Multi-Stage Cold Deep Drawing of Long Pure Titanium Cups Using Coloured Sheets for Prevention of Seizure

Long pure titanium cups were formed by multi-stage cold deep drawing using commercial coloured titanium sheets for preventing seizing. The titanium sheets have sufficient ductility and high r-value for the deep drawing, whereas the seizure tends to occur during the deep drawing due to high reactivity with die materials. The coloured pure titanium sheets were treated by electrochemical coating so as to get oxide surface layer effective for preventing the seizing. By the use of commercial coloured sheets, the investment of coating machines can be avoided in sheet metal forming makers and the quality of the oxide layer can be controlled. The effects of the thickness of the oxide layer, die materials and lubricants on the occurrence of seizure in multi-stage deep drawing were examined. It was found that the coloured pure titanium sheets have sufficient ability in preventing the seizure in multi-stage deep drawing processes.