| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a shape steel pipe provided with a excellent cross-sectional shape and high in symmetry of an uneven part, by suppressing the flowing of a material into a narrow gap in forming, and previously setting the optimum size of a forming roll by computation. SOLUTION: In manufacturing the shape steel pipe provided with a plurality of pairs of a recessed part and a projecting part with respect to the circumferential direction from a cylindrical raw pipe by passing through a preliminary forming stand and a finishing forming stand, a plurality of forming rolls which are disposed in the circumferential direction of the raw pipe, provided with raised parts in the total number of pieces equivalent to the number of pieces of the recessed part, and wherein parts in between the raised parts form roll roots, is formed small by the previously set amount by setting the roll dividing position on the border of one roll root of the forming roll and the raised part of adjacent forming toll, and the inter-raised part distance of the roll dividing position is made small by the previously set amount considering the inter-roll gap expanding during the forming wider than the required projecting part width to form the raw pipe by the preliminary forming stand disposed with the plurality of forming rolls in the circumferential direction of the raw pipe and the finishing stand and fix the recessed part corresponding to the recessed part to the raw pipe.
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