| 摘要 |
PURPOSE:To provide a low cost and excellent manufacture of a multi-layer tube by a method wherein, first, an intermediate tube is put over an inner tube and, secondly, an annular local heating and surrounding coolings, which proceeds and follows said heating, are given to the intermediate tube by relatively shifting themselves in the axial direction of the intermediate tube so as to tightly join the intermediate tube onto the inner tube by shrinking the diameter of the intermediate tube and finally an outer tube is fitted onto the intermediate tube. CONSTITUTION:A double layer stock tube 3 is obtained by loosely fit a highly tough intermediate tube 2, the inner diameter of which is slightly larger than the outer diameter of a ceramic inner tube 1 and which is made of, for example, low carbon steel with carbon content of about 0.25%, onto the ceramic inner tube 1. By the relative shifting of the double layer stock tube 3 to a heating device 5 and cooling devices 6 and 6 in the direction as indicated with the arrow, the portion of the tube 3, which is plastically deformed by heating device 5, is cooled with the cooling device 6 after passing through the heated portion and consequently the diameter of the intermediate tube 2 is shrunk and as a result the inner tube 1 is tightly joined to the intermediate tube 2. By continuously and relatively shifting the double layer stock tube 3 axially to the heating device 5 and the cooling devices 6 and 6, the whole portion of the intermediate tube 2 is shrunk in diameter and consequently a self-tightened double layer tube unit 3' is produced. After the intermediate tube 2 and an outer tube 7 are relatively loosely fitted to each other, the tubes 2 and 7 are tightly fitted to each other by shrink-fitting means or the like in order to obtain a triple layer tube 8. |
