Tribology of dry deep-drawing of various metal sheets with use of ceramics tools

Abstract

Lubricant is essential in the conventional metal forming to reduce the friction between tool and workpiece and forming energy, to increase the forming limit, to shorten the forming process, and to prolong the tool life by prevention of galling and seizure. Huge amount of wasted lubricants has become a great nuisance of environmental issues. Dry deep-drawing is attractive toward zero emission of lubricants but it has great difficulty in application to metal sheets in general. As one of the most promising methods, use of ceramic die, are highlighted because of their high tribological properties. In the present paper, practical possibility of dry deep-drawing is studied using ceramic dies. Various ceramic die materials are prepared and actually applied to deep-drawing for various sheet materials without lubrication. The limiting draw ratio (LDR) as well as the drawing load, were used as a parameter to evaluate the friction between tool and blank. Each ceramic material has its own compatibility to sheet materials. Ceramic dies can be applied to deep-drawing of mild steel and pure copper sheets with success, while they failed to be utilized for titanium sheet. Deep-drawability of ceramic dies might be dependent on the covalency of ceramics: i.e. LDR(SiC)>LDR(Si 3N 4)>LDR(Al 2O 3)>LDR(ZrO 2). In case of deep-drawing for metal-alloy sheets, pretreatment to form the adhesive tribo-coating is effective to improve the workability when using alumina and zirconia dies. The adaptive design of ceramic die to each metallic sheet material is indispensable to realize the dry forming in practice.