PURPOSE: To prevent uneven deformation and crack at the time of manufacturing a tube which consists of a metal or an alloy of a difficultly processable material. ;CONSTITUTION: By joining a low-resistance member 12 which consists of the metal or the alloy whose deformation resistance is smaller than that of a tube stock 1 in the tip part 1a of the tube stock 1 which consists of the metal or the alloy of the difficultly processable material and further joining an inner tube 13 which consists of the metal or the alloy whose deformation resistance is smaller on the inside surfaces of the tube stock 1 and low-resistance member 12, a composite tube 11 is made. Next hot extrusion is applied to the composite tube 11 from the side of the low-resistance member 12. In this way, static friction between the low-resistance member 12 and a die is reduced and deformation resistance between them is decreased. And, kinetic friction between the tube stock 1 and a mandrel is reduced and deformation resistance between them is decreased.;COPYRIGHT: (C)1994,JPO
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