Material Design for Grade X65 UOE Sour Linepipe Steels with SSC-resistant Property

摘要

From actual pipe investigations of Grade X65 UOE sour linepipe steels, the inner surface hardness of pipes increased by increasing the volume fraction of the lath bainite (LB) microstructure instead of the granular bainite (GB) microstructure. Four-point bend tests on sulfide stress cracking (SSC) revealed that SSC occurred when the inner surface hardness of a pipe increased by increasing the volume fraction of the LB microstructure over a 1 bar H2S partial pressure condition. Lowering the surface hardness less than 250 HVO.1kgf at 0.25 mm from the surface by suppressing the LB microstructure led to a good SSC-resistant property over the 1 bar H2S partial pressure condition.