THICK WALLED LARGE DIAMETER ELECTROSEAMED STEEL PIPE EXCELLENT IN FATIGUE STRENGTH, AND MANUFACTURING METHOD THEREFOR

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 450 MPa or more, static tensile strength of 535 MPa or more, Charpy absorption energy at a test temperature of 0°C of 27 J 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 450 MPa or more, by making 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 bainite of 80 area% or more, and ferrite or martensite of less than 20 area% (including 0%) as a cylindrical open tube by cold processing, butting wide direction terminals each other, pressing, electroseaming weldment, low temperature tempering at 150 to 350°C.SELECTED DRAWING: None