大断面合金钢圆坯连铸V形通道偏析形成机理及靶向控制研究

随着铸坯断面尺寸和钢中合金含量增加，大断面圆坯连铸V形通道偏析形成趋势越加明显，制约着高级别大断面合金钢连铸圆坯母材制备。鉴于目前大断面合金钢圆坯V形通道偏析形成机理研究尚不系统深入和控制手段缺乏的现状，本项目拟首先采用Thermo-Calc热力学软件定量分析钢种成分组元相互作用对合金钢凝固行为的影响规律。然后，重构连铸坯凝固末端糊状区枝晶形貌，揭示糊状区枝晶网状结构特征与晶间网络渗流之间的定量关系。其次，采用体积平均法建立宏微观多尺度溶质偏析数学模型，定量描述热溶质浮力和凝固收缩共同下糊状区凝固前沿界面失衡，晶间滑移和浓缩钢液汇集行为，揭示对流和热溶质扩散共同作用下V形通道偏析形成及演变规律。最后，阐明连铸坯凝固末端线性电磁搅拌对糊状区凝固收缩和压降抑制作用规律，开发连铸坯V形通道偏析靶向控制手段，提升大断面合金钢圆坯内部质量，为高级别大断面合金钢圆坯连铸提供理论指导和技术手段支撑。

The trend of V-channel segregation formation in large round bloom of alloy steel becomes more significant with the increase of section size and alloy element, and thus limits its production. Unfortunately, the V-channel segregation formation is controversial and countermeasures are lack in large round bloom of alloy steel. Therefore, this study plans to firstly investigate the effects of alloy element on the solidification behavior of alloy steel by Thermo-Calc thermodynamic software. Then, the dendrite morphology in the mushy zone of continuously cast bloom was reconstructed to reveal the quantitative relationship between the dendrite morphology parameters and the permeability of dendritic structure. Later, a multiscale mathematical model of solute segregation in mushy zone of round bloom is developed by a volume average method, and adopted to study the interface stability of solidification front, dendrite motion, intergranular slip and solute enrichment, and reveal the formation and evolution of V-channel segregation under the interaction of thermosolutal buoyancy and solidification shrinkage. Finally, the effect of linear electromagnetic stirring at the solidification end of round bloom on the inhibition of solidification shrinkage and pressure drop in the mushy zone is clarified and the targeting control of V-channel segregation in the large round bloom of alloy steel. Consequently, according to the above mentioned study, a fundamental theory of V-channel segregation formation and targeting control method are provided for the large bloom continuous casting of high quality alloy steel.