Theoretical investigations into the use of conducting crucibles in medium-frequency metal melting

Clay-graphite and carbon-bonded silicon-carbide crucibles are used in nonferrous induction melting furnaces. Silicon-carbide crucibles especially have encountered premature failure when used at high power densities and operating frequencies. This is thought to be related to their nonuniform properties. To gain a more thorough understanding of this problem, an equivalent circuit analysis has been applied to the composite load of crucible and metal charge. An explanation of the analysis is put forward and results given including electrical characteristics, the distribution of power input between charge and crucible, and resultant meniscus height for typical industrial installations. The paper also explains the use of probes to measure the current density and magnetic field strength on the surface of these crucibles. The results are used to estimate electrical resistivity and power densities at different axial points of the crucible.