PURPOSE: To manufacture a seamless tube composed of (α+β)-type Ti alloy having superior strength and ductility at a low cost by carrying out final rolling, subsequent heating, and aging treatment after cooling under respectively specified temp. conditions at the time of manufacturing a seamless tube from an (α+β)-type Ti alloy by a skew rolling method.

CONSTITUTION: When an (α+β)-type Ti alloy is used as a stock and worked into a tube stock by a hot tube making method, such as skew rolling method, the outlet temp. of a rolling mill at the time of carrying out rolling by means of a final mill on a skew rolling line is regulated to a temp. between 200°C and β-transus (a temp. at which α+β transforms into β-single phase) + 50°C. The tube stock further rolled after the above rolling is heated to a temp. between β-transus-200°C and β-transus, air-cooled or water-cooled, and then subjected to aging treatment at 450W750°C for 2W24hr. By this method, the (α+β)-type Ti-alloy seamless tube can be manufactured with superior productivity, in high product yield, and at a low cost as compared with the one obtained by an extrusion forming method.