热镀锌机组校正辊的断裂原因

Fracture Cause of Correction Roller in Hot-dip Galvanizing Line

某热镀锌生产线校正辊运行时,在其轴头过渡圆角处发生断裂,采用化学成分分析、力学性能测试、显微组织观察、微区成分分析、无损检测和应力分析等方法对其断裂原因进行分析。结果表明:校正辊的失效形式是由弯曲和扭转等复杂载荷引起的多源疲劳失效;校正辊轴头圆角过渡区外表面的凹坑及该处的应力集中促使表面多处疲劳裂纹的萌生,在较高载荷下疲劳裂纹扩展,最终导致校正辊断裂。为避免此类失效再次发生,建议采用较大半径的过渡圆角来降低过渡圆角处的应力集中程度,提高表面质量,加强运行前的无损检测。

A correction roller in a hot-dip galvanizing line fractured at the transition fillet of its shaft head during operation. The fracture cause of the correction roller was analyzed by chemical composition analysis, tensile property testing, microstructure observation, micro-area composition analysis, non destructive testing and stress analysis. The results show that the failure mode of the correction roller was multi-source fatigue failure caused by complex loads including bending load and torsion. The pits on the outer surface of the transition fillet of the correction roller shaft head and the stress concentration here promoted the initiation of multiple fatigue cracks on the surface. The fatigue cracks propagated under high loads, and finally the fracture of the correction roller occurred. In order to avoid the reoccurrence of such failure, it was recommended to use the larger radius of the transition fillet to reduce the stress concentration degree at the transition fillet, improve the surface quality and strengthen nondestructive testing before putting into operation.