environments, corrosion also occurs on the plastics equipment. However, relevant corrosion resistance data for plastics are often lacking. This makes it difficult to compare different materials on a price/performance basis and it can sometimes be difficult to give straight forward recommendations for the hot and very corrosive environments found in pickling plants. The use of plastic components without correct corrosion resistance data can be regarded as full scale experiments. Consequently, there is a need for more knowledge on plastic corrosion to improve safety and service reliability in European steel plants.

PLASTIC CORROSION:

Chemical resistance of plastics can be described especially by the change of mechanical properties, chemical composition, chain length or amount of additives. Important parameters which influence the long-term behavior of plastics are temperature, chemical impact by acid exposure and mechanical

impact by abrasion or cavitation. For plastic parts used in process equipment the following corrosion effects have been identified:

Uniform corrosion: The component lifetime is determined by the time needed to consume the wall thickness by chemical reaction. This is relevant for environments such as nitric acid and sulfuric acid.

Diffusion, softening and swelling: Chemicals can diffuse into the plastics materials reducing strength and reacting with additives, e.g. hydrochloric acid and hydrofluoric acid.

Depletion of additives: Most additives - such as stabilizers, fire retardants or antioxidants - are not bound to the polymer backbone and may be washed out when in contact with the pickling acid.

Surface crack formation: Depending on the process conditions, surface cracks may be generated during periods of dry out when the environment causes an embrittlement of the pipe wall.

Degradation of functional groups: In acid regeneration technology membranes as well as ion exchangers are employed, which may lose their specific properties when in contact with acids at elevated temperatures.

Often, in process equipment a combination of the different corrosion phenomena is observed.

RESULTS:

Samples were taken from plastic parts which had been in operation for several years in different European pickling lines. The analyses of the samples led to following findings:

Crystallinity is a very important parameter for the performance of polypropylene (PP) in pickling acids. The processing of the plastic armatures and fittings affects the total degree of crystallinity, its distribution and the type of crystals. The higher the crystallinity, the lower is the acid diffusion rate and the smaller is the acid attack on the material. Figure 1 shows the influence of different processing techniques on plastic corrosion (all parts PP from the same supplier).

Injection moulded parts: multitude of micro cracks

Extruded pipe: not affected

Fig. 1: Influence of processing parameters on acid attack

Page 173: 2-page abstracts booklet

Diffusion of acid into the polymer material influences also the weldability. This is the reason why joining new plastic parts into an existing system is often difficult and may require other techniques than welding.

Generally, welds are weak points of pipes and tanks. Obviously, temperature conditions, change in crystallinity and oxidation of the polymer chain promote acid diffusion and the formation of cracks (Fig. 2):

Fig. 2: Considerably weakened weld

Polyvinylidene fluoride (PVDF) is stable against all conventional pickling environments. However, it allows the diffusion of acids. If a PVDF-tank is provided with a supporting laminate made of fibre-reinforced polymers (FRP) a proper selection of barrier layer, fiber backing material and resin prevents the delamination of the different polymer layers of the wall. Large scale delamination may result in a collapse of the whole tank structure (Fig. 3):

Fig. 3: Damage of a PVDF-tank re-inforced with FRP

Polymer membranes used for the regeneration of spent acids are prone to chemical attack, too. The damage of these membranes can cause substantial economic drawbacks due to increased fresh acid consumption and increased efforts for the

neutralization of the surplus waste solutions. Figure 4 depicts the surface of a damaged filtration membrane.

Acid attack on a filtration membrane

SUMMARY AND GENERAL RECOMMENDATIONS

Based on the results generated so far the following actions for optimized operation, maintenance and purchasing procedures of plastic parts used in pickling lines are recommended:

• Keep track of all installations by labels indicating installation date, material and supplier. This is often missing for pipes.

• Regular inspections and collection of samples for evaluation during service to keep track of the status of the equipment and avoid surprises.

• Insertion of test samples into the process for corrosion monitoring and evaluation of alternative materials.

• Establishment of a cadastral register of plastic pipes and components (including supplier, specification, and age of the material).

• Deployment of certified plastic welders.

• Involvement of the purchasing department: Use only certified suppliers of plastic parts.

• Investigate any failures and unexpected corrosion effects and take precautions to avoid it from happening again.

Missing adhesion between the layers

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New Siemens VAI pickling model helps to improve surface purity -

FAPLAC® APM

K. KOFLER*, S. WALTER, P. BARBIERI (Siemens VAI Metals Technologies GmbH), Austria

Covering today’s market requirements many steel producers are obliged to variably adapt its production by means of finishing all sorts of steel qualities on demand. The solution is the SIROLL FAPLAC® APM (advanced pickling model) which takes into account a certain number of coils of a scheduled production for pre-calculation. By this optimum balance of utilization in terms of economized energy input, minimized rate of over-pickling and optimum strip speed can be achieved. SIROLL FAPLAC® APM is an adaptive online Level 2 model that further improves the pickling process and pickled strip surface quality. Considering all key pickling parameters (steel grade, strip thickness, rolling and coiling temperatures, bath temperature and chemistry, etc.), the optimum line speed (fast response) and temperature curve (slower response) is calculated for discrete strip segments. Up to 100 coils can be calculated in advance to optimize pickling planning. With FAPLAC process automation it is not necessary anymore to run production campaigns and put several products on stock. The core of the FAPLAC Advanced Pickling Model bases on a physical-chemical model which outputs the optimum strip speed for any particular steel grade. For individual qualities this model takes scale formation and scale properties into account that were formed during hot rolling. SIROLL FAPLAC® APM is fully integrated to SIROLL CM. It is linked to Speed Optimization System of the overall line including terminal sections, looper sections, side trimming section and mill area. SIROLL FAPLAC® APM is applicable for all CPL, PLTCM and PPPL. Two pilot applications foreseen for linked pickling line-tandem cold mills in China and Europe.

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Pickling line/tandem cold mill with electrical and automation systems

from SMS Siemag successfully commissioned at MMK

Detlef Ehlert, Dr. Michael Bühren (SMS Siemag) Sergey Nikolaiwitsch Ushakov (Magnitogorsk

Iron & Steel Works)

ORDER

The Russian steel company MMK, Magnitogorsk Iron & Steel Works, placed an order with SMS Siemag in July 2007 for the construction of a new cold strip complex, which was put into operation in 2011. MMK is one of Russia’s leading steel producers and is expanding its production of high-grade cold-rolled and galvanized strip with this cold strip complex.

SMS Siemag’s supply scope comprised all of the mechanical components for the cold strip complex, the entire X-Pact® electrical and automation system, including the power supply and drive engineering and all auxiliaries.

THE CONTINUOUS PICKLING LINE/TANDEM COLD MILL AT MMK

In the entry section of the production line, a welding machine joins the strips into an endless strip, which is then pickled in the turbulence pickling line at a maximum process speed of 280 m/min. The pickling section, comprising four tanks each of length 35 m, is the longest in the world.

Fig.1 MMK`s long pickling line

Integrated in the pickling cycle is a regeneration plant supplied by SMS Siemag for reconditioning the hydrochloric acid. The operation of this facility is extremely efficient. 99 percent of the acid can be reutilized.

The entire pickling process is checked and controlled by our pickling model of the X-Pact® electrical and

automation system. To perform temperature optimization, the pickling model takes into account the strip which is currently in the mill and also the subsequent strips. The pickling model allows quick adjustments to varying strip requirements via the set-points for the speed-controlled pumps in the pickling circuit. The strip speeds in the process section of the picking mill are calculated in advance on the basis of the production schedule, taking into account the strip preparation times in the entry section. A continuous and highly productive plant operation is thus attained together with an automatic level control of the three horizontal strip accumulators. The result: an optimum pickling result with minimum use of energy.

The pickled hot strip is rolled down on the five-stand four-high tandem mill to final gauges of 3.0 to minimum 0.28 mm. With its high total drive power of over 45 MW and rolling forces of 35 MN per stand, the plant is optimally equipped for processing high-strength steel grades with a view to future market developments. All millstands are equipped with CVC®

plus and all state of the art actuators to ensure best thickness and flatness results. In addition, all plants and facilities are equipped with comprehensive measuring technology, such as roughness, thickness and flatness measurement, covering the full length of the process.

Fig. 2 MMK`s tandem cold mill in CVC® plus 4-high design for a capacity of 2.1 million tons per year The work rolls are changed fully automatically and within minutes. Three strip accumulators ensure optimum production conditions in both plant sections. An automatic system coordinates the levels of the strip accumulators with the production schedule. The mill is started up after the roll change by means of our new automatic start-up system. The plant operator initiates the preparation of the plant by pressing a button; this means build-up of tension and force. With the start button, it enables the acceleration of the mill. The automatically activated gauge control ensures that the required target thickness is attained quickly. This start-up concept, designed by SMS Siemag, offers the plant operator yet another advantage for attaining high production and strip quality.

When the weld seam to the subsequent strip passes through, the mill automatically decelerates and the new geometry and material data are processed by an optimum interaction between the X-Pact® Level 2 set values and the X-Pact® Level 1 controls.

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The result of the accurate re-ramping of the set values is a minimum off-gauge length and minimization of the danger of strip breaks. The deceleration and subsequent running-up of the mill speed take place with maximum acceleration.

For optimum flatness control, the tandem cold mill is equipped with multizone cooling in the last stand and with the flatness measuring roll developed by SMS Siemag. The Dry Strip System is blower type, minimizing operation costs and residual oil content. The exit section of the tandem mill is equipped with a double coiler station for rapid coiling of the strips. Also included is the "Rotary Inspect" inline inspection line, newly developed by SMS Siemag, to enable quality control to take place during the production process.

PLUG & WORK

The automation system of the pickling line/tandem cold mill was tested by SMS Siemag before delivery, using the testing method Plug & Work: Therefore the complete automation system has been set up in the test field, Plug & Work simulates the production process and allows the automation functions to be tested and optimized under realistic conditions before installation at MMK. In addition MMK-operators are trained under very realistic conditions for their future job. Thus this SMS Siemag concept contributes to a shorter commissioning period.

Fig. 5 Main control pulpit of the tandem cold mill with latest generation HMI

COMMISSIONING AND RESULTS

The modular mill design, the preassembly of key components and the extensive functional tests as part of the Plug & Work tests were the best preconditions for smooth installation and early commissioning. Already six weeks before the contractually agreed date, it was possible to roll the first strip on the mill on 31 May 2011. The first 20 strips were pre-pickled. They were already of saleable quality on being processed on the tandem mill. After the pickling section had been filled with acid and put into operation within a very short time, pickling was performed on the line as of 20 June 2011. Five weeks after the first strip was rolled, the plant was already producing in two-

shift operation. During this phase, the first trial strips for applications in the automotive sector were manufactured and successfully certified. The official inauguration of the pickling line/tandem cold mill took place in mid-July 2011.

As early as the first few weeks of the run-up phase, the plant was able to satisfy the production requirements for supply to the end-use customers. Within a period of merely two months, the production range involved here had covered virtually the entire contractually envisaged scope of strip gauges and widths.

Fig. 3, 4 Development of the range of gauges and widths for production

As the technical optimization of the plant continued, the maximum rolling speed was also able to be increased very quickly to the contractually assured level. Already about three months after the first strip, it was possible to achieve a stable strip speed of 1500 m/min in the final stand while maintaining the excellent strip quality.

The productive output of the plant was raised continuously during the first four months. Daily production quantities of up to 4,600 t have been attained so far.

The product range already comprises a wide variation of steel grades. Thus, during the first five months, strips extending from low-alloy carbon steels to dual-phase grades were able to be produced. These embraced a yield-point range of 210 up to 690 N/mm².

The particular flexibility of the X-Pact® automation system made it possible for MMK to provide new and sophisticated products to be offered on new markets already in the hot commissioning stage.

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Asolid laser Welder

Hervé THOMASSON (Siemens VAI)

For many years, the mash lap technology for welding light gauge strip has been the only alternative to steel suppliers. But the search for better weld profiles with no over thickness as well as increased component lifetime, and the move towards higher strength steels has led to other technologies such as laser.

In the last few years the requirements for processing lines and for the SIROLL welder product have changed tremendously with: • The emergence of new steel grades with TRIP and

DP steel already reaching 1000 / 1400 MPa and future steel reaching potentially 2000 MPa tensile strength.

• Changes in the strip format range with ever thinner gauges.

• High level of performance with perfect welding quality criteria (weld robustness, over thickness…), automatic welding quality control and annealing system.

The welder performance must, therefore, incorporate all of the above aspects to be able to meet the current and future requirements of the steel industry.

An extensive R&D program has been conducted since years by Siemens Metals Technologies in the field of welders. After the development in the 90’s of new « Flash Butt » welder concept (pickling entry section, fully continuous rolling mill …) and a new « Mash Lap » welder concept (galvanizing line entry, continuous annealing, inspection lines …), the program was then focussed on laser welding process. . Light laser welders (for galvanizing, annealing, finishing lines) and heavy laser welders (for pickling line and tandem mill) were the results of this R&D program with a first machine installed in 2004 using a CO2 laser source.

Through continued research efforts and always willing to be ahead in term of technology, Siemens Metals Technologies has now reached a new step with the integration of an ASOLID laser source to its light laser welder. This laser source is replacing the CO2

resonator. The ASOLID technology already used on other industry sectors like automotive, tailor blank welding... leads to different and significant advantages compared to the CO² solution. The ASOLID technology makes it possible to transmit the beam from the laser source to the process heads (cutting and welding) through optic fibre instead of using mirrors.

for cutting and welding, easier maintenance with no mirror installed on the machine…

Simple beam transportation:

By using optical fibre to transport the beam from the laser source to the process heads (one fibre for cutting and one fibre for welding), the Customer does not have mirrors or beam switch on the machine. With this beam transportation system, the adjustment of the welder is very easy and the maintenance operations are reduced to almost nothing for the beam path.

With the length available for the fibres, it is possible to install the laser source separate from the welder. Therefore the laser source could be installed in a dedicated space or room. Additionally, without laser source on the machine, the space required by the machine mainly on the motor side of the line is reduced (2 meters less). This point could be a key aspect in case of lines being revamped where the space is often an important issue.

Higher efficiency:

With a higher efficiency, it makes it possible to decrease electrical consumption and sizing of other systems like the cooling unit. At a same laser power level, installed electrical power for the chiller and laser source could be reduced by 50%.

Higher performance in cutting and welding:

Because of the higher quality of the beam, with a same laser power installed, cutting and welding speed will be higher with a gain from 10 to 50 % depending of the thickness.

Based on the experience and know how as a product and line supplier, the Siemens Metals Technologies policy is to be able to propose to its Customer different products - from more conventional machines to advanced technology like laser. An important part of this approach is the permanent and intensive Research and Development effort with the goal to always propose better solutions to our Customer.

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When thinking about better solutions, with its field experience and industrial feedback, Siemens Metals Technologies is always thinking of different aspects from installation, ROI, consumption, maintenance to service support and last evolution of our LW21L laser welder is fully adhering to this policy with higher efficiency and performance level, easier installation, reduced maintenance. And with a lower investment level, this new LW21L evolution represents important gains for the Customer.

But of course, this is not an end and Siemens Metals Technologies will pursue its goal of always proposing better products and better solutions for its Customer to support them for new challenges.

This new technological step gives a lot of benefits to steel producers with among others, a higher efficiency, lower consumptions, higher process speed

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Benefits of Chrome Plating and Long-Term Viability of Use in the

Rolling Industry

G.PENZES (Nord Chrome)

The process of chrome plating (CD) the work rolls was developed in 1975 in North America and Europe by CHL (Court Holdings Ltd) and expanded for use worldwide in rolling mills application. The process is unique and differs from the normal hard chrome plating process due to the specific chrome deposit properties that are required for rolling mills application. In particular the very thin hard chromium layer is required to both withstand the very high forces in metal rolling mills, and also to impart the product and process benefits that have led to it being a standard and essential aspect of rolls technology.

BENEFITS OF USING CD ON WORK ROLLS

The CD process is a primary requirement or a “must have” for Ferrous and non-Ferrous rolling mills work roll application. This process consists of electrolytic deposition of a metallic chrome layer which has specific and unique properties. This layer has a micro-cracked structure (high density of narrow and shallow cracks) providing low stress, high lubricity, low coefficient of friction and high reproducibility of the substrate roughness.

High density micro-cracks act as lubricant reservoirs and effectively reduce the strip/roll contact area.

The table below list the key properties of the chrome layer, together with the reason why it is important and the benefits to metal rolling mill application and end products.

Hardness Robustness, Ability to withstand wear and damage

Resistance to rolls damage, Reduced stock removal

Wear resistance Ability to resist wear and stand up in the mill

Increase rolls life, Reduce mills downtime

Presence of micro-cracks Lubrication improved in the bite, enhance coolant performance Flexibility to withstand deformation in rolling (thermal crown, bending) Less effect of dissimilar metal, Thermal coefficient of expansion, corrosion site spreading

Improve coils flatness Improve cleanness of the strip Improve roughness on galvanizing lines

Coefficient of friction Resistance to wear and better lubrication in the roll bite (lower mill force)

Improve mill reduction or energy savings Improve flatness

Ductility Ability to withstand the deformation in the mil and dissimilar metals thermal coefficient of expansion

Reduce incident in the mill, i.e. downtime and roll stock removal  

Adhesive strength to substrate Requirement to stay on roll under rolling conditions

Prevent quality issues  

Ability to deposit to different materials Is able to deposit on to different roll materials (cast iron, forged steel, Hi Cr, HSS, Semi HSS, tools steels) without major adjustments to plating process

Increase choice of rolls manufacturer and variety of inventory 

Resistance to metal pickup Chromes position in the galvanic series results in acting as a chemical barrier to the transfer of metal (aluminum, nickel, copper, brass, gols, etc…) to the roll

Longer rolling life Less metal loss 

Reproducibility of the substrate surface roughness Is able to mirror the substrate surface

Increase textured roll life Improve roughness transfer 

Corrosion Longer shelf-life for roll dues to resistance to oxidation

Reduce rework process

Furthermore, the process gives additional value added:

Economical due to the plated hardness and wear resistance (the rolls life in the mill could be improved by 1.5 to 8 times using the CD process depending on the stands and the mill or 2.5 in average)

Flexibility due to no-dependence of the process to the rolls materials giving wide rolls inventory materials

Easy grinding conditions, the chrome layer does not affect grinding parameters

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LONG TERM VIABILITY, SAFETY & ENVIRONMENTAL IMPACT

Risk control

To achieve the required properties of the deposited chromium metal, a specific electrolyte chemistry is required which includes various chromate species, with the hexavalent species being a key ingredient.

Significant improvements in risk control have been made over the last 20 years, rigorous adherence to legislation and internal best practice sharing has reduced any health or environmental risks within CD plants to a very low level.

In addition, chromic acid used for this application is converted by electrolysis into chromium metal which is deposited on the roll surface. It is the chromium metal which is present on the work rolls when supplied to the metal rolling mill users. This therefore guarantees that supply chain users (rolling mills) and end-consumers (OEM industry sectors and general public) are not exposed to any SVHC.

Environmental balance

The chrome metallic layer on the roll contributes a minor percentage of the total chrome content of the rolls which typically have between 3 and 5% chromium added as alloy additional during the roll manufacturing process.

Using chrome deposit on rolling mill work rolls increases roll life, reduces work roll usage, reduces grinding operations, reduces rolls manufacturing…

Therefore, using chrome deposit gives a positive environmental balance regarding energy, COV impact and waste management.

Alternatives to CD

Despite years of efforts to find alternative coatings or type of rolls that would withdraw CD requirement, there is no alternative process available. Particularly, HSS or Semi-HSS rolls are not able to achieve a similar range of properties and benefits compared to a micro-cracked metallic chrome surface.

Thus, HSS rolls introduce new constraints to roll shops, such as cracks detection during grinding operation, grinding productivity, stock removal on rolls,

And new constraints to mill users, such as thermal properties leading to inadequate flatness and cleanness of the strip,

Current efforts are focused on green coating based on chrome deposit leading to equal properties with safer process.

Reach

Reach introduces new requirements regarding use of chromium trioxide in the EU after 2016, companies using chromium trioxide will have to file an authorization of application with ECHA at the latest by November 2014. NC is involved in the Chromium Trioxide Authorization Consortium to prepare authorization dossier as major actor in rolls chrome plating.

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Session 13: Cokemaking

Table of Contents

13.1 The new stamp charged coke oven batteries at Zentralkokerei Saar of DillingerHütte - Technical characteristics and operational experience Y. HERRMANN (Zentralkokerei Saar GmbH), B. DELLMANN (HBD Engineers), Germany, T. HANSMANN (Paul Wurth Italia SpA), Italy, W. FAUST (Paul Wurth SA), Luxembourg

13.2 Production of metallurgical coke with hypercoal (ash free coal) - The use of non / slightly coking coals as a coke feedstock T. TANAKA, T. SHISHIDO, N. OKUYAMA, M. HAMAGUCHI, N. KIKUCHI (Kobe Steel) A. KOTANI, Y. NISHIBATA (Kansai Coke and Chemicals Co Ltd), Japan

13.3

Recent operation of new coke plant in Gwanyang works, POSCO M.W. OAK, J.S. EUN, D.H. KIM, D.C. YIM (POSCO), Korea

13.4

Industrial Measurement of pushing force using torque sensors M. LANDREAU, Y. HERGALANT, D. ISLER (Centre de Pyrolyse de Marienau), F. ENTRINGER, D. DUMAY (ArcelorMittal Florange), France

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The new stamp charged coke oven batteries at Zentralkokerei Saar of

Dillinger Hütte – Technical characteristics and operational

experience Yves Herrmann (Zentralkokerei Saar GmbH)

Bernd Dellmann (HBD Engineers)

Dr. Thomas Hansmann (Paul Wurth Italy)

Winfried Faust (Paul Wurth Luxembourg)

Since 1984, Zentralkokerei Saar (ZKS) operates two stamp charged coke oven batteries with a chamber height of 6.25 meters and with a high operating rate.

Starting from 2001 heating wall damages and blocked regenerators induced production losses and increased emissions.

First ZKS investigated different repair methods (cold, hot) for both batteries. Finally ZKS decided under consideration of production losses in case of a repair and the longer expected life time of new coke oven batteries to build one new designed coke oven battery on a new foundation (Battery no. 3, 50 ovens) and to substitute one of the existing batteries by reusing the existing foundation (Battery no.1, 40 ovens).

Picture 1: New Battery no. 3

The main reasons for this decision were:

- Maintaining of the coke-production at a sufficient level with permanently 2 batteries in operation

- Possibility to introduce new design solutions for the new batteries

- To increase the stability of the ovens for stamp charging process

- Improvement of the environmental aspects by integrating innovative solutions.

The renovation project was planned in three steps.

Step 1: New Battery no. 3 under erection, “old” Batteries. Noes. 1 and 2 under production

Step 2: Battery no. 1 shut down and under re-erection, “new” Battery no. 3 and “old” Battery no. 2 under production,

Step 3: Battery no. 2 shut down, “new” Battery no. 3 and “new” Battery no. 1 on existing foundations under production.

The old batteries presented after 25 years high rate of severe operation damages. The conclusion of the damage analysis revealed 3 main causes:

- Insufficient heating wall stability when substituting local coal blends by imported ones for stamp charging

- Insufficient flow distribution in the regenerators due to frequent repair work

- Insufficient gas tightness of heating walls

For these reasons the following improvements have been implemented in the new batteries.

- Higher stability of the heating walls by increasing the heating wall width

- An extraordinary strong bracing system for heating walls, oven roof and regenerator area

- Better linkage between heating wall and corbel area

‐  Improved  joint  design  in  the  heating  wall  for preventing  gas  passages  between  chambers  and heating flues 

The new batteries are designed as gun fired batteries for coke oven gas as well as for mixed gas. The heating flues are twin flues with staggered air and waste gas recirculation for a uniform temperature distribution over the oven height and length of the heating wall and for reduced NOx emissions even at high flue temperatures. For matching the requirements of a stamp charged battery the regenerator of the oven is divided into different compartments, which allows separate regulation of the first four and last four heating flues of each heating wall.

For elimination of emissions at any battery openings the batteries are equipped with spring loaded diaphragm coke oven doors and water sealed ascension pipes and mini stand pipe lids for charging gas transfer.

Both batteries are designed in accordance to match the gas availability and requirements of the steel plant. The battery no. 3 can be changed automatically, wholly or partly (20 ovens + 30 ovens), from rich gas to mixed gas. Alternatively, a substitute gas on the basis of natural gas can be used instead of rich gas.

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For regulation of the pressure in the oven chamber during charging and over a complete distillation cycle a special regulation valve has been developed and installed on the new battery no. 3. It is supplied by Paul Wurth Company under the trade mark SOPRECO® (Single Oven Pressure Control). It is a mechanical valve placed between the isolating valve on the collecting main and the elbow of the ascension pipe. The SOPRECO® System consists mainly of a mechanical valve, a pneumatic actuator, a pressure measurement system for the oven pressure at the basis of the ascension pipe with a pressure transmitter and a PLC for the control of the valve.

Natural gas can also substitute rich gas in case of blast furnace gas carburation.

For improvement of the safety of operation all functions of the valves and waste gas boxes are controlled by infrared systems. Integrated degraphitizing air and nitrogen flushing ensures a safe and trouble free operation of the heating system and its gas channels and nozzles

In a stamp charging battery it is a challenge to prevent charging gas emissions on the machine side during the charging sequence.

Experience delivers that the conventional systems for sucking off the charging gases by high pressure water injection and by charging gas combustion cars are no longer efficient for stamp charged batteries.

For this reason ZKS has performed measurements and tests, thus developing a concept to eliminate completely emissions at the machine side during the charging process. This inovative concept consists of exhausting the charging gases by an underpressure in the collecting main during the charging phase of the oven “n”. During charging the gas is also sucked simultainously into the ovens “n+2” and “n+4” via jumper pipes, and tranfered into the collecting main

Picture 3: SOPRECO® regulating valve For the charging gases transfer to the nearby ovens especially built machines are designed, named FüM (“Füllgasüberleitmaschine”).

All ovens of the new coke oven battery no.3 are equipped with SOPRECO® valves. Since the first charge of the battery in February 2010 they are running without mechanical or control problems. Also expected problems with accumulations of tar deposits could not be observed. The SOPRECO® system is generally an independent control system but here connected with the battery control system for supply of all necessary data like grade of opening, oven pressure etc.

Picture. 2: FüM and arrangement of mini stand pipe

Tests executed by ZKS on the old existing batteries delivered that a under pressure around - 600 Pa in the collecting main would be necessary to avoid the emissions during the charging sequence. The experience since more than two years in operation of the new battery no. 3 delivered that - 400 Pa during charging and 0 Pa during the normal distillation time is sufficient for preventing gas emissions during charging and during the distillation time. A regulated pressure of + 130 Pa is maintained in all neighbouring oven chambers connected to one collector main even during charging.

Picture 4: Arrangement of SOPRECO®

On the basis of the good operational results also the battery no. 1 will be equipped with SOPRECO® valves of unchanged design.

Battery no. 1 is scheduled to be put into operation this year.

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Recent Operation of New Coke Oven in Gwangyang

Myoung-woo, Oak

Coke Making Departiment

in GwangYang Works, POSCO

INTRODUCTION

Background of construction :

In the 2,000s, GwangYang Works has supply short-age of Coke due to the expansion of blast funance volume and is operating maximum production, con-tinously. Even if the coke productivity was increased through operated CMCP (Coal moisture control pro- cess) and increased charging weight, GwangYang works imported coke to solve the coke shortage since the middle of 2000s. But, purchase price of imported coke and china coal was increasing tremendously. Also, the imported coke was divided into many piece and it has too much moisture to use from blast fur- nace. So, in the 2008s, to solve this problem, Gwang-Yang work decided on a direction to construction investment of new coke plant which has 2.32milllon ton/year coke production capacity to stable supply the coke into the blast furnace. Therefore, it was desired to cover the coke demand by self-producted coke.

[Fig1. Coke supply and demand in GwangYang ]

To use the construction site effectively and to collect the By-Product such as coke oven gas, New coke plant in GwangYang was adopted “Uhde(Otto)” oven type coke oven compared with “Non–recovery” type which was required more building site than “Uhde”

type and SCOPE21 (NSC) facility which need more technical verification about the introduce necessity

The new coke plant takes the thirty-eight months con-struciton period from begin construction in Novem-ber 2008. To explain more detail, 5B battery was com-pleted in December 2010 first, and 5A battery was erected in Noveber 2011 thereafter.

RECENT OPERATION OF NEW COKE PLANT

Specification and Charateristic

[Table1. Specification of coke oven in GwangYang]

According to specification of new coke plant, it is consist of four batteries: each batteries has fity-coking chambers. Two-hundred coking chambers are posse-ssed totally. Concerning the charging weight in the coking chamber, new coke plant charging weight which has 57.8ton/ch is 1.8times larger than conven-tional ovens which has 32.0ton/ch in GwangYang with large scale oven trend. And according effective vol-ume, it has also 76.0 square meter compared with conventional ovens which has 43.1 square meter. It’s approximately 1.7 time large. Therefore, new coke plant takes 26.7hrs coking time. It takes more 1.5-times long.

For the improving coke quality, New coke plant also equipped one CMCP and two CDQ (Coke Dry Quen-ching) facilities which was adopted to all coke oven in GwangYang. As expansion of coal transportation capacity and intergration of one coal handling control room which was divided each plant, new coke plant is able to work without an additional open yards.

Working ratio and moving machine

As following that capacity increasement plan, the pushing number was increased continously according to plan. The maximum pushing number is 90 per day.

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[Fig2. Operation result of 5B battery]

And the maximum pushing was reached at 62 days after first coke. Concerning the moving machine, all of machines which is pusher cars, charging cars, trans-fer cars, quenching cars, locomotive cars are auto-matic remote controlling by only one operator who works in main control room.

Coal moisture and coke quality

As mensioned earlier that new coke plant has high charging density and effective volume, the coal moisture which charge into coking chamber is 7% and the average coke Drum Index (DI150) is 86.8% in 2011.

CONCLUSION

In consideration of coke shortage and expand pro-duction capabilities of crude steel, The GwangYang works constructed new coke plant which coke pro-duction capacity is 2.32millon ton per year. Following the construction trend of large size coke oven and for the minimizing of construction site, new coke plant was adopted 7.6meter high oven which is “Uhde” type. Through the increasing coal handling capacity and operation efficiency, it can works without building of open yard, additionally. Finally, as high charging density and charging weight, new coke plant is pro-ducting the high quality coke that DI150 is 86.8% with 7% coal moisture.

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Industrial Measurement of Pushing Force using Torque Sensors

M. Landreau, D. Isler (CPM, Forbach)

Y. Hergalant (CPM, Forbach)

F. Entringer, D. Dumay (ArcelorMittal, Florange)

INTRODUCTION

Pushing problems occur from time to time in coke plants. The reasons for the hard pushes can be related to different factors (the coal blend, the coking conditions, the oven conditions, the pushing machines...).

Nowadays, pushing force is calculated by the majority of coke plants from motor amperage and sometimes, but quite rare, measured by a torque meter.

INDUSTRIAL MEASUREMENT OF THE PUSHING FORCE

Various possibilities to measure the actual pushing force have been investigated. The simpler way is to measure the mechanical torque on the pinion driving shaft. ArcelorMittal Florange coking plant has been chosen to measure the pushing force. Pushing machines 1 & 2 have been equipped both with a torque sensor installed on the pinion driving shaft.

Torque sensor on the pinion driving shaft

This measurement is based on micro-deformation in torsion of the driving shaft. 4 strain gauges must be pasted on the periphery of the shaft. Power supply and signals of the strain gauges are transmitted via an antenna which is contact less. Figure 1 shows a picture of the torque sensor on the driving shaft.

Figure 1: Torque sensor installed on the driving shaft

of the pusher ram.

This system is small and easy to fit. A metallic cover as well as a heating box have been installed to protect electronic from dust and low temperature.

An example of recorded curve is given on the following Figure 2.

Figure 2 : Typical pushing force at Florange coking

plant.

This curve is typical of normal push at Florange coking plant. The force peak is not very sharp and sometimes there are twin peaks. This is possibly related to the movement of coke pieces during the compression step before the coke cake starts to move.

Calibration device

An important step before measuring the force at the interface between the machine and the coke cake head consisted in designing a calibration unit at one end of the battery with a reference load cell. The designed calibration unit is shown on Figure 3.

20°

Force sensor

Spring

20°20°

Force sensor

Spring

Figure 3: Principle of the calibration unit and

installation at Florange

The calibration unit has been first checked in a hydraulic press in Florange workshop and then mounted on a I-beam at one end of Florange coke oven battery. Several tests were carried out in static condition (Figure 4), i.e. pushing to a certain compression of springs and measuring both brake torque and force on the calibration rig.

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This chart highlights that there is a disagreement during starting up and acceleration steps, and then an excellent agreement between calculated and measured force. Indeed, as presented on the figure, as long as the engine speed is not constant, the formula used by coke plants is not valid. Thus, only measurements performed with torque sensors allow to obtain the true force values during pushing operation.

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Torq

ue s

enso

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)

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The torquemeter allows also plotting 3Dchart and so, to follow force evolution during pushing. This global overview of pushing can be used to detect wall deflection, or sole defects. The Figure 6 presents a superposition of different pushings. It can be noticed that the shape of curve is different from an oven to an another. Thus, for example, oven n°5 presents high force in the second part of the pushing due to wall and sole degradations.

Figure 4: Calibration of the torque sensor in static conditions.

As shown on Figure 4, the pushing force of the machine is limited to 400 kN. Values of the force calculated from torque and measured by the calibration rig are equal for forces superior to 250 kN. In the case where forces are inferior to 250 kN, torque sensor overestimates force perhaps due to friction in the calibration unit. Indeed once an important load is applied, the plate friction decreases and so, there is a good correlation.

5 10 15 20 25 30 35 40 45 50 55 60 3 8 13 18 23 28 33 38 43 48 53 58 63

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5 612.114 617.119 5

2224.426.929.4

31.8

34 3

36.8

39.2

41.7

44.1

FORCE CALCULATED FROM MOTOR AMPERAGE VERSUS TORQUE SENSOR MEASUREMENTS

This part consists in comparing the force calculated from motor amperage by Florange coke plant (like the majority of coke plants) and force measured by torque sensors installed on pushing machines. The following formula is used by the coke plant to calculate the force during pushing :

DVRIUF me

×××××××

ηη 60 Figure 6: 3D display of force during pushing.

With: U tension (V), I motor amperage (A), ηe and ηm respectively electrical and mechanical efficiency, R reduction ratio, V engine speed (rpm), D diameter of reduction gear pinion (m) and F force applied by pusher ram on coke during pushing (N).

CONCLUSION

Pushing force can be measured with a good accuracy by a torque sensor based on strain gauges pasted on the driving shaft.

The pushing force typically shows a peak at the beginning of pushing when the coke cake begins to move. Peak forces calculated from amperage are not correct, especially during hard pushes and so, this calculation could prevent to foresee possible stickers. A 3D display allows an overview of pushing and can help coke plant managers to plan maintenance operations.

The Figure 5 represents forces calculated from motor amperage and force measured by torquemeter.

ACKNOWLEDGEMENT

The authors wish to thank the European Union RFCS program (Research Fund for Coal and Steel), for their financial support to this work in the frame of the project called “Coke Oven Operating Limits” (ref. RFCR-CT-2006-0004).

Figure 5: Comparison between calculated and measured force.

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Session 14: Slab continuous casting

Table of Contents

14.1 Investigation of the influence of mould oscillation on the continuous slab casting G. XIA, C. FÜRST, K. BURGSTALLER (voestalpine Stahl), Austria

14.2 Development and application of a non-steady state strand solidification model G. STEPHENS, A. STRAKER, B. BARBER, B. HOOPER (Tata Steel Europe Research Development and Technology), United Kingdom

14.3

Innovative New 250 / 350 mm continuous caster in Salzgitter P. MULLER, M. SCHÄPERKÖTTER, S. ROSSIUS (Salzgitter Flachstahl GmbH), M. REIFFERSCHEID, C. GEERKENS, L. FISCHER, U. KERP (SMS Siemag AG), Germany

14.4

Operational results of the world's most modern Siemens VAI bow type caster withvertical mold for the production of 355 mm thick slabs for demanding quality requirements M. HADLER, E. REISENBERGER, A. EICHINGER (Siemens VAI Metals Technologies GmbH), C. FÜRST, H. UNTER, P. HODNIK (voestalpine Stahl GmbH), Austria

Page 191: 2-page abstracts booklet

Investigation of influence of mold oscillation on continuous

slab casting Guangmin Xia, Christian Fuerst and Karl

Burgstaller voestalpine Stahl GmbH

The continuous casting with a casting speed of 0.5 to 2 m / min without mold oscillation is not possible. By the mold oscillation sticking of the newly formed strand shell on the mold wall is prevented. It is well known that this practice influences the surface quality of the slab. It causes oscillation marks in the form of notches which are perpendicular to the casting direction. The formation of oscillation marks depends on the type of steel grad and casting conditions. These marks can be starting points for defects on the slab, like formation of transverse cracks and inclusions just below the surface of the strand.

In the present paper the results of metallographic investigations and of plant trials are reported. METALLOGRAPHIC INVESTIGATION A lot of metallographic examinations on the slab specimen show that most defects on the strands surface or in the subsurface, like gas bubbles, inclusions, cracks, occur on the bottom of oscillation marks.

For steel with carbon equivalent Cp = 0.08 to 0.14 by mass% the following types of oscillation marks were found, see Fig.1:

- Trough-shaped and edge-shaped oscillation marks. - Oscillation marks with an overlapping with one separation line or two separation lines.

For ultra-low carbon steel (ULC) two typical oscillation marks were found: Trough-shaped oscillation marks and oscillation marks with an overlap.

The ratio of oscillation marks with overlapping depends on steel grade and position on the slab surface. For steel with Cp = 0.08 -0.1% by mass, the oscillation marks with overlapping are found mainly at slab edges, The ratio of marks with overlapping at the slab edge amounts to 60%. For ULC steel with C = 0.003 mass% the oscillation marks with overlapping are not only found at slab edges, but also outside of slab edge area. The ratio of marks with overlapping at the slab edge amounts to 100%. The ratio of

marks with overlapping at the broad side in the center on the slab surface amounts to 40%.

For steel with carbon equivalent Cp = 0.08 to 0.14 by mass%, it was found that the deepest oscillation marks and hooks are found mostly at the edges area of slab. The depth of oscillation marks and hooks decreases with increasing distance to slab edge.

Fig.1 Types of oscillation marks, Type 1: through-shaped 2: edged shaped 3: overlapping with one separation line 4: overlapping with two separation lines.

For steel with Cp=0.01 to 0.2 by mass%, the deepest oscillation marks are formed for the steel with Cp = 0.1-0.12 by mass% under the same casting conditions (Fig.2)

Fig.2 Influence of carbon equivalent on depth of oscillation marks

By means of microprobe the overlapping of marks for ULC steel was investigated. It is found that a positive

 

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enrichment of P and Si and a negative enrichment of Mn and Ti occur on the overlapping (Fig.3). The mechanisms of this enrichment are clarified with the help of the simulation of solidification model. The P enrichment is caused by the microsegregation. The enrichment of Mn, Si and Ti is mainly caused by the chemical reaction between the liquid steel and mold slags.

 

Analysis by mass% Si Mn P Ti

Initial concetration C0 0.009 0.19 0.011 0.064

concentration on the separation line CT 0.06 0.1 0.03 0.013

AV 6.7 0.52 2.7 0.2

AV=CT/C0 Fig. 3 analysis results by microprobe PLANT TRILAS A lot of plant trials with different sinus oscillations were carried out.

Oscillation frequencies and stroke height The ULC steel was chosen for the plant trials. In the first series of trials the casting speed and stroke height were held constant. Superheating was hold in small range. The oscillation frequencies were varied from 100/min to 163/min. The aim of these trials is to investigate how the frequencies of oscillation influence the formation of oscillation marks and hooks. In the Fig.4 the trials results are showed. It is seen that under these trials conditions the stroke frequencies have no influence on the formation of oscillation marks and hooks.

In the second series of trials casting speed was held constant and stroke height was varied from 5mm to 8mm. Superheating was hold in small range. The aim of these trials is to investigate how the negative strip time influences the formation of oscillation marks and hooks. This investigations show definitely that the depth of oscillation marks and hooks is influenced by

the negative strip time. With decreasing negative strip time the depth of oscillation marks and hooks decreases (Fig.5).

Superheating and casting speed It is found that the superheating in the range from 20 to 35°C has no influence on the depth of oscillation marks for ULC steel. But the depth of oscillation hook is influenced by superheating. The increase of superheating by 10 °C results in a reduction of the depth of hooks by 15-18%. The casting speed has a great influence on the formation of oscillation marks and hooks. In the Fig. 6 the influence of casting speed is showed. The depth of oscillation marks and hooks decreases with increasing casting speed.

Fig.4 influence of oscillation frequency on depth of oscillation marks and hooks

Fig.5 Influence of negative strip time on depth of oscillation marks and hooks

Fig.6 Influence of casting speed on depth of oscillation marks and hooks

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Development and application of a non-steady state strand

solidification model

Dr G Stephens (Tata Steel, Teesside UK)

Dr B Barber (Tata Steel, Teesside UK)

Mr A Straker (Tata Steel, Teesside UK)

Mr A Hooper (Tata Steel, Teesside UK)

INTRODUCTION:

Continuous casting machines are designed and operated to ensure that during steady speed casting, the sump length is within the containment length, the appropriate part of the sump is within the mechanical soft reduction unit, and the strand surface temperature on entering the straightener is not within the ductility trough.

However, changes in the casting speed may occur during casting, most notably during ladle changeovers, during capping off the strand, and when a potential mould sticker event is detected. Such speed changes can cause the sump length, sump shape and strand surface temperatures to deviate from the design condition.

MODEL DEVELOPMENT:

To specify operating practices that limit the impact of such events on surface and internal quality a three dimensional dynamic strand solidification model has been developed by Tata Steel. It is a finite difference model which allows the calculation of temperatures throughout the entire strand during the whole of the casting process. The model has a three-dimensional mesh through the strand thickness, across the strand width and along its length. Strand movement is taken into account by continually creating a new layer in the mould. This mesh moves in the casting direction at the casting speed, which is allowed to vary with time.

The model takes into account all heat losses from the strand including the mould, rolls, radiation and convection as well as spray cooling, including surplus spray water trapped between the rolls. Within the strand, heat flow is calculated in all three dimensions, taking into account the non-linear evolution of the latent heat of solidification.

This model can be applied to casting slabs, blooms and billets, and takes into account changes in casting speed, spray zone flow rates and teeming superheat. This dynamic model allows sump movement, temperatures throughout the strand and soft reduction target position to be calculated during transient

casting conditions. As a result of changing the casting speed both the strand temperatures and sump position will vary and these are calculated as a function of time see Figure 1

MODEL VALIDATION:

Two approaches were used to validate the model, one qualitative and one quantitative.

For the qualitative validation, the new model was run to calculate the effect of a speed reduction on strand surface temperatures at a position within the spray chamber and a position beyond the spray chamber.. The results are shown in Figure 2. In the first calculation a reduction spray flow rates proportional to the change in speed was modelled. As can be seen the model correctly predicts the initial increase and then reduction in temperature that occurs on plant. In the second calculation, the effects of the dynamic spray control used on many Tata Steel plants to maintain strand temperatures constant during speed changes was modelled, and the much reduced temperature variation seen on plants with this system is correctly predicted.

For the quantitative validation, the new model was run with a constant casting speed and its calculated temperature and sump position were compared with those calculated by a steady state two dimensional model. The latter model has been extensively calibrated using many strand surface temperature, sump length and breakout shell measurements. The sump lengths agreed with each other to within 0.5m, and there was close agreement between the calculated temperatures, see Figure 3.

MODEL APPLICATION:

High levels of broadface transverse cracking were seen on a slab grade, leading to high levels of rejections at the rolling mill, with the “back crop” slabs at the end of each sequence being most severely affected. These slabs are subject to the cap-off procedure in which the strand is slowed to a creep speed for several minutes, and then withdrawn through the machine at a set speed. Mathematical modelling showed that this led to the strand surface temperature dropping into the ductility trough, particularly during this end of sequence procedure.

The proposed solution was to withdraw the strand after cap-off at the highest possible speed that would still keep the 20% to 70% centreline solid fraction range within the fixed mechanical soft reduction. This should improve the slab surface quality without affecting the internal quality. The new model was used to determine the appropriate strand withdrawal speed. Results are shown in Figure 4.

Page 194: 2-page abstracts booklet

The results show that for an increased withdrawal speed of 0.7m/min the 70% and 20% centerline solid fraction positions do not exit the soft reduction area of the slab caster in the time it takes for the back end of the cast to exit the soft reduction area.

Several plant trials were therefore carried out using a trial run out speed at end of cast of 0.7m/min. A tenfold decrease in the level of rejections of rolled product was reported.

Figure 1: Example of an output display from the 3D dynamic caster model

NEXT STEPS:

A management information system is being developed for one of the Tata Steel slab casting machines that will record process parameters that are important for surface or internal quality for every 0.5m of strand length cast. This system will provide a vital tool for research investigations, new product development, quality trouble shooting, and reduced inspection and scarfing costs.

Strand Mid-Broadface Temperatures

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Ratio SprayControl @12m

DynamicSprayControl @6mDynamicSprayControl @12mCast Speed

Figure 2: Qualitative validation

In order for the system to capture the key process parameters that can only be calculated and not measured, the three dimensional dynamic solidification model is being incorporated into this system to calculate important temperatures, sump length and sump shape for every 0.5m of strand cast while the machine is casting, using actual real time process measurements as its inputs. Mid Broadface Temperatures vs Distance From Meniscus

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The model software code was optimised for speed while a high specification computer with a fast CPU was used to ensure that the model could calculate 1s of casting time in 0.8s of CPU time.

The system is currently being commissioned and is expected to go live within the next few months.

CONCLUSIONS:

A three dimensional mathematical casting solidification model has been developed using a finite difference scheme to calculate the effect of changes in casting speed, secondary cooling spray flowrates and teeming superheat on strand temperatures, sump length and sump shape. It has been validated and then used to generate a new end of sequence code of practice to improve surface quality without impacting on internal quality; in plant trials this led to the a ten-fold reduction in mill rejections. The model has since been developed to run on-line in real time and is now being incorporated into a management information system

Figure 3: Quantitative validation.

Capping off sequence(0.7m/min clear through speed)

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Soft reduction zone

ACKNOWLEDGEMENT:

The research leading to these results has received funding from the Research Programme of the Research Fund for Coal and Steel (Grant Agreement number – RFSR-CT-2009-00005)

Figure 4: The calculated change in sump shape during the proposed new cap-off practice

Page 195: 2-page abstracts booklet

Innovative New 250 / 350 mm Continuous Caster in Salzgitter Dr.-Ing. P. Müller, Dr.-Ing. M. Schäperkötter,

S. Roßius - Salzgitter Flachstahl GmbH

Dr.-Ing. M. Reifferscheid, C. Geerkens, L. Fischer, U. Kerp* - SMS Siemag AG

INTRODUCTION

Salzgitter Flachstahl GmbH operates an integrated steel plant and various flat rolling and strip processing facilities at its Salzgitter location in Germany. The production includes deep-drawing and special deep-drawing steels, structural and fine-grain steels as well as high and ultra-high-strength steels, especially for the production of heavy plates, pipes and tubes. The casting shop has four continuous casting machines, two bow-type machines with a curved mould, commissioned in 1973 and 1981 respectively, one modern single-strand vertical bending machine with a straight mould, commissioned in 2004 and one new single-strand machine, designed as a bow-type slab caster with a curved mould, commissioned in early 2010. All four slab casters were designed and supplied by SMS Siemag, Germany.

The new machine No. 4 has a main radius of 11.5 m and a containment length of 34.4 m. The slab caster produces slabs of 1,100 to 2,600 mm width in 250 and 350 mm thickness. The new slab thickness of 350 mm opened up a new market segment for the heavy plate production at Ilsenburg as well as additional flexibility in dimensional ranges with improved productivity in plate production.

The SMS order scope for the slab caster No. 4 comprised the supply of the complete casting machine with auxiliary systems including comprehensive control systems and process models. The order was handled by SMS on a turnkey basis.

EQUIPMENT DESIGN AND CONTROL SYSTEMS

Intelligent equipment and automation systems ensure a high slab quality. Examples are the hydraulically driven resonance oscillation system and the optimised online remote-controlled mould narrow face adjustment system. The strand guide system features position-controlled segments in the bow and horizontal area for fast thickness changes and dynamic strand taper adjustment. CyberLink® segments in the horizontal section perform the essential dynamic soft reduction. A special roller design ensures sufficient roller cooling even when dry casting is applied.

Above all Salzgitter uses the new casting machine No. 4 to cast steels for heavy-plate, tube and pipe

applications. Examples are micro-alloyed high-strength structural steels and pipe grades in the peritectic and medium-carbon range, API grades in the low-carbon range with HIC resistance as well as heat-treatable steels (CrMo / MnCr steels).

For casting these steel grades, the following process and design features are very important:

• Minimum level of non-metallic inclusions in the strand, i.e. clean steel practice starting in the melt shop, secondary metallurgy, followed by proper tundish and SEN design

• Low strain levels to avoid surface and internal crack ing due to bending and bulging

• Slab surface temperature > 950°C in the unbending zone to prevent surface cracking

• Control of macro-segregation and solidification struc-ture in the strand centre by optimum strand taper and soft reduction.

High internal and surface quality is promoted through the width-dependent air-mist spray cooling system, fully controlled by the Dynamic Solidification Control Model (DSC). In order to cast steel grades with crack sensitivity, the spray cooling water rates are adjusted to extremely low values. For 350 mm slab thickness even dry casting, starting already early in the bow area, is applied for the most crack-sensitive grades.

The DSC online 3D process model includes the following important functions:

• Control of the solidification process including shell growth, solidification range with solid fraction and 1st ductility trough close to and below the solidification temperature

• Control of strand taper and soft reduction

• Control of strand surface temperature based on 2nd ductility trough properties for crack-sensitive steel grades

• Calculation of maximum admissible casting speed

• System functions are fully tuned via measured strand surface temperatures and measurement of the exact position of final solidification

• Offline engineering platform with replay functions, modes for investigations of secondary cooling strategies for new steel grades, material data handling and visualization.

MACHINE DESIGN

The new casting machine No. 4 at Salzgitter was especially designed to cast steel grades that are very sensitive to internal and surface cracking. The caster design is adapted to these constraints. The main focus in minimising cracking has to be on internal

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strain during bending and unbending as well as on the slab surface temperature during unbending.

The accumulated internal strain during bending is much more critical than during unbending, i.e. the risk of internal cracking is higher in the bending zone than in the unbending zone, Figure 1. In the bow-type curved mould caster design this source of cracking is completely eliminated.

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Figure 1 - Accumulated internal strain during bending and straightening

Slab surface temperatures > 950°C during unbending eliminate the surface crack formation due to the limited material ductility of most micro-alloyed steels. Consequently, the shorter machine length from mould to unbending (absence of vertical section) of the bow-type curved mould caster design, in combination with an optimum main radius, provides the better solution for achieving this high temperature, in comparison to the vertical bending caster with straight mould design.

Figure 2 – Surface temperature depending on unbending position

As shown in Figure 2, the bow-type caster ensures 30°C higher unbending temperatures at a given casting speed compared to a vertical bending caster with a 2 m vertical section and the same machine radius. As a result, casting operation is much more flexible due to a considerably wider casting speed

window at given machine length, especially for casting slab thicknesses above 300 mm, Figure 3.

Figure 3 – Casting window for curved mould and vertical mould design, at 45 m metallurgical length

OPERATING RESULTS

Salzgitter produces around 900,000 t of demanding micro-alloyed and crack-sensitive steels per year. Before commissioning the new caster No. 4, these steel grades were cast in 250 mm thickness only on the existing bow-type curved mould machines No. 1 & 2, as well as on the new vertical bending straight mould machine No. 3. A long-term quality comparison for crack-sensitive grades - on the two caster designs, bow-type curved mould versus vertical bending straight mould - confirmed the decision to design the casting machine No. 4 as a bow-type curved mould caster.

Figure 4 – Distribution of steel grades for 350 mm slabs

Since 2010, these grades are almost completely cast on the new caster No. 4, with a share in production of around 35% in 350 mm thickness. Even including the new challenging 350 mm slab thickness, the slab quality for these steel grades has improved overall by approx. 60%, starting already from a very good quality level.

A true success story for the new bow-type curved mould slab caster No. 4 at Salzgitter Flachstahl.

Page 197: 2-page abstracts booklet

Operational results of the world’s most modern SIEMENS VAI bow type caster with vertical mold for the production of 355 mm thick

slabs for demanding quality requirements

M. Hadler (Siemens VAI Linz)

E. Reisenberger (Siemens VAI Linz)

A. Eichinger (Siemens VAI Linz)

C. Fürst (Voestalpine Linz)

H. Unter (Voestalpine Linz)

P. Hodnik (Voestalpine Linz)

INTRODUCTION

The global market for flat products with highly sophisticated requirements like, ultra high strength or sour gas resistance has increased continuously in the past decades. To achieve high strength, together with a low content of alloying elements, a high deformation ratio of the slabs in the rolling mill is required. The thicker the final flat product, the thicker the slabs are required for reaching the correct deformation ratio. High strength combined with resistance against sour gas, especially for pipeline and offshore applications, needs perfect steel cleanliness and excellent internal quality of the cast slabs. At the new caster No. 7 at voestalpine Stahl Linz (Figure 1), latest state-of-the-art technology helps to ensure the above mentioned quality.

Production capacity: 1.2 Mtpy

Thicknesses: 225 / 285 / 355 mm

Heat size: 177 t

Width range: 740 – 2200 mm

Slab weight Max. 40t

Cut length: 3.4 – 15 m

Machine radius: 10 m

Metallurgical length: 35.3 m

Max. casting speed: 2.0 m/min

Start-up: September 20, 2011

Operational Results 

For reaching the best slab quality Siemens VAI equipped the voestalpine caster No. 7 with adjustable spray nozzles (3D Sprays) and EcoStar rollers. In combination with the next generation of process automation models, such as Dynacs 3D, DynaPhase and DynaGap Soft Reduction® it is possible to reach the best surface and internal quality to fulfill the toughest quality standards for all kind of steel groups. Erreur ! Source du renvoi introuvable., the product mix cast since first heat, shows a wide range of different steel groups. Caster No. 7 has been operated, since 31st October, in 4 shifts. As of the 17th January 2012, approximately 240.000 tonnes of steel had been cast, which is approximately 17 % of the planned annual production.

With the installed 3D Sprays linked with the new Dynacs 3D calculation model it is possible to adjust the correct water amount for each cooling zone over the whole slab width. This system gives the possibility to avoid low ductility or brittle temperature zones at the slab corners. Especially for slab thicknesses over 250 mm, which the machine CC7 is able to cast, the avoidance of critical temperature ranges is a big issue. Due to this flexible adjustment of the spray nozzles it is possible to optimize the surface temperature profile according to the slab width along the relevant cooling zones. Furthermore the adjustable 3D Spray system creates a more uniform solidification profile. The more uniform the solidification front, the higher efficiency can be reached of the Dynamic Soft Reduction® [1]. An example of a simulated optimized solidification front can be seen in Figure 1. Due to Siemens VAI´s simulation tools it is possible to prepare offline the finest caster practice to achieve the perfect product quality.

a

b

Figure 1: More uniform solidification front due to optimized spray pattern and nozzle position (a) before optimization, (b) after optimization.

Page 198: 2-page abstracts booklet

In addition to a uniform solidification front the correct knowledge of solidification parameters, like the solidification temperature, heat conductivity, as far as peritectic reactions are necessary. For this reason several reference steel grades are pre-calculated with the new DynaPhase model, that ensures for a wide range of different steel chemistries a very exact prediction of those parameters. Based on this knowledge, with Dynacs 3D the accurate calculation of the final solidification point and the area of the mushy zone is ensured. As a result of these high accurate calculation models it was possible to reach the highest surface quality and internal quality levels such as centre segregation, which can be seen on a macro etched sample of a ultra high carbon steel with a carbon content of 0.75 wt - %, Figure 2.

Figure 3: Laddle shroud manipulation with LiquiRob.

The two LiquiRob’s at the CC7 take over following operations: Due to the wide range of steel chemistries for which

the casting machine CC7 is used, the behaviour during the whole solidification and cooling down range has to be known. In this case the new DynaPhase model includes also an extended database, which is able to predict the peritectic range, especially for new grades with high Al, Si and Mn content.

• Ladle area:

media/electric quick coupling, connection shroud clamping and slide gate

cylinder unlocking of ladle bolt

• Tundish area:

temperature/O2/H2 measurement & sampling tundish powder dosing shroud handling ladle lancing

CONCLUSIONS

The success of the recent thick slab caster project at voestalpine Stahl Linz is the logical result of continuous developments at Siemens VAI together with the excellent cooperation with voestalpine Stahl engineers. The installation of the slab caster No. 7 at voestalpine Stahl is setting a new benchmark in casting of high quality steels by increased operator safety.

[1] S. Ilie, R. Fuchs, K. Etzelsdorfer, C. Chimani, K. Mörwald: Slab quality improvement by soft reduction technology, ECCC, 2008.

Figure 2: Macro etches centre segregation; position: middle; material: C75, C = 0.75%C.

[2] M. Hirschmanner et.al.: LiquiRob – Improved safety and systematic procedures on the casting floor using advanced robotics, ECCC, 2011.

Finally the two equipped LiquiRobs have to be mentioned. For the first time in a steel plant, two LiquiRob industrial robot systems have been installed on a slab caster. The LiquiRobs have been installed in front of and behind the ladle turret, one in the ladle-positioning-area and the other in the ladle/tundish area on the casting platform. The LiquiRobs ensure the highest possible working place safety combined with an increase of reproducibility [2]. Figure 3 shows the ladle shroud manipulation of the LiquiRob #2 installed in front of the ladle turret.

Page 199: 2-page abstracts booklet

Session 15: Environment and by-products

Table of Contents

15.1 Metal recovery from liquid and solid waste streams generated in stainless steelcold rolling mills F. RÖGENER (VDEh-Betriebsforschungsinstitut), D. BUCHLOC (ThyssenKrupp Nirosta GmbH), A. BAN, T. REICHARDT (VDEh-Betriebsforschungsinstitut), Germany

15.2 Granulated metal product from direct tapped furnace - Experience from operation at BEFESA Sweden P. VESTERBERG, K. BESKOW, C.J. RICK (UHT Uvån Hagfors Tek), Sweden, A. RUH (Befesa), Germany

15.3

Evaluating the impact of particulate emissions from an integrated steelworks onair quality at local scale D. COURCOT (Université du Littoral Côte d’Opale), T. DESMONTS (ArcelorMittal Dunkerque), D. HLEIS, A. LIMEM, F. LEDOUX, G. DELMAIRE, G. ROUSSEL (Université du Littoral Côte d’Opale), France

15.4

A case study in utilising rainwater harvesting to reduce abstracted water in a steelproduction facility T. BALHATCHET, V. STOVIN (University of Sheffield), A. GHOSH, S. WOOLASS (Tata Steel Europe), United Kingdom

15.5

Emissions inventory of Priority Hazardous Substances and Priority Substancesfrom the Water Framework Directive in effluents from integrated steelworks in theUK J. CHEN, E. ARIES, P. COLLINS, J.S. HODGES (Tata Steel Europe), United Kingdom

15.6

The role of steel in environmentally friendly construction A.L. HETTINGER, J.S. THOMAS, D.P. BRIDOUX (ArcelorMittal Global R&D), France, O. VASSART (ArcelorMittal Global R&D), Luxembourg, V. HUET, L. GERON (CRM), Belgium, P. LE PENSE (ArcelorMittal Construction), Luxembourg A. LAVAUD (ArcelorMittal Flat Carbon Europe), France

15.7

Site-wide models to evaluate CO2 emission reduction options B. GOLS, C. TREADGOLD (Tata Steel R-D & T), The Netherlands, B. ADDERLEY (Tata Steel Group Environment), United Kingdom

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Metal recovery from liquid and solid waste streams generated in stainless steel cold rolling mills

F. Rögener (VDEH-Betriebsforschungsinstitut Düsseldorf)

A. Bán (VDEH-Betriebsforschungsinstitut Düsseldorf)

T. Reichardt (VDEH-Betriebsforschungsinstitut Düsseldorf)

D. Buchloh (ThyssenKrupp Nirosta Krefeld)

INTRODUCTION:

Shortage of important metals as well as the decreas-ing security of raw materials supply leads to rising production costs. Thus, for the stainless steel industry a significant increase of resource efficiency in all pro-duction steps is essential. Properties and quality of stainless steel are based on a defined surface finish which is gained in pickling lines. However, pickling lines generate significant amounts of waste products, such as removed metal oxide particles, metal en-riched acid solutions and metal containing neutraliza-tion sludge from waste water treatment plants. While there are different processes available to recover re-sidual acid from spent pickling solutions, the metals are still discharged. Thus, valuable metals, such as iron, chromium and nickel, are irrecoverably lost: It is estimated that every year, only in Europe more than 2.500 t of nickel with a current value of 33 million € are deposited (nickel price in July 2012: 13.000 €/t).

NICKEL CONTAINING WASTE STREAMS

Nickel can be recovered directly from spent pickling solutions or from solid neutralisation sludge (Fig. 1).

Fig. 1: Scheme of nickel recovery from waste streams

The first option requires the separation of not reacted acid to assure high process efficiency. The second option involves the leaching of nickel and is also viable for nickel recovery from landfill (“landfill mining”). Both routes lead to solutions containing dissolved metals, which are the basis for further metal recovery processes.

Nickel recovery from spent acid:

Sampling of spent acid from both, HNO3 containing and HNO3 free pickling lines over a longer period showed an average nickel concentration between 3.5 and 5 g/l. The estimated average acid concentration was about 3-3.5 mol/l. In large industrial plants, regeneration of the spent acid is state of the art. In principle, there are two technical approaches for acid regeneration and metal discharge:

1. Total regeneration of both active acid and metals in form of metal oxides. Only briquetting is required for metal recovery. This option is only used for the treatment of volume flows > 4 m³/h.

2. Partial regeneration of only the active acid – mainly with processes such as diffusion dialysis or retardation (Fig. 2). Partial regeneration processes generate metal containing acidic waste waters, which are the basis for nickel recovery.

Fig. 2: Retardation module

Nickel recovery from neutralisation sludge:

Sampling of neutralisation sludge from both, HNO3 containing and HNO3 free pickling lines over a longer period showed an average nickel concentration between 0.8 and 1.4 wt.-% based on dry matter.

For further treatment nickel has to be extracted from the sludge. Examinations have shown that H2SO4 is a favourite leaching solution for nickel. At a pH value of 1 a high but non-selective nickel leaching is possible. At a pH value of 2.7, leaching of nickel is much more

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Assuming, that the measured concentration decrease of the dissolved metals within the catholyte is only caused by electro deposition on the cathode, specific metal deposition rate and current efficiency were calculated (Fig. 5).

selective, but at the expense of a lower recovery (Fig. 3).

Fig.3: Extraction efficiency of H2SO4 for nickel at room temperature

NICKEL RECOVERY BY MEMBRANE ELECTROLYSIS:

Membrane electrolysis (ME) is a separation process involving the transport of ions in an electric field through charged membranes and the subsequent electro deposition of metals on the cathode. ME is one option to recover nickel from the acidic solution, see Fig. 4.

Figure 5: Metal deposition rate and current efficiency as a function of current density

Increasing current density led to increasing current efficiency and specific metal deposition rate. Due to Faradaic losses caused by undesired side reactions or short circuits of the system, current efficiency was about 30-50 %. In the experiments the highest metal deposition rate of about 500 g/m²h was achieved at a current density of 120 mA/cm².

Anolyte  Catholyte = 

metal containing 

Concentrate = 

regenerated 

e‐

 Anode  Cathode 

H2O 

O2 (g) 

H  

A‐ A‐ 

H  

Cation    exchange membrane 

Anion     exchange membrane 

H2 (g) 

Men  

Me (s) 

SUMMARY

The conservation of available metal resources requires the integration of separation techniques into stainless steel cold rolling lines. By recovery of metals from waste streams generated in pickling lines and the subsequent recycling into production lines highly hazardous landfill waste is avoided and natural resources can be preserved.

It could be shown that membrane electrolysis is capable to recover iron, chromium and nickel from stainless steel pickling waste waters. The electro-deposition product consisted of about 50 % iron, 5 % chromium and 5 % nickel in form of oxides and hydroxides. After rinsing the quality is sufficient for pyro metallurgical treatment.

Fig. 4: Principle of membrane electrolysis

The advantage of membrane electrolysis over conventional electrolysis is the prevention of

• anodic corrosion caused by fluoric acid and of

• an electrochemical short-circuit of the Fe(II)/Fe(III) redox system. In order to recover only nickel from liquid or solid

waste, further separation and purification steps - such as liquid-liquid extraction or precipitation - are necessary.

Thus this technology was investigated to prove its reliability for metal recovery. Preliminary investigations with 3 different synthetic solutions were conducted using structural steel substrates. Solution 1 contained only nickel, solution 2 included nickel and chromium and solution 3 included iron, chromium and nickel. It became obvious that the precipitation of elemental nickel was disturbed by the presence of iron. Instead of a thin metallic bright nickel layer, a relatively thick dark layer composed of metal hydroxides and oxides was formed.

REFERENCES:

P. Fornary, C. Abbruzzese, Hydrometallurgy 52 (1999) 209-222.

F. Rögener∗, M. Sartor, A. Bán, D. Buchloh, T. Reichardt, Resources, Conservation and Recycling 60 (2012) 72– 77

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Granulated metal product from

direct tapped furnace - experience from operation at BEFESA Sweden

Mr Vesterberg, Per (UHT Kista Sweden) Dr Beskow, Kristina (UHT Kista Sweden) Mr Rick, Carl-Johan, (UHT Kista Sweden)

Mr Ruh, Andreas (BEFESA Steel Services GmbH, Duisburg, Germany)

RECYCLING OF STAINLESS STEEL DUST

European stainless steel producers generate some 20-30 kg dust per tonne produced stainless steel. When recycling this material it is important to find a suitable product shape for users. Traditional forms of solidification of recycled material involve casting, cooling, crushing and sieving. Crushing and screening of high carbon brittle materials generates fines and dust that is problematic both at the producer and at the final product user. The metal recycling industry is a growing area for applying the GRANSHOT® granulation process for solidification. This industrial process is already proven in iron and ferroalloy applications, where it directly produces metal granules ready for handling, packaging and transport.

Fig1.Within 1 min recycled stainless steel dust, is granulated at BEFESA ScanDust, Landskrona, Sweden.

BEFESA SCANDUST OPERATIONS

The BEFESA ScanDust plant in southern Sweden, Landskrona has an output of 30,000 tonnes of recovered metal per year, Fig 1. This plant features,

since 2003, direct tapping of the hot metal from the plasma shaft reduction furnace to the GRANSHOT® granulation unit, Fig 2.

Fig 2.Hot liquid metal directly enters the granulation tundish.

Granulation at ScanDust is made at a rate of 1.5 tonnes/min, Table 1. After the dewatering and drying operation, the metal granules exit the unit within 1 minute. The final product is transported to a storage silo and packed for transport, ready for shipment back to the stainless steel plant from where the dust originated or it is to be sold on the open market [1].

Table 1. Data for GRANSHOT® unit at BEFESA ScanDust.

Plant design capacity ~ 144 tonnes/day

Granulation rate 1.5 tonnes/min

Heat size 12 tonnes

Water cooling capacity 4 MW

GRANSHOT® METAL GRANULATION

The granulation process is a method for rapid solidification of metals in water. The process is based on the heat exchange between the liquid hot metal and cooling water.

The hot liquid metal is tapped into a preheated tundish and from the tundish the hot metal hits a spray-head of refractory material, placed in the centre over the granulation tank. The spray-head splits the metal stream into droplets that are evenly distributed over the tank water surface, Fig 3. The hot metal solidifies partly in-flight before penetrating the water surface. Further cooling takes place as the granules sink downwards in the granulation water tank transferring heat to the counter flowing cooling water.

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Granules for Simplified Logistics

The main fraction lies in the size range between 5-25 mm with a typical deformed spherical shape, having a bulk density over 3.5 tonnes/m3. The size distribution of the granules will vary slightly with metal composition, hot metal temperature and granulation rate. The granule size, weight and shape make the product excellent for bulk handling. It can easily be handled by conveyor belts, vibrating feeders, magnet, baskets and front-end loader, Fig 4. The free flow properties also make it suitable for silo storage and as a continuous process addition, for example through the 5th hole of the EAF.

Fig 3.In the GRANSHOT® process the hot liquid metal hits a refractory target and the drops are cooled by water.

The solidified granules, at T< 100oC, are discharged from the lower end of the tank by an air and water ejector on to a dewatering screen, Fig 1. The solution with spray-head and ejector allows for an industrial high capacity operation, currently up to 300 tonnes/hr. After dewatering the metal granules can if requested, as at BEFESA, be further dried in a rotary dryer.

There are several GRANSHOT® implementations in the recycling industry but the majority is for ferroalloys, as for ERAMET Doniambo, BHP-Billiton, SNNC, VALE and AngloAmerian, XSTRATA. There are also pig iron being granulated at ArcelorMittal Saldanha, SSAB, Voestalpine and ESSAR Steel.

Fig 4.Granulated recycled stainless steel dust being packed.

Ideal Metallurgical Properties

The granules are free from oxides and slag, also inert while heated. The high specific surface area results in good preheating properties, quick melting and dissolution when added into a liquid melt. This is combined with a high density that enables the granules to penetrate the slag layer.

RESULTS AT BEFESA

The final composition of granulated stainless steel process dust is determined by the ingoing raw materials, a typical composition is shown in Table 2.

Table 2. Typical composition of granulated material.

Fe C Cr Ni Mo Si Weight

% 55–65 4–6 15–20 3–10 0.5– 3

0.2– 0.5

SUMMARY

BEFESA ScanDust has by applying direct tapping and GRANSHOT® metal granulation as solidification of the recycled stainless steel dust achieved several important results in their operation. Rapid & Safe Operation • Safe and industrial process, with high solidification

capacity, 90 t/hr and solutions up to 300 t/hr exists. Granulation and drying of granules take 1 minute as compared to the earlier casting, cooling, crushing and handling operations, which were also hazardous to the staff.

• Close to 100% metallic yield and almost no fines.

• 30% cost reduction by direct tapping from the furnace and the use of granulation process. Close to 100% Metallic Yield

By granulating the recycled stainless steel dust, close to 100% metallic yield and almost no fines is achieved in the solidification. This is appreciated by BEFESA and the end-users of the granulated material.

• Metal granules have ideal logistical properties for producer, transporter and the end-users.

• The shape and absence of moisture, slag and oxides makes metal granules well suited in any downstream metallurgical process. 30% Cost Reduction

Direct tapping to the GRANSHOT® unit and the simple handling of the granules have reduced the cost at BEFESA ScanDust with some 30% as compared to the earlier casting in moulds, crushing and the extensive material handling that was necessary.

REFERENCES

[1] Beskow K, et al, The sustainability of valuable metals – recycling of residues from stainless steel production, Baosteel BAC 2010 conference, China.

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Evaluating the impact of particulate emissions from an integrated steelworks on air

quality at local scale

D.Courcot 1(Université du Littoral Côte d’Opale)

T. Desmonts (ArcelorMittal, Dunkerque)

D. Hleis1, A. Limem2, F. Ledoux1, G. Delmaire2,

G. Roussel2 (Université du Littoral Côte d’Opale) 1. Unité de Chimie Environnementale et Interactions sur le Vivant

- Dunkerque - http://www-uceivfr.univ-littoral.fr

2. Laboratoire d’Informatique Signal Image de la Côte d’Opale - Calais - http://www-lisic.univ-littoral.fr

ABSTRACT

The source identification process is an important step in air quality management. This work presents a new receptor model, based on Non Negative Matrix Factorization (NMF) method, which has been developed for particulate matter (PM) source identification. The main advantage of this tool is to take into account constraints on the source profiles. Input constraints consist in considering the a priori knowledge on the source profile resulting from chemical analysis of samples from industrial sources in the calculation procedure. The objectives of using such model in atmospheric particles studies is to access on the sources profiles influencing the composition of PM samples as well as to quantify the contribution of each identified source influencing the atmospheric PM level.

INTRODUCTION

Receptor modelling offers a method to complete the atmospheric particulate source identification using ambient concentrations as inputs and calculating source contributions. One type of receptor model is the multivariate model as the Positive matrix factorization (PMF) initially developed by Paatero. Using a least squares approach, PMF solves the problem in factor analysis by integrating positivity constraints into the optimization process and using the error estimates for each data value as point-by-point weights. PMF has been used world wide in the analysis of receptor modelling, and successfully applied. Nevertheless, the PMF commercial version does not allow to control the initialisation of the model and to bring extra information on the source to bring the calculation around to the best result.

In this context, our choice was to develop a new method for source identification and contribution based on the Non Negative Matrix Factorization (NMF) method. The main advantage of the NMF is that algorithms are easily available and implementation is possible. This model was then developed introducing constraints in order to be able to take into account an a priori knowledge of the chemical composition of emission sources. The objectives of using such model in atmospheric particles studies is to access on the sources profiles influencing the composition of ambient particle samples as well as to quantify the contribution of each identified source, arising from either industrial or non industrial emissions.

METHODS

The weighted non negative Matrix Factorization used with constraints

The matrix factorization model can be written as X = GF + E, where X is the known n x m matrix of the m measured chemical species in n samples. G is an n x p matrix of source contributions to the samples. F is a p x m matrix of source compositions (source profiles). Both G and F are factor matrices to be determined. E is defined as a residual matrix, i.e., the difference between the measurement X and the model Y as a function of factors G and F. Furthermore, NMF constrains all of the elements of G and F to be non negative, meaning that sources can not have negative species concentration and sample can not have negative source contribution. This NMF version is also weighted by the uncertainty associated with the measurement of chemical species concentrations [1]. Finally, constraints are applied while taking in consideration our knowledge on the source chemical composition.

Sampling and chemical analysis of ambient airborne particles [2]

This method has been validated considering airborne particulates (PM10) samples collected in Dunkerque (52°02’N, 02°20’E) located at the northern coast of France. Particulate emissions from the ArcelorMittal integrated steelworks were also analyzed to get their characteristics. Confined and fugitive emissions from the sintering unit were considered as well as dust emissions from blast furnace and steel making processes. Ambient airborne particulates and industrial samples were analyzed for water soluble inorganic ions (Cl-, NO3

-, SO42- and NH4

+) and metal (Al, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, S, Ti, V and Zn) contents using ion chromatography and inductively coupled plasma emission spectroscopy, respectively. These data are then used as inputs for modelling calculations.

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RESULTS

Source apportionment

The first step in this work was to clearly identify the background source profiles. Thus, first runs of the model were only performed on samples without expected industrial contribution. The choice of such samples was based on the local meteorological wind conditions occurring during the sampling time. The results evidenced that background is make up of 4 sources: secondary inorganic aerosols (traced by SO4

2-/NO3-/NH4+), sea salts (Cl-/Na/Mg/SO4

2-/K), secondary sea salts (Na/NO3

-/SO42-/Cl-/Mg/K) and

resuspended crustal dust (Al/Ca/Fe/K/Ti). These four sources profiles were considered to have constant composition in the further calculation.

Figure 2: Temporal variation of total inorganic concentration of aerosols. Histograms show both industrial and non-industrial contr butions from NMF results. The insert gives the correlation between measured and calculated concentrations.

The contributions of the different local industrial sources are also evidenced. This contribution is about 17% of the total particulate charge and among the industrial sources; the sintering unit shows the higher contribution (Fig. 3). It is interesting to notice that these results have provided for the first time an evaluation of the impact of fugitive emissions versus confined emissions in the ambient air at a local scale.

In a second step, all the collected samples were taken into account as well as the knowledge on the composition of the particles collected in both the different units of the integrated steelworks ArcelorMittal Dunkerque and in a Fe-Mn alloys plant. Chemical composition data of these particles were used to first initialize the model and also to direct the source profiles. Each source could be identified from the relative abundance of specific elements that could be used as tracers. Figure 1 illustrates the 9 sources profiles identified after optimized calculation: Blast furnace/steelmaking (profile p 5), slags (p 6), sintering fugitive emission (p 7), emission from the sintering stack (p 8), Fe-Mn alloys (p 9), and the four constant fixed non industrial profiles: secondary inorganic aerosols (p1), sea salts (p 4), secondary sea salts (p 3), crustal dust (p 2).

Figure 1: Source profiles obtained by weighted NMF with constrains. See text for attribution.

Contributions calculated by the model of each source identified on PM10 samples collected between February 2008 and May 2008 in Dunkerque are given in Figure 2. Results show that the major contributors to airborne particulates ambient concentrations were non-industrial sources (counting for about 83% of the total particle charge). It was found that the mean contribution of the secondary inorganic aerosols and sea salts were 44% and 36% respectively.

Figure 3: Temporal variation of industrial source contribution to ambient PM10 level.

For instance, whereas the emission factor by the sintering stack is well known, fugitive emissions from this sector can not be easily determined. From NMF results, it has been evaluated that the sintering stack and fugitive emissions from the sintering unit had practically the same impact in ambient air at local scale. To conclude, this approach proved that conducting a source apportionment study, using matrix factorization, is more reliable when coupled with a previously acquired knowledge on source profiles. The model developed is specifically capable of distinguishing between many sources of particulate matter within an industrial complex. [1] Une version pondérée de la Factorisation Matricielle Non négative pour l'identification de sources de poussières. Application au littoral de la Mer du Nord. G. Delmaire, G. Roussel, D. Hleis, F. Ledoux. RS-JESA, N° 4-5, vol 44 / 2010, pp 547-566.

[2] Evaluation de la contribution d'émissions sidérurgiques à la teneur en particules en suspension dans l'atmosphère à une échelle locale. D. Hleis, Thesis, Université du Littoral Côte d'Opale, 2010.

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A Case Study in Utilising Rainwater Harvesting in a Steel Production Facility Speaker – Tim Balhatchet (PhD Student, University of Sheffield), Authors – Tim Balhatchet, Virginia Stovin (Supervisor, Civils Dept, University of Sheffield),

Ankur Ghosh (Tata Steel Europe, Energy Optimisation, Strip Products UK) Steven Woolass (Tata Steel Europe , Group Environment,),

An integrated steel plant typically consumes very large quantities of water; in

addition to supply issues, the energy demands associated with water treatment and supply are not insignificant. Measures to improve water efficiency in steel production are required due to increasing pressure resulting from global water shortages. This case study explores the potential of using harvested rainwater to replace existing (more energy intensive) water sources.

At the Port Talbot steelworks (Wales, UK) different water sources sum to a large amount: 20-30% of which is freshwater and 70-80% of which is brackish seawater. Water is used for various cooling, quenching and process applications. In order to reduce freshwater abstraction from natural sources, alternative and freely available sources are being considered. As Wales is one of the wettest places in the UK in terms of rainfall (with Port Talbot on average receiving around 1000 – 1100mm of rainfall per year) rainwater harvesting has the potential to be one of these sources. If all the large roofs of the mills and plants are used as collectors, it is possible to collect in the order of 400,000 m3 per year. If the rainwater falling within the entire site boundary is collected, then about ten times that is available.

This is a substantial quantity, but is not a solution by itself to displace the fresh water consumed by the works, meeting only 7.5 % of freshwater use. It will need to be part of an overall scheme including efficiency measures, significant water reuse and other sources of supply.

A pilot scheme has been proposed at one building on the site: the sinter plant, where it is expected that collected rainwater could reduce the existing water consumption for the sinter plant by about 10 %. This scheme will be used to understand implementation and water quality issues, and work as a proof of concept for integrating rainwater harvesting with industrial processes. Monitoring the water quality will yield information on how and where it can best be used in site processes.

This scheme will help to inform and develop proposals to introduce rainwater harvesting on a larger scale around the works.

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1. INTRODUCTION The European Water Framework Directive (WFD) lists several priority substances (PS) and priority hazardous substances (PHS) that are deemed to present a significant risk to the aquatic environment [1]. To support the WFD, the Environmental Quality Standards Directive [2] sets maximum short-term concentrations and annual average values for PS and PHS. The chemical status of surface waters will be determined by compliance with these environmental quality standards (EQS). Within this list, several polycyclic aromatic hydrocarbons (PAHs) including benzo[a]pyrene and some trace metals, such as Hg and Cd, have been identified as being of relevance to the steel industry.

Accordingly, a study was undertaken by Tata Steel Europe to characterise the emissions of PHS and PS from cokemaking and steelmaking operations. First, work was carried out to develop analytical methods for the measurement at trace levels of PAHs and trace metals in wastewater effluents. Over the period 2010-2011, effluent emissions monitoring campaigns were carried out at Tata Steel Plant B, a major integrated steelworks located in the UK. This work led to obtain a robust emissions inventory for the steelworks and to determine emissions factors for the WFD substances, as well as establishment of the main sources of PHS/PS. The research leading to these results has received funding from the European Community's Research Fund for Coal and Steel (RFCS) under grant agreement (ECOWATER-RFCR-CT-2010-00010: Enhanced Treatment of Coke Oven Plant Wastewater).

2. MATERIALS AND METHODS 2.1 Tata Steel Plant B Tata Steel Plant B has a production capacity of ca. 4 million tonnes of liquid steel (LS) per annum. There is only one effluent discharge which is composed of treated coke oven effluent, drainage from the site, storm water, effluents from continuous casting and cold rolling, effluents from the BOS gas cleaning system and from the blast furnace (BF) blowdown, process water from secondary steelmaking (degasser). The combined effluent is directly

discharged to the sea. Monthly effluent samples were collected in 2010 and 2011, and analysed for PAHs and trace metals.

Emissions inventory of Priority Hazardous Substances and

Priority Substances from the Water Framework Directive in

effluents from integrated steelworks, UK

J. Chen, E. Aries, P. Collins, J. Hodges (Tata Steel Europe, Group Environment, Swinden

Technology Centre, UK)

2.2 PAH analysis Waste water from steelmaking and cokemaking operations may contain PAHs that are present both in the dissolved phase and suspended particulate matter. Accordingly, a versatile method was developed to analyse the total (i.e. dissolved + particle-bound PAHs) concentrations of PAHs in the effluents. Briefly, effluent samples were filtered to remove the suspended particulate matter. The filtrate was extracted using solid phase extraction (SPE). For the SPE step, reverse phase SPE was employed using a cartridge packed with a sorbent containing non-polar functional groups such as octadecyl (C18). The filters and residues from the filtration were extracted using accelerated solvent extraction (ASE) to extract the PAHs bound to the suspended solids. At this stage, both extracts were either combined and analysed by gas chromatography - mass spectrometry (GC-MS) to determine the total PAH concentration in the samples or analysed separately if necessary. Quantification was achieved using a set of surrogate, internal and recovery deuterated PAH standards. 2.2 Trace metal analysis An analytical method using ICP-MS was developed for the determination of trace metals in steelmaking effluents. All samples were analysed for the dissolved and the total concentrations of metals in the effluents. The analytical procedures developed were used to monitor the following elements: Fe, Ni, Zn, As, Cd, Cr and Pb. For determination of the dissolved concentration of trace metals, samples were filtered through a 0.45 um pore diameter membrane filter, pre-digested on a hotplate/hotblock using nitric acid at 90ºC during 30 min, and digested with nitric acid using a microwave instrument. For determination of the total concentration of trace metals, water samples were pre-digested without filtration. All samples were analysed using an Agilent 7500cx inductively coupled plasma - mass spectrometer (ICP-MS) equipped with an Octopole Reaction System.

For Hg determinations, cold vapour atomic fluorescence spectrometry (CVAF) was used as it is more sensitive than ICP-MS and exhibits good linearity over a large concentration range. 3. RESULTS AND DISCUSSIONS 3.1 Annual mass releases and emission factors of PAHs and trace metals at Tata Steel Plant B The PAH and trace metal data obtained in 2010/2011 were used to calculate annual mass releases. For calculations, monthly flow rates of the discharge point were combined with PAH and trace metals concentrations in order to determine annual mass releases, expressed in kg / annum. Emission factors, expressed in mg / tonne LS, were calculated using the

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annual steel production of Tata Steel Plant B. The results are summarised in Table 1.

BF Effluent BOS Effluent Cokemaking EffluentOld Cokemaking Drain ConcastHot Mill Effluent

Con Annealing EffluentCold Mill EffluentDeep DrainDegasserBOS Stormwater

97.5 %0.5 %

1.2 %

0.3 %

Table.1 Annual mass releases and associated emission factors of PAH and trace metal from the effluent discharge point at Tata Steel Plant B in 2010 and 2011.

Annual mass releases (kg/annum)

Emission factors (mg/tonne LS)

2011 2010 2011 2010

Anthracene PHS 6.8 1.4 1.8 0.33 Benzo [b + j] fluoranthene PHS 57.8 89.7 15.5 21.7

Benzo [k] fluoranthene PHS 19.7 26.9 5.3 6.5

Benzo [a] pyrene PHS 35.8 46.2 9.6 11.2

Indeno [1,2,3-cd] pyrene PHS 24. 5 30.5 6.6 7.4

Benzo [g,h,i] perylene PHS 30.3 35.4 8.2 8.6

Naphthalene PS 30.7 12.5 8.3 3.0

Fluoranthene PS 73.2 37.7 19.7 9.13

PAH

s

Total 16 US EPA PAHs 480

Fig.1 Percent contr bution of each wastewater feeding stream to the total PAH emission in 2011 at Tata Steel Plant B. As may be seen from Fig. 1, cokemaking effluents originating from the biological effluent treatment (BET) plant was the most significant PAH emission source contributing approximately 97.5%, while BF effluents only contributed 1.2% to the total PAH emissions.

0

10

20

30

40

50

60

70

80

90

100

Cd Pb Ni Cr Fe Cu Zn As

Con

trib

utio

n %

of e

ach

was

tew

ater

str

eam

BOS Stormwater

Degasser

Deep Drain

Cold Mill Effluent

Con AnnealingEffluentHot Mill Effluent

Concast

Old CokemakingDrain CokemakingEffluentBOS Effluent

BF Effluent

425 129 103

Cd PHS 21.2 25.1 5.7 6.1

Hg (Dissolved) PHS 1.5 1.3 0.4 0.3 Pb PS 1097 1196 295 290

Ni PS 223 157 59.9 38.1

Cr SP 423 145 114 35.1

Fe SP 195591 125702 52595 30459

Cu SP 326 221 87.8 53.4

Zn SP 56434 43498 15175 10540

Tota

l Tra

ce m

etal

s

As SP 77 49.9 20.7 12.1 Fig.2 Percent contr bution of each wastewater feeding stream to the total metal emissions in 2011 at Tata Steel Plant B Fig. 2 shows that Cd, Cr and Cu were mostly emitted from the BOS stormwater stream. Process water from BF appeared to be the most significant emission source of Pb and Fe. More than 30% of Ni originated from the hot mill process waste water and 20% from BF effluents. A significant proportion (50%) of Zn originated from the degasser wastewater stream. Arsenic was emitted from a variety of sources, albeit a very small amount in total.

As may be seen from Table 1, total PAH annual mass releases of Tata Steel Plant B ranged from 425 to 480 kg / annum between 2010 and 2011. PAH emission factors ranged from 103 mg / tonne LS in 2010 to 129 mg / tonne LS in 2011. The most significant trace metal releases at Tata Steel Plant B were Fe and Zn. Among the metals identified as PHS and PS in the WFD, Pb exhibited the most significant total annual mass release (ca. 1100 kg / annum), followed by Ni and Cd. Hg emissions were very low (ca. <1.5 kg / annum) both in 2010 and 2011. There was no significant difference between the total Cd and Pb releases in 2010 / 2011.

4. CONCLUSIONS Throughout 2010 and 2011, extensive monitoring campaigns were carried out to build a robust emissions inventory of PHS/PS identified in the WFD in effluents from a major integrated steelworks in the UK. This work led to identify the most significant process emission sources for each substance. Further work will be carried out to study in more detail the variability of PAH and trace metal emissions.

3.2 Emission sources of PAHs and trace metals at Tata Steel Plant B Although there is only one effluent discharge at Tata Steel Plant B, in total, 11 wastewater streams contribute to the combined discharge. Further work was carried out to establish the sources of PHS/PS and their significance. The contribution of each source to the total emissions for PAHs and eight metals were plotted for the year 2011, as depicted in Fig. 1 & 2.

5. REFERENCES 1. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. 2. Directive 2008/105/EC of European Parliament and of the Council on environmental quality standards in the field of water policy.

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The role of steel in environmentally friendly construction

Anne-Laure Hettinger, Jean Sébastien Thomas, Didier Bridoux, Olivier Vassart 1

André Lavaud 2 Patrick Le Pense 3

Laurent Géron ,Valérie Huet 4

1 ArcelorMittal Global Research and Development R&D 2 ArcelorMittal Flat Carbon Europe Roofing and Cladding 3 ArcelorMittal Construction Design & Engineering Office 4 AC&CS – CRM Group

Introduction: The construction market counts for more than one third of the worldwide energy consumption and 40% of the carbon dioxide emission. To develop environment-friendly constructions, it is crucial in particular to manage resources scarcity, to avoid the generation of wastes and to reduce the impacts on climate change (1, 2, 3). Thanks to its recognized valuable properties, steel is the material of choice to address these major issues for the following reasons:

- The mechanical properties of steel reduce the weight necessary to bear high loads and therefore decrease the quantity of material required to fulfil constructive functions in buildings (bearing structure, envelope,…) - Steel components exhibits a very favourable eco efficiency for main building functions (structure, energy efficiency,..) - Steel is easily recovered thanks to its magnetic properties, increasing the recycling rate at the end of life. This recycling is done without loss of quality, this is why the recycling of steel avoids the need of virgin materials The case studies developed below demonstrate the environmental benefits and value of steel thanks to the use of LCA expertise and LCA softwares (AMeco and LicaB ) These softwares are specifically developed by ArcelorMittal for addressing the challenges of sustainable construction.

I Virgin material savings and Structural optimization ArcelorMittal high strength steel grades (HISTAR®) are developed for rolled shapes dedicated to structural application. Using HISTAR® makes it possible to achieve lighter structures which reduces carbon footprint up to 30% in steel columns and 20 % in beams. HISTAR® was chosen for the structural frame of the famous “Diamond of Istanbul” leading to a 25 % saving of CO2 emissions compared to S235 steel as

evaluated by our AMeco software4. The 50 000 tons of HISTAR® produced each year by ArcelorMittal represents a saving of 14000 tons of CO2, which is approximately the annual emissions of 4000 cars .

II Improved Environmental footprint of office buildings using steel sunshades: A typical small office building of 100 m2 located in Montpellier is studied using LicaB LicaB is a home made software specifically developed by ArcelorMittal to make a Life Cycle Assessment (LCA) on a whole building. LicaB consists in a building modelling module, a dynamic or static simulation completed by a full LCA calculation. The LCA calculation is performed according to the EN 15978 standard using official databases including the official Worldsteel Life Cycle Inventory database5

The studied office building is equipped with a typical vertical sunshade made of perforated coated steel (46 % perforation – R10 T14) with a life time of 30 years. Using sunshades is a very efficient way to improve drastically the environmental footprint of the commercial building with a demonstrated 28% GWP and 16% Primary Energy savings on the whole life of the building.

32

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Fig 1: Steel Sunshade effect on Global Warning Potential

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III Competitive solutions for mastering the environmental footprint of residential housing: The test case covers a single residential housing of 220 m². It includes several apartments and is typical of social housings in Eastern Europe (Romania) The house is made of a light galvanized steel frame structure and has a life span of 60 years. The “Casa Buna” housing concept is to offer an affordable and energy efficient residential housing during its entire life cycle (Production, Usage and End of life). With a GWP of 317 kgCO2eq/m² of net floor area (much lower than French Ademe6 440 kgCO2/m² ) and a primary energy demand for heating of 69kWh/m2.yr, the Casa Bunã Steel house is rated at the best level achievable of the local national thermal regulation. The LicaB study shows that in term of global environmental impact on the climate change (GWP and Primary Energy), the light steel frame steel solution is really competitive compared with the traditional materials. The LCA study concludes a similar impact on the whole life of the building and an identified advantage of a lighter weight and use of a lower quantity of materials (172 tons versus 268 tons) for the steel solution.

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Fig 3: Bill of materials Casa Buna house

At the end-of-life of a building, steel elements can be easily recovered and recycled. Recycling of the steel elements in the Casa Buna building avoids around 16 tons of CO2 equivalent emissions7.

IV Valuable reflective coatings for roofing to improve the Environmental footprint of Buildings: ArcelorMittal regularly develops new environmental friendly products dedicated to the construction market. Thanks to their high reflectance, Granite® Comfort a new organic coated product, and Aluzinc® a specific metallic coating greatly improve the thermal comfort of buildings in sunny days: - they reflect considerably more sunlight - they emit more absorbed radiation back into the atmosphere - they absorb less heat than current steel material and even less than most competing materials On a ventilated building , it helps reducing the inside summer comfort temperature On an air conditioned building, it is demonstrated up to a 15% savings on the energy bill. Tested on the roof of an office building located in

Seville Spain (One storey 20 offices) it makes it possible to save 1 560 kWh per year, leading to a global CO2eq emission reduction of 35 tons of CO2eq over a 50 years usage of the building, improving its environmental footprint. Figure 4 below illustrates the cumulative savings of GWP and PED generated by the use of reflective coatings.

Cumulative benefit of the radiative paint over time

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Fig 4: Steel roof with high reflectance coating - PED and GPW savings during the life of the building.

The amount of greenhouse gas avoided is equivalent to the emissions of an average European car during its whole life (well to wheels emissions during its use phase8)

-36% V Conclusions: With a set of different case studies, the article has demonstrated that steel, through its construction products, components and solutions, is a material of choice to address resources scarcity, to reduce wastes as well as the impacts on climate change. As such, it fully contributes to the development of a sustainable world. Référence: 1 Ministère de l’Écologie, du Développement Durable et de l'Énergie - Les émissions de gaz à effet de serre par secteur en France - Le secteur résidentiel-tertiaire représente 19,1 % des émissions de gaz à effet de serre – 2011 2 FFB et Ademe – Mieux gérer ses déchets de chantier de bâtiment – 38.2 millions de tonnes de déchets par an –2008 3 World Business Council for Sustainable Development WBCSD) Energy Efficiency in Buildings Project -Facts & Trends – 2009 4 AMeco software4 -free at ww.arcelormittal.com/sections 5 Steel Life Cycle Inventory database Worldsteel association –www.wordsteel.org 6 Ademe publications – « Bâtiment: Energie Environnement » Collections Chiffres Clés 2010 7 Worldsteel Association – “Life cycle assessment methodology report” 2011 8 A. Carvallo, “Life Cycle Assessment in the Automotive Sector: a review” 2010

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Site-wide models to evaluate CO2

emission reduction options

B. Gols (Tata Steel RD&T)

B. Adderley (Tata Steel Environment)

C. Treadgold (Tata Steel RD&T)

INTRODUCTION:

Tata Steel promotes corporate citizenship. One of the pillars of corporate citizenship is respect for the environment. For Tata Steel this means playing an active and constructive role in addressing climate change and reducing its own carbon footprint. Tata Steel has set itself the target to reduce carbon dioxide emissions by at least 20% by 2020 compared to 1990 levels.

The European emission trading system (EU-ETS) requires a proper administration of the current carbon dioxide emissions. The economic incentive from the cost for carbon dioxide emissions according to the EU-ETS is embedded in the economic plant models.

Why a Site-wide model?

To predict the impact of future process changes on the carbon dioxide emissions can be complex especially when alternative scopes and boundaries are considered.

Emissions for plant or site level can be very different due to internal streams of process gas, steam, oxygen, heat, etc. In the EU-ETS scope these differences can be huge because the EU-ETS scope only looks at carbon entering from outside the fence and does not consider any intermediate streams.

Worldsteel has created a scope including indirect emissions. Indirect emissions of a stream are the emissions of an upstream installation to make this stream. Worldsteel has generated a list of nominal indirect emissions for most common intermediate streams on an integrated steel site. When indirect emissions are taken into account the differences between site or plant level calculations should be smaller than in the EU-ETS scope, but still not the same.

To make site and plant level carbon dioxide calculations the same the real plant indirect emissions need to be taken along. This requires an integration of various plant models along the site in one integrated site-wide model.

SITE-WIDE MODEL SETUP:

A site-wide model was developed in IRMA. IRMA is in-house developed flowsheeting software based on the Factsage thermodynamic databases. The first IRMA versions originate from ULCOS process comparison work. IRMA is well suited to develop process models and ensure that energy, mass and element balances are closed

Process model included in the site-wide model

The site-wide model consists of a set of integrated existing and new models. The models for the blast furnace and the basic oxygen steelmaking plant are existing heat and mass balance models developed within Tata Steel over years. The models for the sinter plant, the coke plant and the coal plant are based on the actual plant lay-out and available plant data combined with knowledge and literature of the actual process steps. The models for the boiler and power plant are based on fixed average conversion efficiencies taken from actual site data. Casting, rolling, milling, etc is combined in one downstream process with requirements per ton product based on actual plant data.

Connections and streams in the site-wide model

Figure 1 Site-Wide model elements and boundary

An overview of all process models and the major streams between the process models, included in the site wide model is given in Figure 1. The major solid streams in the model are the ferrous and carbon streams. In the model the sinter plant and coke plant production is fixed. Additional coke and pellets are purchased to fill any gaps between the required amount and the production.

Process gas is used around the site to fulfil heat requirements for the blast furnace stoves, the boilers and the reheat furnaces. The process gas network is simplified. The requirements are only set in the amount of giga joules required, any constraints on the calorific value of the gas are neglected. Any additional gas requirements are filled in with natural gas.

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Solver Conditions

The site-wide model converges on a set of defined conditions using an iterative algorithm. These conditions mimic the actual decisions made during plant operation. An example of one of the conditions used in the model is shown in Figure 2. In this example the slag basicity is controlled by adjusting the limestone addition to the sinter.

This also requires additional conditions in the sinter plant. In the sinter plant the output is fixed. This means the amount of ore in the sinter needs to be adjusted to compensate for the change in lime content. Limestone also requires energy to convert to lime. This means the amount of breeze in the sinter mix needs to be adjusted to fix the sinter outlet temperature. And additional breeze needs additional oxygen to combust, so the air inlet is adjusted to keep the flue gas oxygen content constant.

SlagBF

Sinter

Slag Basicity

Lime Stone

BasicitySetpoint

Sinter

Figure 2 Example condition fix basicity with sinter lime

Blast furnace heat and mass balance model

The heat and mass balance model of the blast furnace takes a key role in the site-wide model. This model determines the blast furnace productivity based on the chosen operating conditions and raw materials and requests the required streams from the upstream installations. In this way the blast furnace model sets the setpoints for the amount of injection coal, coke, hot blast and pellet.

RESULTS:

During the evaluation of ideas to reduce carbon dioxide emission three major effects were observed deciding the outcome of most of the calculated options. These are production increase, coal replacement with gas and the raw materials.

Production increase

Although a production increase in itself has no strong effect on the carbon dioxide emissions per tonne of product, a production increase in the model does lower the carbon dioxide emissions. The reason for this is in the conditions set for the model. Any additional production is made with purchased pellets.

Purchased pellets result in no emission in the EU-ETS scope and have a lower indirect emission than the sinter plant emission in the Worldsteel scope. This means a higher pellet/sinter ratio results in a reduction in carbon dioxide emissions

Coal replacement with gas

The energy requirement for steelmaking can be filled in with different sources although a certain amount of needs to be fixed carbon due to the nature of the process. Filling in the energy requirement with (natural) gas instead of coal results in a lower carbon dioxide emission because the amount of carbon per giga joule for gas is half the amount of carbon per giga joule in coal.

Raw materials

Different types of coal and ore have different properties like the amount of carbon per giga joule, the amount of ash and the composition of ash. The quantity of coal and ore used is large. This means changes in the properties, especially of coal, have a large effect on the carbon dioxide emission.

Examples of carbon dioxide options calculated and their effects

The site-wide model has been used to calculate a set of options for carbon dioxide emission reduction with an influence on multiple plants on the site. Some examples are:

Pre-reduced burden in Blast Furnace

An additional installation is added to the site to pre-reduce burden with coke oven gas or natural gas. The pre-reduced burden is charged to the blast furnace. This option reduces carbon dioxide emission by replacing part of the coal requirement in the blast furnace by gas requirement in the pre-reduction step and by increasing productivity of the blast furnace.

Coal injection increase

Increasing the coal injection reduces the carbon dioxide emissions by increasing the blast furnace productivity and by replacing coke by coal. The last condition is difficult to model because first purchased coke is replaced, which only has an indirect emission in the Worldsteel scope.

CONCLUSIONS:

The site-wide model calculates the impact on carbon dioxide emission in various scopes on site and plant level including a simple raw material cost estimation with detailed breakdowns of the carbon dioxide and price per stream. This enables the comparison and evaluation of multiple options on a common basis.

The combination of the actual site configuration and conditions makes this a powerful tool to evaluate site options. The results are configuration specific and show the influences on all plants which are hard to predict without a site-wide model.

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Session 16: Cold rolling

Table of Contents

16.1 Modernization of the four-stand tandem cold mill BILSTEIN GmbH & Co KG. Highperformance rolling of special steel grades in medium wide format K. HOEN, C. SCHWARZ, A. WELLER (SMS Siemag AG), G. ZWICKEL (BILSTEIN GmbH & Co KG), Germany

16.2 First results of a recently installed minimum quantity lubrication system on atandem cold mill K. KRIMPELSTÄTTER (Siemens VAI Metals Technologies GmbH), Austria,A. FLAXA (Quaker Chemical Europe), The Netherlands

16.3

Evaluation of tool material Vancron 40 with regard to wear, surface quality andgalling M. TAHIR (University of Dalarna), N.G. JONSSON (Jernkontoret), J. LAGERGREN (Åkers), J.O. WIKSTRÖM (AB Sandvik Materials Technology), H. HEDENLUND (Outokumpu AB), Sweden

16.4

Novel method for setting the mechanical and topographic properties of stripswithin one process step V. DIEGELMANN (VDEh-Betriebsforschungsinstitut), G. ZWICKEL, M. ULLRICH (Bilstein GmbH), Germany, H. GOUVEIA (Instituto de Soldadura e Qualidade), Portugal, U. WEIRAUCH (Andritz-Sundwig GmbH), Germany, A.V. PERNIA ESPINOZA (Universidad de la Rioja), Spain

16.5

TopPlanHybrid: A new hybrid online measurement system for measurement ofsurface shape of rolled strips with arbitrary reflection characteristics H. KRAMBEER, M. FELDGES, U. MÜLLER (VDEh-Betriebsforschungsinstitut), R. FACKERT (IMS Messsysteme GmbH), W. GERLACH (ThyssenKrupp Nirosta GmbH), Germany

16.6

Integrated thickness and flatness control for Sendzimir mills J. POLZER, A. WOLF (VDEh-Betriebsforschungsinstitut), M. JELALI (Köln University of Applied Sciences), M. TRUSKOWSKI (ThyssenKrupp Nirosta AG), R. FACKERT, T. HERMEY (IMS MessSysteme GmbH), Germany

16.7

Major improvements of the Skin-Pass 48'' at ArcelorMittal Florange X. BREUVAL, J. JOSSET (ArcelorMittal Florange), P. ROBLIN, F. BAUDEL, G. MUZARD (GE Energy Power Conversion), France

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Modernization of the four-stand tandem cold mill Bilstein

GmbH & Co. KG

High performance rolling of special steel grades in medium-wide format

Dr. Karl Hoen, Christoph Schwarz, Alexander Weller (SMS Siemag), Gerald Zwickel (Bilstein)

BILSTEIN GMBH & CO. KG

Since its foundation in 1911, Bilstein GmbH & Co. KG, or Bilstein for short, has developed into one of the world’s largest suppliers of high-quality cold-rolled special steel products. From its group headquarters in Hagen-Hohenlimburg, Germany, Bilstein supplies renowned customers from a wide range of industries.

Included here are the automotive and metal goods industry, precision engineering, electro-technology, machine and steel production, steel trading and the bicycle industry.

As a reliable supplier, Bilstein wins over customers not only with quality, but also with services. With modern manufacturing technologies and corresponding measuring and control technologies, it meets the closest tolerances and best reproducibility.

Product range

The product range of Bilstein covers standard steels as well as a large range of special grades up to micro-alloyed high-strength steels of up to 1,400 MPa. The company supplies this variety of products in compliance with German and international standards as well as according to customer specifications.

As a supplier of cold-rolled narrow strip, Bilstein also uses slit strip with different strip wedges. This presents a special challenge to rolling operation and plant automation.

Kst 270 Tandem mill

Central to production at Bilstein is the four-stand tandem mill. It was built by SMS Siemag in 1969 and has been extended and revamped several times over the years. On this tandem mill, per year approx. 400,000 t of cold strip in widths from 320 to 670 mm, with entry thicknesses of 7.5 mm down to exit thicknesses of 0.3 mm are rolled.

In 2006, Bilstein awarded a contract to SMS Siemag to modernize the tandem mill. The goal of the revamp was to increase production by 60,000 t/year, improve

product quality and plant availability, and increase the degree of automation. All this required modification and replacements of mechanical components and a new electrical and automation system.

Fig.1 Bilstein tandem mill before revamp. One operator per stand was needed to actuate the rolling process.

MODERNIZATION OF THE MECHANICAL EQUIPMENT

In the entry area of the tandem mill, a new pinch roll unit was installed to increase the tension in front of the first stand and decouple the rolling section from the pay-off reel. Compared to an S-roll unit, the pinch roll unit has the advantage that it can also be used with larger entry thicknesses.

Fig. 2 Revamp of major mechanical components (blue colour). Rolling direction from right to left side.

The new hydraulic screwdowns increase the rolling force by 30%. This provides for greater reduction and increases the plant capacity. All the stands are equipped with direct roll-gap measurement. That ensures direct thickness control as precondition for semi-automatic automatic threading in of the strip.

To reduce the residual oil content and improve strip dryness, as well as to avoid marks and corrosion, a latest-generation dry strip system from SMS Siemag was installed in the exit area of the final stand. The system operates with blowers. Compared to blowing off with compressed air, this solution reduces noise as well as operating costs. Furthermore, the DS system also works well at higher rolling speeds.

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The new swiveling bridle S-roll set decouples the strip tension between the final mill stand and the tension reel, and ensures the strip travels smoothly through the flatness and thickness measurement area.

The modernization also increased the rolling speed of the tandem mill. For this purpose, new gear wheel sets were installed. All the main motors were replaced, and modern synchronous motors with medium-voltage technology were installed in the mill stands. They achieve a higher efficiency at a lower mass inertia than asynchronous motors. The coilers, the strip drives, and the S-rolls are equipped with efficient low-voltage motors. This idle-power-free drive constellation saves a great deal of energy and minimizes negative effects on the power supply system.

AUTOMATION UPGRADE

Before the modernization, the automation of the tandem mill consisted only of Level 1. The mill stands were operated individually. That required four operators – one per stand. The mill stands were set according to a pass schedule, stored in the look-up table. Rolling results were dependent on the operator´s experience and of limited reproducibility.

Beside a new Level 1, the new automation system includes a full-fledged Level 2. On the basis of a model, the system calculates the set-up of the mill for each strip, dependent on mill conditions and rolling stock. It is based on a complete mapping of the rolling processes by self-adopting physical models. The Level 2 also gives BILSTEIN the opportunity, to enlarge the product range in an economic way, by exact pre-calculation of the pass-schedules. Rolling experiments in context with new products can be reduced significantly.

Fig. 3 New automation concept including Levels 1 and 2

In addition the new X-Pact® automation by SMS Siemag makes plant operation more efficient, using a modern operating concept. Today, three employees control the entire plant: one in the entry

section of the mill, one in the exit section and rolling is controlled by one operator in the central pulpit.

Fig. 4 Main pulpit

Further advantages are provided by the threading in/out assistance, called Total Roll Gap Control (TRC®), developed by SMS Siemag. It takes into account the wedge and the thickness deviation at the head and tails ends of the strip, and ensures flat, straight strip travelling. Depending on the material properties, it limits the rolling force and corrects the roll gap if necessary, based on direct roll gap measurement.

IMPLEMENTATION

In order to comply with the given short production downtimes, the challenging modernization project was structured in four phases. One of the specialties of the revamp concept by SMS Siemag was the installation of the Process-IO-Server (PIOS). It allowed the stepwise switch-over to the new automation system and therefore a consecutive commissioning and optimization of the new systems, being able to switch over to the old one. With this measure the production of the tandem cold mill, which is the heart of BILSTEIN´S process chain, was ensured at any time.

RESULTS

The measures described resulted in improved process stability and the desired increase in production by at least 15%. Also improved was the plant availability. At the same time, the specific energy consumption was decreased.

TRC®, the threading in/out assistance system, ensures flat and straight strip travelling and reduces off-gauge lengths by more than 50 % and makes rolling operation more efficient.

A further advantage of the revamp is that thickness tolerances have been improved significantly. Operational results show that thickness is kept in tolerance across the entire strip length, even for strips with different strip wedges.

The tandem mill of BILSTEIN is now ideally equipped for the challenges of the coming years.

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First results of a recently installed Minimum Quantity Lubrication system on a tandem cold mill

Konrad Krimpelstaetter (Siemens VAI)

Andreas Flaxa (Quaker Chemical Corporation)

Introduction

The permanently rising demands of steel producers for optimized processes to reduce operating costs and consumption figures on the one hand and to extend their product mix especially for rolling new steel grades and thinner gauges on the other hand, requires new roll-gap lubrication concepts which are more efficient, more flexible and less oil consuming.

Experienced cooperation partners

In order to find solutions fulfilling these costumer demands, Siemens VAI and Quaker Chemical Corporation joined forces to develop a new and highly effective roll-gap lubrication technology. Siemens VAI contributed by its extensive know-how related to engineering, supply and construction of rolling mills. Quaker Chemical Corporation, one of the world’s leading suppliers for lubricants in the rolling industry, supports by developing customized rolling oils for this new kind of lubricant application.

Minimum Quantity Lubrication (MQL)

The patented process technology features a new generation of advanced roll-gap lubrication which applies pure rolling oil very fine dispersed with air directly onto the work roll surface.

The process equipment requires a novel design of spray nozzles for lowest flow rates and oil/air mixing headers. Therefore, extensive nozzle spray tests were performed on a test rig (cf. Fig. 1) with the goal to investigate and optimize the nozzle design as well as to find optimum process parameters for a uniform and homogeneous distribution of oil droplets. The droplet size can be simply adjusted via the system air pressure.

Compared to conventional roll-gap lubrication with emulsion (either recirculation or direct application type), where the oil concentration inside the roll-bite is mainly resulting from plate-out and wash-off, the level of oil concentration in case of a Minimum Quantity Lubrication is maximized. This significantly improves the roll-gap lubrication between work roll and strip and

hence reduces rolling forces, rolling torques and wear compared to conventional systems.

Figure 1: Test rig for nozzle development

Installed emulsion flow-rates of conventional lubrication systems are mainly selected by the roll cooling requirements since the applied emulsion is also used for cooling of rolls and strip as well as for lubrication and cleaning purposes. By application of pure rolling oil it is possible to apply only the minimum required amount of lubricant which is necessary for the purpose of lubrication to ensure a stable rolling process and superior product quality. This allows a separation of media for cooling and lubrication and to optimize the consumption figures. This leads to a low-quantity lubrication with an oil film thickness in the magnitude of the strip roughness instead of a flooding lubrication. The advantage of MQL is that the film thickness can be adjusted by the oil flow rate depending on process parameters like rolling speed, rolling force, strip roughness, strip tensions, etc.

The new technology overcomes the existing limitations of classical emulsion technology in terms of flexibility (rapid change of highly different lubrication requirements) and ensures the adjustment of a proper lubrication level with reduced oil consumption.

Main objective of this new technology is to reduce rolling forces and rolling torques (energy savings), to extend reduction capability, to improve work roll lifetime (wear), to reduce rolling oil consumption and to improve strip cleanliness.

Prototype installation of MQL on a TCM

A first novel prototype for Minimum Quantity Lubrication (MQL) is installed on stand 2 of a tandem cold mill (TCM). Mixing headers and nozzles are installed on a spray bar on upper and lower strip side

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at mill stand entry to apply pure rolling oil very fine dispersed with air directly onto the work roll surface.

Figure 4: Comparison of measured motor current with and without Minimum Quantity Lubrication (MQL)

The new spray bars are mounted onto the existing spray bars for emulsion lubrication. Figure 2 shows the installed Minimum Quantity Lubrication spray bars in operation in a TCM.

Figure 2: MQL lubrication spray bar in operation

During this test campaign the roll temperatures and final strip temperature were measured. As expected, only a small and acceptable increase of roll temperature was observed because entry side emulsion lubrication was switched-off. This can be simply explained because the main actuator for cooling efficiency is the exit side cooling which sprays the emulsion directly on the work roll surface close to the bite exit. The mill trials also include measurements of the oil mist pollution close to stand 2. With switched-on MQL the oil concentration in the air was never increased compared to conventional emulsion lubrication.

In a first test campaign 16 coils were rolled with Minimum Quantity Lubrication and switched-off entry side emulsion lubrication. In exceptionless all cases the observed rolling force was lower compared to conventional emulsion lubrication. Figure 3 resp. Figure 4 show an example for the comparison of measured rolling forces and motor current (resp. rolling torque) in case of conventional emulsion lubrication and with applied Minimum Quantity Lubrication based on the same rolling material and dimensions. As expected, the rolling forces are decreasing with increasing oil low rate.

Furthermore, the strip cleanliness after rolling and annealing was measured and analyzed. As a first result it can be concluded that the strip cleanliness was in no case worse compared to conventional emulsion lubrication.

The prototype trials showed significant reduction of rolling forces and rolling torques (energy savings) and reduced oil consumptions per rolled ton.

Figure 3: Comparison of measured rolling forces with and without Minimum Quantity Lubrication (MQL)

Detailed results of these prototype tests will be presented in the conference presentation.

Conclusion

A first novel prototype for minimum quantity roll-gap lubrication (MQL) was installed on stand 2 of a tandem cold mill. The prototype features a new generation of advanced roll-gap lubrication which applies pure rolling oil very fine dispersed with air directly onto the work roll surface.

The development includes a novel design of spray nozzles for lowest flow rates and oil/air mixing headers as well as tailor-made rolling oils for this kind of application.

The prototype tests clearly show that this new lubrication technology works well in industrial fields and shows high potential to overcome the existing limitations of classical emulsion technology in terms of flexibility (rapid change of highly different lubrication requirements) and ensures the adjustment of a proper lubrication level with reduced oil consumption.

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Evaluation of tool material Vancron 40 with regard to wear,

surface quality and galling

M. Tahir (Dalarna University), N-G Jonsson (Jernkontoret), J. Lagergren (Åkers AB), L.

Wikström (AB Sandvik Materials Technology), H. Hedenlund (Outokumpu AB, now Siemens AB),

SWEDEN

EVALUATION OF TOOL MATERIAL VANCRON 40 WITH REGARD TO WEAR, SURFACE QUALITY

AND GALLING

Abstract Resistance to adhesive wear on tool material can be improved by increasing the tool hardness, high ductility and decreasing of friction coefficient between the tool and the work material. In a similar way, resistance to galling can be increased by increasing the tool hardness and decreasing of friction. The purpose of this project was to investigate the use of Vancron 40 as work rolls in cold rolling of stainless steel in cluster rolling mills. Considerable factors were among others, the influence of different industrial lubricants, minimizing of temperature rising during rolling, lowering of rolling forces, longer life of rolls, easier grinding of rolls, increase the oil film bearing at normal cold rolling conditions and improving surface roughness of the final products.

For using of work rolls in cold rolling cluster mills, roll material Vancron 40 was evaluated with regard to roll wear, surface quality and galling. Currently used roll type ASP23 was used as reference roll in the evaluation. The experiments were performed, as much as possible, in accordance to steel industries recommendations. The experiments were conducted with a 4-high pilot rolling mill at Swerea MEFOS in Luleå which is equipped for rolling of both flat and long products. The experiment was done for different industrial mineral-based lubricants. Lubrication was applied in a controlled form to the upper and lower work rolls and in the contact zone. To achieve the proposed final thickness, five passes were rolled. The characteristic of the upper and the lower work rolls, during rolling, was also examined. The pilot experimental results gave promising result in surface roughness, galling and roll material hardness. Due to its chemical and physical properties, Vancron 40 is believed to be the best solution to resist adhesive wear and galling in cold rolling process that require higher accuracy.

Introduction Three proposed roll materials were studied for using as work rolls in cold rolling of steel strip. The study

was conducted with respect to roll wear, surface quality and galling. Pilot experiment was conducted and the result was analyzed. The two proposed roll materials were, Vancron 40 (Nitrided Powder Metal Tool Steel) and ASP23 (Chromium-molybdenum tungsten-vanadium alloyed high speed steel [1, 2]. Tool materials characteristics, physical and chemical properties and recommended heat-treating process were described. ASP23 which was used as work roll in industrial operation was used as reference material. Two different tests were performed. One accustomed to Outokumpu AB rolling process and another was accustomed to AB Sandvik Materials Technology rolling process rolling process (SMT). The tests were performed, as much as possible, in accordance to companies’ recommendations. The experiments were conducted with a 4-high rolling mill. Tool Materials Chemical compositions of the proposed materials are shown in Table 1. Table 1 Product range of tool steels suitable for cold work applications [1, 2, 3]

Steel grade

Type of metallurgy

Chemical composition (weight %)

% C % N % Si % Mn % Cr % Mo % W % V Vancron 40

Powder metallurgy

1.1 1.8 0.50 0.40 4.50 3.20 3.70 8.50

ASP23 Powder metallurgy

1.28 - 0.50 0.30 4.20 5.00 6.40 3.10

Pilot experiments Two separate pilot experiments were conducted at Swerea MEFOS (experiment I and experiment II). The first experiment was done with Outokumpu AB material and the second one was done with SMT material. Mineral oil lubricants with Ester and EP additives were used. The experiments were conducted with a 4-high rolling mill.

The dimension of the strip was 48x0.68 mm and the average surface roughness, Ra was 0.86 µm. Ra of the upper and lower work rolls were 0.12 resp. 0.13 µm, which is consistence with the industrial Ra values for the specific strip grades. The work roll diameter was 50.2 mm with circumference of 157.1 mm. Five passes were taken to reach the desired final thickness, Figure 1. The final thickness of the strip with rolling of ASP23 rolls was 0.16 mm and with V40 rolls was 0.13 mm.

Figure 1 Reductions of ASP23 and V40

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Experimental Results In Experiment I, Average surface roughness; Ra, Rq and Rz measurement of strip and the work rolls (ASP23 and V40) were conducted after rolling (after taking the required passes). In case of work rolls, the measurement was done for both upper and lower work rolls. Figure 2 and 3 shows the result of average surface roughness measurements of Ra and Rq of experiment I and II. As shown in the figures, V40 with its self coating and its hardness characteristics gave very low Ra and Rq. Results are confirmed for both upper and lower work rolls. To secure the accuracy of the measurements, the measurement was conducted in three different positions on the roll barrel.

Figure 2 Average surface roughness of ASP23 and V40, experiment I

Figure 3 Average surface roughness of ASP23 and V40, experiment II

To study the effect of surface defects due to temperature rising, work rolls surface temperature was measured after every pass. The increasing of surface temperature of the upper and lower work rolls was measured and the surface temperatures of the upper work rolls confirm higher values than the lower work rolls. The reason of temperature differences can be an uneven lubrication of the upper and lower work rolls that cause frictional differences between the upper and lower rolls.

As roll material hardness is one of the main factors affecting wear and galling, hardness test was conducted on the work roll materials to determine hardness after finishing the rolling process. Hardness test was conducted for both “in rolling path” and “outside rolling path”. As shown in Figure 4, the

hardness of V40, after rolling five passes, didn’t decrease. In contrary, for both upper and lower rolls, the hardness of “in rolling pass” increases more than it was before (outside rolling pass). While in case of ASP23; the hardness decreases from 943 to 918 Vickers for the upper roll and from 1023 to 828 Vickers for the lower roll.

Conclusions The pilot experimental results gave promising result in surface roughness, galling and roll material hardness. V40 shows its superiority compared to the reference material ASP23. The author recommended testing V40 in the whole campaign in rolling mills. Figure 3 Surface temperature measurements of the upper and lower work rolls

Figure 4 Hardness test of the work rolls

Acknowledgements The authors are indebted to VINNOVA - Sweden´s Innovative Agency, Jernkontoret - the Swedish Steel Producers' Association and the industrial contributors (Outokumpu Stainless AB, Rautaruukki Oyj, AB Sandvik Materials Technology, SSAB EMEA AB, Uddeholms AB and Åkers Sweden AB) for financial and other practical support.

References 1. Pocket book, The Uddeholm range of tooling

materials, Edition 2, 10.2008, available at: http://www.uddeholm.nl/dutch/files/Uddeholm Pocket book E2 .pdf, viewed on 2011-09-01

2. Uddeholm Vancron 40, Edition 1, 11.2006, available at http://www.uddeholm.se/swedish/files/Vancron40-swedish 061105.pdf, viewed on 2011-10-01

3. New development in Tooling Materials: Antigalling steel for most difficult tooling applications, Böhler Uddeholm, available at http://ctma.com/wp-content/uploads/Patricia-Miller-BohlerUddeholm-Presentation-for-WTC2010-2.pdf viewed on 2011-09-01 

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Novel Method for Setting the Mechanical and Topographic

Properties of Strips within one Process Step

V. Diegelmann (VDEh-Betriebsforschungsinstitut GmbH, Germany)

G. Zwickel, M. Ullrich (Bilstein GmbH, Germany) H. Gouveia (Instituto de Soldadura e Qualidade,

Portugal) U. Weirauch (Andritz-Sundwig GmbH, Germany) A.V. Pernia Espinoza (Universidad de la Rioja,

Spain)

INTRODUCTION Main objective was the development of an innovative strip finishing procedure by combining tension levelling and skin pass rolling into one production step and thus to shorten the process chain. It could be proved that the mechanical characteristics of strip material mainly adjusted during the skin pass rolling process are possible to be achieved as well during a pure tension levelling process by variation of applied tension and bending load [1,2]. The realisation of the desired surface texture requires an additional superposed deformation under pressure introduced simultaneously in those strip sections where the yield strength of the material already is met by the applied tension-bending procedure. Using the new facility it is possible to adjust material mechanical and surface roughness properties separately. Thus the new technique fundamentally contributes to the common development to require steel grades with highest surface quality and simultaneous highest available deformation resources.

CONDUCTED WORK To reach the above mentioned objectives the whole work was subdivided into the following main parts: - Design, construction and implementation of new

facility - Pilot plant trials for process and process model

development - Trials and trial evaluation - Comparing tests with conventional process

The existing pilot plant of BFI was reconstructed to run the trials. The design, construction and implementation was carried out by Andritz Sundwig. The design work was supported by FEM studies coming from Uni Rioja using Abaqus software. The pilot trials were conducted by BFI to identify the process parameter setting for best strip quality starting at default values deduced from FEM modelling. A sensitive study for the existing process parameters was performed accompanied by further optimisation of found process parameters using statistical methods. Set-up and control model basic developments were

carried out. The newly developed process was evaluated running comparing tests with the common skin pass rolling process. Bilstein as a producer of cold rolled steel strip carried out this part of the work together with BFI. The resulting material properties were investigated by ISQ using a tensile test facility, a micro hardness measurement device, alternating bending device, metallographic methods for microstructure identification and by BFI using 2D / 3D topography measurement devices for strip surface identification. ISQ additionally investigated appliance properties e.g. deep drawing, painting and bonding behaviour for identifying the appliance qualification important for the customers further processing. Bilstein supported the run trials by material selection and delivery, and material mechanical tests.

Design and construction of the hybrid facility The design of the tension levelling-skin-passing unit (Figure 1) is formed of 2 bending cartridges and 2 skin-passing cartridges each. One pair of cartridges each consisting of a bending and of a skin-passing cartridge, is arranged hydraulically adjustable against each other in vertical direction. In order to skin-pass the strip top and strip bottom side, one skin-passing cartridge resp. bending cartridge each is above the strip passage, the other one below. The bending cartridge consists essentially in the bending roll, ø 80 mm, with end bearing assemblies to accommodate the axial forces as well as two back-up roll rows, ø 90 mm, which support the radial force components. The skin-passing cartridge will consist of the skin-passing roll, ø300 mm, incl. bearing assembly to accommodate the axial and radial loads as well as 2 bending rolls each ø 100 mm, which can be pivoted around the center of the skin-passing roll into the strip. According to the pivoting angle a changed overlapping will result (wrap angle) of the two bending rolls, ø100 mm, and the bending roll, ø80 mm. Thus the bending/tensile stresses in the strip cross-section can be modified. At maximum possible overlapping a maximum wrap angle of 71° is possible to adjust. The completed pilot plant with the new hybrid facility can be seen in Figure 2.

Figure 1: Arrangement of acting rolls

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Figure 2: Pilot plant with new hybrid facility

Trials and trial evaluation In total 162 trials were run with the steel grades DC04 and ZSTE800. The thickness-width dimension for the DC04 was 1mm x 200mm and for the ZSTE800 0,8mm x 150mm. The trials were run varying the applied tension, the bending degree and the roll force. The DC04 was investigated under symmetric and asymmetric bending roll adjustments respectively. The ZSTE800 was investigated only under symmetric bending roll adjustments. Focused on the optimum adjustment of the bending rolls and texture transfer roll force in order to run the facility with lowest required elongation and at the same time with optimum roughness transfer, specimen were taken from the rolled strip reflecting different parameter combination adjustments. Besides a flatness measurement the specimens were tested by use of tensile tests to determine the resulting mechanical properties. Roughness transfer from roll to strip by 2D/3D surface analysis using mechanical and laser optical devices was detected. Additionally the appliance properties were investigated.

Comparing tests with conventional process The common skin pass rolling process was compared with the new hybrid process by running industrial trials at facilities of Bilstein using the same steel grade (DC04) as during the pilot tests. Three different campaigns were carried out applying roll force, and tension varied on three levels. Tension was adjusted customary, 50% above customary and 50% below customary level. The skin pass degree and the resultant strip roughness have been chosen as the target parameters for further assessment. During each campaign the skin pass degree target was varied from 0,4% to 2% in steps of 0,2%. For each skin pass degree target the roll force now adjusted itself under the given tension condition. Comparing investigations can be summarised by stating that the material shows

comparable properties also in terms of appliance properties, that the required roll force for adjustment of the elongation degree could be reduced by about 25% and that the final strip topography from the common process is of higher quality mainly because of the much better roll topography achievement.

RESULTS Based on a statistical analysis significant parameters having impact on the elongation degree and the roughness transfer were identified:

- Penetration depth of bending roll - Applied longitudinal strip tension - Texture transfer roll pressure

Applying above mentioned parameters the elongation and the roughness transfer are possible to be adjusted separately. The skin pass power requirements could be reduced by approx. 25% compared to the common skin pass process (Figure 3). A working point could be identified. Nevertheless optimisation measures are required. The flatness issue needs to be further investigated. The finally received material mechanical properties show comparable behaviour. Surface quality was measured 2D and 3D. The roughness transfer was evaluated and was found to be good under the given conditions. The material appliance properties show normal characteristics.

Figure 3: Comparison of common skin pass and hybrid skin pass process regarding required roll forces CONCLUSION A new strip finishing procedure by combining tension levelling and skin pass rolling into one production step successfully was developed. The gained knowledge is intended to be further increased and to be transferred onto industrial scale by a continuing pilot project. BIBLIOGRAPHY [1] "Control of the yielding and ageing behaviour in

temper rolling” EUR 20214 EN, 2002 [2] "Control of sheet surface defects and deep

drawing properties in final strip production steps”, Contract No 7210-PX/338 (Completion date: 30.06.2005)

Page 222: 2-page abstracts booklet

TopPlanHybrid: A New Hybrid Online Measurement System for

Measurement of Surface Shape of Rolled Strips with Arbitrary Reflection Characteristics

H. Krambeer (Betriebsforschungsinstitut, Ger.) R. Fackert (IMS Messsysteme GmbH, Germany) M. Feldges (Betriebsforschungsinstitut, Ger.) W. Gerlach (ThyssenKrupp Nirosta, Germany)

U. Müller (Betriebsforschungsinstitut, Germany)

INTRODUCTION The flatness of steel strips and plates poses an impor-tant quality aspect. Thus on-line flatness measure-ment and automatic flatness control are central ele-ments to improve quality in rolling and processing. Conventional non contact flatness measurement sys-tems in plate and strip rolling are based on triangula-tion method using laser optical sensors. The signifi-cance of the flatness characteristics measured by this method is affected by movements of the plate or strip in height direction. The topometrical on-line flatness gauge “TopPlan®” is based on the projected-fringe (2D-triangulation) meth-od. The flatness characteristics are determined by measuring the surface topography over large areas of the plate or strip. This eliminates the system-based disadvantages of the one-dimensional measuring method. These common noncontact measurement systems are developed for at least partially diffuse reflective surfaces. In the standard approach a structured light pattern is projected onto the surface and a camera is taking photos of the strip. These measurement systems fail at high reflective materials like stainless steel, be-cause of the mirroring properties of the strip. The camera would see only the reflected surrounding of the projector. Usually the system for high reflective strips called TopPlanReflect, consists of a camera, which is orien-tated to the reflective surface of the strip, and a screen plate, on which a structured pattern is printed. The camera sees the mirror image of the pattern on the screen. If the reflecting surface is plane, then the camera receives the pattern of the plate undistorted. Disturbances in the reflecting surface (buckles, waves, crossbow etc.) distort the mirror image of the plate. The deformation of the pattern of the plate is used for the computation of the height matrix and the flatness. This method also is called deflectometry. The new measurement system TopPlanHybrid is combining the projected-fringe method and additional the raster reflection method. Therefore a second ca-mera is directed towards a screen receiving the direct reflection of the projected pattern.

FLATNESS MEASUREMENT BY PROJECTED-FRINGE-METHOD Using the projected-fringe-method a stripe pattern is projected onto a section of the strip surface. This stripe pattern is detected by a CCD-camera. The evaluation of the stripe pattern results into an image of the actual surface expressed by a three-dimensional matrix of heights of the complete strip section. When the stripe pattern is projected onto an ideal plane (see Figure 1) in the pass-line of the strip (z=z0), denoted by “reference plane”, the view ray s meets the projection ray p0 (inverse ray tracing). In case of an object present in the optical path and higher than the reference plane, the view ray s meets the projec-tion ray p. The local height z now can be computed by means of projection ray p [1, 2].

Figure 1 Principle of the projected-fringe method

FLATNESS MEASUREMENT BY PATTERN-REFLECTION-METHOD A similar configuration for an object having a reflective surface is shown in Figure 3. The view ray s of the camera is reflected at the “reference plane” z0 as re-flected ray r0, which meets a defined point at the screen plate (with a cross grid pattern). In case of an object in the optical path higher than the reference plane and with unknown inclination, the view ray s is reflected at the object as reflected ray r, which meets a point at the screen plate [1, 2]. The local height cannot be computed directly, because of the unknown direction of the reflected ray r.

z

Figure 2 Principle of the pattern reflection

It is possible to find a clear solution under considera-tion of several view rays. Different to the stripe projec-

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tion procedure a grid has to be used to clearly identify the points on the screen plate.

FLATNESS MEASUREMENT BY COMBINATION OF BOTH METHODS In order to cover a wide range of surface conditions a hybrid measuring system technology was developed. This hybrid system not only serially connects the existing subsystems but combines their modified versions into a unified system.

Figure 3 Principle of the hybrid system

In Figure 3 the basic layout of the two measuring principles is displayed for one ray of light. A light pat-tern is projected onto the strip surface. In case of non-reflective surfaces the diffuse part of the light is re-flected and picked up by the camera whereas for high reflective surfaces the pattern will be reflected onto the screen plate following the law of equality of angle of incidence to angle of reflection. The camera R re-ceives the pattern from the screen.

INSTALLATION AT A BRIGHT ANNEALING LINE The installation of a prototype of the TopPlanHybrid System is shown in Figure 4. A frame was designed to support the screen plate projector and both cameras.

Figure 4 Installation of a prototype of TopPlanHybrid at an annealing line of TKN

Image acquisition: An image of the distorted cross grid pattern taken by the TopPlanReflect camera is shown in Figure 5. Intuitively the strip shape can be qualitatively imagined as waviness. Computation of

the height matrix: The basic evaluation procedure comprises first an image transformation from camera chip level to the object coordinates of the measure-ment area respectively to the screen coordinates.

Figure 5 Camera R is oriented to the screen and re-ceives the reflected pattern at the screen plate

cted fringe meth-od delivers the local height values.

The common procedure is using fringe pattern. Phase computation including smoothing discontinuities of thephase, is also applicable to a cross grid (Figure 6). Based on the phase image, the proje

Figure 6 Phase images of the screen image (Figure 5)

and width direction, the height

rameters are deduced from the

tion, quality monitoring and flatness control systems.

in length and width direction Based on the phase images, the pattern-reflection method delivers the local slope of the surface. After integration in length- values are available. For both methods the transfer function of the system is required. The pasystem calibration.

CONCLUDING RESULTS OF THE MEASUREMENT The length distribution, reflecting one result of the evaluation algorithms, is shown in Figure 7. It will be used for visualiza

Figure 7 Flatness: length distribution of a strip section

terreflexionen,

logy for Production Engineer-ing, Proc. SPIE 5457 (2004)

BILIOGRAPHY 1. J. Beyerer, D. Pérard, Automatische Inspektion spiegelnder Freiformflächen anhand von RasTechnisches Messen 64 (10), 394-400, 1997 2. M. Knauer, J. Kaminski, G. Häusler, Phase Measuring Deflectometry: a new approach to measure specular free-form surfaces, Optical Metro

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Integrated thickness- and flatness control for Sendzimir mills

J. Polzer (VDEh-Betriebsforschungsinstitut,

Germany) A. Wolff (VDEh-Betriebsforschungsinstitut,

Germany) M. Jelali (FH Köln, Germany)

M. Truskowski (ThyssenKrupp Nirosta GmbH, Germany)

R. Fackert (IMS Messsysteme GmbH, Germany) T. Hermey (IMS Messsysteme GmbH, Germany)

Introduction For cold rolled flat products, strip thickness and flat-ness are major quality parameters. However, the con-trol of these two quality parameters with high perform-ance is not independently possible with standard sys-tems. Thickness and flatness control have got an in-fluence on each other. To avoid thickness deviations through the flatness controller normally the flatness controller is slowed down strongly [1]. This leads to a degraded performance. The drawbacks of separated thickness and flatness control are overcome through the presented model based integrated thickness and flatness controller. The new controller has been im-plemented and is running at a Sendzimir mill of ThyssenKrupp Nirosta. Industrial results of the con-troller are given in this paper. Figure 1 shows the schematic view of a Sendzimir mill. The flatness can be influenced through the crown adjustments (7 over strip width) and the taper rolls. The strip thickness is result of the screw down mouvement and the eccenter positions A, D. The screw down itself is often also realised as an eccenter. Control concept The controller has three main aims:

- Fast elimination of thick-ness errors,

- a quick correction of flat-ness errors, using the complete potential of all flatness actuators and

- a compensation of all cross couplings between thickness and flatness.

To reach all aims at the same time, the realised control system is mainly based on the approach of Internal Model Control (IMC, [2]). The IMC structure considers all time/speed dependent death times and includes time delay compen-

sation. An essential part of this approach is a dynamic model of the mill (see ) to predict the bahviour of the mill.

Figure 2

h0, h1,v0, v1

Model

Rolls diameters and strip geometries

Thickness in the roll gapInfluence functions of flatness actuatorsInfluence functions of thickness actuatorsTaper rolls positions

Crown positions

Screw down positionsFlatness in the roll gap

Cross couplings betweenthickness and flatness

Figure 2: Model of the Sendzimir cluster

Model The developed model simulates the plant and in-cludes the cross couplings of the process. The follow-ing parameters are used as input of the model:

- screw down positions and eccenter angle, - crown positions, - taper rolls positions, - strip thicknesses and strip speeds, - all roll diameters and - material properties.

As a result the model delivers estimates for:

- flatness in the roll gap, - thickness in the roll gap, - influence functions of flatness actuators

crown,

- Regard of mutual interactions of actuators- Integrating all control componentsof gauge and flatness

- Model based control

HydraulicScrew Down

Taper RollShifting

Crown Adjustment D(Positioning of Eccenter))

Crown Adjustment A(Positioning of Eccenter)

IntegratedGauge and Flatness Control

Thicknessmeasure-ment

Flatnessmeasuring roll

Laser speedmeasurement

Laser speedmeasurement

Flatness measuring roll

Thicknessmeasure-ment

Figure 1: Schematic view of the Sendzimir mill

Page 225: 2-page abstracts booklet

- on/off controls for all parts of the control system - influence functions of flatness actuators taper rolls, The thickness and flatness actuators work at maxi-

mum speed without disturbing each other, thanks to the integrated approach, as can be seen in . This is a big advantage of the developed controller.

- influence function of thickness actuator, Figure 4- actual cross couplings between thickness and

flatness

Figure 4: Online visualisation for the operator under active integrated thickness & flatness controller

Industrial tests To demonstrate that the flatness actuators can be used at full speed without disturbing the exit thickness h1, the following test was performed (see: ) Figure 3

Figure 3

Figure 3

- The integrated thickness-flatness controller was active at the SG II.

- One output of the flatness sub-controller was manually changed between 0 mm and 25 mm (corresponds to bending), the other outputs are kept constant.

- The crown positions followed the desired val-ues with maximum speed. The actual position of the centre crown is shown in the middle subplot of Figure 3.

- The flatness measurement is characterised with orthogonal gram polynomials [3]. The change of the flatness can be seen in the first subplot of in the corresponding gram polynomial coefficient (c2) of the flatness measurement.

Conclusion Industrial results of the model-based integrated thick-ness and flatness control system are very good. The new control system achieved directly a high accep-tance of the operators. Simultaneously, all actuators can be run at maximum speed. Especially flatness errors are eliminated much faster than with sperated control. This approach is not restricted to Sendzimir mills. With an adapted model this control concept can be used at tandem and temper mills too.

Without a compensation of the cross couplings the exit thickness h1 is disturbed in such an experiment through the fast crown movements. The integrated thickness-flatness controller compensates the disturb-ing effect of the flatness actuators and the resulting exit thickness is undisturbed, as can be seen in the third subplot of . The actuators for the flatness control are now allowed to operate at maximum speed.

Figure 3: Successful test of decoupling be-tween flatness and thickness control

References [1] Jelali M., U. Müller, A. Wolff, W. Ungerer (2001b): Advanced control strategies in rolling mills. Metallurgi-cal Plant and Technology (MPT) International 3/2001:54–58. [2] Morari M, Zafiriou E (1989) Robust Process Con-trol. Prentice Hall. [3] Kristinsson K.; Dumont, G.A.: Paper Machine Cross Directional Basis Weight Control, Using Gram Polynomials. In: Second IEEE Conference on Control Applications, Vancouver, B.C., 13.-16. September 1993.

Figure 4 shows the visualisation mask for the opera-tor. The layout consists of the parts: - header (strip geometries etc.) - flatness measurement und reference curve (blue) - positions of the seven crowns - positions of the taper rolls - thickness measurements (h0 = red, h1=green)

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Major Improvements of the Skin-Pass 48” at ArcelorMittal Florange

Pierre Roblin (GE’s Power Conversion business),

Frederic Baudel (GE’s Power Conversion business),

Thierry Legrand (ArcelorMittal Florange), Xavier Breuval (ArcelorMittal Florange)

INTRODUCTION The ArcelorMittal Group (hereinafter referred to as AM) is a world leader in the production of steel flat product. AM has a 2-stand Skin-Pass Mill in Florange, East of France. Their Skin-Pass Mill is used to roll packaging products. The mill was originally commissioned in 1963 and is currently producing up to 450,000T per annum. This paper describes the recent modernization of the mill to improve the quality, the productivity and the maintenance. The modernization project was undertaken by GE’s Power Conversion business (hereinafter referred to as Power Conversion). The project’s scope included both automation and electrical upgrades.

The electrical upgrade included the supply of a new control of every DC converters and the supply of new Low Voltage drives.

The automation upgrade included the supply of a new state-of-the-art automation system composed of High Performance Controller PLCs, safety PLC, Remote I/Os, HMI system, PDA and development & maintenance stations.

The main installation work took place in December 2011 including commissioning, product tuning and production ramp-up.

ARCELORMITTAL’S OBJECTIVES

AM’s aim is to:

• Assure the sustainability of electrical and automation equipment by replacing obsolete equipment by last update one

• Improve the mill’s reliability and maintainability

• Improve the availability of the mill

• Completely review the operator interface:

o Ergonomic fault management and missing conditions systems with historical data-logging

o Easy diagnosis and troubleshooting analysis to shorten maintenance time intervention

• Increase the mill’s production capacity by decreasing the elapsed time between 2 coils

• Improve the quality of the product.

PROJECT MANAGEMENT Power Conversion provided a turnkey project, including technical leadership with responsibility for the design, specification, review, inspection and planning of all aspects of the project, excluding civil works. Power Conversion also led the commercial responsibility of the contracts with local sub-contractors for cabling and installation of the new equipment. Power Conversion’s prime responsibility remained the achievement of the performance targets and the project timescales. TECHNICAL SUMMARY Upgrade of the Skin-Pass Mill:

• New control PECe for every DC converters interfaced with the existing power bridges. The control uses the same hardware and software as the HPCi PLC for automation

• New power supply for the DC motor field

• New pulse generators for elongation control

• New AC low voltage drives and motors for the entry and exit conveyors

• New HPCi High Performance Controllers for process control and sequences associated with P80i development and maintenance work bench

• Safety PLC implementing advanced safety principle defined by AM

• New Human Machine Interface including the fault and permissive management systems

• New PDA system with video server

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PERFORMANCE AND QUALITY ACHIEVEMENTS PROJECT IMPLEMENTATION

Guarantees were provided to AM for each key product quality parameter:

Planning and functional specifications were developed jointly by the Power Conversion and AM project teams during the course of the project.

- product quality o Elongation: reduction by 50% of the off

gauge length The project was launched in January 2011 and the requirement specification phase started with the aim of collecting all the information required for hardware and software procurement and design.

o Thickness: reduction by 50% of the off gauge length

- cycle times and production rate control - installation reliability An automation test platform with automation

equipment, including a mill simulator, was set in order to largely test the overall process application. Process control was also validated by using real process records. In this way, the automation system was pre-commissioned, thereby reducing the commissioning time while respecting the production ramp-up time.

As a result of the new tuning of the process control, a rapid improvement of product quality was achieved. Some products can now be rolled with good quality, which was not the case before the modernization.

The design, coding and test period for the new equipment was completed in an eleven months period. AM witnessed a factory acceptance test (FAT) in November 2011.

CONCLUSION

The electrical and automation modifications of the AM Skin-Pass Mill have been completed as planned. Substantial performance benefits have been achieved for product quality, productivity and maintenance.

The electrical and automation equipment were installed during the mill shutdown, in December 2011. The duration and detailed activities of this shutdown were planned jointly by Power Conversion and AM. Mill start-up was achieved on-schedule. After a limited number of trial coils were run to prove the system operation, the mill was handed over to production and production resumed without delay.

The project objectives were reached thanks to the close cooperation between the project teams of AM and Power Conversion, the main contractor.

Figure 1 – View of the 2 stand Skin-Pass Mill