Application Technology, Volker Gross Böhler Schweisstechnik

Deutschland Hamm, Germany

Application Technology, Volker Gross Böhler Schweisstechnik Deutschland

Hamm, Germany5.2012, SBW

Challenges in 21/4Cr1Mo(V)welding fabrication

� Agenda

� basics of CrMo and CrMoV

� strength/ toughness features

� development of suitable filler metals

� essential issues

� strong recommendations

Reactors in refinery applications

C-Mn

1200t

21/4Cr1Mo

800t

C-Mn/ inconel duplex

1500t

21/4Cr1MoV

930t

4

effect of stable carbides

•less risk of CH4-formation > petrochemical (hydrotreating) reactors, 11/22/22V

•Application in the creep range > power plant equipment

Why CrMos are suitable

Tendency to carbide formation

Behaviour of C in ferritic micro structure

- thermal expan.

- thermal conductiv.

- diffusion coeff. C

- solubility for C

- carbide formation

Propeties: ferrite vs. austenite

ferriteaustenite

Str

engt

h at

hig

h te

mp.

production of base materials, plates

low N, H, O

6

Base metal

-Structure defined by rolling/ forming processes, heat treatments

-Lowest contents in S, N, H, O byvacuum metallurgy

but: (slow solidifcation)

Normalizing/ solution annealing required

Weld metal

-Structure: as casted

.Welding under normal atmosphere

slag = pick up of N,H,O

but fortunately : fast solidifcationleading to regular distribution of elements,therefore in general no solution annealing to be applied

General difference between base metal and weld meta l

weld YS (MPa) TS (MPa) Elong. (%) CVN (J)

22 800 950 19 50

11 700 850 20 70

CrMo(V) heat treatment essentials

General features of bainitic/ martensitic structure :

heat treatments required

�DHT: dehydrogenation treatment (350°C/ min 4hrs )

removes Hydrogen! A MUST

H-sources: atmosphere/ coating/ flux)

�ISR: intermediate stress relieving (620-680°C/ 6hrs)

for highly stressed joints (nozzles, build up rings , etc)

�SR: stress relieving <min pwht> (660-705°C/8hrs min)

desired structure achieved (min reactor condition)

Influence on strength & toughness

�Step Cooling / max pwht

Simulation of fabrication & refinery conditions

C Si Mn P / S Cr Mo Nix-factor [ppm]

0,05 0,2 0,7 < ,01 2,4 1,1 0 05 7

0,06 0,2 0,7 < ,01 2,4 1,1 0,05 6

ranges-chemistries (wt-%) of CrMo-filler metals

SAW, process, flux, polarity C Si Mn P / S Cr Mo x-factor [ppm]

0,07 0,2 0,7 < ,01 2,4 1 5

0,08 0,2 0,8 < ,01 2,4 1 7

0,1 0,2 0,8 < ,01 2,4 1 4

0,1 0,2 0,8 < ,01 2,4 1 7

0,1 0,2 0,8 < ,01 2,4 1 5

0,11 0,2 0,8 < ,01 2,4 1 7

DC+, single wireUV 420 TTR

AC,single wireUV 420 TTR-W

Tandem, DC+/ACUV 420 TTR-W

SMAW, DC+

Metallurgical review ofsolidification conditions

Typical impact strength for B3 GTA / SM-SA weld me tals before / after step cooling

Impact - temperature - curve

0-10-20-30-40-50-60-70-80

Test temperature [°C]

0

50

100

150

200

250

300

Kv

[J]

before scafter scbefore scafter sc

54 J

~50ppm O, GTAW (~base metal)

~400ppm O, SAW / SMAWdifference in oxygen

Main metallurgical difference betweenwelding processes= OXYGEN

formation of oxides, consequences

Al 2O3

SiO2

MnOCr2O3

Fe2O3

Oxygen in weld metal=

composed of different oxides

oxides formed during solidification

=nuclids

the higher the formation temp. =

early formation of nuclids

More nuclids =

-faster solidification

-finer grains

-less seggregation

-less precipitations

SMAW : Phoenix SH Chromo 2 KS, ø: 4,0 mm

-50 -40 -29 20 30

Test temperature [°C]

0

50

100

150

200

250

CV

N [

J]

690°C/30 h (current) 690°C/30 h (previous)

690°C/30 h + sc (current) 690°C/30 h + sc (previous)

≈

54 J

SMAW : Phoenix SH Chromo 2 KS, ø: 4,0 mm

-50 -40 -29 20 30

Test temperature [°C]

0

50

100

150

200

250

CV

N [

J]

690°C/10 h (current) 690°C/10 h (previous)

690°C/10 h + sc (current) 690°C/10 h + sc (previous)

≈

54 J

SMAW : Phoenix SH Chromo 2 KS, ø: 4,0 mm

-50 -40 -29 20 30

Test temperature [°C]

0

50

100

150

200

250

CV

N [

J]

690°C/30 h (current) 690°C/30 h (previous)690°C/30 h + sc (current) 690°C/30 h + sc (previous)

≈

54 J

SMAW : Phoenix SH Chromo 2 KS, ø: 4,0 mm

-50 -40 -29 20 30

Test temperature [°C]

0

50

100

150

200

250

CV

N [

J]

690°C/10 h (current) 690°C/10 h (previous)

690°C/10 h + sc (current) 690°C/10 h + sc (previous)

≈

54 J

Improvement in toughness in SMA welds; pos. 3 G up,

conv. CrMos, 21/4Cr1Mo,Properties after SR and step cooling

Toughness properties of SAW single wire, AC

Impact - temperature - curve

-90 -80 -70 -60 -50 -40 -30 -20

Test temperature [°C]

0

50

100

150

200

250

KV

[J]

690°C/8 h (current)

690°C/8 h (previous)

690°C/8 h + step cooling (current)

690°C/8 h + step cooling (previous)

54 J

current previous

05.052006 Autorized inspection representative

Enclosure to Inspection certificate no. 130012.1

Phoenix SH Chromo 2 KS, Ø 5,0 mm, heat-no. 1114566

0 10 20 30 40 50-10-20-30-40-50-60-70-80

Temperature [°C]

0

50

100

150

200

250

300

CV

N [

J]

691°C / 5hrs 691°C / 5hrs + sc 54 J

-54,

8

-68,

0 (vTr54 + 2,5 x (∆vTr54sc)) = - 35,0°C

±14°C ±14°C

05.052006 Autorized inspection representative

Enclosure to Inspection certificate no. 130014.1

Union S 1 CrMo 2, Ø 4,0 mm, heat-no. 328556 / UV 4 20 TTR-W, heat-no. 1401278

0 10 20 30 40 50-10-20-30-40-50-60-70-80

Temperature [°C]

0

50

100

150

200

250

300

CV

N [

J]

691°C / 5hrs 691°C / 5hrs + sc 54 J

-54,

5

-52,

9

±14°C ±14°C

(vTr54 + 3,0 x (∆vTr54sc)) = - 57,7°C

05.05.2006 Autorized inspection representative

Enclosure to Inspection certificate no. 130015.1

Union I CrMo 910 Spezial, 2,4 mm, heat-no. 293156

0 10 20 30 40 50-10-20-30-40-50-60-70-80-90-100

Temperature [°C]

0

50

100

150

200

250

300

CV

N [

J]

691°C / 5hrs 691°C / 5hrs + sc 54 J

-88,

6

-92,

8

±14°C ±14°C

(vTr54 + 2,5 x (∆vTr54sc)) = - 82,3°C

„Old“ materials (grade 11/22) with limited strength

CrMo- grades

Type C Cr Mo V NbPWHT

[°C]YS

[MPa]TS

[MPa]AWS filler

metal

11 0,15 1,3 0,5 660 275 485 - 660 B2

22 0,12 2,3 1 690 310 515 - 690 B3

22 V 0,10 2,30 1 0,3 0,05 705 415 585 - 760B3 mod.

Code Case 2098

Service conditions and demand for bigger reactors increased

Consequence of increased service conditions :

• increase in wall thickness

increase in weight of the equipment

(limitations in transport to be considered)

ATB

358mm F22

PC:

454 °C

215 bar

Benefit of CrMo(V) materials for hydroprocessing re actors

• high (creep) strength conditions due to stable carb ides

• higher resistance against hydrogen, disbonding

• high toughness level

CrMo- grades

Type C Cr Mo V Nb PWHT [°C]

YS[MPa]

TS[MPa]

AWS filler metal

11 0,15 1,3 0,5 660 275 485 - 660 B2

22 0,12 2,3 1 690 310 515 - 690 B3

22 V 0,10 2,30 1 0,3 0,05 705 415 585 - 760 B3 mod.

service conditions :

454°C, 215 bar

Courtesy of ATB

267mm2007

317mm358mm2006

F22VF22ASME VIIIEd.

ALLOWABLE STRESS

100

125

150

175

200

225

250

350 378 406 434 462 490

temperature °C

allo

wab

le s

tres

s M

Pa

Conventional 2¼Cr1Mo -ASME 2006 Conventional 2¼Cr1Mo -ASME 2007

2¼Cr1Mo V modified -ASME 2006 2¼Cr1Mo V modified -ASME 2007

ATB

economical advantages:

save in thicknesssave in weight

BUT:

21/4Cr1MoV has to be welded

weld YS (MPa) TS (MPa) Elong. (%) CVN (J)

22V 880 1070 19 20

22 800 950 19 50

11 700 850 20 70

Key property of CrMoV welds

Increased strength in the as welded condition to be considered

Tests on tandem DC/AC all weld metal,2x4mm

550/550 A, 29/ 32 V, 80 cm/min

Preheat.: 180 °C, interpass: max 230 °C

Strength,rt ISR As welded 620°C/ 4h 650°C/ 4h 680°C/ 4h 710°C/ 4h

Rp0.2, MPa 880 859 778 650 591

Rm, MPa 1070 956 858 735 682

A5, % 18,9 16,2 15,7 19,2 19,4

Z, % 51,2 60,4 62,9 69,9 70

CVN (J) at RT 17 19 20 8 14 11 17 26 40 127 123 132 152 153 156

Hardness HV10 345 333 295 252 232

ISR of restrained joints, CrMoV SA welds

Secondary hardening

Advantage of high toughness

SAW Union S 1 CrMo 2 V/ UV 430TTR-W

actual joint metal toughness

C Si Mn P S Cr Mo Ni V Al Cu Nb Xf Kf

,09 ,11 1,19 ,005 ,004 2,45 1,03 ,03 ,25 <,01 ,03 ,013 6 0,7

tandem weld, 300mm wt1/2t

min pwht 705-710°C/8hrs

PWHT°C/hrs

T°C

Rpo.2MPa

RmMPa

A5%

Requ. >585

705/ 10 rt 569 667 23

705/ 8 rt 563 662 23

705/ 32 rt 491 610 26

strength properties of CrMoV-welds

all weld metal, SAW, single wire, AC

Comment :

no comfortable safety margin for tensile strength.

Same properties in stick electrode welds

main issues in CrMoV-welding

Which properties are affected?

2 type of defects mainly, consequences are time and money consuming due to repair, delay in deliveries

• cracks

� Hydrogen attack under control by rebaking, DHT

� Reheat cracking under control by Kf

• more frequent: toughness vs requirements

- SRC does occur on equipment only due to restrainedcondition, not on qualification/pt coupons of same thi ckness

- SRC to be detected by high density UT only

- does not occur after DHT, but after ISR/pwht

- even after optimized ISR

Facts on SRC

location of cracks (boat sample)

•Cracks occur in not refined areas in multi layer SA welds

•Arrested at the fine grain area

•No specific precipitations, seggregations, micro s tructure compared to sound welds

Reheat cracking issue

New Composition Factor toControl reheat cracking

Proposed criterion in the Gleeble Test: (RoA>23%)K factor = Pb + Bi + 0.03Sb < 1.5ppm

Presented by Industeel, API 934 meeting Denver 20090

5

10

15

20

25

30

35

40

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

K factor = Pb+Bi+0,03Sb

RoA

% a

t 650

°C

]

Bohler approach to resolve reheat cracking

low K-factor + fine grainbecause cracks are arrested at fine grain area

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11 12K factor = Pb+Bi+0,03Sb

RoA

% a

t 650

°C

applicable for all joints

„Bohler“ data

applied for circseams

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11 12K factor = Pb+Bi+0,03Sb

RoA

% a

t 650

°C

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11 12K factor = Pb+Bi+0,03Sb (ppm)

RoA

% a

t 650

°C

Competitor values

GDMS-method only

Kind attention to the rebaking of SAW flux

HYDROGEN issue

~60°C

~300°C

300°C

����

large volumen

heating sticks on bottom only

Flux to be dryed on plates, 5cm height max !

Colds Cracks in build up welds (support rings) caus ed by Hydrogen

failed

-min pwht

-min pwht+sc

Not acceptable,why?

Observations in 22V SA welds

Main reasons for toughness (step cooling) issues

• high X-bar >15ppm;

-not available with actual suppliers (<12ppm)

-not allowed by specifications

• trace elements influencing nucleation (under contro l)

• welding and all temperature parameters

•Why the weld failed in the step cooling test then?? ?

Not an issue for reactor welds (except nozzle welds ) due to massive qty., but to maintain preheating temp. becomes essential !

• Reason for overheating: – Interpass temp. (recom. max 230°C) was measured on top side.– loss in temp. from actual weld location to top side not considered

actual

~400°C

measured 230°C

Temp. gradient!

„small“ sized coupon for PQ

730

735

740

745

750

755

760

765

770

14,0 14,2 14,4 14,6 14,8 15,0 15,2 15,4 15,6 15,8 16,0

Zeit in Stunden

Tem

pera

tur

in °C

Kanal 1

Kanal 2

Kanal 3

Kanal 4

Kanal 5

Kanal 6

Kanal 7

Kanal 8

Kanal 9

Kanal 10

Kanal 11

Kanal 12

Kanal 13

Kanal 14

Kanal 15

Kanal 16

Kanal 17

Kanal 18

Kanal 19

Kanal 20

Kanal 21

Kanal 22

Kanal 23

Kanal 24

Kanal 25

Kanal 27

Temp. range of pwht equipment

•record by thermocouple in the furnace: 705°C•actual : 740 -760°C

!!!! thermocouple to be attached to the coupon !!!!

-low cost for equipment

-far cheaper than repeat test

-online control on PC possible

LESS RISKS

Temp. range of pwht equipment

•record by thermocouple in the furnace: 705°C•actual : 740 -760°C

21-30J 160-200J

brittle fracture along grain bounderies ductile fracture

fracture surface of impact specimens (-30°C/ 705°C/ 8hrs)

from same lots, but different „temperature conditio ns“

toughness issue in 22V SA welds

structure of 22V SAW impact specimen at -30°C/ 705 °C/ 8hrs

200µm 50µm

observations

200µm

•large grains

•carbide precipitations on grain boundery

50µm

21-30J

160-200J

21-30J

160-200J •smaller grains

•less carbide precipita-tions on grain boundery

excessive interpasstemp.

21J 190J

-brittle fracture-Crack along grain boundery,-precipitations !

-ductile surface

cross section of impact specimen

21-30J 160-200J

cross section of SAW impact specimen

325 mm

Narrow gap 22V SA welds

flat thin beads mandatory (~max 3.5 mm)

sufficient refinement by subsequent beads !!!!

flat thin beads achieved by

by suitable joint opening + suitable parameters

sketch for same weld metal volume but different joint opening

16mm 22mm

AC, 500 A, 30 V; 45 cm/min

Phoenix Chromo 2 V, Ø 4,0 mm, 3G up

thick beads thin, weaved beads

ATTENTION: Conventional equation to calculate heat input not applicable. Weaving width to be included.

toughnesshighlow

-sufficient refinement-less precipitations-smaller grains

Different bead formation in SMA welds

Typical preheating arrangements for circumferrentia l seams

fine grain to be maintained by

� flat beads (see API 934B too), controlled bead heig ht

�weaved beads for SMAW, bead height: max 2,5mm

�SAW: bead height: max 3,5mm

�controlled temperatures

preheating, interpass temp., DHT, ISR, PWHT

� welding-parameters to be controlled

� Quality of the equipment to be controlled

� Welders to be trained!!!!!!!!!!!!!!!!!!

consequence: strict limitations in welding

recommendations for smooth CrMoV welds

• Material has been underestimated

• 21/4Cr1MoV asks for specific considerations including costs in

terms of:

– in welding, equipment, handling

– evaluations of acceptance criteria

- to rely on experiences in the conventional CrMo on ly is not sufficient at all.

• So far ~10 fabricators know about safe fabrication since introduction

in ~1995!!!

– WHY only ~10 major fabricators worldwide????

– Above mentioned items were simply not considered by other fabricators

Why do (did) these problems occur(ed) ?

Beginning of journey

Project No.

Customer Shell Thickness

No of Circ.

Seams

Year of Mfg.

45030 67 12 2000

45345 138 9 2007

45353 168 5 2008

45376 161 7 2008

45377 161 7 2008

45379 161 9 2008

45380 161 9 2008

Typical development of experience in fabrication of Cr-Mo-V Reactors

Running Cr-Mo-V Reactors

Project No.

No. of Projects

CustomerShell

ThicknessNo of Circ.

Seams

Expected Year of

Dispatch

45514/ 45522

8 290 64

2010 -2011

45515/ 45523

8 287 72

45516/ 45524

4 229 8

45517 1 303 9

45518 1 299.5 11

Typical development of experience in fabrication of Cr-Mo-V Reactors

Running Cr-Mo-V Reactors

Project No.

No. of Projects

CustomerShell

Thickness

No of Circ. Seams

Expected Year of

Dispatch

45526 1 136 14

201045527 1 168 10

45528 1 165 9

45536/1-4

4 153 8

2010-2011

45537/1-4

4 149 9

45538 2 123 5

Typical development of experience in fabrication of Cr-Mo-V Reactors

Running Cr-Mo-V Reactors

Project No.

No. of Projects

CustomerShell

ThicknessNo of Circ.

Seams

Expected Year of

Dispatch

45546 1 101 92011

45547 1 96 9

45548 1 101 92011

45549 1 96 9

45551 1 96 11

2010-201145556 1 91 15

45557 1 91 15

Typical development of experience in fabrication of Cr-Mo-V Reactors

Weight: 930 MT, Process: Axens; Material: 2.25Cr-1M o-0.25V + SS347 O/LDimension: Ø 6.4 m x 31.1 m L x 138 mm Thk

20072007

Largest Dia. Cr-Mo-V DHDS Reactor

DHDS Reactor – Essar Refinery, India

Weight: 870 MT; Process: UOP; Material : 2.25Cr-1Mo- 0.25V + SS347 O/LDimension: Ø 5 m x 26.1 m L x 297 mm Thk,

20092009

Hydrocracking Reactor- I – Helpe, Greece

20092009

Hydrocracking Reactor- II – Helpe, Greece

Weight: 970 MT; Process: UOP; Material : 2.25Cr-1Mo- 0.25V+ SS347 O/LDimension: Ø 5 m x 29.5 m L x 292 mm Thk,

HDT Reactors – IOCL, Panipat INDIA

Weight: 487 MT, Process: Axens; Material: 2.25Cr-1M 0-0.25V + SS347 O/LDim.: Ø 4.2 m X 19 m L X 161 mm Thk

20082008

DHDT Reactors – BRPL, INDIA

20082008

Weight: 397 MT, Process: Axens; Material: 2.25Cr-1M o-0.25V + SS347 O/LDimension: Ø 3.3 m X 22.9 m L X 146 mm Thk

THE petrochemical success story worldwide

• a Middle East Refinery• 22 heavy walled reactors in grade „22V“ by L&T, HZW

Nos WT (mm) Weight (mt)

4 229 255

8 287 975

8 290 750

1 299 1240

1 303 1046

Process filler metals Boehler Qty.

SAW wire: Union S 1 CrMo 2 VFlux: UV 430 TTR-W

800 mt

SMAW Phoenix Chromo 2 V 100 mt