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采用化学成分分析、金相组织检测、断口形貌观察、力学性能检测、扫描电镜及能谱分析等检测研究手段,对发动机缸体在打磨过程中出现的裂纹缺陷的产生原因进行了研究。同时,采用MAGMA软件对缸体凝固过程的应力进行了模拟分析。结果表明,该裂纹为热裂纹,是在凝固冷却过程中产生的。铸件裂纹的产生是裂纹区域的组织异常、存在氮化物夹渣以及铸件凝固冷却过程中的残余应力较大等几方面因素综合作用的结果。
The causes of cracks in engine block during grinding were studied by means of chemical composition analysis, metallographic examination, fracture morphology observation, mechanical property testing, scanning electron microscopy and energy spectrum analysis. At the same time, the stress of cylinder solidification process was simulated by MAGMA software. The results show that the crack is a hot crack and is produced during the solidification cooling. The occurrence of casting cracks is the result of the combined effect of several factors such as the microstructure anomaly in the crack area, the existence of nitride slag and the large residual stress in the solidification and cooling of the casting.