Investigation of masking concepts for influencing the austenitization process during press hardening

One possibility to adjust tailored properties in hot stamping is the application of a masking concept to prevent a complete austenitization. In this study different concepts were investigated in order to use them as a suitable masking. A simulation model of the heating phase was developed for the purpose of predicting the resulting microstructure and hardness. Experimentally determined temperature profiles were used for the numerical model. The numerical results of the temperature profile and hardness were validated by experimental investigations and non-destructive hardness measurements. The simulated hardness is in adequate agreement with the measured hardness

Tailoring Soft Local Zones in Quenched Blanks of the Steel 22MnB5 by Partial Pre-cooling with Compressed Air

The high-strength boron steel 22MnB5 steel is widely used for automotive lightweight constructions. A novel approach is promising to tailor strength and ductility in the hardened condition using locally pre-tempered sheets for the hot stamping process. It results in the formation of locally soft spots where mechanical joining is subsequently intended. A slow pre-cooling of the later joining zones with cooling rates below a certain critical cooling rate for obtaining a decreased strength in these regions is required. A tubular air cooling system suited for this task is presented and tested in a process where the subsequent quenching of the overall sheet is realized by rapid cooling in a water bath. Varying the air pressure and cooling duration allows controlling the size of the softened local spot in a wide range and still obtaining a bainitic microstructure. Using two-stage cooling with point jet nozzles and a subsequent hot stamping process with water-cooled dies resulted in a main sheet hardness of about 470 HV5 and of 260 HV5 in the pre-cooled spots, respectively

Einsatzmöglichkeiten von zerstörungsfreien Sensortechniken innerhalb der Wertschöpfungskette Blechverarbeitung

An die Unternehmen aus der Blechumformung, insbesondere der Automobilindustrie als größter Hersteller und Abnehmer von umgeformten Blechteilen, werden zunehmend höhere Ansprüche an Bauteile und Prozesse gestellt. Viele Prozesse befinden sich, z. B. aufgrund von Leichtbaukonzepten, zunehmend an ihren Prozessgrenzen. Eine steigende Verarbeitungskomplexität, immer geringer werdende Blechdicken, Chargenschwankungen der Werkstoffe sowie Unsicherheiten durch das System Werkzeug/ Maschine, die Tribologie, die Peripherie und Einflüsse des Maschinenbedieners führen zu einer verminderten Prozesssicherheit. Eine Folge derartiger Einflussfaktoren sind temporär auftretende, teilweise nur schwer identifizierbare Schädigungen und störende Auswirkungen innerhalb der Prozesskette Blechverarbeitung