47 巻 (2006) 548 号 p. 850-854
In the multistage deep drawing processes of a beta titanium alloy sheet, the formability and the improvement of surface roughness have been investigated. The beta titanium alloy sheets have sufficient ductility at room temperature, whereas a seizure tends to occur during deep drawing due to high reactivity with other materials. To prevent the seizure, the beta titanium alloy sheet was treated by oxide coating heating, because the coated sheet was not in direct contact with the die during deep drawing due to the existence of the oxide layer. The blank used was the commercial beta titanium alloy Ti-15V-3Cr-3Sn-3Al. The effects of the coating conditions and lubricants on the formability in the multistage deep drawing processes were examined. Long drawn cups with a height sixfold that of the diameter were successfully formed by oxide coating heating. To improve the surface roughness of drawn cups, deep drawing and ironing as well as the grain refining by thermomechanical treatment were also attempted. It was found that the methods of ironing and grain refining were effective for improving the surface roughness of drawn cups.