某公司生产的气门弹簧在用户安装使用几小时后即发生早期断裂。采用宏观观察、微观分析、金相检验及硬度测试等方法对气门弹簧的早期断裂原因进行了分析。结果表明：气门弹簧表面存在折叠裂纹缺陷，该缺陷是在原材料轧制过程中产生的。在交变载荷作用下，折叠裂纹尖端的延伸部分成为疲劳裂纹源并不断扩展，从而造成气门弹簧早期疲劳断裂。

The valve spring produced by a company fractured early after several hours of installation. The early fracture causes of the valve spring were analyzed by means of macroscopic observation, microscopic analysis, metallographic examination and hardness test. The results show that there was folding crack on the surface of the valve spring, which was produced in the rolling process of raw materials. Under the action of alternating load, the extension part of the folding crack tip became the source of fatigue crack and expanded continuously, resulted in the early fracture failure of the valve spring.