ASTM E1251-94铝和铝合金分析

3.2.2standardization—SeeTerminologyE135.Twotypesofstandardizationarecommonlyused,asfollows

3.2.2.1two-pointstandardization——adjustmentofagaincontrolofachannelforanindividualspectrallineinamannerthatreproducesthereadingsthatthehighandlowstandardantsdisplayedduringthecollectionofcalibrationdata.Incomputerapplications,correctionisdonemathematicallybyapplyingaslopeandinterceptcorrection,thatis,amultiplicationtocorrecttheamountofdifferencebetweenthehighandlowstandardantreadingsfollowedbytheadditionorsubtractionofaconstanttofinallyrestorereadingstoexpectedvalues.

3.2.2.2single-pointstandardization—adjustmentofachan-nelforanindividualspectrallineusingasinglestandardant.Usuallythesinglestandardantisahighreferencematerialusedtosetthegain.Iftheanalyticalinterestisjustinlowconcentrationsnearthedetectionlimit,alowstandardantisusedandeitheragainorabackgroundcontrolmaybeadjusted.

4.SummaryofTestMethod

4.1Aunipolarself-initiatingcapacitordischargeispro-ducedinanargonatmospherebetweenapreparedflatsurfaceofthespecimenandthetipofasemi-permanentthoriated-tungstenorothercounterelectrode.Theradiantenergiesofselectedanalyticallinesandaninternalstandardlineareconvertedintoelectricalcurrentsbyphotomultipliers.Thecurrentsareintegratedduringtheexposuretimeeitherbychargingintegratingcapacitorsandmeasuringthecumulativevoltagesattheendoftheexposure,orbyinterrogatingthecapacitorsduringtheexposureandconvertingthevoltagesintodigitalcountsbymeansofacomputer.Theratiosofthevoltagesoftheanalyticallinestothevoltageoftheinternalstandardlineareconvertedintoconcentrationseithermanuallybygraphs,tables,orX-Yrecorders,orbyacomputerinaccordancewithPracticeE158.

4.2Twoalternativeproceduresforcalibrationmaybeem-ployed.Thetwoprocedurescangivethesameprecision,accuracy,anddetectionlimits.

4.2.1Thefirstprocedure,BinaryCalibration,isusedwhenthereisaneedtoanalyzealmosttheentirerangeofaluminumalloys.Thisprocedureemployscalibrationcurvesforeachelementthatcovertheentireconcentrationrangethathastobedeterminedinallalloys.Fiftyormorebinarycalibrantsmayberequiredforcalibration.Typereferencematerialsareusedtoadjusttheconcentrationsreadfromthebinarycurvesinordertoreportthecorrectconcentrationsforspecificalloys.

4.2.2Thesecondprocedure,Alloy-TypeCalibration,ismoreappropriateforanalyzingonlyarelativelyfewalloysofsimilarcomposition.Itemploysananalyticalcurveforeachelementthatcoversarelativelylimitedconcentrationrange.Calibrationmayrequireonly5to20calibrants.

5.SignificanceandUse

5.1Thephysicalandchemicalpropertiesofhigh-purityaluminumandaluminumalloysdependonchemicalcomposi-tion,whichmustbedeterminedandcontrolled.Accurate,high-speedanalysisofaluminum,beforeitispouredfromthefurnace,canpreventscrappedheatsandminimizethecostofexpensivealloyingmetals.

5.2Thistestmethodisapplicabletochill-castspecimenspreparedforroutineproductioncontrol.Itcanbeappliedtoothertypesofspecimensifthereareappropriatereferencematerials,orifthespecimensareremelted.6.Interferences6.1KnownlineinterferencesduetootherelementsarelistedinTable1.TABLE1AnalyticalLinesandConcentrationRangesWavelengthInAir,˚A,B,CAI2881.58I2516.12I3905.53BI2124.15II2382.04II2599.40I2599.57I3749.49BI4415.12I4383.55I3273.96I2961.17II2247.00I5105.I4030.76BII2593.73II2933.06II3460.33BII2795.53I2852.13I2776.69I3832.31BI5183.62RecommendedConcentrationRange,%0.001–1.50.001–1.50.05–240.05–240.001–1.50.001–1.50.001–3.50.01–3.50.005–3.50.001–1.50.05–200.01–50.05–200.001–20.0005–0.50.001–20.01–20.0005–0.30.0005–0.30.05–110.01–110.01–11BackgroundEquivalent,%D0.010.0060.250.50.0150.005DetectionLimit,%E,F0.00010.00010.010.050.00080.00040.0001I0.00040.050.0050.400.030.320.0280.0040.0060.00060.0080.080.0150.02<0.00010.01F0.0005F0.01F0.0001F0.000050.0002F0.00003<0.00010.010.002F0.002F0.7>205>200.2>1.10.040.25>11>11>11Fe2961.28High-ConcentrationIndex,%G1.51.5>24>241.0Interferences˚,andk,%HElement,l,ACr2881.93Cr3905.660.09ElementSiliconIronCopperManganeseMagnesiumElement

WavelengthInAir,

˚A,B,CAI42.35II2677.16II2766.I3414.76I3101.88

II2316.04(2nd)I2138.56(2nd)I3345.02I4810.53I4722.16II3349.04II3372.80I3635.45I3183.41II3102.30I4057.82I2833.06I3175.02I3067.72I2943.I4172.06BI2497.73(2nd)I20.59(2nd)I2348.61II3130.42I3321.34I58.95II3933.67BII3391.98II3496.21BI3453.51BI2288.02I4799.92I6707.84I3232.61I2311.47(2nd)I2598.06II4215.52BII45.04I1782.31(2nd)I,JI3280.68I3382.I4668.48I2567.99I2660.39I2372.08RecommendedConcentrationRange,%0.001–10.001–10.005–10.001–20.005–40.001–20.0005–0.10.001–10.00.01–100.01–100.0005–0.50.001–0.50.0005–0.050.001–0.150.001–0.150.002–0.70.002–0.70.001–7.50.001–0.70.001–0.050.001–0.050.0001–0.050.0001–0.050.0001–0.050.0005–0.050.0001–0.050.0001–0.050.001–0.050.001–10.001–10.0001–20.001–0.30.005–20.0001–0.020.01–30.001–0.50.001–0.50.0001–0.10.0001–0.10.0001–0.10.0005–0.10.0001–0.10.05–1.570–10070–10070–100BackgroundEquivalent,%D0.0150.0040.020.050.0150.0350.0650.070.260.0040.0020.0300.060.0140.040.070.040.040.0150.002

DetectionLimit,%E,F<0.00010.0005F<0.00010.001F0.0005F0.0001F0.00040.001F0.0015<0.0001<0.00010.0003F0.0003F<0.00010.00010.0020.00010.0002<0.00010.0001FHigh-ConcentrationIndex,%GInterferences˚,andk,%HElement,l,A

Chromium

Nickel

Zinc

>2.5

>5<2.50.05>8>10>10

Titanium

VanadiumLeadTin

BismuthGalliumBoron

Mn4057.92

>10

0.01

Fe2497.82Mn2497.78Mo20.520.0010.0070.13

Beryllium

0.0010.00350.00150.0010.020.0060.050.150.00050.170.00040.00040.084SodiumCalciumZirconiumCobaltCadmiumLithiumAntimonyStrontiumBariumPhosphorousSilver0.000030.00010.0001<0.00010.000050.001F<0.0001<0.0001<0.00010.003<0.000050.00020.00020.00010.00010.0001>10Fe3933.61

As2288.12Sb3232.50Fe3232.79Co2311.66Fe2598.370.6AluminumI5atomline,II5ionline.UsefulanalyticallineswithimprovedsignaltobackgroundratiosduetothecompleteremovalofC-Nbackgroundbytheargonatmosphere.CSecond(2nd)indicatesthatthesecondordershallbeused,whereavailable.DBackgroundEquivalent—Theconcentrationatwhichthesignalduetotheelementisequaltothesignalduetothebackground.EInthistestmethod,thedetectionlimitwasmeasuredbycalculatingthestandarddeviationoftenconcentrationprintoutsofaspecimenbetweenthreeandtentimestheexpecteddetectionlimit.FSeefootnoteE.ForthevaluesmarkedwithanF,theavailabledatawasforaconcentrationgreaterthantentimesbutlessthan100timestheexpecteddetectionlimit.GHigh-ConcentrationIndex—Theconcentrationatwhichthetangenttothecalibrationcurveplottedonlog-logpaperdropsfrom45°theoreticalto37°,thatis,theresponseofIa/Isasordinateversus%aasabscissahasdroppedfromapproximately1.0to0.75.Itisrecommendedthatasecond,lesssensitivelinewithcloseto45°responsebeemployedbeforethisconcentrationisreached.HInterferenceFactor,k—Theapparentincreaseintheconcentrationoftheelementbeingdetermined,expressedinpercent,dueto1.0%oftheinterferingelement.IThedetectionlimitforironisdeterminedmorebypossiblesegregationinthespecimenandbycontaminationduringmachiningthanbyspectrochemicalsensitivity.J˚inthesecondorderandthisrequiresavacuumspectrometer.OptimumresultsIfphosphorousistobedetermined,themostsensitivelineappearstobe1782.31A˚inthefirstorder.TheratioofP1782.31Aareobtainedbyusingasaninternalstandardabackgroundchannelprofiledoffthepeakofphosphorous1782A˚(2nd)/backgroundnear1782A(1st)isplottedagainst%P.Evenwiththiscompensationforvariabilityinbackground,alloyswithhighlydifferentcompositionsofmajoralloyingelements,particularlysilicon,requireseparatereferencematerialsandanalyticalcurves.

BA7.Apparatus

7.1SpecimenPreparationEquipment:

7.1.1SpecimenMoldsforaluminumandmethodsforpouringspecimensaredescribedinPracticeE716.Chill-castspecimens,pouredasdescribedtherein,shallbeusedinthistestmethod.

7.1.2Lathe,capableofmachiningasmooth,flatsurfaceonthereferencematerialsandspecimens.Avariable-speedcutter,

acemented-carbidetool,andanautomaticcross-feedarerecommended.

7.1.3MillingMachine—Averticalmillingmachinewithfly-cutterandviseforholdingthespecimencanbeusedasanalternativetothelathe.

7.2ExcitationSource,capableofproducingaunipolarself-initiatingcapacitordischarge,utilizingtheparametersdescribedin13.2orequivalent,andinaccordancewithPracticeE172.Eachhigh-frequencywavetrainisfullyrecti-fied,sothatthespecimenisalwaysthecathode,andonlyspecimenmaterialisintroducedintotheanalyticalgap.Thecounterelectrodeisnotattacked,andcanbeusedforanalyzingmanyspecimens.

7.3ExcitationChamber,similartothatshowninFig.1,formountingamachined,flatsurfaceofthespecimensothatitformsasealtoexcludeatmosphericoxygenfromthedis-charge.Theexcitationchambershallbeprovidedwithacounterelectrodeholderandwithaclamptoholdthespecimenfirmlyagainsttheupperplate.Theupperplateshallbeinclinedatanangleof10to15°tothelightpath.Dependinguponthemanufacturer,theexcitationchambermayrequirewater-cooling,oradiaphragmmaybeinsertedinthechambertooccludeanyradiationfromthehotspecimenorthecounterelectrode,orbothmayberequired.Theexcitationchambershallbedesignedsothatitcanbeflushedautomaticallywithargongas.Argongasshallbeintroducedjustinsidethefusedquartzwindow,flowingtowardthedischarge,topreventanyofthemetalpowderproducedatthedischargefromcoatingtheinsideofthewindow.Argonalsomaybeintroducedaroundthecounterelectrode,buttheflowrateshallnotconfinethedischargetoanarealessthan5mmindiameter,toprovideadequatesamplingofthespecimen.Theargon,withmostofthemetaldust,shallbeexhaustedtotheatmospherefromthebackorsideofthechamber.

7.4GasFlowSystem,tosupplypureargongas(99.995%)totheexcitationchamber.ThegasshallbedeliveredbyaflowsystemasdescribedinPracticeE406fromeitherhigh-puritycompressedgas,orliquidargonbottles,orfromawelding

FIG.1ExcitationStand

gradesupplythathasbeenpurifiedtotherequired99.995%level.Thesystemshallinclude:atwo-stageregulatorofall-metalconstructionwithtwopressuregages;coppertubingwithall-metalseals;asolenoidandvalveoperatedautomati-callybythecontrolsystem,tostartthefullargonflowforthepre-flushandstopitattheendoftheexposure;andaneedlevalvetomaintainaveryslowbleedofargonthroughtheexcitationchamberwhenitisnotinactiveuse(Note1).Thecoppertubingshallbekeptasshortaspossible—preferablyonlyafewfeet.Allconnectionsshallbeleak-free.Aflowgageisrequiredtochecktheflowrates.Theflowgageneednotbeincorporatedinthesystempermanently,butmaybeconnectedattheoutlettemporarilywhileinitiatingadjustingtheoperatingflow,andthencanberemoved.Thiskeepsthesystemassimpleaspossibleandeliminatesapossiblesourceoforganiccon-taminantsorleaks.

NOTE1—All-metalconnectionsarerequiredbecausethedischargeisadverselyaffectedbyorganiccontamination,orbyaslittleas2ppmofoxygenorafewppmofwatervapor.

A

˚7.5Spectrometer,withareciprocallineardispersionof10/mm,orbetter,andacombinationofentranceandexitslitwidthsthatprovidesaworkingresolutionofatleast0.7A

˚(Note2).Thewavelengthcoveragemustincludetheanalyticallinesrequiredfortheneededconcentrationranges,aslistedinTable1.

NOTE2—AccordingtoPracticeE380,theAngstrom,A

˚,isadeprecatedunit.However,itisemployedherefortheconvenienceoftheusersofthistestmethodwhomaywishtorefertothewavelengthtableswhichcontainAngstromunits.AnAngstromisdefinedas0.10ofananometre.

NOTE3—Ifphosphorusistobemeasured,theoptimumlineis1782A

˚,whichisstronglyabsorbedbyoxygen;therefore,avacuumspectrometerisrequired,operatingatapressureof25microtorrorless.

NOTE4—ThebackgroundequivalentsanddetectionlimitslistedTable1canbeattainedwithareciprocallineardispersion˚in

/mmandaworkingresolutionof0.35A

˚of5.4A

,usinganentranceslitwidthof25µmandanexitslitwidthof50µm.

7.6MeasuringSystem,consistingofphotomultipliershav-ingindividualvoltageadjustments,integratingcapacitors,ordigitalcountingcircuitry,anamplifierandsomeformofreadoutsystem.Thesystemalsomaycontaintheprogramcircuitrythattimestheflush,pre-burnandexposureintervals,turnsthesourceonandoff,etc.Themeasuringsystemmayreadonlyintensityratios(voltageratios),whichthenhavetobeconvertedintoconcentrationsmanually,orthesystemmayuseacomputerorprogrammablecalculatortoconvertintensityratiosintoconcentrations.

7.6.1ManualMeasuringSystem,withanindividualvoltageoramplifiergaincontrolandazeroadjustmentcontrolforeachchannel,topermitstandardizationasrequired.Note5

NOTE5—Thegainandzerocontrolscanbeomittediftheanalyticalprogramisrestrictedtoafewalloytypes,theconcentrationrangesineacharerestricted,andthegainandbackgroundlevelsdonotvarywidelyfromdaytoday.Thensomemechanismforsinglepointstandardization,suchasacalculatingboardwithmovableconcentrationscales,maybeusedtocompensateforinstrumentaldrift.

7.6.1.1IntensityReadoutSystem,whichdisplaystheratiooftheradiantenergyoftheanalyticallinetotheradiationoftheinternalstandardline,eitherasadigitalnumberreadvisuallyortypedautomatically,orasadeflectiononastripchart

recorderorX-Yrecorder.

7.6.1.2Graphs,FlipCharts,orCalculatingBoards,usedinconjunctionwithanintensityreadoutsystem,toconvertdigitalintensityratiosintoconcentrations.WithastripchartorX-Yrecorder,concentrationscalesmaybepreprintedonthepaper,asillustratedinTestMethodE227.

7.6.2ComputerReadoutSystemorProgrammableCalcu-lator,whichstorestheanalyticalcurvesinmemoryandconvertstheintensityratiosintoconcentrations(seeX1.1ofAppendixX1).Aprintoutoftheanalysisisrecommendedbecauseitprovidesapermanentrecordandeliminatesclericalerrors,butdisplayofresultsonavideoscopeisacceptable.Manualadjustmentsarenotneededduringstandardizationbecausegainandbackgroundadjustmentfactorscanbecalcu-latedautomatically.

8.Materials

8.1CounterElectrode—Thepreferredcounterelectrode,consistingofaneedle-pointthoriated-tungstenwiremountedinacopperrod,isillustratedinFig.2(a).Analternativecounterelectrode,a6.3-mmdiametertungstenorsilverrodwithaconicaltip,isillustratedinFig.2(b).

8.2ArgonGas,of99.995%purity.Cylindersofeithercompressedargongasorliquidargonmaybeemployed.Alternatively,argongasoftherequisitepuritycanbeproducedfromaweldinggradesupplybypassingitthroughatitaniumfurnacewhichremovesoxygen,nitrogen,water,andoilva-pors,andotherimpurities.SeePracticeE406forprecautionstobeusedinhandlinggases.

NOTE6—Amagnesiumfurnaceisnotacceptablebecauseitwillintroducevariablemagnesiumcontamination.

9.ReferenceMaterials

9.1Calibrantsshallbehomogeneousandfreeofcracksorporosity,withametallurgicalconditionsimilartothatoftheunknownspecimenstobeanalyzed.Theyshallbeusedto

(a)Needle-Point,Thoriated-Tungsten

(b)TungstenorSilverRodwithCon-WireMountedinCopperRodicalTip

FIG.2CounterElectrodes

producetheanalyticalcurvesforvariouselementsbeingdetermined.

9.1.1Ifanalloy-typecalibrationstructureisused,itisdesirabletohaveatleastfourcalibrantsforeachelement(see3.2.1).Theconcentrationsshouldbefairlyevenlyspacedovertheanticipatedanalyticalrange,toestablishastatisticallysoundsmoothcurvethroughallpoints.

9.1.1.1Ifanalyticallinesaretobeusedabovetheconcen-trationsatwhichtheymaystarttoself-absorb,itisnecessarytohavemorecalibrationreferencematerialsintheself-absorbedregion,todefinetheshapeofthecurve.

9.1.2Thecompositionofthecalibrantsshallhavebeendeterminedchemicallyatleasttotheaccuracyrequiredforthefinalanalyticalresults.AfewbenchmarkCertifiedReferenceMaterialsareavailablefromtheNationalInstituteofStandardsandTechnology5andmanyotherreferencematerialsareavailablecommerciallyinbothchill-castandwroughtforms.69.1.3Forseveraltraceelements,availablereferencemate-rialscontainvariableconcentrationsofthetraceelementinatypicalalloyofconstantcomposition.Thesereferencemateri-alscanbeusedforestablishingananalyticalcurve,butwillnotrevealpotentialinterferencesfromnearbylinesofotherelements,ormatrixeffectsthatchangethebackgroundorresponse.Foroptimumusefulness,severalofthecalibrantsshouldhaveconcentrationsoftheotherelementsthatcovertherangestobeexpectedintheunknownspecimens.

NOTE7—Fortunatelywithaluminum,therearerelativelyfewinterfer-encesbecausethealuminumspectrumitselfandthespectraofthemajoralloyingelements(silicon,copper,magnesium,zinc,andtin)aresimple.Thealloyingelementswithcomplexspectra(nickel,manganese,iron,cobalt,chromium,zirconium,titanium,andvanadium)arepresentatconcentrationssolowthatonlythemoreintenselinescancauseinterferences.

NOTE8—Referencematerialsandspecimensmodifiedwithsodiummayproduceblackerburnswithdeeperpenetrationofthesparkintothesurface.Thismayresultinadropintheintensityofthealuminuminternalstandardbelowitsnormallevel,andacorrespondingincreaseintheintensityratiosfortheanalyticallines.This,inturn,mayproduceconcentrationreadingsforsiliconthataretoohighby0.3%atthe5%to7%level,andasimilarincreaseforotherelements.Ifnonmodifiedspecimensaretobeanalyzedwithcalibrationcurvesestablishedwithmodifiedreferencematerials(orviceversa),correctionsforsucheffectsshallbeapplied.

9.2Standardants:

9.2.1High-ConcentrationStandardants—Thesemaybeselectedcommerciallyavailablereferencematerialsor,prefer-ably,referencematerialspreparedin-house,thathavebeentestedforhomogeneityandhaveamongthemconcentrationlevelsnearorabovethemedianconcentrationforeachelement.Asinglestandardantforeachmatrixispreferable,butseveralmaybeused.Theexactcompositionneednotbeknown,sincethestandardantsshallbeusedonlytoadjusttheinstrumenttoreproducetheintensityratioswhichtheypro-ducedatthetimetheanalyticalcurveswereestablished.

5OfficeofStandardReferenceMaterials,NationalInstituteofStandardsandTechnology,U.S.DepartmentofCommerce,Gaithersburg,MD209.6AluminumreferencematerialsareavailablefromAluminumCompanyofAmerica,TechnologyMarketingDivision,18thFloor,AlcoaBuilding,Pittsburgh,PA15219,andAnalyticalReferenceMaterialsInternational,Inc.,P.O.Box2246,Evergreen,CO80439-2246.

9.2.2High-PurityorBlankStandardants—Theseshallbehomogeneous,withthelowestavailableconcentrationsoftheelementsbeingdetermined,buttheirexactcompositionsneednotbeknown.Usually,thebackgroundreadingsofaspectrom-eterremainrelativelyconstant.Therefore,ablankstandardantforanelementdoesnotneedtobeusedinroutinestandard-izationunlessthelowestconcentrationthatneedstobedeterminediswithintentimesthedetectionlimitofthatelement.Forspecimenswithsuchlowconcentrations,singlepointstandardization,eitherwiththeblankoranotherspeci-men,maygivemoreconsistentresults.

10.SafetyPrecautions

10.1Allhigh-voltagesourcescangivepainfulshocksiftheoperatingpersonnelcomeincontactwiththehighvoltagewhenthesourceisturnedon.Theexcitationchambershallbeenclosedandshallbeprovidedwithasafetyinterlocksothatthesourcecannotbeturnedonuntilthedoorisclosed.Accesstothepowersupplyshallbepermittedonlybyremovingpanelswhichcontainsafetyinterlocksorrequiretheuseoftools.10.2Fumesoffinemetallicpowdersexhaustedfromtheexcitationchambercanbepoisonousifspecimenscontainsignificantlevelsofheavymetalssuchascadmiumorlead.Suchmetalsshallbetrappedbybubblingtheexhaustthroughwaterorafiltersystem,ortheexhaustshallbeventedtotheatmosphereatanonhazardouslocation.

11.Sampling

11.1Forthesamplingofmoltenaluminummetalandthecastingofdiskspecimens,seePracticeE716.12.PreparationofReferenceMaterialsandSpecimens12.1PreparationofReferenceMaterials—Thereferencematerialshallbemachinedinthesamemannerasthespeci-mens.12.2PreparationofSpecimens—Forthepreparationofchill-castdiskspecimensandothertypesofaluminumspeci-mens,seePracticeE716.NOTE9—Foroptimumprecisionandaccuracy,thereferencematerialsandspecimensshallhavebeenfreshlymachinednolongerthan1hbeforeuse,toavoidtheformationofaluminumoxide.13.PreparationofApparatus

13.1Prepareandoperatethespectrometerinaccordancewiththemanufacturer’sinstructions.

NOTE10—Itisnotwithinthescopeofthistestmethodtoprescribeminutedetailsrelativetothepreparationoftheapparatus.Foradescrip-tionandspecificdetailsconcerningtheoperationofaparticularspectrom-eter,refertothemanufacturer’smanual.

13.1.1Programthespectrometertoaccommodatetheinter-nalstandardlineorlines(orbackgroundsettings)andthepertinentanalyticallineslistedinTable1.Connectthephoto-multipliers,capacitors,andrelatedmeasuringsystem.

NOTE11—Theargonatmosphereeliminatesthemolecularbandsofcyanogen(CN)thatareproducedwithexcitationsinair(seeTestMethodE227)ornitrogen(seeTestMethodE607).TheabsenceofCNbandsprovidesimprovedsignaltobackgroundratiosforsomeanalyticallinesandpermitstheuseofotherlines.ThelineslistedhaveprovensatisfactoryfortheelementsandconcentrationrangesprescribedintheScope.Otherinternalstandardandanalyticallinesmaybeused,provideditisshownthattheresultsobtainedarecomparable.

13.1.2Profilethespectrometerinaccordancewiththemanufacturer’sinstructions(see13.1).

13.1.3Positionortestthepositionofthespectrometerexitslits,secondarymirrors,ifused,andphotomultiplierstoensurethatthepeakradiationpassesthrougheachslitandilluminatesthecentersofthephotomultipliers.Thisshallbedoneinitiallyandasoftenasnecessarythereaftertomaintainproperalign-ment.

NOTE12—Moderndirect-readingspectrometersshouldshowlittledriftintheresponseofchannelswithtime.However,ifatanytimethegainadjustmentofanychanneldropsbelow0.5orincreasesabove2,orifthebackgroundreadingchangesmorethan0.5to23,thatchannelshouldbecheckedforalignmentordeteriorationofcomponents.Itisrecommendedthatallgainsandbackgroundsbechecked1monthafterinstallationandthereafteratleastonceayearasaformalinspectionprocedure.13.2ElectricalParameters—Varioussetsofelectricalpa-rametersinarectified-capacitordischargesourceproducesomewhatsimilarhigh-frequencyoscillatoryunidirectionalwaveforms.Thesehavebeenfoundtogivecomparableana-lyticalperformance.Useoneofthesetsofelectricalparam-etersgiveninTable2.13.3TypicalExposureConditions—ExposureconditionsTABLE2ElectricalParametersA-1Secondaryrmsvoltage,VPeakvolts,VSecondarycapacitance,µFMaininductance,µHRectifyingbridgeinductance,µHResistanceinserieswithgap,VBreakdownvoltageofgap,VR-fcurrent,APeakcurrent,ADischarges/s(60;supply)20000A-220000B-1...B-2...Preburn...C-1HighAlloys...9500.555........................100120C-299+%...Al0.01030015residual135004.22400.01521020residual135004.624010100/200...2.2......120101000/2000...2.2......1207550.255............275120willdependonthespecificequipment,andatradeoffthattheindividuallaboratoryselectsbetweenspeedofanalysisandslightlyimprovedprecisionandaccuracywithlongertimes.Typicaltimerangesare:

Flushperiod,s2to7Preburnperiod,s2to10Exposureperiod,s

5to20

13.4GasFlow—Gasflowrateswillvaryfromlaboratorytolaboratory,butshallbeinthefollowingranges:

Standby,L/min0.05to0.09(standardft3/h)

(0.1to0.2)Duringexposure,L/min4.5to8(standardft3/h)

(9to15)

Thecompressedargongas2cylindershallbereplacedwhenthepressurefallsto7kgf/cm(100psi).SeePracticeE406forprecautionstobeusedinhandlinggases.

13.5ElectrodeSystem—Positiontheflat,preparedsurfaceofthespecimenonthetopoftheexcitationchambersothatthedischargewillimpingeonthearealyingatleast5mmfromtheedgeofthespecimen.Thespecimenshallsealthe8to15mmopeninginthetopoftheexcitationchamber.Thespecimenservesasoneelectrode,thecathode.Mountthecounterelectrodeoppositethespecimen.Useonlyonetypeofcounterelectrodeformeasurementsonallreferencematerialsandspecimens.Theunidirectionaldischargedoesnotattackthecounterelectrode,sothatitcanbeusedformanyburnsbeforerefinishingorreplacementisnecessary.Adjustthecounterelectrodetoprovideananalyticalgapof3.060.1mm.

NOTE13—Physicallycleaningthecounterelectrodeaftereachexpo-sure,usingamotor-drivenwirebrush,canprolongthetimebeforeamajorcleaningorreplacementisneeded.

NOTE14—Itisessentialthattheoperatorlearnstodistinguishbetweengoodburnsandbadburns,whichareusuallyduetoanairleakbetweenthespecimenandthetopoftheexcitationchamberorsometimestoairincludedinacrackinthespecimen.Agoodburnwillhaveadeeplypittedareainthecenter,surroundedbyablackishring,usuallywideroppositetheargoninlet.Abadburnwillhaveshallowpittings,surroundedbyawhitishorsilveryring.Rejectallbadburns.

13.5.1Exceptforthefewsecondsrequiredtochangespecimens,theopeninginthetopoftheexcitationchambershallbecoveredwithascrapspecimenorothersealatalltimes.

NOTE15—Whentherelativehumidityisgreaterthan80%,anexcita-tionchamberleftuncoveredforseveralminutesmayhavetobeflushedforaquarterofanhourormorebeforeexcitationswillreturntonormal.

13.6Warm-Up—Afteranyprolongedintervalsofnonuseoftheinstrument,warmupthesource,excitationchamber,andgasflowsystembyburninganexpendablespecimenuntilrepeatablereadingsareobtained.

14.Calibration

14.1ObtainingCalibrationData—Thefollowingproce-dureisdesignedtominimizetheeffectsofanypossibleinstrumentaldriftontheconsistencyofthedatausedforpreparinganalyticalcurves.SeeAppendixX1foradditionalinformationconcerningtheacquisitionofcalibrationdata.14.1.1Profileandwarmuptheinstrument.

14.1.2Normalizetheinstrumentfortheelementstobecalibratedwiththefirstfiveorsixcalibrants,usingatleastsix

andpreferablyeightburnsforeachstandardizationreferencematerial.Thenburneachcalibrantfourtimes.Burnthestandardantsforthenextfiveorsixcalibrants.Normalizeforanyelementthathasshownadriftgreaterthan2s(asmeasuredinNote18),orforanyelementnotcoveredbythefirstnormalization.Burnthenextfiveorsixcalibrants.Repeattheprocessofburningthestandardants,normalizingwhereappro-priate,andburningthenextfiveorsixcalibrants,untilallcalibrantshavebeenburned.

14.1.3Repeattheproceduredescribedin14.1.2,exceptburnthecalibrantsinthereverseorder.

14.1.4Repeattheproceduredescribedin14.1.2,exceptthistimestarteachgroupoffiveorsixcalibrantswiththethirdorfourthcalibrantinthatgroup.

14.1.5Repeattheproceduredescribedin14.1.2,exceptburnthecalibrantsinthereverseorderstartingeachgroupoffiveorsixcalibrantswiththefourthorthirdcalibrantinthatgroup.

14.1.6Averagetheintensityratioreadingsforallsixteenburnsofeachcalibrant.

NOTE16—Normalizingtheinstrumentwhileburningthecalibrantshasbeenhelpfulinestablishinganalyticalcurvesthatwillprovideconcentra-tionsaccuratetobetterthan1%ofthestatedvalueforconcentrationsabove1%.Itisnotrequirediflessaccuracyisacceptable.

14.2CalibratingtheInstrument:

14.2.1Foraninstrumentwithamanualreadout,foreachelementplotthemeasuredintensityratioreadingsagainstthestatedconcentrationsorconcentrationratios.Drawtheopti-mumtheoreticalanalyticalcurvethroughtheplottedpoints.RefertoPracticesE158andE305forguidance.

14.2.1.1Usethesecurvestopreparetheflipcharts,calcu-latingboards,orcalibratedstripchartsorX-Yrecordersthatwillbeusedtoconvertintensityratiosintoconcentrations.14.2.1.2Foraninstrumentwithacomputerorprogram-mablecalculatorthatrequiresthemanualdrawingofanalyticalcurves,followthemanufacturer’sinstructionstomaketheappropriateentries.

14.2.2Foraninstrumentwithacomputerthatcalculatestheanalyticalcurvesfromthemeasuredintensityratiosandthestatedconcentrationsorconcentrationratios,followthemanu-facturer’sinstructionstoenterthedataandobtaintheanalyticalcurves.

14.2.2.1Withsuchacomputer,particularlyifthesoftwarepermitsuseofafourthorhigherpowerpolynomial,recognizethataccurateanalysisofunknownspecimensrequiresmorethanareportofagoodfitbetweenthecalculatedandstatedconcentrationsforthecalibrationreferencematerials.Thecomputermayhavecalculatedacurvethatweavesinandoutbetweenthepointsforthecalibrants.Withsuchacurve,seriouslyerroneousanalysesmaybeobtainedforunknownspecimenswithconcentrationsbetweenthecalibrants.Ifthecomputerhasagraphicsfeature,useittoplotthecurveithascalculated;otherwise,plotmanuallythecurvesthecomputerhascalculatedtoensurethattheyaretheoreticallycorrect.RefertoPracticeE158.

14.3VerifyingtheAccuracyofCalibration—Standardizetheinstrumentandreburnthecalibrantsasunknownsandcomparethemeasuredconcentrationswiththestatedvalues.

Checkforandcorrectclericalerrorsandbiases.

14.3.1Ifindividualcalibrantsgiveconsistentlyhighread-ingsforanelement,checkforpossibleinterferencesfromotherelements.CalculateandenterappropriatecorrectionfactorsinaccordancewithPracticeE158.

15.Standardization

15.1PreparationforStandardization—Allfutureaccuracyofanalyseswilldependonself-consistentintensityratioreadings,freefromdriftwithtime,forallthereferencematerialsusedforcalibration.Therefore,theinstrumentshallbenormalizedasneededwhilethecalibrationdataarebeinggenerated(seeAppendixX1).

NOTE17—Unfortunately,directreadersareusuallycalibratedshortlyaftertheyhavebeeninstalledinthelaboratory.Usuallytheyhavenotyetbecomeasstableastheywillbeafteramonthorso,andconsequently,thereadingsobtainedmayshowsignificantdrift.Theprocessofcalibrationwillprobablytakeseveraldays.Accordingly,tocorrectfordrift,itisessentialtoselectprospectivestandardantsanddeterminetheiruniformitybeforestartingthecalibrationprocess.

15.2CheckingHomogeneityoftheStandardants—UsingtheconditionsgiveninSection13,burnthestandardantsselectedinaccordancewith9.2atleasttentimeseachandpreferablysixteentimes.Therelativestandarddeviationsoftheinternalstandardintensitiesshallbelessthan1.5%,whiletherelativestandarddeviationsoftheintensityratiosoftheanalyticallinesdividedbytheinternalstandardshallbelessthan1%(Note18).Ifoneormoreofthestandardantsdonotmeetthesecriteria,thisisanindicationthattheyarenotsufficientlyhomogeneous.Selectalternativereferencemateri-alsandqualifythem.

NOTE18—Thestandarddeviation(s)andtherelativestandarddevia-tion(RSD%)arecalculatedasfollows(seePracticeE876):

s5

Œ(d2n21(1)

where:

d5differencebetweenindividualmeasurementsandthe

mean,and

n5numberofindividualmeasurements.

RSD%5100

X

¯s

(2)

where:

X

¯5theaverageoftheindividualmeasurements.15.3NumberofStandardizationBurns—Itisrecommendedthatthenumberofburnsofthestandardantsbeatleasttwicethenumberofburnsforthereferencematerialsorspecimens

thatarebeingstandardized.Forunknownspecimenswhereusuallytwoburnsareused,thismeansatleastfourburnsofthestandardants.Duringcalibration,eightburnsofthestandar-dantsarerecommended.

15.4RecordingorEnteringtheStandardizationReadings:15.4.1Forreadoutsystemsthathavetobestandardizedmanually,recordtheaveragereadingsforeachelement.

15.4.2Forcomputerreadoutsystems,enterthehighandlowreadingsintocomputermemory.

16.ProcedureforAnalyzingSpecimens

16.1Excitation—Burnthespecimensinaccordancewiththeconditionsgivenin13.2-13.5.

16.2ReplicateBurns—Burnthespecimensonetofivetimes,dependinguponthehomogeneityofthemetalandtheconfidencelevelrequired.Asingleburnfrequentlyisemployedforprimaryaluminumorforlow-concentrationalloys,wherethespecimensusuallyarehomogeneous.Twotofourburnsarerecommendedformostalloys,wherehomogeneityisfairandaccuracybecomesimportant.Inalloysthatarenotedforsegregation,asmanyasfiveburnsmaybeneeded.

16.2.1Thedeterminationsfromallburnsshouldbeaver-agedunlessaburnproducesareallyabnormalinternalstandardcount,orappearsvisuallytobebad(thatis,havingasilveryratherthanablackishringsurroundingthepittedarea).Whenaburnisrejected,itmaybereplacedwithanotherburninordertomaintainthenormalnumberofburnstobeaveraged.17.CalculationofResults

17.1Ifthereadoutismanual,recordtheintensityratiosandconvertthemintoelementalconcentrationsfromtheanalyticalcurves,flipcharts,acalculatingboard,orpreprintedconcen-trationscales.Ifacomputerreadoutisavailable,readorprinttheconcentrationsdirectly.

18.PrecisionandBias18.1Precision:

18.1.1Repeatability—Precisiondatabasedontensucces-sivemeasurementsonasinglereferencematerialwithinonelaboratoryaregiveninTable3forsomeoftheanalyticallines.18.1.2Reproducibility—Testingforprecisionbetweenlabo-ratoriesiscurrentlybeingconducted.

18.2Bias—Interlaboratorytestingforbiasiscurrentlybe-ingconducted.

19.Keywords

19.1aluminumandaluminumalloys;analysis;spectro-chemical;spectrochemicalanalysis

TABLE3PrecisionData(Repeatability)

ElementSiliconWavelengthinAir,AAI2881.58I2516.12I3905.53I2124.15II2382.04I2599.57II2599.40I3247.I3273.96I5105.I2961.17II2247.00I4030.76II2593II2933.06II2795.53I2852.13I2776.69I3832.31I5183.62I42.35II2677.16I3414.76II2316.04(2nd)I2138.56I3345.02I4810.53I4722.16II3349.04II3372.80I3635.45I3183.41II3102.30I4057.82I3175.02I3067.72I2943.I2497.73I2348.61II3130.42I58.95II3933.67II3391.98II3496.21I2288.02I6707.84I3232.61I2311.47(2nd)I1782.31(2nd)LowConcentrationConcentration,%0.0050.0051.10.0520.200.100.00340.0010.50RSD,%B8.69.10.963.01.21.53.07.91.7HighConcentrationConcentration,%1.21.211.311.31.20.604.84.84.80.00150.100.0350.0010.150.201.60.00120.00190.0390.100.0010.00230.0030.0280.00370.040.00570.00180.040.0010.0150.00020.0010.0020.00060.0130.050.0010.00060.00010.00070.00044.00.60.692.60.400.950.314.73.61.40.82368.75.10.650.610.751.4131.2180.482.71.23.6195.91.34.0171418270.401.100.201.63.03.03.00.30.310.400.406.63.526.110.450.100.0180.037.420.10.040.0190.0050.010.0150.11RSD,%B0.860.930.510.461.50.530.760.490.451.10.451.41.50.700.500.860.310.680.521.30.520.400.330.660.220.841.62.21.90.751.51.21.05.60.70IronCopperManganeseMagnesiumChromiumNickelZincTitaniumVanadiumLeadTinBismuthGalliumBoronBerylliumSodiumCalciumZirconiumCadmiumLithiumAntimonyPhosphorousAB0.00418.8I5atomline,II5ionline.Therelativestandarddeviation(RSD%)iscalculatedasfollows:RSD%5100=(d2/~n21!¯Xwhere:¯5averageconcentration,%,X¯,andd5differencebetweentheindividualresultsandXn5numberofdeterminations.Thedataarebasedontensuccessivereadings.APPENDIX(NonmandatoryInformation)

X1.CALIBRATIONANDSTANDARDIZATION

X1.1AdvantagesofComputerReadoutSystems

X1.1.1Computersorprogrammablecalculatorsmakeitpracticaltoemployconcentrationratioplotsforcalibrationcurves,whichcompensateforsignificantvariationsintheintensityofthealuminuminternalstandardlineasmajoralloyingelementsvaryoverwideconcentrationranges(seePracticeE158).Concentrationratiocalculationsmakeitpos-sibletoreporttheconcentrationofthealuminumaswellasthemajor,minor,andtraceelements,whichcanbevaluableforhigh-purityaluminum.

X1.1.2Acomputermakesitpossibletocorrectforinterfer-encesfromother2598.37A

˚elements,suchastheinterferenceofiron,

,onantimony,2598.06A˚.X1.2UniversalCalibrationVersusMatrixCalibrationX1.2.1Eithercalibrationprocedurecanbeemployedwiththistestmethod,asdescribedinX1.3.

X1.2.1.1UniversalCalibrationCurvesareasetofcurvescoveringthecompleterangeofconcentrationsexpectedforeachelementinallthealuminumalloystobeanalyzed.Forstandardization,severalreferencematerialsareemployedtoensurethatthehighendsofeachcalibrationcurvewillbereturnedtotheiroriginalreadings,andasinglehigh-purityreferencematerialisusedtosetthelowendsofthecurves.Foreachmajoralloytype,thecalibrationcurvesareadjustedbyburningatypereferencematerialinordertoobtainthecorrectconcentrationsforvariousalloys.

X1.2.1.2WiththeAlloy-TypeCalibrationprocedure,asetofcalibrationcurvescoversalimitedrangeofconcentrationsforafewspecificalloys.Differentbutsimplecurvescoveringarelativelyshortconcentrationrangeareusedforeachmajoralloy.Usuallytenmatriceswillencompassallthepresentcommercialaluminumalloys,organizedsothatoneortwostandardantsaresufficientforeachofthematricesdescribedinX1.4.

X1.3FourDifferentMethodsofCalibrationand

Standardization

X1.3.1Fortheanalysisofaluminumandaluminumalloys,fourdifferentmethodsofcalibrationandstandardizationarebeingused,aslistedbelow.Equivalentaccuracycanbeobtainedwitheachmethod,whenproperlyemployed.Thefirsttwoareusedprimarilyforrelativelysimpleanalyticalpro-grams,coveringonlyafewalloytypes.Thesecondtwoareappropriateformorecomplexanalyticalprograms.

X1.3.1.1Theinstrumentmayhavebeenprecalibratedbythemanufacturer,usingawiderangeofreferencematerialsandconcentrationorconcentrationratiocalibrationplots,orusingsetsofbinaryalloysforthedifferentelementsandconcentra-tionsorconcentrationratioplots.Asinglestandardantisemployedforeachalloytype,withacompositionnearthenormalortargetconcentrationsforallelements.Thecomputerappliesthedisplacementappropriatetothatalloyovertherelativelyshortportionoftheoverallcalibrationcurvethatwillbeused.Standardizationbecomesashortandsimpleprocess.X1.3.1.2Fortheanalysisofafewalloyswithcloselysimilarcompositions,suchasthe319,355,and356castingalloys,orthe1000and6000Serieswroughtalloyswith97+%aluminum,itmaybepossibletoemployonlyeightto

twelvecalibrantswhichwilldefinethecalibrationcurvesforallrequiredelementsovertheirrelativelyrestrictedconcentra-tionranges.Standardizationmaybepossiblewithoneortworeferencematerialsofthehighestconcentrationalloywhichhavethemajorelementsnearthetopoftheirrangeandtheminorandtraceelementsnearorabovethemiddleoftheirnormalranges.Alternatively,itmaybedesirabletouseseparatestandardizationreferencematerialsforeachalloytypewithinthematrix.Ineithercase,standardizationrequiresonlytwoorthreeminutesandcanberepeatedeasilyifthereisreasontosuspectsignificantdrift.

X1.3.1.3Setsofbinarycalibrantsorawiderangeofcalibrantscanbeusedtoestablishacalibrationcurveforeachelementthatwillcovertheentireconcentrationrangeexpectedinallsamples.Concentrationorconcentrationratioplotscanbeemployed.Thecomputerstoresasinglecurveforeachelement.Standardizationispracticedcustomarilyatthestartofeachnewshift(oroperator),usingseveralhighreferencematerialsthatbetweenthemcoverthehighrangesforallelements.Usuallyasinglehigh-purityreferencematerialsufficestostandardizethelowendsofthecurvesforallelements.Normallystandardizationwillrequiretentofifteenminutes.Inroutineuse,wheneveradifferentalloytypehastobeanalyzed,atypereferencematerialwillbeburnedandthecomputerwillapplylateralshiftstothestandardizedcurves,appropriatetoeachelementinthatalloy.Thiswillrequireonlyaminuteortwo.

X1.3.1.4Thewholearrayofaluminumalloyscanbedividedintoeightortenmatrices,aslistedinX1.4.EachmatrixiscalibratedasinX1.3.1.2andthecomputerstoresadifferentsetofcalibrationcurvesforeachmatrix.Standard-izationforeachmatrixissimilartothatdescribedinX1.3.1.2andusuallywillbepracticedduringeachshiftnormallyjustbeforethefirstspecimenofaparticularmatrixisexpectedinthelaboratory.

X1.4MatrixStructuresAppropriateforAluminum

Alloys

X1.4.1AppropriatematrixcalibrationstructuresforuseasdescribedinX1.3.1.2andX1.3.1.4areasfollows:

X1.4.1.1High-PurityAluminum,withallimpurityelementslessthan0.6%,includingthe1000Serieswroughtalloys.7X1.4.1.2High-Copper(upto10%),RelativelyLowSilicon(upto4%)AluminumAlloys,consistingofthe2000Serieswroughtalloysor200Seriescastingalloys7(exceptforthe242alloywithhighmagnesiumandnickel,whichrequiresaseparatestandardant).Twoseparatematriceswillberequiredifboththe2000Serieswroughtalloysand200Seriescastingalloyshavetobeanalyzed.

X1.4.1.3High-Silicon(upto12%),RelativelyLowCopper(upto4.5%)AluminumAlloys,consistingofthe300and400Seriescastingalloys(exceptforthe332alloywithhighmagnesiumandnickel,whichrequiresaseparatestandardant).X1.4.1.4High-SiliconAluminumAlloys,withsiliconinthe12to24%range.

7The1000to7000Serieswroughtalloysand200to800SeriescastingalloysspecifiedthroughoutX1.4areinaccordancewiththeAmericanAluminumAsso-ciationnumberingsystem.

X1.4.1.5The242and382High-TemperatureAluminumAlloyscanbecombinedintoasinglematrix,witha382standardizationreferencematerial,buttwoseparatematricesgivebetteraccuracy.

X1.4.1.6High-Magnesium(upto10%)AluminumAlloys,withlowconcentrationsofotherelements,consistingofthe5000Serieswroughtalloysand500Seriescastingalloys.X1.4.1.7Low-AlloyAluminum,withallalloyingelementslessthan2.5%,consistingprimarilyofthe6000Serieswroughtalloys.

X1.4.1.8High-ZincAluminumAlloys,consistingofthe7000Serieswroughtalloysand700Seriescastingalloys.X1.4.1.9High-Tin(above6%)AluminumAlloysconsistingofthe800Seriescastingalloys.

X1.4.1.10IdentificationMatrix,withallelementsfrom0.01%tothehighestconcentrationlikelytobeencounteredforeachelement,whichcanbeusefulforidentifyingscrap,mixedstock,oracompletelyunknownspecimen.

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