发布时间 : 星期一 文章ASTM A262 2015 奥氏体不锈钢晶间腐蚀敏感性检测标准方法更新完毕开始阅读
Designation:A262?15
StandardPracticesfor
DetectingSusceptibilitytoIntergranularAttackinAusteniticStainlessSteels1Thisstandardisissuedunderthe?xeddesignationA262;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(′)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.
1.Scope*
1.1Thesepracticescoverthefollowing?vetests:
1.1.1PracticeA—OxalicAcidEtchTestforClassi?cationofEtchStructuresofAusteniticStainlessSteels(Sections4to13,inclusive),
1.1.2PracticeB—FerricSulfate-SulfuricAcidTestforDe-tectingSusceptibilitytoIntergranularAttackinAusteniticStainlessSteels(Sections14to25,inclusive),
1.1.3PracticeC—NitricAcidTestforDetectingSuscepti-bilitytoIntergranularAttackinAusteniticStainlessSteels(Sections26to36,inclusive),
1.1.4PracticeE—Copper–CopperSulfate–SulfuricAcidTestforDetectingSusceptibilitytoIntergranularAttackinAusteniticStainlessSteels(Sections37to46,inclusive),and1.1.5PracticeF—Copper–CopperSulfate–50%SulfuricAcidTestforDetectingSusceptibilitytoIntergranularAttackinMolybdenum-BearingAusteniticStainlessSteels(Sections47to58,inclusive).
1.2TheOxalicAcidEtchTestisarapidmethodofidentifying,bysimpleetching,thosespecimensofcertainstainlesssteelgradesthatareessentiallyfreeofsusceptibilitytointergranularattackassociatedwithchromiumcarbideprecipitates.Thesespecimenswillhavelowcorrosionratesincertaincorrosiontestsandthereforecanbeeliminated(screened)fromtestingas“acceptable.”Theetchtestisapplicableonlytothosegradeslistedintheindividualhotacidtestsandclassi?esthespecimenseitheras“acceptable”oras“suspect.”
1.3Theferricsulfate-sulfuricacidtest,thecopper–coppersulfate–50%sulfuricacidtest,andthenitricacidtestarebasedonweightlossdeterminationsand,thus,provideaquantitativemeasureoftherelativeperformanceofspecimensevaluated.Incontrast,thecopper–coppersulfate–16%sulfuricacidtestis
basedonvisualexaminationofbendspecimensand,therefore,classi?esthespecimensonlyasacceptableornonacceptable.1.4Thepresenceorabsenceofintergranularattackinthesetestsisnotnecessarilyameasureoftheperformanceofthematerialinothercorrosiveenvironments.Thesetestsdonotprovideabasisforpredictingresistancetoformsofcorrosionotherthanintergranular,suchasgeneralcorrosion,pitting,orstress-corrosioncracking.
NOTE1—SeeAppendixX1forinformationregardingtestselection.
1.5ThevaluesstatedinSIunitsaretoberegardedasstandard.Theinch-poundequivalentsareinparenthesesandmaybeapproximate.
1.6Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.Somespeci?chazardsstatementsaregivenin10.1,20.1.1,20.1.9,31.3,34.4,53.1.1,and53.1.10.2.ReferencedDocuments
2.1ASTMStandards:2A370TestMethodsandDe?nitionsforMechanicalTestingofSteelProducts
A380/A380MPracticeforCleaning,Descaling,andPassi-vationofStainlessSteelParts,Equipment,andSystemsD1193Speci?cationforReagentWater
E3GuideforPreparationofMetallographicSpecimens2.2ASMECode:3ASMEBoiler&PressureVesselCode,SectionIX2.3ACSSpeci?cations:4ReagentChemicals,Speci?cationsandProcedures
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.ForAnnualBookofASTMStandardsvolumeinformation,refertothestandard’sDocumentSummarypageontheASTMwebsite.3AvailablefromAmericanSocietyofMechanicalEngineers(ASME),ASMEInternationalHeadquarters,TwoParkAve.,NewYork,NY10016-5990,http://www.asme.org.4AvailablefromAmericanChemicalSociety(ACS),1155SixteenthStreet,NW,Washington,DC20036,http://www.acs.org
2ThesepracticesareunderthejurisdictionofASTMCommitteeA01onSteel,StainlessSteelandRelatedAlloysandarethedirectresponsibilityofSubcommitteeA01.14onMethodsofCorrosionTesting.
CurrenteditionapprovedSept.1,2015.PublishedSeptember2015.Originallyapprovedin1943.Lastpreviouseditionapprovedin2014asA262–14.DOI:10.1520/A0262-15.1*ASummaryofChangessectionappearsattheendofthisstandard
Copyright?ASTMInternational,100BarrHarborDrive,POBoxC700,WestConshohocken,PA19428-2959.UnitedStates
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2.4ISOStandard:5ISO3651-2DeterminationofResistancetoIntergranularCorrosionofStainlessSteels—Part2:Ferritic,Austenitic,andFerritic-Austenitic(Duplex)StainlessSteels—CorrosionTestinMediaContainingSulfuricAcid3.PurityofReagents
3.1PurityofReagents—Reagentgradechemicalsshallbeusedinalltests.Unlessotherwiseindicated,itisintendedthatallreagentsconformtothespeci?cationsoftheCommitteeonAnalyticalReagentsoftheAmericanChemicalSociety6wheresuchspeci?cationsareavailable.Othergradesmaybeused,provideditis?rstascertainedthatthereagentisofsufficientlyhighpuritytopermititsusewithoutlesseningtheaccuracyofthetestresult.
3.2PurityofWater—Unlessotherwiseindicated,referencestowatershallbeunderstoodtomeanreagentwaterasde?nedbyTypeIVofSpeci?cationD1193.
PRACTICEA—OXALICACIDETCHTESTFORCLASSIFICATIONOFETCHSTRUCTURESOF
AUSTENITICSTAINLESSSTEELS(1)74.Scope
4.1TheOxalicAcidEtchTestisusedforacceptanceofwroughtorcastausteniticstainlesssteelmaterialbutnotforrejectionofmaterial.UseofA262PracticeAasastand-alonetestmayrejectmaterialthattheapplicablehotacidtestwould?ndacceptable;suchuseisoutsidethescopeofthispractice.4.2Thistestisintendedtobeusedinconnectionwithotherevaluationtestsdescribedinthesepracticestoprovidearapidmethodforidentifyingqualitativelythosespecimensthatarecertaintobefreeofsusceptibilitytorapidintergranularattackintheseothertests.Suchspecimenshavelowcorrosionratesinthevarioushotacidtestswhichrequirefrom15to240hofexposure.Thesespecimensareidenti?edbymeansoftheiretchstructures,whichareclassi?edaccordingtothecriteriagiveninSection11.
4.3TheOxalicAcidEtchTestmaybeusedtoscreenspecimensintendedfortestinginPracticeB—FerricSulfate-SulfuricAcidTest,PracticeC—NitricAcidTest,PracticeE—Copper-CopperSulfate–16%SulfuricAcidTest,andPrac-ticeF—Copper-CopperSulfate–50%SulfuricAcidTest.4.4Eachoftheseotherpracticescontainsatableshowingwhichclassi?cationsofetchstructuresonagivenstainlesssteelgradeareequivalenttoacceptableorsuspectperformanceinthatparticulartest.Specimenshavingacceptableetchstructuresneednotbesubjectedtothehotacidtest.Specimenshavingsuspectetchstructuresmustbetestedinthespeci?edhotacidsolution.
AvailablefromInternationalOrganizationforStandardization(ISO),1,ch.delaVoie-Creuse,CP56,CH-1211Geneva20,Switzerland,http://www.iso.org.6ForsuggestionsonthetestingofreagentsnotlistedbytheAmericanChemicalSociety,seeAnalarStandardsforLaboratoryChemicals,BDHLtd.,Poole,Dorset,U.K.,andtheUnitedStatesPharmacopeiaandNationalFormulary,U.S.Pharma-copeialConvention,Inc.(USPC),Rockville,MD.7Theboldfacenumbersinparenthesesrefertoalistofreferencesattheendofthisstandard.
54.5Therearetwoclassesofspecimenstobeconsidered:basemetal,andprocess-affectedmetal.
4.5.1Process-affectedmetalcontainsanyconditionthataffectsthecorrosionpropertiesofthematerialinanon-uniformway,suchas(butnotlimitedto)welds;carburized.nitrided,oroxidizedsurfaces;mechanicaldeformation;andareasaffectedbyheat.Basemetalhasnoneoftheseconditions.
4.5.2BecausePracticesB,C,andFinvolveimmersingtheentirespecimenandaveragingthemasslossoverthetotalspecimenarea,andbecausewelding,carburization,mechanicaldeformation,andthelikeaffectonlypartofaspecimen,thepresenceofprocess-affectedmetalinaspecimencanaffectthetestresultinanunpredictablewaydependingonthepropor-tionsoftheareaaffected.
4.5.3Ifthepresenceoftheseorotherlocalizedconditionsisaconcerntothepurchaser,thenteststhatdonotaveragethemasslossoverthetotalspecimensurfacearea,suchasPracticeA,theOxalicAcidEtchTest,orPracticeE,theCopper–CopperSulfate–SulfuricAcidTestforDetectingSusceptibilitytoIntergranularAttackinAusteniticStainlessSteels,shouldbeconsidered.
5.SummaryofPractice
5.1Aspecimenrepresentativeofthematerialtobeevalu-atedispolishedtoaspeci?ed?nishandover-etchedusingoxalicacidelectrolytically.Theetchedspecimenisthenexaminedusingametallurgicalmicroscope.Theetchedstruc-tureiscomparedwithreferencephotographstodeterminewhetherthematerialisacceptableorsuspect.Suspectmaterialisthensubjectedtothespeci?edhotacidimmersiontest.
--`,`,``,``,`,,`,,,,,,```,`,,```-`-`,,`,,`,`,,`---6.Signi?canceandUse
6.1Useoftheetchtestallowsrapidacceptanceofspeci?clotsofmaterialwithouttheneedtoperformtime-consumingandcostlyhotacidimmersiontestsonthoselots.7.Apparatus
7.1EtchingCell:
7.1.1Anetchingcellmaybeassembledusingcomponentsasdescribedinthissection.Alternatively,acommercialelectropolisher/etcher(asusedformetallographicsamplepreparation)maybeusedforsmallspecimensprovidedthecurrentdensityrequirementof10.2ismet.
7.1.2SourceofDirectCurrent—Battery,generator,orrec-ti?ercapableofsupplyingabout15Vand20A.
7.1.3Ammeter—Fordirectcurrent;usedtomeasurethecurrentonthespecimentobeetched.
7.1.4VariableResistance—Usedtocontrolthecurrentonthespecimentobeetched.
7.1.5Cathode—Astainlesssteelcontainer,forexample,a1-L(1-qt)stainlesssteelbeaker.
7.1.5.1AlternateCathode—Apieceof?atstainlesssteelatleastaslargeasthespecimensurface.
7.1.6ElectricalClamp—Toholdthespecimentobeetchedandtocompletetheelectricalcircuitbetweenthespecimenandthepowersourcesuchthatthespecimenistheanodeofthecell.
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7.1.7Thepowersource,resistor,andammetermustbesized10.2.1.2Adjustthevariableresistanceuntiltheammeterappropriatelyforprovidingandcontrollingthecurrentasreadinginamperesisequaltothetotalimmersedareaofthespeci?edin10.2ofthispractice.
specimeninsquarecentimetres.
7.1.8Asdescribed,theelectrolytecontaineristhecathode;itmaybeastainlesssteelbeakerorfabricatedfromstainless10.3Ayellow-green?lmisgraduallyformedonthecath-steelsuchasbyweldingasectionoftubeorpipetoa?atplateode.Thisincreasestheresistanceoftheetchingcell.Whenthisorsheet.Alternatively,theelectrolytecontainermaybeglassoccurs,removethe?lmbyrinsingtheinsideofthestainless(orothernon-conducting,corrosionresistingmaterial)inlieusteelbeaker(orthesteelusedasthecathode)withanacidsuchofastainlesssteelcontainer,andthecathodemaybea?atplateas30%HNO3.
orsheetofacorrosionresistingalloy.Inthislattercase,the?at10.4Thetemperatureoftheetchingsolutiongraduallysurfaceofthecathodemustbeatleastaslargeas,facing,andincreasesduringetching.Keepthetemperaturebelow50°C.approximatelycenteredon,thepreparedsurfaceofthespeci-Thismaybedonebyalternatingtwocontainers.Onemaybemen.Othercon?gurationsoftheelectrodesmightnotprovidecooledintapwaterwhiletheotherisusedforetching.
uniformetchingoverthespecimensurface.Inanycase,the10.4.1Therateofheatingdependsonthetotalcurrentsizeandshapeofthespecimendictatethesizeandconstruction(ammeterreading)passingthroughthecell.Therefore,keepoftheetchingcellandofthepowersourceandcontrols.Thetheareatobeetchedassmallaspossiblewhileatthesametimeoverridingprincipleisthattheetchneedstobeuniformovermeetingtherequirementsofdesirableminimumareatobethesurfacetobeexamined.
etched.
7.2MetallurgicalMicroscope—Forexaminationofetched10.5Avoidimmersingtheclampholdingthespecimeninmicrostructuresat250to500diameters.theetchingsolution.
8.ReagentsandMaterials
10.6Rinsing—Followingetching,rinsethespecimenthor-oughlyinhotwaterandtheninacetoneoralcoholtoavoid8.1EtchingSolution(10%)—Dissolve100gofreagentcrystallizationofoxalicacidontheetchedsurfaceduringgradeoxalicacidcrystals(H2C2O4·2H2O)in900mLofdrying.
reagentwater.Stiruntilallcrystalsaredissolved.
8.1.1AlternateEtchingSolution(See10.7)—Dissolve100g10.7Itmaybedifficulttorevealthepresenceofstepofreagentgradeammoniumpersulfate((NHstructuresonsomespecimenscontainingmolybdenum(AISI4)2SmLofreagentwater.Stiruntildissolved.2O8)in900316,316L,317,317L),whicharefreeofchromiumcarbidesensitization,byelectrolyticetchingwithoxalicacid.Insuch9.SamplingandTestSpecimens
cases,analternateelectrolyteofammoniumpersulfatemaybe9.1Thespeci?edhotacidtestprovidesinstructionsforusedinplaceofoxalicacid.(See8.1.1.)Anetchfor5or10samplingandforspecimenpreparationsuchasasensitizationminat1A/cm2inasolutionatroomtemperaturereadilyheattreatment.Additionalinstructionsspeci?ctoPracticeAdevelopsstepstructuresonsuchspecimens.follow:
11.Classi?cationofEtchStructures
9.2Thepreferredspecimenisacross-sectionincludingtheproductsurfacetobeexposedinservice.Onlysuch?nishingof11.1Examinetheetchedsurfaceonametallurgicalmicro-theproductsurfaceshouldbeperformedasisrequiredtoscopeat250×to500×forwroughtsteelsandatabout250×forremoveforeignmaterial.
caststeels.
9.3Wheneverpractical,useacross-sectionalareaof1cm211.2Examinetheetchedcross-sectionalareasthoroughlyormore.Ifanycross-sectionaldimensionislessthan1cm,bycompletetraversefrominsidetooutsidediametersofrodsthentheotherdimensionofthecross-sectionshouldbeaandtubes,fromfacetofaceonplates.
minimumof1cm.Whenbothdimensionsoftheproductare11.2.1Microscopicalexaminationofaspecimenshallbelessthan1cm,useafullcrosssection.
madeonmetalunaffectedbycold-working,carburization,welding,andthelike.Ifanyoftheseconditionsarefound,note9.4Polishing—Onalltypesofmaterials,polishcrosssec-theirpresenceinthereport.
tionalsurfacesthroughCAMI/ANSI600[FEPA/ISOP1200]inaccordancewithGuideE3priortoetchingandexamination.11.3ClassifytheetchstructuresintothefollowingtypesNotallscratchesneedtoberemoved.(Note2):
11.3.1StepStructure(Fig.1)—Stepsonlybetweengrains,10.Procedure
noditchesatgrainboundaries.
10.1(Warning—Etchingshouldbecarriedoutundera11.3.2DualStructure(Fig.2)—Someditchesatgrainventilatedhood.Gas,whichisrapidlyevolvedattheelectrodesboundariesinadditiontosteps,butnosinglegraincompletelywithsomeentrainmentofoxalicacid,ispoisonousandsurroundedbyditches.
irritatingtomucousmembranes.)
11.3.3DitchStructure(Fig.3)—Oneormoregrainscom-pletelysurroundedbyditches.
10.2Etchthepolishedspecimenat1A/cm2for1.5min.11.3.4IsolatedFerrite(Fig.4)—Observedincastingsand10.2.1Toobtainthecorrectspeci?edcurrentdensity:
welds.Stepsbetweenaustenitematrixandferritepools.
10.2.1.1Measurethetotalimmersedareaofthespecimento11.3.5InterdendriticDitches(Fig.5)—Observedincastingsbeetchedinsquarecentimetres.
andwelds.Deepinterconnectedditches.
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FIG.2DualStructure(250×)(SomeDitchesatGrainBoundariesinAdditiontoSteps,butNoOneGrainCompletelySurrounded)
FIG.4IsolatedFerritePools(250×)(ObservedinCastingsandWelds.StepsBetweenAusteniteMatrixandFerritePools)
11.3.6End-GrainPittingI(Fig.6)—Structurecontainsafewdeepend-grainpitsalongwithsomeshallowetchpitsat500×.(Ofimportanceonlywhenthenitricacidtestisused.)11.3.7End-GrainPittingII(Fig.7)—Structurecontainsnumerous,deepend-grainpitsat500×.(Ofimportanceonlywhennitricacidtestisused.)
NOTE2—Allphotomicrographsweremadewithspecimensthatwereetchedunderstandardconditions:10%oxalicacid,roomtemperature,1.5minat1A/cm2.
11.4Theevaluationofetchstructurescontainingonlystepsandofthoseshowinggrainscompletelysurroundedbyditchesinevery?eldcanbecarriedoutrelativelyrapidly.Incasesthatappeartobedualstructures,moreextensiveexaminationisrequiredtodetermineifthereareanygrainscompletelyencircled.Ifanencircledgrainisfound,classifythesteelasaditchstructure.
11.4.1Onstainlesssteelcastings(alsoonweldmetal),thestepsbetweengrainsformedbyelectrolyticoxalicacidetchingtendtobelessprominentthanthoseonwroughtmaterialsor
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--`,`,``,``,`,,`,,,,,,```,`,,```-`-`,,`,,`,`,,`---FIG.1StepStructure(500×)(StepsBetweenGrains,NoDitches
atGrainBoundaries)
FIG.3DitchStructure(500×)(OneorMoreGrainsCompletely
SurroundedbyDitches)