Interactive Effects between Sheet Steel, Lubricants, and Measurement Systems on Friction

This study evaluated the interactions between sheet steel, lubricant and measurement system under typical sheet forming conditions using a fixed draw bead simulator (DBS). Deep drawing quality mild steel substrates with bare (CR), electrogalvanized (EG) and hot dip galvanized (HDG) coatings were tested using a fixed DBS. Various lubricant conditions were targeted to evaluate the coefficient of friction (COF) of the substrate and lubricant combinations, with only rust preventative mill oil (dry-0 g/m² and 1 g/m²), only forming pre-lube (dry-0 g/m², 1 g/m², and >6 g/m²), and a combination of two, where mixed lubrication cases, with incremental amounts of a pre-lube applied (0.5, 1.0, 1.5 and 2.0 g/m²) over an existing base of 1 g/m² mill oil, were analyzed. The results showed some similarities as well as distinctive differences in the friction behavior between the bare material and the coatings. While friction on the bare substrate was higher than that of coated surfaces with lubrication, it was found to be significantly more tolerant to dry conditions. Stick-slip behavior was also studied as a measurement system response to intermittent friction between the testing tools.