FORMABILITY EVALUATION OF SHEET STEELS FOR AUTOMOTIVE APPLICATION

摘要

Usually the main problem of cold-rolled high-strength steels in press operations is the inferior formability compared to extra deep drawing grades. Recently developed new high strength steels like interstitial free steels, bake hardening steels, isotropic steels and multiphase steels offer a very good combination of strength and ductility. Especially, new developed steels associated with TRIP-effect can further improve formability by their high strain hardening ability. Investigations were carried out to clarify the important metallurgical parameters for improved formability. The emphasis is the comparison of strengthening mechanism, flow behaviour, strain hardening rate, strain rate sensibility and strain path behaviour of different steel grades. Improved material modelling is needed for the prediction of press shop results. The paper summarizes the most important structural features for the development of high strength sheet steels and comments on the importance of sophisticated material testing methods.