Formation of macrosegregation by multicomponent thermosolutal convection during the solidification of steel
Formation of macrosegregation by multicomponent thermosolutal convection during the solidification of steel
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DOI：
10.1007/bf02671251
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发表时间：
1995-09
期刊：
影响因子：
--
通讯作者：
M. Schneider;C. Beckermann
中科院分区：
文献类型：
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作者：
M. Schneider;C. Beckermann
通过固液界面热力学平衡，同时求解宏观质量、动量、能量和物质守恒方程，模拟了钢凝固过程中由多组分热溶质对流形成的宏观偏析。给出了四种情况下的流场、固体分数演化和宏观偏析模式。结果表明：沟道分离的形成和被大块熔体包围的糊状岛的形成。在检查十元素钢的凝固过程中，发现元素的宏观偏析的整体程度与它的分配系数呈线性关系（较小的分配系数更严重的偏析），尽管局部不可能发生这种缩尺。二元Fe-C合金（与十元合金含碳量相同）的凝固结果与十元合金的凝固结果相似，这仅仅是因为所选的十元钢中碳对浮力驱动流动的贡献很大。虽然只包括那些对浮力驱动流动有重要贡献的元素，再现了在十元素合金中看到的宏观偏析的全球范围，但预测中的局部差异是可见的。最后，用两组不同的数据来描述分配系数和液相温度随元素浓度的变化，对同一种十元钢的凝固结果进行比较，结果显示出完全相反的行为，即：一种情况下向上流动通过糊状区，另一种情况下向下流动。因此，在建模多组分宏观偏析时需要精确的相平衡数据。总之，结果表明，如果要完成多组分凝固的精确建模，需要对哪些区域进行更仔细的检查。
The formation of macrosegregation by multicomponent thermosolutal convection during the solidification of steel is simulated by simultaneously solving macroscopic mass, momentum, energy, and species conservation equations with full coupling of the temperature and concentrations through thermodynamic equilibrium at the solid/liquid interface. The flow field, solid fraction evolution, and macrosegregation patterns for four cases are presented. The results show both the formation of channel segregates and the formation of islands of mush surrounded by bulk melt. In examining the solidification of a ten-element steel, the global extent of macrosegregation of an element is found to be linearly dependent on its partition coefficient (more severe segregation for small partition coefficient), although such scaling is not possible locally. Results for the solidification of a binary Fe-C alloy (with the same carbon content as the ten-element alloy) are similar to those for the ten-element alloy due solely to the large contribution of carbon to buoyancy driven flow in the ten-element steel chosen for study. While including only those elements that make significant contributions to buoyancy driven flow reproduces the global extent of macrosegregation seen in the ten-element alloy, local differences in the predictions are visible. Finally, comparison of results for the solidification of the same ten-element steel using two different sets of data to describe the partition coefficients and change in liquidus temperature with concentration of the elements shows completely opposite behavior,i.e., upward flow through the mushy zone for one case and downward flow for the other. Thus, the need to have accurate phase-equilibrium data when modeling multicomponent macrosegregation is illustrated. Together, the results give an indication of what areas require more careful examination if accurate modeling of multicomponent solidification is to be accomplished.