Effects of the Intermediate Precooling Parameters on the Mechanical Properties of a Tailored Press-Hardened Component in Advanced High-Strength Steel

In recent years, several automotive companies have studied new tailored tempering technologies for press hardening process to produce structural components with tailored mechanical properties, that is, component with both soft zones to absorb energy and hard zones to avoid intrusion during an impact. One of these technologies involves a tailored tempering station interposed between the austenitization furnace and the press machine in which classical stamping and quenching phases occur. In the tailored tempering station, areas that are desired to be ductile are cooled, while areas with the final high mechanical properties remain at the complete austenitization temperature. This work investigates this new tailored tempering technology by means of finite-element models and experimental lab-scale tests. The aim is understanding the influence of cooling rate and the dwell time in the tempering station (precooling time) on the formability and mechanical and microstructural properties of the stamped part. Two different cooling ways of soft areas are explored: 1) by a cooled mask and 2) by a mask with compressed air. Results indicate that an increase in precooling time leads to greater softening in the ductile region but also leads to formability challenges. These effects are even more pronounced with a higher cooling rate.This work investigates a new technology employed in the press hardening process to obtain tailored mechanical properties, namely, the intermediate precooling technology. The study is addressed through finite-element models and experimental tests on a laboratory scale. For the experimental tests, Gleeble physical simulator is adopted to obtain specimens on which to perform metallographic analyses, tensile, and hardness tests.image & COPY; 2023 WILEY-VCH GmbH