慢速凝固对特厚板坯宏观组织的影响

Effect of slow solidification rate on macrostructure of ultra-thick slab

基于CA-FE和KGT模型,采用薄片移动边界法对2 200 mm×300 mm断面的特厚板坯进行凝固过程的数值模拟,探究慢速凝固对特厚板坯凝固组织中柱状晶的长度与偏转角及等轴晶的大小和等轴晶率的影响。结果表明:特厚板坯宏观组织的模拟结果与现场铸坯低倍组织一致;当过热度为30℃时,随着凝固速率的逐渐降低,柱状晶的平均长度由19.18 mm减小到9.58 mm,偏转角减小并趋于正向生长;中心等轴晶率由30.49%增大到41%,等轴晶的平均面积由6.05 mm2/个增大到9.74 mm2/个。

Based on CA-FE and KGT models,numerical simulation on the solidification process of a 2200 mm x 300 mm cross-section ultra-thick slab was carried out by using slice moving boundary method. Effects of slow solidification rate on the length and the deflection angle of a columnar crystal and on the size and the ratio of an equiaxed crystal in the solidified structure of an ultra-thick slab were investigated. The present investigation results show that the simulated macrostructure morphology in the ultra-thick slab is consistent with that under low magnification shown in the practical case. When the superheat is 30°C,as the solidification rate decreases the average length of columnar crystals shortens from 19.18 mm to 9.58 mm and the deflection angle diminishes and tends to grow straightforward whereas the proportion of the growth area of equiaxed crystals gradually increases from 30.49% to 41% corresponding to an increase of the growth area from 6.05 mm^2 to9.74 mm^2.