Microstructure aspects of sulphide stress cracking in API micro alloyed steels

Abstract

Presented paper summarizes results of sulphide stress cracking (SSC) resistance of API micro alloyed steels. Two grades of steels - X52 and X60, according to API 5L Specification - have been tested in as-received state (after rolling) and after laboratory quenching and tempering. Obtained results have shown that SSC resistance of steels depends strongly on their microstructure (as in the case of hydrogen induced cracking – HIC). Heats containing bands of ferrite and pearlite or even bands of non-tempered bainite or martensite exhibited a poor resistance to SSC and failed at stresses well below the yield point when tested according to NACE TM 0177, Method A. Quenching and tempering had a beneficial effect on SSC steel resistance despite the fact that mechanical properties and hardness increased considerably. All the results indicate that microstructure plays an important role in the case of SSC. If this fact is not respected, a material non-resistant to SSC can be chosen.