Analysis on Fracture Reason of High Strength Bolts

Based on the macro and micro analysis on the delayed fracture of M20-M24 mm bolts of 10.9 level high strength fastener, it was obtained that the hydrogen embrittlement was the main cause of fracture. By theoretical analysis on mechanism of hydrogen embrittlement and its influencing factors, the conclusion was presented that the hardness was the main influencing factor for hydrogen embrittlement of high strength fasteners.