In the current study, an improved three-dimensional macrosegregation model for the full-length curved continuous casting bloom was established, and the fluid flow, heat transfer, solidification, and macrosegregation were calculated. The calculation domain was divided into four regions: the liquid zone, the columnar zone, the free-floating equiaxed zone, and the porous equiaxed zone. The columnar zone and the equiaxed zone were distinguished according to the cooling rate on the iso-surface of a 0.8 liquid fraction, where it was the columnar zone if the cooling rate was higher than the critical cooling rate of 0.03 °C/s; otherwise, it was the equiaxed zone. Governing equations of the porous zone were used for the columnar zone and the mushy zone coefficient was non-isotropic. In the equiaxed zone, if the solid fraction was higher than 0.5, it was the porous zone where dendrite arms of equiaxed crystals contacted each other forming solid networks and equiaxed crystals hardly moved freely with the liquid phase, and governing equations of the porous zone were used while the mushy zone coefficient was isotropic. If the solid fraction was less than 0.5, it was the free-floating zone where equiaxed crystals moved freely with the liquid phase, and the molecular viscosity of the steel depended on its solid fraction. Since free-floating dendrites were considered in the improved model, in addition to predicting the negative segregation in the subsurface of the bloom and the positive segregation in the bloom center, the negative segregation after the columnar-to-equiaxed transition(CET) zone was also able to be predicted. With the casting speed of 0.42 m/min and superheat of 29 °C, the calculated carbon content was 0.170, 0.190, and 0.268 pct in the subsurface of the bloom, after the CET zone and the bloom center, respectively.

本研究建立了改进的全长弯曲连铸大方坯三维宏观偏析模型，计算了流体流动、传热、凝固和宏观偏析。计算域分为四个区域：液体区、柱状区、自由浮动等轴区和多孔等轴区。柱状区和等轴区是根据0.8液体分数等值面上的冷却速率来区分的，如果冷却速率高于0.03℃/s的临界冷却速率，则为柱状区；否则，它是等轴带。柱状区采用多孔区控制方程，糊状区系数为非各向同性。在等轴区，如果固体分数高于 0.5，是等轴晶枝晶臂相互接触形成固体网络的多孔区，等轴晶几乎不随液相自由移动，采用多孔区控制方程，糊状区系数为各向同性。如果固相分数小于0.5，则为自由浮动区，等轴晶体随液相自由移动，钢的分子粘度取决于其固相分数。由于在改进模型中考虑了自由浮动的枝晶，除了预测大方坯亚表面的负偏析和大方坯中心的正偏析外，柱状到等轴过渡（CET）区后的负偏析是也可以预测。连铸速度为 0.42 m/min，过热度为 29 °C，