LAUSR

As commercially pure titanium sheets (hereinafter simply referred to as titanium sheets) are light weight and have excellent corrosion resistance, they are widely used in platetype heat exchangers, mugs and other cups, and the bodies of cameras and notebook computers.1,2) These products are made by cold press forming of annealed sheets of JIS Class 1 titanium with the best ductility among commercially pure titaniums. When titanium sheets are press formed, the active metal titanium readily adheres to press tools, resulting in the formation of surface defects on press-formed titanium sheet parts.3,4) Metal titanium has a higher coefficient of friction than other meatls.3,5–8) This is probably because its low rigidity (elastic modulus) increases the contact area with the mating surface,6) because the hexagonal close-packed (hcp) lattice constant c/a ratio is low and there are relatively many Effects of Nitrided Surface Layer and Microstructure on Press Formability in Commercially Pure Titanium Sheet Annealed in Nitrogen Gas Atmosphere