Steel pipe for fuel injection pipe, and fuel injection pipe using same

A steel pipe for a fuel injection pipe, wherein:

• a chemical composition of the steel pipe consists of, by mass %:
• C:
• 0.17 to 0.27%,
• Si:
• 0.05 to 0.40%,
• Mn:
• 0.30 to 2.00%,
• P:
• 0.020% or less,
• S:
• 0.0100% or less,
• O:
• 0.0040% or less,
• Ca:
• 0.0010% or less,
• Al:
• 0.005 to 0.060%,
• N:
• 0.0020 to 0.0080%,
• Ti:
• 0.005 to 0.015%,
• Nb:
• 0.015 to 0.045%,
• Cr:
• 0 to 1.00%,
• Mo:
• 0 to 1.00%,
• Cu:
• 0 to 0.50%,
• Ni:
• 0 to 0.50%,
• V:
• 0 to 0.15%, and
• the balance:
• Fe and impurities,
• a metal micro-structure at a center portion of a wall thickness of the steel pipe includes tempered martensite, or tempered martensite and tempered bainite, and a total area fraction of tempered martensite and tempered bainite is 95% or more;
• a hardness at a center portion of the wall thickness of the steel pipe is within a range of 360 to 460 HV1;
• a lattice spacing of a (211) diffraction plane measured by CoKα characteristic X-ray diffraction is 1.1716 Å or less, and a half-value width of the (211) diffraction plane is 1.200° or less;
• and
• a number density of cementite having a diameter of 50 nm or more is 20/μm2 or less,
• wherein the steel pipe is subjected to tempering at a tempering temperature within a range of 250 to 420° C.