astm a262 2015 奧氏體不銹鋼晶間腐蝕敏感性檢測標(biāo)準(zhǔn)方法

1、Designation:A262?15StardPracticesfDetectingSusceptibilitytoIntergranularAttackinAusteniticStainlessSteels1ThisstardisissuedunderthefixeddesignationA262thenumberimmediatelyfollowingthedesignationindicatestheyearofiginalad

2、optioninthecaseofrevisiontheyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperepsilon()indicatesaneditialchangesincethelastrevisionreapproval.ThisstardhasbeenapprovedfusebyagenciesoftheU.S.Dep

3、artmentofDefense.1.Scope1.1Thesepracticescoverthefollowingfivetests:1.1.1PracticeA—OxalicAcidEtchTestfClassificationofEtchStructuresofAusteniticStainlessSteels(Sections4to13inclusive)1.1.2PracticeB—FerricSulfateSulfuricA

4、cidTestfDetectingSusceptibilitytoIntergranularAttackinAusteniticStainlessSteels(Sections14to25inclusive)1.1.3PracticeC—NitricAcidTestfDetectingSusceptibilitytoIntergranularAttackinAusteniticStainlessSteels(Sections26to36

5、inclusive)1.1.4PracticeE—Copper–CopperSulfate–SulfuricAcidTestfDetectingSusceptibilitytoIntergranularAttackinAusteniticStainlessSteels(Sections37to46inclusive)1.1.5PracticeF—Copper–CopperSulfate–50%SulfuricAcidTestfDetec

6、tingSusceptibilitytoIntergranularAttackinMolybdenumBearingAusteniticStainlessSteels(Sections47to58inclusive).1.2TheOxalicAcidEtchTestisarapidmethodofidentifyingbysimpleetchingthosespecimensofcertainstainlesssteelgradesth

7、atareessentiallyfreeofsusceptibilitytointergranularattackassociatedwithchromiumcarbideprecipitates.Thesespecimenswillhavelowcrosionratesincertaincrosionteststherefecanbeeliminated(screened)fromtestingas“acceptable.”Theet

8、chtestisapplicableonlytothosegradeslistedintheindividualhotacidtestsclassifiesthespecimenseitheras“acceptable”as“suspect.”1.3Theferricsulfatesulfuricacidtestthecopper–coppersulfate–50%sulfuricacidtestthenitricacidtestare

9、basedonweightlossdeterminationsthusprovideaquantitativemeasureoftherelativeperfmanceofspecimensevaluated.Incontrastthecopper–coppersulfate–16%sulfuricacidtestisbasedonvisualexaminationofbendspecimenstherefeclassifiesthes

10、pecimensonlyasacceptablenonacceptable.1.4Thepresenceabsenceofintergranularattackinthesetestsisnotnecessarilyameasureoftheperfmanceofthematerialinothercrosiveenvironments.Thesetestsdonotprovideabasisfpredictingresistancet

11、ofmsofcrosionotherthanintergranularsuchasgeneralcrosionpittingstresscrosioncracking.NOTE1—SeeAppendixX1finfmationregardingtestion.1.5ThevaluesstatedinSIunitsaretoberegardedasstard.Theinchpoundequivalentsareinparenthesesm

12、aybeapproximate.1.6Thisstarddoesnotpurpttoaddressallofthesafetyconcernsifanyassociatedwithitsuse.Itistheresponsibilityoftheuserofthisstardtoestablishappropriatesafetyhealthpracticesdeterminetheapplicabilityofregulatylimi

13、tationspritouse.Somespecifichazardsstatementsaregivenin10.120.1.120.1.931.334.453.1.153.1.10.2.ReferencedDocuments2.1ASTMStards:2A370TestMethodsDefinitionsfMechanicalTestingofSteelProductsA380A380MPracticefCleaningDescal

14、ingPassivationofStainlessSteelPartsEquipmentSystemsD1193SpecificationfReagentWaterE3GuidefPreparationofMetallographicSpecimens2.2ASMECode:3ASMEBoileritmaybeastainlesssteelbeakerfabricatedfromstainlesssteelsuchasbywelding

15、asectionoftubepipetoaflatplatesheet.Alternativelytheelectrolytecontainermaybeglass(othernonconductingcrosionresistingmaterial)inlieuofastainlesssteelcontainerthecathodemaybeaflatplatesheetofacrosionresistingalloy.Inthisl

16、attercasetheflatsurfaceofthecathodemustbeatleastaslargeasfacingapproximatelycenteredonthepreparedsurfaceofthespecimen.Otherconfigurationsoftheelectrodesmightnotprovideunifmetchingoverthespecimensurface.Inanycasethesizesh

17、apeofthespecimendictatethesizeconstructionoftheetchingcellofthepowersourcecontrols.Theoverridingprincipleisthattheetchneedstobeunifmoverthesurfacetobeexamined.7.2MetallurgicalMicroscope—Fexaminationofetchedmicrostructure

18、sat250to500diameters.8.ReagentsMaterials8.1EtchingSolution(10%)—Dissolve100gofreagentgradeoxalicacidcrystals(H2C2O42H2O)in900mLofreagentwater.Stiruntilallcrystalsaredissolved.8.1.1AlternateEtchingSolution(See10.7)—Dissol

19、ve100gofreagentgradeammoniumpersulfate((NH4)2S2O8)in900mLofreagentwater.Stiruntildissolved.9.SamplingTestSpecimens9.1Thespecifiedhotacidtestprovidesinstructionsfsamplingfspecimenpreparationsuchasasensitizationheattreatme

20、nt.AdditionalinstructionsspecifictoPracticeAfollow:9.2Thepreferredspecimenisacrosssectionincludingtheproductsurfacetobeexposedinservice.Onlysuchfinishingoftheproductsurfaceshouldbeperfmedasisrequiredtoremovefeignmaterial

21、.9.3Wheneverpracticaluseacrosssectionalareaof1cm2me.Ifanycrosssectionaldimensionislessthan1cmthentheotherdimensionofthecrosssectionshouldbeaminimumof1cm.Whenbothdimensionsoftheproductarelessthan1cmuseafullcrosssection.9.

22、4Polishing—OnalltypesofmaterialspolishcrosssectionalsurfacesthroughCAMIANSI600[FEPAISOP1200]inaccdancewithGuideE3pritoetchingexamination.Notallscratchesneedtoberemoved.10.Procedure10.1(Warning—Etchingshouldbecarriedoutun

23、deraventilatedhood.Gaswhichisrapidlyevolvedattheelectrodeswithsomeentrainmentofoxalicacidispoisonousirritatingtomucousmembranes.)10.2Etchthepolishedspecimenat1Acm2f1.5min.10.2.1Toobtainthecrectspecifiedcurrentdensity:10.

24、2.1.1Measurethetotalimmersedareaofthespecimentobeetchedinsquarecentimetres.10.2.1.2Adjustthevariableresistanceuntiltheammeterreadinginamperesisequaltothetotalimmersedareaofthespecimeninsquarecentimetres.10.3Ayellowgreenf

25、ilmisgraduallyfmedonthecathode.Thisincreasestheresistanceoftheetchingcell.Whenthisoccursremovethefilmbyrinsingtheinsideofthestainlesssteelbeaker(thesteelusedasthecathode)withanacidsuchas30%HNO3.10.4Thetemperatureoftheetc

26、hingsolutiongraduallyincreasesduringetching.Keepthetemperaturebelow50C.Thismaybedonebyalternatingtwocontainers.Onemaybecooledintapwaterwhiletheotherisusedfetching.10.4.1Therateofheatingdependsonthetotalcurrent(ammeterrea

27、ding)passingthroughthecell.Therefekeeptheareatobeetchedassmallaspossiblewhileatthesametimemeetingtherequirementsofdesirableminimumareatobeetched.10.5Avoidimmersingtheclampholdingthespecimenintheetchingsolution.10.6Rinsin

28、g—Followingetchingrinsethespecimenthoughlyinhotwatertheninacetonealcoholtoavoidcrystallizationofoxalicacidontheetchedsurfaceduringdrying.10.7Itmaybedifficulttorevealthepresenceofstepstructuresonsomespecimenscontainingmol

29、ybdenum(AISI316316L317317L)whicharefreeofchromiumcarbidesensitizationbyelectrolyticetchingwithoxalicacid.Insuchcasesanalternateelectrolyteofammoniumpersulfatemaybeusedinplaceofoxalicacid.(See8.1.1.)Anetchf510minat1Acm2in

30、asolutionatroomtemperaturereadilydevelopsstepstructuresonsuchspecimens.11.ClassificationofEtchStructures11.1Examinetheetchedsurfaceonametallurgicalmicroscopeat250to500fwroughtsteelsatabout250fcaststeels.11.2Examinetheetc

31、hedcrosssectionalareasthoughlybycompletetraversefrominsidetooutsidediametersofrodstubesfromfacetofaceonplates.11.2.1Microscopicalexaminationofaspecimenshallbemadeonmetalunaffectedbycoldwkingcarburizationweldingthelike.If

32、anyoftheseconditionsarefoundnotetheirpresenceintherept.11.3Classifytheetchstructuresintothefollowingtypes(Note2):11.3.1StepStructure(Fig.1)—Stepsonlybetweengrainsnoditchesatgrainboundaries.11.3.2DualStructure(Fig.2)—Some

33、ditchesatgrainboundariesinadditiontostepsbutnosinglegraincompletelysurroundedbyditches.11.3.3DitchStructure(Fig.3)—Onemegrainscompletelysurroundedbyditches.11.3.4IsolatedFerrite(Fig.4)—Observedincastingswelds.Stepsbetwee