| 摘要 |
PROBLEM TO BE SOLVED: To accurately and stably manufacture a specially shaped pipe which is excellent in bending strength and energy absorbing property. SOLUTION: A method for manufacturing the specially shaped pipe, which has an outside profile having a nearly trapezoidal shape cross section and is composed of curved rim portions, comprises a first rolling step (a) for forming a circular pipe into a shaped pipe which has a cross section composed of an upper surface 14 having a curved surface with a flat portion 13 at the central position and symmetric concave portions on both sides of the flat portion 13 and a lower surface having convexly curved surfaces which are smoothly connected to the upper surface 14 and have a constant curvature, a second rolling step (b) for forming the shaped pipe so as to be depressed toward the inside of the pipe by pressing a disk shape roll 21 against the central flat portion of the upper surface while supporting the lower surface by a lower roll 22, a third rolling step (c) for forming the shaped pipe so as to reduce the outside diameter of the U shaped pipe formed in the second rolling step by narrowing the opening portion of the U shaped pipe (Figure 2) by bringing rolls 33 into contact with the both sides of the U shape curved cross section, and a fourth rolling step (d) for forming a bottom side and both tilting sides of the trapezoidal shaped pipe by pushing the right and left side portions inward by means of right and left tapered rolls 43 and by pushing up the bottom side portion by means of a lower roll 42 while supporting the upper portion by means of an upper roll 41. COPYRIGHT: (C)2006,JPO&NCIPI
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