Grundlegende Untersuchung zur Eigenschaftsgradierung pressgehärteter Bauteile durch partielle Zwischenkühlung

Description

The present work addresses tailored tempering with intermediate cooling by radiative heat exchange in the TemperBox® for the targeted grading of mechanical properties in ultra-high-strength manganese–boron steels. In light of increasing requirements regarding crash safety and lightweight design in the automotive industry, this technology enables the realization of localized property variations within a single component. The objective was to develop a comprehensive understanding of the process to allow the targeted adjustment of mechanical properties. Relevant influencing parameters were systematically investigated on both flat and formed test specimens made of 22MnB5 and 8MnB7. These parameters included the intermediate cooling time, transfer time, mask geometry, mask distance, and sheet thickness. An extended JMAK model to describe phase transformation kinetics, as well as temperature-, phase-, and strain-rate-dependent flow curves, were integrated into newly developed material models and experimentally validated. The results demonstrate that tailored tempering by means of radiative heat exchange enables reproducible property grading. Furthermore, precise simulation of radiative heat transfer dynamics provides efficient support for component design. The developed approach allows the targeted design of mask geometries based on the required mechanical properties, including complex geometries such as a patched B-pillar.