Sheet steels for cold forming of car-body parts

In this thesis problems were faced during the stamping operation (drawing phase exactly) of a 2.5 mm thick steel sheets. The main focus of this thesis is to investigate which is the optimal steel for this stamping operation. In order to avoid the problem of edge fractures in the drawing phase. For this scope three different steel alloys were characterized, DP600, Fe E340, and FB H590. However, the focus material of interest and believed to best suit this application was the DP600 since it has some distinct mechanical properties regarding strength, ductility and strain hardening behavior. The characterization tests and microstructure analysis conducted in the research for all three steel alloys: Chemical analysis, metallographic analysis (grain size, phase constituent, banding…etc.), tensile test. These characterization tests have been specially selected to reveal the micro and macro characteristics of the studied steel sheets. Chemical tests were conducted on all three different materials to be able to characterize their chemical composition. These results helped to understand some microstructure features later on in the research. In the metallography field, the different tests were conducted according to different standards issued by the ASTM and ISO standards. Allowing a standardized procedure for all three specimens and minimizing the bias of different factors. The results were reported accordingly in tables and in a comparative straightforward way representative of the different steel alloys characteristics. A tensile test was performed in which in-plane stretching is the dominant failure mode. All three specimens were tested until failure and results were reported in terms of tensile strength, yield strength, strain hardening coefficient, strain ratio, and the total elongation.