guidelinesforstainlesssteelwelding-13409547269991-phpapp02-120629023108-phpapp02.pptx

8/18/2019 guidelinesforstainlesssteelwelding-13409547269991-phpapp02-120629023108-phpapp02.pptx

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CHALLENGING PROJECTS. IT’S WHAT WE DO.

Guide Lines for (Duplex) Stainless Ste

el Welding

Zhuang Xu

Welding Engieer

McDermott Wuchuan Offshore Engineer Co., Ltd


2/90

Presentation Overview

Duplex Stainless Steel

llo!ing "roperties

"iping Welding

2


3/90

Duplex Stainless Steel

Lean duplex stainless steel

Standard duplex stainless steel

Superduplex stainless steel

#!perduplex stainless steel

3


4/90

Lean duplex stainless steel

Lean duplex such as $%&', (hich contain no deli)erate

Mo addition.

*he lean allo! $%&' (as de+eloped to compete primaril!

(ith the austenitic S %- grade, )ut (ith t(ice the !iel

d strength and significantl! )etter resistance to SCC.

*he (elda)ilit! of $%&' duplex stainless is generall! goo

d (hen using slightl! o+er/allo!ed filler metal.

*he ne(l! de+eloped lean duplex garde LDX$-&- has s

uch impro+ed (elda)ilit! that also autogenous (elding is

possi)le and this material has contri)uted to the )oom in

the lean duplex mar0et.

4


5/90

Standard Duplex Stainless Steel

Standard duplex stainless steel is the dominant commer

cial duplex stainless steel (hich (as de+eloped in the -1

2&s, )ut (as later optimised (ith higher nitrogen le+els f

or impro+ed (elda)ilit!.

*he "3E of $$&4 is a)out %%/%4 resulting in a resistance

to locali5ed corrosion intermediate )et(een the austeniti

c grade S %-2 and the 4/6 Mo super austenitic allo!

s.

*he (elda)ilit! of this grade is good, )ut o+ermatching filler (ith increased nic0el content, e.g. $$&1, is normall! r

e7uired for optimum (eld metal properties.

5


6/90

Superduplex stainless steel

*he superduplex grades (ere de+eloped to (ithstand +er! aggr

essi+e en+ironments to compete (ith super/austenitics and nic0

el )ase allo!s.

$4&2 has, due to high mol!)denum and nitrogen contents, a "

3E of '$/'%, and offers high mechanical strength and corrosionresistance in extremel! aggressi+e en+ironments such as chlori

de/containning acides.

conse7uence of the high allo! content, there is a ris0 of preci

pitation of intermetallic phases, limiting the heat input and interp

ass temperatures (hen multipass (elding. O+ermatching filler (ith increased nic0el content is re7uired, e.

g. $4&1, to compensate element partitioning for optimum corros

ion resistance.

6


7/90

Hyperduplex stainless steel

#!perduplex stainless steel (as de+eloped as a comple

ment to $4&2 (ith increased strength for use in e+en mor

e aggressi+e conditions, such as in hot sea(ater, acidic

chloride solutions and organic acides.

S8$2&2 #D can )e (elded (ith a matching filler (ire of

SO$214L t!pe.

Due to the high allo!ing content, the h!perduplex allo!s

are some(hat more sensiti+e to secondar! phase precipi

tation than the superduplex grades.

7


8/90

Alloying Properties

Elements content of different t!pes of duplex stainless steel

Chromium

9ic0el

Mol!)denum

9itrogen

Manganese

Copper

*ungsten

Car)on Mechancial "roperties

"h!sical "roperties

8


9/90

Duplex Stainless Steel Types

9

Type r !i "o ! P#$

Lean $&/$'6 -/46 &.-/&.%6 &.-/&.$$6 $'/$4

Standard $-/$%6 '.4/6 $.4/%.46 &.-/&.$$6 %%/%4

Superduplex $'/$16 '.4/:6 $.2/'.46 &.-/&.%46 ;'&

#!perduplex $26 .46 46 &.'6 '1


10/90

%ro&iu&

*here is a maximum limit to the chromium content of appro

ximatel! %&6, (here intermetallic phase precipitation can

mar0edl! reduce the ductilit!, toughness and corrosion resi

stance of these allo!s.

Chromium increases the pitting potential, the critical pittingtemperature


11/90

!i'el

9ic0el is a strong austenite sta)li5er and is a principal addi

tion to austenitic stainless steels.

9ic0el allo!ing is generall! detrimental to cre+ice corrosion

resistance in sodium chloride, and )eneficial or (ithout eff

ect in pitting tests. n the duplex stainless steel, ho(e+er, the main role of nic0

el is to maintain the ferrite/austenite )alance, rather than

modif!ing the corrosion resistance.

Lo( nic0el le+els can result in formation of a high proportion of ferrite, there)! lo(ering toughness. Conse7uentl! mos

t consuma)les for (elding duplex stainless steels are o+e

r/allo!ed to contain 2/-&6 of nic0el.

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12/90

"olydenu&

Mol!)denum is a ferrite sta)ili5ing allo!ing element (ith a str

ong )eneficial influence on general and pitting corrosion resi

stance and on the passi+ation properties.

Mol!)denum is fa+oura)le in most en+ironments, )ut in strongl! oxidising en+ironments, such as (arm concentrated nitric

acid, grades containing mol!)denum are less resistant than

stainless steels (ithout mol!)denum.

*he addition of mol!)denum should not exceed approximatel

! '6 since it ma0es the material more suscepti)le to interme

tallic phase precipitation )! (idening the sigma phase field.

12


13/90

!itrogen

9itrogen is an interstitial element that sta)ili5es the austenite

and has strong influence on se+eral properties such as pittin

g corrosion, presence of mol!)denum.

*he duplex grades conse7uentl! contain up to &.'6 nitrogento gi+e impro+ed austenite formation (hen (elding.

9itrogen significantl! increases the strength of the duplex sta

inless steels, )ut also impro+es the ductilit! and toughtness o

f the allo!.

9itrogen dela!s the formation of intermetallic phases in duple

x stainless steels in a similar (a! as in austenitic grades.

13


14/90

"anganese

Manganese sta)ilises austenite and can partl! replace nic0el

.

dditions to stainless steel ha+e )een used to increase the s

olu)ilit! of nitrogen, (hich ha+e a strong )eneficial influenceon the pitting resistance. t has )een reported that manganes

e itself has a negati+e effect on the pitting resistance, )ut co

m)ined additions of nitrogen and mol!)denum o+erride this e

ffect.

3eplacing nic0el (ith manganese and nitrogen ma0es the pri

ce of the material more sta)le since the nic0el price has fluct

uated significantl!.

14


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opper

Copper is added to highl! corrosion resistant austenitics and

duplex grades to further impro+e the corrosion resistance in,

for instance reducing acids such as dilute sulphuric acid.

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Tungsten

*ungsten has )ecome more commonl! used as an allo!ing e

lement in commercial stainless steels (here it is used as a c

ompliment to mol!)denum for impro+ed corrosion resistance.

When used in the "3E expression, the factor for tungsten isapproximatel! half of that for mol!)denum.

*ungsten has, ho(er+er, also )een reported to promote form

ation of intermetallic phases and cause a more rapid em)rittl

ement thatn mol!)denum.

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17/90

aron

n most modern duplex allo!s car)on is limited to le+els of &.

&%(t6 to minimi5e the ris0 of formation of chromium car)ide

s and there)! reduce the suscepti)ilit! of the duplex stainles

s steels to intergranular corrosion.

17


18/90

"e'%ani'al Properties

Type *ield Tensile $long+

S*M 42$.>r.4&

4&0si


19/90

P%ysi's Properties

19

Type Density

,g+'&-.

#esistivity

,/0+'&

"agnetis&Spe'ifi' Heat

apa'ity

, 1 , 2G 2

Averageoeffi'ient of

Linear $xpansion

,34-5

6-3

(4-344)

T%er&alondu'tivity

,W(&2)-3

42$. >r.4& 2.' &.-& ?ES ''2 -$.-


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Pipe Welding

>eneral Welding >uidelines

Welding "rocedure @ualification

Welding Methods

"ost 8a)rication Clean/up

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General Welding Guidelines

Differences Aet(een Duplex and ustenitic Stainless Steels

Selection of Aase Metal

Material 3ecei+ing

#andling B Storage

8acilities

*ools

Clean Auild "hilosoph!

Cutting Duplex Stainless Steel

oint Design

"reheating

#eat nput and nterpass *emperature

"ost(eld #eat *reatment

Desired "hase Aalance

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22/90

Diffen'es 7etween ASS 8 DSS

"ro)lem of SS

#ot crac0ing dusting the composition of the filler metal to pro+ide a significant f

errite content minimi5es these pro)lems, for the more highl! allo!e

d austenitic SS (here the use of a nic0el/)ase filler metal is necessar! and austenitic solidification is una+oida)le.

*he pro)lem is managed )! lo( heat input, often re7uiring man! p

ases to )uild up the (eld.

Methodes to impro+e the hot crac0ing resistance

Limit the content of sulfur, phosphorus and car)on

"roduce duplex microstructure, ferrtie content is % :6

dd proper content of manganese


23/90

Diffen'es 7etween ASS 8 DSS

"ro)lem of DSS

#Z pro)lem DSS ha+e +er! good hot crac0ing resistance due to the high ferrite content.

*he #Z pro)lems are loss of corrosion resistance, toughness, or post/(eld crac0i

ng.

*o a+oid these pro)lems, the (elding procedure should focus on minimi5ing total time at temperature in the red hotF range rather than managing the heat input for a

n! one pass.

d+antage of DSS Summri5ed "roperties

Much higher !ield strength and tensile strength

Stress corrosion crac0ing resistant "ittingGcre+ice corrosion resistant

Erosion resistant

8atigue resistant

Cost effecti+e


24/90

Sele'tion of 7ase "etal

Sufficient 9itrogen

*he important of the )ase metal containing sufficient nitrog

en has )een repeatedl! emphasi5ed.

f the starting material cooled slo(l! through the 2&& to -&

&& deg. 3ange, or if it is allo(ed to air cool into this range f or a minute or so prior to (ater 7uenching then these actio

ns ha+e used up some of the time on the cloc0F

"urchasing >uidelines for Duplex $$6 Cr Stainless Steel "rocess *

u)ing B "iping

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25/90



u)ing B "iping

25

Produ't 9or& Duplex ::; r Stainless SteelPro'ess Tuing

Duplex ::; r Stainless SteelSea&less Pipe

Material "rocess *u)ing Seamless "ipe

Scope *his material technical sheet is intended to supplement existing material standards andspecification rade


26/90



u)ing B "iping

26



#ardness "er S*M standard. f no harness re7uired )! S*M standard, maximum shall )e #3C$:,#A$2-, or #$1&

mpact *esting / Charp! /notch


27/90



u)ing B "iping

27



8errite Content S*M E4$-8errite content shall )e determined oon afull cross section near the OD and Dsurfaces and at mid/(all location-Samples shall )e electrol!ticall! etched ineither 9aO# or O#, and in such a manneras to pro+ide optimum contrast for austeniteand ferrite phase discrimination-"oint cont shall )e conducted at minimumof 4&&X magnification- minimum of %& fields and - points per

field shall )e used-8errite content shall )e )et(een %46/ 446-8errite content of the seam (eld shall )e$46/&6

S*M E4$-8errite content shall )e determined oon afull cross section near the OD and Dsurfaces and at mid/(all location-Samples shall )e electrol!ticall! etched ineither 9aO# or O#, and in such a manneras to pro+ide optimum contrast for austeniteand ferrite phase discrimination-"oint cont shall )e conducted at minimumof 4&&X magnification- minimum of %& fields and - points per

field shall )e used-8errite content shall )e )et(een %46/ 446


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u)ing B "iping

28



MetallographicExamination

-Samples shall )e etched using S*M E'&2 etchant num)er 1:


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u)ing B "iping

29



9on/destructi+e8erriteMeasurement

--&6 of all tu)es shall ha+e ferrite content determined )! fischer ferrite scope-Measurement techni7ue shall )e in accordance (ith compan! appro+ed procedures-8errite content shall )e )et(een %46 / 446

#!drostatic *est -n accordance (ith S*M 2:1G 2:1Mand S*M '4&G '4&M

/ n accordance (ith S*M 21&G21&M

3epair of Defects -Weld repair of defects is not allo(ed

Surface finish -White "ic0led


30/90



u)ing B "iping

30



#andling, Shipment, andStorage

-"roduct shall )e handled, shipped and stored in such a manner as to pre+ent or minimi5e

the possi)ilit! of free iron contamination-"roduct shall not )e handled (ith )are steel hoo0s, chains or lifting for0s (ithout the useof protecti+e insulating material-Onl! stainless steel (ire )rushes, designated for use onl! on stainless steel products, ma!)e used for )rushing and descaling-Suspected free iron contamination, such as e+idenced )! unusual stains or discoloration,shall )e +erified )! ferrox!l testing in accordance (ith the procedure outlined in S*M %:&-8ree iron contaminated areas shall )e cleaned and passi+ated, at the manufacturerNsexpense, using the procedures outlined in S*M %:&

Certification -E9-&$&' %.-A


31/90

"aterial #e'eving

Material certificate re+ie(

"h!sical chec0 including magnetic chec0 or "M as re7ui

red.

pplication of Material *racea)ilit! 9um)er


32/90

Handling 8 Storage

ll pipeGtu)e material (ill )e store in a co+ered (arehous

e

Separate area for storage e7uipped (ith sign )oard

*o use (ood, ru))er +in!l or card)oard for protection fro

m handing de+ices

*o use onl! (e) sling for lifting

"laced upon non/car)on steel surface

"lastic end caps on pipeGtu)e "lastic co+er on pipeGtu)e surfaces.

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33/90

9a'ilities

Clean area (ith metallic iron dust free en+ironment

9on/car)on steel co+ering for all (or0 surfaces

*o put neoprene ru))er co+er on flange end

*o put plastic end cap


34/90

Tools

Stainless steel compati)le files, grinding disc, (ire )rush

es, sa( )lades etc.

Cold cutting B )e+eling machine

34


35/90

lean 7uild P%ilosop%y

"re+ention is the e! 预防是关键

"rofessionalism is the "erception 专业技巧是方法

"roduct @ualit! is the 3esult 产品质量是结果

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36/90


"re/fa)rication Storage 不锈钢管焊接组装前的储存

36

"ol!thene or *arpaulin Sheeting聚!"#$防%&'()

ll "ipesG *u)es to )e 8itted (ith End Caps*+管,-.装+/0的1)

WoodsG 3u))er 3ac0s2质$3456


37/90


fter Cut Aefore Ae+eling789:;?@AB的CD'EF管,GH

"ull *hrough to 3emo+e Dust a+oid contamination

StringI,

cetone

cetone ?@

"ull *hroughF fter Cut and Aefore Ae+eling


38/90


Sponge "lugF nsertion )efore Ae+eling ;


39/90


Clean (ith cetone AE8O3E Ae+eling and "olishing ;?@Et

39

Min $4mm

cetone

Sponge "luge


40/90


Clean (ith cetone 8*E3 Ae+eling ;?@Et

40

Sponge "luge

cetone


41/90


"loshing rs

3emo+e all surface oxide films from )oth internal and exter

nal surfaces to a minimum distance of $4mm using the cor

rect and autori5ed e7uipment >uv的wxy管,Gz{

|}


42/90


8it/Hp 组‹Œfg焊 fter sponge plug remo+al and final clean (ith cetone dampen

ed cloth, commence 8it/Hp and *ac0 in accordance (ith the app

ro+al W"S ‰Ž:EFkUijLMN,:^;‘’“关的焊接w”–—˜组‹

Sponge "lug MHS* )e returned to control point after remo+al fro

m pipe or fitting. 组‹kU9:^LMN,…†opŠg~

E+er! registered Sponge "lugF shall )e accounta)le at the end

of each shift. VX™+\]的LMN,‰šW›œ>前是ž的

42


43/90


"ost Weld Clean 焊:Et Clean Hsing dedicated (ire )rush during and immediatel! after

(elding Ÿ>/0的,‰焊接¡–¢$焊接kU:—˜Et

43


44/90


Clean Hsing cetone Dampened Cloth Ÿ>?@AB的的CD'Et管{GH

44

cetone


45/90


"rotect the (eld B #Z )! (rapping cellophane Ÿ>£¤的¥¦§¨‡©焊接ªq«¬ª

45

Wrapping Cellophane£¤的¥¦§


46/90

utting Duplex Stainless Steel

Mechanical

Sa(ing

Shearing

)rasi+e Wheel Cutting

Water/et Cutting

*hermal

"lasma cutting

Laser cutting

46


47/90

Sawing

Similar (ith austenitic stainless steel

"o(erful machine

"roper )lade alignment

Coarse toothed )lade

Slo( to moderate cutting speed

#ea+! feed

>enerous flo( of coolant

47


48/90

S%earing

More force and hea+ier e7uipment (ill )e re7uired to she

ar stainless steel compared to car)on steel

Car)on steel PF thic0ness shear limit

ustenitic stainless steel QF max thic0ness shear limit

Duplex stainless steel %G-F max.

general clearance guide is to use a clearance of 46 of

the metal thic0ness )et(een shear 0ni+es

*o counter the shearing force re7uired for duplex stainles

s steel, the hold do(n pressure on the clamps ma! ha+e

to )e increased

Alades must )e sharp

48


49/90

Arasive utting

)rasi+e (heels, rotating at high speed can )e used for straight line cutting of sheet and thin gauge plate a

nd for cut/off operations on relati+esmall sections.

*hic0 section cut/off operations areusuall! done (et

Hse uncontaminated +itrified or resin/)onded (heels

Do not induce o+er/heating

49


50/90

Plas&a and Laser

Same e7uipment as for %&'G%-

Optimum parameter +ar! slightl!

*(o t!pes of plasma cutting machine

Mainl! ad+antages of second oneR

*he no55le can )e recessed (ithin a ceramic shield gas, th

ere)! protecting the no55le from dou)le arcing, if no shield

gas (ere present, the ceramic shield gas cup could )e det

eriorated )ecause of the high radiati+e heat produced )! th

e plasma Iet.

t can protect the cutting surface from oxidation caused )!

ox!gen.

50


51/90

Two types of plas&a 'utting

51

a. Dual flo( plasma cutting po(er source ). Dual flo( plasma cutting machine

c. Cutting surface (ithout oxidation d. Cutting gas

d. Secondar! shielding gas e. *he s0eth of dual flo( plasma arc


52/90

1oint Design

52


53/90

Pre%eating

"reheating ma! )e onl! )eneficial (hen used to eliminat

e moisture from the steel as ma! occur in cold am)ient c

onditions or from o+ernight condensation.

When preheating to deal (ith moisture, the steel should

)e heated to a)out -&& deg. Hniforml! and onl! after the(eld preparation has )een cleaned.

53


54/90

H< and


55/90

H< and


56/90

PWHT

"W#* is not need

t is li0el! to )e harmful )ecause heat treatment ma! preci

pitate intermetallic phases or alpha prime em)rittlement ca

suing a loss of toughness and corrosion resistance.

"W#* temperature in excess of %-4 deg can ad+ersel! aff ect the toughness and corrosion resistance of DSS.

9? "W*# should include full solution annealing follo(ed

)! (ater 7uenching.

56

D i d P% 7 l


57/90

Desired P%ase 7alan'e

"hase Aalcance for 8errite and ustenite

t generall! agreed that the characteristic )enefits of DSS

are achie+ed (hen there is at least $46 ferrite (ith the )al

ance austenite.

9ormall! the pahse )alance has )een adIusted to(ard mor e austenite to pro+ide impro+ed tougness, offsetting the los

s of toughness associated (ith ox!gen pic0up from the flux

.

*he phase )alance in the #Z, )eing the original (rought

plate or pipe plus an additional thermal c!cle, is usuall! sli

ghtl! more ferritic than the original material.

57

W ldi P d = lifi ti


58/90

Welding Pro'edure =ualifi'ation

3e7uirement

La) *esting

*ensile

Aend

#ardness

Macro/Sections

Micro/structural Examination

mpact *ests

Corrosion *esting

8errite Content

58

W ldi P d = lifi ti


59/90

Welding Pro'edure =ualifi'ation

3e7uirement

Aecause of the need to limit the total time at temperature f

or the #Z, the properties of duplex grades (ill )e sensiti+

e to section thic0enss and details of actual (elding practic

e. *herefore, 7ualificationF must )e considered in a )roader sense, that is a demonstration that the (elding procedur

e that (ill )e applied during fa)rication (ill not produce an

unaccepta)le loss of engineering properties, especiall! tou

ghness and corrosion resistance.

t (ould )e conser+ati+e to 7ualif! the (elding procedure at e+er! thic0ness and geometr! of (elding )ecause the mi

nor differences in setup ma! )e significant in the results ac

hie+ed in production.

59

L T ti


60/90

La Testing

*ensile

60

L T ti


61/90

La Testing

*ensile

61

L T ti


62/90

La Testing

*ensile

8or pipe ha+ing an outside diameter of %in.


63/90

La Testing

Side Aend

63

La Testing


64/90

La Testing

3oot B 8ace Aend

64

La Testing


65/90

La Testing

>uided/Aend *est "rocedure

65

La Testing


66/90

La Testing

>uided/Aend *est "rocedure

66

La Testing


67/90

La Testing

#ardness


68/90

La Testing

Macro/Examination


69/90

La Testing

Micro/structural Examination cceptance Criteria

*he micro/structure shall )e suita)l! etched and examined at

'&& X magnification and shall ha+e grain )oundar! (ith no c

ontinuous precipitations and the inter/metallic phases, nitrides and car)ides shall not in total exceed &.46

69

La Testing


70/90

La Testing

mpact *est 3e7uirement

mpact testing of (elds shall )e according to follo(ing ta)le, f

ull si5e specimens shall )e applied (here possi)le.

f t(o t!pes of materials are (elded together, each side of the (eld shall )e impact tested and fulfill the re7uirement for th

e actual materal.

*he (eld metal shall fulfil the re7uirement for the least string

ent of the t(o.

70

La Testing


71/90

La Testing

mpact *est

71

La Testing


72/90

La Testing

Corrosion *esting *he test specimen shall ha+e a dimension of full (all thic0

ness )! $4mm along the (eld and 4&mm across the (eld.

*he test shall expose the external and internal surface and

a cross section surface including the (eld 5one in full (all thic0ness. Cut edges shall )e prepared according to S*M

>':. *he specimen shall )e pic0led


73/90

La Testing

8errite Content cceptance Criteria

8or the stainless steel *!pe $$ and $4 Cr duplex the ferrite c

ontent in the (eld metal root and in the last )ead of the (eld

cap shall )e determined in accordance (ith S*M E4$ andshall )e in the range of %&6 to 2&6.

73

ustenite

8errite

Welding "et%ods


74/90

Welding "et%ods

>*W as *ungsten rc Welding=

SMW MW as Metal rc Welding=

8CW


75/90

GTAW (Gas Tungsten Ar' Welding)

E7uipment -. "o(er source. *ransformerG3ectifier


76/90


*orch #ead ssem)l! -. *ungsten electrodes

$. Spare Ceramic Shield

%. >as lens

'. *orch Aod!

4. >as Diffuser

.Split copper collett


77/90


*!pes of rc Start Scratch Start

Easil! cause contamination of the tungsten

#igh 8re7uenc!

Can a+oid the contamination of the tungsten

Cause interference (ith hi/tech electrical e7uipment and compute

r s!stems.

Lift arc

#as )een de+eloped (here the electrode is touched onto the plat

e and is (ithdra(n slightl!.

n arc is produced (ith +er! lo( amperage, (hich is increased to

full amperage as the electrode is extended to the normal arc lengt

h.

77



78/90


Slope in and Slope out During (elding it is used to control the rise and dela! of the cur

rent at the start and end of a (eld as sho(n )elo(

*his is +er! )eneficial in a+oiding crater pipes at the end of (el

d runs.

78



79/90


>as cut off dela! *he gas cut off dela! control dela!s the gas solenoid shut off ti

me at the end of the (eld and is used to gi+e continued shieldi

ng of the solidif!ing and cooling (eld metal at the end of a run.

t is often used (hen (elding materials that oxidise at high tem

peratures such as stainless and titanium allo!s.

79



80/90


Electrode *he most common t!pes of tungsten used are thoriated or ceri

ated for DC and 5ironiated (ith C


81/90


8iller Metal Matching (ith $ '6 more nic0el than in the (rought product.

*he nitrogen content is t!picall! slightl! lo(er in the filler metal

than in the )ase metal.

More highl! allo!ed DSS fillers are suita)le for (elding the lo(

er allo!ed DSS.

81



82/90


>*W as *ungsten rc Welding= Shielding

*he purit! of dr! (elding grade of inert gas, argon, should e7

ual or )etter than 11.146.

>as flo( should )e initiated se+eral seconds ahead of stri0ing the arc, and it should )e maintained for se+eral seconds aft

er the arc is extingushed, ideall! long enough for the (eld an

d #Z to cool )elo( the oxidation range of the SS.

8or electrode co+erage, suggested flo( rates are -$ -: lGm

in


83/90


>*W as *ungsten rc Welding= Shielding

"urging gas, )ecause argon is hea+ier than air, the feed sho

uld )e from the )ottom to the top of the enclosed +olume, (it

h purging )! a minimum of se+en times the +olume.

dditions of up to %6 dr! nitrogen (ill aid in retention of nitro

gen in the (eld metal, particularl! of the more highl! allo!ed

duplex stainelss steel. While the nitrogen adddition has )een

found to increase electrode (ear, the addition of helium parti

all! offsets this effect.

dditions of ox!gen and car)on dioxide to the shielding gas s

hould )e a+oided )ecause the! (ill reduce the corrosion resi

stance of the (eld.

#!drogen should not )e used in the shielding or )ac0ing gas

)ecause of the possi)ilit! of h!drogen em)rittlement .83



84/90


*echni7ue and "arameters n! arc stri0es outside of the (elding 5one (ill creat local

points of autogenous (elding (ith +er! high 7uench rates,

ruslting in locall! high ferrite content and possi)le loss of c

orrosion resistance at those points. *ac0ing (elds should )e made (ith full gas shielding. *her

e should )e no tac0 (eld at the starting point of the root pa

ss.

*he (or0 piece should )e allo(ed to cool )elo( -4& deg f

or standard duplex stainless steels and )elo( -&& deg forsuperduplex stainless steels )et(een (elding passes to pr

o+ide for ade7uate cooling of the #Z in su)se7uent.

84



85/90


*echni7ue and "arameters *he heat input is t!picall! in the range of &.4 $.4 0IGmm

eneral heat input recommendationsR

$$&' or lean duplex &.4 $.& Gmm


86/90


Weld Discoloration Le+els on nside of SS WS D-:.$ -111 >uide to Weld "iscoloration Le+els on n

side of ustenitic Stainless Steel *u)es

9o. -/ -& ppm 9o. $/$4 ppm 9o. %/4& ppm

9o. '/-&& ppm 9o. 4/$&&ppm 9o. / 4&&ppm

9o. 2/ -&&&ppm9o. :/4&&&ppm 9o. 1/-$4&&ppm

9o.-&/$4&&&ppm86

Post 9ari'ation lean-up

http://var/www/apps/conversion/tmp/scratch_7/AWS%20D18.2%20-1999%20Guide%20to%20Weld%20Piscoloration%20Levels%20on%20Inside%20of%20Austenitic%20Stainless%20Steel%20Tubes.pdfhttp://var/www/apps/conversion/tmp/scratch_7/AWS%20D18.2%20-1999%20Guide%20to%20Weld%20Piscoloration%20Levels%20on%20Inside%20of%20Austenitic%20Stainless%20Steel%20Tubes.pdfhttp://var/www/apps/conversion/tmp/scratch_7/AWS%20D18.2%20-1999%20Guide%20to%20Weld%20Piscoloration%20Levels%20on%20Inside%20of%20Austenitic%20Stainless%20Steel%20Tubes.pdfhttp://var/www/apps/conversion/tmp/scratch_7/AWS%20D18.2%20-1999%20Guide%20to%20Weld%20Piscoloration%20Levels%20on%20Inside%20of%20Austenitic%20Stainless%20Steel%20Tubes.pdf


87/90

Post 9ari'ation lean up

Cra!on mar0s, paint, dirt, oil Em)edeed iron paint> dirt> oil


88/90

y > p > >

ll these surface contaminants can act as cre+ices and can )e initiation sites for pitting or cre+ice corrosion of a st

ainless steel.

*hese contamination should )e remo+ed (ith sol+ents.

88

$&edded


89/90

( )

*he iron rusts in a moist or humid en+ironment and can initiate corrosion on the stainless steel surface.

One approach is to a+oid all contact )et(een stainless st

eel and car)on steel. Onl! stainless steel tools, stainless

steel (ire )urshes, stainless steel clamps, and ne(, uncontaminated grinding (heels should )e used on stainles

s.

Often the tools are color coded in the shop.

89

Weld Spatter> weld dis'oloration> flul t i


90/90

x> slag> ar' stries

ll these defects ma! occur during (elding. *he! can act

as cre+ices and initiate cre+ice corrosion in chloride/containing en+ironments.

Welding spatter

Weld spatter can )e a+oided during fa)rication )! using an

anti/spatter compound Weld discoloration

Weld discoloration causes a loss of corrosion resistance d

ue to the destruction of the passi+e la!er.

#ea+! (eld discoloration or heat tint should )e a+oided )!inert gas shielding and )! pruging the )ac0 side of (elds (

ith an inert gas.

#eat tint cannot )e totall! a+oided and must )e remo+ed d

Documents

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