Effect of forming conditions on frictional characteristic in cold bulk forming process of copper alloy

Effects of working speed (v) of die and lubricant on frictional characteristics of C5191 copper alloy during cold forming process are studied. The friction on contact surface is mainly caused by slight ploughing in small deformation and tearing after adhesion in large deformation, which translates at a critical deformation (deformation threshold (DT)). DT increases with increasing v. Lubricants have little effect on DT at 0.15 and 15 mm/s, but have a significant effect at 1.5 mm/s. Lubricating effect of oil and Molykote is equivalent at low v, especially before the DT, but has notable difference at high v. However, the ploughing action and tearing area by adhesive friction at high speed are smaller than those at low speed.