In-situ characterization of a locally carburized complex phase steel for manufacturing of tailored semi-finished products

• Applicant: Professorin Dr.-Ing. Marion Merklein
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 450281370

Hot stamping of ultra-high-strength steels has developed to a state of the art process for manufacturing safety-relevant car body parts with respect to lightweight design. Further improvement of passenger safety can be achieved by locally adapting the mechanical properties. In terms of process design, the development of the microstructure throughout the process stages is significant. Laser-ultrasonics enables the in-situ determination of microstructural changes, such as grain growth or phase transformation. In recent years, this measurement method was already applied for the investigation of processes like rolling but is unknown in the context of hot stamping. The aim of this project is the in-situ characterization of a locally carburized complex phase steel on the basis of grain growth and phase transformation obtained by laser-ultrasonics. Through fundamental scientific investigations of the influencing factors on microstructure and mechanical properties, a process window for local carburization at temperatures above 950 °C will be identified. Furthermore, the prediction accuracy of numerical simulation should be improved by considering the data from in-situ characterization. Based on the identified process window the warm forming behavior of the carburized and non-carburized complex phase steel will be investigated. Besides temperature and strain rate, the modeling of the flow behavior is carried out with respect to further influencing factors such as the carburization parameters. Moreover, the transferability of measurement data obtained by laser-ultrasonics to model the phase transformation in numerical simulation is analyzed. Through experimental investigations, the numerical material models will be validated and verified.

• DFG Programme: Research Grants