Comparison of springback effect of the dual phase steels 600 and 780 function to microstructure and mechanical properties
Erika Aparecida da Silva1; Antonio dos Reis de Faria Neto1; Marcelo dos Santos Pereira1; Jade Pecune2; Joël Alexis2
1 UNESP; 2 ENIT - FRANCE
doi:10.20906/CPS/COB-2015-0261
Resumo
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 springback effect, during the sheet metal forming of parts. This springback 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, wich are dual-phase (DP) 600 and 780. The springback effect mechanical characterization was performed by means of a mechanical bending test, called as Air Bending. It was also evaluated the mechanical properties of the material defined by the tensile test. The results of the tensile test showed that the DP 780 presents a superior modulus of resilience (σyield^2/2*E) to the DP 600. Furthermore, steels's microstructural characterization was performed by identifying and quantifying the present phases in coexistence by means of digital image processing and EBSD. The mechanical tests were performed comparing different dimensions of samples and was observed that when using smaller steel sheets, the springback effect increased. For smaller sheets, DP780 steel presented an springback effect of 8.7 degrees higher than DP600 steel. Already, when the sheets were of larger dimensions, DP780 steel presented an springback effect of 5.4 degrees higher than DP600 steel. The results of EBSD showed that the size of grain is different between the steel DP780 and DP600. The average sizes of grains in the steel sheet DP780 and DP600 are respectively 1,83 ± 1,94 mm and 6,11 ± 4,39 mm. With respect to the structure of the grain, the
Palavras-chave: springback; morphology; resilience; dual-phase; steels