圆坯连铸过程中坯壳生长规律

Shell growth of round blooms during continuous casting

采用ANSYS软件建立了圆坯连铸过程的二维凝固传热模型,通过射钉实验以及表面温度的测定对模型进行了实验验证.结果表明模型能较准确地得到任意位置处铸坯坯壳厚度以及预测凝固终点位置.在传热模型的基础上结合铸坯低倍观察着重分析了圆坯坯壳生长规律.发现圆坯凝固过程中柱状晶区坯壳的厚度与凝固时间的平方根呈线性关系,符合平方根定律,并对平方根定律进行了修正,修正项与过热度和凝固速率有关;铸坯中心等轴区坯壳厚度与凝固时间平方根为非线性关系,凝固坯壳的生长不再符合平方根定律;间接证明了圆坯柱状晶生长是单方向传热,等轴晶生长时传热方向不唯一.

A two-dimensional mathematical model of solidification and heat transfer for round blooms was established with ANSYS software, and it was verified by nail-shooting experiment and surface temperature testing. The solidified shell thickness distribution at any fixed location in the casting direction and the position of the solidification end point can be accurately obtained by using this mod- el. Combining the model results with the macrographs of samples, it is found that the shell thickness and the square root of solidifica- tion time show a linear relationship in the columnar crystal zone, which fits a solidification square root law. The law is corrected, and the correction term is relevant to the superheat and solidification velocity. The relationship between the shell thickness and the square root of solidification time in the equiaxed crystal zone is not fit for the solidification square root law. It is indirect argument that heat transfer during columnar crystal solidification is unidirectional, but heat transfer during equiaxed crystal solidification is in multiple di- rections.