A four-phase solidification model is introduced to comprehensively investigate the formation of macrosegregation, especially the A-segregation during the solidification of a 55-ton ingot (Fe-3.3 wt pct C). The model considers the simulations of melt convection, shrinkage, dendritic equiaxed grains nucleation and sedimentation, and competitive growth of solid phases, etc. The final patterns of macrosegregation, especially the A-segregation, fit well with experimental results including the characteristics and location. The results show that the A-segregation always exists close to the columnar-to-equiaxed transition zone, which results from the melt flow collision occurring in the triangle area of the mushy zone that composed dendritic equiaxed grains zone, liquid zone, and columnar and equiaxed crystals mixed zone. In addition, the A-segregation evolves with the changing of the columnar-to-equiaxed transition zone, which indicates that the A-segregation occurrence has a correlation with the columnar-to-equiaxed transition zone in large-scale ingots.

引入四相凝固模型，全面研究宏观偏析的形成，特别是55吨铸锭（Fe-3.3 wt pct C）凝固过程中的A偏析。该模型考虑熔体对流，收缩，树枝状等轴晶粒的成核和沉淀，和固相竞争生长，的模拟等. 宏观偏析的最终模式，特别是A偏析，与包括特征和位置在内的实验结果非常吻合。结果表明，A偏析始终存在于柱状至等轴过渡区附近，这是由树枝状等轴晶区、液相区和柱状晶区组成的糊状区三角形区域发生熔体流动碰撞的结果。等轴晶混合区。此外，A偏析随着柱状至等轴过渡区的变化而演变，这表明A偏析的发生与大尺寸铸锭中柱状至等轴过渡区具有相关性。