Numerical Simulation of Decarburization Kinetics for Fe-3%Si Steel during Annealing

In order to reduce the magnetic aging produced in the use of oriented silicon steels, the carbon content in the steel matrix of products is less than 50 ppm. In this study, the decarburization reaction kinetics on Fe-3% Si steel surface and the diffusion mechanism of carbon in the steel were analyzed during decarburization annealing. Based on the balance between carbon diffusion flux in the steel matrix and the decarburization reactions on steel surface, the mathematical model for decarburization of Fe-3% Si steel with oxidation behavior was established. The boundary conditions of the model were given and the model was solved by numerical method. The decarburization experiments were carried at different annealing time, annealing temperature and P-H2O/P-H2. Results showed that the residual carbon content in the steel decreased and oxygen content increased continuously as the annealing time increased. With the increase of annealing temperature and P-H2O/R-H2, the residual carbon content in the steel first decreased and then increased. But the oxygen content increased continuously. Based on the experimental results, the decarburization model was modified from three aspects, which were phase transition in steel matrix, temperature change of steel in heating process and parameters change of decarburization kinetics. When the decarburization model was modified, the values of simulated results were in good agreement with the experimental results, which proved the validity of the model.