AS-ROLL ELECTRIC RESISTANCE-WELDED STEEL PIPE FOR LINE PIPE, AND HOT-ROLLED STEEL SHEET

An as-rolled electric resistance welded steel pipe for a line pipe, in which a base metal portion includes, in terms of % by mass, 0.030 to 0.120% of C, 0.05 to 0.30% of Si, 0.50 to 2.00% of Mn, 0.010 to 0.035% of Al, 0.0010 to 0.0080% of N, 0.010 to 0.080% of Nb, 0.005 to 0.030% of Ti, 0.001 to 0.20% of Ni, and 0.10 to 0.20% of Mo, and the balance includes Fe and impurities, wherein the following F1 is from 0.300 to 0.350, and wherein in a metallographic microstructure of a wall thickness direction central portion of the base metal portion, a polygonal ferrite fraction is from 60 to 90%, an average crystal grain diameter is 15 µm or less, and a coarse crystal grain ratio, which is an areal ratio of crystal grains having a crystal grain diameter of 20 µm or more, is 20% or less; F1 = C + Si/24 + Mn/6 + Ni/40 + Cr/5 + Mo/4 + V/3 + Nb/3.