Seamless steel pipe and method for producing same

A hot-rolled seamless steel pipe having a chemical composition consisting of, by mass %,

• C:
• 0.10 to 0.17%,
• Si:
• 0.05 to 1.0%,
• Mn:
• 0.05 to 1.2%,
• P:
• 0.025% or less,
• S:
• 0.005% or less,
• Cu:
• 0.20% or less,
• N:
• 0.007% or less,
• Ni:
• 0.20 to 0.50%,
• Cr:
• 0.30% or more and less than 0.50%,
• Mo:
• 0.30 to 0.50%,
• Nb:
• 0.01 to 0.05%,
• Al:
• 0.001 to 0.10%,
• B:
• 0.0005 to 0.0020%,
• Ti:
• 0.003 to 0.050%,
• V:
• 0.01 to 0.20%,
• a total of any one or more elements among Ca, Mg and REM:
• 0 to 0.025%, and the balance:
• Fe and impurities;
• wherein:
• a value of Pcm that is represented by Formula [A] below is 0.30 or less,
• a steel micro-structure comprises, in area %, tempered martensite:
• 90% or more,
• a tensile strength is 980 MPa or more,
• a Charpy impact value at −40° C. using a 2 mm V-notch test specimen is 75 J/cm2 or more,
• Pcm=C+(Si/30)+(Mn/20)+(Cu/20)+(Ni/60)+(Cr/20)+(Mo/15)+(V/10)+5B [A]
• where, each symbol of an element in Formula [A] represents a content (mass %) of a corresponding element in the steel, with a value of a symbol being zero if the corresponding element is not contained, and
• wherein the hot-rolled seamless steel pipe is produced by hot rolling the hot-rolled seamless steel pipe, cooling the hot-rolled seamless steel pipe, subjecting the hot-rolled seamless steel pipe to a quenching process, and subjecting the hot-rolled seamless steel pipe to a tempering process.