High-strength stainless steel seamless pipe for oil wells

A high-strength stainless steel seamless pipe for oil wells having a chemical composition comprising, in mass %:

• C:
• 0.002 to 0.050%,
• Si:
• 0.05 to 0.50%,
• Mn:
• 0.04 to 1.80%,
• P:
• 0.030% or less,
• S:
• 0.0020% or less,
• Cr:
• 16.0 to 20.0%,
• Ni:
• 4.0 to 7.5%,
• Mo:
• 1.5 to 3.7%,
• Al:
• 0.005 to 0.10%,
• N:
• 0.002 to 0.15%,
• Co:
• 0.2 to 1.0%,
• Nb:
• 0.005 to 0.20%, and
• O:
• 0.010% or less,
• and further comprising one or two selected from Cu:
• 3.5% or less and W:
• 3.5% or less, the balance being Fe and incidental impurities,
• the chemical composition satisfying relation (1) and relation (2):
• Cr
• +
• 0.22
• ×
• Ni
• +
• 0.38
• ×
• (
• Mo
• +
• 0.5
• ×
• W
• )
• +
• 0.89
• ×
• Cu
• +
• 0.09
• ×
• Co
• ≥
• 21.4
• (
• 1
• )
• wherein Cr, Ni, Mo, W, Cu, and Co in relation (1) indicate the contents (mass %) of the respective elements and are zero when the element is absent,
• Co
• -
• Nb
• ≥
• 0.13
• (
• 2
• )
• wherein Co and Nb in relation (2) indicate the contents (mass %) of the respective elements,
• the high-strength stainless steel seamless pipe having a yield strength of 758 MPa or more and an absorbed energy vE−10 in a Charpy impact test at a test temperature of −10° C. of 40 J or more.