Improvement of Formability for Multistage Deep Drawing of Ti-15V-3Cr-3Sn-3Al Alloy Sheet

Abstract

The improvement of formability has been investigated in the multistage deep drawing of beta titanium alloy sheet. The beta titanium alloys have good cold workability in the metal forming. However, a seizure tends to occur during metal forming due to high reactivity with other metals. The occurrence of the seizure becomes remarkable in sever forming operations such as deep drawing and ironing. Especially, it is hard to prevent the occurrence of seizure in multistage deep drawing process. In this study, to improve the formability of titanium alloy sheet, the formability in multistage deep drawing process of beta titanium alloy was investigated. The blank used was the commercial beta titanium alloy Ti-15V-3Cr-3Sn-3Al. To prevent the occurrence of seizure, the blank treated by oxide coating was used. The coated sheet was not in direct contact with the tools of die and punch during deep drawing due to the existence of the oxide layer. The effects of the surface roughness and hardness on the formability in the multistage deep drawing processes were examined. The improvement of surface roughness of drawn cup was also attempted by using heat treatment. A long titanium alloy cup was successfully formed by intermediate annealing at the 3rd stage. The drawn cup by multistage deep drawing could be formed to the 6th stage. It was found that the beta titanium alloy sheet covered with oxide layer has sufficient ability in preventing the seizure in multistage deep drawing processes.