电磁悬浮熔炼试样的最低温度计算分析

Calculation and Analysis of Minimum Temperature in Electromagnetic Levitation Melting

摘要:

根据Clemente R A计算电磁悬浮熔炼最低温度的办法，导出存考虑辐射散热和保护性气体自然对流散热联合作用情况下，球形试样电磁恳浮熔炼最低温度的计算模型。利用该模犁计算了不考虑气体散热、氩气自然对流散热、氦气自然对流散热3种情况下电磁恳浮熔炼球形试样的最低温度范围。通过对比，发现对于冷却能力筹的氩气，温度计算时可以不考虑气体散热；而对于冷却能力较大的氦气，对于高密度、高电阻率、低辐射率试样只考虑辐射散热计算球形试样最低电磁悬浮熔炼温度可行；而对于低密度、低电阻率、高辐射率试样，则必须考虑氦气散热与辐射散热联合作用计算球形试样最低电磁悬浮熔炼温度。不存存外部强制冷却的情况下，高熔点、低电阻率、低密度、高辐射率的试样，保护性气体冷却能力较强，试样易于在重力环境下实现悬浮过冷；而低熔点、高电阻率、高密度、低辐射率的试样，保护性气体冷却能力较差，试样难以在重力环境下实现悬浮过冷。

Abstract:

Considering terrestrial gravity and natural convection of protected gas, a calculated model of minimum temperature of spherical sample under electromagnetic levitation melting is derived. The range of minimum temperature is calculated without regard to the conditions of the heat dissipation by emission in gas. For argon, which has poor cooling ability, the heat dissipation by gas can be neglected in the temperature calulation. For helium, which has strong cooling ability, when the sample has high density, high electrical resistivity and low emissivity, the heat dissipation by gas can be neglected in the temperature calculation, too. When the sample with low density, low electrical resistivity and high emissivity, the heat dissipation by gas must be considered. When sample has high melting point, low electrical resistivity, low density, high emissivity and the gas has high cooling ability, the sample is easy to obtain undercooling under electromagnetic levitation in terrestrial gravity without additional cooling. When levitation melting sample has low melting point, high electrical resistivity, high density, low emissivity and protected gas has poor cooling ability, the sample is difficult to obtain undercoling.