采用化学成分分析、宏观和微观检验、金相组织分析和力学性能测定等方法分析了吐丝机用高强度螺栓发生断裂的原因。结果表明,由于机加工不当而在螺纹根部产生表面缺陷,并且这些表面缺陷周围在随后的热处理过程中发生全脱碳,大大降低了螺栓的疲劳强度,导致螺栓在使用过程中早期疲劳断裂。

Fracture analysis of a high-strength bolt in laying head is conducted by a variety of means. The results show that a fragile fatigue fracture happened in the bolt. Surface defects in the bottom of screw threads induce a very high degree of stress concentration due to improper mechanical processing,and full-decarbonization around the defects during the following heat treatment reduces fatigue strength of the bolt greatly,thus resulting in the early fracture of the bolt.