Investigation on basic friction and wear mechanisms within hot stamping considering the influence of tool steel and hardness

摘要

Hot stamping is a well-established technology for producing safety relevant car components. The use of hot stamped components in modern car bodies offers the possibility of improving crash performance due to their high strength while simultaneously decreasing the fuel consumption by reducing sheet thicknesses and thus weight. Hot stamped components are mainly produced using the boron-manganese-alloyed steel 22MnB5. To prevent formation of oxide layer during heat treatment and subsequent forming process, AlSi-coatings are applied on the workpiece surface. Since hot stamped parts are formed at temperatures between 600 degrees C and 800 degrees C, no suitable lubricants have been found yet. Thus, severe wear and high friction occur during the forming process affecting final part quality as well as life-time of hot stamping tools. Consequently, measures for reducing tribological load during the forming operation have to be found in order to improve part quality and increase efficiency of industrial hot stamping applications. Within this study, the impact of the tool material on friction and wear is analyzed by comparing the tribological behavior of the newly developed high thermal conductivity hot work tool steel Thermodur 2383 Supercool with the reference material 1.2367. Both are characterized by means of flat strip drawing experiments under hot stamping conditions. The experiments are performed with different hardness values for each of the two tool materials. Furthermore, wear behavior is analyzed using scanning electron microscope and confocal microscope measurements of workpiece and tool. Hereby, fundamental wear and friction mechanisms within hot stamping applications are identified. The results of this study help to increase the process understanding regarding the tribological conditions during hot stamping. In future research work tool-side measures for increasing the life-time of hot stamping tools will be developed.