| 摘要 |
PURPOSE:To prevent edge buckling by bending the central part of a plate into the reverse curvature to that of a product and bending both end parts to the same side as that of the product, before reverse-bending the reversely bent part and forming, at the same time, a joining part of the reversely bent part and both-ends bent parts. CONSTITUTION:At the initial forming stage of an electric welded pipe manufacturing process where a band-shaped plate is continuously roll-formed to weld the formed end-faces to each other; the central part of plate is bent so as to provide a reverse curvature to that of a final product, and both end parts are bent to the same side as that of the product, before reverse-bending the reversely bent part of sheet central part, and at the same time, a joining part of the central reversely-bent part and both ends bent-parts, is formed. In this way, the strain in the lingitudinal direction of edge part is reduced, and the edge buckling of plate is prevented within a small range of a wall-thickness/outer diam. |
