Electromagnetic separation of nonmetallic inclusion from liquid metal by imposition of high frequency magnetic field

Abstract

In this study, a method is investigated for separating inclusion particles from liquid metal by the electromagnetic force generated by an alternating magnetic field. To make clear the characteristics of the inclusion separation, a model experiment has been performed by the use of a SiC-liquid aluminum system in a high frequency induction furnace. The thickness of particle-accumulated layer formed on the side wall and its area fraction of particles are measured from the micrographs of the cross section of solidified aluminum sample. It is found that the growth of the particle-accumulated layer is completed in a short time (ten and several seconds), and that the thickness of the layer becomes smaller and the particle fraction in the layer becomes larger with increasing coil current. Mechanical stirring is found to retard particle separation in the case of small coil current. The maximum thickness of the particle-accumulated layer obtained for the 3 mass% addition of particle is almost same as the skin depth. To investigate the electromagnetic separation in the present system, a complete mixing model is made, which takes into account the effect of the particle-accumulated layer on the electromagnetic force distribution. This model is based on the Lavers' theory with a simple modification of the change in apparent electric conductivity in the particle-accumulated layer. The estimated results of the change in particle concentration and the growth of particle-accumulated layer are in good agreement with the observed results.