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某公司生产的猎枪在进行空枪射击试验时,部分击针发生了断裂。笔者采用化学成分分析、金相检验、扫描电镜观察等方法对断裂形成原因进行分析。试验结果表明,击针断裂的机制为疲劳断裂,击针的化学成分和基体金相组织正常。但击针表面有脱碳层导致击针表面弱化,使得击针表面硬度和强度明显低于基体,加速了疲劳源的形成,且击针承受较大交变应力的作用,加速了疲劳源的扩展。综合分析认为:击针断裂属于表面产生脱碳层导致的早期疲劳断裂。
Shotgun produced by a company in the air gun shooting test, part of the firing pin fracture. The author uses chemical composition analysis, metallographic examination, scanning electron microscopy and other methods to analyze the causes of fracture. The experimental results show that the mechanism of breaking the needle is fatigue fracture, the chemical composition of the firing pin and the normal microstructure of the matrix. However, the decarburized layer on the surface of the firing pin causes the surface of the firing pin to be weakened, so that the hardness and strength of the firing pin surface is obviously lower than that of the substrate, which accelerates the formation of the fatigue source and the firing pin withstands greater alternating stress and accelerates the fatigue source Expand. Comprehensive analysis shows that: the needle-break belongs to the early fatigue fracture caused by decarburization on the surface.