48-paper-Making Chinese Plate and Strip Production

MakingChinesePlateandStripProductionEvenMoreVersatileatNISCOPeterSopp1,JamesEvans2SynopsisTheplateSteckelmillconceptdiffersfromtheconventionalplatemillinthatslabsarecastatthefinalplatewidthinthiscaseupto3250mmwide.Thisavoidstheneedtoturntheslabandusebroadsiderollingtodevelopthefullplatewidth.Itisnotjusttheslabwidththatisimpressive,butthefactthatslabscanbeupto17600mminlength,withaweightof67tonnes.Usingslabsofthissizeenablesmultiplemotherplatestoberolledfromoneslab.Thisresultsinahighlyefficientoperation,butalsointroducesanumberofnewprocesschallengescomparedtotheconventionalplatemilloperation.ThispaperexplainshowSiemensVAIandSiemensI&SdesignedandcommissionedChina’sfirstplateSteckelmillplantinNanjingandsuccessfullyaddressedtheseuniqueprocesschallenges.Keyaspectsoftheequipmentdesign,theprojectorganisationandtheresultsfromthefirstyearofoperationaredescribed.KeywordsPlateSteckelmill,shipbuildingplate,pipesteels1.IntroductionInSeptember2004NanjingIron&SteelCo.Ltd(NISCO)inChinaputintooperationacombinedplate/Steckelmill.Withitsproductionfocusedmainlyonplateandstripforshipbuildingindustryandpipelines,NISCOisnowinapositiontoenhanceitsproductmixtomeetcurrentandfuturemarketdemandsforhigh-qualityandspecialtysteelproducts.TheorderforthisplateSteckelmillinJiangsuProvincewasplacedinMay2002toaconsortiumcomprisingSiemensVAIandSiemensIndustrialSolutionsandServicesGroup(I&S).Thenewfacilityisdesignedforaproductionoutputof1milliontpysplitinto750,000tonnesofplateand250,000tonnesofhotrolledstrip.Themillisdesignedtorollplatebetween4.5and50mmandstripbetween2.5and20mm.Themaximumplatewidthis3200mmandthestripwidthbetween1600and2500mm.TheslabsfortheplateSteckelmillarecastatwidthsupto3250mmusingtheworld’swidestslabcaster,alsosuppliedbySiemensVAI.ThisprojectdemonstratestheextenttowhichtheChinesesteelindustryhasembracednewtechnologicaldevelopmentstoimproveproductqualityandcompetitivenessinanincreasinglyglobalmarket.2.ProcessroutesatNISCOplateSteckelmillThissectionofthepaperdescribesthedifferentprocessroutespossibleusingtheplateSteckelmillfacility.Theversatilityoftheprocessenablesawiderangeofdifferentproductstobeproduced.Aschematicdiagramofthelinelayoutisshowninfigure1._________________________________________________________________________1GeneralManagerMetalsSiemensI&S,Erlangen,Germany2RollingMillsandProcessLinesDirector,SiemensVAI,Sheffield,UKSEAISI2006–NISCOPAGE2Figure1:PlantlayoutMillentryareaThereheatfurnacecaneitherbehot-chargeddirectlyfromtheSiemensVAIcaster,orchargedwithcoldslabsfromtheslabtransfertableandloadedbyacrane,orasathirdoptionchargedfromtheslowcoolingorsoakingpitarea.Thesoakingpitroutecanbeusedasabufferforshortplannedorunplannedmillstoppages.Theslowcoolingrouteenablessomeslabstocooltoalowertemperatureforhydrogendiffusionbeforebeingchargedintothefurnace.Hydrogendiffusionreducestheamountofhydrogenintheslab,minimizingtheeffectofhydrogeninducedcrackinginpipelinesteelsintendedforspecificenvironments,ortocarrysourgas.Hydrogendiffusesoutoftheslabprovidedtheslabiscooledveryslowlytobelowapproximately350°C.Thecommonmethodofachievingthisistostacktheslabscloselytogethertocreatealargemass,whichreducesthecoolingrate.Oncetheslabhasdroppedbelowapproximately350°C,itcanbeputbackontotherollertableanddirectlychargedtothefurnacefollowingthehotchargeroute.Theslabsaretransportedthroughthefurnacebywalkingbeamsandextractedbythedischargingmachineforplacementonthedischargerollertablesdictatedbythemillpacingsystem.Atthispointthreeprocessroutesarepossible:slabreject,iftheslabcannotberolledduetooperatorsopinionslabrecharge,ifanunscheduleddelayoccursinthemilldescalingandrollingasthenormalprocessroute.Non-SteckelrollingFollowingdescaling,theslabistransportedtothemillentrysideguidesandcentered.Aphotographofthemillstandisshowninfigure2.Aftersetupofthemill,theslabisthreadedintothemillthroughtheedgerandthenintothehorizontalstand.Theverticaledger(synchronousmotorfedbySIMOVERTMasterdrive)isequippedwithAWC(automaticwidthcontrol)supportedbySSC(shortstrokecontrol)toensureoptimalmaterialwidthafterthehorizontalpassalongtheentirestriplength.Piler#1DoubleSideTrimShearInspectionColdDivideShearPiler#3Piler#2U.S.T.Marker&StamperStoragePilePlatePlateTurnoverRe-HeatFurnacePrimaryD/SDescalerDDescalerDescalerHydraulicDowncoilerEntrySteckelFurnaceExitSteckelFurnacePinchRollVerticalEdgerPlate-SteckelMillRotaryCropShearRunOutTable&LaminarCoolingHotLevellerCoolingBed#1CoolingBed#2SEAISI2006–NISCOPAGE3Theedgerisoffullyhydrauliclongstrokedesignwithnomechanicalscrews,makingitparticularlymaintenancefriendly.The80,000kNmaximumrollingloadhorizontalmillstandisequippedwithascrewdownsystem(electricalgapcontrol);aback-uprollbalancingsystem;aheavyworkrollbendingsystem;hydraulicgapcontrolusinglongstrokebottommountedAGC(automaticgaugecontrol)cylindersandDPC(dynamicprofilecontrol)functions.Thicknessandprofilegaugesarelocatedclosetothemillstandtoallowinbarfeedbacktobeused.Descalingcanalsobecarriedoutonentrytothemillstandduringtheroughingpasses.Figure2:TheplateSteckelmillstandandcoilerfurna