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通过数值模拟和实验研究,分析了施加不同励磁电流螺旋磁场时Pb-Sn合金的凝固过程。结果表明:随着励磁电流的增加,冷却速率逐渐降低,熔体内的温度梯度变小,促进晶粒等轴化;轴向分力使熔体沿轴向的环流增强,初生β相趋于弥散分布,宏观偏析基本消除。但大电流产生强烈的搅拌,增加了晶粒之间摩擦与碰撞几率,晶粒聚集程度提高,强烈的感应加热也延缓熔体的冷却速度,导致晶粒粗化。在频率为10 Hz条件下,适宜的励磁电流是100~125 A。
Through numerical simulation and experimental study, the solidification process of Pb-Sn alloy with different excitation current and helical magnetic field was analyzed. The results show that with the increase of magnetizing current, the cooling rate decreases gradually and the temperature gradient in the melt becomes smaller, which promotes the equiaxed grains. The axial component increases the axial circulation of the melt, and the β phase tends to Diffuse distribution, macrosegregation basically eliminated. However, the strong current has a strong stirring, increasing the probability of friction and collision between the grains, the degree of aggregation increases, a strong induction heating also slows the melt cooling rate, resulting in grain coarsening. The suitable excitation current is 100 ~ 125 A at a frequency of 10 Hz.