Die Wear and Coating Galling in Stamping Advanced High Strength Steels

Abstract

Advanced high strength steels (AHSS) have been widely used in vehicle structural components due to their high strength nature with balanced formability. In a typical application, a zinc coating is often required and applied to AHSS for the purpose of corrosion protection. Due to the high strength nature of AHSS, higher forming forces and binder pressures are also required in stamping AHSS, which often results in coating galling and die wear. The degree of coating galling and die wear depends upon forming process variables such as contact pressure, forming speed, lubrication and die temperatures. In this study, the Bending Under Tension (BUT) tester was used to evaluate the effects of these process variables on coating galling and die wear. Dual phase (DP) 590 and 780 steels with galvanized (GI) and galvannealed (GA) coatings were investigated in the study. The results indicate that GI coatings tend to have better wear resistance than GA coatings. A better surface treated (Thermo-Reactive Diffusion Vanadium Carbide) die material was also identified to decrease coating galling and die wear in stamping AHSS.