Strategic surface topographies for enhanced lubrication in sheet forming of stainless steel

Strategic stainless steel surfaces have been developed for which the tribological properties are significantly improved for sheet-metal forming compared with the as-received surfaces. The improvements have been achieved by modification of the surface to promote Micro-Plasto Hydrodynamic Lubrication (MPHL) by increasing the ratio of closed lubricant pockets and modifying the pocket geometry. These factors influence the retention and subsequent escape of lubricant during forming thus enhancing lubricant permeability to the contact between flattened workpiece asperities and contacting tool. The technique, which has been developed, is based on an electrochemical treatment changing the topography of the stainless steel surface. Comparative testing of the new surface topographies in ironing and deep drawing of stainless steel sheet shows significant improvements and possibilities of replacing chlorinated paraffin oils with environmentally friendly plain mineral oil.