Challenges in 21/4Cr1Mo(V) welding fabrication...ISR: intermediate stress relieving (620-680°C/...
Transcript of Challenges in 21/4Cr1Mo(V) welding fabrication...ISR: intermediate stress relieving (620-680°C/...
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