Characterization of surface oxidation and numerical simulation of oxidation kinetics for Fe-3%Si steel during decarburization

Abstract

During the decarburization annealing process, the oxidized layer formed on the Fe-3% Si steel surface may affect its subsequent nitriding and secondary recrystallization. The decarburization experiment is carried out in the N2 + H2 + H2O at an annealing temperature 835°C. The morphology evolution of the oxidized layer on the steel surface under different annealing times is studied, and the distribution trend of silicon and oxygen in the oxidized layer is analyzed. For the phenomenon of selective oxidation behavior of Fe-3% Si steel, its oxidation kinetic model is established by using mass conservation equations, which is modified by probabilistic statistical method according to the experimental results. The results show that the oxidized layer of Fe-3% Si steel is composed of silica and fayalite after decarburization annealing. The oxidized layer thickens with the increase of annealing time. This oxidation kinetics model is suitable for calculating the mass fraction distribution of silicon and oxygen in the oxidized layer, the thickness of oxidized layer, and the content of oxygen in the steel. The model is a very powerful tool in the simulation of Fe-3%Si steel during decarburization.