Fracture failure analysis of the main shaft of a large sewage treatment equipment

Abstract

In view of the main shaft fracture failure accident occurred in the service process of a sewage treatment equipment, this paper carried out the fracture macro analysis, chemical composition analysis, material mechanical properties testing, metallographic structure analysis, fracture micro morphology analysis of the failure of the main shaft. The analysis results show that there are cold cracks in the weld and toe of the main shaft of the equipment, and the cracks expand under the action of rotating and bending alternating loads. The main shaft speed of the equipment is 3r/min, the load change frequency is very small, and the corrosive medium has sufficient time to play a role in the crack tip, fatigue cracks further propagated, leading to corrosion fatigue fracture of the main shaft. So in order to prevent this kind of failure, it is suggested to improve the welding process regulations for the equipment of the main shaft and rationally select welding materials.