组合搅拌模式对连铸特殊钢大方坯凝固行为的影响  

Effect of Combined Stirring Modes on the Solidification Behavior of Special Steel Bloom Casting

作　　者：王璞 李少翔 张壮 铁占鹏 董延楠 张伟[2] 张家泉[1] WANG Pu;LI Shaoxiang;ZHANG Zhuang;TIE Zhanpeng;DONG Yannan;ZHANG Wei;ZHANG Jiaquan(School of Metallurgical and Ecological Engineering,University of Science and Technology Beijing,Beijing 100083;Xining Special Steel Co.,Ltd.,Xining 810005)

机构地区：[1]北京科技大学冶金与生态工程学院,北京100083 [2]西宁特殊钢股份有限公司,西宁810005

出　　处：《机械工程学报》2020年第12期99-106,共8页Journal of Mechanical Engineering

基　　金：国家自然科学基金资助项目(U1860111)。

摘　　要：组合搅拌模式是控制特殊钢铸态组织与均质性的重要手段。为深入揭示连铸结晶器电磁搅拌(Moldelectromagnetic stirring,M-EMS)和凝固末端电磁搅拌(Final electromagnetic stirring,F-EMS)的复合作用行为,基于麦克斯韦方程和低雷诺数湍流模型建立断面250mm×280mm的20Cr Mo A齿轮钢大方坯连铸过程电磁-流动-传热与凝固三维耦合数值模型。基于实测M-EMS中心线磁感应强度及F-EMS作用下的铸态组织白亮带宽度验证模型的可靠性。研究结果表明,M-EMS促使结晶器区域钢液产生水平旋流并冲刷凝固前沿,加强钢液和凝固坯壳的换热,可使钢液过热完全耗散及其凝固终点位置不同程度地前移,促进柱状晶向等轴晶的转变(Columnar to equiaxed transition,CET),从而可实现F-EMS作用区域为中心等轴晶区。组合搅拌作用下铸坯末搅区域液相穴宽度减小,糊状区内钢液对凝固前沿的冲刷速度降低,从而不易产生常见的负偏析白亮带缺陷。碳偏析检测结果表明,M-EMS可能造成大方坯出现一定程度的皮下负偏析和CET转变区的正偏析,但其中心偏析和铸态碳极差可获得明显改善。综合表明,合理的组合搅拌模式可有效改善特殊钢大方坯铸态组织的均质性,进而提高其轧材产品的热处理与服役性能。The mold electromagnetic stirring(M-EMS)and final electromagnetic stirring(F-EMS)is widely used in the special steel bloom casting,which could improve the as-cast quality effectively.A segment-based three-dimensional mathematic model coupling the electromagnetic field,melt flow,heat transfer and solidification in the whole casting domain is established to study the effect of M-EMS and F-EMS on steel flow and solidification behavior of a bloom casting.The model is validated by the measured data of magnetic flux density in the stirrer center and the white band width for plant tests.According to the simulation and experimental results,M-EMS can introduce a horizontal swirling flow ahead of the solidification front,which changes the flow pattern of melt and promotes the superheat dissipation of molten steel in the mold,and promotes the equiaxed crystals ratio when entering the solidification end stirring zone.M-EMS can make the carter end advanced by 0.347 m,the liquidus cavity width of the final stirring zone and washing velocity of molten steel to the solidification front are reduced.Carbon segregation detection shows that although M-EMS causes subsurface negative segregation and positive segregation of CET transition zone,the significant improvement of center segregation causes the range of carbon content decrease from 0.035%to 0.029%,which promote the homogenization production of bloom casting.It suggests that the reasonable combined application of M-EMS and F-EMS can improve the homogeneity of as-cast macrostructure of special steel blooms,thereby improving heat treatment and service performance of rolled products.

关 键 词：大方坯连铸 组合式电磁搅拌 碳偏析 白亮带 凝固终点 

分 类 号：TF777[冶金工程—钢铁冶金]