| 摘要 |
PURPOSE:To prevent the generation of wavy edges on both edges of the material to be formed by performing a bending so that the locus surface of the straight line to connect both edges of the inside of each cross section in each bending can maintain a plane surface in case of bending the material to be formed in tubular shape. CONSTITUTION:The sectional shape of the metallic strip M is first made as F1 by the prescribed forming method in case of forming an electric welded pipe with bending in the width direction the metallic strip M of flat sectional shape. The sectional shape is formed with bending in the order of F2-F7 then. In this case the straight line to connect the both edge parts K1-K7 of the inside of each cross section of the material M to be formed is overlapped on the flower figure and the straight line is made to maintain in the plane surface or about plane face shape. The shaft center of the forming roll pair to form with bending pinching the material M to be formed from the both sides is made to be on the line of slope approx. of the locus line of the center part in the width direction of the material M to be formed. The electric welded pipe of high quality is produced thus at lower cast.
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