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ID:34908294
大小:5.18 MB
页数:73页
时间:2019-03-13
《大断面立式半连铸坯凝固微观组织的数值模拟》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、ADissertationSubmittedinPartialFulfillmentoftheRequirementsfortheDegreeofMasterinEngineeringNumericalModelingofSolidifiedMicrostructureinVerticalSemi-continuousCastingwithALargeCross-sectionMasterCandidate:ZhangDongxiaoMajor:MaterialScienceandEngineeringSupervisor:Prof.ChangQingmingWuhanUn
2、iversityofScienceandTechnologyWuhan,Hubei430081,P.R.ChinaMay,2015摘要特厚大断面连铸坯的生产目前仍是业界的难题。通过数值模拟的方法,分析半连铸过程的凝固组织形貌及不同工艺情况对凝固组织的影响,是开发1600mm×500mm的立式大断面半连铸机的必要手段。本文根据立式半连铸的特点及钢液凝固的复杂过程,建立了有限元(FiniteElement)和元胞自动机法(CellularAutomaton)相结合的CA-FE模型。以断面尺寸为1600mm×500mm的H13钢为研究对象,基于有限元软件ProCAST建立了的铸坯
3、的物理模型。通过边界条件和参数设置,模拟了立式半连铸过程的拉坯、凝固过程及凝固微观组织,得到了不同时刻的温度、凝固坯壳、凝固组织的特点,并从过热度、拉坯速度、二冷段冷却强度等方面模拟分析了不同工艺条件对凝固微观组织的影响。研究结果表明,应用宏微观耦合的CA-FE模型可以较好的模拟大断面立式半连铸坯的温度场、凝固场和凝固微观组织;随着过热度的增加,晶粒平均尺寸增大,等轴晶比例增大,经分析,应选择较低的过热度来进行浇注;拉坯速度对凝固组织的影响也较大,较快的拉速可以使得晶粒平均尺寸减小,等轴晶比例增大;改变二冷段各区冷却水量后,模拟结果显示较弱的二冷段冷却强度的凝固组织晶粒更小
4、,等轴晶比例更大。关键词:大断面;立式半连铸;CA-FE;微观组织;数值模拟IAbstractTheproductionofcastingbilletswithaextralargecross-sectionisstilladifficultissueinthemetallurgicalindustry.Numericalmodelingisanecessarymethodtoanalyzethesolidificationmicrostructureofsemi-continuouscastingprocessandtoinvestigatetheinfluenceofd
5、ifferentprocessconditionsonsolidificationstructure,andthusisefficienttooltodevelopa1600mm×500mmverticallargesectionofsemicontinuouscaster.Inthispaper,accordingtothecharacteristicsofverticalsemi-continuouscastingandthecomplexprocessoftheliquidsteelsolidification,aCA-FEmodelwasestablishedbyc
6、ouplingthefiniteelementandcellularautomatonmethod.Thesemi-continuouscastingprocesswithacross-sectionaldimension1600mm×500mmisstudied,aphysicalmodelofthecastingslabisestablishedbasedonfiniteelementsoftwareProCAST.Theverticalsemi-continuouscastingprocess,solidificationprocessandmicrostructur
7、earesimulatedunderdifferentconditionsandparameters.Theeffectsofdifferentsuperheat,castingspeed,secondarycoolingintensityonthesolidificationmicrostructureareanalyzed.Theresultsshowedthat:WiththeCA-FEmodelcouplingmacroandmicroscale,thetemperaturefield,solidifica
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