汽车铸造铝合金缸盖失效分析

Failure Analysis of Cast Aluminum Alloy Cylinder Head for Vehicle

目的某汽车公司的铸造铝合金缸盖在使用过程中发生开裂,需寻找缸盖发生失效的原因。方法通过应用环境扫描电镜观察缸盖断口形貌、金相显微镜观察断口金相组织、纤维硬度仪检测缸盖芯部硬度、化学成分分析和低倍针孔度测试方法,对铝合金缸盖的失效原因进行全面分析。结果铝合金缸盖样品化学成分和硬度满足技术要求,金相组织未发现异常,低倍针孔度控制良好。分型线凹槽过深造成应力集中较大,是缸盖失效的主要原因。结论建议在缸盖的生产过程中需进一步控制分型线凹槽深度,以避免失效。

Objective To find the cause for cracking of cast aluminum alloy cylinder head supplied by a certain motor corporation during using. Methods The failure cause for the cylinder head was analyzed by observing appearance of fracture with SEM, observing metallographic structure of fracture with metallographic microscope, testing the core hard-ness of cylinder head with fiber hardness tester, analyzing chemical component and testing macrostructure pinhole degree, et.al. Results Chemical component and harness of sample for aluminum alloy cylinder head met the technical require-ments. There was no abnormity on metallographic structure. The macrostructure pinhole degree was controlled properly. The larger depth of parting line groove was the main cause for the failure of cylinder head. Conclusion It is suggested to further control the depth of parting line groove in production of cylinder head to avoid failure.