To provide a method of manufacturing a tube having a spirally grooved inside surface which is manufactured with a device having simple structure and has high productivity and its device.
This device is a port hole die in which a die mandrel and a die cap for extruding a hollow material of a metallic material are combined and has a plug which is freely rotatable taking the direction of extrusion as the center of the rotation at the front end in the extruding direction of the male head of the die mandrel. The plug is made into an approximately truncated conical shape which is expanded in the extruding direction in the outline, has a spiral projected line on the outer peripheral surface and is provided with a ring-like flow guide for generating twist in the metal flow just under a port hole in the die chamber.
TAKATSUJI NORIO
ARISAWA TOMOKATSU
UNIV TOYAMA
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