垂直连铸凝固过程的数值模拟研究

采用基于Eulerian-Eulerian方法和合金凝固理论的液相-柱状晶-等轴晶三相凝固模型，对立式连铸工艺中结晶器内的凝固过程进行了研究.对比焓-多孔介质凝固模型，除热溶质浮升力导致的熔体流动，该三相凝固模型还考虑了柱状晶组织的生长、等轴晶组织的形成和演变以及游离等轴晶粒的沉浮，揭示了等轴晶沉降漂移作用对宏观溶质传输及凝固组织分布的影响.模拟结果显示铸坯中心处由等轴晶粒沉积形成的富等轴晶区存在溶质负偏析，紧邻该负偏析区域存在带状偏析区域.随着钢液过热度增加，等轴晶分布减少，中心处宏观偏析加重.

Numerical Simulation of Solidification Process During Vertical Continuous Casting

Solidification process in a vertical continuous casting was numerically simulated using a three-phase (mixed liquid-columnar-equiaxed grain) solidification model based on Eulerian-Eulerian approach and metal/alloy solidification theory. Comparing with the single-phase solidification model， more detailed phenomenons in addition to the thermo-solute natural convection are predicted， such as the evolutions of columnar and equiaxed grains， floatation/sedimentation of equiaxed grains can be predicted， which greatly affects the macroscopic solute transport and development of as-cast structure. The simulation results show that negative segregation occurs in the center of the billet， which filled with deposited equiaxed grains and next to this center， a ribbon segregation regions are observed. With the increasing superheat of molten steel， the region of equiaxed grain decreases and the macrosegregation at the center increases.