| 摘要 |
A steel material contains: by mass%, C: greater than 0.05% to 0.18%; Mn: 1% to 3%; Si: greater than 0.5% to 1.8%; Al: 0.01% to 0.5%; N: 0.001% to 0.015%; one or both of V and Ti: 0.01% to 0.3% in total; Cr: 0% to 0.25%; Mo: 0% to 0.35%; a balance: Fe and impurities; and 80% or more of bainite by area%, and 5% or more in total of one or two or more selected from a group consisting of ferrite, martensite and austenite by area%, in which an average block size of the above-described bainite is less than 2.0 µm, an average grain diameter of all of the above-described ferrite, martensite and austenite is less than 1.0 µm, an average nanohardness of the above-described bainite is 4.0 GPa to 5.0 GPa, and MX-type carbides each having a circle-equivalent diameter of 10 nm or more exist with an average grain spacing of 300 nm or less therebetween. |
