Roland Ernst

Magnetohydrodynamics applied to materials processing

Abstract In the processing of liquid materials various operations are performed, e. g., alloying, homogenisation of the composition, refining or inclusion removal. As was realised early on by Charles Crussard, electromagnetic effects can be used to process electrically conducting materials without any contact. When alternating magnetic fields are used, the material is directly heated and melted thanks to the induced electric currents. The induced electromagnetic forces are capable of shaping the free surface, levitating a liquid blob and stirring the liquid bulk or its surface. The latter principle may be applied to electrically conducting liquids such as metallic alloys, but also to poorly conducting materials such as oxides, glasses or plasmas. Those effects are used in many processes such as induction furnaces for liquid metals or glasses, refining ladles, electromagnetic levitation, continuous casting of aluminium or steel. In this paper, typical effects based on the use of electromagnetic systems are reviewed, as well as the corresponding applications.