Two kinds of magnetic fields induced by one pair of rotating permanent magnets and their application in stirring and controlling molten metal flows

Abstract We present a method to induce rotating and travelling magnetic fields inside metallic alloys by permanent magnets. A pair of arc NbFeB permanent magnets, which constitutions and dimensions were optimally designed was rotated in high speed by means of a motor, and the subsequently electromagnetic body forces were induced in the molten metal. In different regions, two kinds of magnetic field were obtained: the rotating and the travelling magnetic fields. A two layers construction called double-magnet-driver was used to realize agitation and control of the free surface of the flow at the same time. CET experiment and solidifying front observation validate the theory analysis. A gradient travelling magnetic field was induced in the external space of the arc permanent magnets, with a distribution different from that induced by the alternative current. This system was analyzed, too. The induction of Lorentz forces by the gradient travelling magnetic field was proved by the analytical solution. Its effect was confirmed experimentally by visualization of the flow and the channel segregation modification.