New Advanced Ultra High Strength Bainitic Steels: Ductility and Formability (DUCTAFORM)

Download or read book New Advanced Ultra High Strength Bainitic Steels: Ductility and Formability (DUCTAFORM) written by and published by . This book was released on 2013 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this proposal is to develop AHSS both hot rolled and annealed cold rolled bainitic steels with an optimal ductility and work hardening comparable to drawing steels, and/or keeping a suitable bending and stretching behaviour. In addition, forming processes such as roll-forming and hardening, and press-hardening were optimised to achieve a carbide free bainitic microstructure in final products such as structural safety components in the car body i.e. A-beam, roof-beams, car bumpers and side impact beams. Hot rolling of carbide free bainitic steels with 1100 MPa of yield strength and high toughness (KV(-40oC)>30 J) was proved to be challenging. Apart of a high carbon content (̃0.3wt.%), chemical composition requires of a high manganese content (̃2wt.%), which leads to a high risk of banding. By contrast, annealed cold rolled bainitic steels designed for continuous annealing line achieved far higher uniform elongation, better stretching ability and formability than that in DP980 and Martensitic 1400 steels considering the same range of ultimate tensile strengths. Finally, roll-forming simulations of bainitic cold rolled steels obtained by interrupted quenching and salt bath at different temperatures showed an excellent formability without crack formation in comparison to martensitic 22MnB5 reference steel. Likewise, press-hardening trials of hat shaped profiles using a novel quench and partitioning post heat treatment of cold rolled designed steels showed promising tensile results in comparison to same commercial 22MnB5 profiles.