Direct observation of the free surface behavior of a molten metal under the imposition of an intermittent alternating magnetic field

In continuous casting, the free surface motion of a molten metal plays an i mportant role for determining the surface quality of products. In order to clarify the free surface behavior of a molten metal under the imposition of an intermittent alternating magnetic field free surface waves of a molten gallium were visualized and recorded by use of a high-speed video camera, I t is noticed that the number of capillary waves generated in the radial dir ection increased with increase of the instrument frequency and was decrease d by inserting a copper shield between a coil and a mold. The number of the waves generated in the azimuthal direction decreased during propagating fr om the vicinity of a sidewall to the center. Asymmetric gravity waves were excited when the distribution of the magnetic field was non-uniform in the azimuthal direction or the intermittent frequency was adjusted near the res onance frequency.