| 摘要 |
Provided is a seamless steel pipe for a line pipe having high strength and toughness. The seamless steel pipe for a line pipe has a chemical composition by mass% of 0.02% to 0.10% of C, 0.5% or less of Si, 0.5% to 2.0% of Mn, 0.01% to 0.1% of Al, 0.03% or less of P, 0.005% or less of S, 0.005% or less of Ca, and 0.007% or less of N, and further, one or two or more selected from the group consisting of 0.008% or less of Ti, less than 0.06% of V, and 0.05% or less of Nb, and Fe and impurities as the balance, wherein the carbon equivalent (Ceq) as defined by formula (1) Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cr)/15 (1) is 0.38 or greater; the Ti, V and Nb content satisfies formula (2); Ti+V+Nb<0.06 (2) and the size of a carbonitride containing one or two or more of Ti, V, Nb, and Al is 200 nm or less. |
