| 摘要 |
Provided is a stainless steel pipe having a strength within a specific range and low yield ratio. This stainless steel pipe has a chemical composition that contains, in mass%, 0.02% or less of C, 0.05-1.00% of Si, 0.1-1.0% of Mn, 0.030% or less of P, 0.002% or less of S, 5.5-8% of Ni, 10-14% of Cr, 2-4% of Mo, 0.01-0.10% of V, 0.05-0.3% of Ti, 0.1% or less of Nb, 0.001-0.1% of Al, 0.05% or less of N, 0.5% or less of Cu, 0-0.008% of Ca, 0-0.05% of Mg and 0-0.005% of B, with the balance made up of Fe and impurities. This stainless steel pipe has a structure that contains a martensite phase and 12-18% of a residual austenite phase in volume fraction. The martensite phase comprises prior austenite grains having crystal grain size numbers of less than 8.0 in accordance with ASTM E112. This stainless steel pipe has a yield strength of 550-700 MPa. |
