搜索
1©2009InnseCilindri–AllRightsReservedFLATROLLINGEARLYFINISHINGSTANDSHIGHSPEEDSTEELWORKROLLAPPLICATIONS热轧板带精轧机前段机架高速钢工作辊的应用Nov.200909年11月2©2009InnseCilindri–AllRightsReservedUSINGOFHSS高速钢轧辊的使用WEARRESISTANCE耐磨性MULTIPLECAMPAIGNS多次轧制周期(REDUCTIONINNUMERSOFGRINDINGS)（减少磨削次数）IMPRUVEMENTINROLLPERFORMANCE提高轧辊性能IMPRUVEMENTINMILLUSING提高轧机效率IMPRUVEMENTINSTRIPQUALITY改善板带质量REDUCTIONOFCOSTS降低成本3©2009InnseCilindri–AllRightsReservedGUIDELINEFORTHESTARTINGINUSINGOFHSSROLLSINFRONTSTANDSOFHSM热带轧机前段机架高速钢轧辊的使用指南4©2009InnseCilindri–AllRightsReservedThisisaguidelinefortheintroductiononthemilloftheHSSworkrollsinsubstitutionofHighCrIronworkrolls.MaintargetIncrementinproductivity,reductionincosts,improvementinquality,through:•multiplecampaigns(reducingthenumberofgrindings,andconsequentlytheextra-grindingforeachgrinding•reductionoftheintermediatechangesnotplanned•improvementofsuperficialqualityofthestripPreliminaryactivities•DetectthestandardusingconditionsoftherollsinHighCrIron,through:•definitionofthecampaignduration•detectionoftherollingforces•rolltemperatureafterusing(15min.approx.afterrolling)verifiedinatleastthreepositions(centreandrollingedges)•detectionofrollprofileafterusing•photographicdocumentationofsuperficialconditionsbeforeandafterusing5©2009InnseCilindri–AllRightsReserved本文将向您介绍在轧机中替代高铬铁工作辊而使用高速钢工作辊的准则。主要目标：提高产量，降低成本，改善质量这三项目标需要通过以下几个方面来实现：•延长轧制周期（减少磨削次数和每次磨削中的额外磨削量）•减少非计划的中间换辊次数•改善板带表面质量预备工作：检测高铬铁轧辊的正常使用情况：•确定轧制周期•检查轧制力•检测辊温（下机后约15分钟，至少检测三个点包括轧制区域的两端和辊身中部）•检测使用后的辊形•轧制前后拍照记录辊面情况6©2009InnseCilindri–AllRightsReservedElementstobeconsideredHSSrollshave(incomparisonwithHiCrIronrolls):•quiteminimalwear•higherthermaldiffusionoftheshell,withconsequenttendencytohaveadifferentthermalprofile(therollswellsupmorethanhighCriron),andhigherlevelofheatinthecore(longertimetocoolaftertheuse)•lowerquantityofcarbides,andconsequentlyslowgrowingoftheoxidefilminthefirstphaseofrolling•presenceofMChardcarbides,withpossibleincrementoftherollingforces(incrementoffrictioncoefficient)•tendencytotheincrementofthesuperficialtemperatureofthestrip,duetotheincrementoffrictioncoefficient•thecompressivetensionalstatusoftheshellishigher;thereforemechanicalcrackshavehigherpropagationspeed.7©2009InnseCilindri–AllRightsReserved需考虑的因素：高速钢轧辊的特性(同高铬铁轧辊相比):•磨损量相当小•工作层热传导快，其结果是热辊形与高铬铁轧辊不同（高速钢轧辊的热凸度比高铬铁轧辊大）；芯部热量更高（使用后需更长的时间冷却）•碳化物含量低，在轧制初始阶段氧化膜形成慢•高速钢中坚硬的MC碳化物可加大轧制力（增加摩擦系数）•由于摩擦系数的增加导致板带表面温度上升•工作层的压应力更高，因此机械裂纹的扩展速度快8©2009InnseCilindri–AllRightsReservedStartingwithHSSrollstrials高速钢轧辊的试用：Usuallytrialsstartwithoutmodificationsinstandardrollingconditions•detectionofthesameparameters(inthesameconditions)usedwithHighCrIron,usingHSSrollsfirstinonestand,thanintwostandssimultaneously•makeaseriesofphotos(usually4÷6),onwhichbasistheworkerscandecideiftherollsaresuitableforafurthercampaignwithoutgrinding.通常在开始试用高速钢轧辊的时候保持与高铬铁轧辊相同的轧制工况。•在相同的使用工况下，检测与高铬铁轧辊相同的参数。首先在一个机架上使用HSS，然后同时在两个机架上使用HSS。•制定一组辊面对照图（一般4-6张），操作工可根据对照图判定是否不用磨削继续上机使用。9©2009InnseCilindri–AllRightsReserved#1and#2:rollsurfacequalityacceptableforfurtherusing#1和#2：可继续上机使用#3and#4:rollsurfacequalitynotacceptableforfurtherusing#3和#4：不可继续上机使用Remarks:itisfundamentaltheeducationoftheworkerstotakenoteoftherollsurfacesimmediatelyafterusing,andtonotedowninaproperfilethequalitativelevelofthesurfaces.备注：要求操作工在下机后立即对辊面情况作记录，记录辊面质量情况并存档。#1轧辊表面光滑的灰黑色氧化膜#2轧辊表面灰黑色氧化膜伴轻度剥落#4轧辊表面非常严重的氧化膜剥落，触摸感觉粗糙#3轧辊表面严重的氧化膜剥落，触摸略感粗糙10©2009InnseCilindri–AllRightsReservedPossibleaidstobemade有效措施：•mechanicalprofile:toevaluateonthebasisofthecomparisonofthethermalprofilewithHighCrIronrollsafterthecampaign.IfthetemperatureofHSSrollsafterusingishigherthan70°Citcouldbenecessaryareductionofthemechanicalprofile:forinstance,0,05mmevery10°CofincrementintemperatureofHSSrollscomparedwithHighCrIronrolls•cracks(firecracksandmechanicalcracks)•机械辊形：轧制周期结束后，与高铬铁轧辊热辊形比较，判断是否需要减少高速钢轧辊机械辊形的修磨量。如果高速钢轧辊下机后的辊温高于70度，就有必要减少机械辊形的修磨：与高铬铁轧辊相比，高速钢轧辊的温度每升高10度就可减少修磨0.05mm.•裂纹（热裂纹和机械裂纹）的修磨以防事故发生。11©2009InnseCilindri–AllRightsReservedFirecrackingThefactthatHSSrollshaveconsistentlyshownaverygoodresistancetofirecrackinitiationhasbeenaplusoverotherhotstripmillmaterials,buttherealplusisthatwhencertainconditionsduringrollingcausefirecrackingtooccur,theHSSrollmaterialstronglyresiststhegrowthandpropagationofthesecracks.RollPropertiesFirecrackingoccurswhenthermalstressesinducedduringrollingexceedthethermalfatiguestrengthoftherollsurfacematerialwhichisafunctionofthehotstrengthorhotelasticlimitofthematerial.Thehigh‘hot’propertiesoftheHSSrollsresistthermalfatigue,thermaloverstressesinconnectionwiththelowvolumepercentageofnetworkcarbidesandthelackofcoarseeutecticcarbidesincomparisonwithHiCrIronrolls.Growthandprogressionarefurtherresistedbythematerial’ssmallausteniticgrainsize.Thematerialresistancetofirecrackgrowthandpropagationaccountsforitsresultantresistancetobanding.12©2009InnseCilindri–AllRightsReserved热裂纹高速钢轧辊的抗热裂纹性能比其他热轧辊材质好，但真正的优点是一旦轧制过程中出现热裂纹，高速钢轧辊材质能很好地阻碍热裂纹的扩展。轧辊性能当轧制过程中热应力超过轧辊表面材料的热疲劳强度就会出现热裂纹，这是材料的高温强度和热弹性极限的作用。与高铬铁轧辊相比，高速钢轧辊体现出更高的抗热疲劳、抗热过应力等“热”性能，这与其组织中网状碳化物含量低、粗大共晶碳化物含量少有关。材料中细小的奥氏体晶粒能