研究了Ni基高温合金Ni-10Cr-15Co-6W-6Mo-4Al-2Ti真空熔炼过程中Mg挥发动力学。结果表明,真空感应熔炼过程中,当炉内Ar压力保持在100—400mmHg时,合金中Mg挥发速率受Mg在液相边界层中扩散及金属熔池/气相界面挥发反应双重控制,而非受控于气相边界层中Mg的扩散。双重控制时Mg的传质系数为10~(-5)—10~(-2)cm·s~(-2)数量级,而气相边界层中Mg的传质系数为140cm·s~(-1)左右。借助于动力学公式、回归方程及特殊的参数转换,建立了一个简单的Mg挥发数学模型,该模型计算结果与实验室及生产条件下试验数据很好地符合,因此,可通过控制熔炼参数,例如向金属熔池加Mg量,Ar压力,挥发温度及时间等来精确地控制最佳Mg含量。
The kinetics of Mg evaporation of a Ni-base superalloy, Ni-10Cr-15Co-6W-6Mo-4Al-2Ti, during VIM has been studied. It was indicated that the rate of Mg evaporation is simultaneously controlled by the diffusion of Mg through the liquid boundary layer and by the evaporation of Mg at the metal pool/atmosphere interface, rather than its diffusion through the gas boundary layer, when the furnace Ar pressure kept under 100—400 mmHg. The transfer coefficient of Mg evaporation K_(23) is 10~(-1)—10~(-2) cm. s~(-1) and K_4 is about 140cm. s~(-1). A simple mathematical model for Mg evaporation during VIM was proposed. This model provided that the predicted Mg contents are in excellent agreement with those analyzed in the experimental and industrial alloys. Thus, it is possible that the optimum Mg content may be accurately controlled by certain smelting parameters, such as, the amount of Mg added into the metal pool, the Ar pressure, the temperature and time of evaporation, etc.
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