DEEP-DRAWING OF COMMERCIALLY PURE TITANIUM SHEETS

The technology of deep drawing of commercially pure Ti cold-rolled sheet for obtaining drawn cup without defects was developed. Oil hydraulic press of max. 490 kN punch force and 98kN max. blank holding force (BHF) and 300mm/min drawing speed were used. Ti sheets (TP28C) of 0.8mm sheet thickness (t) were used. The punch diameter is phi40mm, and various punch radii were used. First, blanks lubricated with machine oil were deep drawn. BHF values were calculated by Dr. Fukui's formula. The limiting drawing ratio (LDR) was about 1.8, inferior to steel sheets. Next, two 30 mum polyethylene (PE) films were used on each side of the Ti sheet and BHF values were calculated by Dr. Fukui's formula. The LDR increased to 2.5, but large and numerous wrinkles were found. When the BHF was increased to 98kN, only traces of wrinkles were found. Last, punch lubrication was eliminated by the 50mm center hole of PE films of the punch side. The BHF was also 98kN. The LDR increased to 2.6, but severe earing was formed. As for the effect of r(p) on LDR, when r(p) is smaller than (4 approximately 6)t, LDR somewhat diminished. By adequate blank shape, this earing was nearly eliminated.