某CrWMn钢冲孔模具在磨床磨光后于距边缘较近的圆孔处发生开裂，通过低倍组织检验、显微组织检验、化学成分分析及对开裂模具相关热处理工艺过程分析等方法对模具开裂的原因进行了分析，并进行了验证性试验。结果表明：该模具开裂是由于热处理工艺不当引起的;模具淬火时未预冷，淬火后在未冷透的情况下即用凉水清洗，再加上回火不充分，使材料内应力和组织应力较大，在这两种应力作用下，导致模具在距离边缘较近的圆孔处发生开裂。

A CrWMn steel piercing mould cracked around the round hole near the edge after it was polished on a grinding machine. Besides the analysis of heat treatment process of the cracked mould,the cracking reason was also analyzed by using the high and low multiple metallographic structure observation and chemical compositions analysis on the heat treatment test sample and the raw material. Verification test was performed to prove the reason. The results show that the crack resulted from the improper heat treatment processing. The mould was not precooled before quenching. Then it was cleaned with cool water when it didn’t cool completely after quenching. In addition,the mould was not tempered fully. All these improper processing resulted in a larger internal stress and structure stress which made the mould crack.