| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for molding a joint portion of an electroseamed steel pipe in which an increase in plate thickness in the vicinity of a welding portion is reduced, and an apparatus for manufacturing the electroseamed steel pipe.SOLUTION: In a method for molding a joint portion of an electroseamed steel pipe, a certain region (L) in a width direction from both edges of a steel band prior to bending processing is formed into (0.10 or more and less than 5.0)×a plate thickness (t) mm, and in a cross-sectional view, the edges are formed to have a minimum thickness, and an angle (&thetas;) to a horizontal plane of a taper is formed into 1.0° or more and less than 4.0°, and processing depth (H) at both edge surfaces is formed into (0.010 or more and less than 0.10)×a plate thickness (t) (mm). An apparatus for manufacturing the electroseamed steel pipe comprises: an open tube molding machine for the steel band; an electro-resistance-welding device for performing electro-resistance-welding of both edges of an open tube; and a pair of right and left upper/lower rolls arranged at an upstream side of the open tube molding machine, for pressing both edges of the steel band in a tapered shape. Alternatively, in place of the upper/lower rolls, a pair of right and left upper/lower rolls constituting an edge molding device for performing bending molding of the edges, of the open tube molding machine, press both edges in a tapered shape. |
