Of hot coil for line pipe and manufacturing method thereof

The present invention provides a method of manufacturing a hot coil for even more restricted due to the heat coil winding step of the manufacturing conditions, but also to ordinary temperature strength and the deviation is reduced, the low temperature toughness is improved line pipe. Wherein, by recrystallization between the rolling passes of the steel sheet temperature range of a predetermined residence time, as well as two-stage cooling after hot rolling, the steel structure so that the center of plate thickness, the effective crystal grain size is set to the total area ratio of 3 ~ 10μm, bainite and acicular ferrite is set to 60 to 99%, and arbitrary two portions of the total area ratio of bainite and acicular ferrite and respectively a B, the a-B so that the absolute value of from 0 to 30%.