| abstract |
Provided is stainless steel for oil wells, which has excellent corrosion resistance at high temperatures and is capable of stably achieving a strength of 758 MPa or more. This stainless steel for oil wells contains, in mass%, 0.05% or less of C, less than 1.0% of Si, 0.01-1.0% of Mn, 0.05% or less of P, 0.002% or less of S, 16-18% of Cr, 1.8-3% of Mo, 1.0-3.5% of Cu, 3.0-5.5% of Ni, 0.01-1.0% of Co, 0.001-0.1% of Al, 0.05% or less of O and 0.05% or less of N, with the balance made up of Fe and impurities. This stainless steel for oil wells satisfies the following formula (1) and formula (2).nCr + 4Ni + 3Mo + 2Cu ≥ 44 (1)nCr + 3Ni + 4Mo + 2Cu/3 ≤ 46 (2)nIn this connection, the contents (mass%) of corresponding elements are assigned to respective symbols of elements in formula (1) and formula (2). |