采用凝固过程和对流条件与碳钢相似的NH_4Cl水溶液模拟实验,研究了铸锭凝固过程中的对流及液相区的成分变化。染色液示踪的结果表明,dρ_L/dT_L>0的溶液凝固过程中,侧向凝固的两相区中液相向上流动,并自上部流入液相区后,浮在液相区的上部形成一个弱对流区(第Ⅲ对流区)。随着来自两相区液相的不断补充,该区向下扩展。成分分析发现,第Ⅲ对流区内NH_4Cl浓度低于原液相区。向溶液中加入Na_2SO_4或NaI·2H_2O可以平衡两相区内液相密度的变化,抑制两相区的流动和第Ⅲ对流区的形成,从而消除液相区上部的低NH_4Cl区。
Convection and constitution variation of liquid metal during solidifi-cation has been studied using NH_4Cl agueous solution. The liquid in mushy zoneattached to the side wall of the mold will flow upward and forms a low concen-tration region, in which no significant convection occurs, on the top of liquidzone. This region develops downward gradually during solidification. Addition ofadequate component may suppress the formation of this region.
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