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1、TitaniumNitridePrecipitationBehaviorinThin-SlabCastHigh-StrengthLow-AlloySteelsMICHAELT.NAGATA,JOHNG.SPEER,andDAVIDK.MATLOCKToassessthepotentialforobtainingandutilizingtitaniumnitride(TiN)refinementviatheincreasedpostsolidificationcoolingratesassociatedwiththin-slabcasting,TiNparticlesizedistri
2、butionswereevaluatedbytransmissionelectronmicroscope(TEM)examinationofcarbonextractionreplicas.Eightcommerciallyproducedthin-slabcastTiNsteels,nominally0.05pctC,1.2pctMn,andoneconventionallycaststeelwerereceived.Thinslabsamplesweretakenfromthreelocationsintheproductionprocess:quenchedaftercasti
3、ngbeforethetunnelfurnace,quenchedaftertunnelfurnacesoaking,andtheas-rolledandair-cooledfinalproduct.Effectsofcoolingratewereevidentintheresultsandagreewithpreviouslydocumentedbehavior,whereprecipitatesizedecreaseswithincreasedcoolingrate.Statisticaldifferencesinparticlesizebetweenspecimensfroms
4、teelswithdifferentchemistrieswereshown.Thesevariationsresultfromdifferencesinthedrivingforceforprecipitation,ratesofcoarsening,anddifferencesinvolumefractionduetochangesinsteelcomposition.Theinteractionofcompositionandprocessing,suchassoakinginthetunnelfurnaceandrolling,wasfoundtobeimportant.Fo
5、rexample,thehyperstoichiometricsteel(excessTi)exhibitedfineTiNaftercastingandsoaking,butdramaticcoarseningafterhotrolling.Thisbehaviorwasattributedtodeformationenhancedparticlecoarsening,orincompleteprecipitationaftersoaking,followedbycontinuedgrowthduringsubsequentprocessing.I.INTRODUCTIONvolu
6、mefractionofthepinningparticles,andzisagrainsizeheterogeneityfactor.[2]THIN-SLABcastingisbeingusedincreasinglyasaChangesinchemicalcomposition(e.g.TiorNlevels),meansofproducingsheetsteelsbecauseofitsreducedcapi-liquidus/solidustemperature,andcoolingratemayinfluencetalcosts.Whileinitialdifficulti
7、esduetodifferencesinpro-theamountofTiNthatmaybeprecipitatedinthesolidandductionmethodshavebeenovercomeandaviableproductisthetemperaturesoverwhichprecipitationoccurs.Conse-beingproduced,muchremainsunknownaboutthisrelativelyquently,