为控制油井管用连铸圆坯的质量，基于薄片移动法建立了连铸圆坯凝固传热数学模型，并应用Procast软件的CA-FE模块对37Mn5钢150mm圆坯凝固组织进行了模拟。中心等轴晶率模拟结果与工业试验检测结果相一致，据此，建立了柱状晶-等轴晶转变判据。基于此判据的中心等轴晶率预测结果表明，降低过热度、提高拉速和降低二冷零段冷却水分配比均能够降低固液混合区的温度梯度，扩大过冷区范围，有利于晶体的形核与长大，进而阻止柱状晶的生长，使柱状晶提前向等轴晶转变，中心等轴晶率提高。综合考虑圆坯中心等轴晶率、表面和内部裂纹控制及浇铸安全和生产率，37Mn5钢150mm圆坯合适的连铸工艺参数为：过热度为(20±5)℃，拉速为25m·min-1，二冷水分布为35∶28∶26∶11。
To control the quality of continuous casting round billets used for oil well pipes, a mathematical model based on slice moving method was developed for the solidification and heat transfer process of the round billet. Then, a mathematical simulation was done using the CA-FE module of Procast software for the solidification process of the 150mm round billets of 37Mn5 steel. As a result, the simulated equiaxed crystal ratio was in accordance with testing results of industrial experiments, and then the criterion of columnar to equiaxed transition was found. The prediction results show that, with decreasing of superheat, increasing of continuous casting velocity and decreasing of second cooling water distribution in the first second cooling zone, the thermal gradient decreases and the undercooled liquid region ahead of the columnar dendrite tips becomes wider. Thus, the density of the grains nucleated in the solid-liquid region increases and their growth enough stops the columnar front, so the columnar to equiaxed transition occurs earlier and equiaxed crystal ratio increases. Considering controlling of equiaxed crystal ratio and surface and internal cracks, casting security and productivity synthetically, the suitable continuous casting parameters are as follows: superheat is (20±5)℃, continuous casting velocity is 25m·min-1, second cooling water distribution is 35∶28∶26∶11.
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