Nickel & Special HT steels Petrochemical applications · Mat. No. EN Designation Ni Cr Fe C Al Ti...

Nickel & Special HT steels

Petrochemical applications

UTP SchweissmaterialApplication Technology

2 | UTP Schweissmaterial | Nickel for HT applications I June 2012

Requirements of petrochemical processes

Base material selection

Welding consumables for petrochemical appliances

Examination of long-term behaviour of welding consumables

Other aspects to be considered

Contents

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Summary6


Source: howstuffworks.com

Oil processing in refinery

• Distillation takes place at different temperature and pressure levels.

• E.g.: Ammonia synthesis at 100 bar and 600°C

• Therefore, petrochemical plants are composed of different base metals.

• An oil refinery is a combination of all these units.



Temperature: from RT up to 1200°CPressure: up to 600 bar



In order to guarantee reliable and safe processing conditions, base materials and welding consumables are selected to fulfil the following requirements:

Oxidation resistance

Carburisation resistance

Low embrittlement tendency

Creep rupture strength







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0

Temperature °F

392

752

1112

1472

1832

2192

600°C

700°C

1050-1100°C 900-1200°C

high-temperature

resistant

CrMo

steels

stainless

steels

centrifugal

casting

CrNi

alloys

NiCr

alloys

X20CrMoV121

X6CrNi1811ASTM A240 304H

X6CrNiMo1713ASTM A240 316H

G-X40CrNiSi2520ASTM A531 GradeHK40

G-X40NiCrNb3525ASTM A297 HP40

X10NiCrAlTi3220

NiCr15Fe

NiCr22Mo9Nb

NiCr23Fe

NiCr23Co12Mo

X5NiCrCeNb3227X10CrMoVNb91

NiCr25FeAlY

Operating temperatures for different materials


Iron Base AlloysChemical composition

Main alloying elements in wt %

Material

No.EN Designation

ASTM

DesignationNi Cr Fe C Nb Si Others

1.4859 GX10NiCrNbSi32-20 CT 15C 32 20 R 0,10 1,0 1,0 Mn<2,0

1.4848 GX40CrNiSi25-20 HK 40 20 25 R 0,40 1,8 Mn<2,0

1.4857 GX45NiCrSi35-25 HP 40 34 25 R 0,4 1,8 Mn<2,0

1.4868 GX50CrNiSi30-30 30 30 R 0,5 1,8 0,5<Mn<1,5

1.4889 GX45NiCrNbSiTi45-35 35/45 45 35 R 0,45 1,7 1,8 Mn < 1,5

Chemical composition of iron-base alloys


Nickel base alloysChemical composition

Main alloying elements in wt %Common

name

UNS

No.

Mat.

No.

EN

DesignationNi Cr Fe C Al Ti Others

Alloy 601 N06601 2.4851 NiCr23Fe R 23 16 0,08 1,4 0,4

Alloy 602CA N06602 2.4633 NiCr25FeAlY R 25 9,5 0,2 2,1 0,140,08%Y

0,07%Zr

Alloy 600 L N06600 2.4817 LC-NiCr15Fe R 15 8 <0,025 <0,3

2.4815 G-NiCr15 R 15 22 0,5

NA22H 2.4879 G-NiCr28W R 29 11 0,45 4,5%W

Alloy 625 N06625 2.4856 NiCr22Mo9Nb R 22 < 3 <0,0259%Mo

3,5%Nb

Alloy 617 N06617 2.4663 NiCr23Co12Mo R 22 < 2 0,05-0,1 1 0,49%Mo

12%Co

Alloy 657 2.4680 G-NiCr50Nb R 50 <1,0 <0,11,5%Nb

0,15%N

Chemical composition of nickel-base alloys


Requirements for high-temperature alloys


Carburising resistance

Low embrittlement tendency

Creep rupture strength


Oxidation

In order to reduce oxidation rate, you need elements which hinder the diffusion of O2 inside the material and which have a high affinity to O2

(e.g. Al, Si, Nb)

Influence of alloying elements:

Cr > 25 %; higher Cr content stabilizes oxide films but causes sigma phase

Ni has a beneficial effect on cyclic oxidation

Higher Si-content promotes oxidation resistance, esp. bonding of oxide layer

Rare earth elements enhance oxide stability


Chemical composition

Main alloying elements in wt%Common

nameNi Cr Fe C Al Ti Others

Alloy 601 R 23 16 0,08 1,4 0,4

Alloy

602CAR 25 9,5 0,2 2,1 0,14

0,08%Y

0,07%Zr


Comparison of corrosion attack on Nicrofer 6023 H (alloy 601) and Nicrofer 6025 HAT (alloy 602 CA) after 1000 h at 1200°C (2192°F) in air

Chipped-off material

Chipped-off material

Initia

l dimensio

n



Test medium: Air

Air temperature: 1200°C

Time: 1000 hrs


Mechanism of carburization

Decomposition of hydrocarbons creates free carbon, which diffuses through the grain boundaries into the material.

Carburization increases with rising temperature;The rate roughly doubles for every 38°C tube metal temperature increase.

Consequences of carburization:

� Decrease of melting point� Carbide formation with chromium depletion� Loss of ductility due to carbide formation


Inc

rea

se i

n c

arb

on

[%

]

Carburized at temperature for

260 hours in carbon granulate

HK-40

25/20

HP-45

25/35 mod.

35/45

1800 1900 2000 2100

Temperature

[°C]

[°F]

950 1050 1150

3,5

3,0

2,5

2,0

1,5

0,5

0,0

1,0

Carburization

Increase of alloy carburization under rising temperature


Carburization

There are

numerous & complex

factors:

Cr, Ni and Si are

effective barriers

Synergistic additions of

W, Nb, Ti and Zr

considerably improve

resistance to carburization


Creep behaviour

Creep is the tendency of a solid material to slowly deform

permanently under the influence of stresses (and temperature).

Strengthening mechanisms against creep:

Solid solution hardening (Cr, Mo, Co, W)

Precipitation hardening (Al, Ti, Nb)

Formation of carbides (Ti, Nb, V, B)

Manipulation of grain size (coarse / fine)

Purity to trace elements


Metallographic explanation for creep behaviour

Microstructure of alloy 800H

after 33470 h, 650°C (1202°F), 11 N/mm².

On the grain boundaries,slight formation of chromium carbidesvisible, grain size about 170 µm,Initially: 140 µm

Mag. 500:1

Microstructure of alloy 800H

after 25760h, 850°C (1562°F), 1.8 N/mm².

On the grain boundaries,agglomeration of carbides, the grains have grown,grain size about 220 µm

Mag. 500:1


They should be still weldable!

Requirements for high-temperature alloys


How to weld these

materials - similar

or dissimilar?







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Iron Base Metals Filler metalChemical composition

Main alloying elements in wt %Material No. EN Designation ASTM Des. C Si Cr Ni Nb Others

1.4859 GX10NiCrNbSi32-20 CT 15C 0,1 1 20 32 1 Mn < 2.0

UTP 2133 Mn 0,14 0,3 21 33 1,3 4,5 % Mn

1.4848 GX40CrNiSi25-20 HK 40 0,4 1,8 25 20 - Mn < 2.0

UTP 2535 Nb 0,4 1 25 35 1,2 1,5 % Mn

1.4857 GX45NiCrSi35-25 HP 0,4 1,8 25 34 - Mn < 2.0

UTP 2535 Nb 0,4 1 25 35 1,2 1,5 % Mn

1.4889 GX45NiCrNbSiTi45-35 35/45 0,5 2 35 45 2 Mn < 1.5

UTP 2535 Nb 0,45 1 35 45 0,9 0,8 % Mn

UTP welding consumables for Fe-base alloys


Nickel base alloys Filler metals Chemical composition

Main alloying elements in wt %

Common name Material No. EN Designation Ni Cr Fe C Al Ti Others

Alloy 601 2.4851 NiCr23Fe R 23 16 0,08 1,4 0,4

UTP 6225 Al R 25 10 0,8 1,8 0,10,08%Y; 0,07%Zr

Alloy 602CA 2.4633 NiCr25FeAlY R 25 9,5 0,2 2,1 0,140,08%Y; 0,07%Zr

UTP 6225 Al R 25 10 0,8 1,80,08%Y; 0,07%Zr

Alloy 600 L 2.4817 LC-NiCr15Fe R 15 8 <0,025 <0,3

2.4815 G-NiCr15 R 15 22 0,5

UTP 7015 Mo R 16 6 0,046,2%Mn2,2%Nb

NA22H 2.4879 G-NiCr28W R 29 11 0,45 4,5%WUTP 2949W R 29 15 0,45 4,5%W

Alloy 625 2.4856 NiCr22Mo9Nb R 22 < 3 <0,0259%Mo; 3,5%Nb

UTP 6222 Mo R 22 1,5 0,033,3%Nb9%Mo

Alloy 617 2.4663 NiCr23Co12Mo R 22 < 2 0,05-0,1 1 0,49%Mo; 12%Co

UTP 6170 Co R 21 1 0,6 0,7 0,39%Mo12%Co

Alloy 657 2.4680 G-NiCr20Nb R 50 <1 <0,11,5%Nb0,15%N

UTP 5848 Nb R 50 - <0,1 1,5%Nb

UTP welding consumables for Ni-base alloys


Creep strength

Creep rupture strength and high-temperature plastic deformation are the key properties to determine the tube wall thickness. The design is usually made for 100,000 hours of service life.

Cr and C control the rupture strength through carbide formation.

Nb is a solid solution strengthener as are W and Mo.

Nb and additions of Ti and Zr produce extremely fine carbides and participate in the formation and strengthening of the alloy (temperature-stable carbides).







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Creep strength

To increase the working temperature of a weld material,

TÜV requests creep strength values after

minimum 30,000 hrs at different temperatures.


Testing of creep strength

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2

3

4

Plate after welding

1 – sawn plate

2 – prepared specimen

3 – ready specimen

4 – tested specimen1000°C (1832°F), 1071 hrs, 10 N/mm2


Testing of creep strength

Specimen in test


Embrittlement behaviour

Embrittlement tendency is checked after ageing

at different temperatures by Charpy impact test.


Testing of embrittlement behaviour

Plate after welding Plate in oven


Testing of embrittlement behaviour

1

2 3

1 – plate machined2 – after 10,000 hrs, 950°C3 - machined

UTP 068 HH10,000 hrs, 950°Cafter testing


time [ h ] test temperature: RT

Av ( ISO-V ) [ J ]

1 10 100 1.000 10.000

0

50

100

150

200

750°C850°C

550°C

650°C

950°C

100.000

Embrittlement behaviour

Ageing of E NiCrFe-2(UTP 7015 Mo)







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200 300 400 500 600 700 800 900

the

rma

l ex

pa

ns

ion

co

eff

icie

nt

.

temperature °C

m

m x

grd

x 1

0-6

Alloy 625

1.4859

alloy 800H

UTP 2133Mn

C-steel

Thermal expansion coefficient



Base material: Manaurite 36X(25Cr 35Ni Nb)







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Summary

For high-temperature application use welding consumables with similar chemical composition to match the properties of the base metal.

Creep strength plays a key-role in the development of welding consumables.

Corresponding expansion coefficients are also important for the structure lifetime.

Qualification of BWG welding consumables is crucial to meet high quality requirements.

These filler metals are available for SMAW and GTAW.


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Nickel & Special HT steels Petrochemical applications · Mat. No. EN Designation Ni Cr Fe C Al Ti...

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