| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel material achieving both of excellent uniform ductility and local ductility while having high strength with tensile strength of 1960 MPa or more and over 2 GPa class.SOLUTION: There is provided a steel material having a chemical composition of, by mass%, C:0.35 to 0.65%, Si:0.1 to 0.5%, Mn:0.1 to 0.5%, Cr:10 to 14%, Ti:0.005 to 0.012%, Al:0.025 to 0.055%, N:0.001 to 0.005%, Nb:0 to 0.05% and the balance: Fe with impurities, a metallic structure of a dual-phase structure constituted by ausformed martensite and austenite, a short diameter of old austenitic grain of 3 μm or less and the content of austenite of 10 to 17% by area ratio. |
