Abstract

Macrosegregation is the major defect in large steel ingots caused by solute partitioning and melt convection during casting. In this study, a three-phase (liquid, columnar dendrites, and equiaxed grains) model is proposed to simulate macrosegregation in a 36-t steel ingot. A supplementary set of conservation equations are employed in the model such that two types of equiaxed grains, either settling or adhering to the solid shell, are well simulated. The predicted concentration agrees quantitatively with the experimental value. A negative segregation cone was located at the bottom owing to the grain settlement and solute-enriched melt leaving from the mushy zone. The interdendritic liquid flow was carefully analyzed, and the formation of A-type segregations in the mid-height of the ingot is discussed. Negative segregation was observed near the riser neck due to the specific relationship between flow direction and temperature gradient. Additionally, the as-cast macrostructure of the ingot is presented, including the grain size distribution and columnar-equiaxed transition.

中文翻译：

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使用多相模型模拟36吨钢锭中的宏观偏析

摘要

宏观偏析是大型钢锭的主要缺陷，是铸造过程中溶质分配和熔体对流引起的。在这项研究中，提出了一个三相模型（液态，柱状枝晶和等轴晶）来模拟36吨钢锭中的宏观偏析。在模型中使用了一组补充的守恒方程，以便很好地模拟两种类型的等轴晶粒（沉降或附着在固体壳上）。预测浓度与实验值定量一致。负的偏析锥位于底部，这是由于颗粒沉降和浓稠的熔体从糊状区排出而造成的。仔细分析了枝晶间的液流，并讨论了铸锭中部高度A型偏析的形成。由于流向和温度梯度之间的特定关系，在立管颈部附近观察到负偏析。此外，还介绍了铸锭的铸态宏观结构，包括晶粒尺寸分布和柱状等轴转变。