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Neue innovative Konzepte für die Innenhochdruckumformung

: Masek, Bohuslav

Liewald, Mathias:
Effizient formen! : 13. und 14. Mai 2014, Fellbach
Frankfurt: MAT-INFO Werkstoff-Informationsgesellschaft, 2014
ISBN: 978-3-88355-400-6
International Conference New Developments in Sheet Metal Forming <2014, Fellbach>
International Conference New Developments in Hydroforming <8, 2014, Fellbach>
Fraunhofer IWU ()
Presshärten; Innenhochdruckumformen; Quenching; Martenzit

Innovation opens new opportunities in the field of processing hollow stock, 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 1900-2000 MPa and elongations of 15-20 % can be achieved.