Designation:A561−08(Reapproved2014)StandardPracticeforMacroetchTestingofToolSteelBars1ThisstandardisissuedunderthefixeddesignationA561;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.1.Scope1.1Thispracticeformacroetchtestinghasbeenfoundtobeausefulandreliablemethodforevaluatingthequalityoftoolsteelbars.Itisusedasaqualitycontrolandinspectiontesttorevealbydeepacidetchingthemacrostructureinspecimenscutfrombarsandtoshowthepresenceofsuchconditionsaspipe,cracks,porosity,segregation,orforeignmaterial.Theetchedsurfaceisgenerallyexaminedvisually,butmagnifica-tionuptoabout10×isoccasionallyemployed.1.2Thevaluesstatedininch-poundunitsaretoberegardedasstandard.ThevaluesgiveninparenthesesaremathematicalconversionstoSIunitsthatareprovidedforinformationonlyandarenotconsideredstandard.2.ReferencedDocuments2.1ASTMAdjuncts:2SixPhotomacrographs3.Apparatus3.1EtchingContainers—Macroetchingmaybeperformedinavesselofborosilicateglass,porcelain,corrosion-resistantmetals,orsomeotheracid-resistingmaterial.4.Reagent4.1EtchingReagent—Asolutionofequalvolumesofcon-centratedhydrochloricacid(HCl,spgr1.19)andwateriscommonlyusedformacroetchingtoolsteels.ThissolutionmustbeusedunderaventilatinghoodbecauseHClisvolatileandthefumesarecorrosiveandirritating,althoughnontoxic.Thesolutionmaybereusedwithinlimits.Withuse,theconcentrationofdissolvedironandothermetalsincreasesandtheacidityofthesolutiondecreasesretardingtheetchingaction.Spentsolutionshallbereplacedwithfreshsolution,notreplenishedwithconcentratedacid.5.Sampling5.1Theselectionofspecimensformacroetchtestingmustbedonewithcareforinterpretationstobeofvalue.5.1.1Specimensareusuallycutfromhot-rolledannealedbars,butmaybecutfrommachinedorgroundbarsifthebarsaretobefinishmachine...
