Effect of coupling between melt shape and temperature field on electromagnetic shaping

摘要

Based on the analyses of electromagnetic pressure on melt and heat induced in melt, the ratio of heat to pres- sure Qo/Pm was defined. It was given that the relationship between Qo/Pm and thickness a, electromagnetic parameter μγ of melt and electric current frequency f under electromagnetic confinement and shaping process. If the value of Qo/ Pm is big, any adjustment on melt shape will easily cause a variation of temperature in melt. In this situation, there ap- pears a more sensitive interaction between shape and temperature field and a more narrow adjustment range for this pro- cess. Experiments on some thin plate samples with a cross-section of 6 mm x l8 mm have been done in two kinds of induc- tion coils respectively. The results show that as the coil with a trumpet inside wall is used and the positions of melt top and S/L interface are properly selected, the melt periphery is nearly vertical and the temperature gradient ahead of S/L in- terface is high. On this condition, a more stable and wider coupling between shape and temperature field has been continu- ously maintained and samples with smooth surface and unidirectional crystals have been successfully obtained.