Dry progressive stamping of copper-alloy snaps by the plasma nitrided punches

The dry progressive stamping was strongly required to make mass production of clothing parts and beverage cans. The duplex coating was one of the most reliable means to protect the dies and punches from wear and friction and to prolong their life time. In this coating, the die and punch was first surface-treated to have sufficient hardness in compatible to the hard ceramic coatings. In the present study, the low temperature plasma nitriding at 673 K was employed to harden the six kinds of punches and dies for progressive stamping of copper alloyed fucks. The micro-structure and nitrogen mapping were investigated by SEM with EDS to demonstrate that the hardening took place by nitrogen super saturation into SKD11 matrix without nitride precipitations. These nitrogen super-saturated punches and dies were fix into the progressive die set for dry stamping. No significant wear of tools as well as reduction of stamping loads even after a million shots proved that the low temperature plasma nitriding should be suitable to make hardening of dry stamping die substrates even without use of hard ceramic coatings.