异径双辊薄带铸轧钢液初始凝固的传热特性

Numerical Study on Heat Transfer Characteristics at the Initial Solidification Stage During Unequal Twin Roll Strip Cast Rolling

采用有限差分和二维非稳态凝固传热模型，应用边界适体坐标（ Ｂ Ｆ Ｃ） 技术对异径双辊薄带铸轧熔池中钢液的初始凝固传热特性进行了数值仿真·分析了铸轧起始阶段熔池内温度场的发展变化及辊面凝固薄壳的生长过程，指出１００ ｓ 为适宜的起始铸轧时间，此时凝固末端距熔池出口约９ ～１０ ｍ ｍ·探讨了钢液过热度、辊壁内表面与冷却水的对流换热系数和辊壁导热热阻等设计及操作工艺参数在起始铸轧阶段对钢液的凝固传热及凝壳形成的影响，结果发现辊壁是制约熔池中凝固传热的重要因素，直接影响着凝壳的快速生长·

The finite difference method and 2 D transient heat transfer model were applied to the numerical simulation for the development of temperature distribution patterns in the molten pool and in the solidified metal layer formed on the surfaces of two opposite rotating rolls during the early stage of unequal diameter twin roll strip cast rolling process. The technique of boundary fitted coordinate systems (BFC) was employed to deal with the irregular molten pool geometry. The solidified layer growth in thickness with time can be obtained by the calculated results. The results show that the proper withdrawal time is about 1 00?s and the distance between the solidification front and the exit is 9～10?mm at the time. The superheat of molten steel,heat transfer coefficent between inner cooling water and rolls and thermal conductivity of rolls were discussed to provide the guidelines for operation parameters. The analysis reveals that the thermal property of the rolls is the key factor to influence the growth of initial solidification thin shell.