Patent ID: 8974612
Filing Date: 2015-03-10
Classification: C21D,C22C

Abstract:
1. A high-strength low-alloy steel having high-pressure hydrogen environment embrittlement resistance characteristics, which has a composition comprising C: 0.10 to 0.20% by mass, Si: 0.10 to 0.40% by mass, Mn: 0.50 to 0.84% by mass, Ni: 1.02 to 1.75% by mass, Cr: 0.20 to 0.80% by mass, Cu: 0.20 to 0.40% by mass, Mo: 0.10 to 1.00% by mass, V: 0.01 to 0.10% by mass, B: 0.0005 to 0.005% by mass and N: 0.0069 to 0.01% by mass, and further comprising one or two of Nb: 0.01 to 0.10% by mass and Ti: 0.005 to 0.050% by mass, with the balance consisting of Fe and unavoidable impurities, wherein the steel is heat treated so that it has a tensile strength in air after heat treatment of from 900 MPa to 950 MPa, wherein a crystal grain size number after heat treatment, which is measured by a comparison method based on a ferrite crystal grain size test method for steels specified in JIS G 0552, has a grain size of 8.4 to 10.4.