Cold-rolled complex-phase (CP) steel grades with optimised bendability,stretch-flangeability and anisotropy (CP-Steels) : final report

This RFCS project started on 1 July 2006 and was coordinated by Swerea KIMAB. Other partners engaged in the project were Ruukki Metals Oyj (Ruukki), Rheinisch-Westfälische Technische Hochschule (RWTH), SSAB EMEA (SSAB) and voestalpine Stahl GmbH (voest). This final technical report includes contributions from all partners and describes the results of the research carried out over the entire project. The overall goal of this project was to identify microstructures with optimised balance between strength, bendability and stretch-flangeability and to develop guidelines on how to produce this cold rolled sheet steel through three processing routes, i.e. by continuous annealing with gas cooling, continuous annealing with quenching, and the third route was hot dip galvanizing. The objectives were to produce material with the following properties : a tensile strength of more than 800 MPa, a hole expansion ratio (HE) of more than 35 % and a bending angle, Ri/t<1. This has been obtained through a sequential narrowing of the processing parameters and the chemical composition, using laboratory simulations in several steps in parallel with some on line trials. The final results were then achieved in full scale trials. The required property goals for the project were reached for all processing routes, although their different design has introduced differences in the microstructures that are reflected in the properties.