| 摘要 |
PURPOSE:To manufacture inexpensively a differential thickness pipe excellent in the accuracy of dimension and curvature by cutting the edge parts after forming a tubular body and welding the joining parts together by performing edge preparations. CONSTITUTION:A metallic sheet material having prescribed dimensions and thick parts corresponding to the thick-walled parts of a pipe, is bent into a tubular shape by a press bender. Here, S2=piD2, S2 is the outer circumferential length of a thick-walled part 3, and S1=piD1, S1 is the outer circumferential length of a thin-walled part 2, (D1 and D2 are objective outer diameters of the parts 2 and 3). The material is cut along a cutting line 9 which is perpendicular to the pipe surface and is set depending on the outer circumferential length at the transition part 10 of sheet thickness or is obtained by merely connecting both parts 2 and 3. As the line 9 is bent in the longitudinal direction, it is corrected into a straight line by interposing a liner between both ends of the opening of part 3 and adjusting the opening widths of the parts 2 and 3 by a press, etc., to make the cutting of the material easy. |
