| 摘要 |
<p>Thick wall electric resistance welded steel pipe which has a low enough Y/T so that no buckling occurs due to reeling and unreeling and which is excellent in low temperature toughness, the thick wall electric resistance welded steel pipe characterized by having a wall thickness/outside diameter ratio of 4.0 to 7.0%, comprising, by mass%, C: 0.06 to 0.15%, Mn: 1.00 to 1.65%, and Nb: 0.005 to 0.030%, having a Ceq ([C]+[Mn]/6+([Cr]+[Mo]+[V])/5+([Ni]+[Cu])/15) of 0.32 to 0.43, having a metal structure of, by area rate, 50 to 92% of polygonal ferrite, having an average grain size of the polygonal ferrite of 15 µm or less, having a hardness of a seam part of the electric resistance welding of Hv160 to 240, and
having a structure of the seam part of fine grain ferrite and pearlite or bainite, where, [C], [Mn], [Cr], [Mo], [V], [Ni], and [Cu] are respectively the contents [mass%] of C, Mn, Cr, Mo, V, Ni, and Cu.</p> |
