| 摘要 |
PURPOSE:To prevent a plug from being pulled in and to reduce a fixing force by using outer and inner pipes having different usable characteristics respectively and cold drawing the pipes between a fixed-type stepped plug having two or more steps, and a die. CONSTITUTION:An expanding part 7 is provided to the tail part of a plug 3 having a plug head 5, and the small diametral part of a die 4 is disposed between the plug head 5 and the expanding part of plug tail-part. In said constitution; two kinds of outer and inner pipes 1, 2 having respectively different usable characteristics are overlapped with each other, and are pulled into the die 4 after inserting the stepped plug 3 into the pipes 1, 2, to draw the pipes 1, 2 in the arrow A direction. At that time, the pipes 1, 2 are simultaneously drawn and expanded at the exit of the die 4 by the plug head 5 to form a clad pipe by press-welding the outer pipe 1' and the inner pipe 2' together by the residual stress. In this way, the plug 3 is prevented from being pulled-in in the arrow A direction, and at the same time, a fixing force P2 required for fixing a fixing rod 6 of the plug 3 is reduced. |
