采用宏观和微观分析、化学成分分析、力学性能测试、金相检验和断口分析等方法对失效气缸盖进行了分析。结果表明,该失效件为疲劳开裂。材料组织不均匀、严重的组织疏松、热处理过程中出现的过烧现象使材料疲劳强度大幅度降低,导致其疲劳失效。

The cracked cylinder head was studied by macro and micro-analysis,chemical compositions,mechanical properties,metallographic analysis and fracture analysis,which showed that the fracture mode was fatigue cracking. Because of the non-uniformity microstructure,severity microstructure porosity,and the overfiring phenomenon at the heat treatment,the fatigue strength was greatly decreased,which led to the failure.