from the conferences organized by TANGER Ltd.
During forging, dies are subject to a complex load collective caused by combined thermally and mechanically induced stresses. Crack formation and deformation on tool surfaces, as a result of low fatigue resistance, lead to tool failure and high process costs. Grain refinement is regarded as a method to improve fatigue resistance due to enhanced ductile material properties. To generate a fine-grained microstructure in the die material, increased deformation can be applied in the metastable austenite phase, also known as ausforming. In this study, the thermo-mechanical treatment ausforming will be used to form the final contour of forging dies. For this purpose, an analogy study was performed in which a preform is ausformed. It is investigated to what extent a fine-grained microstructure can be achieved in the final forming stage. The hot-working steel X37CrMoV5-1 (AISI H11) was used as specimen material. The developed sample geometry represents the inner contour of a highly mechanically loaded forging die. To achieve optimal properties, process routes with different cooling strategies and two defined true plastic strains were examined in metallographic analysis and hardness measurements according to EN ISO 6507-1 (HV1). It is shown that, after complete austenitisation, the highest hardness values can be achieved by applying a water-air spray cooling with subsequent forming. This could be demonstrated without material failure in the samples even with a high true plastic strain.
Keywords: Metastable austenite, ausforming, cooling rate, true plastic strain© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.