The effect of the Si content on the morphology and amount of Fe2SiO4 in low carbon steels

Abstract

In order to study the effect of the Si content on the morphology, amount, and distribution of fayalite (Fe2SiO4), three low-carbon steels with different Si contents were selected, and reheating tests were conducted in an industrial furnace in a hot strip plant. The results show that Si distributes in two forms—first, Fe2SiO4, in the innermost layer of the oxide scale, and, second, granular SiO2, dispersively distributed in the matrix near the scale. In addition, Fe2SiO4 appears in a net-like form in the innermost layer of the oxide scale close to the iron matrix when the Si content is 1.21 wt. %. However, no obvious net-like Fe2SiO4 is observed when the Si content is less than 0.25 wt. %. Moreover, the inhibition effect of the solid Fe2SiO4 on the oxidation reaction plays a more important role than the promotion effect of the liquid Fe2SiO4 during the entire oxidation reaction. Therefore, the total thickness of the scale decreases with the increase in Si content.