Mechanism of silicon distribution and oxide morphology in the internal oxidation zone of grain-oriented silicon steel during decarburization

Abstract

Grain-oriented silicon steel is decarburized in N2-H2-H2O at 835 ℃ for different time. The oxide is spherical, spherical-lamellar and lamellar from outside to inside, and lamellar oxide would gradually degenerate to spheroid as oxidation front moves inward. Concentration-depth profiles for silicon exhibit damping-like oscillations. Wagner’s model is extended to illustrate the intrinsic mechanism by introducing the hypothesis of flux imbalance at oxidation front with finite thickness. Based on the extended model, the dissolved oxygen concentration at steel surface is lower at initial decarburization, and the damping-like oscillations of concentration profile for silicon follow from cyclic change in oxidation front velocity.