某HMn58-2铜制冷却器在库房存放4 a后开裂,采用光学显微镜、力学性能试验机和布氏硬度计对开裂冷却器进行了检验和分析。结果表明: 由于焊接工艺或者焊接操作不当造成的热影响区晶粒粗大和α-Cu相自β相晶界大量析出形成魏氏组织形态, 降低了材料的韧性、塑性和强度; 此外, 冷却器铜板冷卷后没有及时进行退火处理, 使得材料内部存在较大的内应力; 两方面共同作用导致冷却器在存放过程中于焊缝处萌生裂纹并不断扩展最终造成开裂失效。

A HMn58-2 copper cooler cracked after being stored in the ware house for four years. The cracking failure cooler was investigated by optical microscope, mechanical testing machine and brinell hardness tester. The results show that coarse grain of heat-affected zone, produced by improper welding procedure or improper welding operation and formation of Widmanstaten microstructure by precipitated of α-Cu phase from grain boundary of β phase decreased the ductility, plasticity and strength of material of the cooler. In addition, the stress exited in copper plate was large because it was not anneal in time after cold coiling. So cracks initiated at the welding bead and extended continuously during the storing process and eventually led to cracking of the copper cooler.