Fracture Analysis on Long Axle-Pin of Elevator Chain Lift

A elevator chain lift long axle-pin fractured in assembling process.In order to find out the failure causes,macro morphology,chemical composition,micro-hardness,microstructure and fracture morphology were analyzed by means of optical microscope,scanning electron microscope,photoelectric direct reading spectrometer,EDS and micro-hardness tester.The results show that the main fracture reasons were the grinding stress and quenching retained stress on the axle-pin surface.And with the cooperation of the stress and hydrogen,hydrogen ductile-brittle fracture occurred on the surface.With the prolongation of the time the crack grew,that led to the axle-pin fracture in the process of assembling.