Efeito do substrato dos aços IF nas propriedades do revestimento Galvannealed

Abstract

The galvannealed material results from an additional annealing of the galvanized material at high temperatures enough to provide zinc and iron interdiffusion. During the beginiig of the process, there is a competition betwen the phases to nucleate and grow. Later, the richer phases in iron grows at the expenses of the richer phases in zinc. In the process,temperature and time are the main variables, although other variables causes significant modifications on the final product. The main feature of the galvannealing process in the integration with previous processing units because they are responsible for the main sourcesof influence on the galvannealed product. In the present work, the study of the galvannealing process on ultra low carbon steel substrates containing three levels of chemical composition was carried out. The galvanizing bath about 0,12% Al and operated at 470°C. Thegalvannealing temperature range was betwen 470°C and 570°C in steps of 50°C. The main experimental techniques used, were the scanning electron microscopy, X-ray diffraction and iron coated weight. The discussion of the results focus on several aspects related to thegalvannealing process, process window and the substrate chemistry. As a conclusion, it was found that the process parameters in the studied substrate did significantly affect the galvannealing alloying kinetics for the process conditions and substrate chemistries studied.