The effect of inclusion type and morphology, sulfur content and Ca/S ratio on Hydrogen Induced Cracking Resistance of seamless line pipes Grades X60 and X65 was studied. The sulfur content ranges between 0.0010% and 0.0040% and the Ca/S ratio varies from 0.6 to 2.7. HIC resistance was evaluated following NACE TM0264-96, using the solution with pH 2,7. Test duration was 192 hours. Fourteen of the steels tested presented slight cracking after the test. The obtained values of CLR, CTR and CSR were notably lower than the usual acceptance limits for these parameters. The maximum values of the crack ratios were obtained in materials with Ca/S ratio lower than 1 and S content higher than 0.003 %. In the range of sulfur tested, it was found that, for seamless line pipes, a Ca/S ratio between 0.6 and 1 is adequate to guarantee HIC resistance.
Keywords: Hydrogen Induced Cracking, seamless line pipes, Ca/S ratio, S content.