The redrawability of several organic coated container steels and the characteristics of redrawn cans

Abstract

Eighteen container steels of three tempers were evaluated for their redrawability. The die combinations employed ranged from 27 pct to 42 pct for the drawing reduction and from 22 pct to 48 pct for the redrawing reduction. The results indicated that higher tensile strength and/or lower work hardening exponents improved the redrawability. Consequently, the DR (double reduced) steels had the best redrawability, CA-T4 steels were next and BA-T1 steels had the least. Thickness, surface finish, metallic coating and average strain ratio (r) showed either little or no effect on the redrawability. The LRDR (limiting redrawing ratio) generally decreased with the increasing of drawing ratio. However, the TDR (total drawing ratio) usually increased with the drawing ratio. For each steel the tallest container could be made from the die combination with the highest drawing reduction. As for the redrawn cans, the can wall showed thickening at the upper part and thinning at the lower part of the container. The change in thickness tended to increase with the TDR and to be relatively independent of r-value. As for the earing, it was observed to increase with the TDR and, to a lesser extent with the plastic strain ratio anisotropy, Δr. The normalized earing (ratio of earing to can height) was generally less than 5 pct of the can height for most of the die combinations. Finally, the normalized can height (ratio of can height to can diameter) was found to vary linearly with the TDR employed.