SEAMLESS STEEL PIPE FOR LINE PIPE AND METHOD FOR PRODUCING THE SAME

摘要

There is provided a seamless steel pipe for line pipe, wherein a chemical composition consists, by mass percent, of C: 0.03-0.10%, Si: ≦0.50%, Mn: 1.0-2.0%, P: ≦0.050%, S: ≦0.005%, Cr: 0.05-1.0%, Mo: 0.01-0.30%, Al: 0.001-0.10%, N: ≦0.01%, Ni: 0.04-2.0%, Ca: 0.0005-0.0050%, Cu: 0-2.0%, Ti: 0-0.05%, Nb: 0-0.05%, V: 0-0.10%, the balance: Fe and impurities, and satisfies the conditions of Cu+Ni: ≧0.10%, and Mo+V: ≦0.30%, wherein in a scale formed on the surface of the steel pipe, metal particles consisting mainly of Ni or Cu having an average circle-equivalent diameter of 0.1-5 μm exist, and a distance from a boundary between the base metal of the steel pipe and the scale to a region in which the metal particles do not exist is 20 μm or longer.

主权项

1. A seamless steel pipe for line pipe, wherein a chemical composition consists, by mass percent, of
C: 0.03 to 0.10%, Si: 0.50% or less, Mn: 1.0 to 2.0%, P: 0.050% or less, S: 0.005% or less, Cr: 0.05 to 1.0%, Mo: 0.01 to 0.30%, Al: 0.001 to 0.10%, N: 0.01% or less, Ni: 0.04 to 2.0%, Ca: 0.0005 to 0.0050%, Cu: 0 to 2.0%, Ti: 0 to 0.05%, Nb: 0 to 0.05%, V: 0 to 0.10%, the balance: Fe and impurities, and the chemical composition satisfies the conditions of Cu+Ni: 0.10% or more, and Mo+V: 0.30% or less, wherein in a scale formed on the surface of the steel pipe, metal particles consisting mainly of Ni or Cu having an average circle-equivalent diameter of 0.1 to 5 μm exist, and a distance from a boundary between the base metal of the steel pipe and the scale to a region in which the metal particles do not exist is 20 μm or longer.