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CASTING Developmentandapplicationof dynamicsecondarycoolingand softreductionforslabcasting Dynamicsecondarycoolingandsoftreductioncontrolmodelshavebeendevelopedforanewly commissionedslabcastertoimprovethequalityofthecastslab.Thesystemcomprisesthreeparts: dynamicthermaltrackingmodel,dynamicspraywateroptimisationmodelandadynamicsoft reductioncontrolmodel.Thesystemhasbeenshowntobestableandrobustfortheproductionof shipplategradesand,followingfurthercalibration,willbeappliedtothewholeproductmix. Authors:YunheChang,KeLiu,ZhanguangHanandJiaquanZhang StateKeyLaboratoryofAdvancedMetallurgyandUniversityofScienceandTechnology,Beijing hina’ssteelproducersarefacingaseriesofsevere Cchallengesfromuserswhorequirehigherquality steels.Incontinuouscasting,internalcracks,centre segregationandcentreporosityareusuallythemain bottleneckspreventingdevelopmentofhigh-strength steelgradeswithqualifiedmechanicalproperties.Forthis reason,dynamicsecondarycoolingandsoftreduction technologyhavebeentwoofthekeytechnologies adoptedbymanysteelplantsthroughouttheworldin thepastfewyearstoimproveslabquality. Incasting,theinterdendriticliquidsteelinthemushy zoneofthefinalsolidificationstageflowstothecentre areathroughconvectionandbulging.Thisleadsto centrelinesegregation.Thevolumecontractionofsteel onsolidificationcanalsoleadtocentralporositywhere thereispoorfeedingorcompensation.Also,thecyclical coolingandreheatingofthestrandsurfacetemperature duringcastingisconnectedwiththeformationofbroad facecracking,subsurfacecrackingandotherdefects.The appearanceandintensityofcentresegregationandcentre porosityorotherdefectsarecloselyrelatedtosteelgrade, liquidsteelsuperheat,castingspeedandcoolinghistory. Dynamicsoftreduction,combinedwithdynamic secondarycooling,hasbeenshowntobeaneffectiveway tominimisecentresegregationandporosity.Inthispaper, anewlydevelopedthermaltracking,dynamicsecondaryrFig1Structureofdynamicthermaltrackingmodel coolinganddynamicsoftreductionsystemforslabcasting controlisdescribed. DYNAMICTHERMA