STEEL PLATE FOR LINEPIPE, STEEL PIPE FOR LINEPIPE, AND PRODUCTION METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a high strength steel pipe for a linepipe, in which the occurrence of HIC (Hydrogen Induced Cracking) is sufficiently suppressed without being added with a large amount of alloy element.;SOLUTION: The steel pipe for a linepipe is provided that comprises a surface layer formed on at least single side of a surface of the steel pipe and having a thickness of 10 μm to less than 2000 μm and an inner layer which is the balance other than the surface layer of the steel pipe. The surface layer is composed of steel in which total volume fraction of a bainite structure, an acicular ferrite structure and a bainitic ferrite structure in a micro structure is 90% or more. The inner layer is composed of steel which has a component composition containing, by mass%, C:0.02 to 0.08%, Si:0.01 to 1.0%, Mn:0.5 to 1.8%, P:0.01% or less, S:0.002% or less, Ti:0.005 to 0.040%, Al:0.01 to 0.07% and the balance Fe with inevitable impurities and in which volume fraction of the ferrite structure in a micro structure of the inner layer is 80% or more.;SELECTED DRAWING: None;COPYRIGHT: (C)2016,JPO&INPIT