| 摘要 |
<p>PURPOSE:To adhere an outer tube tightly to an inner tube and to improve the adhesion of the outer tube to the inner tube by inserting the inner tube into the outer tube large in diameter, then, drawing this outer tube. CONSTITUTION:When a band steel is conveyed, it is formed by a group 1 of plural lateral rolls continuously into a steel tube 2 with circular section. When the band steel leaves the final lateral roll 1A, it is formed to a steel tube G that its upper part shows an open section. The inner tube 4 smaller in diameter than the steel tube 2 is conveyed continuously and this inner tube is introduced from the open part 12 on the upper part of the steel tube into the steel tube. Then, the steel tube 2 is formed with strung pressure, by longitudinal rolls 5 to close the opening 12 of the steel tube. Consequently, the steel tube is closed with the seam line 20 on the upper side and the inner tube is inserted into the inner part to make a double tube. Then, it is seduced by lateral axis rolls, the diameter is reduced and the inner wall of the steel tube and the outer wall of the inner tube are fixed physically to each other. At the following welding stage, the seam of the steel tube is induction-heated by an induction heating device to weld the seam.</p> |
