| 摘要 |
A high-strength steel material for oil well use, having: a chemical composition which contains, in mass%, 0.60 to 1.4% of C, 0.05 to 1.00% of Si, 12 to 25% of Mn, 0.003 to 0.06% of Al, at most 0.03% of P, at most 0.03% of S, less than 0.1% of N, 0 to less than 5.0% of Cr, 0 to less than 3.0% of Mo, 0 to less than 1.0% of Cu, 0 to less than 1.0% of Ni, 0 to 0.5% of V, 0 to 0.5% of Nb, 0 to 0.5% of Ta, 0 to 0.5% of Ti, 0 to 0.5% of Zr, 0 to less than 0.005% of Ca, 0 to less than 0.005% of Mg and 0 to 0.015% of B with the balance being Fe and impurities and which has an Nieq value (=Ni+30C+0.5Mn) of 27.5 or more; a metal structure which comprises FCC structure as the main structure and has a total volume fraction of ferrite and α'-martensite of less than 0.10%; and a yield strength of 862MPa or more. |
