Action of Pulse-Magnetic Fields on Liquid and Crystallizing Metal

Abstract

Pulsed-magnetic fields are used for execution of a whole complex of technological processes: dividing, forming, assembling, welding and others. In all these technologies half-finished products from sheets, sections and tubes are used as billets. Action of magnetic fields on a cast metal is known in the metallurgy production, for example, casting to an electromagnetic crystallizer. In spite of a high electrical resistance of a melt and owing to low mechanical resistance of a liquid metal the use of high-intensity pulse-magnetic fields (PMF) in technologies of mechanical engineering is of interest. Even the first exploration experiment showed high efficiency of such action. At energy of 1, 2 kJ a portion of the melt under the action of the PMF has flown more than 4 m, spread in the form of a thin film on the ceiling and solidified. The paper presents three basic technological schemes of such action: with influence through a wall of a magneto-transparent crucible; by an immersion inductor; and action from the surface. Factors accompanying such action are: added sources of heat as a result of flowing of induced eddy currents through the melt; force action on the melt responsible for passage of waves of stress and metal flows. Action of these factors is controllable both in intensity and in direction. The temporal action of the pulse-magnetic field on a liquid and crystallizing metal (LCM) is to be matched with a curve of cooling the melt: either on the portion above the crystallization area or on its different portions, that is, at different relationships of solid and liquid phases.Factors of action of the pulse-magnetic field change temperature conditions of crystallization influence on the number of centers of crystallization and, as the consequence, change structure and properties of cast metal. The paper presents results of first studies on action of the pulse-magnetic field on a LCM which testify that such action is real and good. This has determined the prospects for development of new technologies in metallurgy (forming of an ingots structure, stirring of a material, rolling of cast metal and so on) and in mechanical engineering (in casting, stamping, welding and others).