Abstract: A long steel pipe for reel-lay installation formed of electric resistance welded (ERW) steel pipes and having high buckling resistance and a method for producing the long steel pipe for reel-lay installation are provided. The long steel pipe is formed by successively butt-joining longitudinal ends of the ERW steel pipes by girth welding so that girth welds are formed. The ERW steel pipes are successively butt-joined in the pipe longitudinal direction such that the 0 o'clock cross-sectional position or the 6 o'clock cross-sectional position of one of adjacent ERW steel pipes faces an area from the 2 o'clock cross-sectional position to the 4 o'clock cross-sectional position or an area from the 8 o'clock cross-sectional position to the 10 o'clock cross-sectional position of the other of the adjacent ERW steel pipes.

Abstract: A long steel pipe for reel-lay installation formed of electric resistance welded (ERW) steel pipes and having high buckling resistance and a method for producing the long steel pipe for reel-lay installation are provided. The long steel pipe is formed by successively butt-joining longitudinal ends of the ERW steel pipes by girth welding so that girth welds are formed. The ERW steel pipes are successively butt-joined in the pipe longitudinal direction such that the 0 o'clock cross-sectional position or the 6 o'clock cross-sectional position of one of adjacent ERW steel pipes faces an area from the 2 o'clock cross-sectional position to the 4 o'clock cross-sectional position or an area from the 8 o'clock cross-sectional position to the 10 o'clock cross-sectional position of the other of the adjacent ERW steel pipes.

Abstract: A steel material has a composition of C: 0.02 to 0.2%, Si: 0.01 to 0.5%, Mn: 0.5 to 2.5%, P: 0.05% or lower, S: 0.05% or lower, Al: 0.1% or lower, and N: 0.01% or lower and, as required, one or two or more elements selected from Cu: 0.01 to 2%, Ni: 0.01 to 5%, Cr: 0.01 to 3%, Mo: 0.01 to 2%, Nb: 0.1% or lower, V: 0.1% or lower, Ti: 0.1% or lower, B: 0.01% or lower, Ca: 0.01% or lower, and REM: 0.1% or lower in terms of % by mass, and the balance Fe with inevitable impurities, in which the microstructure at the ¼ position of the plate thickness contains ferrite and a hard phase, the area fraction of the hard phase is 50 to 90%, and the average aspect ratio of the ferrite is 1.5 or more.