Failure Analysis on Fracture of High Strength Bolts for Diesel Engine

High strength bolts with material of 30CrMoSi steel used for diesel engine fractured during service, and the fracture reasons were analyzed by means of chemical composition analysis, metallographic examination, fracture analysis and hardness test. The results show that the fracture of the bolt was early fatigue fracture, and machining defects at the screw root and more inclusions in the material were main reasons for the fatigue fracture. Finally, prevention measures were put forward for the fracture reasons.