Cold-Cracking Control in Low-Alloy Steel Welds

McMaster UniversityDigitalCommons@McMaster

Open Access Dissertations and Theses Open Dissertations and Theses

9-1-1979

Cold-Cracking Control in Low-Alloy Steel WeldsVivek Pavaskar

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Recommended CitationPavaskar, Vivek, "Cold-Cracking Control in Low-Alloy Steel Welds" (1979). Open Access Dissertations and Theses. Paper 2753.http://digitalcommons.mcmaster.ca/opendissertations/2753

McMaster Univer~ity ~

Handlton; Ontario•r ..

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S.eptembcr 1979

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LOW-ALLOY S'1'E!:L WELDS

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. ' . - .MSUR Of' DCD+Rnax: (197'9)

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(MetaUurcJY aDd ICateria1.a SC1eftCe) . -

AT11'HOR:

SUPERVISOR:

Vivek Pavaskar. B.'1'ech. (I~ InSt!tute of'recbnology. BcGlbay)

Dr. J _ S. JCirkaldy

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BAZ microst:ructure" s~ess anc1'1-lyckogen level a~.,the-fun~n-, \ -

t&J. faet="<; tDt'l~5!"'. cold '~rac:1dng s""ceptihlUty '~l1:he RAZ. •

Implant testin~4't:v ~ ious hYdroqen leve'1.s over A range of steel. CCIIIpO-

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sition~ and he 1n s ..shows how the ~mi.cros~ctur~~.hydrogen, ,~'

level influence the cx::itic4l -stress necess~ry for cold-cracking.

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•. 'Based on implant test da~cr. 4 cOrrelation fOrlUula prC'dieting. the. ~ ,

, ~critical stress necessary for cold cracking for given HAZ ~ness. ,

he~ transfet ~alculations. , martensit~~si-

'"marten'site in the HAZ -4nd hydrogen -revel, is proposed. Elnpioying this. ....... ,w~ prediction'of ~ mar~e~te 'in the ~AZ'and,. .

correlation. together

~'HAZ hardness. ~ed on ..

.\ tion-cooling rat~ relations anc h~rdness-compositiOn-cooi~grate.r~la-"

tions, an algorith~ which can p!cdict the criti~al stress necessary for

~)cracking f~ given implant c~~p~~it~on, cooling rate and hydrog~n level,

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is constructed.•

....niis, method of predicting the-critical stress'necessary for cold

cracki.ng is an improvem~nt over tht: ex.isting regression formulas fo'l;

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estindting cold-,racking susceptibility., . ~ .

This formula has been s~cJ~5sfullY addpt~d to predict cold-crack-

ing susceptibility data as obtained through'othe~ test~ such as rigid

rcstraiot~ and to re~omme~d preh~a~,levels necess~~y to aV~d cold-crack-

ing. Development and use of <l:"l inplant t~sting machine ""ith·-an automatic

w~ldin9 and loading facility i~ al~o reported.

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........ . ......'1'be.. abthoc.1a indebted ~to his aaperviaor, Dr. J. S. J:1%'ka1dy,,

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for ~u1jges~n9'~p~oblelD de&lt ~th here~ ~ 'for hia cont.iJluoua- ... •• .. 1# •

9ui~ance throughout the course of this ~rk. 'nlanks. are a1.so'due to

"many\ of t~ ,s~tf.and gradUoite students in the De-partment of Meta11urgy

and-~teria.fs S<:~ence. for their advice and assistance. X wou1d al.so

like to thank the technical staff of the Department of Metallurw and

.Materi~ls SCience.'~~ the machine shop for their assjstan<:e in de-

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veloping the lmpl~t ~sting Equipment, Thanks are also due to Mrs.

S~ Saracini'f~ the excellent typing 'of this thesis./'", , .

~<:ial suppOrt of the Natural Sciences and Engineering

Research Couneil of Canada is gratefully acknowledged ../

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OIAP1'ER 1 .IN'l'RODOCTION 1

• •CHAP'1"ER 2 ASSESSDlC THE C;:O~RACnNC. SUS~arLITY OF THE HEAT ,

. .AFP'EX:"tEO ZONE (HAZ) IN S'l"EEL t~LC:~:TS

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2.1 Weldability Formulas for !,-ssessi{\g Cold~rackinq

Susceptibility/

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2.2 Implant Testin; for Assessin;.Cold-cra~kin~·

: Susceptibi li t.y . 15J

CHAPTER 3 INFLUENCE OF HAZ r-~ICR05'!'ROC'I'URE .;.:::> HYOROGEtl LEVEL ON, ,

3.1• •

Correlatio~ For~~ Base~.o~ !~lant. Test Data.. 19

3.2 Influence of ·~~z , ~~rtc~sitc ~~d Harcness on aCR

20

3. 3· (' ~.odi f i ed' Corre l~ ti·cnt"Forr..u Ill, . : or aCR

3.~ ROle of.Hydro~en in A:f~c~in~ o. •. c~ .

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25

3.4.1 Calcula~ion o~ Hydrog~n Concentration and•, . . '

Str*:;ss I::tensity in tl'\t: ~egion of Haximum

Tria~ial i ~y" 36

3.4.2 Discussi~~. , . 38

CHAPTER ~ ~R-~ICTION O~ 0 . O~ TH~ BAS!S 0; ~~~7 ·tNPG1, PLATECR .~

pred~tiono! ~~~~ hffcc~d Z~n; Cooling Rate

4.2.1 He<lt-.Tran:ifer wit'h 30"r.",=,H. Fl'Ow

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46

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4,_2..1.1 Applic<ltio:'\ 0: 3:) HC<1t F.lm" Relation~

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2D, Heat Flow

2.SD Heat Flow .

4.2.2 Heat 'transfer With

4.2.~ Heat ~~sferli~( .4.2.4 Craphi~~l Representation of Heat Flow

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Conditions as a Function of Plate 'l'hiclcness 52

."4.2.5 Procedure for Preaicting Cooling Rate 53

4.2'.6 Discussion

4.3 Prediction of Heat Affected Zone Microstructure

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4.3,i , Klcroconstituent -.Composition - COoling,Rate R~lations 57

4.3.2-Hardness - Composition -'Cooling Rate

Reiationst

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;(--4.3.3 Prediction of HAZ , Martensite and Hardness, w

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4.3.4 Discussion 63

CHAPTER 5 DETERMINATION OF PRACTICAL WELDING PROCEDURES ON THE

BASIS OF IMPLANT TEST 82

5.1 General Remarks 82

5.2 R~lation Between Implant Test and Otht!T kstraint

Tests 82

'5.3 Determination of Prehea.t to Avoid Cracking 84

5.3.1 Estimation of Reuction Stress Developed in

the Welc 87 .'5.3.2 Influenc~ of Preh~dt on Resicual Hydrogen

Level 88

5.'.3 Prediction of Prehedt Level to Prcv~nt Crucking 91

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CHA?:=:~ 7 CONCLUSIONS

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6.2.3 The Pressure Systeo for the Implant Test

6.2.1 AutO!Datic Deposition of ~.5MAW Electrodes

6.2.2 '!'he Il:lpl4nt Loadinc;'S~tem

6.3.2 Implant 7est'Details.

6.3.1 Welding Con~tions

6.4 Prelic1nary ?ests

6.5 DisCI..-ssion

6.3 Standardization of the- Iop1a."1': Testing Procedure

6.1 General Remarks

~.2 ~sign of th"e ~lant Testinc; Machine

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APPEt'DIX I 1-3§

APPENDIX II 137

APPE~:Dn: III 139

REFE~JCES ~ 144

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LIST 'OPTJU3LES

TABLEi

PACE

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Steel weldments

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Formulas Develo~ to Assess Cold-craddng of HAZ in, , ~

•~ldin<J Precautions for Various carbon

Equivalents

~~~litY Index Proposed by Bradstreet

Re1.a.t.ion Between carbon Equivalent and weldability .

.Inde~ fo~ Low Hydrogen Electrodes

Weldin~ Procedure,for Prevention",of Cold-Cracking

'~ristensen's Implant Test' Datd \

Comparison Between Our's and Christensen's Correlation

Influence of Hydrogen Lever on,oCR

Calculated Stress Intensity and HeR Level~ ,at 0C~

Comparison Between Reported dnd Calculated Cooling

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Times' Between 800°C - 500·C .. 56

11 Prediction of OCR o~ ~e Basis of Heat Input, ~late

Thickness, Plate Co~position and Hydrogen Leve~

"12 Prediction of HAZ Hdrdn~ss and OCR for the Ito-Bcssyo

Data 73-81

13-16 Prchaat Levels Predicted for Various-Steel Compositions,

Plate Thickness, Heat Inp~t, ~nd Hydrogen Level With

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Fillet Weld Configuration

Welding Hcat Input Details

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116

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Compar~ Be~ (bserved &.~d·?:~c:ted Coo~

. tiJDeS~4 eoo.~·C - _soo·Ct

0Mtmic:al CoD:posi.tiCXlS of ...the Steels used for

_ l)apl.ant: Testing

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..PACE

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14

Bai.ley' s (14) Nomog%4JD of safe Welding Procedures

for C-Mn Steels

Ito-Bessyo (1'6) System for Determining' safe Weldi.ng

Procedures

!m;)lanting Steel .Specimen by Welding'

SChematic Diagram Showing Implant Te9t

Typical Stress VS Fracture Time Curve fo'r an

"Implant Test .. (23)

Variati~~ of 0ck With HAZ Hardness

, Weld Cracking and HAZ Hardness Plot C1S)

'COrrelation Between OCR and Both , Martensite and

Hardness as Parameters

Correlation Between OCR and HAZ INDEX

COmparison Between COrrelated and Observed 0C~ With

, Ma~site ,as p~~ter

Comparison Between Correlated and Observed ° WithCR

, Martensite and Hardness, as Parameters

Influence of Hydrogen Level on OCR

Variation of Hydrogen Index Wi th HydrC?3en Level

,Stress Intensity and Hydrogen Concentration Combina- ...

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'\

tions for Fracture(4)

as Suggested,~y Beachem...

15 Influence of Notch Radius on the Location of the

Hy,drogen Assisted • C35)Crack1ng ,-

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23-25

CUWbiua' of St:ress."Intensity· and~~ ".' .-

.CoDceDt:raj:ion~critical ~ion at (Sea

'Block D1a~"for PridictiDg (Sea on the Ba~~ of ... -~ ........."

Wel.di:D9 Beat anput, Plate Thickness," Plate C'omposi-.....

tieD.. and Hydrogen Level~

Beat F~9'" Cone.it:i.ons in Welding

vari&t5:-on. of~A3D .with:- . . ~

varla~~- of B3D with

va.r~ation of Coo1i:lg Rate 'with Plate ickness (~l) ,

Tr· f .' d Cool' . Cha (42).ans ODDa:'t:ion an ~ng Rate· rtJ ":-

" Martensite and Cooling Rate ~s for Three c-Mn

SteelS'

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26 . Cqmpa.rison Between predicted and Observed " Martensite

.' (for.Christense:\"s :,)ata(22,23»'.'.

27 ~ison Between Predicted ·A."\d ObserVed HAZ H~dness

(fOr Christensen's Data(22,23» ..

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Cpmparison .Beo.:ee,n 'Predicted A."\d Observed RAZ Hardness

(f. (lS} .

or lto-~ssyo . Data)

...C~ison Between'Predicted and Observed OCR (for

Chri~tensen's(22). Data)

, Plot of " weld Cracki:\g ~gainst Predicted 0CR'!for

lto-Be~'SYO(15) Data)

. (15tPlot of " Weld Crac~ing ~gainst Ito-Bessyo Cracking..Parameter Pc

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32 CoIIIpari.saD Between Lower Critical. .Fra~ S~.

Obtained frcm Implant '!'est and from RIC and TBr:::

'.Tests

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Critericn £or A'V'Oiding Cold-Cracks in Welded

Structures

Procedur; fOr Rec:ommend.ing Preheat.to A'V'Oid Cracking

. ~Intensity of Restraint vs Plate Thickness for Welded

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Bead .Model for Bydrog~..Diffusion Analysis

CompaJ';~son Be.bleen Predicted Preheats and ReCOlllJDended

(B.S. Standard) Preheats

System for AutOmatic Deposi ti6n of MSMAW Electrodes

Implant l.oading System .-Pre~~e System for Implan~~est

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48 General View of the Implant Tes~ing Equi~nt Complete

Wi th ~utomatic Weldi~g ana Loading Facility 117

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5~

- .Details of the weld;ing Arrangement

Detailed View of the Loading System

Weld Bead Sections for Three Heat Inputs

Typical Thermal Cycle Profile in Welding

Implant Specimen Details

.Base Plat~ Used for Implant Test

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•55 Section of Implant Specimen Showing the Location

•of the Notch 127

56.

. Typical Variation of Hardness Across the ~eld

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·FIGtIBE

Stress-Pra~~Diagam for St2e1 No.:

~-Fra~e ~~gram"~or 'S~l 50.

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CHAPTER 1....

Hydrogen induced cold-crac:king has ~n one of the .major problems'

~n~ ~ls. ~c:ks of this' type can take many fonlS _ although

they have some qene.r'a1 characteristics and are influenced by CO""IDOn

basic factors.

, As the name implies, these cracks form at low temperatures

generally below ~OOOC, and often exhibit a delay phenomenon. Even after

the weld has cooled to room temperature, there may be a further lapse of

time ranging from a' few minutes to severa1 hours.

Cold~cracks ~re not tolerated in a.structure, and since they are

'0.

..often' difficult to detect and expensive to repair, it becomes essential

fo~ the fabricator to take precautions during welding to prevent their

formation,J

Even though the general causes of hydrogen cracking and the means

of preventing these cracks are known" recent industrial surveys have

shown that cold-cracking is ~till widely encountered, indicating that

the ability to satisfactorily predict cold-cracking susceptibility has.

not been developed.

Hence, development of a t'el;'able, quick and economic method for

predicting hydrogen craclcing in a real welded.. joint is desirable to 00-

termine when conventional welding techniques can be used wi thout the

likelihood of failure from hydrogen cracking. In addition, needless

expense of preheating and low-hydrogen techniques cou1d be avoided; re-

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