Abstract
The efficiency of hot forging processes significantly depends on the service life of the dies. As a consequence of thermal and mechanical interactions between workpiece and tool surfaces during the forming process, adhesive and abrasive die wear occurs, that is a major failure reason of hot forging tools. Due to the high forming temperatures, the annealing temperatures of the tool steels are exceeded. This leads to a decrease of the die material’s hardness that results in an increased tool wear particularly in areas of the die cavity with high relative velocities and contact pressures between tool surface and workpiece. Within the process design by means of Finite-Element analysis, a quantitative prediction of the die wear in consideration of thermal conditions is limited at present. In terms of the reachable process cycles, the design of the forging tools is generally based on the know-how of the engineer. This paper shows an enhanced FE-based approach for die wear calculation that includes relevant thermal effects on the tool material. In addition, the mentioned approach is calibrated by substantial industrial data, to obtain more realistic results. The wear behaviour of several industrial forging dies, that cover an extended range of geometries, was determined by optical measurement technology over long operating times. Based on the obtained results, the approach for die wear calculation was calibrated by statistical analysis. Exemplary, the simulation concept was implemented into a commercial FEA-package for the simulation of bulk metal forming processes by means of user subroutines, considering materialspecific wear properties for some common hot forming tool steels. The modelling approach is finally verified regarding an industrial process with complex tool geometry.