某汽油发动机频繁出现缸套开裂的现象，通过宏观观察、金相检验、化学成分分析和硬度测试等方法，对缸套的开裂原因进行了分析。结果表明：发动机缸套在使用过程中发生了过载开裂，原因是在缸套离心铸造过程中，铸件壁厚和冷却速率不均匀，引起各部位收缩量不均衡、相互阻碍收缩，产生较大的残余应力；同时，毛坯件机械加工过程中，表层金属由于塑性变形产生了机械应力和热应力，最终在工作载荷的作用下发生过载导致缸套开裂。

The cylinder liner of a gasoline engine cracked frequently. The causes of cracking on cylinder liner were analyzed by means of macro observation, metallographic examination, chemical composition analysis and hardness test. The results show that the engine cylinder liner cracked under overload during use.The reason was that in the centrifugal casting process of cylinder liner, the wall thickness and cooling rate were not uniform, resulting in the uneven shrinkage of each part and mutually hindered, which resulted in large residual stress. At the same time, in the machining process of blank parts, the surface metal produced mechanical stress and thermal stress due to plastic deformation, finally under the action of working load, the cylinder liner cracked and failed due to overload.