基于Eulerian-Eulerian多相流框架，建立了液相-等轴枝晶-柱状晶(L-D-C)三相传输模型，模型追踪柱状晶尖端生长位置及等轴枝晶被捕获过程，预测了等轴枝晶运动、相间耦合及柱状晶-等轴晶转变(CET)对2.45 t Fe-0.45%C (质量分数)钢铸锭宏观偏析的影响规律。预测获得的底部锥形负偏析最大值约至-0.27，负偏析锥高度约至2/3锭高，与文献实验测量值(负偏析最大值为-0.13、负偏析锥高度约为2/3锭高)相符。增大的液-等轴晶相间动量交换系数会增强液-固耦合、减弱等轴晶相对滑移能力，改变CET位置，进而重塑锭型偏析条带的形态与强度；仅降低热顶换热可将热顶处正偏析极值由0.76降至0.26，但会加重热顶下方过渡区正偏析带。侧壁梯度冷却协同热顶保温制度，使铸锭中心线处最大正偏析预测值由0.76 降至0.10，最大负偏析预测值由-0.27降至-0.12，有效抑制铸锭顶部正偏析、热顶下方A型偏析及底部负偏析。

Large steel ingots are widely used in heavy-duty equipment for the nuclear power, hydropower, and metallurgical industries. However, severe macrosegregation induced by thermosolutal convection, grain sedimentation, and solidification shrinkage during solidification deteriorates the chemical homogeneity and service reliability of ingots. To understand the macrosegregation formation mechanism and develop effective control strategies, a mixed columnar dendritic-equiaxed three-phase solidification model was developed within the framework of the Eulerian-Eulerian approach. By tracking the position of the columnar dendrite tip and capturing the equiaxed dendrites at the columnar front, the effects of the equiaxed-dendritic grain movement, interphase momentum exchange, and columnar-to-equiaxed transition (CET) on macrosegregation in a 2.45 t Fe-0.45%C (mass fraction) steel ingot were investigated. The predicted maximum negative segregation at the ingot bottom reaches approximately -0.27, and the length of the conical negative segregation zone is approximately 2/3 of the ingot’s height. These results are consistent with the experimental measurements reported in the literature. Increasing in interphase momentum exchange intensity between the liquid and equiaxed phases enhances the liquid-solid coupling and weakens the relative slip of equiaxed grains, thereby shifting the CET position and further reshaping the morphology and intensity of the V-segregation bands. Reducing the heat transfer intensity at the hot top decreases the maximum positive segregation there from 0.76 to 0.26. However, the positive segregation bands in the transition zone beneath the hot top worsen. The combined scheme of sidewall gradient cooling and hot-top insulation reduced the maximum positive segregation along the ingot centerline from 0.76 to 0.10 and the maximum negative segregation from -0.27 to -0.12, effectively suppressing the positive segregation at the ingot top, A-segregation beneath the hot top, and the negative segregation at the ingot bottom.