Stainless steel seamless pipe for oil country tubular goods and method for manufacturing the same

A stainless steel seamless pipe for oil country tubular goods having:

• a composition that consists of, in mass %, C:
• 0.10% or less, Si:
• 0.5% or less, Mn:
• 0.05 to 0.50%, P:
• 0.030% or less, S:
• 0.005% or less, O:
• 0.0040% or less, Ni:
• 3.0 to 8.0%, Cr:
• 10.0 to 11.9%, Mo:
• 0.5 to 0.94%, Al:
• 0.1% or less, V:
• 0.005 to 0.2%, N:
• 0.10% or less, Cu:
• 0.01 to 1.0%, Co:
• 0.01 to 1.0%, and Ca:
• 0.0005 to 0.0030%, optionally one or more selected from Nb:
• 0.50% or less, W:
• 1.0% or less, Ta:
• 0.1% or less, Zr:
• 0.20% or less, REM:
• 0.010% or less, Mg:
• 0.010% or less, B:
• 0.010% or less, Sb:
• 0.20% or less, and Sn:
• 0.20% or less, and in which the balance is Fe and incidental impurities;
• a microstructure containing non-metallic inclusions of an oxide containing calcium oxide, CaO, and aluminum oxide, Al2O3, in the steel, wherein a number of the non-metallic inclusions in the steel having a composition ratio satisfying the formula (1) below and a major axis of 5 μm or more is at most 20 per 100 mm2;
• and
• a yield stress of 806 MPa or more,
• (CaO)/(Al2O3)≥4.0 (1),
• where (CaO) and (Al2O3) in formula (1) represent the content of CaO and the content of Al2O3 in the non-metallic inclusions in the steel, in mass %.