| abstract |
(57) 【Abstract】 PROBLEM TO BE SOLVED: It is difficult to form a fin having a sufficient depth on the inner surface of an aluminum-based metal pipe, and the processing depends on the pulling force of the metal pipe. It could not be applied to a metal material having a low breaking strength such as an aluminum-based metal. SOLUTION: A metal material 11 is supplied to a groove portion 2 of a rotating wheel 1 and fed into a material collecting chamber 4 provided inside a shoe block 3, and the metal material 11 heated to high temperature and pressure is heated to a die portion 5. Push out from. Inside the die bearing portion 9 of the die portion 5, the tip processed portion 8 of the mandrel 6 penetrating the shoe block 3 is located. The mandrel 6 is configured to be rotated by a drive source 10, and the tip processing part 8 of the mandrel 6 is further provided. A groove 7a is provided on the outer surface of the. At the same time when the metal tube 12 is pushed out, the mandrel 6 is rotated, whereby a spiral fin 13 is formed on the inner surface of the metal tube 12 by the rotating groove 7a. |