φ200mm断面37Mn5钢凝固过程数学模型及在提拉速中的应用

Mathematic Simulation on Solidification Process of φ200mm Round Billet of 37Mn5 and Applied Research on Increasing Casting Speed

基于ANSYS建立37Mn5钢φ200mm断面圆坯连铸过程中的凝固传热数学模型,并通过射钉试验及表面测温对模型的准确性进行了验证,模拟研究了拉速、过热度以及比水量对凝固终点、铸坯表面温度以及铸坯中心过热消散位置的影响,研究结果证明:比水量对铸坯表面回温影响最大,每增加0.1L·kg^(-1),铸坯表面回温增加10℃,而拉速对凝固终点及铸坯中心的过热消散的位置影响最大,拉速每增加0.1m·min^(-1),凝固终点及铸坯中心的过热消散的位置分别增加1.1m和0.8m,并从理论上验证了φ200 mm断面生产37Mn5拉速从1.4m·min^(-1)提高到1.8m·min^(-1)的可行性,另外考虑到37Mn5的高温热塑性特点及二冷冶金准则,针对铸坯存在的质量缺陷,优化二冷工艺制度,工业试验结果表明:低过热度(25℃以下),比水量为0.3L·kg^(-1),拉速从1.4m·min^(-1)提高到1.8m·min^(-1)时,铸坯低倍质量良好,无内裂纹以及中心缩孔,中心等轴晶率为35%,但过高的过热度(30℃以上)会存在中心缩孔。

A mathematical model of solidification and heat transfer for φ200mm round billet on 37Mn5 was established with ANSYS software, which was verified by nail-shooting experiments and surface temperature testing. The effect of casting speeds, specific water flow rate and superheat on surface temperature, position of crater end and superheat dissipation in central area of round billet were respectively investigated by simulations, whose results proved that specific water flow rate had the greatest impact on surface temperature and 0.1L·kg^-1 increase in spe- cific water flow rate was associated with each additional 10℃ in surface temperature returning; Casting speed had the most effects on position of crater end and superheat dissipation in central area of round billet and every 0.1m·min^-1 increase in casting speed corresponded to 1.1m increase in position of crater end and to 0.8m in the location where superheat dissipated in central area of round billet separately; In addition, it was proved feasible theoretically that casting speed increased from 1.4m·min^-1 to 1.8m·min^-1 for φ200mm round billet on 37Mn5. In view of high temperature hot ductility on 37Mn5 and secondary cooling metallurgical criteria, law of secondary cooling was optimized. Plant trials results have shown that casting speed increased from 1.4m·min^-1 to 1.8m·min^-1 with specific water flow rate 0.3L·kg^-1 and lower superheat below 25℃, the internal quality of round billet improved significantly and the defects such as center shrinkage cavity, intermediate cracks decreased obviously and center equiaxial crystal zone of round billet was 35% , but center shrinkage cavity appeared with higher superheat above 30℃.