论文部分内容阅读
基于Eulerian-Eulerian方法,阐述了简化枝晶状等轴晶、柱状晶以及金属液三相完全混合的凝固模型.模型考虑了等轴晶的移动及柱状晶对等轴晶的捕获,跟踪了柱状晶尖端的位置并考虑了等轴晶和柱状晶的相互竞争生长,因此该模型具备了预测柱状晶向等轴晶转变(CET)的能力;为了在不过量增加计算量的前提下提高模型的精度,模型对等轴晶采取了简单的枝晶化处理,即采用简化方法描述等轴晶包络线内固相分数.分别模拟了3.25和25 t钢锭的凝固过程,成功预测了大型钢锭凝固过程所形成的底部锥形负偏析、“类-A型”偏析以及CET等现象.分析认为长细形状铸锭中出现的顶部负偏析区,是由于凝固后期所形成的局部小钢锭及等轴晶在其内部的沉积聚集而成.
Based on the Eulerian-Eulerian method, the solidification model that simplifies the complete mixing of dendritic equiaxed grains, columnar grains and liquid phases is described. The model takes into account the movement of equiaxed grains and the capture of equiaxed grains by columnar grains, Crystal tip position and consider the competing growth of equiaxed and columnar crystals, so the model has the ability to predict the columnar to equiaxed crystal transformation (CET); in order to increase the amount of calculation without excessive increase in the model Accuracy and model, the simple equiaxed grains were treated by simple dendritic method, that is, a simplified method was used to describe the solid fraction in the equiaxed grain envelopment.The solidification process of 3.25 and 25 t ingot were simulated respectively, and the solidification of large ingot was successfully predicted The process of the formation of the bottom of the cone-shaped negative segregation, “class-A type ” segregation and CET and other phenomena.Analysis that the top of the thin slab shape appear in the top of the negative segregation zone is due to the late solidification of the formation of local small ingot and Equiaxial grains accumulate in their interior.