Tool and process design for press hardened parts with small-sized tailored properties

In the last years press hardening has become the leading technology for the production of high-strength structural components in car manufacturing. As a result the trend of components with optimized properties, so-called tailored parts, can be observed. These components have different local mechanical properties which leads to certain benefits, including production process and crash behavior. A particular group of these tailored parts represent components with small-sized tailored sections. This can lead to advantages in the stability of spot welds or the production of hybrid components by mechanical joining. Currently, these properties can only be produced in the process step subsequent to the press hardening step. This paper outlines how mechanical properties of a small-sized section of the component can be affected by particular tool technology in the actual press hardening step. First the state-of-the-art of the production of small-sized tailored properties is briefly described. The tool technology in focus is explained. This uses flexible heated elements (up to 800 °C) which are in contact to the workpiece. This locally influences the cooling behavior of the workpiece and its phase transformation during the cooling process. The results of the numerical analyses (FEM) and experimental studies are presented and discussed in detail. It is shown how the input variables such as temperature and diameter of the heated elements influence the output variables as minimum hardness and size of the sections with tailored properties.