Testing and modelling of new tribo-systems for industrial sheet forming of stainless steels

Sheet metal forming of stainless steels is known to be tribologically demanding. To ensure satisfactory production without pick-up and galling, lubrication with environmentally hazardous chlorinated paraffin oil is normally required and in the most severe cases combined with ceramic tool coatings. The present paper presents an attempt to clarify the challenges of replacing chlorinated paraffin oils with new environmentally friendly oils in an industrial production, by investigating these oils in combination with alternative tool materials and tool coatings. A number of tribology systems have been screened in the laboratory by strip reduction testing and the best tribo-systems have been tested in a progressive production tool at the Danish company Grundfos A/S. The combination of a TiAlN coating with one of the environmentally friendly lubricants shows good performance in the simulative test as well as the production test with no sign of galling even at maximum production speed. Lowering production speed, and thereby the interface temperature, allows less efficient tribo-systems to function satisfactory, i.e. without galling. The tool/workpiece interface temperature is simulated for the strip reduction test as well as the production test in order to estimate the critical interface temperature for lubricant film breakdown. Simulation results show good agreement with experimental measurements of tool temperature close to the interface.