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Corrosion

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CorrosionCorros

    Corrosion

Dec.2008,Volume2,No.12(SerialNo.13)JournalofMaterialsScienceandEngineering,ISS

    N19348959,USA

    ;Corrosionresistanceofhighaluminagraphitebased

    ;refractoriestothesmeltingreductionmelts|

    ;LIUQingcai,ZHENGHuirain,LUCun-fang,GAOWei

    ;(SchoolofMaterialScienceandEngineering,Chongqing(f1,ersi~.Chongqing400044.C

    hina)

    ;Abstract:Thecorrosionresistanceandmicrostmctureof ;Al01Cbasedrefractoriesinsmeltingreductionmeltswere ;studiedandevaluatedbythequasi.stationaryimmersionand ;rotaryjmmersiontest.ThecorrosionrateoftheAI,O{Cbased

    ;refractoriesisdecreasedwiththeadditionofthegraphitecarbon ;andZrO,.Thetestresultsshowedthatthebrickscontaining ;Zr01hadmuchbe~ercorrosionresistancethantheZrO2-free ;bricks.TheZrO,additionimprovedtheoxidizationresistanceof ;therefractoryanddecreasedtheinteractionratebetweenthe ;meltsandtherefractory.ThecorrosionoftheAI,0Cbased

    ;refractoriesiscausedbyboththeinteractionbetweenmeltsand ;refractoryandthedissolutionoftherefractoryconstituentsinto ;themelts.

    ;Keywords:corrosionresistance;A1203Cbasedrefractory;

    ;ZrO,melt

    ;1.Introduction

    ;Thecorrosionresistanceoftherefractoriesisone ;oftheimperativeproblemsforthedevelopmentof ;smeltingreductionwithironbathl_4].

    ;TheA1203C

    ;basedrefractorieshavebeenwidelyandsuccessfully ;usedinthemetallurgyindustry.A1203Cbased

    ;refractoriesarewidelyusedastheliningmaterialsin ;blastfumacesandelectricfumaces.Numerous

    ;investigationsofthephysicalpropertiesand

    ;microstructuresoftheA12O3-Cbasedrefractoriesare ;availableinliterature[6,-9..buttheinvestigationsofthe ;corrosionbehaviors0fAl,O1.Cbasedrefractoriesin ;themeltsofsmeltingreductionwithironbatharevery ;scarce.Thestudiesofthepropertiesandcorrosion ;Ackn0wledgement:ThisworkwassuppoaedbytheNational ;KeyTechnologyR&DProgramofChinafNo.

;2007BAC24B00).

    ;Correspondingauthor:LIUQingcai,male,professor.Email

    ;liuqc@cqu.edu.cn

    ;mechanismoftheA12O3-Crefractoriesand ;Al203CTiO2insmeltingreductionmeltswere ;reportedbyLIUQ.c[1o_”.YANGHotmg—Yireported

    ;thecorrosionresistanceandmicrostructureofthe

    aluminarefractories,basedontherotaryslag ;high

    ;test[1

    ;.

    ;Others_havestudiedthewearof

    ;high?aluminabrickstothebasicityofslagortotheraw ;materials.

    ;Thisworkaimsatstudyingthecorrosion

    ;resistance,andtheeffectoftheZrO2additiononthe ;corrosionrateoftheA1203-Cbasedrefractories.The ;majorfactorsthataffectthecorrosionbehaviorof ;A1203Cbasedrefractoryinsmeltingreductionmelts ;withironbathhavebeenanalyzed.

    ;2.Investigationmethods

    ;2.1Selectionolrefractories

    ;ThreecommercialproductsofAl203Crefractories.

    ;designatedastypesAC1,AC2,andAC3,wereselected ;forstudy.RefractoryspecimensofAZltoAZ3were ;preparedinalaboratory,andshapedandsinteredina ;refractoryfactory.Theirchemicalcompositionsand ;physicalpropertiesarelistedintheTable1. ;2.2Smeltingreductionmelts

    ;Themeltswerecomposedofmoltenslagandiron ;bath.Thesyntheticslagwasamixtureofblastfurnace ;slagandchemicaladditives;itschemicalcomposition ;was(wt)10.0%FeO,35-3%Ca0,33.2%SiO2,8.0% ;MgO.11.0%A1203.2.5%TiO2.Theironbathwas ;formedbypigironscrap,itscompositionwas(wt): ;4.16%C,0.53%Si,0-32%Mn,0.10%Pand0.034%S. ;49

    ;CorrosiOnresistaneeofhigh.aluminagraph

    ;itebasedr

    ;efractories

    ;

    ;to

    ;

    ;thesmeltingreductionmelts

    ;3O

;25

    ;20

    ;5

    ;0

    ;05

    ;0.03.06.09.012.0I5.0

    ;FeOContent.%

    ;Fig.1FeOcontentinmeltsandthecorrosionrateof ;therefractories,testtemperature1773K

    ;Thecorrosionrateofrefractoriesisincreasedwith ;theincreasingoftheFeOcontentinthemelts.The ;corrosionresistanceoftherefractoriesevidently ;decreasesastheFeOcontainingofthemeltsincreases. ;TherefractoriescontainingZrO2exhibitagood ;anticorrosioncharacteristic,especiallyinthemeltsof ;Fe0concentrationabove6%.Thereactionrate ;betweenthemeltsconstitutesandtherefractoriesis ;speededupbyincreasingFeOcontentofthemelts.The ;graphitecarboncontainedintherefractoryisanactive ;reducingagentoftheironoxidizes.Thegraphiteofthe ;A1,01.Crefractorieswasoxidizedbytheironoxidesof ;themelts.Poresandcracksareformedinthereaction ;ZOne.

    ;4.3Temperatureandcorrosionrateof

    ;refractories

    ;Fig2showsthetestresultsofcorrosionrateof ;refractoriesatthedifierenttemperatures.Itshowsthat ;thetemperatureofthemoltenbathwasoneofthe ;importantfactorsthatinfluencedthecorrosion ;behavioroftheA12O3-Cbasedrefractory.

    ;Thecorrosionrateoftherefractoriesincreased ;rapidlyasthetemperatureincreased.Themovingrate ;ofslagfilm,theinteractionratebetweenthemeltsand ;refractories.andthediffflsionofmasswillbeincreased ;asincreasingofthetemperature.Thereductionrateof ;ironoxidesinmeltswouldbeincreasedandthestirring ;densityofthemoltenbathbytheheatmotionandthe ;gaseousCOproducedinthereductionreactionwould ;befierceasthetemperatureincreasing.

    ;40

    ;3O

    ;20

    ;10

    ;00

;65017001750i800l85019001950

    ;Testtemperature,K

    ;Fig.2Relationshipbetweenthetemperatureand ;corrosionratesoftherefractories

    ;4.4MicrOstructuresandthecorrosion

    ;mechanism

    ;Thedeteriorativelayermicrostructureofthe ;refractorieswasinvestigatedbytheScanningElectron ;Microscope(SEM),ElectronProbeMicroanalyses, ;andtheEnergyDispersiveSpectroscopy(EDS).Fig.3 ;isthecompositionoftheinterfacebetween

    ;deteriorationlayerandslagfilm.Themetaliron, ;FeSi2O3,CaSiO3,FeTiO3,SiO2arefoundinthe ;deteriorationlayerofrefractory.Thegraphitecarbon ;wasoxidizedover90%andnographitecarbonwas ;foundintheinterfacebetweendeteriorativelayerofthe ;refractoryandslagfilm.Fig.4isthemicrostructuresof ;Al203Crefractoryinthemeltswithironbath.Fig.4(a) ;istheoriginalconstituentsoftherefractory.The ;structuresoftheAI,O3-Crefractoriesarecomposedof ;corundum,mullite,A1203andgraphitecarbon.Fig.4(b) ;isthemicrostructureofthedeteriorationlayerofthe ;immersedA1203Crefractory.Thedeteriorativelayer ;ofAI203Crefractorywascorrodedgreatlybythe ;smeltingreductionmelts.Themicrostructuresofthe ;AC2compositionofA1203-Crefractorieswere ;changedwiththeslagandironpenetration.Interaction ;betweenthemeltsandtherefractorieshastakenplace ;andalotofnewcompoundsformed,suchasCaSi03, ;51

    ;,,o_I0?o.1_100

    ;q/?0.II10.0U

    ;C

    ;

    ;orrosionresistanceofhigh-a

    ;

    ;luminagraphitebasedrefractoriestothesmeltingreductionmelts ;TiO2,FeSiO3,Al2SiO5andFe3Cinthedeteriorative ;layer.

    ;Fig.3Compositionsoftheinterfacebetweendeteriorative ;layerofA1203Crefractoryandslagfilm(EDS)

    ;Fig.4ThemicrostructuresoftheAC2,immersedinslag ;andironbath,testtemperature1773K,rotary ;speedofrefractoryinmelts15r/min.

    ;Notes:(a)istheoriginalmicrostructure;(b)isdeteriorative ;layerofrefractory.

    ;Fig5presentsthemicrostructuresofthe

    ;deteriorationlayerofrefractoryAZ2.Theoriginal ;constituentsoftheA1203-C-ZrO2refractoryarezircon, ;corundum,mullite,andgraphite11.Fig.5(a)shows ;thatthemeltspenetratedanddestroyedthestructureof ;therefractory.FromFig.5(b),theinteractionbetween ;52

    ;themeltsandtherefractoryoccurredandnew ;compoundsofFeSiO3(meltingpointapproximately ;1205~C),ZrSiO3,CaFeO2,Ca3SiO3andCaSiO3were ;formedinthedeteriorationlayerandslagfilm.Table3 ;iStheelectronprobemicroanalysesofthedeteriorative ;layerforAZ2.ThedeteriorativelayeriScalciaand ;silicarich.Fortheslagfilm,thereismuchmorecalcia, ;aluminaandsilicarich.Theresultsshowthatthe ;oxidesofSiO2,CaO,TiO2,FeOandtheircompounds ;ofFeSiO3,ZrSiO4,CaSiO3appearedinthe

    ;deteriorativelayeroftheA1203CZrO2refractory.The

    ;metalironalsoexistsinthedeteriorativelayerandslag ;f1m.

    ;Fig.5Themicrostructures(SEM)oftheAZ2,immersed ;inslagandironbath,testtemperature1773K, ;rotaryspeedofrefractoryinmelts15rpm

    ;Notes:(a)ismeltspenetrated;(b)isthedeteriorationlayerof ;refractory.

    ;Table3Electronprobemicroanalysesofthe

    ;interfacebetweentherefractoryandslagfilm ;CorrosionresistanceofhighaluminagraphitebasedrefractoriestotheSmeltingredu

    ctionmelts

    ;5.Conclusions

    ;Thecorrosionresistance0fA1203-Cbased

    ;refractoriestothesmeltingreductionmeltsisimproved ;withtheadditionofgraphitecarbonandZrO2.The ;corrosionrateoftheAZrefractoriesisdecreasedwith ;theadditionoftheZrO,intherefractories. ;ThecorrosionrateofbothACandAZsystem

    ;refractoriesincreasedastheironoxidecontentofthe ;meltsandthetemperatureincreasingofmoltenbath. ;Thecorrosionrateoftherotarytestis30%higherthan ;thatofquasi.stationaryimmersiontest.

    ;ThecorrosionmechanismofACrefractoriesin ;thesmeltingreductionmeltswithironbathisgraphite

    ;oxidizationfirstanddeteriorativelayerformation.For ;theAZrefractory,theinteractionbetweenmeltsand ;refractory,andthedissolutionoftherefractory ;constituentsintothemeltsarethemajorcorrosion ;behavior.ThenewcompoundsofFeSiO3(themelting ;point1205?),ZrSiO4,Ca3FeO4,CaSiO3formedinthe ;deteriorativelayerduringtheinteractionbetweenthe ;meltsandAZsystemrefractory.

    ;[6]

    ;[7]

    ;(8

    ;9]

    ;[10]

    ;[12

    ;13]

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    ;

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