A method for manufacturing seamless steel pipe for line pipe and

The present invention provides a pipeline having high strength and toughness seamless steel tube. Seamless steel line pipe of the present invention contains, by mass%, C: 0.02% ~ 0.10%, Si: 0.5% or less, Mn: 0.5% ~ 2.0%, Al: 0.01% ~ 0.1%, P: 0.03% or less, S : 0.005% or less, of Ca: 0.005% or less and N: 0.007% or less, from the further contains Ti: 0.008% or less, V: less than 0.06% and Nb: 0.05% or less group consisting of one or two or more selected elements, the balance being Fe and impurities, by the formula (1) defined by the carbon equivalent Ceq of 0.38 or more, the chemical composition, Ti, V and Nb contents satisfy the formula (2), comprising Ti, V, Nb size carbonitrides of Al, and one or more elements of 200nm or less. Ceq = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15? (1) Ti + V + Nb <0.06? (2).