Alternating Electromagnetic Field as a Motion Control Tool under High Temperature Environment

Solute control in boundary layer under a high temperature environment is important from the industrial viewpoint, because mass transfer in boundary layer is often rate-determining step of chemical reactions and chemical composition of solidified alloy is determined by solute concentration in the vicinity of solid-liquid interface. An alternating electromagnetic force is one of candidates to control the mass transfer in the boundary layer of molten metals and alloys since it can directly excite a flow in it. The alternating electromagnetic force also has a potential to enhance the removal of inclusions in molten metal because increase in their collision efficiency is expected. This paper reviews the recent investigations on possibility of the alternating electromagnetic force as a tool of solute concentration control and inclusion removal. A model experiment using an electrolyte aqueous solution and electrodes having a shape with triangles aligning in line was carried out to clarify the effect of the alternating electromagnetic force on solute concentration distribution in the vicinity of the boundary between the electrode and the electrolyte aqueous solution. The alternating electromagnetic force imposition changed the solute concentration distribution because of the flow excitation. Then, it was applied to solidification of an alloy. Local eutectic area ratio of a Sn-10mass% alloy was dependent on the imposing period of the alternating electromagnetic force during its solidification. This suggests that the alternating electromagnetic force might control the solute distribution. Theoretical investigation on collision frequency among the inclusions using the alternating electromagnetic force suggests that this method is suitable for small inclusions collision and the collision frequency increases as frequency of the alternating electromagnetic force becomes low.