压力条件下缩松判据的研究

Study on shrinkage porosity criterion under pressure conditions

缩松是铝合金铸件中常见的缺陷。在压力下凝固能够有效减轻铝合金铸件的缩松倾向。为此，从描述枝晶间流动的Ｄａｒｃｙ定律出发，推导出与压力（ＰＳＣ）、温度梯度（ＧＳＣ）及冷却速度（ＲＳＣ）有关的缩松判据ＧＳＣ】ＰＳＣ／ＲＳＣ〈＞ＫＣ，ＫＣ为判据临界值，应用于凝固过程数值模拟。实验结果与计算机模拟结果一致，验证了判据的正确性。该判据不仅适合于铸件在压力下凝固的情况，如低压铸造，同时也适用于普通重力铸造，如砂型铸造。

Shringkage porosity is a common defect style for aluminum alloy castings. The porosity tendency is effectively testricted when the aluminum alloy castings solidify under pressure. Therefore, a new criterion which predicts shrinkage porosity during solidification simulation under pressure conditions was derived from Darcy's law. This criterion is a function of temperature gradient ( G SC ), pressure ( P SC ) and cooling rate ( R SC ) and is expressed as G SC \7 P SC / R SC \8> K C. Qualitative verification was conducted by both experiments and solidification simulation. This criterion is not only suitable under pressure condition, such as low pressure die casting, but also suitable to gravity casting, such as sand casting.