A Study on Uniformity of Pre-Applied Lubricants from Mill Application to Draw Die

One of the causes of rejections for part breakage on automotive sheet steels at stamping plants is insufficient pre-applied lubricant (prelube) on the blank. There are several key processes that occur after the prelube is applied at the steel facility that can affect the prelube amount and distribution before the blank is stamped. To understand the effects of these key processes, a controlled study was performed to examine the effects of prelube application level, coiling, coil storage, blanking, lift storage, and blankwashing on the amount and distribution of prelube. After mill application, the prelube migrates from the center to the edge resulting in reduced oil levels (“dry spots”) in the center of the coil or blank. It was found that coiling and coil storage had the greatest effect on prelube migration. Extended lift storage resulted in continued reduction in prelube level at the center of the blank, but at a decreased rate. The study concludes that the lubricant uniformity may be improved by applying the pre-lubricant later in the process flow at the blanking operation and that special precautions should be taken with inventory systems that lead to longer material storage times.