High-strength seamless stainless steel pipe for oil country tubular goods, and method for producing the same

A high-strength seamless stainless steel pipe for oil country tubular goods having a yield strength of 862 MPa or more, the high-strength seamless stainless steel pipe having a composition that comprises, in mass %, C:

• 0.05% or less, Si:
• 0.5% or less, Mn:
• 0.15 to 1.0%, P:
• 0.030% or less, S:
• 0.005% or less, Cr:
• 14.5 to 17.5%, Ni:
• 3.0 to 6.0%, Mo:
• 2.7 to 5.0%, Cu:
• 0.3 to 4.0%, W:
• 0.1 to 2.5%, V:
• 0.02 to 0.20%, Al:
• 0.10% or less, N:
• 0.15% or less, and the balance being Fe and unavoidable impurities, and in which the C, Si, Mn, Cr, Ni, Mo, Cu, and N satisfy the formula (1) below, and the Cu, Mo, W, Cr, and Ni satisfy the formula (2) below,
• the high-strength seamless stainless steel pipe having a structure comprising more than 45% martensite phase by volume as a primary phase, and 10 to 45% ferrite phase and 30% or less retained austenite phase by volume as a secondary phase,
• wherein the total amount of precipitated Cr, precipitated Mo, and precipitated W is 0.75 mass % or less,
• −5.9×(7.82+27C−0.91Si+0.21Mn−0.9Cr+Ni−1.1Mo+0.2Cu+11N)≥13.0 (1),
• where C, Si, Mn, Cr, Ni, Mo, Cu, and N represent the contents of corresponding elements (mass %), respectively,
• Cu+Mo+W+Cr+2Ni≤34.5 (2),
• where Cu, Mo, W, Cr, and Ni represent the contents of corresponding elements (mass %), respectively.