Cr12钢冷冲模具在电火花线切割过程中发生开裂,采用光学显微镜、扫描电镜、化学成分分析和硬度测试等方法，对模具开裂的原因进行了分析。结果表明:该Cr12模具开裂为脆性开裂，其主要原因是铬含量超标,同时锻造不充分，使得材料中的共晶碳化物多而粗大且呈严重网状聚集分布,成为应力集中源，在线切割加工过程中的加工应力和材料自身内应力的共同作用下萌生裂纹并扩展开裂。

A Cr12 steel cold work die cracked during WEDM process. Fracture reason of the die steel was analyzed by means of the microstructure examination,scanning electronic microscope fracture analysis,chemical compositions analysis and hardness test. The results show that the cracking of the Cr12 steel die was due to brittle fracture. Chromium content exceeding the limit and deficient forging made the eutectic carbides in the die material were numerous,coarse and seriously aggregated network-like distribution,so the eutectic carbides became stress concentration source and initiated cracks,and then under the combined actions of machining stress and internal stress the cracks extended and finally resulted in the cracking of the die.