Investigation on Adhesion-Promoting Process Parameters in Steel Bulk Metal Forming

Abstract

Surface layers of forging dies are subject to thermal, mechanical and tribological influences during forging. These loads occur combined and result in a variety of tool damages, which shorten tool life. The predominant cause for tool failure is wear. While abrasive wear and crack formation directly cause tool failure, adhesive wear can be equally disruptive as it results in a geometrical deviation of the tool and the formed work piece. However, adhesive wear can also be beneficial in acting as a regenerating, protective layer to the surface of forging dies. This paper deals with the influence of process parameters and billet material on the formation of adhesive wear on forging dies. As adhesive wear is facilitated at elevated temperatures, high thermally loaded dies with a mandrel geometry are investigated in forging tests. During forging, thermal, mechanical and tribological loads on the tools are varied by changing cooling parameters, steel billet material and lubrication strategies. The study presents adhesion-promoting process parameters and tool areas of increased adhesive wear. The results show, that the formation of adhesive wear occurs predominantly at high tool temperatures and in areas with increased material flow, while lubrication and the billet material show little to no impact.