Study on the interaction between the shape and the temperature field of the melt in the electromagnetic shaping process

Based on analyses for the electromagnetic pressure on the melt and the heat induced in the melt, the ratio of heat to pressure Q(0)/P-m is defined, to give the relationship between Q(0)/P-m and the thickness a, the electromagnetic parameter (mu gamma) of the melt and the electric current frequency f under the electromagnetic confinement and shaping process. If Q(0)/P-m is large, any adjustment to the melt shape will easily cause a variation of the temperature in the melt. In this situation, there appears to be a more sensitive interaction between the shape and the temperature field and a more narrow adjustment range for the process. Experiments on thin plate samples with a cross-section of 6 mm X 18 mm are done with two kinds of induction coils. The results show that when a coil with a trumpet inside wall is used and the positions of the melt top and the S/L interface are properly selected, the melt periphery is nearly vertical and the temperature gradient ahead of the S/L interface is high. Under these conditions, a more stable and wider coupling between the shape and the temperature field is continuously maintained and samples with a smooth surface and unidirectional crystals are successfully obtained. (C) 2001 Elsevier Science Ltd. All rights reserved.