在吊装43.4 t容器过渡段的过程中，某吊装工具的卸扣发生了断裂。通过化学成分分析、断口形貌分析、金相检验、硬度测试等方法，对卸扣断裂的原因进行了分析。结果表明：卸扣断裂起源于表面的缺陷处，缺陷的存在及热处理工艺不当导致的组织分布不均匀、晶粒粗大、铁素体沿晶界析出是导致卸扣承载时断裂的主要原因。

In the process of hoisting 43.4 tons transition section of a container, the shackle of a lifting tool fractured. Through the chemical composition analysis, fracture morphology analysis, metallographic examination, hardness testing and so on, the fracture reasons of the shackle were analyzed. The results show that: the fracture of the shackle originated from the defects on the surface; in addition, the improper heat treatment process led to the inhomogeneous structure distribution, coarse grains, and ferrite precipitation along the boundary; these were the main reasons leading to the shackle fracture during the loading.