Failure Analysis on Fracture of 35CrMo Steel Bolts

The 10.9 grade 35CrMo steel bolts for elevators fractured after being installed for a period of time, and the fracture reasons were analyzed by direct-reading spectrometer, scanning electronic microscope, optical microscope, Vickers hardness test machine and so on. The results show that the fracture of the bolts was hydrogen induced delay fracture under the co-action of hydrogen and static tensile stress.