Effect of preheating on punch force, sheared surface and work hardening in cold punching process of commercially pure titanium sheet

In cold punching, the main problems are the large punch force and the low burnish in sheared surface; otherwise, the main problem in warm and hot punching is the decrease in material hardness. Therefore, cold punching with preheating has been developed in order to reduce the punch force and to improve the burnish height. This paper aims to investigate the effect of preheating in the cold punching on punch force and burnish height of commercially pure titanium. The testing apparatus used has been a pneumatic punch machine with temperatures of 30, 100 and 150 °C. Punch velocity used has been 35 and 70 mm/s. The results show that cold punching with preheating can reduce punch force, improve burnish height, and decrease work hardening. With a preheating of 150 °C on velocity 35 mm/s, punch force has been reduced by 17.8 compared to cold punching force. On the other hand, burnish height has improved by 41.6; this result is smaller than warm and hot punching. However, the ratio of burnish height resulted to thickness is greater. Work hardening has decreased by 27) of cold punching work hardening; this decrease is smaller than warm and hot punching. © 2019 Praise Worthy Prize S.r.l.-All rights reserved.