Bending behavior of a hot stamped complex phase steel with tailored properties by local carburization

Abstract

Concerning lightweight design, hot stamping of boron-manganese steels has developed to a state-of-the-art process for manufacturing safety-relevant car body parts in the last two decades. To further improve passenger safety, the idea of components with tailored properties has become even more important. Normally, these process variants aim to bring in so-called soft zones, where a fully martensitic microstructure is prevented to significantly improve ductility. The growing importance of battery electric vehicles and their special requirements call for alternative processes. Especially the battery and its housing are often referred to as a no deformation zone. Concerning this matter, the new process of tailored carburization can be advantageous, since it aims to locally improve strength rather than ductility. Regarding the field of application as a safety-relevant component, the crash behavior is of high interest. In recent years, the three-point bending test has prevailed as a suitable comparative test to estimate crash performance. Within this work, the influence of various carburization parameters on the bending behavior is analyzed. The results reveal that the additional carburization improves punch force at the cost of the bending angle. By analyzing locally carburized samples it is shown, that especially the carburization of the tensile loaded side within the deformation zone is crucial for local strengthening under bending load.