| 摘要 |
PROBLEM TO BE SOLVED: To provide a heat treated steel sheet excellent in hydrogen-induced cracking resistance, and a method of producing the same.SOLUTION: There is provided the heat treated steel sheet excellent in hydrogen-induced cracking resistance which contains, by mass%, C:0.05 to 0.30%, Si:0.05 to 0.60%, Mn:0.5 to 2.0%, P:0.050% or less, S:0.050% or less, Al:0.100% or less, having a carbon equivalent Ceq of 0.16 to 0.60. The heat treated steel sheet has metallic structure in which: metallic structure in the range of 1 mm from a steel sheet surface in a sheet thickness direction is composed of one or more kind of tempered martensite and tempered bainite ; and metallic structure in the range of ±1 mm from a sheet thickness center part in sheet thickness direction has a main phase included in an amount of 80% or more by area percentage and composed of one or more kind of tempered martensite and tempered bainite, and the balance other than the main phase is composed of one or more kind of ferrite, perlite, cementite and retained austenite. The heat treated steel sheet has a hardness at a position of 1 mm from the steel sheet surface in the sheet thickness direction of 250 HV or less and hardness difference between the position at 1 mm from the steel sheet surface and the sheet thickness center part of 60 HV or less. |
