P 944 - Flexible production of locally reinforced support structure variants using bonded blank

P 942 - Development of intelligent materials to reduce wear in forging dies The service life of hot forging dies is limited by various types of damage resulting from the complex cyclical stresses. The tool edge zone in particular is subjected to considerable thermal, mechanical, tribological and chemical stresses during operation. Compared to other manufacturing processes, the resulting load collective leads to tool failure even after short tool life. The main cause of failure is wear of the moulding tool component. Methods for reducing wear in hot forming tools are therefore the subject of numerous research projects. Even though significant improvements in the tool life of hot forming tools have already been achieved through measures such as the generation of high surface layer hardness through nitriding and/or the application of hard coatings, there is still no satisfactory cost-benefit ratio. Previous measures to reduce wear are predominantly associated with high investment and tool costs, so that the resulting increase in tool life does not cover the costs of the wear protection measures. A simple and cost-effective measure to reduce wear on hot forging tools was investigated as part of this research project. To this end, a new type of hot-work tool steel was developed in which the additional costs are limited to the alloying elements required for this purpose. The alloy was developed on the basis of the hot-work tool steel 32CrMoV12-28 (material no. 1.2365) with varying proportions of the austenite-stabilising elements manganese, nickel and cobalt, with the aim of lowering the material-specific austenite starting temperature and specifically influencing the microstructural changes in the tool edge zone. This intelligent reaction of the material to the thermomechanical environmental conditions prevailing in the process was intended to achieve an increased new hardening effect, which is maintained over many forging cycles and thus ensures continuous wear protection. The investigations showed that lowering the austenite starting temperature by means of alloying measures can contribute to a strengthening of the new hardening if the thermomechanical stresses cause austenitisation of the tool surface layer. In areas subject to high thermomechanical stresses, exceeding the austenitising start temperature and subsequent quenching of the material lead to the formation of a new hardening zone. In contrast, tempering zones with reduced hardness form in areas of the tool where the microstructure is not transformed and rehardened due to insufficient thermomechanical stress, which promotes wear on the tool and reduces the tool life. The potential of the new hot-work tool steel can therefore only be fully utilised in coordination with the forging parameters and knowledge of the stress condition on the tool. A combination of the new hot-work tool steel with additional nitriding treatment proved to be advantageous in the investigations. This led to an increase in the wear resistance of the non-rehardened areas, so that an overall increase in the tool life could be achieved. The IGF project 445 ZN of FOSTA - Forschungsvereinigung Stahlanwendung e. V., Düsseldorf, was funded via the AiF within the framework of the programme for the promotion of joint industrial research (IGF) by the Federal Ministry for Economic Affairs and Energy on the basis of a resolution of the German Bundestag. The project was carried out by the Institute of Forming Technology and Machines, Gottfried Wilhelm Leibniz Universität Hannover and the Institute of Materials Science, Gottfried Wilhelm Leibniz Universität Hannover. Publication: 2016 Authors: B.-A. Behrens, J. Puppa, H.-J. Maier, F. Nürnberger