对真空消失模铸造铸铁件铸型坍塌缺陷的形成机理进行了系统研究 ,结果表明 :铸型坍塌缺陷的形成是由于铁水充型时 ,其流动前沿气隙内外真空度的急剧下降 ,同时内外受力失去平衡 ,造成干砂向气隙内流动而引起的。提出了铸型坍塌缺陷的力学关系式 ,通过变速箱体的实验室和现场浇注试验 ,证明了上述坍塌缺陷形成机理和力学关系式的正确性。 The formation mechanism of the slump defects of cast-iron castings with vacuum-EPC was systematically studied. The results show that the collapse of castings is caused by the rapid decrease of the vacuum inside and outside the air gap when molten iron is filled, Lost balance, resulting in dry sand to the air gap caused by the flow. The mechanical relation of the mold collapse defects was put forward. Through the laboratory of transmission case and the pouring test in the field, the correctness of the formation mechanism and mechanical relation of the above collapse defects was proved.