A Comparison between an Advanced High-Strength Steel and a High-Strength Steel Due to the Spring back Effect

Abstract

In this project, it is planned to carry out a complete microstructural characterization of advanced high strength steels (AHSS) currently used in the automotive industry. These steels have an elastic effect, called spring back effect, during the sheet metal forming of parts. This spring back is the main problem of this family of steels during the production process of the structural components of the automotive industry: especially for dimensional problems in automotive structural components. It is therefore necessary to evaluate changes in microstructure during the stages of sheet metal forming in order to know precisely the microstructural and mechanical behavior of material after being subjected to this effect. Steels studied in this research work are currently used by all major automobile industries, which are dual-phase (DP) 600 and 780. The spring back effect mechanical characterization was performed by means of a mechanical bending test, called as Air Bending. The results indicate that the spring back effect in the DP 780 has the highest spring back rate due to its high mechanical strength due to Hall-Petchphenomenom. The comparison of analyses EBSD before and after bending tests showed a relation between the misorientation of grains and the spring back effect. The results obtained by microstructure analysis of EBSD confirmed the tendency of DP780 absorb a greater amount of energy during the deformation, thus resulting in greater springback effect.