电磁搅拌对钢坯凝固过程中热工参数的影响

采用自行设计的单侧冷却凝固实验装置进行了有无电磁搅拌作用下钢坯的凝固实验,并通过计算机数据采集系统对钢坯凝固过程中的各种热工参数进行了实时测试和分析·研究结果表明:施加电磁搅拌以后,钢坯凝固初期的铸型热流量明显增加,促进了铸型内钢液过热的耗散,使得钢坯内的温度分布趋于均匀,降低了凝固前沿的温度梯度·这不仅抑制了柱状晶的发展,同时易于在钢液内部同时形核,有利于等轴晶凝固组织的形成,使得钢坯的等轴晶比率由无电磁搅拌作用下的47%提高到76%·这也说明了电磁搅拌促进钢液中的过热耗散是提高铸坯凝固组织中等轴晶比率的重要原因之一·

Influence of Electromagnetic Stirring on the Thermal Parameters of Steel Solidification Process

An experiment of the solidification process of steel billets under linear electromagnetic stirring (EMS) was carried out on a special setup of which a unilateral water cooling copper plate was mounted to the mould. A computer dynamic data acquisition system was provided to perform real-time measurements of some heat exchange parameters during the solidification of steel. The results showed that in the mould the heat flux increases obviously in initial solidification period under the action of EMS to expedite the overheat dissipation in molten steel. Thus, the internal temperature of the ingots tends to be distributed uniformly with the temperature gradient at the solidifying front reduced. As a result, the growth of columnar grain is suppressed, which will be helpful to the nucleation in molten steel and the formation of equiaxed grain solidification structure. Therefore, the rate of equiaxed grains in ingots with EMS can be improved to 76% from 47% without EMS. The fact indicates that the overheat dissipation in molten steel with EMS is one of the key factors to increase the rate of equiaxed grains in the solidification structure.