Reasons Analysis on Fracture of a Compressor Electric Valve Stem

The fracture reasons of a compressor electric valve stem were analyzed by means of macroscopical frature analysis, chemical compositions analysis, metallographic structure analysis and hardness test. The results show that the poor toughness of the fractured valve stem material and the local existence of network and banded carbides seriously lowered the fracture resistance of the material, which was the main cause of brittle fracture of the valve stem. The fracture position existing machining gap that located in the interior thread roots of upper extreme of the fracture valve stem caused local stress concentration and led the valve stem to crack from the gap.