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 m 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.

A roll press apparatus for manufacturing an electrode plate, the roll press apparatus including a frame portion, a first pressure roller rotatably fixed on the frame portion to press a first surface of the electrode plate, the first pressure roller being configured to have a first expansion roller protruding at each of opposite ends of the first pressure roller, a second pressure roller rotatably fixed on the frame portion to pressurize a second surface facing the first surface of the electrode plate, the second pressure roller being configured to have a second expansion roller protruding at each of opposite ends of the second pressure roller, and a driver configured to provide a driving force to the first pressure roller and the second pressure roller.

A roll press apparatus for manufacturing an electrode plate, the roll press apparatus including a frame portion, a first pressure roller rotatably fixed on the frame portion to press a first surface of the electrode plate, the first pressure roller being configured to have a first expansion roller protruding at each of opposite ends of the first pressure roller, a second pressure roller rotatably fixed on the frame portion to pressurize a second surface facing the first surface of the electrode plate, the second pressure roller being configured to have a second expansion roller protruding at each of opposite ends of the second pressure roller, and a driver configured to provide a driving force to the first pressure roller and the second pressure roller.