RG1.050 低合金钢焊接余热温度的控制 1973

SSU.S.ATOMICENERGYCOMMISSIONREGULATORYGUIC0iDIRECTORATEOFREGULATORYSTANDARDSREGULATORYGUIDE1.50CONTROLOFPREHEATTEMPERATUREFORWELDINGOFLOW-ALLOYSTEELA.INTRODUCTIONGeneralDesignCriterion1,QualityStandardsandRecords,ofAppendixAto10CFRPart50,GeneralDesignCriteriaforNuclearPowerPlants,requiresthatstructures,systems,andcomponentsimportanttosafetybedesigned,fabricated,erected,andtestedtoqualitystandardscommensuratewiththeimportanceofthesafetyfunctiontobeperformed.AppendixBto10CFRPart50,QualityAssuranceCriteriaforNuclearPowerPlantsandFuelReprocessingPlants,requiresthatmeasuresbeestablishedtoassurecontrolofmaterialsandofspecialprocessessuchaswelding,andthatproperprocessmonitoringbeperformed.Thisguidedescribesanacceptablemethodofimplementingtheserequirementswithregardtothecontrolofweldingforlow-alloysteelcomponentsduringinitialfabrication.Thisguideappliestolight-water-cooledreactors.TheAdvisoryCommitteeonReactorSafeguardshasbeenconsultedconcerningthisguideandhasconcurredintheregulatoryposition.B.DISCUSSIONTheAmericanSocietyofMechanicalEngineersBoilerandPressureVesselCode(ASMEB&PVCode),SectionIII,NuclearPowerPlantComponents,'specifiescertainrequirementsassociatedwithmanufacturingCodeClass1,2,and3components.ProcedureQualificationSectionIIIrequiresadherencetoSectionIX,WeldingQualifications,'oftheASMEB&PVCode,includingtherequirements.governingprocedurequalificationsforwelds.ReviewoftherequirementsofSectionIXforprocedurequalificationsandthefabricationrequirementsofSectionIIIindicatesthe'CopiesmaybeobtainedfromAmericanSocietyofMechanicalEngineers,UnitedEngineeringCenter,345East47thStreet,NewYork,N.Y.10017.desirabilityofsupplerimentaryrequirementstoassureadequatecontrolofweldingvariablesintheproductionweldingoflow-alloysteels.Theassuranceofsatisfactoryweldsinlow-alloysteelscanbeincreasedsignificantlyand,inparticular,thepropensityforcracks(coldcracks)orreheatcracksforminginunderbeadareasandheat-affected:zones(HAZ)canbeminimizedbymaintainingproperpreheattemperaturesonthebasemetals'concurrentwithcontroIsonotherweldingvariables.Coldcrackingcanoccurwhenthesteelishardened;i.e.,undergoesaphasetransformationtomartensiteintheHAZand/orweldmetal.Themartensiteexhibitsbrittlefracturetendencies,anditmaynotbeabletowithstandrapidcoolingandthevolumechangeassociatedwiththephasetransformationwithouttheoccurrenceoflocalcracking.-ThissusceptibilitytocrackingincreasesWithhigherstresses,suchasthoseexperiencedwithincreasedthicknessofthepartbeingwelded,andalsoincreaseswithadecreaseinweldingenergyinput.Inordertoavoidorminimizetheeffectsofhardeningassociatedwithphasetransformation,alongercoolingtimeisneededfortheweld;inotherwords,thepreheattemperatureshouldbemaintainedhighenoughtoachieveanacceptableconditionofthephasetransformation.Itisgenerallyrecognizedthatatomichydrogenabsorptionanddiffusionintoandthroughtheregionbeingweldedhaveanimportantinfluenceonthetenancytoformcracks.Thelevelofhydrogeninweldfilli-metalislowenoughtoprecludeadverseeffectsinthewelds,butgreaterquantitiesofhydrogencanbepresentintheweldregionfromthedissociationofmoistureinhygroscopicweldingfluxesorduetoadsorptiononmetalsurfacesiftheweldingfluxesandsurfaceshavenotbeenproperlydriedbeforewelddeposition.EmbrittlementofmetalintheweldareaduetothepresenceofhydrogengenerallyoccursatlowertemperaturesandmaybepreventedbyprolongingtheUSAECREGULATORYGUIDESCopiesofpublishedguidesmaybeobtainedbyrequestindlcetingthedivisionsdesiredtotheU.S.AtomicEnergyCommission,Washington,D.C.20545,RegulatoryGuidesareIssuedtodescribeandmakeavailabletothepublicAttention:DirectorofRegulatoryStandards.CommentsandsuggestionsformathodsacceptabletotheAECRegulatorystaffofimplementingspecificpartsofImprovementsIntheseguidesaweencouragedandshouldbesenttotheSecretarytheCommission'sregulations,todelineatetechniquesusedbythestaffinoftheCommission,U.S.AtomicEnergyCommission,Washington,D.C.20646.evaluatingspecificproblemsorpostulatedaccidents,ortoprovideguidancetoAttention:Chief,PublicProceedingsStaff.applicants.RegulatoryGuidesarenotsubstitutesforregulationsandcompliancewiththemisnotrequired.MethodsandsolutionsdifferentfromthoesetoutinTheguidesweissuedinthefollowingtenbroaddivisions:theguideswillbeacceptableiftheyprovideabasisforthefindingsrequisitetotheisuanceorcontinuanceofapermitorlicensebytheCommission.1.PowerReactors6.Products2.ResearchandlTestReactors7.Transportation3.FuelsandMaterlaisFacilities8.OccupationalHealthPublishedguideswillberevisedperiodically,asappropriate,toaccommodate4.EnvironmentalandSiting9.AntitrustReviewcommentsAtoreflectnewinforrmationorexperience.6.MaterialsandPlantProtection10.GeneralMay1973)EtimetheweldmentIsmaintainedatpreheatingtemperatureorbyperformingapost-weldheattreatment.Prolongedtimeatpreheatingcanpreventorinterruptlocalhardeningandassistinreducingadverseeffectsofapotentialhydrogengradient.Thisgradientwoulddisappearbymeansofdiffusionofthehydrogenbeforetheweldmentisreturnedtoroomtemperature.Therefore,theminimumpreheattemperatureshouldbeestablishedtoassureadesirablecoolingratefortheweld,andth