13th International Conference on Fracture June 16–21, 2013, Beijing, China -3- Figure 2. Micrograph of the flange shaft, etched Figure 3. Vickers hardness of the different phases In order to optimize the local phase distribution and its properties in the flange shaft several pre-heating strategies were developed. Beside the standard flange shaft having room temperature at the start of the forming process four pre-heating temperatures were used for the flange. Therefore the flanges were heated up to 300, 400, 500 or 600°C in a convection oven. Then the local induction heating above the austenitization temperature was carried out before forming. The corresponding phase distribution in the flange shaft for each pre-heating temperature is given in Fig. 4 a-d). a) pre-heating temperature 300°C b) pre-heating temperature 400°C c) pre-heating temperature 500°C d) pre-heating temperature 600°C Figure 4. Micrographs of the flange shafts with various pre-heating temperatures, etched The etched micrographs of the flange shafts, given in Fig. 4 a)-d), reveal that an increasing pre-heating temperature leads to an increasing amount of the transformed phase at the outer part of the flange. The width of the transition zone (white area) increases as well. A second observation of
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