| 摘要 |
PROBLEM TO BE SOLVED: To work the whole inner peripheral surface of a pipe into a uniform circumferential surface without producing chips and causing the occurrence of the seizure and the deformation of a tool or the like by reducing the projection of a bead in the welded part of the pipe. SOLUTION: Thin parts 4 are formed in both edge parts in the width direction on the side of one surface of a metallic plate 1 by machining work or crushing work. After butting both edge parts in the width direction of the metallic plate 1 so that these thin parts 4 are faced to each other and bending the metallic plate 1 into an open pipe shape so that the thin parts become the inside, both the edge parts are welded and the bead produced in the thin parts 4 by this welding is crushed. COPYRIGHT: (C)2003,JPO
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