Channel induction furnaces

Abstract

The invention relates to channel induction furnaces employed for melting metals. A channel is arranged to extend downwardly from a bath and to form a loop whereby molten metal in the bath can pass into the looped channel to form a closed electrically conducting loop. A laminated iron core passes through a coil and forms a closed magnetic circuit linked with the coil and channel. Consequently, alternating current applied to the coil induces currents to flow in the molten metal in the channel, which metal is therefore heated. The molten metal is contained in the channel within a refractory lined vessel. With application of the alternating current to the coil electromagnetic forces are produced which are directed away from the walls of a channel. Thus a squeezing action is applied to the metal which produces an increase in static pressure towards the center of the channel relative to that at the wall. This pressure fluctuates from zero to a maximum value at twice the frequency of the induced current. For some value of these forces, the minimum wall pressure will be less than the vapor pressure of the most volatile species in the molten metal. Thus a vapor filled cavity can grow on the wall facing the core and upon collapse can damage the refractory lining of the channel. Therefore, to overcome this problem the channel wall nearest the induction core is shaped to follow a contour of constant current density or to follow a contour of constant static pressure.