1-Weld Process Crack Mechanisms. Rev 1

8/19/2019 1-Weld Process Crack Mechanisms. Rev 1

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Copyright © 2006, TWI LtdWorld Centre for Materials Joining Technology

CSWIP 3.1 WELDING INSPECTION CSWIP 3.1 WELDING INSPECTION

TWI Training & ExaminationTWI Training & ExaminationServicesServices

Weldability of SteelsWeldability of Steels

Course Reference WIS 5

Course notes section reference 22


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Weldability of SteelsWeldability of Steels

The "el#ability of steel is mainly #e$en#ant on carbon & otherThe "el#ability of steel is mainly #e$en#ant on carbon & otheralloying elements content'alloying elements content'

If a material has limite# "el#ability% "e nee# to ta/e s$ecial measuresIf a material has limite# "el#ability% "e nee# to ta/e s$ecial measuresto ensure the maintenance of the $ro$erties re-uire#to ensure the maintenance of the $ro$erties re-uire#

,oor "el#ability normally results in the occurrence of crac/ing,oor "el#ability normally results in the occurrence of crac/ing

. steel is consi#ere# to have $oor "el#ability "hen). steel is consi#ere# to have $oor "el#ability "hen)

• an acce$table oint can only be ma#e by using very narro"an acce$table oint can only be ma#e by using very narro"range of "el#ing con#itionsrange of "el#ing con#itions

• great $recautions to avoi# crac/ing are essentialgreat $recautions to avoi# crac/ing are essential (e.g., high !e" (e.g., high !e" heat et#$heat et#$


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The Effe#t of %lloyi&g o& SteelsThe Effe#t of %lloyi&g o& SteelsElements may be a##e# to steels to $ro#uce the $ro$ertiesElements may be a##e# to steels to $ro#uce the $ro$ertiesre-uire# to ma/e it useful for an a$$lication're-uire# to ma/e it useful for an a$$lication'

0ost elements can have many effects on the $ro$erties of0ost elements can have many effects on the $ro$erties ofsteels'steels'

1ther factors "hich affect material $ro$erties are)1ther factors "hich affect material $ro$erties are)

• The tem$erature reache# before an# #uring "el#ingThe tem$erature reache# before an# #uring "el#ing

• eat in$uteat in$ut

• The cooling rate after "el#ing an# or ,W TThe cooling rate after "el#ing an# or ,W T


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Iron 3e!)Iron

3e!) 0ain steel constituent' 1n its o"n% is relatively soft%0ain steel constituent' 1n its o"n% is relatively soft%#uctile% "ith lo" strength'#uctile% "ith lo" strength'

Carbon C!)Carbon

C!) 0a or alloying element in steels%0a or alloying element in steels% a strengtheninga strengtheningelement "ith ma or influence on .4 har#nesselement "ith ma or influence on .4 har#ness ' Decreases' Decreases"el#ability'"el#ability'

•ty$ically 6 7'258ty$ically 6 7'2580anganese 0n!)0a

nganese 0n!) Secon#ary only to carbon for strength% toughnessSecon#ary only to carbon for strength% toughnessan# #uctility% secon#ary #e(oxi#iser an# also reacts "ithan# #uctility% secon#ary #e(oxi#iser an# also reacts "ithsul$hur to form manganese sul$hi#e'sul$hur to form manganese sul$hi#e'

67'98 is resi#ual from steel #e(oxi#ation 67'98 is resi#ual from steel #e(oxi#ation

•u$ to 6:';8 in C(0n steels! im$roves strength & toughnessu$ to 6:';8 in C(0n steels! im$roves strength & toughness

Silicon Si!)Silicon

Si!) Resi#ual element from steel #e(oxi#ation'Resi#ual element from steel #e(oxi#ation'

•ty$ically to 67'


7/110 Copyright © 2006, TWI LtdWorld Centre for Materials Joining Technology

Steel %lloyi&g Ele'e&tsSteel %lloyi&g Ele'e&ts

,hos$horus ,!),hos $horus ,!) Resi#ual element from steel(ma/ing minerals'Resi#ual element from steel(ma/ing minerals' #ifficult to#ifficult tore#uce belo" 6 7'7:58 brittlenessre#uce belo" 6 7'7:58 brittleness

Sul$hur S!)Sul $hur S!) Resi#ual element from steel(ma/ing mineralsResi#ual element from steel(ma/ing minerals

6 7'7:58 in mo#ern steels 6 7'7:58 in mo#ern steels

6 7'77



Steel %lloyi&g Ele'e&tsSteel %lloyi&g Ele'e&ts

>ic/el >i!>ic/el >i! )) ?se# in stainless steels% high resistance to corrosion?se# in stainless steels% high resistance to corrosionfrom aci#s% increases strength an# toughnessfrom aci#s% increases strength an# toughness

0olyb#enum 0o!0o lyb#enum 0o! )) .ffects har#enability' Steels containing.ffects har#enability' Steels containingmolyb#enum are less susce$tible to tem$er brittleness thanmolyb#enum are less susce$tible to tem$er brittleness thanother alloy steels'other alloy steels' Increases the high tem$erature tensile an#Increases the high tem$erature tensile an#cree$ strengths of steel' ty$ically 6 7'5 to :'78cree$ strengths of steel' ty$ically 6 7'5 to :'78

>iobium >b!>iobium >b! )) a grain refiner% ty$ically6 7'758a grain refiner% ty$ically6 7'758

@ana#ium @!@ana#ium @!)) a grain refiner% ty$ically 6 7'758a grain refiner% ty$ically 6 7'758

Titanium Ti!Titanium Ti!)) a grain refiner% ty$ically 6 7'758a grain refiner% ty$ically 6 7'758

Co$$er Cu!Co$$er Cu! )) $resent as a resi#ual% ty$ically 6 7'



MaterialsMaterials

IronIron FeFe

CarbonCarbon CC is for Strengthis for StrengthManganeseManganese MnMn is for Toughnessis for ToughnessSiliconSilicon SiSi < !"# $eo%idiser< !"# $eo%idiserAluminiumAluminium AlAl &rain re'ner( < ! )# $eo%idiser * Toughness&rain re'ner( < ! )# $eo%idiser * ToughnessChromiumChromium CrCr Corrosion resistanceCorrosion resistanceMolybdenumMolybdenum MoMo +# is for Cree, resistance+# is for Cree, resistance-anadium-anadium -- StrengthStrength.ic/el.ic/el .i.i 0o1 tem,erature a,,lications0o1 tem,erature a,,licationsCo,,erCo,,er CuCu 2sed for 1eathering steels 3Corten42sed for 1eathering steels 3Corten4

Sul,hurSul,hur

SS

5esidual element 3can cause hot shortness45esidual element 3can cause hot shortness4

6hos,horous6hos,horous 66 5esidual element5esidual elementTitaniumTitanium TiTi &rain re'ner( 2sed a a micro alloying element&rain re'ner( 2sed a a micro alloying element

3S7T43S7T4.iobium.iobium .b.b &rain re'ner( 2sed a a micro alloying element&rain re'ner( 2sed a a micro alloying element

3S7T43S7T43S7T4 8 Strength 7 Toughness3S7T4 8 Strength 7 Toughness



Classifi#atio& of SteelsClassifi#atio& of Steels

Steels are classifie# into grou$s as follo"s)Steels are classifie# into grou$s as follo"s)

• ,lain Carbon Steels,lain Carbon Steels

• .lloy Steels.lloy Steels


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.lloy Steels).lloy Steels)• o" .lloy Steelso" .lloy Steels F8 alloying elementsF8 alloying elements

• igh .lloy Steelsigh .lloy Steels GF8 alloying elementsGF8 alloying elements

.lloy Steels are consi#ere# the ty$e of steels that.lloy Steels are consi#ere# the ty$e of steels that$re#ominantly contain$re#ominantly contain extraextra alloying elements other than Ironalloying elements other than Iron& Carbon& Carbon


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Ty$es of Wel#ableTy$es of Wel#able CC %% C(0nC(0n && o" .lloy Steelso" .lloy Steels

o" .lloy Steelso" .lloy Steels

• Strength & toughness raise# even higher by very smallStrength & toughness raise# even higher by very smalla##itions of grain refining elements li/e .luminium%a##itions of grain refining elements li/e .luminium%>iobium% @ana#ium>iobium% @ana#ium

• igher strength gra#es may be referre# to as S . steelsigher strength gra#es may be referre# to as S . steelsigh Strength o" .lloy steels% e'g'% .,I 5 H;5 & higher!igh Strength o" .lloy steels% e'g'% .,I 5 H;5 & higher!


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Ty$es of Wel#ableTy$es of Wel#able o" .lloy Steelso" .lloy Steels

Steels for Elevate# Tem$erature ServiceSteels for Elevate# Tem$erature Service• Chromium Cr! & 0olyb#enum 0o! a##itions give im$rove#Chromium Cr! & 0olyb#enum 0o! a##itions give im$rove#

strength at high tem$erature an# goo# cree$ resistancestrength at high tem$erature an# goo# cree$ resistance• Ty$ical steels are)Ty$ical steels are)

– 2'2582'258 Cr :8 0oCr :8 0o – =8Cr :80o=8Cr :80o

Steels for o" Tem$erature ServiceSteels for o" Tem$erature Service• >i a##itions give goo# toughness at lo" tem$eratures>i a##itions give goo# toughness at lo" tem$eratures

• Steels may be referre# to as cryogenic steelsSteels may be referre# to as cryogenic steels• Ty$ical exam$les are)Ty$ical exam$les are) – i steel – =8>i steels=8>i steels


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Ty$es ofTy$es of Stainless SteelsStainless Steels

.ustenitic Jra#es.ustenitic Jra#es

• .lloye# "ith Chromium & >ic/el.lloye# "ith Chromium & >ic/el

• Exam$les ( on(magnetic

• o" thermal con#uctivity they Ahol#B the heat #uring "el#ing!o" thermal con#uctivity they Ahol#B the heat #uring "el#ing!

• igh coefficient of ex$ansion ( more #istortion #uring "el#ingigh coefficient of ex$ansion ( more #istortion #uring "el#ing


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Stainless Steel Stainless Steel


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Ca!bo& e )i*ale&t +o!')laCa!bo& e )i*ale&t +o!')la

The "el#ability of the material "ill also be affecte# by the amountThe "el#ability of the material "ill also be affecte# by the amountof alloying elements $resent'of alloying elements $resent'

TheThe Carbon E-uivalentCarbon E -uivalent of a given material also #e$en#s on itsof a given material also #e$en#s on itsalloying elementsalloying elements

• The higher theThe higher the CE CE % higher the susce$tibility to brittleness%% higher the susce$tibility to brittleness%

an# lo"er the "el#abilityan# lo"er the "el#ability• TheThe CE CE or CE@ is calculate# using the follo"ing formula)or CE@ is calculate# using the follo"ing formula)

CE@CE@ K 8C K 8C 0n0n Cr 0o @Cr 0o @ Cu >iCu >i;; 55 :5:5


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0il# steel CE 7' !0il# steel CE 7' ! • Rea#ily "el#able% $reheat generally not re-uire# if lo"Rea#ily "el#able% $reheat generally not re-uire# if lo"hy#rogen $rocesses or electro#es are use#hy#rogen $rocesses or electro#es are use#

• ,reheat may be re-uire# "hen "el#ing thic/ section,reheat may be re-uire# "hen "el#ing thic/ sectionmaterial% high restraint an# "ith higher levels of hy#rogenmaterial% high restraint an# "ith higher levels of hy#rogenbeing generate#being generate#

C(0n% me#ium carbon% lo" alloy steels CE 7' to 7'5!C(0n% me#ium carbon% lo" alloy steels CE 7' to 7'5!• Thin sections can be "el#e# "ithout $reheat but thic/erThin sections can be "el#e# "ithout $reheat but thic/er

sections "ill re-uire lo" $reheat levels an# lo" hy#rogensections "ill re-uire lo" $reheat levels an# lo" hy#rogen$rocesses or electro#es shoul# be use#$rocesses or electro#es shoul# be use#

igher carbon an# alloye# steels CE G 7'5!igher carbon an# alloye# steels CE G 7'5! • ,reheat% lo" hy#rogen $rocesses or electro#es% $ost "el#,reheat% lo" hy#rogen $rocesses or electro#es% $ost "el#

heating an# slo" cooling may be re-uire#heating an# slo" cooling may be re-uire#


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P!o#ess C!a# sP!o#ess C!a# s

• y#rogen In#uce#y#rogen In#uce# .4.4 Crac/ingCrac/ing CL0n steels!CL0n steels!• y#rogen In#uce#y#rogen In#uce# Wel# 0etalWel# 0etal Crac/ingCrac/ing S . steels!'S . steels!'

• Soli#ification or ot Crac/ingSoli#ification or ot Crac/ing .ll steels!.ll steels!

• amellar Tearingamellar Tearing .ll steels!.ll steels!• Re(heat Crac/ingRe(heat Crac/ing .ll steels% very susce$tible [email protected] steels% very susce$tible CrL0oL@

steels!steels!

• Inter(Crystalline Corrosion or Wel# DecayInter(Crystalline Corrosion or Wel# Decay stainless steels!stainless steels!


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C!a# i&g C!a# i&g

When consi#ering any ty$e of crac/ing mechanism% threeWhen consi#ering any ty$e of crac/ing mechanism% threeelements must al"ays be $resent)elements must al"ays be $resent)• StressStress

Resi#ual stress is al"ays $resent in a "el#ment%Resi#ual stress is al"ays $resent in a "el#ment%through unbalance# local ex$ansion an# contractionthrough unbalance# local ex$ansion an# contraction

• RestraintRestraintRestraint may be a local restriction% or through $latesRestraint may be a local restriction% or through $latesbeing "el#e# to each other being "el#e# to each other

• Susce$tible microstructureSusce$tible microstructureThe microstructure may be ma#e susce$tible toThe microstructure may be ma#e susce$tible tocrac/ing by the $rocess of "el#ingcrac/ing by the $rocess of "el#ing


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C!a# sC!a# s

y#rogen In#uce# Col# Crac/ingy#rogen In#uce# Col# Crac/ing

d d) d ldd! & I&d)# d C ld


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-yd!oge& I&d)#ed Cold-yd!oge& I&d)#ed ColdC!a# i&g C!a# i&g

.lso /no"n as CC% y#rogen% Toe% ?n#erbea#% Delaye#%.lso /no"n as CC% y#rogen% Toe% ?n#erbea#% Delaye#%

Chevron Crac/ing'Chevron Crac/ing'

1ccurs in)1ccurs in)

• Carbon SteelsCarbon Steels

• Carbon(0anganeseCarbon(0anganese• o"% 0e#ium an# igh .lloy Steels)o"% 0e#ium an# igh .lloy Steels)

• 0ainly in 3erritic or 0artensitic steels'0ainly in 3erritic or 0artensitic steels'

• @ery rarely in Du$lex stainless steels%@ery rarely in Du$lex stainless steels%

• >ever in >ic/el or Co$$er alloys'>ever in >ic/el or Co$$er alloys'


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Crac/ ty$e)Crac/ ty$e) y#rogen .4 & Wel# 0etaly#rogen .4 & Wel# 0etalcrac/ingcrac/ing

ocation)ocation) .4 ongitu#inal!.4 ongitu#inal!Wel# metal Transverse!Wel# metal Transverse!

Steel ty$es)Steel ty$es) .ll har#enable steels.ll har#enable steels

inclu#ing)inclu#ing) S . igh Strength o" .lloy!S . igh Strength o" .lloy!steelssteels

Muench & Tem$ere# steelsMuench & Tem$ere# steelsT0C, thermal mechanicallyT0C, thermal mechanicallycontrolle# $rocesse#! steelscontrolle# $rocesse#! steels

Susce$tible 0icrostructure)Susce$tible 0icrostructure) 0artensite0artensite

-yd!oge& I&d)#ed Cold C!a# i&g -yd!oge& I&d)#ed Cold C!a# i&g

d! & I&d)# d C ldd! & I&d)# d C ld


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There is a ris/ of hy#rogen crac/ing "hen all of the factorsThere is a ris/ of hy#rogen crac/ing "hen all of the factorsoccur together)occur together)

• y#rogeny#rogen 0ore than :5mlL:77g of "el# metal0ore than :5mlL:77g of "el# metal

•StressStress 0ore than N the yiel# stress0ore than N the yiel# stress

•Tem$eratureTem$erature

Oelo"


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0ay occur)0ay occur)

• u$ to F2hrs after com$letionu$ to F2hrs after com$letion

• In "el# metal% .4% $arent metal'In "el# metal% .4% $arent metal'

• .t "el# toes.t "el# toes

• ?n#er "el# bea#s?n#er "el# bea#s

• .t stress raisers'.t stress raisers'



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• y#rogen is the smallest atom /no"ny#rogen is the smallest atom /no"n

• y#rogen enters the "el# via the arcy#rogen enters the "el# via the arc

• Source of hy#rogen mainly from moisture $ic/(u$ on theSource of hy#rogen mainly from moisture $ic/(u$ on theelectro#es coating% "el#ing fluxes or from the consumableelectro#es coating% "el#ing fluxes or from the consumablegasgas

22

2222

2222

0oisture on0oisture onthe electro#ethe electro#eor grease onor grease onthe "irethe "ire

Water va$ourWater va$our

in the air orin the air orin thein theshiel#ing gasshiel#ing gas

1xi#e or grease on1xi#e or grease onthe $latethe $late




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Steel in ex$an#e# con#itionSteel in ex$an#e# con#ition Steel un#er contractionSteel un#er contraction

.tomic.tomicy#rogeny#rogen

!!

.bove


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y#rogen absorbe#in a long% orunstable arc

Hydrogen introduced inweld from consumable,oils, or paint on plate

Cellulosic electro#es$ro#uce hy#rogen as ashiel#ing gas

y#rogeny#rogen

crac/crac/

0artensite forms from P2 #iffuses to P in .4

22

-yd!oge& I&d)#ed Cold C!a# i&g -yd!oge& I&d)#ed Cold C!a# i&g



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Susce$tible 0icrostructure)Susce$tible 0icrostructure)

ar# brittle structure 0.RTE>SITE ,romote# by)ar# brittle structure 0.RTE>SITE ,romote# by)

.!.! igh Carbon Content% Carbon E-uivalent CE!igh Carbon Content% Carbon E-uivalent CE!

eat in$ut Q Lmm!eat in$ut Q Lmm! K .m$s x @olts x arc timeK .m$s x @olts x arc time

Run out length x :7Run out length x :7 i Cu>i Cu ; 5 :5; 5 :5

O!O! high alloy contenthigh alloy content

C!C! fast cooling rate)fast cooling rate) Ina#e-uate ,re( eatingIna#e-uate ,re( eatingCol# 0aterialCol# 0aterial

Thic/ 0aterialThic/ 0aterial

o" eat In$ut'o" eat In$ut'

Eff # f # !b & i& h ! ! iEff #t f # !b & i& th ! !ti


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0 0.1 0.2 0.3 0.4 0.5 0. 0.! 0." 0.# 1.0 1.2 1.4 1.$%arbon

Ductility

ar#nessTensile

Strength

0."3 $ %arbon&'utectoid(

Increasing the carbon content "ill increase the strength% but"ill also increase greatly the ris/ of formation of 0artensite

Effe#t of #a!bo& i& the !o e!tiesEffe#t of #a!bo& i& the !o e!tiesof i!o&of i!o&

d! & I&d)# d C ldd! g & I&d)# d C ld


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Ty$ical locations for Col# Crac/ingTy$ical locations for Col# Crac/ing

d! g & I&d)# d C ldd!oge& I&d)#ed Cold


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y#rogen in#uce#y#rogen in#uce#"el# metal crac/ing"el# metal crac/ing

y#rogen in#uce#y#rogen in#uce#.4 crac/ing.4 crac/ing

0icro .lloye# Steel0icro .lloye# Steel Carbon 0anganese SteelCarbon 0anganese Steel


d! g & I&d)# d C ldyd!oge& I&d)#ed Cold


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Toe crac/ingToe crac/ing?n#er bea# crac/ing?n#er bea# crac/ing

d! g & I&d)# d C ldyd!oge& I&d)#ed Cold


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Toe crac/ing in 00. fillet "el#Toe crac/ing in 00. fillet "el#


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yd!oge& I&d)#ed Coldyd!oge& I&d)#ed Cold


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,recautions for controlling hy#rogen crac/ing,recautions for controlling hy#rogen crac/ing

• ,re heat% removes moisture from the oint $re$arations% an#,re heat% removes moisture from the oint $re$arations% an#slo"s #o"n the cooling rateslo"s #o"n the cooling rate

• Ensure oint $re$arations are clean an# free fromEnsure oint $re$arations are clean an# free fromcontaminationcontamination

• The use of a lo" hy#rogen "el#ing $rocess an# correct arcThe use of a lo" hy#rogen "el#ing $rocess an# correct arclengthlength

• Ensure all "el#ing is carrie# out is carrie# out un#erEnsure all "el#ing is carrie# out is carrie# out un#ercontrolle# environmental con#itionscontrolle# environmental con#itions

• Ensure goo# fit(u$ as to re#uce# stressEnsure goo# fit(u$ as to re#uce# stress

• The use of a ,W TThe use of a ,W T

• .voi# $oor "el# $rofiles.voi# $oor "el# $rofiles


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-yd!oge& S#ales-yd!oge& S#aleslist of hy#rogen scales from OS E> :7::)$art 2'list of hy#rogen scales from OS E> :7::)$art 2'

y#rogen content relate# to :77 grams of "el# metaly#rogen content relate# to :77 grams of "el# metal#e$osite#'#e$osite#'

• ScaleScale .. igh)igh) GG:5 ml:5 ml

•ScaleScale

OO

0e#ium)0e#ium)

:7 ml ( :5 ml:7 ml ( :5 ml

• ScaleScale CC o")o") 5 ml ( :7 ml5 ml ( :7 ml

• ScaleScale DD @ery lo")@ery lo") < ml ( 5 ml< ml ( 5 ml

• ScaleScale EE ?ltra(lo")?ltra(lo") < ml< ml

Pote&tial yd!oge& Le*elPote&tial yd!oge& Le*el


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Pote&tial -yd!oge& Le*elPote&tial -yd!oge& Le*elP!o#essesP!o#esses

list of "el#ing $rocesses in or#er of $otential lo"est hy#rogenlist of "el#ing $rocesses in or#er of $otential lo"est hy#rogen

content "ith regar#s to :77g of #e$osite# "el# metal'content "ith regar#s to :77g of #e$osite# "el# metal'

•TIJTIJ < ml < ml

•0IJ0IJ 5 ml 5 ml

•ESWESW 5 ml 5 ml

•00. Oasic Electro#es!00. Oasic Electro#es! 5 ml 5 ml

•S.WS.W :7ml :7ml

•3C.W3C.W :5 ml :5 ml

yd!oge& I&d)#ed Coldyd!oge& I&d)#ed Cold


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Ty$ical ,rocess y#rogen evelsTy$ical ,rocess y#rogen evels

yd!oge& Cold C!a# i&gyd!oge& Cold C!a# i&g


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• y#rogeny#rogen

• StressStress

• Tem$eratureTem$erature

• ar#nessar#ness

• 00. basic electro#es!' 0.J00. basic electro#es!' 0.J Cleaning "el# $re$ etc'Cleaning "el# $re$ etc'

• Design% Oalance# "el#ing'Design% Oalance# "el#ing'

• eat to


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-yd!oge& Cold C!a# i&g-yd!oge& Cold C!a# i&g %*oidae %*oidae

Re#uce y#rogen evelRe#uce y#rogen evel

• Select lo"er hy#rogen $otential $rocess e'g'Select lo"er hy#rogen $otential $rocess e'g'

O.SIC vs' R?TI EO.SIC vs' R?TI E

0.J vs' 00.0.J vs' 00.

• Increase hy#rogen #iffusion "ith increase# $reheatIncrease hy#rogen #iffusion "ith increase# $reheat

• 0aintain $reheat after "el#ing allo"ing #iffusion from "el#0aintain $reheat after "el#ing allo"ing #iffusion from "el#

• Oa/e basic 00. electro#esLS.W fluxes ( manufacturersOa/e basic 00. electro#esLS.W fluxes ( manufacturersrecommen#ationsrecommen#ations

• CleanlinessL#ryness of consumables an# "el# $re$arationsCleanlinessL#ryness of consumables an# "el# $re$arationse'g' rust scale grease cutting flui#se'g' rust scale grease cutting flui#s

• ?se austenitic or nic/el fillers?se austenitic or nic/el fillers


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eat in$ut Keat in$ut K :'; /*Lmm:'; /*Lmm

.m$s K 277.m$s K 277

@olts K


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-eat I& )t -eat I& )t igh heat in$ut ( slo" coolingigh heat in$ut ( slo" cooling

• o" toughness grain gro"th!o" toughness grain gro"th!

• Re#uction in yiel# strengthRe#uction in yiel# strength

o" heat in$ut ( fast coolingo" heat in$ut ( fast cooling

• Increase# har#nessIncrease# har#ness

• y#rogen entra$menty#rogen entra$ment

• ac/ of fusionac/ of fusion


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esid)al St!essesid)al St!essResi#ual stress "ill be increase# by)Resi#ual stress "ill be increase# by)

• Increasing $late thic/nessIncreasing $late thic/ness

• Restraint (Restraint ( rigi# fixturesrigi# fixtures"el# volume"el# volumeinsert in $lateinsert in $late

• 0ulti($ass vs' single $ass0ulti($ass vs' single $ass

• Small "el# bea#s vs' large "el# bea#sSmall "el# bea#s vs' large "el# bea#s

-yd!oge& Cold C!a# i&g-yd!oge& Cold C!a# i&g


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-yd!oge& Cold C!a# i&g-yd!oge& Cold C!a# i&g %*oidae %*oidae

,revention,revention• Slo" the cooling rateSlo" the cooling rate

• Re#uce hy#rogen levelRe#uce hy#rogen level

• Re#uce resi#ual stressRe#uce resi#ual stress

-yd!oge& Cold C!a# i&g-yd!oge& Cold C!a# i&g


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yd!oge& Cold C!a# i&gyd!oge& Cold C!a# i&g %*oidae %*oidae

o" to Re#uce Resi#ual Stresso" to Re#uce Resi#ual Stress• Ensure goo# fit(u$) ( minimum root ga$ an# misalignmentEnsure goo# fit(u$) ( minimum root ga$ an# misalignment

• .voi# restraints) ( ,reset the oin.voi# restraints) ( ,reset the oin

• ,reheat may hel$) ( to slo" #o"n cooling rate,reheat may hel$) ( to slo" #o"n cooling rate

• arge "el# $asses) ( higher #e$osition ratearge "el# $asses) ( higher #e$osition rate• 0inimise volume of "el# metal) ( ess resi#ual stress0inimise volume of "el# metal) ( ess resi#ual stress

• ,W T from $reheat tem$,W T from $reheat tem$

• Dress "el# toes at $reheat tem$Dress "el# toes at $reheat tem$


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Co'bi&ed Thi# &essCo'bi&ed Thi# &ess

Combine# chilling effect of oint ty$e an#Combine# chilling effect of oint ty$e an#thic/ness'thic/ness'


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The Chilling Effect of the *ointThe Chilling Effect of the *oint


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The Chilling Effect of the *ointThe Chilling Effect of the *oint


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The Chill Effe#t of the /ate!ial The Chill Effe#t of the /ate!ial


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P!e"heat % li#atio&P!e"heat % li#atio&.$$lication 1f ,reheat.$$lication 1f ,reheat

• eat either si#e of ointeat either si#e of oint

• 0easure tem$ 2mins after heat removal0easure tem$ 2mins after heat removal

• .l"ays best to heat com$lete com$onent rather than local.l"ays best to heat com$lete com$onent rather than local

if $ossible to avoi# #istortionif $ossible to avoi# #istortion• ,reheat al"ays higher for fillet than butt "el#s #ue to,reheat al"ays higher for fillet than butt "el#s #ue to

#ifferent combine# thic/nesses an# chill effect factors'#ifferent combine# thic/nesses an# chill effect factors'


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P!e"heat % li#atio&P!e"heat % li#atio&3urnace3urnace (( heating entire com$onent ( bestheating entire com$onent ( best

Electrical elementsElectrical elements (controllable ,ortable Site use Clean(controllable ,ortable Site use CleanCom$onent cannot be move#'Com$onent cannot be move#'

Jas burnersJas burners ( #irect flame im$ingement ,ossible local( #irect flame im$ingement ,ossible localoverheating ess controllable ,ortable 0anualoverheating ess controllable ,ortable 0anualo$eration $ossible Com$onent can be move#'o$eration $ossible Com$onent can be move#'

Ra#iant gas heatersRa#iant gas heaters ( ca$able of automatic control >o flame( ca$able of automatic control >o flameim$ingement >o contact "ith com$onent ,ortable'im$ingement >o contact "ith com$onent ,ortable'

In#uction heatingIn#uction heating ( controllable Ra$i# heating mins not( controllable Ra$i# heating mins nothours! arge $o"er su$$ly Ex$ensive e-ui$menthours! arge $o"er su$$ly Ex$ensive e-ui$ment


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0anual Jas 1$eration0anual Jas 1$eration

P!e"-eat % li#atio&P!e"-eat % li#atio&

Electrical eate# ElementsElectrical eate# Elements

) l


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-eati&g Te' e!at)!e Co&t!ol -eati&g Te' e!at)!e Co&t!ol • TE0,I STICQS ( crayons% melt at set tem$s' Will notTE0,I STICQS ( crayons% melt at set tem$s' Will not

measure max tem$'measure max tem$'

• ,yrometers ( contact or remote% measure actual tem$',yrometers ( contact or remote% measure actual tem$'

• Thermocou$les ( contact or attache#% very accurate%Thermocou$les ( contact or attache#% very accurate%measure actual tem$'measure actual tem$'


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d%* idi& ICC


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%*oidi&g -ICC %*oidi&g -ICC

• 0aintain calculate# $reheats% an#0aintain calculate# $reheats% an# never never allo" the inter($assallo" the inter($asstem$erature to go belo" the $re(heat valuetem$erature to go belo" the $re(heat value

• ?se?se o" y#rogeno" y#rogen $rocesses "ith short arcs & ensure$rocesses "ith short arcs & ensureconsumables are correctly ba/e# & store# as re-uire#consumables are correctly ba/e# & store# as re-uire#

• If using a cellulosicIf using a cellulosic E ;7:7E ;7:7 for the root run% insert the Ufor the root run% insert the U ot $assot $ass VVas soon as $ossible' Oefore .4


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C!a# sC!a# s

Soli#ification Crac/ingSoli#ification Crac/ing

S lidifi# i & C! # i&S lidifi# i & C! # i&


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?sually 1ccurs in Wel# Centerline?sually 1ccurs in Wel# Centerline

Solidifi#atio& C!a# i&g Solidifi#atio& C!a# i&g

S lidifi# i & C! # i&S lidifi# i & C! # i&


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Solidifi#atio& C!a# i&g Solidifi#atio& C!a# i&g .lso referre# as.lso referre# as -ot C!a# i&g -ot C!a# i&g

Crac/ ty$e)Crac/ ty$e) Soli#ification crac/ingSoli#ification crac/ing

ocation)ocation) Wel# centreline longitu#inal!Wel# centreline longitu#inal!

Steel ty$es)Steel ty$es) igh sul$hur & $hos$horigh sul$hur & $hos$horconcentration in steels'concentration in steels'

Susce$tibleSusce$tible 0icrostructure)0icrostructure) Columnar grains In #irection ofColumnar grains In #irection ofsoli#ificationsoli#ification

Solidifi#atio& C!a# i&gSolidifi#atio& C!a# i&g


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• Sul$hur in the $arent material may #ilute in the "el# metalSul$hur in the $arent material may #ilute in the "el# metalto form iron sul$hi#es lo" strength% lo" melting $ointto form iron sul$hi#es lo" strength% lo" melting $ointcom$oun#s!com$oun#s!

• During "el# metal soli#ification% columnar crystals $ushDuring "el# metal soli#ification% columnar crystals $ushstill li-ui# iron sul$hi#es in front to the last $lace ofstill li-ui# iron sul$hi#es in front to the last $lace of

soli#ification% "el# centerlinesoli#ification% "el# centerline• The bon#ing bet"een the grains "hich are themselvesThe bon#ing bet"een the grains "hich are themselves

un#er great stress' may no" be very $oor to maintainun#er great stress' may no" be very $oor to maintaincohesion an# a crac/ "ill result% "el# centerlinecohesion an# a crac/ "ill result% "el# centerline

S lidifi# i & C! # i&S lidifi# ti & C! # i&


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3actors for soli#ification crac/ing3actors for soli#ification crac/ing

• Columnar grain gro"th "ith im$urities in "el# metalColumnar grain gro"th "ith im$urities in "el# metalsul$hur% $hos$hor an# carbon!sul$hur% $hos$hor an# carbon!

• The amount of stressLrestraintThe amount of stressLrestraint

• *oint #esign high #e$th to "i#th ratios*oint #esign high #e$th to "i#th ratios

• i-ui# iron sul$hi#es are forme# aroun# soli#ifying grains'i-ui# iron sul$hi#es are forme# aroun# soli#ifying grains'

• igh contractional strains are $resentigh contractional strains are $resent

• igh #ilution $rocesses are being use#'igh #ilution $rocesses are being use#'

• There is a high carbon content in the "el# metalThere is a high carbon content in the "el# metal

• 0ost commonly occurring in sub(arc "el#e# oints0ost commonly occurring in sub(arc "el#e# oints



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)i*uid +ron ulp-idefilms

olidificationcrac

%ontractional strain


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S lidifi# ti & C! # i&S lidifi# ti & C! # i&g


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Crac/ing li/ely

27mm

5mm

Wi#th K 7'FDe$th

5 K 7'2527

igher #ilution levelsfaster cooling

Crac/ing unli/ely

Wi#th K G 7'FDe$th

:5 K 7'F527

:5mm

27mm

o"er #ilution levels slo"er cooling

De$th to Wi#th RatiosDe$th to Wi#th Ratios


S lidifi# ti & C! # i&S lidifi# ti & C! # i&g


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,recautions for controlling soli#ification crac/ing,recautions for controlling soli#ification crac/ing

•The first ste$s in eliminating this $roblem "oul# be to choose aThe first ste$s in eliminating this $roblem "oul# be to choose alo" #ilution $rocess% an# change the oint #esignlo" #ilution $rocess% an# change the oint #esign

Jrin# an# seal in any lamination an# avoi# further #ilutionXXXXJrin# an# seal in any lamination an# avoi# further #ilutionXXXX

.## 0anganese to the electro#e to form s$herical 0nLS "hich.## 0anganese to the electro#e to form s$herical 0nLS "hichform bet"een the grain an# maintain grain cohesionform bet"een the grain an# maintain grain cohesion

.s carbon increases the 0nLS ratio re-uire# increases.s carbon increases the 0nLS ratio re-uire# increasesex$onentially an# is a ma or factor' Carbon content 8 shoul# beex$onentially an# is a ma or factor' Carbon content 8 shoul# bea minimise# by careful control in electro#e an# #ilutiona minimise# by careful control in electro#e an# #ilution

imit the heat in$ut% hence lo" contraction% & minimise restraintimit the heat in$ut% hence lo" contraction% & minimise restraint


S lidifi# ti & C! # i&gSolidifi#atio& C!a# i&g


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,recautions for controlling soli#ification crac/ing,recautions for controlling soli#ification crac/ing

• The use of high manganese an# lo" carbon content fillersThe use of high manganese an# lo" carbon content fillers

• 0inimise the amount of stress L restraint acting on the oint0inimise the amount of stress L restraint acting on the oint#uring "el#ing#uring "el#ing

• The use of high -uality $arent materials% lo" levels ofThe use of high -uality $arent materials% lo" levels ofim$urities ,hos$hor & sul$hur!im$urities ,hos$hor & sul$hur!

• Clean oint $re$arations contaminants oil% grease% $aintsClean oint $re$arations contaminants oil% grease% $aintsan# any other sul$hur containing $ro#uct!an# any other sul$hur containing $ro#uct!

• *oint #esign selection #e$th to "i#th ratios*oint #esign selection #e$th to "i#th ratios


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p-erical /n ulp-ide ballsform bet"een solidifiedgrains

%o-esion and strengt-between grainsremains

%ontractional strain

.## 0anganese to "el#metal

Text ,age Ref 22)9

S lidifi# ti & C! # i&gSolidifi#atio& C!a# i&g


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Solidifi#atio& C!a# i&g Solidifi#atio& C!a# i&g Soli#ification crac/ing in .ustenitic Stainless SteelSoli#ification crac/ing in .ustenitic Stainless Steel

• $articularly $rone to soli#ification crac/ing$articularly $rone to soli#ification crac/ing

• large grain si+e gives rise to a re#uction in grain boun#arylarge grain si+e gives rise to a re#uction in grain boun#aryarea "ith high concentration of im$uritiesarea "ith high concentration of im$urities

• .ustenitic structure very intolerant to contaminants.ustenitic structure very intolerant to contaminantssul$hur% $hos$horous an# other im$urities!'sul$hur% $hos$horous an# other im$urities!'

• igh coefficient of thermal ex$ansion L o" coefficient ofigh coefficient of thermal ex$ansion L o" coefficient ofthermal con#uctivity% "ith high resultant resi#ual stressthermal con#uctivity% "ith high resultant resi#ual stress

• same $recautions against crac/ing as for $lain carbonsame $recautions against crac/ing as for $lain carbonsteels "ith extra em$hasis on thorough cleaning an# highsteels "ith extra em$hasis on thorough cleaning an# high#ilution controls'#ilution controls'

C!a# sC!a# s


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C!a# sC!a# s

amellar Tearingamellar Tearing

FACT95S F95 0AME00A5FACT95S F95 0AME00A5


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TEA5I.&TEA5I.&

• Occurs in susceptible material ith poorOccurs in susceptible material ith poorthrough thic!ness ductility "alues #20$%through thic!ness ductility "alues #20$% • &ssociated ith rolled steels%&ssociated ith rolled steels%

• 'on metallic inclusions in the steel%'on metallic inclusions in the steel%

• Thermal stresses as the eld contracts% Thermal stresses as the eld contracts%


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FACT95S F95 0AME00A5FACT95S F95 0AME00A5


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TEA5I.&!TEA5I.&!

Thermal stresses% Thermal stresses%

Contraction o) deposited eld metal createsContraction o) deposited eld metal creates

localised strains%localised strains%I) these localised strains e*ceed the yieldI) these localised strains e*ceed the yieldstrength o) the base material in the throughstrength o) the base material in the throughthic!ness direction, lamellar tearing ill result%thic!ness direction, lamellar tearing ill result%

0AME00A5 TEA5I &0AME00A5 TEA5I &


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0AME00A5 TEA5I.&0AME00A5 TEA5I.&

STRA TESTSTRA TEST


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STRA TEST.STRA TEST.


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LAMELLAR TEARINGLAMELLAR TEARING


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LAMELLAR TEARING

Lamellar Tearing along the )usionLamellar Tearing along the )usionboundary%boundary%

'ote the characteristic step li!e'ote the characteristic step li!eappearanceappearance

AVOIDANCE OF LAMELLAR AVOIDANCE OF LAMELLAR


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TEARINGTEARING

• -se steels ith good through thic!ness-se steels ith good through thic!nessductility in the . direction%ductility in the . direction%

• Change /oint design%Change /oint design%

• Carry out appropriate testing asCarry out appropriate testing asnecessary, T+&, -T or both%necessary, T+&, -T or both%

• -se a buttering techni1ue to )orm a ductile-se a buttering techni1ue to )orm a ductilepad%pad%

• +educe restraint+educe restraint


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La'ella! Tea!i&gLa'ella! Tea!i&g


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La ella! Tea!i&g La ella! Tea!i&g

• ocation)ocation) ,arent metal,arent metal

• Steel Ty$e)Steel Ty$e) .ny steel ty$e $ossible.ny steel ty$e $ossible

• Susce$tible 0icrostructure)Susce$tible 0icrostructure) ,oor through thic/ness,oor through thic/ness#uctility#uctility



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La ella! Tea!i&g La ella! Tea!i&g • amellar tearing has a ste$ li/e a$$earance #ue to the soli#amellar tearing has a ste$ li/e a$$earance #ue to the soli#

inclusions in the $arent material e'g' sul$hi#es an#inclusions in the $arent material e'g' sul$hi#es an#silicates! lin/ing u$ un#er the influence of "el#ing stressessilicates! lin/ing u$ un#er the influence of "el#ing stresses

• o" #uctile materials in the short transverse #irectiono" #uctile materials in the short transverse #irectioncontaining high levels of im$urities are very susce$tible tocontaining high levels of im$urities are very susce$tible tolamellar tearinglamellar tearing

• It forms "hen the "el#ing stresses act in the shortIt forms "hen the "el#ing stresses act in the shorttransverse #irection of the material through thic/nesstransverse #irection of the material through thic/ness#irection!#irection!



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3actors for lamellar tearing to occur 3actors for lamellar tearing to occur

• o" -uality $arent materials% high levels of im$uritieso" -uality $arent materials% high levels of im$urities

• *oint #esign% #irection of stress*oint #esign% #irection of stress

• The amount of stress acting across the oint #uring "el#ingThe amount of stress acting across the oint #uring "el#ing

• >ote) very susce$tible oints may form lamellar tearing>ote) very susce$tible oints may form lamellar tearingun#er very lo" levels of stressun#er very lo" levels of stress


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Critical areaCritical area

CriticalCritical

areaarea

Critical areaCritical area




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0o#ifying a Tee oint to avoi# lamellar tearing0o#ifying a Tee oint to avoi# lamellar tearing

Susce$tibleSusce$tible

Susce$tibleSusce$tible Im$rove#Im$rove#

>on(susce$tible>on(susce$tible

>on(susce$tible>on(susce$tible

Jouge base metalJouge base metalan# fill "ith "el#an# fill "ith "el#metal beforemetal before"el#ing the oint"el#ing the oint

Susce$tibleSusce$tible ess susce$tibleess susce$tible

,rior buttering of the oint,rior buttering of the oint"ith a #uctile layer of "el#"ith a #uctile layer of "el#metal may avoi# lamellarmetal may avoi# lamellartearingtearing




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0o#ifying a corner oint to avoi# lamellar tearing0o#ifying a corner oint to avoi# lamellar tearing

Susce$tibleSusce$tible >on(Susce$tible>on(Susce$tible

,rior "el#ing both,rior "el#ing both$lates may be groove#$lates may be groove#to avoi# lamellar tearingto avoi# lamellar tearing

.n o$en corner oint.n o$en corner ointmay be selecte# tomay be selecte# toavoi# lamellar tearingavoi# lamellar tearing



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Sho!t Te&sile (Th!o)gh Thi# &ess$Sho!t Te&sile (Th!o)gh Thi# &ess$T


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The short tensile test or through thic/ness test is aThe short tensile test or through thic/ness test is a

test to #etermine a materials susce$tibility totest to #etermine a materials susce$tibility tolamellar tearinglamellar tearing

3riction Wel#e# Ca$s3riction Wel#e# Ca$s

Short Tensile S$ecimenShort Tensile S$ecimen

ThroughThroughThic/nessThic/ness

DuctilityDuctility

Sam$le of ,arent 0aterialSam$le of ,arent 0aterial

The results are given as aThe results are given as a STR.STR. valuevalueShort Transverse Re#uction in .reaShort Transverse Re#uction in .rea

Test Test



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Crac/ ty$e)Crac/ ty$e) amellar tearingamellar tearing

ocation)ocation) Oelo" "el# .4Oelo" "el# .4

Steel ty$es)Steel ty$es) igh sul$hur & $hos$horous steelsigh sul$hur & $hos$horous steels

0icrostructure)0icrostructure) amination & Segregationamination & Segregation



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1ccurs "hen)1ccurs "hen)

• igh contractional strains are through the short transverseigh contractional strains are through the short transverse#irection' There is a high sulfur content in the base metal'#irection' There is a high sulfur content in the base metal'

• There is lo" through thic/ness #uctility in the base metal'There is lo" through thic/ness #uctility in the base metal'

• There is high restraint on the "or/There is high restraint on the "or/

La'ella! Tea!i&g La'ella! Tea!i&g


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igh contractionalstrains

amellar tear

Restraint

Text ,age Ref 22)=

a e a! ea! &gg



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.ssessment of susce$tibility to amellarTearing)

• Carry out through thic/ness tensile test

• Carry out cruciform "el#e# tensile test



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La'ella! Tea!i&g La'ella! Tea!i&g


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e designweld

rind and infill wit-

ductile weld metal%ontrolrestraint

or critical wor aforged piece may beused

3orge# T

,iece

gg

C!a# sC!a# s


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Wel# DecayWel# Decay

I&te!"G!a&)la! Co!!osio&I&te!"G!a&)la! Co!!osio&


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))

.lso /no"n as Wel# Decay.lso /no"n as Wel# Decay

• ocation) Wel# .4' longitu#inalocation) Wel# .4' longitu#inal

• Steel Ty$e) .ustenitic stainless steelsSteel Ty$e) .ustenitic stainless steels

• Susce$tible 0icrostructure) Sensitise# .4 grainSusce$tible 0icrostructure) Sensitise# .4 grain

boun#ariesboun#aries



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))• Wel# Decay%Wel# Decay% Intergranular CorrosionIntergranular Corrosion or /nife line attac/%or /nife line attac/%

may occur in austenitic stainless steelsmay occur in austenitic stainless steels• .t the critical range of ;77(957.t the critical range of ;77(957 oo C Chromium carbi#eC Chromium carbi#e

$reci$itation at the grain boun#aries ta/es $lace$reci$itation at the grain boun#aries ta/es $lace

• .t this tem$erature range chromium is absorbe# by the.t this tem$erature range chromium is absorbe# by the

carbon at the grain boun#aries% "hich causes a localcarbon at the grain boun#aries% "hich causes a local#e$letion of chromium content in the a# acent areas#e$letion of chromium content in the a# acent areas

• The #e$letion of chromium content in the affecte# areasThe #e$letion of chromium content in the affecte# areasresults in lo"ering the materials resistance to corrosionresults in lo"ering the materials resistance to corrosionattac/% allo"ing rusting to occur'attac/% allo"ing rusting to occur'



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))

Sensitisation range "here $ea/ tem$eratures in the .4Sensitisation range "here $ea/ tem$eratures in the .4reaches about ;77reaches about ;77 77 C to 957C to 957 77 CC



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))

When heate# in the range ;77When heate# in the range ;77 77CC

to 957to 957 77C Chromium Carbi#esC Chromium Carbi#esform at the grain boun#ariesform at the grain boun#aries

Chromium migrates to site ofChromium migrates to site ofgro"ing carbi#egro"ing carbi#e



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))

Jrain boun#ary a# acent areas become #e$lete# of chromiumJrain boun#ary a# acent areas become #e$lete# of chromiuman# lose their corrosion resistancean# lose their corrosion resistance

.reas #e$lete# of.reas #e$lete# ofChromium belo" :2'58Chromium belo" :2'58



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))

WELD DEC%0 WELD DEC%0


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• ,recautions against Wel# Decay,recautions against Wel# Decay

• ?sing lo" carbon gra#e stainless steel e'g'


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M? :'M? :' Oriefly #iscuss the four essential factors for hy#rogencrac/ing to occur

M? 2'M? 2' State four $recautions to re#uce the chance ofhy#rogen crac/ing

M?


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g

Reheat or Stress relaxation crac/ingReheat or Stress relaxation crac/ing1ccurs in the .4 of "el#s in o" alloy steels #uring ,W T or1ccurs in the .4 of "el#s in o" alloy steels #uring ,W T or

#uring service at elevate# tem$eratures#uring service at elevate# tem$eratures3actors contributing for Reheat crac/ing)3actors contributing for Reheat crac/ing)• Susce$tible alloy com$ositionSusce$tible alloy com$osition• Susce$tible microstructureSusce$tible microstructure

• igh level of resi#ual strain combine# "ith some #egree of tri(igh level of resi#ual strain combine# "ith some #egree of tri(axialityaxiality

• Tem$erature in the strain relaxation cree$! rangeTem$erature in the strain relaxation cree$! range

0ost alloy steels suffer some #egree of embritlement in the0ost alloy steels suffer some #egree of embritlement in the

coarse grain area of the .4 "hen heate# at ;77Ccoarse grain area of the .4 "hen heate# at ;77CThe crac/s are intergranular The crac/s are intergranular


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Cooli&g ateCooli&g ate


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,lain Carbon,lain CarbonSteel ofSteel ofEutectoi#Eutectoi#Com$ositionCom$osition

1-Weld Process Crack Mechanisms. Rev 1

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