Growth Law of Solid-State Decarburization Oxide Layer of Fe–C–Si Alloy Under CO2–CO Atmosphere

The experiment is carried out on a 0.5 mm Fe-0.1C-3.5Si silicon steel. Solid-state decarburization tests are carried out under CO₂–CO/H₂O–H₂ atmosphere to analyze the evolution of the oxide layer in the decarburization process under different atmospheric conditions. The results show that the decarburization effect and decarburization rate in CO₂–CO atmosphere are significantly better than that in H₂O–H₂ atmosphere. Under the CO₂–CO atmosphere, the gas flow rate is 650 mL min⁻¹, the thickness of the oxide layer increases gradually with the extension of decarburization time. At a gas flow rate of 950 mL min⁻¹, the thickness of the oxide layer in the cross-section becomes thicker and thicker with the increase of decarburization time, but the rate of increase of the thickness slows down. As the decarburization temperature increases, the striped SiO₂ oxide band forms between the matrix and the thin oxide layer thickens. The thickness of the oxide layer is about 6.1 μm at the decarburization stagnation, when the banded SiO₂ grooves are more uniform and regular. In H₂O–H₂ atmosphere, irregular strip-shaped silicon dioxide grooves form when decarbonization stops, and the thickness of oxide layer is about 15.9 μm.