ラインパイプ用高強度溶接鋼管向け高張力熱延鋼板およびその製造方法,申请号JP20100162036-传众专利搜索

ラインパイプ用高強度溶接鋼管向け高張力熱延鋼板およびその製造方法

申请公布号：JP5742123(B2)

申请号：JP20100162036

申请日期：2010.07.16

申请公布日期：2015.07.01

分类号：C22C38/00;C21D9/46;C22C38/38;C22C38/58

主分类号：C22C38/00

摘要：PROBLEM TO BE SOLVED: To provide a hot-rolled high tensile steel sheet having both of high strength being a tensile strength TS of 520 Mpa or higher and high toughness, and to provide a method of producing the same. SOLUTION: The hot-rolled steel sheet has: a composition containing, by mass%, 0.04-0.08% C,≤0.4% Si, 1.0-1.8% Mn,≤0.1% Al, 0.02-0.08% Nb, 0.3-0.8% Cr; and a structure of mulitiple layers in a thickness direction in which a surface layer composed of a bainitic single phase and an inner layer composed of a bainitic phase as a main phase, a second phase in which a martensitic phase having an average grain diameter of≤3μm is dispersed in an amount of 1-4% in a volume ratio, and as a third phase, a ferrite phase in an amount of 10-30% in a volume ratio. The hot-rolled steel sheet may further contain one or two or more elements among Cu, Ni, Mo, V, Ti and B in a total of≤1.0%. in addition to the above composition. The hot-rolled steel may further contain Ca and REM. When a pipe is made by using the hot-rolled steel sheet having such composition and structure, a high strength welded steel pipe having a low yield ratio of≤85% and high toughness after being made into the pipe, is obtained. COPYRIGHT: (C)2012,JPO&INPIT