Abstract: In order to improve the solidification structure of steel 20CrMnTi billet, based on the CAFE model in ProCAST software, the solidification structure is numerically simulated, and the effects of different superheat of molten steel, casting speed of billet and secondary cooling water ratio on the solidification structure are studied. The simulation results show that with decreasing the superheat of molten steel, and increasing cast speed, and decreasing the specific water a- mount of secondary cooling can increase the equiaxed grain ratio and refine the grain size of the billet, and the superheat of molten steel has the most influence on it； the equiaxed grain rate increases by 3. 7% with the decrease of superheat by 10°C ；the equiaxed grain ratio of the casting billet increases by 1. 8% on average when the cast speed increases by 0.1 m/ min； and the equiaxed grain ratio of the billet increases by 1. 65% when the specific water amount decreases by 0. 1 L/kg. Production application shows that with superheat of molten steel 30 °C，as cast speed decreases from original 2. 2 m/min to 2. 1 m/min, secondary cooling specific water amount inceases from 0. 6 L/kg to 0. 7 L/kg, the billet center porosity obvously decreases.

摘要： 为改善20CrMnTi钢小方坯凝固组织,基于ProCAST软件中的CAFE模型,对其凝固组织进行数值模拟,研究了不同钢水过热度、铸坯拉速、二冷比水量对凝固组织的影响。模拟结果表明,降低钢水过热度、提高铸坯拉速、降低二冷比水量均可达到增大铸坯等轴晶率和细化晶粒的目的,其中过热度对其影响最大。过热度每降低10℃,等轴晶率平均增加3.7%;拉速每增加0.1 m/min,铸坯等轴晶率平均增加1.8%;比水量每降低0.1 L/kg,铸坯等轴晶率平均增加1.65%。生产应用表明,钢水过热度30℃时,当拉速由原2.2 m/min降低至2.1 m/min,二冷比水量由0.6 L/kg提高至0.7 L/kg,铸坯中心疏松明显减少。