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Process design of press hardening with gradient material property influence

: Neugebauer, Reimund; Schieck, F.; Rautenstrauch, A.

Preprint urn:nbn:de:0011-n-1646203 (3.3 MByte PDF)
MD5 Fingerprint: 29d4d07ec66039ce29087e3de117af5a
Copyright AIP
Created on: 16.6.2011

Menary, G. ; American Institute of Physics -AIP-, New York:
14th International ESAFORM Conference on Material Forming 2011 : 27-29 April 2011, Belfast
New York, N.Y.: AIP Press, 2011 (AIP Conference Proceedings 1353)
ISBN: 978-0-7354-0911-8
ISBN: 0-7354-0911-0
ISSN: 0094-243X
International Conference on Material Forming <14, 2011, Belfast>
Conference Paper, Electronic Publication
Fraunhofer IWU ()
hot sheet metal forming; material characterization; thermo-mechanical processing

Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganeseboron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steel sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.