考虑固相移动的大尺寸钢锭宏观偏析数值模拟

以欧拉方法和体积元平均技术为基础，建立考虑固相移动的大尺寸钢锭宏观偏析数学模型.研究了纯自然对流和包含固相移动两种情况下宏观偏析形成的模式，分析了临界固相分数和固相密度变化对宏观偏析形成的影响.计算结果表明：无论是否考虑固相移动，A型偏析形成机理是侧壁形成的固相与底部形成的固相之间形成狭窄的补缩通道，此通道内溶质富集且流动不顺畅，最后形成了高成分区域.增大临界固相分数会导致A型偏析带和底部负偏析的加剧.固相密度的增加会引起底部负偏析和顶部正偏析的偏析程度增大，但A型偏析带的长度不随固相密度的增加而增长.将模拟结果和实验结果进行对照，验证了模型的准确性.关键词：宏观偏析固相移动A型偏析形成数值模拟

Modelling of macrosegregation in large steel ingot with considering solid movement

Based on the Eulerian and the volume averaging methods, a mathematical model of macrosegregation formation with considering solid movement during solidification of large steel ingot is developed. The cases with and without solid movement are studied and compared. The result shows that the A segregation band results from a narrow channel that forms around the position where the solidified shell in the horizontal direction meets the one in the vertical direction, which serves as a barrier to the fluid flow, leading to the accumulation of solute. Effects of critical solid fraction and density of solid on evolution of macrosegregation are investigated. The results indicate that both the positive segregation in the A segregation band and the bottom negative segregation become more pronounced with the critical solid fraction increasing. As the density of solid increases, stronger macrosegregations occur at the upper and bottom parts of the ingot. However, the length of A segregation band is not increased with density of solid. Calculated results show good agreement with experimental ones, except a larger bottom negative segregation zone.