Failure Analysis on Fracture of Catch Bolts of 252 kV GIS Mechanism

Fracture failure happened to a batch of 35CrMo alloy steel zinc electroplating catch bolts used for 252 kV gas insulated switchgear (GIS) mechanism during the closing test. The fracture reasons of the catch bolts were analyzed by means of chemical composition analysis, fracture analysis, hardness test, hydrogen embrittlement assessment test, metallographic examination and so on. The results show that the fracture of the catch bolts was caused by the hydrogen embrittlement, and the hydrogen embrittlement fracture of the bolts was caused by the improper dehydrogenation process after zinc electroplating. Finally, measures to prevent the hydrogen embrittlement fracture of the bolts were proposed.