Fe-C系合金铸锭因C元素分配系数小、铸锭尺寸较大，易产生C偏析缺陷；同时因合金液-固相密度差异以及铁素体、奥氏体等相密度的差异都易产生并加剧凝固收缩。对凝固收缩的模拟研究表明，气相(渣相)的引入对偏析影响甚微，主要起补充顶端收缩腔的作用，但却导致气-合金界面模拟困难。为了简化模拟的复杂性，本工作基于液-固混相的连续介质模型，将凝固过程中收缩的体积与固相区、糊状区及液相区下降的体积建立关联，从而确定熔体顶端边界；结合动网格技术，开发了一种追踪收缩腔界面的模型，实现了Fe-C合金铸锭凝固收缩和宏观偏析的耦合模拟，预测的收缩腔形状与实验相符。结果表明：Fe-0.3%C合金铸锭凝固过程中，在热-溶质浮升力影响的基础上，考虑凝固收缩后，预测的铸锭顶部正偏析最大值减少了4.78%。铸锭顶端界面的换热，会减轻铸锭顶端正偏析。耦合热-溶质浮升力及凝固收缩影响，顶端与环境换热系数为h = 2.0 W/(m²·K) 的铸锭上部溶质分布更符合文献实验测量结果。在热-溶质浮升力影响的基础上，考虑凝固收缩增强了糊状区内溶质浮力影响，致使铸锭凝固前沿主流股旋流方向更快反转，熔钢流速超过仅考虑热-溶质浮升力时的流速，从而加快了铸锭凝固速率。本模型预测的铸锭底端负偏析小于文献实验结果，这是由于本模型仅考虑了液-柱状晶混相，进一步的模型中需加入等轴晶粒沉降的影响。

Macrosegregation is the mutual contribution of many factors, such as thermo-solutal buoyancy-induced flow, solidification shrinkage, and grain movements, during alloy solidification. Fe-C-based alloy ingot is apt to form carbon segregation due to C's relatively small partition coefficient and the large ingot cross-section size. Moreover, it is also easy to generate solidification shrinkage because of the density difference between the liquid and solid and among ferrite, austenite, and other solids in the alloy. The numerical studies on solidification shrinkage show that introducing the air (or slag) phase mainly fills up the shrinkage cavity, which appears in the top part of the ingot. Although it has minor effect on segregation, it creates severe difficulty in solving the continuum transport equations at air-alloy interface owing to the large difference in their physical properties, such as density and thermal conductivity. A method that tracks the boundary profile of the cavity due to solidification shrinkage was developed in the present work to study macrosegregation under solidification shrinkage while avoid solving the air-alloy interaction. Macrosegregation under solidification shrinkage in Fe-C alloy ingot was predicted through the traditional liquid-solid mixed continuum model. To this end, the melt-air interface position was determined through allocating the shrink in volume to the solidified, mushy and liquid zones by the dynamic mesh technique. The predicted shape of the shrinkage cavity was fitted with the experimental one in the literature. Comparing the impact of thermo-solutal buoyancy showed that the predicted maximum positive C segregation at the top part of the Fe-0.3%C alloy ingot decreased by 4.78% with the additional consideration of solidification shrinkage. However, the heat exchange between the surroundings' and ingot's top surface reduced the positive C segregation near the latter. The C concentration distribution at the upper part of the ingot was more consistent with the experimental results in the literature when a heat transfer coefficient of 2.0 W/(m²·K) was adopted at the ingot's top surface, besides the effects of the thermo-solutal buoyancy and solidification shrinkage are considered. Compared with the thermo-solutal buoyancy influence, the solidification shrinkage enhanced the solutal buoyancy impact in the mushy zone. This made a faster reverse circulation in the mainstream ahead of the solidification front and led to the maximum flow velocity all over the molten steel exceeding that of mere thermo-solutal buoyancy during the solidification. All of them accelerated the overall solidification rate of the ingot. However, the predicted negative segregation at the lower part of the ingot was lower than the experimental data in the literature because the present continuum model only consisted of a liquid-columnar mixture. The movement of equiaxial grains needs to be included in further consideration.