Masek, BohuslavBohuslavMasekVorel, IvanIvanVorelOpatová, KaterinaKaterinaOpatováKurka, PetrPetrKurkaHahn, FrankFrankHahnMahn, UweUweMahn2022-03-122022-03-122015https://publica.fraunhofer.de/handle/publica/38914810.1051/matecconf/201521060092-s2.0-84957879822Innovation opens new opportunities in the field of processing hollow semi-products, as it offers the potential for manufacturing complex-shaped structural parts with enhanced properties. This introduces a manufacturing route comprising the following steps: internal high pressure forming, hot stamping and thermomechanical Q&P processing. In this manufacturing route, the demonstration product, a tube-shaped stock, is first austenitized. It is then expanded in a closed die by internal pressure of nitrogen until the material touches the die wall. As a result, it cools down quickly and martensite begins to form. At a temperature above the Mf, the cooling is interrupted and the workpiece is transferred to a furnace and tempered. The furnace temperature is below the Ms temperature. Within several minutes, a mixed microstructure forms, consisting of martensite and stabilized retained austenite. Thanks to this microstructure, the material exhibits a favourable combination of high strength and adequate ductility. Martensite imparts sufficient strength to the material whereas the retained austenite provides ductility. At a carbon level of approximately 0.4 % and with a simple Si-Mn-Cr-based chemistry, strengths of 2000 Mpa and A5 mm elongations of 15 % can be achieved.enhigh pressure forminghollow shafthot stampingQ+P processstructural parts42SiCrconference paper