Effect of Annealing Time on Oxides Phases and Morphology along Oxidized Depth of Fe-3%Si Steel during Decarburization

The decarburization experiments were carried out at different annealing temperatures, PH2O/PH2 and times. Under the annealing conditions in present work, the optimum annealing condition of decarburization was that annealing temperature was 1108 K under PH2O/PH2=0.317. The oxides morphology in oxidized layer was studied. The concentration distribution of silicon and oxygen along the oxidized depth was analyzed. The relationship between oxides phases, oxides morphology and concentration distribution of silicon and oxygen was established. Results showed four zones presented in oxidized layer from the atmosphere/steel interface to the steel matrix, which were enriched zone of oxides, depleted zone of oxides, spherical zone of oxides and lamellar zone of oxides in sequence. The oxidized layer of Fe-3%Si steel was composed of iron oxide, fayalite and silica. With the increase of oxidized depth, there was still some unreacted silicon atoms remained in the oxidized layer.