Hydrogen Induced Cracking in Pipeline Steels

This paper describes the work conducted at the British Gas Engineering Research Station (ERS) using laboratory tests of the BP and NACE type to assess the hydrogen induced cracking (HIC) resistance of pipeline steels. Various grades of linepipe and fittings steels have been studied, and the metallurgical parameters controlling HIC resistance have been established. In particular, the effects of nonmetallic inclusions, sulfur content, alloy segregation, and microstructure are described in detail. On the basis of these results, it is suggested that pipeline steels for sour gas/oil service should have a low sulfur content (<0.005%) and effective inclusion shape control by calcium or rare earth metal (REM) treatment. Reduction of the manganese content to the lowest possible level and the use of quenched and tempered steels would also be beneficial. Small additions of copper, nickel, and/or chromium may offer some protection under certain operating conditions.