| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a round steel tube, which can manufacture a round steel tube without performing manual conditioning work even when the round steel tube has a thick wall and a large diameter, can improve the quality of weld zone, and can easily and securely manufacture the round steel tube having no residual stress and sufficient toughness. SOLUTION: A steel plate 1 with a specified width having grooves 2 at its both ends in a width direction is bent by press forming at a plurality of places across the width so that straight portions 3a and 3b with a desired length remain and the portion between the straight portions is bent to an arc 3c, at both ends and intermediate specific portions across the width. The bent steel plate 3 is formed to a semi-finished round steel tube 5 by welding the groove portions of the bent steel plate 3 while the groove portions are made to butt against each other. After the whole semi-finished round steel tube is heated, faces 22 and 25 to be formed are passed for hot forming between a plurality of forming rolls 21 and 24 with a semicircular shape corresponding to the final radius. This enables the semi-finished round steel tube to be formed by a few times of press forming and welding, and the round steel tube can be manufactured easily, securely and efficiently by passing the semi-finished round steel tube between a plurality of forming rolls for hot forming. COPYRIGHT: (C)2006,JPO&NCIPI |
