铀矿用不锈钢泵轴断裂原因分析

目的找到不锈钢泵轴断裂原因。方法通过对断裂的泵轴进行失效分析,利用扫描电镜、金相显微镜、直读光谱仪、显微硬度计等测试方法和手段,对失效泵轴的断口形貌、组织、化学成分、显微硬度等进行分析。结果断口形貌呈明显的脆性疲劳开裂特征,且裂纹源呈现多源特征,有疲劳辉纹和二次裂纹存在。316L泵轴材质成分和组织问题不大,在近表面存在大量夹杂物,同时泵轴表面观察到点蚀和微裂纹存在。结论近表面夹杂物在酸性环境中极易引起点蚀,同时泵轴与联轴器根部结合处存在变截面,形成应力集中。当泵轴受到腐蚀、应力以及电机交变载荷作用时,形成腐蚀疲劳裂纹源,裂纹扩展造成瞬断是此次不锈钢泵轴断裂的主要原因。

Causes of Fractures of Stainless Steel Pump Shaft Used in Uranium Mine

To find out the cause of pump shaft failure, this paper analyzed the failure of the pump shaft with SEM, metallographic microscope, direct reading spectrometer, micro hardness tester and other test methods. The structure, chemical composition, and micro-hardness were analyzed. The results showed that the fracture morphology had obvious brittle fatigue cracking characteristics, and the crack source had multi-source characteristics, fatigue fringes and secondary cracks existed. The material composition and microstructure of 316L pump shaft were not significant, and there were a lot of inclusions on the near surface. At the same time, pitting and microcracks were observed on the surface of the pump shaft. Near-surface inclusions are prone to pitting corrosion in an acidic environment, and there is a variable cross-section at the junction of the pump shaft and the coupling root to form stress concentration. When the pump shaft is subject to corrosion, stress and alternating load of the motor, a source of corrosion fatigue crack is formed. The instantaneous fracture caused by crack propagation is the main cause of the fracture of the stainless steel pump shaft.