Development of strategic surface topographies for lubrication in sheet forming of stainless steel

Strategic stainless steel surfaces have been developed by which the tribological properties are significantly improved for sheet metal forming compared to as received surfaces. The improvements have been achieved by modification of the surface in order to promote micro-plasto hydrodynamic lubrication by increasing the ratio of closed lubricant pockets and modifying the pocket geometry. These factors influence the retention and subsequently escape of lubricant during forming thus enhancing lubricant permeability to the contact between flattened work piece 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.