某用于插秧机的拉簧，在运行过程中发生早期断裂。通过宏观观察、化学成分分析、力学性能试验、断口分析、能谱分析、金相检验及非金属夹杂物检测等方法对拉簧的断裂原因进行了分析。结果表明：拉簧的断裂性质为疲劳断裂。热处理工艺不当是拉簧发生疲劳断裂的根本原因，冷拉后直接冷卷成型的拉簧组织为纤维状组织，该组织抵抗疲劳能力太弱，导致拉簧往复循环近百次，就发生了疲劳断裂。

The tension spring of a rice transplanter fractured during operation. The fracture causes of the tension spring were analyzed by means of macro observation, chemical composition analysis, mechanical property test, fracture analysis, energy spectrum analysis, metallographic examination and non-metallic inclusion detection. The results show that the fracture property of the tension spring was fatigue fracture. Improper heat treatment process was the root cause of fatigue fracture of the tension spring. After cold drawing, the tension spring structure formed by cold rolling directly was fibrous structure. The fatigue resistance of the structure was too weak, resulted in fatigue fracture after nearly 100 reciprocating cycles of the tension spring.