| 摘要 |
PROBLEM TO BE SOLVED: To provide a low alloy steel for high pressure hydrogen gas having high strength and excellent in hydrogen environment embrittlement resistance.SOLUTION: There is provided a low alloy steel for high pressure hydrogen gas containing, by mass%, C:0.35 to 0.65%, Si:0.05 to 0.5%, Mn:0.05 to 3%, Al:0.005 to 0.10%, Cr:0.8 to 4.5%, Mo:0.5 to 1.5%, V:0.05 to 0.30% and Nb:0.01 to 0.1%, and the balance Fe with impurities which are P of 0.025% or less, S of 0.01% or less, O of 0.01% or less and N or 0.03% or less, and having tensile strength of 900 MPa or more, the old austenitic grain size number of 9.0 or more, V-Mo based carbide and/or V-Mo based carbonitride of total 30/μmor more, and Ceq (mass%) and board thickness t (mm) defined in the formula (1) satisfying the formula (2). Ceq=C+(Mn+Cr+Mo+V)/5≥1.00 (1), where each element symbol means content of each element (mass%). Ceq/t≥0.025 (2). |
