简介:Thecenterlinesegregationincontinuouscastingsteelisknowntobeformedbytheinterdendriticenrichedliquidflowatthesolidificationendinstrand.Atpresent,severalmethods,suchasthermalsoftreduction,electromagneticstirringanddynamicsoftreduction,areavailabletoreducethecentersegregationandtoimprovetheinternalquality.Althoughsomemethodscouldalleviatecentersegregationtosomeextent,theycanalsogiverisetonewproblems.Forinstance,thermalsoftreductioncanleadtosurfacecrackingduringcastingofsomesteelsandelectromagneticstirringcanresultinwhiteband.Dynamicsoftreductionisaneffectivetechnologyfortheimprovementofstrandqualityincontinuousslabcasting.Inthispaper,thekeyparametersofdynamicsoftreductiontechnology,suchassoftreductionregion,thetotalreductionamount,forlowcarbonsteelhavebeenstudiedbasedonexperimentalandtheoreticalanalysis.Thesoftreductionregionwasrelatedtothesegregationofchemicalcomposition,slabbulgingofnarrowsideandavoidinginternalcrackofslab.Thetotalreductionamountwascomposedofnaturalthermalshrinkageandactualreductionamountdependingoncriticalstrain.Forlowcarbonsteelwithslabdimensionof(950-1950)mm×170mm,thesolidfractionrangeinsoftreductionregionwasrecommendedfrom0.4to0.8,thetotalreductionamountwas2.0-2.8mm,andtheoptimizedreductionratewas0.4-1.2mm/min,respectively.Furthermore,adynamicsoftreductionsystemincontinuousslabcasting,VisualCast-Dynamic,hasbeendevelopedbymultithreadingmethod.Itdemonstratedthatthedynamicsoftreductionmodelinthisstudywascorrectwiththeabilityofonlinecontrol.
简介:AttheinitialoperationstageofthecontinuousbloomcasteratBaosteel,alotofcentralporosityandcracksoccurredinblooms,especiallyinthebloomsofhigh-pressureboilersteel.Inthisstudy,amodelofheattransferandsolidificationwassetuptoanalyzetheprocessofcontinuousbloomcasting.Basedonthemodel,thedistributionsoftemperaturefieldandshellthicknesswereobtained,themushyzonewasdefined,andtherebythetechnologyofsoftreductionforbloomswasdeveloped.Afterseveraltestswereconducted,areasonabletestplanwasdeveloped,whichledtothedeterminationoftheoptimalreductionzoneandgaugereduction.Now,centralporosityandcracksinbloomsarealmostavoidedandtheinnerqualityhasbeenobviouslyimproved.
简介:DynamicmodelcontroltechnologiesofsecondarycoolingandsoftreductionofBaosteelareintroduced.Modelprincipleandcontrolsystemarchitecturearesummarized,aswellasfunctionsandfeatures.Finally,applicationsofmodeltechnologiesarediscussed.Theself-developeddynamicsecondarycoolingmodelandthedynamicsoftreductionmodelhavebeenappliedonseveralcastingmachinesinsideandoutsideBaosteel,desiredcontroleffectswereachievedwithgoodstabilityandreliability.Temperaturemeasurementresultsverifiedthecorrectnessofmodel.
简介:Takingα-FeandNd2Fe14Bgrainsasexample,thegrainsizedependenceoftheexchange-couplinginteractionandeffectiveanisotropyandalsotheirvariationsdependingontheratioofmagneticallysoftandhardgrainsizes,Ds∶Dh,wereinvestigated.WhengrainsizeD>Lex,thegrain'sanisotropyisthestatisticvalueofthecoupledanduncoupledpart.TheanisotropyconstantofuncoupledpartisthecommonvalueK1andthatofcoupledpartvarieswiththedistancetothegrainsurface.Theeffectiveanisotropyconstantbetweenmagneticallysoftandhardgrains,Keff,canbeexpressedasthesumoftheproductsofvolumefractionsforsoftandhardgrains,respectively,andthecorrespondingmeananisotropyconstants.Thecalculationresultsindicatethattheexchange-couplinginteractionisenhancedwiththereductionofgrainsize,andtheeffectiveanisotropydecreaseswithreducinggrainsizeandincreasingratioofDs∶Dh.Inordertogethigheffectiveanisotropyconstant,Keff,incompositemagneticallysoft-hardgrains,thehardgrainsizeshouldbelargerthan30nmandthesoftgrainsizeshouldbeabout10nm.