Microstructure Transformations in Tempering Steels during Continuous Cooling from Hot Forging Temperatures

Apart from reducing the processing energy, hardening and tempering of near-net shape forged components from their forging heat primarily promises shortened conventional process sequences. In this case, the continuous cooling transformation diagrams (CCT diagrams) found in the literature can only be used as a rough approximation of microstructural transformations during the heat-treatment. The reasons for this are that firstly, the deformation influences the transformation kinetics and secondly, the deformation temperatures are comparatively high. Therefore, both deformation CCT diagrams and, for reference purposes, CCT diagrams without deformation were determined for a selection of heat-treatable steels (34CrMo4, 42CrMo4, 52CrMo4, 51CrV4, 34NiMo6) at the heating temperature of 1200 degrees C and deformation levels of 0.3 and 0.6.