材料期刊网

在浸入式水口外部采用可移动的旋转电磁场装置, 使水口内钢液形成旋转流动.通过对磁场和流场的数值模拟, 分析了电磁参数和电磁旋流装置结构对钢液内磁感应强度和旋流速度大小及分布的影响. 结果表明, 钢液中心竖直轴线上的磁感应强度随线圈电流增大而增大, 随频率增大而减小. 采用圆形磁体时磁感应强度最大且分布均匀, 优于马蹄形磁体; 线圈电流500 A, 频率50 Hz时, 获得了在圆形装置作用下浸入式水口内及结晶器内的钢液的速度矢量分布, 此时结晶器内产生了较强的旋流流动. 从现场操作角度出发,提出了改进马蹄形电磁旋流装置. 通过低熔点合金的电磁旋流实验验证了数值模拟的结果及计算方法的可靠性.

Swirling flow in an immersion nozzle generated with a swirl blade in it has been proved to be effective to reduce the meniscus fluctuation and homogenize the distribution of temperature in a mold during continuous casting of steel. However, this process has insuperable limitations: the swirling flow intensity can not be regulated to meet the process operation needs; the immersion nozzle with blade is liable to clog, leading to its low life span; and frequent replace of a nozzle in casting may cause operational difficulties. In this study a new process that a rotating electromagnetic field was set up around the immersion nozzle to induce a swirling flow in it by Lorentz force, has been proposed. In this case, te same effects as the swirl blade can be achieved without the above limitations. Four types electromagnetic stirrers, such as round, half round, U–shaped and modified U–shaped, were used in the simulation and their effects of structure, coil current intensity and magnetic field frequency on the magnetic field distribution and the flow filed in the immersion nozzle and mold during the round billet continuous casting of steel were numerical simulated and analyzed. The simulated results show that the magnetic flux density is the largest and magnetic field distribution is most uniform under the round electromagnetic stirrer. By using round electromagnetic stirrer, 500 A coil current intensity and 50 Hz frequency will induce a strong swirling flow and reversing flow in the mold. The distribution of flow field under the modified U–shaped stirrer is better than that under the U–shaped, and closer to that uner the round one. Considering the operational difficulty to replace the nozzle etc., the modified U–shaped electromagnetic stirrer is a better alternative to the round stirrer. The numerical simulation method has been proven to be sound by the swirling experiment of a low melting point alloy in an immersion nozzle surrounded by a round stirrer.