To provide a seamless tube which has a smooth outer surface and an inner surface on which a plurality of kinds of grooves are formed, and to provide a method and a device for manufacturing the seamless tube having the grooved inner surface by which the tube is manufactured at a low cost and high productivity and the generation of fin parts is prevented.
The diameter of the tube 1 is reduced with a die 2 and a plug 7. Then, by pressing the outer surface of the tube 1 toward a grooving plug 9 with a pair of rolls 3, grooves 12 are formed in part of the inner surface of the tube 1. The cross-sectional shape of the tube 1 is flattened in the direction in which the tube is pressed with the rolls 3 by this working. By applying sizing to the tube 1 with the die 4, the cross-sectional shape of the tube 1 is made to be approximately completely circular. By pressing the outer surface of the tube 1 toward a grooving plug 11 with a pair of rolls 5 the axes of rotation of which are arranged so as to orthogonally cross the axes of the rolls 3, grooves 13 are formed in part of the inner surface of the tube 1. The diameter of the tube 1 is then reduced with a die 6.
SAEKI CHIKARA
KOSEKI KIYONORI
IWAMOTO HIDEKI
