| 摘要 |
PURPOSE:To manufacture a double tube of sufficient grade of fit by giving initial diameter difference by heating and expanding the outer tube or/and cooling and contracting the inner tube before or after doubling inner and outer tubes, expanding the inner tube by inserting a mandrel, and further giving thermal contraction to the outer tube or/and thermal expansion to the inner tube. CONSTITUTION:An inner tube (for example, a stainless steel tube) 3 is inserted into an outer tube 2 (for example, a carbon steel tube) and set in a cylindrical steam heater 4. A mandrel 7 connected to a specified hydraulic pulling device 5 through a connecting rod 6 is made to encroach into the end of the inner tube. At the same time, rail caps 8, 9 that penetrate the rod 6 are provided on both ends. The inner tube 3in the caps 8, 9 is filled with cooling water and the tube 3 is cooled and contracted. On the other hand, the outer tube 2 is heated and expanded by supplying steam into the heater 4, and diameter difference is formed. Next, the mandrel 7 is pulled out in the direction of the arrow by operating the device 5. At the same time, heating is stopped and the inner tube 3 is made to yield by the mandrel 7. The inner tube 3 is plastic deformed and expanded larger than initial diameter of the outer tube 2 and pressure welded to the inner face of the outer tube 2. Thus, the both tubes are joined firmely and a double tube 1 having high grade of fit is manufactured. |
