State of Strain and Development of Microstructure of 22MnB5 Steel and Al-Si Coating During Deep Drawing of Automotive B Pillar

The analysis of the development of the microstructure of deep drawn automotive B pillar, as well as the analysis of deformation based on numerical simulation and experiment, was performed. The microstructure of steel sheet as well as Al-Si coating after various stages of B pillar production was investigated. It was found that the obtained microstructure of the B pillar was significantly different from that described in many studies as a proper one. The microstructure of the investigated material consisted of martensite, bainite, and a small amount of ferrite. Al-Si coating, despite its morphological changes, remained on the surface of B pillar and, in spite of this, did not fully eliminate oxidation and decarburization of B pillar material. The analysis of the state of strain allowed to evaluate the deformation safety of the process, as well as to verify the simulation results through measurements of sheet thickness variations.