Electric Steel Making Technology in the 21st Century

8/3/2019 Electric Steel Making Technology in the 21st Century

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ELECTRIC STEEL MAKING TECHNOLOGY IN THE 21ST CENTURY

R.P. Varshney, Executive Director, AIIFA,Delhi

Introduction

The world at present is witnessing technology up-gradation in regard to input materials andtechnology for steel making and pig iron production. Good quality iron ores are depleting allover the world and in the same way good quality coking coal needed for reduction of iron

ores in blast furnace is also becoming scarce. Big hills of iron ore fines can be seen at theiron ore mine heads because in Blast Furnaces only certain weight and size of iron ore grits

can be used. Thus, to reclaim the fine iron ores several technologies have been developedto make pig iron.

Remalt Process for Pig Iron

Russians have developed a technology of using iron ore fines by making agglomerate of

fines and then charging them in a furnace where ordinary coal can carry out reduction of

iron ore and make pig irons. It is closed chamber furnace. National Mineral DevelopmentCorporation (NMDC) who mine iron ore and export it to other countries have a tie-up withRussia for installing the ROMALT process at Bailadila in the State of Chhattisgarh. Similar

plants have been developed by Austria, etc. which can be used according to the types of

iron ore fines availability and the reduction i.e. Carbon content material availability.

COREX Process

COREX Process was developed by the Austrian firm who utilizes good quality iron ore with

poor quality of coal. In a closed vessel, the reaction takes place and the ore gets reduced.In India, the COREX process plant has been installed by M/s Jindal Vijaynagar Steel Limited

in the State of Karnataka. The pig iron produced in the plant is sent to LD converters forproduction of Steel. The Pig iron has been made by COREX process, ROMALT process and by

HYSMELT process. Low shaft Blast Furnaces is also being used.

Manufacturing Steel - Continuous Casting Process

More and more International Steel plants are at present using continuous casting machines

for the manufacture of long as well as flat products of steel. India is also not lagging behind.Over two dozen Electric Induction Furnaces are using continuous casting process.

Manufacture of Sponge Iron/Direct Reduced Iron - As Input Material to Steel

Making

As stated earlier, the iron ore has to be reduced to remove the Oxygen content.

Carbonaceous materials are to be used but for smelting the carbonaceous materials do nothave the property to carry out sufficient reduction of iron ores. The technology was

developed in Germany known as SLRN process in Sixties to use iron ore, mix it withlimestone and then use ordinary coal. These are fired in horizontal kilns of 60 ft. to 90 ft.

long which are kept rotating to allow the input to mix up. From various points and zonesfiring is done. It will bring the temperature to near about 1350C to 1400C. At this

temperature, the carbonaceous material reacts with FeO, FeO, etc. and removes theoxygen from the ores. This contains iron upto 90% and rest is gauge material. The

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reduction of iron ore is also carried out by using Compressed Natural Gas (CNG). For thispurpose pellets of iron ore are taken from palletizing plants. Coal is added in the kilns. Here

again at a temperature of 1350C, the carbon content of the gases react with the iron oreand reduce the Oxygen of the ore. The product is called Hot Briquetted Iron (HBI). The HBI

are considered to be superior than the coil based sponge iron. Sponge iron is input materialnot only for Electric Steel making but also in big Integrated Steel Plants who charge it in the

blast furnaces or at any point where it is necessary to increase the productivity. For theproduction of Steel by Electric Steel making route, Sponge Iron/HBI is a good substitutebecause it contains least tramp elements. The steel melting scrap is rendered from Steel

products, which may contain Copper, Chromium and other metals, and non-metals, which

will make the steel, produced dirty. Thus due to absence of tramp elements, sponge iron isgaining popularity in steel making.

Electric Process of Making Steel

Due to shortage of Steel in the Country, Government of India allowed a member of Electric

Arc Furnaces (EAFs) to produce steel in the Secondary Steel Sector by recycling the steelscrap. Since early 70"s to 1985, nearly 150 EAFs were installed with a capacity of over 9

million tones in various parts of the country. However, in the meanwhile the MediumFrequency Induction Furnaces technology came into the country in early 80's. Electric

Induction Furnaces have been installed in all states in India and India is perhaps the onlycountry in the World using Induction Furnaces on a large scale to manufacture secondary

steel.

Electric Arc Furnaces of bigger capacities say 150 tones/charges have been developed. Therecent developments in EAF technology are the increased oxygen consumption, reducing

power consumption and decrease in tap to tap time and the increased hot metal proportion

to reduce power consumption and control 'Cu' content which comes from steel melting scrapto produce higher grades of steel. At present nearly 30% of steel is produced by EAF route

in the world. This is because of more and more availability of steel scrap.

Electric Arc Furnaces

Electric Arc Furnaces installed in India were of small capacities ranging from 5 tonne to 20tonne per charge in early seventies. The reason was (a) non availability of big size furnaces

(b) to cater the need of shortage of steel for construction industry as the product of Arcfurnaces was not under Government control of prices unlike steel produced by integrated

steel plants. (c) Facilities provided by Government such as less excise duty of Arc furnaceproduct. Thus EAFs were installed in J & K, Punjab, Haryana, Himachal Pradesh, Uttar

Pradesh, Rajasthan, M .P., Bihar, West Bengal, Orissa, Andhra Pradesh, Tamil Nadu,Karnataka, Maharashtra & Gujarat. There was some slump in 1975 to 77 and to rehabilitate

them the banks reduced interest rates, excise duty was reduced. Finding shortage of steel

melting scrap in the country, import of steel scrap was allowed at concessional custom duty

rate. From1978 to 1985 EAF s did very well.. Some of them started diversifying theproduct-mix made by them. Some installed balancing equipment and continues castingequipments. In mid eighties the profitability of EAFs up to 15 tone/charge decreased

particularly who were producing pencil ingots only. Some of EAFs did not take action to

reduce power consumption etc. When the Induction Furnaces started producing steel from84-85 using less power, the competitiveness of EAFs became less and less despite steel

Ministry not giving license to Induction Furnaces to make steel and import scrap. However,EAFs were still favored by Steel Ministry in giving steel melting scrap, which was canalized

by Government of India, through MSTC and allotted to EAFs only. But Induction Furnaces

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got import duty concession for importing steel melting scrap in 1998 through MSTC. Thismade the production of EAFs for making only pencil ingots uneconomical. Only 35 EAFs are

in operation at present who have diversified their production or have started flat production- color coating or galvanizing them, etc.

Electric Induction Furnaces

Induction Melting Furnaces in India were first installed to make Stainless Steel from

imported Stainless Steel Scrap. But in years 1981-82, some entrepreneurs who were havingsmall size Induction Furnaces, and making Stainless Steel experimented in making Mild

Steel from steel melting scrap. It succeeded. More firms in northern India produced Steel(Pencil Ingots) by using 500 kg to 1 tonne Induction Furnaces. The power consumption was

found to be about 650 Kwh/tone, which were nearly 100 units less than EAFs. Bigger sizeInduction Furnaces were then installed first in North India and then in other states of India.

By 1985-86, the technology of making Mild Steel by Induction Furnace route was masteredby Indian Technologists. Induction Furnace manufacturers saw the potential and started

installing bigger size/capacity Furnaces. By 1988-89 period 3 tonne per charge InductionFurnaces were installed (became standard) all over India. The chemistry of melt was

adjusted by adding mill scale if opening carbon of bath was more. Good quality of steelmelting scrap was used. In 1991-92, the Government license and control on steel making

and rolling was removed. Then more Induction Furnaces were installed all over India.Backward and forward integration took place. The use of sponge iron made it possible to

adjust chemistry of melt. Thus good quality of Mild Steel pencil ingots are being producedwith no tramp elements.

Technological Upgradation

The fact that Electric Induction Furnaces are producing Mild Steel of structural quality in

considerable quantities indicates both quality-wise and price-wise, they are competitive andwill become still better if Government of India adopts a more pragmatic policy with regard

to cost of Energy. Improvements are taking place in the Panel Circuit design and in Powerfactor. It is hoped that by improved panel circuit design, power consumption can be

achieved below 600 Kwh per tonne. While many Electric Induction Furnace units havestarted processing steel melting scrap so that it not only improves the quality of products

but also consumes less power. The other area, which can be improved in Induction Furnacesworking, is in material handling, i.e. materials and also finished goods. Continuous feeding

and heating of raw materials, i.e. Sponge iron and steel melting scrap in the Furnace is usedby many companies in Maharashtra and Gujarat.

Inputs in the Induction Furnaces

Induction Furnaces are using Steel-melting scrap, Sponge Iron & Pig Iron/Cast Irons. On an

average the ratio of these items is 40% sponge Iron + 10% Cast Irons or Pig Iron. The

technology of melting these input materials varies according to the availability of rawmaterials and location of the plant. Quality of products made by Induction Melting Furnacesdepends on the quality of input materials charged in the furnace. The various input

materials used are given below:-

Shredded Steel Melting Scrap - mostly imported from USA Heavy Steel Melting Scrap -mill cut ends or old steel components and some quality

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Light Steel Melting Scrap such as turnings brooding or the steel sheets cutting Old Cans & coated steel sheet cuttings Railway scrap Pig Iron/Cast Iron Direct reduced Iron (Coal based)

Direct reduced Iron (Gas based)

Ship-breaking steel scrapThe shredded Steel scrap is at present considered to be a better input material due to itshigher density and low melting losses. However, it has some tramp elements such as

Copper, Nickel, Chromium, Zinc and Aluminium etc. While Zinc and Aluminium, chromiumgets removed during melting but they make bath sluggish. Copper and Nickel remain in the

metal. Over size steel scrap used need sizing and processing before charging, but very few

units are doing so, thereby tap to tap time is more and Power consumption is higher,Railway scrap is good if it is of Mild Steel. Pig Iron and Cast iron can be used in certain

proportions only. Direct reduced iron ores coal based or gas based has occupied a premier

position in the secondary melting industry. It is a boon to Induction Melting Furnaces. It hasno tramp element and is very low is Sulfur and Phosphorous contents. It is reported that

some Induction Melting Furnace units are using as high as 85% DRI. A judicious blending ofcharge is needed to produce Steel of particular specification to meet quality requirement of

customer/Annexure I gives a guidance of charge-blending etc. Therefore, qualitymanagement for steel production in Induction Melting Furnaces commences from input

material stage. Ship breaking scrap is of Mild Steel and very good for Induction Furnaces.

Quality Management

With such a large producing capacity 8.5 million tonne and estimated production amountingto nearly 16% of Steel semi production in the country, Government of India has now

realized the potential of this sector, which it neglected for over a decade. The industry on itsown has initiated several schemes to meet the challenge it faces in regard to Quality

Management. All the Induction Melting Furnace units have chemical testing laboratory and20% have sophisticated testing equipment for alloying elements by using spectrometers.

They have instruments for gas analysis. Casting units have Ultrasonic testing equipment or

get such castings tested by independent laboratories as per requirement of the customer.Proper testing records are maintained by all Induction Furnace units. Over 30 number of

Induction Furnace units have taken BIS Certification mark. The products of Induction

Furnace units are meeting the BIS Certification mark. The products of Induction Furnaceunits are acceptable to ISRO; BHEL; NTPC; Railways and Defense and other

users/customers. Product of Induction Melting Furnace units is exported to USA; Germanyand other developed countries. It is expected that Induction Melting Furnace industry will in

the next two years have elaborate quality assurance regime.

Quality Control of Low Alloys Special Steels and Stainless Steel made by InductionMelting Furnaces

Electrode Quality SteelSome Induction Furnace units are producing electrode grade steel. The production is

carried out under strict control. The chemical composition of the steel as noted fromthe company's records is as follows: -

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Heat No C Mn Si S P

01 0.037 0.45 0.04 0.020 0.024

02 0.058 0.50 0.03 0.0186 0.019

03 0.04 0.55 0.05 0.020 0.23

04 0.03 0.48 0.03 0.017 0.023

Size of ingots produced is 3 X 4 . All bath sample and final samples are tested

using Spectrometer. The steel produced by this company is acceptable to electrodemanufacturers.

Low Alloy SteelsAt present many Induction Furnace units in India are regularly producing Low alloySteels. These include En18, En19, En24, En8, En9 etc. Size of ingots varies 3 " x 4

" to as much as 6 " x 7 ". So far none of the Induction Furnace units haveproduced these Steels by Concast process but three Induction Furnace units are

installing Ladle Refining and Concast equipment to make Concast billets soon.

Stainless SteelsInduction Melting Furnaces before making Mild steel ingots started producing

stainless steel since 1979-80 period using small size induction furnaces. The rawmaterial was imported stainless scrap of 304 grade. At present stainless steel is

produced by (a) melting SS scrap and casting ingots by gas purging the liquid metalin ladle, adding alloying elements etc. and (b) melting Mild steel scrap and adding

ferro alloys and transferring the liquid metal to AOD vessels for refining. After AOD

treatment some units carry out further refining in LRF and then producing billet byconcast process. All units having Ladle refining system have installed spectrometerfor quicker bath analysis. Gas levels such as N, H & O are also determined by the

newly installed instruments. Most of the induction furnace units are producingutensils grade stainless steel. Two induction furnace units making SS have exported

bars and rods and forged flanges. More and more Induction furnace units are

modernizing as well as diversifying to value added products.

Grinding MediaFive Induction Melting Furnace units are producing Grinding Media on Mncr5; 20

MnCr5, etc. located at Ghaziabad, Jhansi, Ahmedabad, Mumbai and Bangalore and

exporting. It meets the quality requirement of World standard.

Production of Steel & Alloy Steel CastingsAt least 40 Induction Melting furnace units are producing steel castings for Railways,

Sugar Mills, Tractor units and Machine tool companies. Four Units are producing heatresistant casting. The metallurgical tests are carried out as per specification,

Ultrasonic testing, water Pressure test, tensile testing etc. Such units have all in-house testing equipment to control quality of products. More and more induction

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furnace units are going for special steel castings. At least five induction furnace unitsare exporting steel & alloy steel castings.

Special Cast Iron & Sponge Iron CastingsWhile many cast iron casting foundries have installed Mains Frequency Induction

Furnaces to make quality cast irons, some have installed Medium FrequencyInduction Furnaces to make SG Iron. These foundries have chemical testing, Sand

testing and Physical testing equipments along with Ultrasonic testing equipments. Itis learnt that these Induction furnace units have exported special cast iron & S G

Iron castings worth Rs. 350/- crore in 1997-98.

Micro-Alloy Structural SteelIt was felt that Induction Melting Furnace industry should develop Micro-Alloystructural steels. This idea was mooted by AIIFA and the development project was

given to National Institute of Secondary Steel Technology (NISST), which prepared afeasibility report submitted to Ministry of Steel, Government of India in 2002. A sum

of Rs. 4.0 lakh was granted by the ministry for this project. The melting & rolling hasbeen completed. The Micro-Alloy Steel was produced by varying additions of

vanadium, niobium and titanium for rolling 12 mm bars was carried out. Physical andChemical tests were done. The semis of 12 mm bars so produced were made in

normalized condition. Some were water quenched. The 12 mm bars produced withabout 0.04% vanadium with carbon content nearly 0.25% was having strength and

ductility superior to TMT bars in normalized condition. Mass production is beingcarried out. AIIFA is, therefore, taking up R&D projects to help the Induction Furnace

industry.

Present Scenario

After 2 years of depressed market the steel market suddenly showed competitiveness. It isnoted that induction-melting furnaces in various parts of the country are at presentoperating to near full capacity depending on power availability. However, the power is not

supplied to the units fully. Against a capacity of 8.5 million tonne in the year 2003-04, the

induction furnaces are likely to produce nearly 5.2 million tonne of mild steel ingots. Theproduction of stainless steel may also be 3.5 lakh tonne. There are nearly 890 units of

induction melting furnaces installed in various parts of the country and laboratories toproduce cast iron, special cast iron, mild steels stainless steels and high & low alloy

castings. There are nearly 650 induction furnaces installed in the country to manufacturethe mild steel and stainless steel. Out of this nearly 560-induction furnace units are in

operation at present.

Due to demand of steel increased during the last one year, Mini Integrated steel plants are

come up in some states of India. These plants, according to our information have beeninstalled at Durgapur zone in West Bengal, Chhattisgarh, Jharkhand , and in a big way in

Orissa. The route followed by these units are to have sponge iron plant, use sponge iron inmelting it in induction melting furnaces of various capacities using Waste gas of sponge iron

kiln in generating Power and use it in melting Sponge Iron and Steel melting scrap. Themolten metal is put in Concast continuous machine and produce billets. According to our

information nearly 1 million tonne of steel is being produced by this route. It is expected

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that this system of manufacturing steel by this Mini Integrated Steel Plants will shortlypresent a scenario totally new.

It is also noted that many units are installing furnaces of 16 tonne per charge to 22 tone per

charge. Induction melting furnaces use over 60% sponge, and have iron installedmechanical devises to remove slag, then use LRF to make better quality steel. The refined

steel will be poured in the Concast machine to produce steel billets. Revolution is takingplace to make steel in India by utilizing various technologies. India is therefore, emerging asa country with innovative idea to make steel, which is not followed by other countries in the

world. Our technologists are at present exporting this technology to various countries inAsia and Africa.

ANNEXURE - I

THE DATA IS FOR A 3 TONE MEDIUM FREQUENCY INDUCTION FURNACES

SL.NOGENERAL SCRAP USED

CHARGE MIX

24 HR.

WORKINGNO.OF HEATS

LINING

LIFE PERTONNE

POWER-KwhCONSUMPTION

01 80% sponge iron + MixedScrap

09 40 heats 820 Units

02 50% sponge iron or more10% CI & mixed scrap

12 50-65 heats 760 Units

03 30% HMS + 30% sponge&rest mixed scrap + CI

13 60-75 heats 700 Units

0430% HMS + rest loose mixedscrap

1490-100heats

700 units

0515% LMS bundle + 15%turning bundle + 50% HMS

+ rest mixed scrap

14-15 100-125heats

690 Units

06

15% LMS bundle + 30%turning bundle + 40%shredded scrap+ rest mixed

scrap

15 100-125heats

670 Units

07

15% LMS bundle + 15%

turning bundle + 40%shredded scrap + 20% HMS

+ rest mixed scrap

15-16 100-125

heats

650 heats

08

15% HMS bundle + 15%

turning bundle + 60%shredded scrap + rest mixed

scrap

15-16 100-125

heats

650 Units

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Electric Steel Making Technology in the 21st Century

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