Frictional Characteristics of Galvanized Steels Evaluated with a Draw Bead Simulator

Frictional characteristics of galvanized steels during forming are important when substituting for bare, cold-rolled steels. A Draw Bead Simulator (DBS) which simulates metal flow through a production draw bead was used to measure a coefficient of friction between the draw bead and the deforming sheet metal. Seventeen commercial lubricants were evaluated on zinc and zinc-iron coated steels produced by both electrolytic and hot-dipped processes. A wide variation in coefficients of friction was noted among the different lubricants, with relative ranking of lubricant effectiveness dependent upon the type of coated steel used for the evaluation. For a given lubricant, the coefficient of friction could be related to the surface morphology or topography of the zinc coating. The study showed that combinations of coating and lubricant can be selected with DBS frictional coefficients comparable to bare steel/lubricant combinations.