Jfe Steel Corporation

Ryo Nakazawa

Atsushi Matsumoto

Shinsuke Ide

Hiroyuki Shirosawa

Jun Yasuda

Eiichi Urahata

An electric resistance welded steel pipe, and a method for manufacturing the same are provided. An electric resistance welded steel pipe has a welded portion that includes a heat-affected zone having a steel microstructure principally including a bainitic ferrite phase and/or a bainite phase. The steel microstructure at half the wall thickness includes a bainitic ferrite phase and/or a bainite phase in a total area ratio of 90% or more. In the steel microstructure located 1 mm in the wall thickness direction, the bainitic ferrite phase and/or the bainite phase has an average grain size of 20 μm or less. The average grain size of the bainitic ferrite phase and/or the bainite phase located 1 mm in the wall thickness direction is 0.5 times or more and 2 times or less the average grain size of the bainitic ferrite phase and/or the bainite phase at half the wall thickness.

Electric resistance welded steel pipe and method for manufacturing the same

An electric resistance welded steel pipe having excellent formability and torsional fatigue resistance and a method for manufacturing the same. The electric resistance welded steel pipe includes a seam region and a base metal region, the seam region having a range of ±10 degrees in a pipe circumferential direction with respect to an electric resistance welded seam formed in a pipe longitudinal direction, the base metal region being a region other than the seam region. The electric resistance welded steel pipe has an r-value in the pipe longitudinal direction of 1.0 or greater, H (mm) and W (mm) satisfy a specified formula, and Ts(mm) and Tb(mm) satisfy a specified formula.

Growing community of inventors

Tokyo, Japan

Ryo Nakazawa