Low alloy CrMo(V) petrochemical reactors · • conventional CrMo steels: ASTM A387 Gr.11 Cl 1 and 2 or Gr. 22 Cl. 2 or ... Low alloy CrMo(V) steel plates for petrochemical reactors

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Low alloy CrMo(V) steel plates for petrochemical reactors 1

LowLow alloyalloy CrMo(V)CrMo(V) steelsteel platesplates forforpetrochemicalpetrochemical reactorsreactors

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1. Introduction

2. Application trends

3. Requirements for CrMo(V) steels

4. Heat treatment - Hollomon parameter

5. General material behaviour and feasibility investigations

6. Long term embrittlement and avoidance strategies

7. The benefits of modern CrMoV steels

8. General recommendations for processing: forming+welding

9. Creep properties

10. Conclusion

Content

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Introduction

conventional CrMo steels: ASTM A387 Gr.11 Cl 1 and 2 or Gr. 22 Cl. 2 or 13CrMo4-5 or 10CrMo9-10 acc. EN 10028 part2

enhanced CrMo steels: quenched and tempered steels with increased mechanical properties, e.g. ASTM A 542A/B 3/4/4a or 12CrMo9-10 acc. EN 10028 part 2

new generation of CrMo steels: Vanadium modified CrMo-steels, e.g. ASTMA542 D4a or 13CrMoV9-10 acc. to EN 10028 part 2.

Wherever high temperatures and/or high hydrogen partial pressures in the processes are required, CrMo steels have been used for more than 50 years. Due to changing process parameters in chemical and petrochemical processes these steel grades have been developed to enhanced properties.

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1Cr Mo ASTM/ASME A/SA 387-12-1/2EN 10028-2: 1992 13CrMo4-5EN 10028-2: 2003 13CrMo4-5

1Cr Mo ASTM/ASME A/SA 387-11-1/2EN 10028-2: 2003 13CrMoSi5-5

2Cr 1Mo ASTM/ASME A/SA 387-22-1/2A/SA 542-A/B-3/4/4a

EN 10028-2: 1992 10CrMo9-1011CrMo9-10

EN 10028-2: 2003 10CrMo9-1012CrMo9-10

2Cr 1Mo V ASTM/ASME A/SA832-22VA/SA 542-D-4/4a

EN 10028-2: 2003 13CrMoV9-10

3Cr 1Mo V ASTM/ASME A/SA832-23VA/SA 542-E-4/4a

EN 10028-2: 2003 12CrMoV12-10

A broad variety of CrMo(V) steels is commercially available

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200

300

400

500

600

700

800

0 50 100 150 200 250

Hydrogen partial pressure [bar]

Tem

pera

ture

[C

]

6%Cr, 0,5%Mo

3%Cr, 0,5%Mo V

2,25%Cr, 1%Mo, V

2,25%Cr, 1%Mo

1,25%Cr, 0,5%Mo1%Cr, 0,5%Mo

Carbon steel

1%Cr, 0,5%Mo

acc. API 941, 1997

Nelson-curves

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Application and trends for the use of CrMo(V) steels

typical applications are hydrotreating reactors

operating temperatures up to 480 C

hydrogen partial pressures up to 180 bar or even more

Trends:

ever bigger and heavier reactors (already more than 1000t per unit)

higher operating temperatures and pressures resulting in higherwall thicknesses

increasing demand due to expansion or new construction of plants

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Developments in different aspects between 2000 and 2008

Example: 2Cr1Mo steels

dramatic increase of deliveries deliveries in thickness over 100mm

were increased even more than the overall deliveries for these grades

deliveries in N+AC+T conditionwere also increased dramatically

market is very tight as demand isfast rising and only few manufac-turers are able to meet the very high quality standards requested

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Factors contributing to more sophisticated steel plates

strong safety requirements for core units designed from CrMo(V) steels increasing thickness with high demand in thickness over 100mm larger dimensions to allow for more freedom in vessel design PWHT requirements including 3 or often even 4 cycles chemical restrictions exceeding those of the standards specifying J- and X-factor for ultra clean steels specifying toughness values at low temperatures in combination with PWHT additional requirements in regard to grain size hardness requirements specifying step cooling test additional tensile test at elevated temperatures ...

Many additional requirements; partly interfering each other

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CrMo-plate delivery dimensions of Dillinger Htte GTS

Maximum thickness is often limited by requirements from specifications

0

25

50

75

100

125

150

175

200

225

250

1.500 1.750 2.000 2.250 2.500 2.750 3.000 3.250 3.500 3.750 4.000 4.250 4.500 4.750 5.000 5.250

N + AC + T( Q + T)

N + T

up to 28 t

up to 37 t

depending on grade & thickness up to 37 t

upon agreement

up to 42 t

up to 37 t

width [mm]

thic

knes

s [m

m]

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Common additional requirements for different CrMo(V) grades

> 100 mm

Ch-V + PWHT

Step CoolingHardness

J- / X-Factor

1Cr Mo1Cr Mo2Cr 1Mo2Cr 1Mo V

100 %

80 %

60 %

40%

20%

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Concept of the Hollomon-Parameter (HP)

The metallurgical effect of tempering and PWHT on the mechanical properties of steel can be combined by the HP-Parameter (T

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Description of a heat treatment cycle by the Hollomon Parameter:

Time [h]

Tem

pera

ture

[C

]

t +

holding

T Holding

Temperature[C]

[HP = T (+ 273) log ( T (+ 273) 2,3 * Kh ( 20 - log Kh )

heating

Kh heating rate

[C/h]

2,3 * Kc ( 20 -log Kc )

T (+ 273) ) + 20 ] * 10 -3

cooling

Kc cooling rate

[C/h]

t Holding time

[h]*

*) holding time starts whenreaching temperatureover the whole cross section

+

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Tempering PWHT HP700C/300Min. 20.15700C/250Min. 670C/180Min. 20.15680C/250Min. 680C/600Min. 20.15680C/60Min. 690C/300Min.+700C/90Min. 20.15680C/60Min. 675C/600Min.+680C/300Min. 20.15

Equivalence of Tempering and PWHT on Hollomon Parameter:

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General influence of heat treatment on mechanical properties

AfterPWHT

Av,

Rm

, Rp0

.2

Hollomon parameter

HB before

HB after

BeforePWHT

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Tensile strength in dependence of HP for CrMo and CrMoV steels

500

600

700

800

900

1000

1100

19,00 19,20 19,40 19,60 19,80 20,00 20,20 20,40 20,60 20,80 21,00 21,20 21,40

Rm

[MPa

]

400

HP

12CrMo 910 acc. EN 10028-2:2003

CrMoV: acc.SA 542-D-4a

2,25CrMoV, t/42,25CrMoV, t/23CrMoV, t/43CrMoV, t/212CrMo 910

HP 20,8: Tempering+705 C/10h


thickness: 200 mmcondition: N+AC+T

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Yield strength for CrMo and CrMoV steels

19,2 19,4 19,6300

400

500

600

700

800

900

1000

19 19,8 20 20,2 20,4 20,6 20,8 21 21,2 21,4HP

Rp0

2[M

Pa]

12CrMo 910 acc. EN10028-2:2003

2CrMoV, t/42 CrMoV, t/23CrMoV, t/43CrMoV, t/212CrMo 910 (2CrMo)

CrMoV acc. SA 542-D-4a



thickness: 200 mmcondition: N+AC+T

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HP

0

50

100

150

200

250

300

350

400

19,00 19,20 19,40 19,60 19,80 20,00 20,20 20,40 20,60 20,80 21,00 21,20 21,40

Cha

rpy-

V-tr

ansv

erse

,A

vm

ean

[J]

2CrMoV, t/4

3CrMoV, t/4

12CrMo 910 (2CrMo)

test temperature: -60C

CH-V-results vs HP compared between CrMo and CrMoV steels

thickness: 200 mmcondition: N+AC+T test location: t/4

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General observations when dealing with transition curves

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SA 387-11-2: Feasibility in dependence of HP, Rm, Re, Ch-V, hardness and plate thickness of 1Cr steel

0 20 40 60 80 100 120 140 160 180 200

plate thickness [mm]

Hol

lom

on p

aram

eter

0 20 40 60 80 100 120 140 160 180 200


Hol

lom

on p

aram

eter

195 HB

200 HB

205 HB

210 HB

215 HB

220 HB

225 HB

220

HB

210

HB

205

HB

200

HB

195

HB

-29 C

-18 C0 C

0 C

-18 C

-29 C

N+AC+T

N+T

(Q + T)

N+AC+T(Q + T)

N+T

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SA 387-22-2: Feasibility in dependence of HP, Rm, Re, Ch-V, hardness and plate thickness of 2Cr steel

0 20 40 60 80 100 120 140 160 180 200


Hol

lom

on p

aram

eter N+AC+T

- 40 C

- 18 C & -29 C

0 20 40 60 80 100 120 140 160 180 200


Hol

lom

on p

aram

eter

- 29 C

- 18 C

- 10 C

N+T(Q + T)

195 HB

200 HB190 HB200 HB

N+AC+T

205 HB

N+T 205 HB

195 HB

210 HB

215 HB

210 HB

215 HB

(Q + T)

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Offset in hardness between 2CrMo and 2CrMoV steels in dependence of delivery condition

180

190

200

210

220

230

240

250

2CrMo 2CrMoV

hard

ness

[HB] Q + T

10h @ 705 C

Q + T

Q + T30h @ 705 C

Q + T5h @ 700 C

N + AC + T(Q + T)

Actual hardness distribution is depending on the steel design necessary to fulfillthe overall requirements of the specification

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Aspects of interchangeability between 2Cr and 1Cr steels

-29 C

-29 C

-29 C

-40 C

2Cr N+T2Cr Q+T1Cr N+T1Cr Q+T

Hol

lom

on P

aram

eter

1CrMo Specs reflect more and more the attempt to replace 2Cr1Mosteels

generally the 1Cr steels show a different toughness behaviour

interchangeability is limited for different PWHT conditions andhigh thickness

not only mech-tech properties butalso other restrictions by the codeslike e.g. listing in the Nelson curvesare of importance

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Tensile- and yield strength of enhanced 2CrMo steels (N+AC+T)

300

400

500

600

700

800

900

1000

19,8 20,0 20,2 20,4 20,6 20,8 21,0 21,2HP-Factor

Rp0

,2re

sp. R

m[N

/mm

2 ]

Rp0.2

Rm

12CrMo9-10

12CrMo9-10

12CrMo9-10

Thickness > 200 mm

Tempering740 C/30

PWHT-Max690 C/24h

PWHT-Min690 C/8h

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Tensile- and yield strength of enhanced 2CrMo (V) steels (N+AC+T)

300

400

500

600

700

800

900

1000

19,8 20,0 20,2 20,4 20,6 20,8 21,0 21,2HP-Factor

Rp0

,2re

sp. R

m[N

/mm

2 ]

Thickness > 200 mm

Rm V-modified

Rp0.2 enhanced

Rm enhanced

+ 0,

25%

V

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300

400

500

600

700

800

900

1000

19,8 20,0 20,2 20,4 20,6 20,8 21,0 21,2HP-Factor

Rp0

,2re

sp. R

m[N

/mm

2 ]

Thickness > 200 mm

Rm V-modified

Rp0.2 enhanced

Rp0.2V-modified

+ 0,

25%

V

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300

400

500

600

700

800

900

1000

19,8 20,0 20,2 20,4 20,6 20,8 21,0 21,2HP-Factor

Rp0

,2re

sp. R

m[N

/mm

2 ]

Thickness > 200 mm

Rm V-modified

Rp0.2V-modified

A542-D-4a

A542-D-4a

A542-D-4a

Tempering715 C/250

PWHT-Max705 C/24h

PWHT-Min705 C/8h

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Estimated impact toughness of enhanced 2CrMo(V) steels (N+AC+T)

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200

300

400

500

600

0 50 100 150 200 250 300 350 400 450 500 550 600 650

Testing temperature [C]

2,25CrMoV, Rp02

3CrMoV, Rp02

12CrMo 910, Rp02, HP=21,0

12CrMo 910 acc. EN 10028 part 2

Rp0

,2[M

Pa]

300

400

500

600

700

0 50 100 150 200 250 300 350 400 450 500 550 600 650

Testing temperature [C]

2,25CrMoV, Rm

3CrMoV, Rm

12CrMo 910, Rm, HP=21,0

Rm

[MPa

]

Hot tensile properties (transverse, 1/4 thickness)

- plate thickness: 200 mm - heat treatment: N+AC+T

- plate thickness: 200 mm - heat treatment: N+AC+T

2CrMoV acc. EN 10028 part 2

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Hot tensile properties (transverse, 1/4 thickness)

300

350

400

450

500

550

600

0 50 100 150 200 250 300 350 400 450 500 550 600 650testing temperature [C]

Rm

, Rp0

.2[M

Pa]

plate thickness: 200mmheat treatment: N+AC+T

2CrMoV, Rm

2CrMoV, Rp0.2

3CrMoV, Rm2CrMo, Rm ,HP=21.0

3CrMoV, Rp0.22CrMo, Rp0.2 ,HP=21.0

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Notes to Table U (like table Y1 also) state clearly:

values given are for calculating purposes only ASME doesnt require any hot tensile testing for production material If tests are performed, obtained values shall not be compared to tabulated values of table

U for acceptance / rejection purposes

Tensile testing at elevated temperatures - notes to ASME II D

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Comparison of real data and calculation values of ASME II DASME II D Table U: Tabulated values for calculation vs. measured values

300

350

400

450

500

550

0 100 200 300 400 500 600

Temperature [C]

Tens

ile s

tren

gth

[MPA

]

HP 20,63

HP 20,81SA 387-11-2SA 387-22-2

Rm,T tabulatedRm,T tabulated

SA 387-22-2, measuredRm min20 C

SA 387-22-2, measured

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ASME II D tables U and Y1 tabulated vs. measured

150

200

250

300

350

400

450

500

550

100 150 200 250 300 350 400 450 500 550 600

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Comparison of test results with Table U data for different grades

300

350

400

450

500

550

600

650

0 100 200 300 400 500 600

Temperature [C]

Tens

ile s

treng

th [M

Pa]

SA 387-22-2SA 542 D4aSA 542 C4atest datatest datatest data

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Basic connections between carbon content, tensile strength

and toughness behaviour (unalloyed steel SA 516-70)

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Low contents of As, Sb, Sn and P for improved temper embrittlement behaviour

temper embrittlement usually occurs in the temperature range between 370 and 580 C

tramp elements like P, Sn, Sb and Ascause this phenomenon

J-factor and X-factor are commonly used as additional specification criteria

modern steels with very low contents oftramp elements show no obvious correlation between J-/X-factor and embrittlement any more

for 2CrMo(V) steels usually the step cooling test is used toinvestigate the proneness totemper embrittlement Intergranular crack

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peration of installation(~30 years) 400 COperation of installation

(~30 years) 400 C

Temper EmbrittlementCrack

high safety

without danger of

grain-boundary

embrittlement!

PAsSb

Conclusion:

aim for low content of embrittling tramp elements specify J- value, X- value

LD- Route + special steel refining adventageous,due to less tramp elements compared to EA process

specify Step-cooling

The mechanism of temper embrittlement

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J-factor X-factor J-factor X-factor

1Cr Mo 120 13 100 9

1Cr Mo 165 13 120 9

2Cr 1Mo 130 13 100 ** 9

normal production special production

Intergranular cracking and recommendations for avoidanceStrategies to avoid temper embrittlement

aim for low content of embrittlingtramp elements

specify J-factor, X-factor

LD- Route (Basic Oxygen Furnace) + special steel refining is adventageouscompared to electric arc process, due to less tramp elements

specify Step-cooling test

X- (Bruscato) Factor = (10P + 5Sb + 4Sn + As)/100J- (Watanabe) Factor = (Mn + Si)(P + Sn)104

normal production special production

P 0,011 0,006 resp. 0,007*

Sn 0,005 0,005

As 0,007 0,007

Sb 0,001 0,001

Special production: higher cost

* depending on Cr-content

** 80 for 2CrMoV

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Achievable P-contents as function of Cr-content for various process routes

A

B

C

250

200

150

100

50

00 1 2 3

Cr-content [%]

[C]0.13 %

[Si]0.25 %

[Mn]0.60 %

[Mo]1.00 %

[Tliq]~1560C

1.5 2.5 3.50.5

Aim

edP-

cont

ent[

ppm

]conventional process

special converter processconventional process with heating in VD units

ABC

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80

70

60

50

40

30

20

10

0

EAF with 70 % alloyed-rejects srap + ferrous alloysEAF with sheet-metal scrap + ferrous alloysLD-steel BOF process

Arsenic (As) Tin (Sn) Antimony (Sb)

Mas

sco

nten

tin

ppm

Comparison of the tramp elements between EAF and LD-steelmaking

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Ductility vs. Charpy notch toughness for 2CrMo

Ductility and Charpy-values taken from randomly picked Dillinger orders in SA 387-22-2 at different temperatures. Plate thickness 134 & 208 (G&B) mm

0

50

100

150

200

250

300

350

400

0 10 20 30 40 50 60 70 80 90 100

Ductility [%]

Av

[J]

0 C -20 C -30 C -40 C -60 C -80 C -100 C

Test location: t/2

A ductility requirement of 50% minimum would correspond to a toughnesslevel of 140 to 150 J ductility value is usually offered for information.A slight decrease in toughness due to higher thickness can be observed

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Requiremnets of low Oxygen

Dillinger Htte offers 30ppm max. of total oxygen Ogygen is supposed to have a moderate negative impact on toughness, formability and machineability the higher oxygen content DH offers results from the requirement of low phosphorus to avoid embrittlement, which seems to be the

main issue for these steels (keep J-factor low)

low phosphorus steels produced by the BOF route have to undergo a special additional treatment, which leads to a higher oxygenlevel of the heat, when entering the vacuum degasser

during vacuum treatment it cannot be guaranteed in all cases that oxygen can be removed to the level obtained for normal production.

The large majority of the steels will have max. 15 ppm after vacuum degassing, but some heats wont show this amount due to production risk restrictions given by the management DH only offers max. 30ppm of oxygen

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Cumulative Oxigen content (example)

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aftercleanness

stirring

tundish mould plate0

10

20

30

40

50

60

[O]

in p

pmto

t

aftervacuum

treatment

after CaSi-addition

10

0 5 10 15time in min

0

20

30

40

50cleanness stirring with 100 l Ar/min

O in

ppm

tot

Development of [O]tot during production for continous casting and without special converter treatment

Steps after vacuum treatment are still very important to bring total oxygen further down

after inclusionshape control

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Step cooling - impact transition curve

after service

test temperature

impact energy initial

after step cooling

TTSCSC

TTtottot

54 JTTtottot = 2.5 x TTSCSC

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Step cooling - heat treatment

step-cooling-treatm ent inaccordance to EN 10028-2

59 3 C

53 8 C52 4 C

4 9 6 C

4 6 8 C

2,8C/h

5,6C/h

3 15C

2,8C/h

3 15C

250

300

350

400

450

500

550

600

0 1 2 3 4 5 6 7 8 9 10 11 12

tim e [d]

tem

pera

ture

[C

]

55,6C/ h

15 h24 h

60 h100 h

1 h

test duration approx. 12 days + mechanical testing (including specimen preparation)

cooling in still air

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Step cooling on base metal - results

-20

-10

0

10

20

30

40

50

60

-140 -120 -100 -80 -60 -40 -20 0 20

TT54J before Step Cooling [C]

T

afte

r Ste

p C

oolin

g [K

]Q+AN+A

TT + 2.5 xT

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Step cooling on base metal - results

-20

-10

0

10

20

30

40

50

60

-140 -120 -100 -80 -60 -40 -20 0 20


T

aft

er S

tep

Coo

ling

[K]

Q+AN+A

TT + 2.5 xT

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Advantages of Vanadium enhanced steels

Higher strength / lighter weight reactors Improvement in temper embrittlement susceptibility Greater resistance to hydrogen attack (higher temperatures/H2 partial pressures are permissible)

Greater resistance to hydrogen embrittlement Greater resistance to weld overlay disbonding

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Benefits for CrMoV steels when applied, calculating exemple outer Diameter: 3.400mm

overall height: 36.000mm

design pressure: 170 bar

calculation based on some simplifications

allowable stress[MPa]

resulting wall thickness

[mm]

resulting weightof the vessel

[t]

allowable stress[MPa]

resulting wall thickness

[mm]

resulting weightof the vessel

[t]

2CrMo Div. I 129 214 616 103 263 757

2CrMoV Div. I 145 192 553 140 199 572

2CrMo Div. II 151 185 533 117 234 674

2CrMoV Div. II 169 167 480 163 172 497

2007 Edition

2CrMo Div. II 151 185 533 117 234 674

2CrMoV Div. II 199 143 413 163 172 497

design temperature 454 C design temperature 482 C

Material ASME VIII

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Summary of parent material properties

12CrMo9-10: The tensile and toughness properties are satisfactory in a HP-range between 19.6 and 20.8

CrMoV-steels: In spite the higher tensile requirements HP-values up to 21.1 are acceptable

CrMo(V)-steels: Impact toughness increase by tempering effect until an optimum HP value isreached.

Good toughness reserves even for high HP-values

Know-How about mechanical properties in dependence of HP and deliverycondition is the basis of the optimum steel design and safe production

Even for the high plate thickness:

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Dillingers experience in processing CrMo(V) steels Dillinger Htte GTS regularly processes CrMo(V) steels in its Heavy Fabrication Division the scope of work comprises forming and welding of components for pressure vessels

out of CrMo(V) steels, i.e. - cold or hot* forming by roll bending or pressing- longitudinal welding of shell courses- forming of heads in the pressing shop( *after hot forming the parts will be heat treated as per the material standard)

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Cold forming - Dillinger Httes roll bending machine

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Weld edge preparation

weld edge hardness is mostly restricted by Engineering

Specs e.g. API 934 to max 225BHN for conventionel

and 235BHN for advanced steel grades;

in some cases to the same level as the base metal .

This can be reached by machining or

oxycutting with subsequent grinding.

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Milling machine for edge preparation

Possibilities: thickness up to 120 mm

length up to 25000 mm

width up to 5000 mm

weight up to 40 t

extremely tight tolerances

shape profiling

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X-edge

J-edge

J-X combined edge

Edge preparation possibilities

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Cold forming

Bend test to check cold forming(cross section 200 x 50 mm) with severedeformation no cracks on the machined sideeven for bending at ambienttemperature

a small crack in the flame cut edgeafter bending at 170C

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Forming

General trend of the influence of cold deformation on mechanical properties

Av(T=const.)

Rp0,2

Rm

Av,

Rm, R

p0,2

cold deformation

Cold Forming:

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Warm and Hot Forming

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500

550

600

650

700

750

800

Rp0

,2re

sp. R

m[M

Pa]

Rp0.2 Rm

200

250

300

350

400

Q 980 C/2h/W+A 730 C/90'/L

Q 950 C/10'/W+A 730 C/90'/L

HG 1100 C/2,5h/L+

Q 950 C/10'/W+A 730 C/90'/L

HG 1140 C/2,5h/L+

Q 950 C/10'/W+A 730 C/90'/L

HG 1170 C/2,5h/L+

Q 950 C/10'/W+A 730 C/90'/L

HG 1100 C/5,0h/L+

Q 950 C/10'/W+A 730 C/90'/L

HG 1140 C/5,0h/L+

Q 950 C/10'/W+A 730 C/90'/L

HG 1170 C/5,0h/L+

Q 950 C/10'/W+A 730 C/90'/L

HG 1100 C/2,5h/L+

Q 980 C/120'/W+

A 730 C/90'/L

HG 1170 C/5,0h/L+

Q 980 C/120'/W+

A 730 C/90'/L

Av

[J],

Cha

rpy-

V-tr

ansv

. Top

Prftemperatur -60 CPrftemperatur -80 CTest Temperature -60CTest Temperature -80C

Mechanical properties of 2.25Cr1MoV-steel in dependence of heat treatments

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Torispherical Heads: ID 3500; smin 180mm, Grade 2.25Cr1Mo (12CrMo9-10)

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Plate for torispherical heads ID 3500; smin 180mm, 12CrMo9-10

heat treatment Q+T+PWHT, initial plate thickness 192mm

Av average without step-coolingAv average after step-cooling

0

50

100

150

200

250

300

350

-100 -80 -60 -40 -20 0 20 40 60 80 100

Test Temperature C]

Av

[J]

After step cooling

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Torispherical Heads ID 3500; smin 180mm, Steel Grade 2.25Cr1Mo (12CrMo9-10)

head hot formed, Q+T + simulated PWHT

0

50

100

150

200

250

300

-100 -80 -60 -40 -20 0 20 40 60 80 100

Test Temperature [ C]

Av

[J]

After step cooling

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Welding - general recommendations

Reactors made out of CrMo(V)-steels are characterized by:

precaution and careful processing required

closer look to:

HAZ hardness Delayed HICC

Toughness in the weld / step cooling

API RP- 934, ASME VIII-2, App. 26

extreme wall thickness strong hardenability severe service conditions

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SA 542 D4a

120mm

Shell inside

Shell outside

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Fabrication aspects to be considered for the use of V modified steels vs. standard 2CrMo steels

Mandatory request for intermediate stress relieving (ISR) application fornozzle welds

Need for a tight control of preheating and interpass temperature application

Tight control of PWHT temperature Careful attention for temporary attachment and/or attachment welds(e.g. insulation supports)

Personnel education.

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Hydrogen induced cold cracking

dry and clean weld bevels select low hydrogen consumables and treat them properly to minimisehydrogen input (rebaking, storage, heated quivers ...)

keep the weld at sufficiently high temperatures until the weld iscompleted (>180C)

lower the concentration of residual hydrogen by heat treatmentimmediately after welding (300-350C)

lower the hardness and cracking susceptibility by PWHT (~700C) orintermediate PWHT (~650-670C)

Weld metal and HAZ in the as welded condition are susceptible to hydrogen induced cold cracking

how to avoid this defect ?:

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Influence of PWHT on thoughness charpy-V -20C for 2.25CrMoV

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Influence of PWHT on toughness; PWHT 710C, 30h for 2.25CrMoV

0

50

100

150

200

250

300

350

400

HAZ t

opHA

Z t/4

HAZ t

/2HA

Z 3/4

HAZ t

opHA

Z t/4

HAZ t

/2HA

Z 3/4

weld

metal

top

weld

metal

t/4

weld

metal

t/2

weld

metal

3/4t

weld

metal

top

weld

metal

t/4

weld

metal

t/2

weld

metal

3/4t

CH

AR

PY-V

(J)

Indiv 1 Indiv 2 Indiv 3 Average

-20C -40C -40C-20C

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0

50

100

150

200

250

300

350

400

0,5 1,5 2,5 3,5 4,5 5,5 6,5 7,5 8,5

Cha

rpy-

V [J

]

weld metal HAZtop t/4 t/2 3/4t top t/4 t/2 3/4t

2CrMoVtest temperature: -20C

PWHT 30hrs @ 710 CPWHT 10hrs @ 680 CPWHT 5hrs @ 680 C

Influence of PWHT on weld metal and HAZ thoughness @ -20C

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Weld metal: Transition curves for different PWHT conditions

Source: Elettrotermochimica S.r.l.

54 J TT 15C2 Cr-1Mo-V

650C 8h

54 J TT 38C2 Cr-1Mo

350C 4h

54 J TT -23C2 Cr-1Mo

620C 4h


350C 4h


620C 4h


650C 4h

54 J TT -4C2 Cr-1Mo-V

680C 4h

2 Cr-1Mo

2 Cr-1Mo-V

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PWHT limits: 680C, 5hours

680C, 10 hours

710C, 30 hours

PWHT-limits to be destinated according to ASME VIII, App. 26

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All Weld Metal Tensile Test

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Impact Test Charpy-V, PWHT 705C, 30hrs

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Influence of step-cooling test, PWHT: 705 C/8 hrs; Location : HAZ center

Order-No 674739Ref.-No 21250Heat-No 55470Material SA 542-D-4aThickness 120 [mm]HP:Weld seam XCurrent ACPosition HAZ center

Faktor: 2,5max. Shift 10 CMin Av 54 JTTr without Step-Cooling: -99,15 CTTrsc with Step-Cooling: -80,40 CDTTr = TTr SC - TTr 18,75 Ctest criteria fullfilled Yes

Test Criteria:TTr + Faktor * TTr max. shift

0

50

100

150

200

250

300

350

400

450

-120 -100 -80 -60 -40 -20 0 20 40 60 80 100

Temperature [ C]

Av [

J]

0 = with Step-Cooling-Test0 = without Step-Cooling Test

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Influence of Step-Cooling, PWHT: 705 C/ 8hrs; Location: Weld metal center

Order-No 674739Ref.-No 21250Heat-No 55470Material SA 542-D-4aThickness 120 [mm]HP:Weld seam XCurrent ACPosition WM center

Faktor: 2,5max. Shift 10 CMin Av 54 JTTr without Step-Cooling: -61,19 CTTrsc with Step-Cooling: -64,84 CDTTr = TTr

SC - TTr -3,65 Ctest criteria fullfilled Yes

Test Criteria:TTr + Faktor * TTr max. shif t

0

50

100

150

200

250

300

350

-120 -100 -80 -60 -40 -20 0 20 40 60 80 100

Temperature [ C]

Av [

J]

0 = with Step-Cooling-Test0 = without Step-Cooling Test

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Influence of Step-cooling on the transition temperature

not fulfilled!

-125

-100

-75

-50

-25

base material 2.25CrMoV

weld metal 2.25CrMoVHAZ 2.25CrMoV

base material 3CrMoVweld metal 3CrMoVHAZ 3CrMoV

0

25

-100 -80 -60 -40 -20 0 20


T T54

Jaf

ter S

tep

Coo

ling

[C

]

x

xxfulfilled

x

x

T

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HAZ hardness comparison of CrMo- and CrMoV-steel

235

400

700C-10h

700C-10h675C-10h

675C-10h

cooling time t8/5

hard

ness

[HV1

0]

250 650C-10h

650C-10h

725C-10h

usual range

2CrMoas welded

2CrMoVas welded

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HAZ hardness vs. cooling time t8/5 and PWHT (bead on plate)

1 10200

250

300

350

400

450

2.25CrMoV as welded 2.25CrMoV 705 C / 10 h 2.25CrMoV 705 C / 30 h 3CrMoV as welded 3CrMoV 705 C / 10 h 3CrMoV 705 C / 30 h 12CrMo9-10 as welded 12CrMo9-10 690 C / 10 h 12CrMo9-10 690 C / 30 h

403020

hard

ness

HV1

0

cooling time t8/5 [s]

TIG ca. 3-5 secGTAW 3-12 secSMAW 5-20 secSAW 10-40 secElectro Slag > 50 sec

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150170190210230250

Base

Meta

lBa

se M

etal

Base

Meta

lHA

ZHA

ZHA

ZWe

ld Me

talWe

ld Me

talWe

ld Me

tal HAZ

HAZ

HAZ

Base

Meta

lBa

se M

etal

Base

Meta

lH

ardn

ess

HV1

0

top 1mm centre bottom 1mm

top 1mm centre bottom 1mm

PWHT 705C, 30hrsPWHT 705C, 8hrs

Influence of PWHT on Vickers-hardness of the welded joint for2.25CrMoV

2CrMoV

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170

180

190

200

210

220

Base

Meta

lBa

se M

etal

Base

Meta

lHA

ZHA

ZHA

ZWe

ld Me

talWe

ld Me

talWe

ld Me

tal HAZ

HAZ

HAZ

Base

Meta

lBa

se M

etal

Base

Meta

l

Brin

ell H

ardn

ess

HB

(1

0mm

Bal

l)

Top Bottom Top Bottom

PWHT 705C, 30hrsPWHT 705C, 8hrs

Influence of PWHT on Brinell-hardness for 2.25CrMoV

PWHT 705C, 30hrs

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Development of carbides during PWHT

730C - 8hM7C3, M23C6,fine V4C3, M2CTEM micrographs on carbon extraction replica 21/4CrMoV

Ref.: Lundin,C.D. and K.K.Khan, WRC Bulletin 409

620C - 15M3C few M23C6

0,5m 0,5m

As weldedno carbides

0,5m

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Disadvantages of Vanadium modified steels

No cost advantage over conventional steel even though lighter vessels. Greater sensitivity to weld cracking during fabrication. ISR mandatory for highly stressed joints e.g. nozzles, bed supports, etc.

Higher PWHT temperature required. Field weld repairs more difficult. Weld materials not readily available (limited suppliers) Low toughness of "as welded" weld deposit prior to PWHT. Higher deposited weld metal hardness Successful fabrication requires experience and tight control of production parameters (narrow production window)

==> E.g. cracking problems from rolling of welded plate have been reported

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Creep properties

German code (AD-Merkblatt) allows an extrapolation of creep results to a factor ofonly 3 necessity to provide the creep resistance for at least 30.000 h if a vessel is

designed for 10 years, even 70.000 h for expected 20 years in service.This criterion will also be used in the future for the European Standard EN 13445 for Unfired Pressure Vessel.

In case of reactor design in creep regime: if creep strength values on welded joints are verified to be within a 20%-scatter band of the base material

welding consumable and base metal from the material manufacturer duly approved by tests within the creep regime can be used for fully stressed weldsusing a joint efficiency factor of 1 instead of 0.8 (design according to GermanAD-Merkblatt, in future also according to EN 13445)

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Heat affected zone hardness

Welds of CrMo(V) reactors steels are always subjected to PWHT

Coarse grained heat affected zone (CG-HAZ) is usually the areaof highest hardness within the HAZ

The main tempering effect is obtained by intensive PWHT

The essential parameter to control HAZ hardness are time and temperature of PWHT

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Benefits of Vanadium addition in regard to creep behaviour

Vanadium carbides provide increased creep rupture life tochrome moly alloys.

Vanadium addition enhances creep rupture life of 2 Cr alloys to a degree greater than that for 3Cr & 5Cr alloys.

Source JSW

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100 1000 10000 10000050

60

70

8090

100

200

300

400 T

ensi

le s

tress

[MPa

]

Time [h]

creep test interrupted12CrMo9-102.25CrMoV3CrMoVVdTV 404/1VdTV 525VdTV 491

Creep test results CrMo(V) steels (base metal) at 500C

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CrMo steels with % V offer improved performance for petrochemical reactorscompared to enhanced 2Cr1Mo steels. Plates are commercially available up toabout 250 mm thickness.

welding needs precautions, in particular: tight control of preheat, interpasstemperature intermediate stress relieving and post weld heating to avoid cold cracking

optimized welding consumables have to be used with respect to low hydrogen inputand very low impurity level to limit in service embrittlement.

screening tests of the weld metal before production starts, e.g. as per API RP 934, are recommended.

the steels tolerate very high temperatures 690 - 710 C for post weld heat treatment, which is beneficial for the toughness of the weld metal.

DH-GTS is a long term supplier with plenty of know how for high sophisticated steels

a wide range of dimensions can be supplied.

more and more vessels will be designed from CrMoV steels to take advantage of improved process possibilities and improved properties.

Conclusion

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Documents

Low alloy CrMo(V) petrochemical reactors · • conventional CrMo steels: ASTM A387 Gr.11 Cl 1 and 2 or Gr. 22 Cl. 2 or ... Low alloy CrMo(V) steel plates for petrochemical reactors