Investigation of the formability (including hydroforming capability), springback and crash resistance of modern high strength steels under development
To achieve a defined strength level several hardening mechanisms can be used. Grain refinement, solid solution hardening, second phase hardening and precipitation hardening all raise the tensile strength but have opposite effects on other user properties. To assess the effect of hardening mechanisms and microstructure on tensile and formability properties, a wide range of high strength steels (HSLA, DP, multiphase, TRIP, etc.) was generated with a strength level ranging from 600 MPa to 1400 MPa. Both laboratory and industrial steel grades were tested. A microstructural analysis was performed and the mechanical properties were determined. Flow curves were obtained by both compression test and a newly developed tensile test on a very small specimen. The effect of temperature and strain rate on tensile properties was investigated. The influence of structure on the forming behaviour and crash resistance was investigated. No big differences in deep drawability and stretchability results were observed among the steels. The hole expansion possibility, however, was greatly influenced by the structure. Surprising bending results were obtained even for the highest strength steels. Hydroforming was carried out on straight and bent tubes. Very high deformation strains, far exceeding the forming limit diagram were obtained. The need for FLD based on complex strain paths for these high strength steels became clear. The crash behaviour was studied and compared with computer models in order to eliminate the thickness parameter and keep the weight saving possibility of each grade.
Bibliographic Reference: EUR 21414 EN (2005), 149 pp. Euro: 25
Availability: Katalogue Number: KI-NA-21414-EN-S The paper version can be ordered online and the PDF version downloaded at: http://bookshop.eu/
ISBN: ISBN: 92-894-9693-2
Record Number: 200518375 / Last updated on: 2005-10-05
Original language: en
Available languages: en