Thick-walled large-diameter electric resistance pipe with excellent fatigue strength and its manufacturing method

摘要

To provide an electroseamed steel pipe having thick wall of 11.9 mm or more and pipe outer diameter of 219.1 mm or more and excellent in fatigue strength.SOLUTION: There is provided an electroseamed steel pipe having static yield strength of 245 MPa or more, static tensile strength of 415 MPa or more, and repeated yield strength calculated from a repeated stress strain curve obtained by conducting repeated stress load of stress ratio:0.1 of 245 MPa or more, by using a hot rolled steel band containing, by mass%, C:0.001 to 0.50%, Si:0.001 to 2.0%, Mn:0.001 to 3.0%, P:0.05% or less, S:0.05% or less, Al:0.010 to 0.060%, and the balance Fe with inevitable impurities, having a structure with a mixed phase consisting of a ferrite phase and pearlite as a main phase, and a second phase of 30 area% or less (including 0%) of the main phase as a raw material, conducting cold processing to make a cylindrical open tube, butting wide direction terminals each other, pressing, electroseaming weldment, low temperature tempering at 150 to 350°C.SELECTED DRAWING: None