压铸机QT500-7模板开裂失效原因分析

Causes Analysis of Cracking Failure in QT500-7 Mould Boards for Die Casting Machine

压铸机QT500-7模板在机械加工和使用过程中发生了开裂。采用断口形貌和化学成分分析、力学性能和硬度测试、金相组织检验以及生产工艺过程追溯对其开裂原因进行了分析。结果表明,铸件拆箱过早,退火保温时间过短,以及高温铸件受南方潮湿气候的雾化正火,使铸件珠光体数量、硬度、残余应力明显大幅增加。这些是模板开裂失效的主要原因。

QT500-7 mould boards for die casting machine produced crack in machine work and using. The causes for cracking were analyzed by adopting fracture morphology and chemical composition analysis, mechanical properties and hardness testing, metallographic examination and production process tracing. The results show that, the premature unpacking of the casting boxes, short-time annealing and atomizing normalizing of the high-temperature castings in a humid climate of south China greatly increase the pearlite faction, hardness and residual stress of the castings. These are main reasons for cracking failure in the mould boards.