SSC–199
STUDY OF THE FACTORS WHICH AFFECT THE ADEQUACY OF HIGH-STRENGTH LOW-ALLOY STEEL WELDMENTS FOR CARGO SHIP HULLS
This document has been approved for public release and sale; its distribution is unlimited.
SHIP STRUCTURE COMMITTEE
AUGUST1969 SHIP STRUCTURE COMMITTEE
MEMBER AGENCIES, ADDRESS CORRESPONDENCE To, “., ,.. s,,, ...... ,,. ,EC. ET. RY NAVAL SHIP SYSTEMS CO MMA.” SHIP ,, ,”.,”.. COMMITTEE MILITARY SEA TRAN5PORTAT!ON SE R.,., u.*. . ..s. .“.,7” M, ADca. A, T.Rs M, R, TIM, .OMINIST. AT ION w., ”,..,.., “... 20,9, .M, R, CAN ,“, ,.” 0s ,.l,, !..
August 1969
Dear Sir:
The impetus behind the use of high-strength steels in shipbuilding has been largely due to the sa.vinqs in weight of the ship. Since the high-strength steels used have a dif- ferent character than the traditional lower strength steels, a criteria for material selection, design, and fabrication is necessary. Ship Structure Committee project, “High-Strength, Low-Al 10Y Steel Weldments”, with Southwest Research Institute as the investigator, is intended to provide background for criteria development. The enclosed report, “High-Strength, Low-Al loy Steel Weldments”, describes the results of a first phase effort to identify what information is available on high-strength, low-alloy steels and what data must be devel- oped by research.
This report has been distributed to individuals and groups associated with or interested in the work of the Ship Structure Committee. Comments concerning this report are sol icited.
Sincerely,
* Rear Admiral , U. S. Coast Guard Chairman, Ship Structure Committee SSC-199
FirstTechnicalReport on ProjectSR-177
“High-Strength,Low-AlloySteelWeldments” tothe ShipStructureCommittee
STUDYOFTHEFACTORSWHICHAFFECTTHEADEQUACYOFHIGH-STRENGTH LOW-ALLOYSTEELWELDMENTSFORCARGOSHIPHULLS
by A.L.Lowenberg,E.B.Norris,
A.G.Pickett,R.D.Wylie SouthwestResearchInstitute SanAntonio,Texas
under DepartmentoftheNavy NAVSECContractNOO024-67-C5416
This documenthasbeen app~ovedfop public ~elease andsale; its distribution is unlimihed. U.S.CoastGuardHeadquarters Washington,D.C. August1969 ABSTRACT
A recentadventinshipconstructionistheuseof high-strengthlow-alloysteelswith100,000-psiyieldstrengths forshiphullstructuralelements,makinguniquedesignconcepts possible.Thisapplicationisa significantstep,butthemate- erial’sbehaviorneedstobefurtherdefined.Forthebenefitof theowners,designers,andfabricators,a projectwasinitiated bytheShipStructureCommitteeto establishwhichmechanical propertiesshouldbe usedascriteriaforjudgingperformance, toevaluatelarge-scaleweldmentstodeterminethesuitability ofthesecriteria,andto selectsmall-scalelaboratorytests thatcorrelatewiththelargescaletests.A surveyofshipyards andshiprepairersrevealedthatthesenewermaterialsarebeing usedonlyincriticalstrengthelementsofshiphulls. Welding proceduresarequalifiedbyexplosionbulgeteststodefinesafe operatingtemperaturelimits.A surveyof thepropertiesof thesematerialsandtheirweldmentsindicatedthattheHAZmight besuspectedto bemore susceptibletocrackinitiationand growththantheunaffectedbaseplate,butitwasconcludedthat moredataareneededtoestablishserviceabilitycriteria.It isrecommendedthat laboratoryinvestigationsbeperformedto determinetheeffectofenvironmentandcyclicstressesonslow crackgrowthandestablishthe fracturetoughnessofweldments, includingtheeffectsofresidualstressandmetallurgicaland geometricdiscontinuities.
ii CONTENTS PAGE INTRODUCTION...... 1 RESULTSOFSURVEY...... 3 SURVEYOFTHEUSEOFHSLAQ ANDT MATERIALSINMERCHANTSHIP HULLCONSTRUCTION. . . ;...... 4 SURVEYOFTHEMECHANICALPROPERTIESOFHSLAQ ANDT MATERIALS ANDWELDMENTS. . . . , ...... 1] THECONTRIBUTIONOFVARIOUSFAILUREMECHANISMSTOCRACK INITIATION,CRACKGROWTH,ANDTERMINALFAILURE...... 25 CONCLUSIONS...... 38 RECOMMENDATIONS...... 38 BIBLIOGRAPHY...... 39 GLOSSARY...... 43 QUESTIONNAIRE...... 47
iii
.-.,. SHIPSTRUCTURECOMMITTEE TheSHIPSTRUCTURECOMMITTEEisconstitutedtoprosecutea researchto improvethehullstructuresofshipsbyanextensionofknowledgepertainingto design,materialsandmethodsoffabrication. RADMC.P.Murphy,USCG- Chairman Chief,OfficeofMerchantMarineSafety U.S.CoastGuardHeadquarters CaptainW.R.Riblett,USN Mr.E.5.Dillon Head,ShipEngineeringDivision Chief,DivisionofShipDesign NavalShipEngineeringCenter OfficeofShipConstruction MaritimeAdministration CaptainT.J.Banvard,USh! Mr.D.B.Bannerman,Jr. MaintenanceandRepairOfficer VicePresident- Technical MilitarySeaTransportationService AmericanBureauofShipping SHIPSTRUCTURESUBCOMMITTEE TheSHIPSTRUCTURESUBCOMMITTEEactsfortheShipStructureCommittee ontechn-calmattersbyprovidingtechnicalcoordinationforthe determination ofgoalsandobjectivesoftheprogram,andbyevaluatingandinterpretingthe resultsn termsofshipstructuraldesign,constructionandoperation. NAVALSHIPENGINEERINGCENTER U.S.COASTGUARD Mr.J.J.iiachtsheim- Chairman CDRC.R.Thompson,USCG- Member Mr.J,B.O’Brien- ContractAdministratorCDRJ.L.Howard,USCG- Member Mr.G.Sorkin- Member LCDRL.C,Melberg,USCG- Alternate Mr.H,S.Sayre- Alternate LCDRR.L.Brown,USCG- Alternate Mr.I.Fioriti- Alternate MARITIMEADMINISTRATION NAVALSHIPRESEARCtl& DEVELOPMENTCENTER Mr.F.Dashnaw- Member Mr.A.B.Stavovy- Alternate Mr.A.Maillar- Member Mr.R.Falls- Alternate !Ir.W.G.Frederick- Alternate AMERICANBUREAUOFSHIPPI[iG }]ATIOLIALACADEMYOF SCIENCES Mr.G.F.Casey- Member Mr.A.R.Lytle,Liaison Mr.F.J.Crum- Member Nlr,R.W,Rumke,Liaison Mr.M.L.Sellers,Liaison OFFICEOFNAVALRESEARCH AMERICANIRONANDSTEELINSTITUTE Mr.J.M.Crowley- Member Mr.J.R.LeCron,Liaison Dr.W.G.Rauch- Alternate BRITISHNAVYSTAFF Mr.H.E,Hogben,Liaison CDRD.Faulkner,RCNC,Liaison MILITARYSEATRANSPORTATIONSERVICE WELDINGRESEARCHCOUNCIL Mr.R,R.Askren- Member Mr.K.H.K~opman,Liaison Lt.J.G.T.E.lKoster,LISN- Member Mr,C.Larson,Liaison iv 1. INTRODUCTION Merchantshiphullstructuralelementsarecurrentlybeingcon- structedof awidevarietyof steelsthatcanbe classifiedintoseveral groupssuchas theas-rolledor normalizedstructuralcarbonsteelswith yieldpointsupto 40,000psi, thelow-alloysteelswithyieldpoints rangingfrom40,000to 75,000psi, andthequenchedandtemperedlow- alloysteelswithminimumspecifiedyieldstrengthsabove75,000psi (I+SLAQ andT steels). Figure1 depictstwohybridsteelhullsandthe specificstructuralelementsmadeof FISLAQ andT steelsincurrent designs.
Thebehaviorof as-rolledandnormalizedsteelsinmarineservice is knownwellenoughto establishrequirementsfortheirusageinship hullconstruction.(1,2, 3)’~CThisis notthecasefor HSLAQ andT steels, althoughthereis a considerablebodyof informationonthebehaviorof thesesteelsderivedfromlaboratoryinvestigationsandfromtheiruse inotherengineeringstructures, (4,5,6)
A three-phaseprogramhasbeenundertakento definetherelation- shipbetweenmaterialpropertiesandperformancecharacteristicsof FISLAQ andT steelweldmentsbeingused~ntheconstructionof merchant shiphulls, andto delineateinvestigationsrequiredto developthe criteriawhichwill assurelongtermsatisfactoryservice. Thisscope oftheoverallprogramis as follows:
PhaseI, Item1 - Determine,usingexistingknowledge, those mechanicalpropertiesandquantitativevaluesof FISLAweld- mentswhichshouldbeusedas criteriaforjudgingsatisfactory performanceinthevariousserviceenvironmentsof a cargoship hull.
PhaseI, Item2 - Undertakea studyoftheavailableweldingpro- ceduresapplicableacrosstheboardfor repairweldingany combinationof FISLAandplaincarbonshipsteelsandprovidea weldingtechniquecapableof producinganadequatetemporary weldin smallremotepartsor at seawhereweldingsupplies, procedurecontrols,andwelderqualificationsarelimited. PhaseII - Evaluatelarge-scaleweldmentsto determinethe suitabilityofthecriteriaselectedinPhaseI, Item1.
Phase111- Selectsmall-scalelaboratoryteststhatcorrelatewith thelarge-scaleweldmenttests,
‘~SuperscriptnumbersinparenthesesrefertotheBibliographyatthecnd of thispaper.
,---<7 --:-
~. –------2
n A517/A514 m A537-A UAB$-C
~ D ‘“ ~-~ r7 ~“~ /===~’”.. r———”————__ ‘7 \k 1 L——.——.A——— ( 6,
CROSSSECTIONS SHOWINGUSEOF n A517{A514 HSLASTEEL m A537-A
Fig.1. UseofHSLASteelinModernShips -3- ThisreportsummarizestheresultsobtainedinPhaseI, Item1. Thisstudyincludeda surveyoftheuseof FISLAQ andT steels in shipbuilding,withemphasisonfabricationandinspection procedures,anda reviewof relevantdataonthemechanical propertiesofthesematerials.
H. RESULTSOFSURVEY
Theshipbuilding,shiprepairing,andsteelindustriesweresur- veyedto determinethepresentstateofutilizationof HSLAQ andT materialsandto delineateinvestigationsrequiredto establishthecriteria whichwill assurelongtermsatisfactoryserviceof merchantshiphulls.
Thesurveyproducedthefollowinginformation:
HSLAQ andT materialsarecurrentlyusedonlyincritical highlystressedelementsof shipstructure.
Thisclassof materialis morehighlystressed,bothfrom residualandservicestresses, thansimilarlyusedcarbon steel. For example,changesinoveralldesignandreduced sectionsizes raisethestresslevelsinlocalizedareasby .,.-” increasingtheflexibilityofhulls. Also, residualstresses inFISLAQ andT weldrnentsareexpectedtobe higherthanin carbonsteelweldmentsbecauseofthehigheryieldstrength oftheHSLAmaterials.
Theoccurrenceoffabricationflawsanddefectscreatesa moresevereprobleminIHSLAQ andT materialsthanin carbonsteels. Qualitycontrolandinspectionproceduresin shipstructureshavenotbeenrefined‘coa degreecommell– suratewiththematerialsFabricationprobl~ms,where HSLAQ andT materialsareused. It is essentialthatthese refinementsbemade.
TypicalHSLAQ andT basemetalpropertiesare as follo\vs:
Cv at - 60 UTS 0.270Ys Elong. Hardness E20S (ft-lb) (ksi) (ksi) (%) (Rc) NDTT(“F) —L —T ll!5-i.25 105-115 20 25-30 -50 30-.55 20--[[)
. HSLAQ and‘1’submer~cdarcwrldm
25-30 20-40 LO-35 10–’[0 -101,1 11[) -4-
ThereareverylittledataonHSLAQ andT materialswhich areapplicableto the evaluationof shipstructureserviceability. SteelswithhardnessvaluesequaltothoseoftheHAZin A514/A517 shipstructureweldmentsexhibitsusceptibilityto crackinitiationandslowcrackgrowthinmarineenvironments whensubjectedto stressesless thanthevaluesexpectedin shipstructures. Thesesteelsmayalsohaveappreciably ,..’ <’‘ shorternotchedspecimenfatiguelives inmarineenviron- ,//”“ mentsthandocarbonsteelswhenthedifferencein service stresslevelsis considered.
TheHAZinHSLAQ andT weldmentsis suspectedto bemore susceptibleto c~ackinitiationandgrowththantheunaffected baseplatebecauseof its propertiesandits geometriclocation withrespectto discontinuitiesandhighestcombinedstresses. TheonlyHAZpropertythatcanbe accuratelymeasuredin an actualweldmentis hardness. Thisis usefulinformation becausehardnessvaluescorrelatewithtensilestrengthand fracturetoughnesspropertiesfor a particularsteelalloy.(7)
HI. SURVEYOF THEUSEOFHSLAQ ANDT MATERIALS INMERCHANTSHIPHULLCONSTRUCTION
A. SurveyProcedure
Theinitialprogrameffortwasthedeterminationofwhy,where, andhowHSLAQ andT steelsareusedincurrentandplannedmerchant shiphullconstruction.Thisinformationis requisiteto selectingthe performancerequirementsof thematerialsof construction,establishing therelationshipsbetweenpropertiesandserviceability,andprogram development. A questionnairewaspreparedandsentto all oftheshipbuildersand andshiprepairfacilitiesinthecountrywhoarepotentialusersof HSLA Q andT steelstructuralelementsinmerchantships. A samplequestion- naireis includedas theAppendix.Ofthe56 questionnairesdistributed, 10werereturned.TheCoastGuard,ABS, andHSLAQ andT steelsup- pliersw-erealsoqueriedto assurethata completelist of shipyards usingthisclassof materialswasdeveloped.Thedatafromthequestion- nairesandothersourceswerecompiled,summarized,andreviewedand a fieldtripitinerarydeveloped.Theitineraryincludedvisitsto all of theshipyardsusingA514/A517materialsinhullconstruction.The itineraryalsoincludedvisitstoweldingsupplymanufacturers,theR&D laboratoriesof steelsupplie!+s,andotherR&Dlaboratoriesthathad studiedthepropertiesor participatedinthedevelopmentof thesemate- rials. It alsoincludedvisitsto Japaneseshipbuilders,researchand developmentlaboratories,anduniversities.
Theshipyardvisitsweremadebya weldingengineeranda structuralengineer,eachof whomha~ : Thebasicplanfor a shipyardvisitwasto: Reviewplansandspecificationsincludingdesigndetails, weldingprocedures, qualitycontrol,andinspectionpractices. Observefabricationpracticesindetail,includingauditingof workmanship. . Critiqueof materialsof construction,practices,andproblems encounteredinHSLAQ andT fabricationwithshipyardperson- neldirectlyconcernedwitha responsibilityforwelding. Specificdocuments,information,anddataof particularinteresttothe programwererequestedandobtainedforprojectfiles to serveas a basisfor futurework. Theothervisitsweremadeto determineandcollecttheinformat- ion availableonHSLAQ andT materials,includingweldments,andon specificlaboratoryteststhatbestsimulatetheserviceabilityof a structure. Thisinformationwasreceivedonthesameconfidentialbasis as theshipyardinformation.Theexperiencerecordof HSLAQ andT materialsinotherstructures,includingfabricationproblemsandfailure investigation,wasreviewedinrelationshipto shipyardpracticesand marineenvironments. B. SurveyResults 1. Design Thereareseveralmechanismsof failurewhichshouldbe consideredinmerchantshiphulldesign,including: Excessiveplasticdeformation,includingplastic instabilityy Excessiveelasticdeformation,includingelastic instability . Tensile(ductileor overload)failure . Lowcycle(highstrain)fatigue . Corrosion -6- Stresscorrosion Corrosionfatigue . FastIracture,includingcleavageandlowenergytear fracture. Anactualservicefailure,of course,is usuallytheresult of morethanoneof theaforementionedmechanisms. Thestructuraldesignproblemshouldinclude: Assurancethatanas-builtstructureis adequateto withstandserviceloading . Assurancethatserviceloads, or environmentsand incidents,donotdegradestructuralor materialsprop- ertiesbelowacceptablelimitsduringrequiredservice life . Assurancethatjointdetailsarereviewedin 1ightof materialspropertiesto minimizeflawsthatwould degradeperformanceinwhichthecalculatedstress magnitudedoesnotexceedanallowablestressvalue derivedfrommechanicaltestpropertiesof themate- rials of construction.Environmentaleffectscanbe consideredbytheinclusionof thisparameterina specifiedmaterialstestprocedure.Theeffectsof fabricationflaws, defects, andresidualstressescan seldombe so included,becauseof thelimitationsof test specimensize andotherpracticaldifficulties, andmustbe developedseparately.Theevidenceis thattheproblemof fabricationflaws, bothincharac- ter andeffect, is differentinHSLAQ andT steels thaninlow-carbonsteels.(8-13) Qualitycontrolandinspectionproceduresmustconsequently be reconsideredinthelightof propertiesof materialsof construction. Theconstructiondetailsshouldprovideinspectablejoints. Thisstudyis limitedtotheeffectsof changesinmechanical propertiesof materialsof shiphullconstructiononserviceability.The factthatthestructuralgeometryof shipsutilizingHSLAQ andT steels is alsodifferentfromthecarbonsteelshiphullswhoseservicerecord is thepresentbasisfor designmustnotbe forgotten.Ingeneral,these differencesderivefromthenewcargohandlingsystemsthatrequire modificationof strengthdeckdesign, Thefactorsrequiredfor satis- factoryutilizationof carbonsteelsinmerchantshiphullconstruction havebeenestablishedandthetaskathandis to establishlikefactors IorHSLAQ andT steelstoprovideequalserviceabilityandpermit economicconstructionfortheparticularcaseof shipyardconstruction -. ;..-.. :,’,~ .! ,’,., -7- .. 1, andmarineservice.(14-17) ThedesigndetailsoftheseveralshipsusingHSLAQ andT steelswerereviewedduringvisitsto variousshipyards. SeeFigure1 fortypicalhullsectionspresentlybeingfabricated.(18-22) Theincreased areaofhatchesinsuchshipsis compensatedforbyusinghigher-strength steelsinlieuofheavysectioncarbonsteelplatesandshapes. This avoidsseveraladversegeometryandfabricationfactors. 2. Fabrication Themostcommonweldjointsobservedduringthevisitsto variousshipyardswerethedoubleweldedI)V!Tjoint, intermittentfillet joint, doublefillet“T” joint, doublebevel“T“ joint, andthedouble“bevel cornerjoint(filletreinforced).Theseweldjointconfigurationsare standardfor all typesof stiffenedplateandstructuralconstruction,The onlyjointconfigurationwhichcausedsomeconcernwasa doublebevel cornerdetailusedto jointthedeckscantlingsto gunnelbarandsheerstrake. Theconcernis thatthejointdoesnotlenditselfto radiographicinspection. Thedifficultyof inspection,coupledwiththehighrestraintoftheweld jointandthehighstressthroughthethicknessof thedeckplating,can leadto problems. Theseproblemscanbe overcomebychangingthe jointdesignto makeit morereadilyinspectable,or byemployinga more reliableweldingprocess. Properlydesignedjointsusuallyreducefiller metal requireme~ts,thenumberof passes, anddistortion.Theyalso facilitategoodworkmanship. At shipyards,mostjointdetailsarepreparedbyoxygen-gas torchcutting. Thismethod,whenproperlyused,leavesverylittleslag or oxideonthe preparedjoint. Inthecaseof alloysteelswithrelatively highhardenability,therearetwofactorswhichmustbe consideredwhen jointsarepreparedinthismanner. Thefirst andmostimportant factoris thepossibilityof crackingalongthetorchcutedge. The secondfactoris thelackof ductilityandincreaseinhardnessinthe HAZcausedbythetorchcutting.Inthecaseof FISLAQ andT steels, it l-naybenecessaryto grindthetorch-preparededgeof thickerplates to eliminatecracksandhardtransformationproducts.As steel hardenabi.lityincreases,themorelikelygrindingwillbeneeded. Relativecalculatedhardenabilitynumbersare shownin TableI. AllweldinginvolvingA514/517materialsis supposedto })( [:crformedusinglowhydrogentechniquesinconjunctionwithcontrolled pr(:lleatandinterpasstemperatures.Theobservedweldingprocedures varylittlefromyardtoyardandessentiallyconformto thoseforHY80 ;~sspecified inNAVSFHPS0900-006-9010. ThemajorityoftheweldingperlormedonA514/517mate- ~i;ll~is accomplishedusingtheshieldedmetalarcprocesswith l’:] I 018 M or G F,l.cctrodes. Tabe 1. CornPositonandPropertiesofASTMA514/A517-Steels andOtherSteelsUsedinShipConstruction ASTMA514/A517 ASTMA537 Grade A B c D E F G H T K _ AS7T4A441 ASTMAZ42 A Chernistry (Ladle! c 0.15-0.21 0.12 - 0.21 0.10-0.20 0,13-0.20 0.12 - 0,21 0.)0-0.20 0.15-0.21 0.12-0,21 0.12 - 0.21 0.10-0.20 0.22!&x 0.20 Max 0.20Max Mn 0.60-1.10 0.70- 1.00 1.10. 1.50 0.40- 0.10 0.40- 0,70 0.60- 1.00 0.80-1.10 0.95 1.30 0.4!. 0.70 1.10- 1.50 0.85- 1.25 1.25Max D.70-1.40 P 0.035Mm 0.035Max 0.035Max 0.035Max 0.035Ma. 0.035Max 0.035Max 0.035Max 0.035Max 0.035Max 0.04M= .- 0.040M= s 0.040Max 0.040Max 0.040.Max 0.0.0Max 0.040Max 0.040Max 0.040M= 0.040L{a= 0.040Max 0.040Max 0.05 kin D.05Max O,050Ma. .5i 0.40- 0.80 0.20- 0.35 0.15-0.30 0.20 0.35 0,20 0.35 0.35.0.30 0,50- 0.90 0.20- 0.35 0.20-0.35 0.15 - 0.30 0.30hi.. .- 0,!5 .0.50 Ni -- .. .. -. .- 0.70-1.00 -- 0.30- 0.70 ...... - .- c, 0.50- G.80 0.40 0.80 .- 0.85- 1.20 1.40..?.00 0.40- 0.45 0.50- 0.90 0.40- 0.65 . . .. -. . . .- Me 0.18 0.20 0.15- 0.25 0.20- 0.30 0.15 0.15 0.40- 0.60 0.40- 0.40 0.40. 0.60 0.20- 0.30 0.50- 0.65 0.45- 0.55 -. . . . . v. -. 0.03 0.08 -- .. -- 0.03- 0.08 -. 0.03. 0.08 .. .. 0.02Min . . . . T, .. 0.01 0.03 -- 0,04-0.10 0.04-0.10 -...... - ...... Zr 0,05.-0.15 .. -. -. -- -. 0.05-0.15 . . .. .- -. -. -. c. .- .. -. 0,.?0- 0.40 0.20 0.40 0.15-0.50 .. .. -- -. 0.20 Min -. . . B 0.0025Max D.0005- 0.0050,001 0.0050,0015 0.0050.0015- 0.0050.002- D.0060,0025Max 0.0005Mi. 0.001- 0.005 0.001 0.005 . . . . -. CA 11.1 4.5 8.0 17.2 M. z 23.7 25.0 4.62 8.1 1.46 1.02 1.17 I Carbon (Equiv.) Ew E.60 0,56 0.71 0.65 0.B9 O.71 0.75 0.62 0.46 0.56 0.43 0.41 G.43 AMGr.des T.11,il. 115,000to135,000psi 63,000- 70,00Ll63,000 70,00065,000- 85,00G Ymid 100,000psi h~lm 42,000 50,00042,000 50,00046,000 50,000 mong.2 in. 18%Mm 16 18% 16- 19% 19-23% Hardness Radius= 2 X Thicknessbr 1 in. andunder Radwfi1 T to 3!4 in. Incl. Radius1-1/2T to 1-1/4i.. Inci. Ra&ius. 3 X ‘Ihick.e,s for over 1 to2-1{2 in. 1..1, R.C,”S 1.1/2T.v., 1t. Radius2 T over 1-1f2 in. Incl. 1.1/4m 2 i.. in.1. Rzdiua2 T OVer1-1!2 in. -9- WhenA514/517materialis weldedto oneof themedium strengthmaterials,theusualprocedureis to usethepreheat,interpass, andlowhydrogentechniquesrequiredbythehigh-strength,quenchedand temperedmaterial. Theweldmetalstrengthis usuallychosensuchthat it matchesthatofthelowerstrengthsteel. ?Iowever,oneof theyards visitedchoseto matchtheweldmetalstrengthtothehigher-strength basematerial. Withoneyardexcepted,therootpassof grooveandtee weldsandsinglepassfilletweldsaremadeusingE8018or E9018elec- trodes. Thisis doneinanefforttominimizethechanceof rootcracking ingrooveweldsandtransversecrackinginfilletwelds. Thisselection wasbasedontestswhichindicatedthatdilutionwiththebasemetalraises thestrengthof thedepositedweldmetaltonearthatofthebaseplate. Theuseof thelowerstrengthelectrodesforrootandsingle passfilletweldingseemstobe aneffectivemethodinreducingthe chanceof rootcracks. Theonlydrawbackto thisprocedureis thepos- sibilityofthewelderusingthelowerstrengthelectrodeforweldingsub- sequentfillerlayers. Anyprocedurewhichrequiresmultiplefiller metalshasthesamedrawbackandrequiresclosesupervisionbythose inchargeof qualitycontrol. Onesemiautomaticprocess, shortcircuitingMIG, iS currentlyusedbytheshipyardsinHSLAQ andT welding. Thisprocess is beingusedto makea fullpenetrationcornerweldof deckplatingto sheerstrake. Twofullautomaticprocesseswereinuse, thesubmerged arcandMIGprocesses. Theonlysubmergedarcweldingprocedurein useforwhichdetailswereavailablelimitstheheatinputto 25,000joules/in. for l-in. -thickplatebecauseof theresultsobtained ontwoexplosionbulgetestserieswhichwerefabricatedandtestedfor weldingprocedurequalification.Oneserieswasfabricatedwitha maxi- mumheatinputof 55,000joules/in. andthesecondwasfabricatedusing a maximumof 25,000joules/inch. Althoughtheformerdidnotqualify withtheexplosionbulgetest, theauthorsdo not considerthelatterto be economical.It is possiblethata successfultest seriescouldhave beenfabricatedusinganintermediateheatinputthatwouldbemore economicalthanthe25,000joules/in. procedure. TheautomaticMIGprocedurewhichwasobserveduseda heatinputof 55,000joules/inch. Thisprocedurewasalsoqualifiedby theexplosionbulgetest. Thetwoprecedingparagraphsindicatethatthecalculated heatinputmaynotbe anaccuratemeasureof,theheatactuallytrans- mittedtothebaseplate. Apparently,a largeportionof thearcenergy oftheMIGprocessis dissipatedas a~cradiationandis nottransmitted toih~>weldpuddleandultimatelyto thebaseplate, Thiswouldmean thateachzoneintheHAZwouldbe attemperaturefor a shorterlength -1o- Oftimeandthateachzonewouldbe narrower. Sincemostmetallurgical reactionsaretimeaswellas temperaturedependent,it canbe assumed thatHAZdegradationmaybe a functionoftimeattemperature.Forthis reason,it appearsthatdatamustbe gatheredor generatedso thata factorcanbe addedto theheatinputformulawhichwouldgivea more accuratevaluewhenconsideringa specificweldingprocess. Themajorproblemwhichconcernsfabricatorsof high- strength,quenchedandtemperedsteelsis weldrnentcracking. There areessentiallythreetypesof crackingwhichcanoccurwhenthesetypes of steelsarewelded.Theyare: WeldmetalandHA.Zcracking- Associatedwiththe transformationof austeniteto martensite, this typeof crackingis a functionof coolingrateandseemsto be independentof externalrestraint. Hotandcoldcracking- Hotcrackingis associatedwith lowmeltingpointconstituentswhichlackductilityatthe hightemperatureendofthesolidificationrange. Cold crackingis a functionof externalrestraintcoupledwith coolingratesandmetallurgicaltransformations. Delayedcracking- Thistypeof crackingis themost seriousas it canoccurdaysafternondestructive testingandcanleadto failurebyfatigueand/orfast fracture. TheU. S. NavalAppliedScienceLaboratory(NASL)has performedconsiderableresearchonweldrnentcrackingproblemswhich areassociatedwithhigh-strength,quenchedandtemperedsteels. Althoughtheirworkhasbeenonthe“highchemistry”steels, their approachandtests shouldbe applicabletotheA514/517varietyof steels. TheNASLWeldabilityTestSystemis logicalandappearsto be a good approachtotestingfor cracksusceptibility.(23) TheNASLsystemis actuallya seriesoftestswhich includesa modifiedControlledThermalSeverity(CTS)test, Keyhole SlottedPlatetest, andNASLCircularFilletWeldability(NCI?W)test. Thistestsystemessentiallyevaluatesa fillermetal/basemetalsystem forthetypesof crackingdescribedabove, Thissystemcanbe usedto evaluatebasemetalandfillermetalchemistry,degreeof restraint, weldingparameters,andtheirinteractionona givenbasemetal/fiHer metalcombination.Theresultsreportedinthepaper(23)correlatewith fabricationexperiencegatheredin shipyardsandwithexperimentalwork performedonlargemodels. 3. Inspection Economy,soundness,andmechanicalpropertiesaredeter- mindedbyweldingprocedurefactorsincludingmaterialthickness,mate- -11- rialquality,jointdesign,weldingpositionandsequence,fillermetal, shieldingsystem,preheatandinterpasstemperatures,heatinput,post- weldheattreatmentandweldsurfacetreatment.Qualitycontroland inspectionproceduresassurethatthebestpossibleweldrnentis obtained. Thelackof sufficieillqualitycontrolof HSLAQ andT baseplateusedin shipbuildingmakesit likelythatmanyofthefactorswhichcontrilmt~to weldrnentcrackingarepresent,suchas segregatesofnonrnetallicinclusions andalloyingelementsandvoidssuchas laminations.Theshipyard environmentmakesit difficultto eliminatehydrogeninducedcracking. Consequently,thereis a likelihoodthatmanyburiedflawsandextensive crackingcouldexistinHSLAQ andT weldrnentswhoseorientationwould preventtheirdetectionbyradiography.Thishasbeenthecauseof failureinotherstructuresmadeofthisclassofmaterials.(24) Onlyone shipyardvisitedusedbothradiographyandultrasonicinspectionfor buriedflawanddefectdetection.All othersrelyonradiographyalone. IV. SURVEYOF THEMECHANICALPROPERTIESOF HSLAQ ANDT MATERIALSANDWELDMENTS A. MechanicalPropertiesandServicePerformance Themechanicalpropertiesof steelsarealteredbyheattreatment andplasticdeformation.Weldingprocessesimposecomplexandsevere thermalandmechanicalconditionsthatproduce~radientsinnlicrostruc- turesandpropertiesinthezonesadjacenttothefusionlines. Fabrica- tionflawsanddefects,andresidualandrestraintstressesassociated withweldingprocesses,alsoaffectthestrengthoftheresultingstructures. Properweldingproceduresfor low-carbonsteelsprovideweld- rnentswithsoundnessandlmechanicalpropertiessuperiorto basemetal. Thislimitstheproblemof serviceabilitydeterminationtoweldingpro- ceduredevelopmentandmeasurementof baseplateproperties.At the presenttime, however,thepropertiesof theheat-affectedzoneofthe FISLAQ andT steelsar~inferiortobaseandweldmetalpropertiesin weldrnentsmadebythebestavailableweldingprocedures.Hencethe problemof serviceabilitydetermination01HSLAQ andT steelsmust includemeasurementofHAZpropertiesandconsiderationoftheinter- actionoftheaccompanyingeffectsof fabricationflawsandresidual stressesonbehavior.(24-27) Thefactorsappliedto mechanicaltest resultsto obtaindcsigll stres.,valuesto accountfortheseparameterscannotbe assumedto bc thesamefor HSLAQ andT andlow-carbonsteels, hencethey mustIIC developedbyexperienceor experiment.Inaddition,thereis insuffi[:itllt informationavailableto properlyassessthebehaviorof HSLAQ andT steelbasemetalinmarineservice;thisincludeslack01knowlrdy,~.of shipstructuralmechanicsaswell as 01materialsproprrtics. pJ’3\Llr- theless,theexperienceswiththeuseof HSLAQ andT mi~t~’rialsill otherstructuralapplicationsandthe provideabackgroundfor delineating -12- a designbasisfortheuseof HSLAQ andT steels. Theywill alsoprovide preliminarypredictionsof servicebehaviorof shiphullstructural elementsmadeofthesematerials. A requirementof theweldingprocedureis thatitwillprovide specimensthatwill “qualify”usingassignedspecimentestprocedures. These“standard”specimentestprocedures(tensile,hardness,andnotch toughness)mayor maynotbe relatedto serviceabilityandmechanismsof failure. Theproblemhereis thatthespecimentestprocedureanddata interpretationcriteriamaybe establishedfor a specificsetof materials properties,suchas onemightobtainfor low-carbonsteels, bycorrela- tionwithserviceexperience.Theyarenotnecessarilyapplicableto differentmaterials,suchas HSLAQ andT steels, yethavecommon acceptancerequirements. Therearea set of importantpropertieswhicharenotcurrently evaluatedas a standardizedprocedure.Thesepropertiesincludefatigue strength,fracturetoughnessandtheeffectsof environmentonservice- ability. Thefatiguestrengthis theonlypropertyforwhichdataonHSLA materialsareavailableandwhichrelatesdirectlyto knowndesign requirementsof 25,000psifor 2 X 106cycles.(28) Laboratorydataonthe fatiguepropertiesinair, aqueous,andsalinewaterenvironmentsare available. Therearealsolimiteddataon corrosionresistancewhich areinsufficientto establishquantitativepredictionsofbehaviorbutdo indicatetrendssuitablefor comparingtheserviceabilityof HSLAQ and T materialsto carbonsteelsinmarineenvironment.A fracture mechanicsapproachcanbeusedto establisha relationshipbetween stresslevelandcracksizewhichcaninitiateanunstablefastfracture. Theeffectoftest specimensize is equallyimportant,andequally difficultto assess, Testspecimenandactualhardwares~zeeffectsinvolve severalvariablesthataffecthardwarebehavior.Inaweldrnent,thereis theunpredictablepresenceanddistributionof residualstresses, flaws, andmaterialproperties.It cansafelybe saidthatnoselectedsegment of a weldmentwillhavecharacteristicsidenticalto thoseof another segment. Consequently,nosegmentcanbe expectedtobehaveexactly as anothersegment,Ina largeweldedstructure,thelikelihoodis high thattheworstconditionswillexistsomewhere,so thismustbethebasis for anengineeringestimateof structuralbehavior. It is obviousthatconsiderableempiricalworkis required,inlieu of experience,to resolvetheseproblems. Inparticular,it is essentialto determinefor I-IAZmaterial: Theslowcrackgrowthbehaviorof flawsin regionsofhigh stressandinmarineenvironments Crackinitiationandgrowthin responseto cyclicloadsinthe marineenvironmentas relatedto shiploadings Fastfracturebehaviorinmarineenvironments. .13. Thesedatacanbeusedto establishsurveillanceproceduresaswellas qualitycontrolandinspectionrequirementsfor structuralelementsmade of HSLAQ andT materials. It shouldbenotedthatthisinformationis notavailablefor carbonsteelmaterialsofthethicknessrequiredinthe structureswhichuseHSLAQ andT materials. Considerationmustalso be giventothedifferencesinbehaviorbetweenHSLAQ andT materials andtheirpredecessors.Inothertypesofhardware,thishasresultedin initialunacceptablefailureexperiencethathasfurtherresultedinrestric- tiverequirementsto eliminatetheproblemsencountered.(5) Hopefully, thiscanbeavoidedin shipstructuresbydevelopmentoftheinformation requisiteto establishingthelimitationsof thesematerialsof construction as wellas theirattributes, B. Hardness Theproblemathandis to evaluatetheserviceabilityof EISLA Q andT weldmentsmadehyacceptableweldingprocedures.Thefirst insightintothenatureofthisproblemis obtainedbymicrohardness surveysacrosstheweldrnent.Hardnessis anindicatorof thetensile propertiesof steelsand,becaus~materialsbehaviorvarieswithtensile properties,indicatestrendsin behavior.Increasein yieldandtensile strengthof a materialgenerallyindicatesdecreasein fracturetoughness andductility,andincreasein sensitivityto env-ironmentaleffectsonflaw growth. DiamondpyramidhardnesssurveysmadeonA514andA517 materialsindicateHAZstrengthlevelsareintherangeof sensitivityto stresscorrosioncrackingandlowfracturetoughness.Typicalmeasured rnaxirnumHAZhardnessvaluesare”DPH425whichconvertsto RockwellC43. c. TensileStrendh A basicsourceof datafor estimatingserviceabilityis thetension test.(22) Thematerialspropertiesobtainedareyieldpoint,tensile strength,elongation,andreductioninarea. Thistestis performedon as-r,~ceivedbaseplate,weld, and sometimesonbaseplateheattreated to simulateheat-affectedzonematerial. Theevaluationof residual stress, plasticstrain,andnotcheffectsonrealhardwarematerialsof constructionpropertiesarenotincludedin thistest, Thesedataare primarilyusefulfor qualitycontrolandmaterialcomparison. Theinitialtensiontestpropertiesspecifiedarefor as-received baseplate. Theas-receivedbaseplatepropertiesmustbe considered fromthestandpointof eventualHAZpropertiesas wellas fromthatofthe requiredbaseplateproperties.It is considereddesirableto haveopti- mumobtainablepropertiesinas-receivedbaseplate. TheminimumO.27’ooffsetyieldstrengthrequiredIortheclass of materialsconsideredis 100,000psi; thisvalueis usedas a design.basis for stabilityanalysis. The mill testyieldstrengthis usuallyhigher than100,000psi andcanbeincreasedfurtherbyreducingthetempering temperatureor bycoldwork. Thetensilestrengthof thesematerials .14. is usuallyintherangeof 115,000to 135,000psiandcanalsobeincreased bythermalor mechanicaltreatment,‘cutnottothesamedegree. An increaseinthesevaluesis usuallyaccompaniedbya reductioninnotched fatiguestrength,ductili~y,andnotchtoughness;hence,it is ess~ntial to establishcontrolontheseproperties. Ductilityis anothermeasureof processcontrol. Sincethisprop- ertyis alsoaffectedbymaterialflawsanddefectsin specimensstressed inthetensileinstabilityregionof thestress-straincurve(abovemaxi- mumtensileload),ductilityis notanintrinsicmaterialsproperty. Typicalvaluesfor ductilityare 20%elongationina 2-in. gagelengthand 65~0reductionof areameasuredona standardASTMspecimen. Theweldmaterialshouldhaveequalor bettertensileproperties. HAZmaterialtensilepropertiesaretoodifficulttomeasureindepen- dentlyto serveas a qualitycontroltensiontest requirement,Theonly indexof thesepropertiesis hardnessmeasurementsandnotenoughwork hasbeendoneto providea guidefor selectionof suitablevaluesofthis property. D. NotchToughness Threefracturetoughnesstestsare currentlyusedwhichare suit- ablefor qualitycontrol(seeSectionVI onterminalfailure). Theseare theCharpyV-notch(ASTME23), theDrop-Weight(ASTME208), and theExplosionBulgeCrackStarter(NAVSHIPS0900-oo5-5ooo). 1. CharpyV-NotchTest TheCharpyV-notchtestis suitablefor ev-aluatingbase plateandweldmaterials. Correlationswithfracturemechanicsvalues havebeendevelopedbyWestinghouse,U.S.steel,andtheI’Ja=l ResearchLaboratory(NRL)whichprovidea suitablebasisforusingthe resultsofthistest. Theseresultsindicatethat25 ft-lb absorbedenergy is a minimumvaluefor 1-in. -thickplatewhichwillprovideanacceptable criticalcracksizeat yieldstrengthloadings.(29,30) Laboratoryinvestigationsusingotherbrittlefracturetests havedemonstratedtheseveredeg~adationof fracturetoughnessinHAZ material. Consequently,it is necessaryto offsetthisreductionby increasingminimumtoughnessinbaseplate. Figures2and3 presentsomenotchtoughnessdataon A517F materialsthathavebeenusedforthesecorrelations. 2. Drop-WeightTest Thedrop-weighttestdefinesthenilductilitytransition temperature(NDTT).(26) Thistesthasseveraldeficiencies(forexample, materialtemperingbybrittlebeaddeposition)butdoesprovidea better -15- Fig.2. EffectofWeldPre- heatat47,000Joules/ in.onCharpyV-Notch CurvesforSimulated Grain-Coarsenec!t!eat- AffectedZonein% in. ASTMA517F5 -2001 -1501 -1001 50I 01 1—.1+ c L 50 100 J -140-120-100-8o-60 -40-20 0 20 40 60 70 I I t ‘O L—L———J -1oo -50 0 50 100 Temperature, “~ -75 -50 -25 0 +10+25 +50 +75 (b) .A517ASteel Ternperaturc,“F QuenchedandTemperedBase (a) ~44~,~T-75-HS,andA517Steels PlateTensileProperties Tensile Yield Steel Strength(psi) Strength(psi) A441 70,000 50,000 LT-75-HS 90,000 75,000 A 517 115,000 100,000 Fig.3 CharpyV-NotchImpactEnergyCurves -16- indexof temperaturetransitionfromductileto brittlebehaviorthanthe CharpyV-notchtestandis moreconvenientthantheexplosionbulgetest for shipy-arduse. If drop-weighttestscannotbe runbecauseof material limitations,it is recommendedthattheCharpyV-notchimpactenergy valueof 40 ft-lb be usedas theNDTTcorrelationenergylevelfor esti- matingtheNDTTof thebaseplate, Thatis, theas-receivedbaseplate CharpyV-notchimpactenergyshouldbe atleast40 ft-lb at a test temperature60”F belowtheminimumdesigntemperature. 3. Explosion13ul~eTest A fundamentalproblemis theevaluationof actualweldments whosecomplexitycannotbe simulatedin simplesmallspecimens.The explosionbulgetestis oneprocedurecurrentlyused,onalimitedscale, for thispurposeandfromwhicha considerableamountof informationis graduallybeingaccumulated. Someof thesedataareincludedin Tables11throughVI. Severalobservationshavebeenmadew-hichareimportantwithregard to theuseofthistestfor establishingtheperformanceof weldmentsin high-strength,low-alloysteels. Thetestdefinesthreetransitiontem- peraturesas describedbyNRLin Reference26. Thesetransitiontem- peraturesarenil ductilitytransitiontemperature(NDTT),fracture transitionelastic(FTE)andfracturetransitionplastic(FTP). Inferritic materials,theFTEis usually60”F higherthantheNDTT. Theobserva- tionhasbeenmadethatfor thequenchedandternpercdlow-alloysteels, theactualFTE andNDTTtemperaturesareoftenveryclosetogetherand nearlyidentical.Theobservationhasalsobeenmadethatinexplosion bulgetestingthesesteels, it is nearl,y impossibleto obtaina so-called “flatbreak”whichhasalsobeenusedas thedefinitionof NDTTtemperat- ure. It is believedthat,becauseof theveryhighyieldstrengthto tensile strengthratio,to forcea cracktopropagateoneneedsto exceedtheyield strength,eveninthehold-dnw-narea. Themostdesirableresultsare: (1)fracmrepathsthatdo notindicateseveredegradationofweldnlentmaterialswithrespectto as- receivedbaseplate;(2)greaterthan5~0plasticdeformationbefore fracture;and(3)FTPbelowoperatingtemperature.Thisbehavior cannotoftenbeobtainedin shipyardHSLAQ andT weldments. At thepresent time, the recommendation for weldrnent quality control is that the FTE, as definedbytheexplosionbulgetest, mustbebelowtheoperatingtemperature.Thistestdoesnotprovidea measureof fracturetoughnessintheHA.Z,butdefinesthelowerlimit of safeoperatingtemperatureaccordingto presentconcepts01fracture safedesign.Thistestmaybe replacedbythedynamicteartestbeing Table11. Geil~ral!UeldingProceduresandTestResultsforL1.S.SteelExplosionBulgeTestsonWelded Platesof,4517F Steel Bzse Metal WeldMe(ml Plate TII,ck.. P*eh.. Number.1 El.ctr.dc C!lrre.1 voltage, TravelSpeed Heat3nput Drq-},:e,ght C,,at -50T Cwat -50-F CvaCO-F, Cv at -50-F FTE ,. JO,,tDz,,s. Temp., t- I%s,cs TyT,e Dia., i.. R..:., arwps “oIts Rage, ipn Ra.Re, KJ/Im. NDT,’F [Lo.E.) ft-lb (Trar,s,)It-lb ft-lb [t-lb TSIIW,OF1 112 boos,.gle ,5 9 E11018G1/8Root, 125-170 21 6.1-13.0 lb,5-35.0 -70 29 23 52 37 -40 5132 1 60° Double 75 12 E11018G1/SRoot, 120-210 21 z. 8-8.5 25,8-56.2 -50 53 32 52 32 -30 5f3z, >{16 2 60° Double 200 44 X[1018G5/32, 170-210 Zi 3.2-8.6 32,0-70.0 -80 50 4; 70 54 . . i.. ~ BuIx.He,@It,m. Ikd.cmo”,% DiametricCr-ack,tm. 112 1 }.112 3-1j2 2 1-15{16 6-112 3 2-5/16 9-il.? 4 2-11{16 !3.1/2 5 3-1/.? 21 3-1[2 0 2-1/8 6-112 0 2.11/16 11 0 3-3116 17 9-314 2 1 .- Z.3J.3 1 2 . . 4 9-3!4 I-J 3 . . 6-3)4 =-J 15 { ~d!~~ ~~i~,, “aterial--ldentificatonandProPertesofP.rmcoSSS-1OO!I1OOPlates mechanicalPrope I ,s rtsilePI ,ertie 5 Impact$ U2!72s ChemiczLComposition Mat’1 ~hi.k. , ASTM Hca! HtT 0.270Y.S., T. S., % E1. I E208 ;“ a E FinalHeatAnaly~is, TO in. Grade k=i n 2 in. ~ c Mn P s si c, c. MO Ti B ~ No. Ch NO. ksi %R. A. NDT,“Y — . T A 1 A517-33 50627 P-26974 112.I 122.3 20.0 6?.9 -501 30 27 0.18 0.66 0.010 0.020 0.28 1.00 0.24 0.24 0.070 0.002 B l-3)4 A514-E 50826 P-2B507 Ii4.7 124.8 21.0 54.7 -50L 47 10 0.16 0.70 0.012 0,022 0.35 1.92 0.26 0.52 0.058 0.002 c 1-314 A517-E 50826 P-28504 109.0 118.7 21.0 64.3 L40 48 262 Sameas above D 1 A517-D +3862 P-53850 108.5 118.4 23.0 61.9 .50[ 48 30 O.16 0.54 0.0100.014 I 0.26 I 0.95 0.25 I 0.20 I 0.,075 I 0.002 P-53852 106.3 115.8 23,0 68.7 4 48 38 A517-D E 1 43062 P-53849 109.I 119.0 Zl, o 64.5 4 3 3 Same as above P-53851 105.8 116.8 22.0 68.D 4 3 3 \ F 1 A517-D 43862 P-53848 108.3 117.3 23,0 68.7 4 57 29 ‘. G h A517-D 52.902 P-52639 112.2 122.3 20.0 70.I -501 38 35 0.16 0.52 0.0100.006 0.25 0,92 0.28 0.21 0.070 0.002 H I-314 A517-3Z 43723 P-53569 )19.8 130.3 17.0 56.5 <.z04 40 31 0.16 0.58 0.013 0,010 0,28 1.73 0.23 0.50 0.061 0.002 J 1. A5i7-E 50576 P-64043 1)1.1 122.5 10.0 59.6 .701 33 22 0.13 0.62 0.012 0.020 0.34 1,89 0.23 0.42 0.066 0.002 K 1-3/4 A517-E 51519 P-36361 L18.9 126.0 20.0 68.0 .3~l 56 28 0.17 0.5a 0.010 0.012 0.28 1.82 0.24 0.52 0.062 0.002 L 1 A517-D 53592 P-64044 113.9 127-.5 19.5 66.9 -701 51 40 0.18 0.50 0.010 L0.016 0.28 0,96 0.26 0.23 0.091 0.002 1. P-2 Specimen. 2. -30” F”datz, NO tMS at -60” F. 3. Not obtained. 4. This NDT was determinedTimnnEqcdoaim Bulge Test. I TableIIIB. ExplosionTestslofArmcol-In.-ThickSSS-1OOAUnweldedBasePlate (MaterialCodeL - A517G!RD) Test Type Test Temp, Shot Fracture Test No. “F No. Results Characteristics Crack El o 1 Twolcracksinbulge O*FaboveFTE Starter region- 8 in.and12in. 1ong E4 -40 1 Fivepiecesblownfrom -40°Faboveh!DT center,twocracks throughtoplateedge I l-- E3 -80 1 Ninepiecesblownfrom -80°FisaboutNDT center,onecrack throughtoplateedge i3ulge2 E2 0 1 6flThinning l-%-in.Bulge 2 8%Thinning Nocracksinplate. 2-1/8-in.Bulge O“FisFTPof 3 12%Thinning unweldedplate. 2-5/8-in.Bulge 4 19.8%Tl~inning 3-1/8-in.Bulge 1. 7-lbpentoliteat15-in.standoff. 2. Thicknessreductionsexceedsminimumrequiredby100%onfirstshot. TableIV. bleldingProceduresforArmcoSSS-100A/100ExplosionTestPlates sample Welding Proccd Root P&s,es Filler )detalandt.r Grade code series ldent. Process Heat 3nput, Ilti. d Material Flux Dala A517-D ~ 2.3 SMAW 3b,000- 45,000 1f8 E11OI7-M 5/32in. E11018-M A 2 1,2,3 SAIZ; 33,500- 52,000 1/8 ox-loo wf709-5 1/8in, OX-1OOw/709-5 r),L, - G 4 D,E, G SA B,,, Plate Weld H.A.2 EKPIC.S,O”CrickSt&rL,, Test Rcsnlts Th,ck., ASTM ,4.,’, Te,, Sarnplc Weldl.gProcedureJ E-208 c., .$-600F Metal,c“ c,. FTE, Failw.e ,r,. Grad, Cod, Series Id.,]t. P,..,, s He., Jmput,J/,., NDT,OF L T O,F -50°F O~F -50-F OF Locahon CO-..1. 1 A547-D ,\ 1 2,3 Sh$AIW 36,00045,000 -502 30 27 61 35 57 45 -40 BM-T?JLI.HAZWeldzone tou~hness equal to base meta~ A 2 1,2,3 SAW 33.5G0 52,1J00 .502 30 27 45 35 58 32 +40 FusionZ.., Lowe,l t.ughne,sinhsim zone D .L D SAU 34,000-45.000.;02 1~ ,8 ~, 22 ~] Z* <0 BM-!,;W-HAZ )’/eldzonelough.,,, eq.al 10basem>elal L 4 E s,1i\r 34,000 45,000 .502 48 38 . . 34 . . 36 <-.20 BM-WM-HAZ Sameasz.bo:c G 4 G SAW 34,000 45,000 .502 j~ ~~ ~, Z6 .+~ ~~ -10 BM.WM-!+AZ Samea, ab.w A517.11 .1 5 B.,3 sj\\ir 42,500 52,500 .;.2 3J 22 4, . . q$ . . :0 BM-\VM-HAZsame❑s ab.w .4317-D 5> 5 .4-1,A-24 shw 22,500- 28,DOG .7~z >, q~ ,5 ~g 60 42 <0 Bh{-Wh[-HAZ Gooduni[orrc10ugl>ne,s. FTE belokvOar L 5 c-1 SAIW .2, 500. 52.,00 -702 51 40 56 2,0 42 -- 0 BM.WM-HAZ \,Weld. . . . ,oughnc,, cqua]m Las..metal A5L7.D/E L(J 5 ‘.25 5A\! 42,500- 5.?,00 .702 ~ce=~o,,e .- ]g -. . . +,0 E!M.WM.HAZ Lowerto.gbnessi. A517Eplateside .4517-D .% 3 1.4 GMA\V-FC 32,<,00. 48,000 .502 ~~ 27 44 ~B5 ~~ ~fls .40 BM-HAZ Weld.m.e wghne, , equal[. b.,. metal A 3 5-3 GATAW 34,!)00- 44,000 -502 30 27 44 345 51 245 -30 BM-HAZ %rnea, abaw 1-3/4 S.517-E c 2 T.a, 9 SMAw 26,WQ- .7,000 -.!0 48 26Y 54 39 3s 28 .10 BM-WM.HAZ Samea, abow c 2 4, 5,6 SAW 39,GO0 63,000 -40 46 269 44 36 36 26 +10 BM-Whl-HAZ Sameasabove H 4 B sAw 37,700 60.000 c.z07 40 31 37 z& L(, ~.5 -10 13M-WM.HAZ Sameasabove H 4 c 5.4!% 37.500. 60,000 <.Z07 ~~ j~ 32 295 52, 435 -10 BM-WM.HAZ Szrnc.S above iK 5 D1,D2,D4 ski? 42,300- 52,500 .3~2 56!. zOS 36 Zg so la 0 13M-WM-HAZ .3ameas above 1-3/4 A5i4.E B 1 5.q S>.5A1W 27,000- 39,000 .5~3 q, ,8 j~ 37 54 .. ,20 ~~[ Weldzoneku~l>ms,SUP,,,•, 1“PI.(c ,.. Frch Material den~itication Mat,1 Test sample WeldProcedure Test Shot Thinning, Code Series Ident. Temp, “F NO. % Ht, i~. ~ —— 1 A517-D A 1 ~A2 +3o 1 5 1-3/8 None 30”F aboveFTE andnear FTP 2 6 2-1/8 112-in. crack - toe of weld O°F HAZ 3 12 2-1/2 Extendt. 9 in. alongweld ) ~z SMAW 36,000-45,000 0 1 5.‘1 1-1/2 ,None O-F is at FTP oiHAZ, Weldand 2 8.2 2-1116 No”e Base Piale 3 11 Z-lfz Short.rack across weld 4 13 2-7/8 Crackdidnot increase D 4 D.B12 SAW 34,000-45,000 +40 I 5.8 1-9!16 None +40°F i, near FTP .1 F3AZ I 2 6.9 2-kt4 None 3 12.6 2-314 .%natltears m meldandat toe 4 18.4 3-518 Extendedalongtoe andBMin bulge L 5 Al -22 SAW 22,500- Z0,000 0 1 6.2 hron. O-Fis belmzFTP.fHAZ 2 9.1 Crack~ngat toe of~eld and thruholddm=min base I metal AZ-23 5Aw 22,500- 28,000 0 1 5.4 l-7t16 None O-F is FTP of HAZ, Weld and 2 7.4 2-3(16 None Base PIatc 3 10.8 2.5/8 None 4 17.6 3-lf8 None 5 C1-22 SAW 42,500- 52,500 0 ) 3.9 1-7f8 Extensivecrackingin HAZ I A5i7-DIE LIJ 5 C2-22 SAW 42,500- 52,500 0 1 3. L 1.3f4 Samea, above. Coniined oI--J I toA517-Dside oi weld t A 3 92 GkiAUr 34,000- 44,000 +3o 1 5.8 L-318 None +30°F is at FTP of HAZ, 2 ?. 8 1-15/16 None WeldandBee Pia& 3 10.2 2-7f16 Smll crackin weld L 4 16.0 2-13/16 NOextensionOicrack 1. 7-lbDentoltteat 15-in.standolilor l-in. plate. 2, As-weldedconditionv,ith\veldbeadreinforcementin place. 3. Weldreinforcementremovedby grinding. Table!ITR.!?esultsofExplosionBulgeTestsofArmcoSSS-1OOMelcirnents Material Descripc E. lesion Bul~eTest Resultsl Thick. , ASTM MaLmI sarnp~e WeldProcedure Test S!lot Thinning, Bnlge Fracture I 1 Res(Llts Ident. Process I HeatInput,J/in. Ternp, “!? NO. % Ht. in. Characteristic I I I I C-B12 SAW 37,500- 60,000 +40 1 2 Crackingin weld zndplate in bulge D2-22 sAW 42,500- 52,500 o 1 2 D4-22 SAW Sameas above 0 1 2 Crackkrgin weld, HAZ andplate 42 SAW 27,000- 39,000 +60 1 M 2 ~ 1. 28-lb=enmtiteat i7-in. standoff. 2. As-weldedmnditim %.,ith.vcldbeadzeinforcementin place. -21. developedatNRLwhichshowsconsiderablepromisefor definingdynamic fracturetoughnessvaluesinadditiontotransitiontemperatures. Thebasicobjectiveof explosionbulgetestsis to demon- stratethattheweldmentwillnotpropagatefastfractureatelasticstress levels. As previouslyindicated,thissuppositionis notnecessarily truefor Q andT materialsandtheotherdatapresentedindicatethat it is nota sufficienttestto determinelikelihoodof fastfractureatless thanyieldstrengthstressloadinginthepresenceof reasonablesize flaws. It is a usefultestfor determiningthezoneof lowestfractur~ toughnessandprovidingfractureappearancecriteriafor interpretation. E. FatigueandCorrosionFatigue Theconventional(smooth,polished,flawfree)fatiguespecimen testsdisplayfatiguestrengthsthatincreasemonotonicallywithincrease intensilestrength.As-rolledsurfacesandthepresenceofmechanical andmetallurgicaldiscontinuities,suchasmightbepresentinaweld- ment,cansignificantlydegradethefatiguestrengthof constructional steels, Figure4.(31) Figure5 depictssmallspecimenA517F datawhichfurther demonstratetheeffectsof surfacediscontinuitiesonfatiguestrength. Thestressconcentrationfactorforthesediscontinuitiesis low, relative tothatfor manykindsof fabricationflawswhichcouldoccurinHSLA Q andT materials. Thesmallspecimensize limitscrackpropagation lifeto sucha degreethatthesedatacanbe consideredas crackinitiation life for thematerialandindicateddiscontinuityina largestructure. Figure6 alsoshowsthedegradationof fatiguelife of baseplatemate- rial as a functionof materialstrength,butona normalizedloadintensity basis. Figure7 depictsa comparisonof initiationandpropagation fatiguelivesfor HY-80baseplatematerialinair andsaltwater. Figure8 showstheeffectof a 3. 5’%saltwaterenvironmentonthefatigue crackgrowthrateinA!3171?material. Thesetrends,togetherwith higherdesignstresses, indicatethatHSLAQ andT shipstructural elementsmayhaveconsiderablyshorterfatiguelivesthancarbonsteel elements. However,if attentionis givento designdetailsandfabrica- tionqualitycontrol,a structurewithadequatefatiguestrengthcanbe fabricated. l?. EnvironmentalEffects 1. Corrosion ThecorrosionresistanceofunstressedHSLAQ andT base platematerialsexposedto marineenvironmentsappearsto be equalor superiortothatof carbonsteelmaterials.(32) Steelswithveryhigh -22- 80 / ExpectedFatigue Str~ngth,AtR=O WithGroundamdPolishedScrfaces 70 / 60 / / 50 Fig.4. AverageFatigue / ~ pl~i~~pl~~~ Strenqthsof 40 Constructional Steelsat2,000,000 Cyclesata Stress 30 RatioofO.31 20 Trarisvcrs?lyButl-WeldedPlate 10 1 0 20 40 60 80 100 120 140 TENSILESTRENGTH,ksi >WeldRcmfjveci AndPolished ❑ 100-GriLDisc.Scratches 7 As-Received Plate Perpendicularto Principal Stress Axis kk.\ ,+ -’-+ Axis . ●W”eldReinforcement Intact-T.Icight1/16Inch ~st’e’’’xi’ 00 A W?ld Partially Ground Down-Heightlf64 Inch ,1 lu- lU lU FATIGUE LIFE, cycles Fig. 5. EffectofRemovalofWeldReinforcementonAxial-Load FatigueStrengthofTransverselyButt-Weldedl/4-in- ThickConstructionalAlloySteelPlates(R= -1)19 -23- ,000 100Q I I I I I I I 1 I I I I 1 I I I ‘1 PlateBendFatigueTest 1I A302BSteel Full-ReverseStrain I (YieldStrength Cycle I 58ksi) Air Environment I I / / I :/ II// A51(“7FSteel 100 :+w~-m+h 1! /’ %+ 10,000 (Yields..G..& L,. “1 107 ksi)~, / , II II / ~ I I I i ‘/~A201B steel //’!(YieldStrength 1)f1 I 48 ksi) i 10 I’,/ / w 00,000 I I/’ / /’ / INOTE: I ProportionalLimitStrain I, Rangeis Definedas 500 I Microinches/InchPlastic 1 StrainRan~e I I PlasticStrainRange I 1.,0 I I 1 I # ! I I I I I 1 I I 1 ( , 000,000 0,1 0.2 0.4 0.6 1.0 2.0 4.0 6.0 10 RATIOOF TOTALSTRAINRANGETOPROPORTIONALLIMITSTRAINRANC;T; Fig.6. AirEnvironmentLowCycleFatigueCrackPropagation~h~~acteristics ofA201B,A302BandA517FSteelsona h!ormalizedLoad lntensit.y Basis ..— -24. I I 0,04 InitiationCurve-Air (USSData) I I 0.02 ~rop~gationGurve-Air (NRI.,Data) 0.01 0.00? Elastic o.OOE InitiationGurve - 3.570 0.004 (USSD:,ta) PrOpa~atiOnCurve - 3.570Salt Water 0.002 0.001 Number of Cvclcs to Failure Fig.7. Log-LogPlotofTotalStrainRangeVersusCyclestoFailureForHY-80 Steels,TheCurvesIndicateFailurebvInitiationandFailurebv Propagation(ISFL)inBothAirand3.5%SaltWaterEnvironments“p 000 Fig.8. Log-LogPlotofFatigue [CrackGrowthRateVS. TotalStrainRangefor A517FSteelina 3.5% SaltMaterEnvironment (Full-R;~erseStrain Cycle) 0,000 00,000 ,000,000 1000 10,000 100,000 Total StrainRange(Microinchcs/Inch) -25- strengths(or ofhighhardness)maybe susceptibleto corrosiveenviron- mentsotherthanhydrogensulfide. Thechlorideionmaybe detrimental or beneficialto corrosionresistance. 2. StressCorrosionandHydrogenEmbrittlement U. S. SteelCorporationtests(33)showedthata marine atmosphereenvironmentwasmoreseverethanseawaterandsemi- industrialenvironmentsonthestress-corrosionpropertiesofunwelded stressedsteelspecimens. Thesesteelsrepresenteda rangeof strength levelsproducedbyvariationsinchemistryandheattreatment.The resultsindicatedthatsusceptibilityto specimendelayedfailures(from stresscorrosioncrackingor hydrogenembrittlement)inmarineenviron- mentscanoccurinsteelshavingyieldstrengthsas lowas 175,000psi. SincehardnesstraversestakenacressA514/A517 weldmentsindicate thatultimatetensilestrengthlevelsinexcessof 175,000psi arepossible intheHAZ, it appearslikelythatmarineenvironmentscanbe expected to inducecrackinitiationandS1OWcrackgrowthinthesematerials, IthasalsobeendemonstratedthatH2S, inconcentrations as lowas 100ppm,inducesdelayedfailurein HSLAQ andT HAZmate- rials stressedto less thanyieldstrengthvalues.(35) It is generally thoughtthatthemechanisminvolvedis hydrogenembrittlement.This is a particularlysevereenvironmentandnocorrelationhasbeen developedbetweenbehaviorinthisenvironmentandfailurein specimens exposedto otherenvironments.(24) v. THECONTRIBIJTIONOFVARIOUSFAILUREMECHANISMS TOCRACKINITIATION,CRACKGROWTH,AND TERMINALFAILURE A. FlawNatureandGrowth 1. Background Theevidenceis thata structuralcrackwill initiatesooner andgrowfasterinHSLAQ andT structuralelementsthantheywillin comparablecarbonsteelstructuralelementssubjectedto thesame structuralloadingsovera periodoftime. Thissituationarises becauseof theincreasedlikelihoodof sharpflawsearlyintheservice life, higherresidualandimposedstresses, andenvironmentalsensitivity, TheHSLAQ andT steelstructuralelementweldmentsare morelikelyto havefabricationflawsanddefectsthanthoseof carbonsteel builtandinspectedtothesamestandards.Theprimaryconcernis weld- mentcracking. Unlessadequatecontrolsareapplied,delayedcracking canoccuraftertheweldmenthasbeensubjectedtonondestructivetests, Nonmetallicinclusionsandlaminationscontributetotheformationof buriedflawswithorientationsunfavorablefor detectionbyradiography. -26- Thestressconcentrationfactorof notchesincarbonsteels mayoftenbe reducedbyoccasionalhighserviceloads(referredto as “shakedown”).HSLAQ andT steels, becauseof ahighratioof yield to ultimatestrength,resistthebluntingof a notchso thatsharpflaws inregionsof yieldstressloadingmaypersistduringtheshipservice life. 2. InitiationandPropagationbyFatigue Experiencehasdemonstratedthatcrackinitiationandgrowth byfatigueis a likelyoccurrencein shipstructuresandthatthemost likelylocationsareatdiscontinuitieswhichprovidepointsof stress concentration.Thegreaterlikelihoodof havingcracklikeflawsinHSLA Q andT weldmentsincreasesthepossibilityofhavingsitesfor fatigue crackinitiation. Lowcyclefatiguehasbeenconsideredto betheonlysignif- icantsourceof crackgrowthbyfatigueincarbonsteelshipstructural elementsbecause,inmaterialswithsmallratiosof yieldto ultimate tensilestrengths,occasionalhighloadings“wipeout’’hightensileresidual stressesto providethefavorablecaseof meanstressequalto zero. Thisis notthecasefortheI-ISLAQ andT steelsusedin shipconstruc- tion. Theextremelyhighresidualtensilestressthatcanbemaintained inHSLAQ andT weldmentsrequiresthathighcyclefatiguecrackgrowth underconditionsof highmeanstressbe consideredinadditionto low cyclefatigue. Fatiguecrackinitiationlife is shorterinthepresenceof notchesandfatiguecrackpropagationrateis higher,ona normalized stressbasis(consideringpeakservicestressesto belinearlyrelatedto materialyieldstrength),for HSLAQ andT baseplatematerialsthan for carbonsteelmaterials.Thistrendcanbe expectedto be accentuated inhighhardness,high-strengthHAZmaterial.(34>35) 3. EnvironmentalEffects Slowcrackgrowth,bymechanismssuchas stress corrosion cracking,hydro,qenembrittlement,or theotherpost-datedenvironmen- tallyaffectedmechanismsmustbe consideredas possibleinHSLA Q and‘THAZmaterialsuntilinvestigationdemonstratesotherwise,The onlyevidenceavailableas to thelikelihoodthatthismechanismof crack growthcancontributeto failureis measuredhardnessof HAZmaterials andtheexperiencethatmanymaterialsofthesehardnesslevelsare sensitive”tothecombinationof sharpflaws,highstresses, andaqueous environments.(36!37) A517F materialshavebeenobservedto develop corrosionpitsinregionsof highstrainandthesegeometricdiscon- tinuitieshavebeenobservedtobethesiteof fatiguecrackinitiation.(31) Crackinitiationandslowcrackgrowthbyhydrogenembrittle- m(:r]tis particularlyinsidiousbecauseit is moredifficultto protect ;l.,~;.liflS~ bycoatin~andcathodicprotection.Thefollowingmechanisms -27. arealsosuspectedof contributingto slowcrackgrowthinmarineatmo- spheresor seawaterenvironments: . Corrosionpitting . Stresscorrosion Crackloadingbywedgingof corrosionproducts. Stresscorrosionis a problemnotencounteredincarbon steelmaterialsandis, as yet, onlysuspectinHSLAQ andT materials becausethereis nodefinitiveevidencethattheproblemdoesexist. It shouldbe emphasizedthatcrackinitiationandgrowthbehaviorof this typeinvolvetheinteractionof a complexset ofvariables,including stressmagnitudesanddistributions,flawanddefectcharacter,and metallurgicalvariationsthatcannotbe developedinsmall, simple specimens.Also, theattainmentof a particularlydeleteriousset of conditionsinaweldmentmustbe regardedas a statisticaloccurrence relatedto samplesizewhichis morelikelyto occurina shipthanin a laboratoryspecimen. B. TerminalFailure Thefailureof a structuralelementmayor maynotendangerthe structuredependingonthestructuralfunctionoftheelement,structural redundancy,andloadcharacteristics.Thecurrentusageof FISLA Q andT materialsin shipstructuresis suchthatfailureofthese elementswouldlikelyresultin seriousstructuraldamageif nothull ‘ failure.Thetwotypesof failurethatcanbeenvisionedareweakening ofthehullgirderso thatit cannotwithstandserviceloadsor introducing a fastrunningcrackintothecarbonsteelmaterialthatwouldnotbe arrestedbythatmaterial. Structuralelementfailure(otherthanexcessivedeformationor compressioninstability)canbe classifiedas: Tensilefailureinresponseto unforeseenoverload.or to service damagethatreducesthecross-sectionalarea requiredto carryappliedserviceloads . Fastfractureor unstablecrackpropagation. TensilefailureanalysiscriteriaarethesameforbothcarbonandI-ISLA Q andT steels, butfastfractureanalysiscriteriaaredifferent.In general,thetransitiontemperatureapproachis adequatetopredictthe fastfracturecharacteristicsof carbonsteels, butfracturemechanics criteriamustbe consideredinthecaseof HSLAQ andT materials. Thismaybe explainedbyreferenceto Figure9, whichdepicts fracturetoughnessconceptsfor steelsonthebasisof a normalized -28- transitiontemperature.Qualitatively,carbonsteelsfit thetoughsteel categoryandI-ISLAQ andT baseplatematerialare inthelow-toughness steelcategory. However,HSLAQ andT HAZmaterialcanbe inthe high-strength,brittlealloycategorywhichdoesnotexhibita transition fromlowto highfractureenergy. Inthisdiagram,theeffectsof size, rateof loading,etc., areneglectedbutcanbe consideredas accounted Iorbynormalizationoftransitiontemperatureandfractureenergy. Considering(1)thatEnergyavailablefor lastfracturecrack propagationincreaseswithmaterialstrengthlevelbecauseofhigher designstresses, (2)thatlaboratorytest resultscannotbe correlated directlywithservicebehaviorexceptformaterialsandtest specimens analyzablebyfracturemechanics,and(3)thatthedifferentlaboratory testprocedureresultsdonotcorrelate,it is obviousthatthelikelihood of fastfractureof similarstructuresmadeof differentmaterialscannot be easilydevelopedintoa formsuchas is depictedbyFigure9. I-Iow- ever, theNavalResearchLaboratory~as accomplishedthedevelop- mentof a methodfor fastfracturecorrelationanalysisthatis suitable for use, as describedbelow.(26) Carbonsteelfastfracturepropertiescanbe characterizedby theNDTTindexedFractureAnalysisDiagramas depictedbyFigure10(a), inwhichcorrelationwasdevelopedfromserviceexperience.The establishingof FTE at60°F andFTP at 120°F aboveNDTTis con- servativesincemanysteelshavemuchless thanthistemperaturedif- ferencebetweentheindexpoints. SinceNDTTmayactuallybelocated atanypointontheCharpyV-notchimpacttransitio~curvefor steels, thecrackarrestcurvecannotbe derivedreliablyfromCharpyV-notch impacttestresults. OncecorrelationbetweenCvpropertiesand NDTTis established,however,theCharpyV-notchtestdataaresuf- ficientfor fractureanalysisfor carbonsteelshiphullmaterialswhere baseplatefracturetoughnessis less thanweldmentmaterialtoughness. Thefirst problemencounteredintheuse oftheFractureAnalysis Diagramprocedurewasin its applicationto HSLAQ andT materialsin whichtheweldmentHAZductilefractureenergywasless thanthebase platebrittlefractureenergyas depictedbyFigure10(b), andlast fracturewasobservedto occuratless thanyieldstrengthstressand higherthanI?TEtemperatureconditionsestablishedforthebasemater- ial. Inthiscase, thefractureanalysisdiagrampro>-idesanupper boundfor predictionof fastfracturebehavioroflowtoughnesssteel, suchas theHSLAQ andT materialsof interest. Thisis useful,but notsufficientfor analysis. Theotheravailablequantitativeapproachto theproblemis the fracturemechanicsprocedurefor high-strength,brittlealloysor mate- rialsloadedbelowNDTT.(38-46) Figure11andTableVIIdepictthe specimenusedanddataobtainedwiththisprocedureforHSLAQ andT materials. Theas-quenchedconditionwashypothesizedforHSLAQ andT propertiesof I-IAZmaterial,andthemeasuredhardnessvaluestendto supportthisthesisalthoughthematerialwasnotsubjectedto as much -29- “3!)” Tensile -.— ~--- ~-.------=_--- - 9- F Stress InitiationCurves M“H4 .@ ——FTP (FractureStresses,, #-O ,>< ,O,=..~--~~–-- I?orSpectrum01,/ / /y ,’ / —-— / /’ FlawSizes) ,i / / ,~ _-–=lastic / //–– Loads / / --”= ~ Yield – ------Sma11Flaw-— ~,<~ - 7/~ - –,1- -- ncreasin / -3?TE~ Stress Elastic [ .----:’ ::::? /~’” /’” /“-=--= Loads ; 3/4Y.s. / /~ FracturesDoNot / / _- Q / / -- D Propagate 12” / / / --- .—-.. - - --- / ,/ _:- (TernperatureLimitation) l“ 211 j’ -–l\ CatCurve ,/ .--– 1/4Yes.---- b ——-- _1~/ --— I ll!llll llll~tll, ,1,!lllt! v,111111!l!! 1111 - o I I 1 i I I I I I I I 1 I NDT NDT+30”F NDT+60”F NDT-!-120”F Temperature a. Generalizedfractureanalysisdiagram,as referencedbytheNDTtemperature HighEnergy FullSh~ar I T-A..\T-L-..,-7 Fracture u. T. Y.s. / //L1’LL ~Fracture StressFor /4Y.s [ncreasing / 12Y. ‘z’ 114Y. S‘t~y~*T.11 ~+f~~~~FullShear t~ ...... ~.,,,!l” I Fractures‘aterial NDT NDT+60DF NDT+120”F Temperature b, Featuresoffractureanalysisdiagrammodificationsfor steelsof “lowenergytear”characteristics Fig.10. FractureAnalysisDiagramsfromW.$.PelliniandP.P.Puzak26 .31. TableVII.FractureToughnessDataforASTMA517FSteel Net Gross Fracture E.tre8s Relative Plastic Fracturo Stress crack eection, section, tough. inteaeity plate zone tough- intewity Thick- Width, length, Fr Str, Fr Str, neas, factor, thicknessapprOxr ness, factor, Shear c, param- c, GCI,in. lip, Temp, ness, L, ~o;~’ ,i lo;: ,i Cc, i-. Kc. Kci. Spcch-r.en “F t, in. _—*. in. lh/iq2 psi As-quenchedcondition TI-3 QTQ -200 0.9(I1 4.418 1.137 68.8 35.2 2q9 79,000 4,90 0,03 Z2Z 81,500 T1-15QTQ o 0.900 4.424 1!150 90.2 45.3 353 103.000 2.50 0,06 384 107,000 : T1-1QTQ RT 0.905 4.302 0.893 104.6 60.8 456 117,000 1.80 0.08 455 1!7,000 40 T1-12QTQ 300 0.913 5,040 1.314 81.4 40.2 317 97,50Q 2,60 0.06 342 101,000 40 T1-10QTQ 600 0.903 4.017 1.o32 79.1 39.7 241 85,000 2.99 0.06 241 85,000 35 711 t- Grippingand AlignmentHOleo 0° 0 0 0 ‘O” SawCut 181’ 1,, Crack Notch 5,, ‘‘“ rLengthIICII idth,,L1l Oo 1,,Thick Q(jO ‘0° L *? / d GmneralGonfi~ura$i.ynOfcrack. NotchTermilcSpecimen HEATTREATMENTOFSTEELU$EDINBENGH-kU@KT325TPROGRAM Grain Size, Hardness, steel COndition Heat Treatment ASTM Rc 517Fl-in. Plate Aa-quonctid Held1hrfin.ofthicknessat1650-FandVIaker quenched. 9 42 Quwwhad&tempered Held1br/in.ofthicknessat1650- 1700*Fandwater (+Y.upplier) quenched.Thefitcmperedat1150- 1250-F,h~ld. 1hrfin. ofthicknensandwaterquenched, 9 28 Annealed He~d1hriin.ofth$ckn$esat 1650-Fandthenfm.rmce coolad (3~F/hr) to 1000-F. Than air cooled to roomtemperature. 9 12.5 Fig,11. FractureToughnessDataforAS-M A517FStee24 -32- plasticdeformationas hadtheHAZmaterial. Thedatafortheas- quenchedconditionaredepictedbyFigure12(a)whereit canbe noted thatthespecimenwasnotof adequatesize tomeasurefracturemechanics planestrainfracturetoughnessmuchaboveO°F, Figure12(b)depicts thecorrelationobtainedbytheinvestigatorsbetweenfracturetoughness valuesandCharpyV-notchimpactenergywhichis usefulbecauseit enablesuseofthebulkofthefracturetoughnessdataavailable. Figure12(c)presentsthetheoreticalrelationshipbetweencracklength, stresslevel, and“fra,cturemechanics”fracturetoughnessforthe uniaxialtensilecase. It shouldbenotedthat, at about30”F, themate- rial of Figure12(a)wouldbe expectedto fractureatone-halfyield strengthstressif a throughcrackof 2 in. inlengthwerepresent. Sub- sequentwork,usinga moresophisticatedspecimen,hasresultedin obtainingplanestrainfracturetoughnessvaluesfor A517F baseplate materialatroomtemperatureandcorrelationbetweenthesevaluesand CharpyV-notchimpactvalues. Thesevaluesareconsistentwiththe valuesof Figures11and12attemperaturesbelowO“Fwherethespeci- mensizewasadequate.Thefracturemechanicsapproachprovidesa lowerboundfor predictionof fastfracturebehaviorof lowtoughness steelandappears‘cobe sufficientfor analysis,especiallyintheweld- mentFiAZwhichis certainlyless toughthanbaseplatematerial. TheA517F pointontheFigure13 correlationcurvecorresponds tobaseplatematerialwitha yieldstrengthof 110ksi, KICof 170ksi ~. anda CharpyV-notchimpactenergyvalueattesttemperatureof 62 ft-lb. Thisis roughlyequivalentto statingthata 2-ft-longthroughcrackin strengthdeckplatingloadedto one-halfyieldcouldinitiatefastfracture inthismaterial,if thematerialis thickenoughto developplanestrain crackloadingconditions.I?orthecaseof a materialwitha yieldstrength of 120ksi, CharpyV-notchimpactenergyvalueof 30 ft-lb, Figure13 indicatesa KICof 110ksi K. whichis equivalentto a criticalthrough cracklengthatone-halfyieldstrengthof about8 inches. Similarly,the simulatedHAZmaterialof Figure11wouldhavecriticalthroughcrack lengthas lowas 2 in. for one-halfyieldstrengthstressloadingat30”F as waspreviouslyindicatedbyotherwork, Figure14depictsa carbonsteelpressurevesselwhosebehavior is analyzablebythetransitiontemperatureapproach,andFigure15, its behaviorinrelationshipto theNRLfractureanalysisdiagram. Figure16depictsanA517F pressurevesselwhosebehavioris notanalyzablebythetransitiontemperatureapproach.Thisvessel failedfroma smallflawat a nominalstressless thanone-halfofthe yieldstress. Thisvesselwasstressrelieved. It is interestingto note thatthefailureapparentlydidnotinitiateatthelargestflaws,which werefatiguecracks. Ithasbeennotedinfracturetoughnessteststhat suchbehaviorapparentlyresultsfromcompressiveresidualstress at cracktipsderivedfromplasticloadingatfatiguecracktipswhichresults inapparentlyhighfracturetoughnessvalues. Thisfailureis oneof several.I-ISLAQ andT pressurevesseltestresultsthatfit thecorrelation fracturemechanicsprediction. -33- UJ Tempcratul+e,“F a. Effectoftemperatureonfracturetou~hness parameters for A517,GradeF steel o 0 0 0 000 00 0 0 /0 o Plateofinfinitewidthwithinternal crackoflength2Cor semi–infinite platewithedgecrac- 0 de~thC. t f —~l-—L——L— 0.01 0.1 1.0 J10.0 20 40 60 80 100 120 140 Energy,CharpyImpactTest,ft-lbs CrackLength(C), inches b. Gorrclation of ~n ] ~racture toughness c. Relationshipoffracturestrength withCharpyimp~ctenergyforbench- to cracklengthfordifferentlevels marksteels. offracturetoughness Fig.12. FractureToughnessofA517,GradeF SteelandSummary ofFractureMechanicsProcedures‘q —— -34- TestsConductedat+80”F VIM- Vacuum-Melted AM - Air-Melted 3,[ . HY-130(T)., AM- / 0A517-F (AM) 2.( o 12NiVM 12NiVM 1.[ / n 18Ni(180)VM (@47 ~M ‘ ‘ 12NiAM ~oP 4130AM /.>18 Ni (180)AM ., c 1 I I I I I I o 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Cv Energy/YieldStrength,ft lblksi Fig.13. RelationBetweenPlane-StrainStress-Intensity Factor,KIC,andCharpyV-NotchEnergyAbsorption (CVN) -35- . + ,-+ L v) m >m Lal . -36- FIeavy O.477’0Strain (PlasticStress At Nozzle) “’~m=”ShellStress 30 0/ .+ ------/ 2 ~ 20 m : 10 G _[J”q DT Failure ShellNozzle ‘ ‘ Temperature 01 I I 1 I 1 I I o 20 40 60 80 100 Temperature,OF Composition,wt-% Material c Mn Si P s A201Shell 0.18 0.65 0.21 0.010 O.024 A105Nozzle 0,25 0.72 0.22 0.007 0.034 Yield Tensile Reduction Strength, Strength,Elongation, ofArea, ksi ksi % 70 A201Shell 48.0 67.9 40,0 54.6 A105Nozzle 36.4 66,6 34.4 50.5 NDT,‘F CVNDT,ft-lb FT, ‘F CvFt,ft-lb A201Shell o 26 60/70 63/72 A105NOZZ~E! 10 13 60/70 25/30 Fig.15. FractureAnalysisRelatingtoFailureofPVRCVessel No.1,WhichOriginatedfroma 6-inchFatiqueCrack ina ForgedASTMA105Nozzle11 — -37- C D (a) Afterbrittlefracturetestat30”F and 5200 psi (b) Arc strike which initiated brittle fracture (c)FatiguecrackidjacenttoNozzleNo. 9 (d) Fatiguecrackinshellwhichleakedat48,772 cyclesand 4400psipeakinternalpressure Fiq.16. TerminalFailureofVesselNo.6 l] -38- Directapplicationofthedataobtainedto datehasbeendifficult becausetestmachineloadcapabilitieshavelimitedspecimensize. This inturncanproduceinvalidfracturetoughnessdataanddoesnotpermit anevaluationof a complexweldjointintermsof mechanicalproperties, residualstresses, andgeometricdiscontinuitiesthatcanonlybe studiedwithlarge-sizedspecimens. VI.CONCLUSIONS Thesedataindicatethat: (1) Fast fractureis possibleinweldmentsfabricatedof HSLA Q andT materialsatnominalstresslevelsless thanone- halfoftheyieldstressfromcracksof smallsize relative to shiphulldirnensions. (2) Fastfractureof manyof theHSLAQ andT materialswhich arebeingusedinshiphullconstructionshouldbepredictable bythefracturemechanicsapproach. (3) Thereis a generallackof quantitativedatarequiredto pre- dictcracksize as a functionof servicehistoryandloads correspondingto potentialfastfractureinitiation.This informationis basictotheestablishmentof serviceability criteriafortheHSLAQ andT steelsbeingusedinmerchant shiphullconstruction.Theseserviceabilitycriteriainclude qualitycontrol,inspection,andsurveillancespecifications andstandards. (4) A crackor flowcangrowto criticalsizeunderthecombined influenceof servicestressesandenvironmentalconditions. VII. RECOMMENDATIONS It is recommendedthatthefollowinglaboratoryinvestigationsbe performedto obtaintheessentialdatarequiredto establishtheservice- abilitycriteriafor HSLAQ andT weldments: (1) Studytheenvironmentaleffectsonspecimenssubjectedto highstatictensilestressesto determineif mechanisms suchas stresscorrosioncrackingandhydrogenembrittlement causeslowcrackgrowth. (2) Determinethec~ackinitiationandgrowthresponseto cyclic stressesina marineenvironment, (3) Establishthefracturetoughnessof FfAZmaterialsin quantitativetermsusingfracture~mechanicstestprocedures. -39. (4) Testcomplexspecimens(whichincludethevariouseffects of residualstress, cracklikeflaws, andgeometricand metallurgicaldiscontinuitiesIouridinrealhardwareweld- rnents)todeterminetherelationshipbetweenspecimentests andhardwarebehavior. BIBLIOG,RAPHY 1. Buchanan,G., “TheApplicationof HigherTensileSteelin MerchantShipConstruction,‘[ R.I.N.A. PaperNo. 1, March21, 1967, Meeting. 2. Cla~k,E. E. , “HighYieldShipSteels,“ NorthEastCoastInsti- tutionof EngineersandShipbuilders,Newcastle-Upon-Tyne, Transactions,July1967. 3. Kullberg,Gurmar,“ApplicationofHigher-TensileSteelsinShip Construction,“ presentedatSSCMeeting,August16, 1967. 4. Doty,W. D., “PropertiesandCharacteristicsof a Quenchedand TemperedSteelfor PressureVessels,“ TheWeldingJournal, ResearchSupplement,September1955. 5. Doty,W. D. , “Weldingof QuenchedandTemperedSteels,“ TheWeldingJournal,ResearchSupplement,pp289-s - 309-s, July1965. 6. Kampschaefer,G. E. , Jr,, Bruner,J. P. , andHavens,F. E- , “EngineeringDatafortheDesignandFabricationof Offshore DrillingPlatformswithHeat-TreatedSteels,“ ASMEPaper65- PET-25. 7. “PropertiesandSelectionof Metals,“ MetalsHandbook, Volume1, 8thEdition,1961. 8. Langer,B. F. , “PVRCInterpretiveReportofPressureVessel Research,Section1 - DesignConsiderations,“ WRCBulletin95, April1964. 9. Gross, J. H., “PVRCInterpretiveReportof PressureVessel Research,Section2 - MaterialsConsiderations,“ WRC13ulle- tin 101, November1964. 10. Pickett,A. G. andGrigory,S. C. , “Predictionof theLOW CycleFatigueLifeof PressureVessels,“ ASMEPaper67- MET-3. 11. Pickett,A. G. andGrigory,S. C. , “PredictionoftheTerminal- FailureBehaviorof PressureVessels,“ ASMEPaper67- MET-2. .40- 12. Jolmson,R. E., “FractureMechanics:A Basisfor Brittle FracturePrevention,“ November1965, WAPD-TM-505. 13. Gurney,T. R. , “FatigueTestsonButtandFilletWeldedJoints inMildandHighTensileStructuralSteels,“ BWRAReport D7/6/60. 14. Week,R., “A RationalApproachto Standardsfor WeldedCon- struction,“ BritishWeldingJournal,pp658-668, November1966. 15. Heller, S. R. Jr., Fioriti, 1., andVasta, J. , “AnEvaluationof 14Y-80Steelas a StructuralMaterialfor Submarines,‘rNaval EngineersJournal,FebruaryandApril1965. 16. “Quenched-and-TemperedAlloy-SteelPlates,“ ClimaxMolybdenum, 1962. 17. EIull WeldingManual,AWSD3. 5-62. 18. Crum, F. J. , “TheUseof Higher-StrengthSteelsinShipCon- struction,“ NewYorkSocietyof MarinePortEngineers,Meeting, January19, 1966. 19. Kline,R. G., “Applicationof HigherStrengthSteelstoGreat LakesVessels,“ MarineTechnology,pp273-287, July1966. 20. “GuidefortheSelectionof HighStrengthandAlloySteels,“ Pre- liminaryDraft, 1967Revision,SNAMETechnicalandResearch BulletinNo. 2-11. 21. “Rulesfor BuildingandClassingSteelVessels,“ ABS1965. 22. “DesignandConstructionof SteelMerchantShips,“ DavidArnott, Editor,SNAME,1955. 23. Stern,1. L. andQuattrone,R. , “A MultipleTestApproach‘co thePredictionof WeldrnentCracking,“ TheWeldin~Journal, ResearchSupplement,pp203-s - 216-s, May1967. 24. Lange,E. A. , Pickett,A. G., andWylie, R. , “Failure Analysisof PVRCVesselNo. 5, PartI-A Studyof Materials PropertiesandFractureDevelopment,“ WRC13ulletinNo. 98, August1964. 25. Wessel, E. T. andHays, L. E., “FractureCharacteristicsof SomeHigh-Strength,Weldable,StructuralSteels,“ TheWelding Journal,ResearchSupplement,pp512-s - 528-s, November1963. 26. Pellini,et al. , “Reviewof ConceptsandStatusof Procedures for Fracture-SafeDesignof ComplexWeldedStructuresInvolving Metalsof Lowto Ultra-HighStrengthLevels,“ NRLReport6300, —- _4]- June1965. 27. Kihara,H., Kanazawa,T. , andIkeda,K. , “13rittleFracture Characteristics01WeldedJoint,“ March1967. 28. Vasta, J. andPalmero,P. M. , “AnEngineeringApproachto Low-CycleFatigueof ShipStructures,“ SNAMEAnnualMeeting, No. 14, 1965. 29. Rolfe, S. T. andGensarner,M. , “Fi-acture-ToughnessRequire- mentsforSteels,“ AppliedResearchLaboratory,U. S. Steel TechnicalReportProjectNo. 89.018-020(2). 30. Pellini, W. S., “AdvancesinFractureToughnessCharacteriza- tionProceduresandinQuantitativeInterpretationsto Fracture- SafeDesignforStructuralSteels,“ NRLReport6713. 31. Scott,G. R. , Stallyemer,J. E. , andMunse,W. II., “Fatigue Strengthof TransverseButt-WeldedJointsinN-A-XTRA100 Steel,“ Universityof IllinoisReport,February1963. 32. Brown, B. F. and Bir~baum, L. S., “CorrosionControlfor StructuralMetalsintheMarineEnvironment,“ NRLReport6167, pp222-230. 33. Phelps,E. H., “Stress-CorrosionBehaviorof High-Yield- StrengthSteels,“ PanelDiscussionNo. 27, “Problems,Preven- tion, andTheoriesof Corrosion,“ SeventhWorldPetroleum Congress,MexicoCity, April2-8, 1967. 34. Crooker,T. W. andLange,E. A. , “Comparisonof LowCycle FatigueTestResults- InitiationversusPropagationFailure Criteria,“ NRLReport6454, pp81-88, April1966. 35. Crooker,T. W. andLange,E. A. , “LowCycleFatigueCrack PropagationinA201B,A30213,andA517FPressureVessel Steels,“ TheWeldingJournal,ResearchSupplement,pp322-s - 328-s, July 1967. 36. Crooker,T. W. andLange,E. A. , “Corrosion-FatigueCrack PropagationinModernHigh-PerformanceStructuralSteels,“ ASMTransactions,Vol 60, No. 2, pp198-204, June1967. 37. Gross, M. R. andCzyryca,E. J. , “Effectsof Notchesand SaltwaterCorrosionontheFlexuralFatiguePropertiesofSteels for FtydrospaceVehicles,“ MELR&DReport420/66. 38. Davis, R. A. andQuist,W. E. , “FractureToughness,“ Mat~’- rials inDesignEngineering,pp91-97, Novernbcr1965. 39. Reynolds,M. B. , “FractureMechanicsandtheStabilityol’ .- EngineeringStructures,“ ReportNo. GeneralElectricAtomic Power- 4678. 40. Rolfe,S. T. , “Howto DesignforNotchToughness,“ Product Engineering,pp68-73, December21, 1964. 41. Wessel, E. T., “Correlationof LaboratoryDeterminationsof FractureToughnesswiththePerformanceof LargeSteelPressure Vessels,“ TheWeldingJournal,ResearchSupplement,pp415-s - 424-3, September1964. 42. Freed, C. N. , “Correlationof TWOFractureToughnessTestsfor High-StrengthSteels,“ NRLReport6607. 43. Gerridge,D. W. andSlutter,R. G. , “TheBrittleBehaviorof High-StrengthSteelWeldmentsFinalReport,“ April1965, FritzEngineeringLaboratoryReportNo. 200.61.364.8 (Lehigh University). 44. Rolfe, S. T. andNovak,S. R. , “Slow-BendKIGTestingof Medium-StrengthHigh-ToughnessSteels,“ Submittedto ASTM, September1967. 45. Schwartz,I. A. , Lange,E. A. , andMartin,M. L. , “Notch ToughnessPropertiesof PressureVesselSteelsProgress ReportI, “ TR67-021OCE, February1967. 46. Rornualdi,J. P. , “FractureArrestDesignConsiderations,“ ProceedingsoftheCrackPropagationSymposiumCranfield, September1961. -43- GLOSSARY As-rolled- Rolledmaterialwhichhasnopostfabricationheattreatment. Austenite- A solidsolutionof oneor moreelementsinface-centered cubiciron. Unlessotherwisedesignated,thesoluteis assumed ‘cobe carbon. Cv, CharpyV-notch,test - A pendulum-type,single-blowimpacttest of a specimencontaininga veenotchinoneside. SeeASTM MethodE23. Corrosionfatigue- Thereductioninfatiguepropertiesresultingfrom theapplicationof cyclicstressesin a corrosiveenvironment. Delayedcracking- Crackingobservedinweldments,usuallya number ofhoursor daysaftercompletionoftheweld. DPFI,diamondpyramidhardness- Hardnessof a materialdetermined witha pyramid-shapeddiamondindenterundervariousloads. Also calledtheVickershardnesstest. Drop-weighttest - A guillotine,single-blowimpacttestona specimen containinga brittleweldcrackstarterto definethenilductility transitiontemperature.SeeASTMMethodE208. Elasticdeformation- Changeof dimensionswhena structureis stressed belowtheelasticlimit, theoriginaldimensionsbeingrestored afterthestresshasbeenremoved. Elasticinstability- Failureof a structuralmemberbyexceedinga criticalvalueof loadabovewhichthedeflectionsandstresses arenolongerproportionalto loadalthoughthematerialsof constructionare still intheelasticrange. Also calledelastic buckling. Elongation- Intensiletesting,thechangeinthelengthofthegagesection whenfracturedwithinthegagesection. Usuallypresentedas a percentageof theoriginalgagelength. Explosionbulgetest - Thesubjectionof atest plateto anexplosive forcesufficientto producebiaxialstressesabovetheelastic limitina circulartest section. Explosionbulgecrackstartertest - Thesubjectionof a testplatehaving a brittleweldcrackstarterto anexplosiveforcesufficientto producebiaxialstressesabovetheelasticlimitina circular test section. S~eNAVSHIPS0900-005-5000. Fastfracture- Therapid,uncontrolledpropagationof a fractureat -44- stresseseitheraboveor belowtheelasticlimit. Fastfracture maybebrittleor ductile. Fatigue- Thephenomenonleadingto fractureunderrepeatedor fluctu- atingstresseshavinga maximumvalueless thanthetensile strengthofthematerial. Fatiguecrackinitiationlife - Thenumberof cyclesof alternatingstress requiredto developa detectablefatiguecrackina material. FTE, fracturetransitionfor elasticloading- Thattemperature,usually NDTT+600F, abovewhicha flawcannotbecomeunstablewhen subjectedto stressesbelowtheyieldstrength. FTP, fracturetransitionforplasticloading- Thattemperature,usually NDTT+120”F, abovewhichfailuremustoccurbyplasticinstability. Fullyautomaticweldingprocesses- Weldingwithequipmentwhichper- formstheentireweldingoperationwithoutconstantobservation andadjustmentofthecontrolsby anoperator. ‘ H2S- Hydrogensulfide, Hardenability- Thepropertyof a ferrousalloywhichaffectsthedepth of hardnessinducedbyquenching. Rc, Rockwell“C” hardness- Hardnessof a materialdeterminedwitha 120”conicaldiamondindentoranda 150-kgload. HA.Z,heataffectedzone- Ina weldment,theunfusedmaterialimmedi- atelyadjacenttotheweldpuddlewhichis heatedsufficientlyto changeits microstructureor properties. HSLAQ andT - High-strength,low-alloysteelswhicharequenchedand temperedto developthedesiredtensileproperties. Hydrogenembrittlement- Theloss inductilityof metalswhichhave absorbedhydrogen. Interpasstemperature- Temperatureoftheweldmetalandadjacentbase metalpriorto subsequentwelding. K~c, critical stress intensity factor - The value of the stress intensity factorsufficientto resultinunstablecrackpropagation. Lowcyclefatigue- Failureof a materialinless than100,000cyclicload applications.Generally,theloadsarehighenoughto cause plasticdeformationofthematerialof construction.Sometimes referredto as “plasticfatigue”or “highstrain”fatigue. Lowhyclro~cntechniques- Techniquessuchas preheating,bakingof -45- electrodes,etc., whichcontrolthehydrogencontentoftheweld metal. Thisincludestheuseof lowhydrogen-mineralcoated electrodes. Martensite- A mstastablephaseof steel, formedbytransformationfrom austenitewhenthecriticalcoolingrateis exceeded. Microhardness- Hardnessof a phaseor othersmallareaof a polished metalspecimen,determinedwiththeTukonor Knoopmethods. NDTT,nilductilitytransitiontemperature- Thattemperaturebelowwhich a smallflawcaninitiatefastfractureatyieldstrengthstress levels. Nonmetallicinclusions- Nonmetallicmaterials(usuallyoxides,silicates, or sulfides) ina solidmetallicmatrix. Normalizedsteels- Steelswhichhavebeenheatedabovethetransforma- tiontemperaturerangethenair cooledto roomtemperature. Notchedfatiguestrength- Thefatiguestrengthof a materialas determined withspecimenscontaininga notch. Plasticdeformation- Thepermanentdeformationachievedwhena stressis removedafterexceedingtheelasticlimit. Plasticinstability- Failureof a structuralmemberbyexceedinga criticalvalueof loadabovewhichdeflectionsandstressesare nolongerproportionalto loadbecausetheyieldstrengthofthe materialhasbeenexceeded. Postheat- Thermaltreatmentappliedafterthecompletion01awelding or cuttingoperation. PPM- Partspermillion. Preheat- Thermaltreatmentappliedpriorto aweldingor cutting operation. Semiautomaticweldingprocess- Weldingwithequipmentwhichcontrols thefeedof fillermetalandarc characteristics.Theadvance speedofweldingandmanipulationofthearc aremanuallycontrolled, Shakedown- Thedevelopmentof a steady-staterelationshipbetween stressandstrainina lowcyclefatiguetestor ina structure. Shieldingsystem- A gasor combinationof gasesand/orslagwhich protectsthemoltenpuddleIromtheatmosphereuntilmetal soliclifies. ShortcircuitingMIGprocess- Anarcw-eldingprocesswhereincoalescence — -. -46- is producedbyheatingwithrepeatedshortcircuitsbetweenthe fillermetalelectrodeandthework.Shieldingis obtainedwitha suitablegasor mixtureof gases. Stresscorrosioncracking- Developmentof transgranularor inter- granularcracksunderthecombinedinfluenceof stressanda corrosiveatmosphere. Stressconce~tratio~ factor - The ratio of the maximum s’tress at the root of a notch to the average stress over the e~’tire cross sectio~. Submergedarcweldingprocess- Anarcweldingprocesswhereincoales- cenceis producedwithoneor moreelectricarcsbetweena bare metalelectrodeor electrodesandthework. Shieldingis obtained bya blanketof granularfusiblematerialonthework. Tensilefailure- Fractureresultingfromstressesexceedingthetensile strengthofthematerial. UTS,ultimatetensilestrength- Inthetensiletest, themaximumload thatthematerialcanwithstanddividedbytheinitialcross- sectionalarea. Weldments- Anassemblywhosepartsarejoinedbywelding. Yieldpoint- Thestressatwhichanincreaseindeformationoccurswith- outanincreaseinload. It occursonlyinmildor mediumcarbon steels. Yieldstrength,O.2%offset- Thestress atwhichthegagesectionof a tensilespecimenhasundergonea plasticdeformationof O.2~0. . -47- souTIIwEsT RE5EARCI-IINSTITUTEQUESTIONNAIRE SHIPSTRUCTURECOMMITTEECONTRACTNOO024-67-C-5416 1, Haveyouusedquenchedandtempered HSLAsteels? (yes) (no) For surfaceshipconstruction (yes) (no) For repairof su~faceships (yes) (no) For reconstructionof surfaceships (yes) (no) 2. Whatspecifictypesof quenchedand temperedHSLAsteelshaveyouused? 3. Are yourWeldingProceduresfor these materialsavailablefor useinthis program? (yes) (no) (Weareinterest~dinall procedures, i. e. , automatic,manual,all positions, fillet, tee, etc.) 4.1 Doyouhav-eformalproceduresfor controlof moisturein: (a) Lowhydrogenelectrodes (yes) (110 (b) Submergedarc fluxes (yes) (no If theaboveanswersareyes, arethey available for use in this program? (yes) (no) 4.2 Ifyoudonothaveformalprocedures for controlof moisturedoyouexercise anyformof control? Pleaseexplain. (a) Lowhydrogenelcctrodos (b) Submersedarc fl~lxcs .~& wouldbe realisticforweldingA517mate- rialsin theconstructionof merchantcargo shipsinthefollowingthicknesses? Thickness Preheat‘F Interpass“F 1/2” 1,, 1-1/2” Over 6. Doyoufeelthatit wouldbepracticalto have morethanoneprocedurefor thesamemate- rial? i. e., a strictprocedurefor critical areaswitha downgradedprocedurefor less critical areas. (yes) (no) 7. Axeyournondestructivetestingpro- ceduresavailablefor useinthis program? (yes) (no) 8. Whattype(s)ofnondestructivetech- niqueshaveyouusedto inspect weldmentsof HSLAonmerchant cargovessels? Visual MagneticParticle Radiography Ultrasonic 9. Whattypesof impactof fracture toughnesstestinghaveyouused whenqualifyingweldingprocedures for quenchedandtemperedsteels? 10. (a) Doyouhavea recommended minimumweldingprocedurefor - repairweldinganycombinationof HSLAsteelsandplaincarbon steelsthatmaybefoundin car’go shipweldments,to beperformed in smallremoteportsandat sea whereweldingsupplies,procedure -49- controlsandwelderqualifications arelimited? (yes) (no) (b) Is thisprocedureavailablefor useinthisprogram? (yes) (no) UNCLASSIFIED SecurityClassification DOCUMENTCONTROLDATA-R&D (Security claaaificationof title, body of abstractandindexingannotfitionmust beenteredwhenth* overall report is cJ=s~fied) 1.ORIGINATINGACTIVITY(Co orato+thor) 20 REPORT 5ECUPITY CLASSIFICATION SouthwestResearch~ns.t~tute unclasslfl~d. . 8500CulebraRoad Zb GROUP SanAntonio,Texas 78228 ------1. REPORTTITLE StudyoftheFactorsWhichAffecttheAdequacyofHigh-Strength Low-AlloySteelWeldmentsforCargoShipHulls 1. DESCRIPTIVENOTES(Typeof raporfsndinclusiva datas) FirstTechnicalReport ;.AUTHOR(S)(LHs/mw?a,first name,initi s{) Norris,E.B. Lowenberg,A.L. Pickett,A.G. Wylie,R.D. i. REPORT DATE 76. TOTAL No. OF PAGES 7b, NO. QF REFS August1969 4~ 46 3e. CONTRACT OR GRANT NO. 9fI ORIGINATOR’SREPOWT NUMBER(S) NOO024-67-C-5416 07-2147-01 b, PROJECT NO SE013-03-04 c. 9b. OTHER REPORT NO(S)(AnYorh.rnumbersthatm-yb*as*im-d fiisreport) Task2022 d, SSC-199 10.AvAILABILITY/LIMITATIoN NOTICES Distributionofthisdocumentisunlimited Il. SUPPLEMENTARYNOTES 12.sponsoring MILITARyACTIVITY DepartmentoftheNavy None NavalShipEngineeringCenter Washington,D.C. 20360 13.ABSTRACT A recentadventinshipconstructionistheuseofhigh-strengthlow- alloysteelswith100,000-psiyieldstrengthsforshiphullstructuralelements, makinguniquedesignconceptspossible.Thisapplicationisa significantstep, butthematerial’sbehaviorneedstobefurtherdefined.Forthebenefitofthe owners,designers,andfabricators,a projectwasinitiatedbytheShipStructure Committeetoestablishwhichmechanicalpropertiesshouldbeusedascriteriafor judgingperformance,toevaluatelarge-scaleweldmentstodeterminethesuita- bilityofthesecriteria,andtoselectsmall-scalelaboratoryteststhatcor- relatewiththelarge-scaletests.A surveyofshipyardsandshiprepairers revealedthatthesenewermaterialsarebeingusedonlyincriticalstrength elementsofshiphulls.Weldingproceduresarequalifiedbyexplosionbulgetests todefinesafeoperatingtemperaturelimits.A surveyofthepropertiesofthese materialsandtheirweldmentsindicatedthattheHAZmightbesuspectedtobemore susceptibletocrackinitiationandgrowththantheunaffectedbaseplate,butit wasconcludedthatmoredataareneededtoestablishserviceabilitycriteria.It isrecommended-thatlaboratoryinvestigationsbeperformedtodeterminetheeffect ofenvironmentandcyclicstressesonslowcrackgrowthandestablishthefracture toughnessofweldments,includingtheeffectsofresidualstressandmetallurgical andgeometricdiscontinuities. DD,W’!.1473 UNCLASSIFIED SecurityClassification —-— “Gucu.,y *.-.L-.L.*- L.”,, I4. LINK A LINK B LINK C KEY WORDS ROLE WT ROLE WT ROLE WT MerchantCargoShips High-StrengthLow-AlloySteels HSLAWeldments ASTM514Steel ASTM517Steel FractureToughnessofHSLASteelsand Weldments INSTRUCTIONS L ORIGINATINGACTIVITY. Enterthe nameandaddress imposedby securityclassification, usingstandardstatements of thecontractor,subcontractor,grantee,Departmentof ?lI+ such as: fense activityor otherorganization(corporate author) issuing .(1) “Cjuali[iedrequesters mayobtaincopies of this thereport. reportfromDDC” 2+x REPORTSECUEITYCLASSIFICATIONEnterthe over- all securityclassification of thereport. Indicatewhether (2) “Foreign armouucementanddisseminationof this “Restricted Data” ISinclude& Markingis to be in accord- report by DDC is not authorized. ” ante with appropriate security regulations, (3) “U. S.Governmentagencies mayobtaincopies of this reportdirectlyfromDDC. OtherqualifiedDDC 2b. 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KEYWORDS:Key wordsare technicallymeaningfulterms subproject number,systemnumbers,task number,etc. or shortphrasesthatcharacterizea reportandmaybe used as 9a. ORIGINATOR’SREPORTNUMBER(S):Entertho offi- indexentriesfor catalogingthe report. Keywordsmustbe cial reportnumberby whichthedocumentwill be identified selected so that no security classification is required. ldenti- andcontrolledby the ori~inatingactivity. This numbermust fiers, suchas equipmentmodeldcs~gnat~on,tradename,milita~ be uniqueto this report. projectcode name,geographiclocat~on,maybe usedas key 9b. OTHER REPORT NUMBER(S):If wordsbutwill be followedby an indication of technical COn- the reporthas been text, The ass~gnrne”tof links, roles, andweights IS optional. assignedanyotherreportnumbers(either by the originator or by the sponsor),also enterthisnumber(s). 10.AVAILABILITY/LIMITATIONNOTICES:Entermy lim- itationson furtherdisseminationof the report,otherthanthose UNCLASSIFIED — Security Classification — .- — MR. M. L SELLERS, ChC7i.~al’2 MR. ,1. E. IHERZ (1,11) Naval Architect Chief Structural Design Engineer Newport News Shipbuilding Sun Shipbuilding and Dry Dock Company and Dry Dock Company MR. G. E. KAMPSCHAEFER, Ji? (III) DR. H. N. ABRAMSDN (1,11) Manager, Application Engineering Director, Dept. of Mechanical Sciences ARMCO Steel Corporation Southwest Research Institute PROF. R. R. NOTON (11,111) MR. W. H. BUCKLEY (1,11) F)epartment of Aeronautics Chief, Structural Criteria and Loads and Astronautics Bel 1 Aerosystems Company Stanford University DR. D. P. CLAUSING (III) MR. M. W. OFFNER (11” Senior Scientist, Edgar C. Pain Consulting Engineer Laboratory for Fundamental Research U. S. Steel Corporation DR. S. T. ROLFE (III Division Chief, ApDl NR. D. P. COURTSAL (11,111) Center Assistant Chief Enqineer U. S. Steel Corporation Dravo Corporation PROF. J. WFERTMAN (11,111) MR. A. E. COX (1,11) Walter P. Murphy Professor General Program Manager of Materials Science Newport News Shipbuilding Northwestern University and Dry Dock Company CDR R. M. WHITE, USCG (1,11) MR. J F. DALZELL (I) , coordinator Chief, Applied Engineering Section Senior Research Scientist U. S. Coast Guard Academy Hydronautics, Incorporated PROF. R. A. YPGLE (II) , (~OOd7iF!dOr CDR D. FAULKNER, RCNC (I, II) Department of Naval ).rchitecture Staff Constructor Officer and Marine Engineering British Navy Staff University of Michigan PROF. J. E. GOLDBERG (1,11) School of Civil Engineering MR. R. W. RUMKE, EZ~CUtiV~ S’ecmtaru Purdue University Ship Research Committee (I) = k?>i.sOr>yCroup T, (./1) = A/sow (GT>07C .1.?. SHIP STRUCTURE COMMITTEE PUBLICATIOP!S SSC-186,Effeet oaf ship Sti fj%ss upon the s’trwcturalResponse of a Carg] Ship to an Impulsive Load. by M. St. Oenis and S. N. Fersht. September 1968. AD 675639. SSC-187, Biennial Report ojf Ship Stmctur’e Committee. September 1968. AD 675022. SSC-188,EFf SSC-189,The Video ?ape Reeo~ding of U1trasonic Te.st Inforination by R. A. Youshaw. C. H. Dyer and E. L. Criscuolo. October 1968. AD 677894. SSC-190,Bending ?Vomen.tDiatr’ibution in a Mcwiner>Cargo Ship Mode L in i?egukr and I“rwgu lcw Waves of Extreme Steepness by N. M. Mania r and E. Numata. November 1968. AD 689187 SSC-191,Plastic }’louin the Local on Notches and Clacks in Fe-3Si Steel [J?!.depConditions Approaching Plane Strain by G. T. Hahn and A. R. Rosenfield. November 1968. AD 680123. SSC-192,l:oteh Rrittteness after Fracture by C. Mylonas and S. Kobayashi . January 1969. AO 681051. SSC-193,Deoelopmefltof ?k%thematiiealModels for Describing S%ip Structural Response in waves by P. Kaplan. January 1969. AD 682591. SSC-194,Feasibility Study of Model Test on Ship wull Girder by H. Becker. May 1969. AD 687220. SSC-195,uewvwnendcd Emergenq Welding Procedure for Temporary Hepcri-wof Ship stea%s by A. L. Lowenberg and P. D. Matson. May 1969. AD 688119. SSC-196,ha lysis and Inteipetation of Fv.1Z-Scale Data on Midship Bending S1.WSSCX of .DPYca~~goShips by D. Hoffman and E. V. Lewis. June 1969. SSC-197,,!n !nt~e,st;i:ga,:.ion o.fthe :/L7:Z~:t~~of Comp,uter SimuZaLicm to .Pred,~ct ,%ip :;trwctur~a2.Resporma in ?iavcsby P. Kaplan, T. P. Sarqent and A. I. Raff. June 1969. SSC-198,Straightening Distorted ~~e~~ent~ by H. E. pattee, ‘. ‘. ‘Vans and R. E. Monroe. August 1969.