Development of strategies for saving energy by temperature reduction in warm forging processes

This paper is associated to the European policy of increasing efficiency in raw material and energy usage. This policy becomes even more important in sectors consuming high amount of resources, like hot forging industry, where material costs sums up to 50% of component price and energy ones are continuously raising. The warm forging shows a clear potential of raw material reduction (near-net-shape components) and also of energy saving (forging temperature under 1000°C). However and due to the increment of the energy costs, new solutions are required by the forging sector in order to reduce the temperature below 900°C. The reported research is based on several approaches to reduce the forging temperature applied to a flanged shaft of the automotive sector as demonstration case. The developed investigations have included several aspects: raw material, process parameters, tools and dies behavior during forging process and also metallographic evaluation of the forged parts. This paper summarizes analysis of the ductility and the admissible forces of the flanged shaft material Ck45 in as-supplied state (as-rolled) and also in two additional heat treated states. Hot compression and tensile tests using a GLEEBLE 3800C Thermo mechanical simulator have been performed pursuing this target. In the same way, a coupled numerical model based on Finite Element Method (FEM) has been developed to predict the material flow, the forging loads and the stresses on the tools at lower temperature with the new heat treatments of the raw material. In order to validate the previous development, experimental trials at 850 °C and 750 °C were carried out in a mechanical press and the results were very promising.