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

A method for manufacturing a high-strength seamless stainless steel pipe for oil country tubular goods, the method comprising:

• heating a steel material in a heating furnace in an atmosphere having an oxygen concentration of 2% or more and 5% or less in terms of volume fraction at a temperature of 1250° C. or higher and 1300° C. or lower, wherein the steel material contains Cr and Ni and satisfies relational expression (1)
• Cr/Ni≤5.3 (1),
• where Cr and Ni respectively denote the contents (mass %) of the corresponding chemical elements
• forming the steel material into a seamless steel pipe,
• performing a quenching treatment and a tempering treatment on the seamless steel pipe,
• wherein:
• the seamless steel pipe has a microstructure including mainly a tempered martensite phase,
• a surface layer microstructure of the seamless steel pipe includes a white phase after having been subjected to etching with a Vilella etching solution, the white phase:
• (i) having a thickness in a wall thickness direction from an outer surface of the pipe of 10 μm or more and 100 μm or less, and (ii) being dispersed in the outer surface of the pipe in an amount of 50% or more in terms of area fraction.