| 摘要 |
PURPOSE:To prevent the defect such as generation of edge buckling owing to edge bending and to obtain an ideal shape of a welded end in roll forming of a thin walled electric welded pipe, by forming a plate to a shape approximate to an elliptical or oval shape without bending the part of a specified length from the end thereof. CONSTITUTION:The end parts of a plate are left at zero curvature without forming till the last as shown in the figure in the stage of roll-forming a thin walled electric welded pipe of <0.10 t/D. More specifically, the ends of the plate are prevented from contacting with, for example, an upper roll as shown by 1 in the figure. However, a drawing ratio is made smaller than in the prior art to leave said end parts without bending positively in a fin pass srage, but some curvature may be provided owing to the characteristic of fin pass. The plate material having the ends of zero curvature is thereafter subjected bending approximately to a UO shape as shown in the figure (b), whereby the intended thin walled electric welded pipe is formed. |
