FORMABILITY EFORMABILITY EVALUATION OF GALVANNEALED (GA), HOT-DIP PURE ZN GALVANIZED (GI), ELECTROGALVANIZED (EG) AND ELECTROGALVANIZED PREPHOSPHATED (EGP) INTERSTITIAL FREE STEELALUATION

摘要

The formability of galvannealed (GA), hot-dip pure Zn galvanized (GI), electrogalvanized (EG), and electrogalvanized prephosphated (EGP) interstitial free (IF) steel sheets was studied. The phases in the Fe-Zn system were characterized using electronic and optic microscopy as well as X-ray diffraction. Behavior of the Zn coating when subjected to stretching, bending and drawing was also assessed. Comparison between the performance of large-scale industrial production of GA, GI, EG and EGP coated steels was made possible. The GI steels presented the best results, due to the predominantly basal crystallographic texture, lower friction coefficient with commercial oils and better press-forming response in the pressure range of 135-l80kgf/cm2. It was also observed that the phosphate present in the EGP steels protected the structure of the EG coating, reducing the friction coefficient. Lastly, differences between the coatings, regarding stretching, bending and drawing, were confirmed.