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WELDING INSPECTION - STEELS

CONTENTS PAGE

TERMINOLOGY 3

THE DUTIES OF A WELDING INSPECTOR 9

CODES AND STANDARDS 12

THE WELDING PROCEDURE 14

DESTRUCTIVE TESTING 20

SYMBOLS 27

MATERIALS 32

FOUR FACTORS FOR ESTABLISHING A WELD 37

WELDABILITY 38

RESIDUAL STRESS AND DISTORTION 44

HEAT TREATMENT 47

CALIBRATION 49

DEFECTS DETECTED BY SURFACE INSPECTION 0

INTERNAL DEFECTS 4

MACRO E!AMINATION 8

NON-DESTRUCTIVE TESTING "1

REPAIR BY WELDING ""

CONSUMABLES 70

WELDING POSITIONS 7

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WELDING PROCESSES

MANUAL METAL ARC WELDING 78

TUNGSTEN INERT GAS WELDING 83

METAL INERT GAS WELDING 88

SUBMERGED ARC WELDING 94

AUTOMATIC METAL ARC WELDING 101

ELECTRON BEAM WELDING 103

ELECTRO-SLAG WELDING 10

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TERMINOLOGY

Use of the correct terminology is important. CSWP !ses BS 499 #$%&'%('. "re#!ently the terms$%el&' an& $(oint' are !se& incorrectly. E)act &efinitions are gi*en in BS 499 PT 1 1983 +$Wel&ing terminology' an& BS 499 P$ 2) 1980$ Wel& sym,ols'.

TYPES OF WELD

B*$$ W+,'

F,,+$ W+,'

E'.+ W+,'

small in&entationsat each %el&

S/$ W+,' -ll!stration &epicts resistance

%el&.Spot %el&s can ,e ma&e %ith

G or TG processes./

The fo!r ,asic %el&s can ,e !se& to (oin *ario!s types of (oints.

0

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TYPES OF OINTThe follo%ing are some typical (oints

BUTT

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

TEE

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

CORNER

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

LAP

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PLATE EDGE PREPARATION FOR BUTT WELDS

The ill!strations sho% stan&ar& terminology for the *ario!s feat!res of plate e&ge preparations.

S#!are e&ge& close& ,!tt S#!are e&ge& open ,!tt %ith ,ac3ing

strip

0 mm + plate -consi&erations + penetration control5

,ac3ing strip of the same material an&!s!ally remo*e&/

6ac3ing ,ar + ceramic or copper "!si,le insert + electric ,olt -e.,/ -copper can ca!se lo#!ation crac3ing/ -!ses TG process/

S&.,+ V S&.,+ ++,

D*,+ V D*,+ ++,

S&.,+ S&.,+ U

D*,+ D*,+ U

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incl!&e& angle

,e*el angle

,e*el angle %i&th

si&e%all

face ra&i!s

root face root gap lan&

FEATURES OF A COMPLETED WELD

A ,!tt %el& in plate5 ma&e ,y %el&ing from ,oth si&es5 has t%o %el& faces an& fo!r toes. n a f!llpenetration %el& ma&e from one si&e5 the protr!&ing %el& on the !n&ersi&e is calle& thepenetration ,ea&5 %hich also has t%o toes. The root is &efine& -6S 88/ as the 9one on the si&eof the first r!n farthest from the %el&er.

toe face toe

root

toe face toef a %el& is sectione&5 polishe& an& etche&5 the f!sion ,o!n&ary can ,e esta,lishe&. etal lying

,et%een the t%o f!sion ,o!n&aries is %el& metal + a mi)t!re of &eposite& metal an& plate metalthat has ,een melte&. The f!sion 9one is the area of highest &il!tion ,et%een filler metal an&

parent plate. A&(acent to the f!sion ,o!n&ary is the heat affecte& 9one -:A;/5 in %hich the platematerial has ha& its metall!rgical str!ct!re mo&ifie& ,y the heat of %el&ing.

e)cess %el& metal

f!sion 9one

throat f!sion ,o!n&ary < line

:A;

E)cess %el& metal is the correct term5 not $ %el& reinforcement'. E)cess %el& metal lying o!tsi&ethe plane (oining the toes of the %el&.

"illet %el&s ha*e similar feat!res.

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Toes"ace

f!sion ,o!n&ary

root :A;

The shape of a fillet in cross+section is &escri,e& in three terms.

M$(+ ,,+$ 5&+6 ,,+$ C&5%+ ,,+$

A con*e) fillet has a poor toe ,len& + greater notch effect an& sharper angle at toe5 not !se& infatig!e sit!ations. A conca*e fillet has a ,etter toe ,len& for fatig!e sit!ations5 ho%e*er a re&!ce&throat. The conca*e %el& may ,e ma&e ,y %el&ing alone or ,y s!,se#!ent grin&ing.

SIE OF WELDS

"!ll Penetration 6!tt Wel&s.

The general r!les are &esign throat thic3ness > thic3ness of the thinner part (oine&.Cap %i&th > prep %i&th ? 1@ either si&e -for open prep5 not specifie& in 6S 88/

Partial Penetration 6!tt Wel&s.The term partial penetration strictly implies ,!tt %el&s that are &esigne& to ha*e less than f!ll

penetration. "ail!re to achie*e f!ll penetration %hen it is %ante& sho!l& ,e liste& as the &efectincomplete penetration.The &esign throat thic3ness of a partial penetration %el& is t1an& the act!al throat thic3ness is t2.With a partial penetration %el& ma&e from ,oth si&es5 the &esign throat thic3ness is t1? t1an& theact!al throat thic3ness is t2? t2. Note that the &egree of penetration m!st ,e 3no%n.

t1 t2 t2 t1

t1 t2 t1 t2

t1 t2

t1

t2

B

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F,,+$ W+,'#.

"illet %el& si9es are calc!late& ,y reference to allo%a,le shear stress on the throat area5 i.e.Throat area > &esign throat thic3ness ) length of %el&.The si9e re#!ire& is specifie& on &ra%ings in terms of leg length -l/."or fillet %el&s %ith e#!al leg lengths l> 1. t1. This &oes not apply to conca*e fillet %el&s.

l

l t1> t2 t1 t1 t1 t1 t2 t2

f an asymmetrical %el& is re#!ire&5 ,oth leg lengths are specifie& an& t1is ta3en as the minim!mthroat &imension.

l1

l2 t1

D++/ /+&+$(%$& ,,+$ +,'.

With high c!rrent &ensity processes5 e.g. s!,merge& arc an& G -spray/5 penetration along the(oint line can ,e pro&!ce&. This gi*es an increase in throat thic3ness %ith no change in leg length.

l

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t1 t1

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THE DUTIES OF THE WELDING INSPECTOR

VISUAL INSPECTION

At any point in the co!rse of %el&ing5 i.e. tac3ing5 root pass5 filler pass or capping pass5 ,!tpartic!larly for the root an& cap5 a &etaile& inspection may ,e re#!ire&. 6ritish Stan&ar& 72818B= gi*es g!i&ance on tools an& responsi,ilities together %ith s3etches of typical &efects.The inspector at this point m!st +a/ O,ser*e i&entify an& perhaps recor& -meas!re/ the feat!res of the %el&.

,/ Deci&e %hether the %el& is accepta,le in terms of the partic!lar le*els that are permitte&&efect le*els may ,e $in+ho!se' or national co&es of practice.When the &efect si9e is in e)cess of the permitte& le*el then either a concession m!st ,e applie&for -from a competent person/5 or the %el& re(ecte&.

AIDS OF VISUAL INSPECTION

ll!mination Goo& lighting is essential.nspection Fenses The magnification sho!l& not e)cee& 2 + 2.7 &iameters. f highermagnification is re#!ire& !se a ,inoc!lar microscope.Optical *ie%ing can progressi*ely &e*elop from eyesight5 to !se of a han& torch an& mirror5 tothe a&&ition of a magnifier an& light so!rce.n or&er to achie*e accessi,ility5 remote pro,e !nits are a*aila,le %hich m!st ha*e the follo%ing

properties.a/ Farge fiel& of *ision

,/ "ree&om from &istortion of imagec/ Acc!rate preser*ation of colo!r *al!es

&/ A&e#!acy of ill!mination

CODE OF PRACTICE

A co&e of practice for an inspection &epartment sho!l& ta3e the form o!tline& ,elo%. t isappreciate& that f!ll implementation of the co&e %o!l& ,e e)tremely costly an& therefore it may

,e necessary to re&!ce the amo!nt of inspection to less than is theoretically re#!ire&.The inspector sho!l& ,e familiar %ith the follo%inga/ All applica,le &oc!ments

,/ Wor3manship stan&ar&sc/ All phases of goo& %or3shop practice

&/ Tools an& meas!ring &e*ices

INSPECTION BEFORE WELDING

6efore Assem,lyChec3 All applica,le &oc!ments.

H!ality plan is a!thorise& an& en&orse& %ith signat!re5 &ate an& company stamp. Application stan&ar& is !p to &ate %ith the latest e&ition5 re*ision or amen&ment. The &ra%ings are clear5 the iss!e n!m,er is mar3e& an& the latest re*ision is !se&. Wel&ing proce&!re sheets -specifications/ are a*aila,le5 ha*e ,een appro*e& an& are

employe& in pro&!ction.

Wel&er #!alifications %ith i&entification an& range of appro*al are *erifie& an& that only

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appro*e& %el&ers as re#!ire& are employe& in pro&!ction. Cali,ration certificates5 material certificates -mill sheets/ an& cons!mer certificates are

a*aila,le an& *ali&. Parent material i&entification is *erifie& against &oc!mentation an& mar3ings. aterial composition5 type an& con&ition. Correct metho&s are applie& for c!tting an& machining. &entification of %el&ing cons!ma,les s!ch as electro&es5 filler %ire5 fl!)es5 shiel&ing

an& ,ac3ing gases an& any special re#!irements -e.g. &rying/ are met. Plant an& e#!ipment are in a safe con&ition an& a&e#!ate for the (o,. Safety permits e.g. hot %or3 permit5 gas free permit5 enclose& space certificate are

a*aila,le an& *ali&.

After Assem,lyChec3 Dimensions5 tolerances5 preparation5 fit+!p an& alignment are in accor&ance %ith the

Appro*e& &ra%ings an& stan&ar&s. Tac3 %el&s5 ,ri&ging pieces5 clamping an& type of ,ac3ing + if any !se& are correct. Cleanliness of %or3 area is maintaine&. Preheat in accor&ance %ith proce&!re.

NOTE Goo& inspection prior to %el&ing can eliminate con&itions that lea& to the formation of&efects.

INSPECTION DURING WELDING

C+5: The %el&ing process m!st ,e monitore&. Preheat an& interpass temperat!res m!st ,e monitore&. nterpass cleaning + chipping5 grin&ing5 go!ging5 m!st ,e monitore&. Ioot an& s!,se#!ent r!n se#!ence. Essential *aria,les s!ch as c!rrent5 *oltage5 tra*el spee& to ,e monitore&.

"iller metals5 fl!)es an& shiel&ing gases are correct. Wel&ing is in compliance %ith %el& proce&!re sheet an& application stan&ar&.

INSPECTION AFTER WELDING

C+5: Jis!al inspection to ,e carrie& o!t to ascertain accepta,ility of appearance of %el&s. Dimensional acc!racy to ,e ascertaine&. Conformity %ith &ra%ings an& stan&ar&s re#!irements. Post %el& heat treatment5 if any5 monitore& an& recor&e&. NDT carrie& o!t an& reports assesse&. Assess &efects as to either repairing5 or application for concession.

Carry o!t any necessary repairs. Control of &istortion

REPAIRS

Iepair proce&!re an& %el&ing co&e sho!l& ,e a!thorise&. Defect area sho!l& ,e mar3e& positi*ely an& clearly. Chec3 %hen partially remo*e& an& f!lly remo*e& -*is!al an& NDT/. Ie+%el&ing sho!l& ,e monitore&. Ie+inspect complete& repair.

Collect all &oc!ments an& reports. Pass the &oc!ment pac3age on to a higher a!thority for finalinspection5 appro*al an& storage.

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THE WELDING INSPECTOR

RESPONSIBILITIESEns!re compliance %ith stan&ar& or co&e.Ens!re %or3manship.

Ens!re %el&ing criteria ,y $policing' %or3 an& &oc!mentation.

ATTRIBUTES:onesty an& integrity.Fiteracy."itness + physical an& eyesight.

DUTIESO,ser*e.eas!re.&entify.

CODES AND STANDARDS

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CLASS OF WOR;

There are many types of %or3 %hich re#!ire engineering materials to ,e (oine& ,y %el&ing5 fore)ample

Press!re *essels 6ri&gesOil rigs Earth mo*ing e#!ipment

Aero+engines Jentilation systemsStorage tan3s :ea*y *ehicle chassisCar ,o&ies "oo& processing plant

The #!ality re#!irements of the (oints in these fa,rications &epen& on their fitness+for+p!rposean& &iffer significantly from one application to the ne)t. Press!re *essels re#!ire %el&s5 %hich can%ithstan& the stresses an& high temperat!res e)perience& in operation. Oilrigs are &esigne& to%ithstan& the effect of %a*e formation an& %in& loa&s. Earth mo*ing e#!ipment has toaccommo&ate &ifferences in terrain an& earth con&itions an& is s!,(ect to fatig!e loa&ing. Wel&sin foo& processing plants m!st %ithstan& corrosion ,y hot aci&ic li#!ors.

6elo% are liste& some typical co&es of practice an& stan&ar&s %hich co*er *ario!s typesof constr!ctions fa,ricate& ,y %el&ing.

C'+ C,%## W(: 6S 77@@ Unfire& f!sion %el&e& press!re *esselsASE J American ,oiler an& press!re *essel co&e6S 2=00 Class 1 arc %el&ing of ferritic steel pipe %or3 for carrying fl!i&s6S 717 Process of %el&ing steel pipelines on lan& an& offshore6S 787@ Str!ct!ral !se of steel%or3 in ,!il&ingAWS D1.1 Str!ct!ral %el&ing co&e -American/6S 7@@ Steel5 concrete an& composite ,ri&ges6S =207 Co&e of practice for fi)e& offshore str!ct!reAP 11@ Stan&ar& for %el&ing pipelines an& relate& str!ct!res

These &oc!ments can also pro*i&e a !sef!l so!rce of &ata for applications %here co&es &o note)ist. t sho!l& ,e remem,ere&5 ho%e*er5 that the principal criterion in the co&es liste& is the#!ality of the (oint in relation to the ser*ice con&itions. There are other applications %heres!ccess is (!&ge& ,y &ifferent criteria5 s!ch as &imensional acc!racy.Another important consi&eration is controlling the cost of %el&ing. Jariations in %el& times an!antities of cons!ma,les can rea&ily res!lt if the metho& of ma3ing a %el& is left to the %el&erto &eci&e.The contin!o!s an& satisfactory performance of %el&ments ma&e to *ario!s co&es re#!ires thatspecific g!i&elines are lai& &o%n to co*er all *aria,les. These g!i&elines are !s!ally gro!pe&!n&er the general hea&ing of a Wel& Proce&!re.

CODE OF PRACTICE

A co&e of practice is a set of r!les for man!fact!ring a specific pro&!ct. t sho!l& containDesign Ie#!irements e.g. fit+!p5 preparation an& type of (ointsaterials e.g. types5 thic3ness rangesan!fact!rer's Wor3ing Practicenspection Criteria e.g. 1@@ *is!al5 percentage other NDTAcceptance Criteria e.g. &efect si9e5 limits5 etc.Wel&ing Process e.g. type5 cons!ma,lesTypes Of Tooling e.g. !se of strong,ac3s

Contract!al nformation

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The &ifference ,et%een a co&e an& a stan&ar& is that a co&e states ho% to &o a specific (o, an&&oes not contain all rele*ant information5 ,!t refers to other stan&ar&s for &etails.A co&e or stan&ar& generally mentions three parties + the c!stomer or client5 the man!fact!rer or

pro&!cer an& the inspection a!thority. n a co&e the term $shall' means man&atory + m!st ,e &one5an& the term $sho!l&' means recommen&e& + not comp!lsory.A concession is an agreement ,et%een the contracting parties to &e*iate from the original co&e

re#!irements. -6S 7107/

THE WELDING PROCEDURE

A %el&ing proce&!re is a %ay of controlling the %el&ing operation.

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P*(/#+ /(5+'*(+1/ To pro*e a (oint can meet &esign proce&!re + consistency2/ nstr!ction for %el&er0/ Ens!re repeatability

Wel& proce&!res are appro*e& to ens!re they are f!nctional an& f!lfil the physical an& mechanicalproperties necessary to reach the re#!ire& stan&ar& -to esta,lish the essential *aria,les forcontract!al o,ligations/.Wel&ers are appro*e& to ens!re a partic!lar %el&er is capa,le of %el&ing to a proce&!re an&o,taining a res!lt that meets specification.The tas3 of collecting the &ata an& &rafting the &oc!mentation is often referre& to as $%riting' a%el& proce&!re. n many %ays this is an !nfort!nate term as the %riting of &oc!ments is the lastin a se#!ence of tas3s.

P('*5&. % +,' /(5+'*(+ &,+#

Planning the tas3sCollecting the &ataWriting a proce&!re for !se or for triala3ing test %el&sE*al!ating the res!lts of the testsAppro*ing the proce&!re of the rele*ant co&ePreparing the &oc!mentation

n each co&e reference is ma&e to ho% the proce&!res are to ,e &e*ise& an& %hether appro*al ofthese proce&!res is re#!ire&. n most co&es appro*al is man&atory an& tests to confirm the s3illof the %el&er are specifie&. Details are also gi*en of acceptance criteria for the finishe& (oint.

The approach !se& &epen&s on the co&e5 for e)ample6S 2=00 -Class 1 arc %el&ing of ferritic steel pipe %or3 for carrying fl!i&s/ pro*i&es generalcomments on *ario!s aspects of a s!ita,le %el& proce&!re.AWS D.1.1 -Str!ct!ral %el&ing co&e + steel/ fa*o!rs more specific instr!ctions for &ifferent (ointsan& processes that are5 in effect5 pre+#!alifie& proce&!res.Other co&es &o not &eal specifically %ith the &etails of the %el& proce&!re ,!t refer to p!,lishe&&oc!mentation5 e.g. 6S 7107 $process of arc %el&ing car,on an& car,on manganese steels'.

COMPONENTS OF A WELD PROCEDURE

tems to ,e incl!&e& in the proce&!re can ,e some of the follo%ingParent etala. Type

,. Thic3ness -for pipe this incl!&es o!tsi&e &iameter/c. S!rface con&ition&. &entifying mar3s

W+,'&. P(5+##a. Type of process -A5 TG5 SAW etc./

,. E#!ipmentc. a3e5 ,ran&5 type of %el&ing cons!ma,les

&. When appropriate5 the temperat!re an& time a&opte& for &rying an& ,a3ing ofelectro&es

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an& < or cons!ma,les&$ D+#.&

a. Wel&ing position,. E&ge preparationc. etho& of cleaning5 &egreasing etc.&. "it !p of (oint

e. Kigging or tac3ing proce&!ref. Type of ,ac3ing

Wel&ing Positiona. Whether shop or site %el&

,. Arrangement of r!ns an& %el& se#!encec. "iller material5 composition an& si9e -&iameter/&. Wel&ing *aria,les + *oltage5 c!rrent5 tra*el spee&e. Wel& si9ef. 6ac3 go!gingg. Any specific feat!res5 e.g. heat inp!t control5 r!n+o!t length

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WPS %el&ing proce&!re specification + an appro*e& an& accepte& %el&ing proce&!re5An a!thorise& &oc!ment.

PHI proce&!re #!alification recor&s + proof the proce&!re %or3s + recor& of tests!n&erta3en to #!alify proce&!re.

WAC %el&er appro*al certificate + re#!ire& to ens!re a partic!lar %el&er is capa,le of%el&ing to a proce&!re.

WATC %el&er appro*al test certificate.WAI %el&er appro*al recor&.WPAI %el&ing proce&!re appro*al recor&.WHT %el&er #!alification test.

pWPS preliminary WPS + !na!thorise& -contains all essential *aria,les an&5 after %el&ingthe test piece an& all NDT an& &estr!cti*e tests ha*e ,een accepte&5 then the WPScan ,e appro*e&/.

pWPS an& WPAI gi*e final WPS -*ario!s WPS can &eri*e from one pWPS/.

DOCUMENTATION

The o,(ecti*es of a proce&!re or %el&er appro*al test area. to pro*e the proce&!re meets the necessary re#!irements %ith reference to feasi,ility5mechanical strength etc.

,. to pro*e the %el&ers are competent to %or3 on a partic!lar (o,.f a c!stomer #!eries it5 e*i&ence can an& %o!l& ,e s!pplie& to pro*e *ali&ity.

Appro*al Test Specifications call for a paper recor&5 %hich can ,e 3no%n asProce&!re < %el&er appro*al certificateProce&!re < %el&er appro*al recor&Proce&!re < %el&er appro*al report

The follo%ing recor&s sho!l& also ,e 3eptNDT reportsIecor&s of *is!al e)amination or mechanical testingTest pieces from &estr!cti*e testing

Other recor&s that are e#!ally important areproofof reg!lar employment on a (o, for sche&!lingre+tests to a*oi& &!plication on proce&!re appro*al.

WELDER APPROVALWel&er appro*al tests are !se& to &etermine the a,ility of a %el&er to pro&!ce %el&s of anaccepta,le #!ality %ith the processes5 materials an& %el&ing positions that are to ,e !se& in

pro&!ction. Depen&ant on the re#!irements an& a&ministration the man!fact!rer or contractor

may choose to #!alify their o%n %el&ers or they may employ o!tsi&e personnel %ho can meet there#!irements. These re#!irements !s!ally specify *erification of the tests ,y an a!thorise&inspector or in&epen&ent ,o&y. The re#!irements for the #!alification of %el&ers are !s!ally lai&&o%n in the go*erning co&e or specification or the contract specification.Appro*al tests impro*e the pro,a,ility of o,taining satisfactory %el&s in pro&!ction. :o%e*er itis tr!e to say that appro*al test %el&s are ma&e %ith special attention an& effort an& so cannotsho% %hether or not the %el&er can &o so !n&er e*ery pro&!ction con&ition. "or these reasonscomplete reliance sho!l& not ,e place& on these #!alifications + pro&!ction %el&s sho!l& ,einspecte& reg!larly to ens!re that the stan&ar& is ,eing 3ept !p.

T=/+# O A//(%, T+#$#.

Tests that are prescri,e& ,y most co&es an& stan&ar&s are in the main similar. Common tests area. Plate an& str!ct!ral mem,ers.

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,. Pipe %el&ing.c. Positions of %el&ing.&. Testing of appro*al testpieces.e. Ie+tests.a. Plate an& str!ct!ral mem,ers.The re#!irements for %el&ers of plate an& str!ct!ral parts -incl!&ing press!re *essels/ !s!ally

re#!ire the %el&er to ma3e one or more test %el&s on plate or pipe assem,lies %ith the #!alifie&%el&ing proce&!re. Each %el& is teste& in a specific manner5 often ,oth &estr!cti*ely an& non+&estr!cti*ely. The re#!irements normally state the applica,ility of material thic3ness an& %el&ing

positions that %ill #!alify for pro&!ction %or3. Other &etails %ill co*er (oint type an& &irection of%el&ing %hen &epositing *ertical %el&s -*ertically !p or *ertically &o%n/.

> P/+ +,'&.>The re#!irements for the appro*al of %el&ers for pipe %el&ing &iffers from those for %el&ing

plate an& str!ct!ral mem,ers chiefly in the type of test assem,lies an& test positions. As a r!le the%el&s m!st ,e ma&e on pipe an& not plate. n some cases the space %ithin %hich the test piecem!st ,e %el&e& may ,e restricte& if the pro&!ction %or3 in*ol*es %el&ing in crampe& con&itions.

As a general r!le %el&ers %ho #!alify for certain (oints on pipe nee& not #!alify for plate %or35,!t #!alifications on plate &o not apply to pipe%or3.

5> P#$& +,'&.>Appro*al tests are normally e)pecte& to ,e ma&e in the most &iffic!lt positions that %ill ,eenco!ntere& in pro&!ction %el&ing. "or e)ample #!alification in the *ertical5 hori9ontal an&o*erhea& positions !s!ally #!alifies for %el&ing in the flat position.

'> T+#$&. +,'+( %//(%, $+#$/+5+#>All co&es an& specifications %ill ha*e &efinite r!les for the testing of appro*al %el&s to &eterminecompliance. ost fre#!ently this in*ol*es the remo*al of specimens for mechanical tests5 s!ch as

,en& tests5 an& specimens for macro e)amination from specific locations in the test pieces. Non+&estr!cti*e testing may ,e re#!ire& in con(!nction %ith the mechanical tests.Other properties re#!ire& of the proce&!re #!alification %el&s s!ch as tensile strength5 har&ness5etc. are not generally specifie& in %el&er appro*al tests since these properties &epen& primarily onthe parent an& filler materials !se& on proce&!re &etails that are ,eyon& the in&i*i&!al %el&erLscontrol.Wel&ers %hose test %el&s meet the re#!irements are #!alifie& to !se the process an& to %el& %iththe filler metals an& proce&!res similar to those !se& in testing. t sho!l& ,e mentione& that a%el&er %ho has s!ccessf!lly %el&e& a proce&!re test specimen is not re#!ire& to !n&ergo anappro*al test5 !nless the re#!irements of pro&!ction %el&ing are &ifferent from those of the

proce&!re in %hich he has #!alifie&.

+> R+-$+#$#>The circ!mstances for the re+testing of a %el&er incl!&e the follo%ing1. "ail!re of the initial test %el&s.2. A significant change in %el&ing proce&!re.0. A %el&er has not ,een engage& in %el&ing for an e)ten&e& perio&. -Us!ally three months./. There is reason to #!estion the %el&erLs a,ility.7. Change of employment %itho!t the transfer of his appro*al certificates.

CHEC; LIST FOR WELDER AND PROCEDURE APPROVAL

1. The test ,eing carrie& o!t is the correct one re#!ire&.

1B

1B

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2. Wel&ers are in possession of all rele*ant information concerning the test.0. Test materials confirm in all respects to re#!irements.. Koint config!ration an& tolerances are correct.7. Wel&ing plant an& cons!ma,les.=. The %el&erLs i&entification is clearly mar3e& on the testpiece.B. Where it is specifie& for a root r!n to ,e stoppe& an& restarte& in a certain position5 that

thisposition is clearly mar3e&.

. n the case of (oints %el&e& in fi)e& positions the test piece is so fi)e& that it cannot ,emo*e&.

8. All ancillary tools s!ch as chipping hammers5 %ire ,r!shes5 grin&ers5 etc. are a*aila,le.The tests sho!l& ,e carrie& o!t %itho!t interr!ption ,!t %ith s!fficient s!per*ision to ens!re thatthe re#!irements are ,eing complie& %ith. Where %el&er appro*al is carrie& o!t in accor&ance%ith ASE section M it states that the person s!per*ising the test may5 if in his opinion heconsi&ers that the %el&er %ill not meet the re#!ire& stan&ar&5 terminate the test at any time. f itis necessary to apply this r!ling5 it is s!ggeste& that f!ll reasons for termination ,e recor&e&. t isf!rther recommen&e& that the testpiece sho!l& also ,e 3ept for a short perio& as a means of

,ac3ing !p %ritten statement.f the test is to ,e s!per*ise& ,y a representati*e of an in&epen&ent a!thority he sho!l& ,e gi*enall the rele*ant &etails of the testing re#!ire&.Where 6ritish stan&ar&s are in*ol*e&5 they generally state that if the %el&er is of the opinion thathis first attempt may not pass any s!,se#!ent testing5 he may %ithhol& it an& %el& a secon&. nthis case it is the secon& testpiece that is s!,mitte& for e)amination an& the first one m!st ,escrappe&.TEST CERTIFICATESho!l& state clearly that it is a %el&er appro*al an& not a proce&!re appro*al5 an&5 &epen&ing onthe partic!lar stan&ar&5 sho!l& contain the follo%ing

a. %el&er's name an& i&entity n!m,er

,. &ate of testc. stan&ar& of co&e in f!ll5 e.g. 6ritish Stan&ar& B2 PT 1 182&. test piece &etails incl!&ing material specificatione. e#!ipment an& cons!ma,le &etailsf. e)tent of appro*alg. s3etch of r!n se#!ence5 preparation an& &imensionsh. other factors5 operating parameters etc.i. the test res!lts -*is!al5 NDT5 DT etc./

(. remar3s3. %itnesse& ,yl. test s!per*isor

m. locationost stan&ar&s gi*e an e)ample of a test certificate.Signat!res on certificates m!st ,e en&orse& ,y company stamp.

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DESTRUCTIVE TESTING

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Destr!cti*e tests on %el&e& (oints are !s!ally ma&e as part of the appro*al of a %el&ingproce&!re or a %el&er.Commonly !se& &estr!cti*e tests are

6en&TensileCharpy

"ract!re testsacro section

The test pieces are c!t from the test %el& an& their location is often specifie& in the stan&ar&. The6ritish stan&ar& for the testing of %el&s is 6S B@8 180 etho&s of testing f!sion %el&e& (ointsan& %el& metal in steel. The areas for test are sho%n ,elo%.

test %el& along centre of plate

&iscar&

,en&macro section tensile

,en& longitudinal

,en&tensile

short transverse ,en&&iscar&

transverse

BEND TESTS

O?+5$) To &etermine the so!n&ness of %el& metal5 heat affecte& 9one an& %el& 9one.These tests may also ,e !se& to gi*e some meas!re of the &!ctility of the %el&9one. t is not !s!al to !se trans*erse an& longit!&inal ,en& tests for the sameapplication.

M+$' All specimens to ,e remo*e& an& prepare& %itho!t ca!sing significant &istortionor heating. The cap an& root are gro!n& fl!sh. The specimen is ,ent ,y themo*ement of a former of prescri,e& &iameter5 the rele*ant si&e of the specimen to

,e place& in tension. Angle of ,en& an& &iameter of former sho!l& ,e as specifie&

in the appropriate stan&ar&.

R+/($&. R+#*,$#1. Thic3ness of specimen2. Direction of ,en& -root or face/0. Angle of ,en&. Diameter of former 7. Appearance of (oint after ,en&ing e.g. type an& location of fla%s

root ,en& face ,en&

2@

2@

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force force

this si&e in tension for face ,en&" "

this si&e in tension for root ,en& I I I I

S!rface in contact %ith former gro!n& flat. . I > roller s!pport " > former of specifie& ra&i!s

SIDE BEND TEST

O?+5$) To &etermine the so!n&ness of the %el& metal an& :A; in a cross section. Thismay ,e preferre& to the trans*erse ,en& test on thic3 materials. t is also !se& on

processes or proce&!res e)pecting lac3 of f!sion -e.g. thic3 plate !sing G/.

M+$' The testing metho& is the same as that !se& for trans*erse ,en&s e)cept the cap

an& root are not gro!n& fl!sh5 to allo% testing across the complete %el&.

R+/($ R+#*,$#1. Wi&th an& thic3ness of specimen.2. Angle of ,en&.0. Diameter of former.. Appearance of (oint after ,en&ing e.g. type an& location of fla%s.

force 1@mm

"

thic3nessof plate I I

this si&e in tension for I > roller s!pportsi&e ,en& " > former of specifie& ra&i!s

TRANSVERSE TENSILE TEST

O?+5$ Use& to meas!re the trans*erse tensile strength !n&er static loa&ing of a ,!tt (ointemploying ,!tt %el&s.The re&!ce& section tensile test normally fails in the parent metal an& so it is not&esigne& to gi*e the tensile strength of the %el&.The ra&i!s re&!ce& tensile test is a test of the as &eposite& &il!te& %el& metal.The all %el& tensile test5 !sing a longit!&inal section from the %el& only5 is !se& tochec3 the as &eposite& !n&il!te& %el& metal. -Us!ally !se& ,y cons!ma,leman!fact!rers./

M+$' The testpiece is clampe& at each en& an& a loa& is applie& ,y an hy&ra!lic or scre%mechanism. The loa& is increase& !ntil fract!re occ!rs.

R+/($&. R+#*,$#1. Type of specimen -e.g. re&!ce& section/.2. Whether e)cess %el& metal is remo*e& or not.

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0. Tensile strength5 in Ne%tons per mm s#!are&5 is calc!late& from ma)im!m loa&an& original cross sectional area. When e)cess %el& metal is not remo*e&5 thecross sectional area shall ,e the pro&!ct of the parent metal thic3ness an& the%i&th of the specimen.

. Focation of fract!re + %hether in parent plate5 heat affecte& 9one or %el& metal. fthe fract!re is in the parent metal5 the &istance from the %el& 9one shall ,e state&.

7. Focation an& type of any fla%s present on the fract!re s!rface.

loa& loa&

notch in %el&

loa& loa&

re&!ce& section tensile test ra&i!s re&!ce& tensile test

The test gi*es a meas!re of percentage elongation5 percentage re&!ction in area an& !ltimatetensilestrength.

UTS -yiel& stress strength point/

yiel& point

UTS > !ltimate tensilestrength STIAN -N/

elastic plastic

STIESS -mm/

The tensile test gi*es a meas!re of DUCTFT.-in Ne%tons per mm s#!are&5 a com,ination of percentage elongation an& percentage re&!ctionin area.

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T=/+# %,*(+#.

BRITTLE 6rea3

S!rface

6rittle fract!re is flat an& feat!reless.

DUCTILE

6rea3 Shear lips

S!rface

A &!ctile fract!re tears at 7to the loa&.

LChe*ronL mar3s.N+SEIJCE 6ITTFE "IACTUIE

S!rfaceA flat s!rface %ith che*ron mar3ings that point to the material &efect that initiate& the fract!re.

C!r*esFATIGUE FAILURE

S!rface

A flat s!rface %ith noticea,le c!r*es.

CHARPY V NOTCH IMPACT TEST

O?+5$) To &etermine the amo!nt of energy a,sor,e& in fract!ring a stan&ar&ise& testpieceat a specifie& temperat!re.

M+$') A machine&5 notche& specimen is ,ro3en ,y one ,lo% from a pen&!l!m. 6eca!sescatter occ!rs in the res!lts5 at least three specimens are !se& to assess the (ointrepresente&.Testing is carrie& o!t at a temperat!re specifie& in the appropriate applicationstan&ar&.The 6ritish stan&ar& is 6S 101 PT 2 18B2.

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R+/($&. R+#*,$#)1. Focation an& orientation of the notch.2. Testing temperat!re.0. Energy a,sor,e& in (o!les.. Description of fract!re appearance.7. Focation of any &efects.

:ammer ,lo% from this si&e h

&

1@mm p A

6 77mm

1@mm

a t

root ra&i!s a + an*il

@.27 mm t 4 test pieceh + hammer& + &ial cali,rate& in (o!les

p + point reache& afterfract!re

2 mm Energy a,sor,e& &!ringfract!re

7 is proportional to -A + 6/

C:AIP TEST PECE C:AIP PACT AC:NE

The Charpy impact test5 meas!re& in (o!les5 is an assessment of TOUG:NESS.

Transition temperat!re -c!r*e/ in steel. D!ctile "ail!re

CS SS

Ko!les

2

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Temperat!re6rittle "ail!re -higher to!ghness /

FILLET WELD FRACTURE TEST

O,(ect To ,rea3 the (oint thro!gh the %el& to permit e)amination of the fract!re s!rfacesfor fla%s an& to chec3 root penetration an& f!sion.

etho& The specimen is c!t to length an& a sa% c!t5 normally 2 mm &eep5 is ma&e alongthe centre of the %el& face. The specimen is fract!re& ,y ,en&ing or hammer

,lo%s.

R+/($&. R+#*,$#)

1. Thic3ness of parent material.2. Throat thic3ness an& leg length.0. Focation of fract!re.. Appearance of (oint after fract!re.7. Depth of penetration < lac3 of penetration or f!sion.

hammer or ,en& sa% c!t

$NIC;@ BREA; BEND TEST

O,(ect As for fillet %el& fract!re5 !se& on ,!tt %el&s.

etho& The specimen is c!t trans*ersely to the %el&5 an& a sa% c!t is applie& along thecentre of the %el& face. The ,est place for the c!t is at a start < stop. The specimenis fract!re& ,y ,en&ing or ,y hammer ,lo%s. The nic3 ,en& test %ill fin& internal&efects.

R+/($&. R+#*,$#)1. Thic3ness of material.2. Wi&th of specimen.0. Focation of fract!re.. Appearance of (oint after fract!re.

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MACRO SECTION

O?+5$ To e)amine a cross section of a %el& for internal &efects an& so!n&ness.

M+$') A trans*erse section of the %el& is c!t o!t. The cross section is then *is!allyinspecte&. The section is file& &o%n from ro!gh to smooth5 then emery or %et

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SYMBOLS

WELD SPECIFICATIONS

Wel&s m!st ,e specifie& ,y clear instr!ctions an& all staff incl!&ing pro&!ction personnel m!st!n&erstan& the %el& sym,ols specifie&.t may ,e necessary to specify more &etails a,o!t the %el& e.g. si9e5 or electro&e to ,e !se&5 ore*en the f!ll &etails of a %el& proce&!re may ,e nee&e&.The metho&s most commonly !se& to specify a %el& are

W($$+& #$%$+

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W+,' &(arrow sideof the (oint.

A triangle on the &otte& linecalls for a fillet %el& on the >other sideof the (oint.

TYPES OF BUTT WELD

The common types of e&ge preparation associate& %ith a ,!tt %el& are in&icate& asfollo%s

s#!are e&ge preparation single J preparation

&o!,le J preparation single U preparation

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Using sym,ols it is not necessary to &ra%the &o!,le U preparation shape of the %el& e&ge preparation.On any

&ra%ing the (oint is al%ays sho%n as a singleline.

ASYMMETRICAL PREPARATIONS

n some (oints5 only one component is prepare&5 e.g. single ,e*el ,!tt or single K ,!tt. n thesecases the arro% points at the e&ge %hich is to ,e prepare&. The *ertical !pright of the sym,ol isal%ays to the left on the reference line.

>>

DIMENSIONING FILLET WELDS

The leg length of a fillet %el& is locate& to the left of the %el& sym,ol -triangle/. The &imension isin millimetres prece&e& %ith the letter ;. Throat thic3ness is in&icate& in the same %ay ,!t is

prece&e& ,y the letter a. f no letter is sho%n on a &ra%ing5 then ass!me the &imension is leglength.

; 1@ a B > 1@ mm leg length > fillet %el& %ith B mm

fillet %el& &esign throatthic3ness

"or &eep penetration %el&s the &imensions are in&icate& e.g. S a=

This in&icates a %el& of = mm &esign throat5 %ith an mmact!al throat &esire&. The act!al throat thic3ness isprece&e& ,y S.

ntermittent fillet %el&s are &imensione& ,y gi*ing ; n ) l -e/n!m,er of %el& elements - n /length of %el& element - l /&istance ,et%een %el& elements - e /

Often the n!m,er of %el& elements -n/ is not specifie&5 !s!ally ,eca!se it is not 3no%n.The sym,ol can also ,e %ritten as l -e/ l5 the length ,eing repeate&. The length is in centimetres.

A sym,ol th!s 9 n ) l -e/ on a &o!,le fillet means the %el& elements are to ,estaggere& on either si&e of the (oint.

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staggere&

; = 1@-2@/ 1@ = mm throat fillet %el&s of 1@ cm length %ith a gapof

> 2@ cm ,et%een each element5 staggere& on eithersi&e of the (oint5 for the %hole (oint's length.

COMPOUND WELDSA compo!n& %el& is a com,ination of &ifferent %el&s on the same (oint.

> A f!ll penetration single ,e*el tee(oint %ith an mm fillet

reinforcement.

= > An mm partial penetration tee (oint%ith an mm fillet reinforcement

an&a = mm fillet on the other si&e of the

(oint.

> A single J ,!tt %el& %ith a sealingr!n along the root si&e of the%el&.

SURFACE PROFILES

The s!rface profile can ,e in&icate& ,y an e)tra sym,ol place& on top of the %el& sym,ol.

0@

0@

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> > a single J ,!tt %el& %ith aflat

s!rface. -!s!ally fl!she&after %el&ing ,y grin&ing/

> a conca*e fillet %el&.

> a con*e) fillet %el&.

> a fillet %el& %ith ,len&e& toes.

SUPPLEMENTARY SYMBOLS

Other sym,ols in general !se

> %el& all ro!n& the component.

> a&&itional information. -the ,o) on the tailof the reference line can contain informatione.g.

%el& process5 NDT5 paint5 etc./

> this %el& %el&e& on site. -fiel& %el&/

> spot %el& > seam %el&

> pl!g %el& > seal %el&

> ,!tt %el& ,et%een plates %ith raise& e&ges

BS 499

01

01

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n the ol&er style5 in 6S 88 stan&ar&5 the main &ifference %as that there %as no &otte& referenceline5 so ,elo% the reference line %as the arro% si&e an& a,o*e the reference line %as the othersi&e.

other si&earro% si&e

MATERIALS

ALLOYING ADDITIVES

The term $steel' is !se& to &escri,e many &ifferent metals. They are all alloys ,ase& on iron5 ,!tthe alloying a&&itions5 s!ch as car,on5 manganese5 silicon5 chromi!m5 etc.5 singly or incom,ination pro&!ce a range of metals %ith %i&ely &iffering physical an& mechanical propertiesas %ell as #!ite &ifferent %el&i,ility.

ION "e the ,asic constit!ent.CAI6ON C gi*es har&ness an& strength.ANGANESE n gi*es to!ghness an& strength. Ne!tralises s!lph!r.SFCON Si a &eo)i&ent + o)i&e re&!cer. Us!ally a&&e& thro!gh filler %ire.AFUNU Al an o)i&e re&!cer5 grain refiner an& a&&s to!ghness. -n 3ille& steelthe

o)ygen is remo*e& ,y al!mini!m./C:IOU Cr gi*es corrosion resistance5 high temperat!re strength an& creep

resistance. -Grain creep occ!rs o*er time at high temperat!res &!eto gra*ity./

OF6DENU o gi*es high temperat!re creep resistance.

TTANU Ti Ti an& N, are ,oth grain refiners an& sta,ilising agents. Theypre*entNO6U N, intergran!lar corrosion an& %el& &ecay. Use& in a!stenitic steels.JANADU J gi*es har&ness an& strength.SUFP:UI S a contaminant. -ain ca!se of soli&ification crac3ing + $hot

shortnessL/NCEF Ni gi*es lo% temperat!re to!ghness an& strength.COPPEI C! a contaminant + ca!ses lo#!ation crac3s. -Tho!gh also !se& for

%eathering steel an& a possi,le grain refiner./P:OSP:OIUS P a contaminant.

STEEL COMPOSITIONS

02

02

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Iimming SteelComposition @.@8 C @.8 n ? resi&!alsWel&a,ility The %el& pool %ill re#!ire to ha*e a&&e& &eo)i&ent *ia a filler ro&.

Iimming steel is *ery &!ctile5 cheap an& !se& for pressing an& forming. tis lo% in car,on an& high in o)ygen + has not ,een 3ille& -3ille& >&eo)i&ise&/.

Fo% Car,on SteelComposition @.2 C @.8 n ? resi&!alsWel&a,ility The general %el&a,ility is goo& ,!t the le*el of resi&!als -S/ may ca!se%el& metal < heat affecte& 9one crac3ing.

e&i!m Car,on SteelComposition @.7 C @.8 n ? resi&!alsWel&a,ility The high car,on content in&!ces hy&rogen crac3ing in the :A; as the

section si9e increases. Greater than @.0 C possi,ly re#!ires heattreatment.

:igh Car,on SteelComposition @. C @.8 n ? resi&!alsWel&a,ility The %el& pool is s!,(ect to soli&ification type crac3ing an& the :A;s!ffers

hy&rogen crac3ing. Not s!ita,le for %el&ing. A tool steel.

Car,on+anganese SteelComposition @.2 C 1.7 n ? resi&!als may also contain Ti5 Ni an& J.

Wel&a,ility These high manganese steels ha*e goo& to!ghness5 partic!larly thetitani!m5 nio,i!m5 an& *ana&i!m gra&es. The main %el&a,ility pro,lem isto maintain these.

H!enche& An& Tempere& SteelComposition @. C 1.@ n @. Cr @.0 o ? Ti or Al ?resi&!alsWel&a,ility These steels are &iffic!lt to %el&5 an& &efect free %el&s %ith goo&mechanical

properties are only o,taine& ,y !sing the greatest care.

:igh Temperat!re SteelComposition @.27 + 8 Cr @.27 + 0 o ? tracesWel&a,ility The %el&a,ility of the lo% chromi!m is &iffic!lt. Goo& grain creepresistance.

Fo% Temperat!re SteelComposition 0.7 + 8 Ni ? tracesWel&a,ility The higher nic3el content is s!,(ect to soli&ification crac3ing.

icro Alloye& Steel -:SFA/Composition @.27 C 1.7 n -@.@@2 J5 @.@@7 N,5 @.@@0 Ti minim!m/

Wel&a,ility These steels may s!ffer hy&rogen crac3ing in the %el& metal + the only%el&

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metal to &o so. :SFA + :igh Strength Fo% Alloy.

STAINLESS STEELS

artensitic Stainless Steel

Composition 11 Cr @.@ C ? resi&!alsWel&a,ility Poor &!e to hy&rogen crac3ing.

"erritic Stainless SteelComposition 12 + 2B Cr @.@ C ? resi&!alsWel&a,ility Poor &!e to crac3ing5 ,rittleness an& temper em,rittlement.

A!stinitic Stainless SteelComposition 1 + 2B Cr + 22 Ni @.@ C ? resi&!alsWel&a,ility Pro,lems %ith soli&ification crac3ing an& %el& &ecay + ,!t &oes not s!ffer

hy&rogen crac3ing. N.6. this is non-magneticsteel.

CARBON EUIVALENCY

Car,on e#!i*alency -C.E./ is !se& to gi*e an o*erall car,on percentage to estimate the ris3 ofcrac3ing. The higher the car,on content the har&er the steel + the more s!scepti,le it is tocrac3ing. A car,on e#!i*alency of @.@ an& a,o*e gi*es a greater ris3 of crac3ing.

C.E. > C ? n ? Cr ? o ? J ? Ni ? Co etc.

= 7 17REVIEW OF STEELS

Types of steel !se& in %el&e& constr!ctions +

a. Fo% car,on + These steels are rea&ily %el&a,le ,!t may ,e s!,(ect to %el& metal crac3ingin

the cheaper #!alities.,. e&i!m car,on + As the car,on content approaches @. steels ,ecome prone to parent

metal crac3ing.c. Fo% car,on

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ille& steel is &eo)i&ise& an& altho!gh the res!lting non+metallic incl!sions may gi*e rise to someother pro,lems porosity is not !s!ally a prime pro,lem.

Air ,lo%n aci& or ,asic 6essemer steel %ill contain nitrogen5 %hich lo%ers the impact properties&!e to precipitation of "eN nee&les. This is ,ecoming less of a pro,lem %ith the a&*ent oftonnage o)ygen an& the ,asic o)ygen process in steelma3ing.

Deo)i&ants are *arie& ,!t al!mini!m5 silicon an& manganese are %i&ely !se&. Al!mini!m gi*esthe finer grain si9e5 an& hence a har&er steel. :o%e*er the fine grain si9e is lost %hen

temperat!res in e)cess of 07@C are enco!ntere&.

D++5$# & /%(+&$ t is not5 in general5 safe for the inspector to i&entify materials ,y composition from a millsheet5 since *ery small *ariations or a&&itions to the metal may gi*e rise to significantchanges in properties an& %el&a,ility. :o%e*er limite& selecti*ity is permissi,le5 s!ch as

percentage car,on ma)im!m etc. The proce&!re is for the mill sheet to ,e s!,mitte& forappro*al an& then the inspector recor&s an& transfers the reference n!m,er.

S*//,+(>This can ,e fo!n& on the Goo&s n%ar&s &oc!ments or the receipt &oc!ments5 oroccasionally on pac3aging or e*en mar3e& on the metal.

*%&$$=>

The #!antity ,eing inspecte& sho!l& al%ays ,e note& as %ell as the sample si9e if 1@@ inspection is not ,eing employe&.

S+>Si9es m!st ,e chec3e& for secon&ary i&entification as %ell as conformance. The inspector%ill5 as appropriate5 ,e gi*en tolerances on si9e that are permissi,le. Chec3 length5

,rea&th5 thic3ness an& &iameter.D#$($&>

A chec3 is often re#!ire& on the &egree of &istortion5 i.e."latnessS#!arenessStraightness

O*alityConsistent %all thic3ness

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C&'$&>I!st5 paint an& grease on the s!rface of the metal are all harmf!l to %el&ing an& m!st!s!ally ,e remo*e&5 at least near to the act!al %el&. G!i&ance is normally gi*en to theinspector regar&ing accepta,le le*els or the treatment that is re#!ire&. An inspectorsho!l& ,e alert to gra&!al changes5 s!ch as increase& corrosion. Caref!lly maintaine&specimens sho%ing accepta,le con&itions are often the ,est metho&. :eat treatment

con&ition5 anneale&5 normalise& etc.5 sho!l& all ,e recor&e&.D++5$#>

n %ro!ght pro&!cts the most common &efects are laps an& laminations -Also porosityan&

segregation ,an&s./ These %ill normally ,e s!,s!rface so5 !nless NDE is employe&5 onlythe e&ges of the plate5 an& partic!larly c!t e&ges5 can ,e inspecte&. The lapAfter inspection an& appro*al for !se it is essential that the metal is store& in s!ch a %ayas to maintain its goo& con&ition. Protect from corrosion an& mechanical &amage.

MATERIALS INSPECTION CHEC; LIST

INSPECTION OF

S;E TPE CONDTON

thic3ness composition physical mechanical length gra&e %i&th car,on e#!i*alent s!rface heat treatment

&iameter tra&e name scaleo*ality oil

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tolerances accepta,le accepta,le

ACCEPTANCE OF MATERIAL

UESTIONS TO BE AS;ED1. Do the mar3ings on the material match those on the proce&!re sheet or &ra%ing2. Are the &imensions correct0. s the s!rface con&ition satisfactory for %el&ing

THE FOUR ESSENTIAL FACTORS FOR ESTABLISHING A WELD

Wel&ing is !s!ally regar&e& as a (oining process in %hich the %or3 pieces are in atomic contactoften %ith a filler metal %ith ,roa&ly similar properties. :ence sol&ering an& ,ra9ing are e)cl!&e&

,!t ,oth soli& state an& f!sion %el&ing are incl!&e&.

Soli& state processes incl!&e"orge %el&ing."riction %el&ing.

"!sion %el&ing processes incl!&eO)y+acetylene.an!al metal arc -A/.etal inert

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MMA f!sion so!rce electric arc ,et%een electro&e an& %or3place.atmospheric protection gaseo!s shiel& from fl!).s!rface protection mechanical cleaning5 slag5 fl!)ing -cleaning/ action.

properties alloying elements in fl!)5 ,a3ing electro&es5 pre an&post %el& heat treatment.

WELDABILITY

INTRODUCTION

As a res!lt of the heat inp!t to %hich the steel is e)pose& in any form of %el&ing the material!n&ergoes certain changes5 some of %hich are permanent. Amongst these changes are str!ct!raltransformations &!ring heating an& cooling an& changes in shape or si9e &!e to the thermal

stresses. A steel5 %hich can ,e %el&e& %itho!t any &angero!s conse#!ences res!lting from thesechanges5 is sai& to possessgood weldability. f5 on the other han&5 the changes &!e to a normal%el&ing process are in serio!s &anger of ca!sing fail!re in a %el&e& component5 or if act!al&efects s!ch as crac3ing occ!r &!ring %el&ing5 the steel is sai& to possess limited weldabilityan&can in most cases ,e %el&e&5 %itho!t ris35 pro*i&e& certain preca!tions are ta3en or certain pre+or post+ %el&ing treatments are carrie& o!t. The term $!n%el&a,le steels' is !nrealistic. Any steelcan ,e %el&e& pro*i&e& correct metall!rgical con&itions are chosen. Sometimes5 ho%e*er5 thesecon&itions may ,e impossi,le to realise in practical pro&!ction %or3.

WEFDA6FT O" STEEF

Wel&a,ility is a f!nction of many inter+relate& factors ,!t these may ,e s!mmarise& as1. Process an& techni#!e.2. Composition of parent plate.0. Koint &esign an& si9e.

INFLUENCE OF PROCESSEach process %ill gi*e a characteristic intensity of po%er. Processes that offer the higher po%erintensity offer a&*antages in f!sion %el&ing ,eca!se the essential melting can ,e o,taine& %itho!te)cessi*e heat inp!ts %ith the conse#!ent thermal e)pansion of the parent metal.S!ccessf!l %el&ing often &epen&s on fee&ing into the %el& pool a filler %ire %hich carries a

&eo)i&ant -or ferrite forming elements/ hence processes %hich &o not !se filler %ire are limite& inapplication.

HEAT INPUT

:eat inp!t is a com,ination of *oltage5 amperage an& tra*el spee&.

:eat np!t > *oltage ) amperagetra*el spee&

:eat np!t @.7 1 2

6ea& Penetration

0

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:ar&ness B7 7@ 0@@ 2B7

-%ith har&ness5 the higher the n!m,er5 the har&er the material/

To!ghness + resistance to ,en&ing an& impact

:ar&ness + resistance to penetrationAs heat inp!t increases grain si9e increases to!ghness &ecreases

,rittleness increases har&ness &ecreasesinci&ence of crac3ing &ecreases

PREHEATING

There are fo!r general factors that m!st ,e assesse& to &etermine the le*el of preheat.1. aterial type.2. Com,ine& thic3ness.0. :eat inp!t potential -%el&ing process/.

. Koint type.

INFLUENCE OF COMPOSITION

The composition of the steel an& its effect on %el&a,ility may ,e &i*i&e& into t%o parts1.Segregation effects5 partic!larly that of s!lph!r.

When a steel soli&ifies5 there is a ten&ency for the iron to soli&ify fast an& for the alloyingelements to ,e acc!m!late& in the centre of the ingot. This config!ration is retaine& e*en after

prolonge& an& se*ere rolling an& res!lts in high concentrations of s!lph!r in the central layers ofthe plate. These layers ha*e little strength an& are li3ely to crac3 if stresse&.

2. The ten&ency of the steel to har&en.The har&ening characteristics of steel are mentione& in the heat treatment section. As the car,onor alloy content of the steel increases5 the li3elihoo& of lo% &!ctility an& har&ene&microstr!ct!res forming also increases an& sho!l& stresses e)ist5 crac3ing %ill res!lt.

WELD AND HA CRAC;ING

These are the main ca!ses of crac3inga. :igh le*els of car,on an& other alloy elements res!lt in ,rittle 9ones aro!n& the %el&.

,. :igh cooling rates after %el&ing increase the har&ness5 %hich increases the s!scepti,ilityto col& crac3ing.

c. Koint restraint pre*ents contraction after %el&ing5 %hich can lea& to internal crac3ing.&. :y&rogen in the %el& ,ea& can lea& to hy&rogen in&!ce& col& crac3ing.e. Contaminants li3e s!lph!r an& phosphor!s ca!se segregation or soli&ification crac3ing.f. Famellar tearing ca!se& ,y incl!sions layering &!ring rolling res!lting in &eterioration of

the thro!gh+thic3ness properties.

Crac3ing !s!ally occ!rs in the !nmelte& areas a&(acent to a %el& ,ea& -in the heat affecte& 9one5

:A;/. This 9one is ma&e !p of an area that has ,een heate& to a,o*e a,o!t @@C -to ,ecome

a!stenite/5 an& an area heate& a,o*e B20C -an& partially transforme&/. The f!lly a!stenitic

region (!st a&(acent to the f!sion 9one is often the most ,rittle area of the %el& &!e to the graingro%th that has occ!rre& %hile the metal %as at this temperat!re. The grain si9e gra&!ally

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&ecreases mo*ing a%ay from the f!sion 9one to the partially transforme& region. Grainrefinement occ!rs here5 %hich is consi&ere& ,eneficial5 the grain si9e ,eing smaller.The composition of the steel5 partic!larly the car,on le*el5 &etermines the har&ness an& ,rittlenessof ,oth the %el& an& the :A;. On cooling5 a!stenite transforms to ferrite. Car,on is sol!,le ina!stenite5 ,!t less so in ferrite. ron car,i&es are precipitate& %hen this transformation ta3es

place. These can ,e arrange& in lamellar form -as pearlite/5 %hich gi*es the str!ct!re reasona,le

strength an& &!ctility.The :A; can ,e the region %here the highest cooling rates occ!r5 partic!larly in thic3er section

plate. :igh cooling rates ten& to loc3 the car,i&es in a soli& sol!tion5 forming martensite. Thislea&s to high internal stress an& har& ,rittle str!ct!res.

TYPICAL WELDABILITY DEFECTS

1. SOLIDIFICATION CRAC;ING.Also 3no%n as hot crac3ing or centreline crac3ing. Al%ays occ!rs in the %el& metal.Ca!ses + n car,on manganese steels s!lph!r in the parent plate5 shape of the %el&5 stress +al%ays nee&e&.

S*,/*(.D!ring soli&ification the centre of the %el& is the last to cool. S!lph!r from the parent plateforms iron s!lphi&e %ith iron from the %el& pool. The iron s!lphi&e forms a thin li#!i& film on thegrain ,o!n&aries5 %hich has a lo%er melting point than iron5 so as the %el& cools it is p!she&to%ar&s the centre of the %el&. The iron s!lphi&e has *ery little tensile strength5 so as it cools5 the%el& is !n&er stress an& crac3ing %ill res!lt. Phosphoro!s contamination in the material can alsoca!se soli&ification crac3ing.

A'%&5++ Ie&!ce s!lph!r -chec3 mill sheets for le*els Deep an& narro% %el& preparations are s!scepti,le. As a %el& cools5 grains gro% from thee)tremities to%ar&s the centre of the %el&. n a narro% prep5 as the grains gro% to%ar&s thecentre5 they interfere %ith each other's gro%th. This grain impingement ca!ses *oi&s ,et%een thegrains an& crac3ing %ill res!lt.A*oi&ance + Wi&er %el& preparation -increase the incl!&e& angle an& < or gap si9e/.

2> HYDROGEN CRAC;ING.Also 3no%n as !n&er ,ea& crac3ing5 har& 9one crac3ing an& hy&rogen in&!ce& col& crac3ing-:CC/. This phenomenon can occ!r &!ring the %el&ing of har&ena,le steels5 an& is normally a:A; phenomenon. :y&rogen is more sol!,le in a!stenite than ferrite + it can easily ,e pic3e& !p

,y the %el& metal. When ferrite is forme& the hy&rogen sol!,ility &ecreases5 an& hy&rogen&iff!ses to the :A; %here it can contri,!te to crac3 propagation.There are fo!r factors in*ol*e& in hy&rogen crac3ing. A*oi& one factor an& hy&rogen crac3ing%ill not occ!r.

F%5$(#>1. hy&rogen Q 17 ml hy&rogen per 1@@ mg %el& metal

2. temperat!re R 07@C

@

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0. har&ness Q @@ JPN -Jic3ers pyrami& n!m,er/. stress Q 7@ yiel& -cannot ,e meas!re& so ass!me it is Q 7@ yiel&/

A*oi&ance.1> H='(.+& a/ parent material &rie& -free from moist!re/.

,/ lo% hy&rogen ro&s -,a3e& to less than 7 ml per 1@@ mg/.

c/ !se lo%er potential hy&rogen process.-hy&rogen potential + electron R TG R G T+ H%('&+## a/ preheating -to re&!ce the cooling rate/

,/ 3eep interpass temperat!re to a minim!mc/ higher heat inp!t -gi*es a larger grain si9e/&/ post %el& heat treatment +tempers har& :A;5 remo*es :25 re&!ces

stress

4> S$(+## a/ (oint &esign,/ fit !pc/ &istortion control&/ stress relie*e treatment -pre an& post %el&/

On high micro alloy steels it may occ!r in the %el& metal5 other%ise only in the :A;.

3> LAMELLAR TEARING.A step li3e crac3 that occ!rs in thic3 section tee (oints an& close& corner (oints.

stress

lamellar tearinghas $step li3e'

appearance

stress

Ca!ses + Poor thro!gh thic3ness &!ctility in parent plate %here high shrin3age strains -thro!ghthic3ness stress/ act thro!gh the plate thic3ness in com,ination %ith parent metal incl!sions. Theincl!sions can ,e lamellar incl!sions5 small micro incl!sions or tramp elements. Only occ!rs onthe leg %ith stresses on the non+rolling &irection < thro!gh thic3ness.

A*oi&ance + Koint &esign -!se pre+forme& tees5 !se open corners/.Use ,!ttering layer -possi,ly more &!ctile an& %ill ta3e !p some of the shrin3age/.

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Use ; gra&e steel -has ,een teste& in the short trans*erse &irection !sing a STIAtest + Short Trans*erse Ie&!ction in Area/.

stress

,!ttering

stress stress

pre forme& tee open corner ,!ttering4> WELD DECAY IN AUSTENITIC STAINLESS STEELS

Occ!rs in the :A; &!e to the precipitation of chromi!m car,i&es. n the 77@C + 7@C range5

the chromi!m leaches o!t of the grain an& reacts %ith the car,on to form chromi!m car,i&es5 &!eto the chromi!m ha*ing a greater affinity for car,on. This res!lts in a chromi!m &eficiency in thegrains. The chromi!m is in the grains for corrosion resistance5 so %hen the chromi!m is lost5&ecay -$r!sting'/ occ!rs *ery #!ic3ly. The longer a 9one is in the temperat!re range of

77@C to 7@C the greater the area is s!scepti,le to &ecay. This temperat!re range is !s!ally

(!st off the %el&.

A*oi&ance + Ie&!ce car,on + Use lo% car,on ro&s for e)ample 01= F. 6!t lo% car,on re&!cesstrength5 so a sta,ilise& stainless steel co!l& ,e !se& %ith high car,on content ,!t%ith titani!m an& nio,i!m a&&e&. -Car,on has a greater affinity for titani!m an&nio,i!m therefore titani!m an& nio,i!m car,i&es are pro&!ce& instea& ofchromi!m car,i&es/.

Fo%er heat inp!t + less time in the 77@C + 7@C temperat!re range.

H!ench cool + less time in the 77@C + 7@C temperat!re range.

eep interpass temperat!re lo%.

The 3ey%or& is precipitation -of the chromi!m/. The material is then sai& to ,e sensitise& + p!t itin sea%ater5 it r!sts.

WELDING OF CARBON STEEL

These steels are also 3no%n as car,on+manganese an& plain car,on steels. They are !s!ally%el&e& %ith mil& steel cons!ma,les %itho!t pro,lems5 ,!t the %el&a,ility &ecreases %ithincreasing car,on le*els or C.E. -car,on e#!i*alent/ *al!es.The *ery lo% car,on steels -C R @.17/ can pro&!ce porosity %hen %el&e& at high spee&. This

pro,lem can ,e o*ercome ,y increasing the heat inp!t.Steels %ith car,on contents ,et%een @.17 an& @.27 are preferre& for %el&ing5 as they rarelypresent %el&a,ility pro,lems if the imp!rity le*els are 3ept lo%. The steels %ith car,on le*elshigher than @.27 can ,e s!scepti,le to crac3ing if other har&ening elements li3e n an& Si are

present in fairly high percentages. These steels are ,est %el&e& %ith lo% hy&rogen processes orelectro&es5 an& thic3 sections may re#!ire some pre+heating to re&!ce the cooling rate.The high car,on steels are !se& for their %ear resistance an& har&ness -for e)ample tool steels/.They are generally *ery ,rittle an& re#!ire pre+heating5 interpass heating an& post %el& stressrelief to pre*ent crac3ing.ost me&i!m car,on steels re#!ire one or more of the a,o*e treatments &epen&ing on car,onle*el an& (oint thic3ness. They are al%ays %el&e& %ith lo% hy&rogen processes or cons!ma,lesan& it is !s!al to perform a %el&a,ility test ,efore pro&!ction %el&ing.

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WELDING OF LOW ALLOY STEELS

The most common lo% alloy steels are the nic3el steels5 the car,on+moly,&en!m an& thechromi!m+moly,&en!m alloys.

Nic3el from 2 to 7 in a @.17 to @.27 car,on steel pro*i&es a com,ination of high strengthan& high to!ghness at lo% temperat!res. f the car,on le*el is ,elo% @.1 %el&ing can ,e &one

%itho!t pre+heat. A,o*e this le*el5 similar preca!tions to those recommen&e& for me&i!m car,onsteels sho!l& ,e a&opte&.The car,on+moly,&en!m an& chromi!m+moly,&en!m steels are !se& for high temperat!reapplications as they ha*e high creep resistance an& high strength. 6elo% @.1 car,on no pre+heat is re#!ire&5 ,!t thic3er sections %ith higher car,on le*els are har&ena,le in air an& thereforecrac3 sensiti*e. "or *ery high car,on le*els -@.77/ %here %el&ing is not recommen&e&5 ana!stenitic stainless steel cons!ma,le can sometimes ,e !se&. The %el& %ill ha*e more &!ctilityan& less strength than the parent plate an& %ill relie*e some of the internal stress. The :A; %illstill ,e ,rittle5 ho%e*er5 ma3ing pre+heat essential.

WELDING OF HIGH YIELD UENCH AND TEMPERED STEELS

These steels ha*e martensitic str!ct!res that are forme& ,y heat treatment &!ring man!fact!re.One of the most common of these steels is :@5 %hich is !se& on s!,marine h!lls.The steels rely on relati*ely high cooling rates for the strong martensitic str!ct!res to form.Strength can ,e lost if the cooling rate is too slo%. Too high a cooling rate5 ho%e*er5 can ca!se%el& crac3ing. 6oth the minim!m pre+heat temperat!re an& the ma)im!m inter+pass temperat!reha*e to ,e caref!lly controlle& to achie*e the correct str!ct!re %itho!t crac3ing. atchingcons!ma,les are !s!ally !se&. Wea*ing sho!l& ,e limite& to a ma)im!m of 17mm to 3eep theheat inp!t &o%n.

WELDING OF HIGH STRENGTH LOW ALLOY STEELS

ost of these steels &o not rely on heat treatment for their strength. They ha*e ferritic str!ct!res%ith lo% car,on le*els -@.2 an& less/ an& small amo!nts of alloying elements in sol!tion -n5Cr5 Ti5 J5 N,5 N/.There are many &ifferent types %ith *arying &egrees of strength5 to!ghness an& corrosionresistance. They !s!ally ha*e goo& %el&a,ility5 ,!t the high strength &oes ma3e them mores!scepti,le to crac3ing than lo% car,on steel. :igh heat inp!ts are !s!ally recommen&e& an& pre+heating is sometimes re#!ire&.

SUMMARY

6S 7107 states that %el&a,ility is the a,ility of a material to ,e (oine& ,y most of the %el&processes an& still maintain most of the physical

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RESIDUAL STRESS

etals contract &!ring soli&ification an& s!,se#!ent cooling5 ,!t if this contraction is pre*ente&or inhi,ite&5 resi&!al stresses %ill &e*elop. D!ring normal cooling smaller grains &e*elop firstto%ar&s the e&ges of the %el& an& larger grains &e*elop in the mi&&le of the %el& as it cools.ost material pro&!cts contain resi&!al stresses5 often !p to yiel& point. Pipe pro&!cts5 for

e)ample5 are !s!ally *ery highly stresse&.The ten&ency to &e*elop resi&!al stresses increases %hen the heating an& cooling are localise&.So %el&ing %ith its *ery localise& heating an& the presence of li#!i& an& soli& metal in contactcan ,e e)pecte& to in&!ce *ery high le*els of resi&!al stresses.

Iesi&!al stresses are a com,ination of !ne#!al e)pansion < contraction co!ple& %ith restraint.

Iesi&!al stresses can ,e &iffic!lt to meas!re %ith any real acc!racy5 ,!t a ro!gh g!i&e is that%hen the %el& metal e)cee&s t%o c!,ic inches -fo!rteen c!,ic centimetres/ then the total resi&!alstress is a,o!t yiel& point in magnit!&e.

Normal %el&s &e*elop the follo%ing resi&!al stressesa/ along the %el& + longit!&inal resi&!al stress.

,/ across the %el& + trans*erse resi&!al stress.c/ thro!gh the %el& + Short trans*erse resi&!al stress.

longit!&inal

trans*erse

short trans*erse

L&.$*'&%, R+#'*%, S$(+##+#>

A 6

CConsi&er the t%o plates A an& 6 (oine& ,y the %el& metal C. The %el& metal an& the :A; %antto contract5 ,!t this is resiste& ,y the plates. So the %el& metal an& the :A; are p!lle& o!t-place& in tension/ an& the plates are p!lle& in -place& in compression/.

? ? TensionThis can ,e sho%n &iagrammatically + Compression

+ +

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Trans*erse Iesi&!al Stresses.

A

c1 c2 c06

Again consi&er t%o plates A an& 6 %ith %el& metal C. n or&er to see ho% the stresses &e*elop%e m!st loo3 at the &eposition of small lengths of %el& C15 C25 C0 etc.Ass!me that the plates A an& 6 are not restraine&. Fength C1 %ill contract an& &ra% the platestogether so the le*el of resi&!al stresses across the (oint %ill ,e *ery lo%. Fength C2 %ill attemptto contract ,!t C1 %ill pre*ent this5 so -ro!ghly/ C1 is place& in compression an& C2 in tension.Fength C0 also attempts to contract ,!t is no% pre*ente& ,y C25 %hich is place& in compression5

an& C1 is p!lle& into tension. So %e fin& there is a re*ersal of trans*erse resi&!al stresses alongthe (oint. This pattern is similar for a m!ltipass %el&.

Short Trans*erse Iesi&!al Stresses.

A C 6 thic3ness

Again consi&er plates A an& 6 (oine& ,y %el& metal C. The effect is li3e that of the longit!&inal

resi&!al stresses if the %el& is a single pass. "or m!ltipass %el&s the con&ition is more li3e thetrans*erse resi&!al stresses an& %e fin& tensile stresses at the s!rface an& compressi*e stresses atthe centre.

Total Iesi&!al Stresses.n practice the three &irections in %hich the resi&!al stresses &e*elop com,ine to gi*e a res!ltantor total resi&!al stress.

Effect of restraint."or any gi*en %el&e& (oint the le*el of resi&!al stresses ten&s to increase as the restraint on the

(oint increases.

:igh Fo%

Ie&!cing restraint %ill re&!ce resi&!al stress an& re&!ce the chance of crac3ing.DISTORTION

The action of resi&!al stresses in %el&e& (oints is to ca!se &istortion.

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Consi&er a simple %el& %ith a single J preparation.The follo%ing mo*ements can ,e &etecte&

1. Contraction in the %el& metal an& :A; along the length of the %el&.2. 6o%ing5 &!e to the greater *ol!me of metal at the top of the %el&.0. Pea3ing &!e to the J angle.

. Iipple -in sheet/ a%ay from the %el&.7. Contraction in the %el& metal an& :A; trans*erse to the %el&.

1

2

&istortion

1 mo*ements 0 0

7

Control of &istortion is achie*e& in one or more of three main metho&s1.Presetting + so that the metal &istorts into the re#!ire& position.2.Clamping + to pre*ent &istortion5 ,!t this increases the le*el of resi&!al stresses.0.Wel&ing se#!ence + i.e. ,alance&5 for e)ample ,ac3s3ip %el&ing.

Other metho&s of &istortion control incl!&ePreheatingChange of prep to a more open prep -e.g. a U prep/.

Fo%er heat inp!t.P!lse %el&ing.

HEAT TREATMENT

any metals m!st ,e gi*en heat treatment ,efore an& after %el&ing. The inspector's f!nction is toens!re that the treatment is gi*en5 an& gi*en correctly5 to the &etails s!pplie&.

6elo% are the types of heat treatment a*aila,le. The temperat!res mentione& are for steel.

Process Temperat!re Cooling Ies!lt

Annealing 82@C hol&5 f!rnace cool annealing is a recrystalisation

=

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impro*es &!ctility -softens/*ery slo% cool &ecreases to!ghness

ma3es ,en&ing5 etc. easierlo%ers yiel& stress

Normalising 82@C hol&5 air cool increases to!ghness

impro*es mechanicalproperties slo% coolrelie*es internal stress

H!ench5 har&en 82@C hol&5 #!ench cool har&ens car,on steels

pre*ents car,i&e precipitationin a!stenitic stainless steels

fast pre*ents temper ,rittleness%hen -in oil or %ater/ cooling after tempering

prepares metal for tempering

Temper 77@C + B@@C hol&5 air cool increases to!ghness of#!enche& slo% steels

Stress Ielief 77@C + B@@C hol&5 air cool relie*es resi&!al stresses ,y

plastic &eformationre&!ces yiel& pointre&!ces hy&rogen le*els

slo% impro*es sta,ility &!ringmachining

pre*ents stress corrosioncrac3ing

Preheat for %el&ing 7@C + 27@C hol&

:y&rogen soa3 17@C hol&

A,o*e 82@C the grain str!ct!re an& si9e of grain str!ct!re are affecte&. 6elo% 8@@C the grain

str!ct!re is not affecte&. The soa3 time is relate& to thic3ness5 !s!ally one ho!r per 27 millimetresthic3ness. Differing cooling rates gi*e &ifferent properties to the metal5 so the cool &o%n rate isalso critical. -Possi,ly monitoring at a stan& off from the %el& ,eing treate&./ "or preheating an&hy&rogen soa3 o)y+acetylene is not to ,e !se& -too localise& a heat so!rce/5 propane is to ,e

!se&.

MONITORING THE HEAT TREATMENT

The metho& an& location of the heat treatment are important5 for e)ample in a %or3shop f!rnaceor on site !sing electro,lan3et -cooperheat type/ e#!ipment. The temperat!re is meas!re& %iththermoco!ples an& recor&e& on a chart. The main points are

controlle& heat risesoa3 time

temperat!recool &o%n rate to !nrestricte&

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The last test is a har&ness test after cooling.

temperat!re rise soa3 time cool &o%n

temperat!re

timeTypical heat treatment chart recor&ing.

The inspector sho!l& ens!re that

a/ E#!ipment is as specifie& an& cali,rate&.,/ Operators are #!alifie&.c/ Proce&!re as specifie& is !se&.

i.e. metho& of application5 rate of heating an& cooling5 ma)im!m temperat!re5soa3 -hol&ing/ time5 temperat!re meas!rement.

&/ All &oc!mentation an& recor&s are in or&er.

CALIBRATION OF WELDING EUIPMENT

nstr!mentation fitte& to arc %el&ing e#!ipment often ,ecomes inacc!rate thro!gh neglect5&amage5 %ear etc. The presence of errors in the rea&ings may remain !n3no%n an& their e)tent!nchec3e&. As a res!lt5 the *al!es of the %el&ing parameters in&icate& may %ell lie o!tsi&e the%or3ing tolerances. Conse#!ently pro,lems may ,e e)perience& in achie*ing the &esire& %el!ality. A significant le*el of &efects may ,e pre&icte& %ith conse#!ential costs of re%or3ing5repair or e*en scrapping.n high #!ality %el&ing5 reg!lar chec3ing of the parameters is there essential an& sho!l& form aman&atory part of inspection < #!ality control.There are many &ifferent types of cali,ration e#!ipment a*aila,le5 incl!&ing ammeters5 *oltmetersor e#!ipment specifically &esigne& to meas!re all the %el&ing parameters.Whate*er the type of cali,ration piece !se&5 they m!st also ,e cali,rate& for acc!ratemeas!rement + !s!ally to a national stan&ar&. The 6ritish stan&ar& for cali,rate& meas!ring&e*ices is NAAS + the National eas!rement Scheme. The 6ritish stan&ar& for arc %el&inge#!ipment is 6S B7B@.Cali,ration is carrie& o!t on any e#!ipment %ith a ga!ge *ali&ation is carrie& o!t on e#!ipment%itho!t ga!ges.

CHEC;LIST FOR CALIBRATING ARC WELDING EUIPMENT

Wel&ing nspection necessarily in*ol*es chec3ing that the correct %el&ing

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The main parameter controlling heat inp!t an& penetration. Chec3 %ith ammeters forinacc!racies5 !s!ally %ith tong testers generally any%here5 ,!t prefera,ly as close to thetorch as possi,le. Tolerance ?

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trans*erse crater -star crac3ing/

2> SURFACE IRREGULARITIES

Un&erc!t.An irreg!lar groo*e at a toe of a r!n in the parentmetal or in pre*io!sly &eposite& %el& metal. fcreate& s!,+s!rface it ,ecomes a *ery effecti*eslag trap in the ,o&y of the %el&. Un&erc!t is

essentially a notch that in t!rn ,ecomes a focalpoint for stress loa&ing5 there,y re&!cing the fatig!elife of the (oint.Ca!ses + c!rrent too high5 *oltage too high5 tra*elspee& too high5 electro&e too small5 electro&e angle.

O*erlap.An imperfection at the toe or root of a %el& ca!se& ,yca!se& ,y %el& metal flo%ing on to the s!rface of the

parent plate %itho!t f!sing to it.

Ca!ses + slo% tra*el spee&5 large electro&e5 tilt angle5poor pre+cleaning.

Crater pipe.A &epression &!e to shrin3age at the en& of a r!n%here the so!rce of heat %as remo*e&.Ca!ses + ,rea3ing the arc too #!ic3ly5 too rapi&cooling.

Spatter.Stray glo,!les of %el& material5 on parent plate o!tsi&e the %el&.Ca!ses + &amp electro&es5 too high *oltage5 too high c!rrent5 fl!) missing.

Stray flash -stray arcing/The &amage on the parent material res!lting from the acci&ental stri3ing of an arc a%ayfrom the %el&. A small *ol!me of ,ase material is melte& %hen the arc is str!c3. Thismolten pool is #!enche& &!e to the rapi& &iff!sion of heat thro!gh the plate. This maylea& to the formation of a crater that len&s itself to crac3ing5 or a change in grain str!ct!re

,y creating a martensitic or ,rittle grain str!ct!re in the area of the arc stri3e. These

&iscontin!ities may lea& to e)tensi*e crac3ing in ser*ice.Ca!ses + operator error.

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3> CONTOUR DEFECTS

The profile of a finishe& %el& may consi&era,ly affect performance of the (oint !n&er loa&,earing con&itions. Specifications normally incl!&e &etails of accepta,le %el& profiles to,e !se& as a g!i&e.

-The i&eal profile is to remo*e the cap an& lea*e the %el& fl!sh %ith the a&(acent s!rfaces.This %o!l& increase the fatig!e life of the (oint ,y a factor of 0./

E65+## +,' A contin!o!s or intermittent groo*e along the si&e of

the %el& %ith the original %el& prep face still intact.Ca!ses + not eno!gh r!ns5 operator error.

I&5

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L%5: ($ *#&.Fac3 of !nion at the root of a (oint.Ca!ses + poor %el& prep5 !ne*en ,e*el5 root face toolarge5 linear misalignment5 cleaning.

E65+## /+&+$(%$& +%'>

E)cess %el& metal protr!&ing thro!gh the root of af!sion %el& ma&e from one si&e only.Ca!ses + high heat inp!t5 poor %el& prep + largeincl!&e& angle.

R$ 5&5%$=. -s!c3+,ac35 !n&er%ashing/A shallo% groo*e %hich may occ!r in the root of a

,!tt %el&.C%*#+# + p!rge press!re5 %i&e root gap5 an& resi&!al stressesin root.

S(&:%.+ .(+>A shallo% groo*e along each si&e of a penetration ,ea&.C%*#+#+ contraction of the metal along each si&e of the

,ea& %hile in the plastic con&ition.

B*(&$(*.>-melt thro!gh5 ,lo%thro!gh/A localise& collapse of the molten pool res!lting in ahole in the %el& r!n.Ca!ses + e)cess penetration5 e)cess heat inp!t -!s!ally

at the en& of a r!n/5 localise& %el& prep *ariations.> MISCELLANEOUS

P( (+#$%($>Non+stan&ar& term. A local s!rface irreg!larity ata %el& restart.

M#%,.&Non+stan&ar& term. isalignment ,et%een t%o%el&e& pieces s!ch that their s!rface planes are not

parallel or at the inten&e& angles.

E65+##+ '(+##&..A re&!ction in metal thic3ness ca!se& ,y the remo*alof the s!rface of a %el& an& a&(acent areas to ,elo%the s!rface of the parent metal.

G(&'&.

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An in&entation in the s!rface of the parent metal or %el& metal res!lting from theapplication of a tool5 e.g. a chipping tool5 in preparation or &ressing.

H%

L%5: *#&. Fac3 of !nion in a %el&. a. ,et%een %el& metal an& parent metal. ,. ,et%een parent metal an& parent metal. c. ,et%een %el& metal an& %el& metal.

L%5: #'+%,, *#&. Fac3 of !nion ,et%een %el& metal an& parent metal at a si&e of a%el&.

L%5: &$+(-(*& *#&> Fac3 of !nion ,et%een a&(acent r!ns of %el& metal in a m!lti+r!n(oint.

I&5,*#&> Slag or other foreign matter entrappe& &!ring %el&ing. The &efectis more irreg!lar in shape than a gas pore.

O6'+ &5,*#&. etallic o)i&e entrappe& &!ring %el&ing.

T*&.#$+& &5,*#&> An incl!sion of t!ngsten from the electro&e &!ring TG %el&ing.

C//+( &5,*#&> An incl!sion of copper &!e to the acci&ental melting of the contactt!,e or no99le in self a&(!sting or controlle& arc %el&ing or &!e to

pic3 !p ,y contact ,et%een the copper no99le an& the molten panel&!ring TG %el&ing.

P*5:+(&.> The formation of an o)i&e co*ere& %el& r!n or ,ea& %ith irreg!lars!rfaces an& %ith &eeply entraine& o)i&e films5 %hich can occ!r%hen materials forming refractory o)i&es -e.g. al!mini!m an& itsalloys/ are ,eing %el&e&.

P(#$=> A gro!p of gas pores.

E,&.%$+' 5%$+#. A string of gas pores sit!ate& parallel to the %el& a)is. -Finearporosity./

B,,+> A ca*ity generally o*er 1.7mm in &iameter forme& ,y entrappe&gas &!ring the soli&ification of molten metal.

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W( An elongate& or t!,!lar ca*ity forme& ,y entrappe& gas &!ring thesoli&ification of molten metal.

GENERAL CAUSES

P(#$=. s the res!lt of gas ,eing entrappe& %ithin the soli&ifying %el& metal. Porosity %ill,e present in a %el& if the %el&ing techni#!e5 materials !se& or con&ition of the%el& (oint promotes gas formation. f the molten %el& metal cools slo%ly an&allo%s all gas to rise to the s!rface ,efore soli&ification5 the %el& %o!l& ,e*irt!ally free of porosity.solate& or !niform porosity The ca!se of this form of sing!lar porosity isgenerally fa!lty %el&ing techni#!e or &efecti*e material or ,oth.Cl!ster or gro!p porosity s a localise& gro!p of pores that may res!lt fromimproper initiation or termination of the %el&ing arc.Finear porosity Al%ays forms a straight line along a r!n of %el& an& is ca!se& ,y

gas e*ol*ing from contaminants.

O+(,%/> -Col& lap

E)cessi*e hy&rogen5 nitrogen or Use lo% hy&rogen %el&ing process filler

metalso)ygen in %el&ing atmosphere high in &eo)i&isers increase shiel&ing gas flo%

:igh soli&ification rate Use preheat or increase heat inp!t

Dirty ,ase metal Clean (oint faces an& a&(oining s!rfaces

Dirty filler %ire Use specially cleane& an& pac3age& filler %irean& store in a clean area

mproper arc length5 %el&ing c!rrent Change %el&ing con&itions an& techni#!es

or electro&e manip!lation

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Jolatisation of 9inc from ,rass Use copper+silicon filler metal re&!ce heatinp!t

Gal*anise& steel Use EB@1@ electro&es an& manip!late the archeat to *olatilise the gal*anise& 9inc ahea& ofthe molten %el& pool

E)cessi*e moist!re in electro&e co*ering Use recommen&e& proce&!res for ,a3ing an&or on (oint s!rfaces storing electro&es preheat the ,ase metal

:igh s!lph!r ,ase metal Use electro&es %ith ,asic slagging reactions

I&5,*#

"ail!re to remo*e slag Clean s!rface an& pre*io!s %el& ,ea&

Entrapment of refractory o)i&es Po%er %ire ,r!sh the pre*io!s ,ea&

T!ngsten in the %el& metal A*oi& contact ,et%een the electro&e an&%or3piece !se larger electro&e

mproper (oint &esign ncrease ,e*el angle of (oint

O)i&e incl!sions Pro*i&e proper gas shiel&ing

W+,'

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Crater crac3ing "ill crater ,efore e)ting!ishing the arc !se a%el&ing c!rrent &ecay &e*ice %hen terminatingthe %el& ,ea&

B%#+

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n the a,o*e s3etch incomplete root penetration can ,e seen ,!t5 ,eca!se of the loss ofpenetration5 incomplete root f!sion is also present.