镁合金负压消失模铸造充型过程的研究

Study on Mold Filling in Magnesium Alloy EPC Process with Vacuum

镁合金负压消失模铸造充型过程的直接观察实验的结果表明 ,不抽真空时 ,金属前沿呈微凸形平缓地向前推进 ;抽真空时 ,因在模样分解产物的排除方向上存在一正的压力梯度 ,金属液优先沿模样壁充填型腔使流动形态呈不规则的凹形形态。提高真空度 ,不规则的流动形态的凹度更大且充型时间明显缩短。浇注方式对流动形态和充型时间的影响不大 ,与顶注和侧注相比 ,底注时充型过程最为平稳 ,且其充型时间最长。根据试验结果 。

The results of direct observed experiments of mold filling by magnesium expendable pattern casting (EPC) process indicate:Without vacuum, the metal fills slowly with a smoothly, slightly convex metal front profile; with vacuum, the metal will advance preferentially against the pattern wall because there is a positive pressure gradient in the removal direction of pattern decomposed products, leading to a pronounced irregular concave metal front profile. With increasing vacuum, the metal front becomes more irregular and concave, while the mold filling time is shortened greatly. The effect of the type of gating system on the metal front profile and mold filling time is not significant,compared with top gating and side gating, mold filling with the bottom gating is slightly more stable and its mold filling time is longest. Based on the experimental results, a model of mold filling of EPC process with vacuum for magnesium alloy has been set up.