| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a steel pipe for a thick-walled line pipe, which does not require special forming conditions in steel pipe formation and a heat treatment after pipe production, and in which the compressive strength is enhanced by optimizing the metal structure of a steel sheet. <P>SOLUTION: The high compressive strength steel pipe includes, by mass, C, Si, Mn, P, S, Al, 0.015-0.07% of Nb, and 0.005-0.035% of Ti, wherein C(%)-0.065Nb(%) is 0.025 to 0.060, C(%)+0.67Nb(%) is ≤0.10, and the Pcm value is ≤0.20. The steel pipe is characterized in that, when the inner surface layer part and pipe thickness center part of the steel pipe in the Vickers hardness are respectively defined as HVs and HVm, HVs-HVm is ≥30, and in the metal structure, the area fraction of bainite is ≥95%. <P>COPYRIGHT: (C)2013,JPO&INPIT |
