The new generation of CrMo(V) steel plates base …. Detemple and F. Hanus, Dillinger Pressure...

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1The new generation of CrMoV-steel plates - base material, welding

The new generation of CrMo(V) steel plates

base material - welding

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1. Introduction

2. Application trends and resulting requirements for CrMo(V) steels

3. Metallurgical limits for PWHT- conditions

4. Processing

5. Summary

Content

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1. Introduction

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

2¼Cr1Mo¼V ASTM/ASME A/SA832-22VA/SA 542-D-4/4a

EN 10028-2: 2003 13CrMoV9-10

3Cr1Mo¼V ASTM/ASME A/SA832-23VA/SA 542-E-4/4a

EN 10028-2: 2003 12CrMoV12-10

„conventional“

1¼Cr½Mo ASTM/ASME A/SA 387-11-1/2EN 10028-2: 1992, 2003 13CrMoSi5-5

1Cr½Mo ASTM/ASME A/SA 387-12-1/2EN 10028-2: 1992, 2003 13CrMo4-5

2¼Cr1Mo 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

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


EN 10028-2: 2003 13CrMoV9-10


EN 10028-2: 2003 12CrMoV12-10

„enhanced“


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

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

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

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




EN 10028-2: 2003 12CrMoV12-10

A broad variety of CrMo(V) steels is commercially available„new generation“


EN 10028-2: 2003 13CrMoV9-10

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2. Application trends and resultingrequirements for CrMo(V) steels

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

Application:

• typical applications are hydrotreating reactors

• operating temperatures up to 480 °C

• hydrogen partial pressures up to 180 bar or even higher

Trends:

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

• higher operating temperatures and pressures resulting in higher wall thicknesses

• increasing demand due to expansion or new construction of plants

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● 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● Improved resistance against hydrogen● 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 and microstructure● Hardness restrictions● Specifying step cooling test● Additional tensile test at elevated temperatures● ...

Special requirements for more sophisticated steels

Many additional requirements; often in combination

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3. Metallurgical limits for PWHT conditions

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General influence of a PWHT on the mechanical propertiesof CrMo-steels

BeforePWHT

AfterPWHT

Av,

Rm

, Rp0

,2

HP-Factor

mR after

Rm before

Rp0.2 before

Rp0.2 after

Av after

Av before

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Tensile- and yield strength of enhanced 2¼CrMo 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

,2 re

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 2¼CrMo (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

,2 re

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

,2 re

sp. R

m [N

/mm

2 ]

Thickness > 200 mm

Rm “V-modified“

Rp0.2 “enhanced“

Rp0.2“V-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

,2 re

sp. R

m [N

/mm

2 ]

Thickness > 200 mm

Rm “V-modified“

Rp0.2“V-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 ofenhanced 2¼CrMo(V) steels (N+AC+T)

0

50

100

150

200

250

300

350

19,8 20,0 20,2 20,4 20,6 20,8 21,0 21,2

Impa

ct T

ough

ness

[J]

2¼2¼CrMoCrMo

0

50

100

150

200

250

300

350

19,8 20,0 20,2 20,4 20,6 20,8 21,0 21,2

Impa

ct T

ough

ness

[J]

HP-Factor

2¼2¼CrMoVCrMoV

Thickness Thickness > 200 mm> 200 mm

HP-Factor

Thickness Thickness > 200 mm> 200 mm

+20 °C

+20 °C

0 °C 0 °C

-20 °C

-20 °C

-40 °C

-40 °C

-60 °C

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19,0

19,2

19,4

19,6

19,8

20,0

20,2

20,4

20,6

20,8

21,0

21,2

0 20 40 60 80 100 120 140 160 180 20019,0

19,2

19,4

19,6

19,8

20,0

20,2

20,4

20,6

20,8

21,0

21,2

0 20 40 60 80 100 120 140 160 180 200

-18 °C u. -29 °C

N+AC+T

SA 387-22-2: Feasibility in dependence of HP, Rm, Re, Ch-V, hardness and plate thickness of 2¼CrMo steel

Plate thickness [mm] Plate thickness [mm]

Hol

lom

on p

aram

eter

Hol

lom

on p

aram

eter

Average ≥ 31 J

-40 °C

-10 °C

N+T

-18 °C-29 °C

195 HBN+AC+T

200 HB

205 HB

210 HB

215 HB

190 HB

N+T

200 HB 195 HB

205 HB

210 HB

215 HB

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0

25

50

75

100

125

150

175

200

225

250

1,50 1,75 2,00 2,25 2,50 2,75 3,00 3,25 3,50 3,75 4,00 4,25 4,50 4,75 5,00 5,25

Width [mm]

Thic

knes

s [m

m]

As rolled(plates for

hot-forming)

up to 37 t

2¼ CrMo(V), Q + T, plate delivery dimensions of Dillinger Hütte GTS

Maximum thickness is often limited by requirements from specifications

upon agreement up to 42 tN + AC + T

(Q + T)up to 37 t

up to 28 t

Depending on grade & thickness up to 37 t

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• CrMo steels with ¼V offer improved performance for petro-chemical reactors compared to enhanced 2¼Cr1Mo steels.

• Plates are commercially available up to about 250 mm thickness.

• The steels tolerate very high temperatures 690 - 710 °C for postweld heat treatment.

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

• A wide range of dimensions can be supplied.

Conclusion 1

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4. Processing

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4. Processing - Index

4.1 Reference to API 934 - Recommended Practice4.2 Impact toughness requirements test conditions4.3 Step cooling4.4 Flame cutting4.5 Forming and subsequent thermal treatment4.6 Welding

– Weld design– Welding procedure qualification– Production testing– Preheat and minimum interpass temperature– HAZ-hardness– Welding consumables– Production tests

4.7 Post weld heat treatments– Intermediate post weld heat treatments– PWHT - „final PWHT”

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Title and introduction of API 934

API recommended practice 934 : 2000Materials and Fabrication Requirements for 2¼ Cr-1Mo & 3Cr-1MoSteel Heavy Wall Pressure Vessels for High Temperature, HighPressure Hydrogen Service *

“....IntroductionThis recommended practice applies to new heavy wall pressure vessels inpetroleum refining, petrochemical and chemical facilities in which hydrogenor hydrogen-containing fluids are processed at elevated temperature andpressure.Materials covered by this recommended practice are conventional steelsincluding standard 2-¼Cr-1Mo and standard 3Cr-1Mo steels, and advancedsteels including enhanced 2-¼Cr-1‘Mo, 2-¼Cr-1Mo-¼V, 3Cr-1Mo-¼V-Ti-B,and 3Cr-1Mo-¼V-Cb-Ca steels. The interior surfaces of these heavy wallpressure vessels may have an austenitic stainless steel weld overlay toprovide additional corrosion resistance. ...”

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Impact test - step cooling

on the base material (each heat)•on welding consumables (each batch)•on HAZ

for the qualification of welding proceduresand the verification on production welds

What is step cooling and why is it applied ?

Additional to the PWHT condition impact tests arerequired after “step cooling”:

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impact transition curve

after high temperature service

test temperature

impact energy before service

∆∆TT54J

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Service embrittlement - step cooling

trace elements are responsible

Parent materialJ = (Si + Mn) x (P + Sn) x 1000

Weld metalX = (10P + 5Sb + 4Sn + As) / 100 API 934 X < 15

harmful elements must be restricted to provide goodtoughness properties through the life time.

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Step cooling - heat treatment

1 6 °C/h2 6 °C/h3 6 °C/h4 3 °C/h5 28 °C/h

316°C

Heating rate56°/h

6h

100h60h24h15h1h

6h

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Step cooling- impact transition curve

after service

test temperature

impact energy initial after

stepcooling

∆∆TTSCSC ∆∆TTtottot54J

∆∆TTtottot = 2.5 x ∆∆TTSCSC

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4.6 Welding

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HAZ hardness comparison of CrMo- and CrMoV-steel

2¼CrMo¼V as welded

2¼CrMoas welded

cooling time t8/5

HV10

250

usual range

400

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Coarse grained HAZ microstructure

as welded coarse grained HAZt8/5 22s - essentially Martensite

For the usual weldingconditions we obtain

Martensite in thecoarsed grained HAZ

andhigh as welded

hardness~400 HB

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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 side even forbending at ambient temperatur• a small crack in the flame cut edge afterbending at 170°C

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Hydrogen induced cold cracking

• dry and clean weld bevels• select low hydrogen consumables and treat them properly

to minimise hydrogen input (rebaking, storage, heatedquivers ...)

• keep the weld at sufficiently high temperatures until theweld is completed (>180°C)

• lower the concentration of residual hydrogen by heattreatment immediately after welding (300-350°C)

• lower the hardness and cracking susceptibility by PWHT(~700°C) or „intermediate PWHT“ (~650-670°C)

Weld metal and HAZ in the as welded condition aresusceptible to hydrogen induced cold crackinghow to avoid this defect ?

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HAZ hardness comparison of CrMo- and CrMoV-steel

2¼CrMo¼V as welded

235

400

700°C-10h

700°C-10h

2¼CrMoas welded

675°C-10h

675°C-10h

cooling time t8/5

HV10

250 650°C-10h

650°C-10h

725°C-10h

usual range

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Development of carbides during PWHT

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

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

620°C - 15’M3C few M23C6

0,5µm 0,5µm

As weldedno carbides

0,5µm

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5. Summary

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Summary

• Parent metal toughness: sufficient safety margin against the requirementsat -29°C and taking into account the step cooling. Limited step coolingembrittlement is achieved by extremely low level of trace elements.

• HAZ toughness: after PWHT impact at -29°C and “after lifetime” at +10°Csatisfactory thanks to ultra low trace elements.

• HAZ hardness 248HV10 (235 HB) is achieved by proper PWHT at 705°C• 235HV10 is difficult to achieve• weld metal toughness: Very few potential suppliers. Rather important

scatter of impact results at -29°C, and at +10°C after “lifetime” more difficultthan for CrMo-Steel. (with regard to the lowest anticipated servicetemperature some relaxation should be possible). Development is ongoing.

• hydrogen induced cracking can safely be prevented -> needs goodworkmanship, careful personal and well controlled processing conditions

• PWHT for 8-10 hours 705°C - 710°C is experienced to be the bestcompromise for the properties in the welded construction. In case ofrepeated PWHT the sum of holding times shall not exceed 24 h.

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Thank you for your attention

and welcome to our workshops

Date post:	17-Apr-2018
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The new generation of CrMo(V) steel plates base …. Detemple and F. Hanus, Dillinger Pressure...

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