Effect of cold working on the fracture characteristics of a mild steel exposed to a sour gas environment

The effect of cold working on mild steel and the relationship of fracture as influenced by a sour gas environment was investigated. The fractures were examined with respect to the mechanical property relationships and correlated with microstructure in conjunction with the effects of hydrogen embrittlement and stress corrosion cracking. It was found that hydrogen in this steel promotes crack initiation at grain boundaries and increases secondary cracking. Under the influence of the sour gas environment, the fractures of moderately coldworked materials (10% to 30%) exhibit quasi-cleavage behavior with some ductile microvoid coalescence. The fractures of heavily cold-worked materials (50% to 70%) exhibit the same features but with the addition of secondary cracking.