以低熔点Sn-32%Pb-52%Bi合金作为模拟介质, 实验研究了高频交变磁场以及复合磁场(交变磁场+静磁场)作用下结晶器内液面波动及其不稳定行为. 实验发现,单独施加交变电磁场时, 液态金属表面处于波动状态, 随着交变磁场磁感应强度增加,液面会依次出现稳定凸起圆台形变形和液柱的随机摆动现象; 发生摆动时的凸起液面主要呈柱状和三棱柱状, 此时液面中心波动略强于三相点处. 随交变磁场磁感应强度增加,中心点处的波动主频率逐渐增大. 横向水平静磁场(0-1.44 T)的施加能显著抑制交变磁场作用下变形液柱的不稳定摆动行为; 增加静磁场磁感应强度, 液柱的摆动幅度减弱.静磁场可以有效抑制液面的波动, 增加静磁场强度, 熔池自由表面出现拉伸现象,在强静磁场作用下, 液面出现规则层波. 实际应用中应有一个合理的静磁场磁感应强度范围,此时液面较稳定, 液面波动振幅和主频率均较小.

In order to control stability of molten metal surface during electromagnetic continuous casting, the stabilities of melting surface under applications of an alternating magnetic field and a compound magnetic field were investigated experimentally. The melting surface behavior of the Sn–32%Pb–52%Bi alloy with low–melting point was measured by using a laser displacement sensor and visualized by using a high–speed video camera. The Fourier analysis method was introduced to reveal the fluctuation characteristics of free surface. It is experimentally found that when only alternating field is applied, the free surface keeps fluctuating. However, with increasing the alternating magnetic flux density, two statuses of the free surface, the stable camber deformation and the swinging phenomenon, can be observed orderly, and during swinging, the square–like or triangular prism–like deformations appear stochastically. The Fourier analysis indicates that the dominant fluctuation frequency at free surface center increases with increasing the alternating magnetic flux density. After simultaneously superposing a transverse static magnetic field within 0—1.44 T, the unstable swinging behavior of free surface can be remarkably controlled. Increase of static magnetic flux density can make the swinging amplitude reduce. Also the static magnetic field can effectively damp the free surface fluctuation. The stretch phenomenon was observed due to application of high static magnetic field in compound field, also a series of regular surface fluctuations appeared on free surface. There is an appropriate range of the static magnetic flux density to obtain more stable free surface, lower fluctuation amplitude and dominant fluctuation frequency.