Method for reducing temperature fluctuations in molten masses

摘要

The method for contact less stirring of semiconductor- and metallic melts (2) in heated containers, comprises reducing temperature variations turbulently present in the melt through flow drive effect of a rotating magnetic field significantly around the factor 3 in comparison with the case of without magnetic field. The Taylor number of the rotating magnetic field, which is larger than the threshold value, is selected in the case of drive stimulating turbulent swirl in crucible (1). A dimension less classification number is the drive flow. The method for contact less stirring of semiconductor- and metallic melts (2) in heated containers, comprises reducing temperature variations turbulently present in the melt through flow drive effect of a rotating magnetic field significantly around the factor 3 in comparison with the case of without magnetic field. The Taylor number (Ta =sigma omega B 2>h 4>/2rho v 2>) of the rotating magnetic field, which is larger than the threshold value (Ta c=Gr 0> .> 7> 5>) is selected in the case of drive stimulating turbulent swirl in crucible (1), where Gr=alpha gdelta Th 4>/v 2>. A dimension less classification number is the drive flow that is determined with alpha , rho , , sigma as volume expansion coefficient, specific gravity, kinematical viscosity and electric conductivity of the melt, g as acceleration due to gravity, delta as typical temperature difference over the melt, h as half height of the melt and/or omega and B as frequency and amplitude of the rotating magnetic field. The frequency of the rotating magnetic field is selected so that the dimension less shielding parameter S=mu sigma omega R 2>not exceeds the value S=30, and lies in the range of 5 greater than S greater than 10, where mu represents the magnetic permeability of the melt. The temperature fluctuations in the melt are reduced through increasing the Taylor-number of the rotating magnetic field over the threshold value. The reduction of the temperature fluctuations is carried out through the use of rotating magnetic field to a greater initial weight and/or greater filling height of the initial melt in the crystallization process. The amplitude of the rotating magnetic field is adapted in the progress of the crystal breeding process of the continuously decreasing melt height.