Influence of sulphur content and inclusion distribution on the hydrogen induced blister cracking in pressure vessel and pipeline steels

摘要

In previous works, extensive desulphurisation, including shape control and low hardness in segregation zones, were pointed out as effective ways for increasing resistance to hydrogen induced cracking (HIC) in steels exposed to wet H_2S environment. In this study, the behaviour of eight plates was evaluated by immersing samples in H_2S-saturated NACE solution. HIC susceptibility was assessed by an ultrasonic method and correlated with the elongated MnS inclusion distribution. The results allow us to remark that an extremely low sulphur level is not necessary to reach good HIC resistance, provided that no hard bands are present in the steel. Under this condition, a relationship to calculate the minimum average sulphide length which provides low HIC susceptibility was found.