Investigation of selective oxidation during cooling of hot-rolled iron-manganese-silicon alloys

The kinetics of selective oxidation in iron-manganese-silicon alloys of varying silicon contents was examined at 700°C and oxygen partial pressure of 2.9×10−22 bar for up to 2 h. The investigation revealed a linear mass gain over time, suggesting oxygen uptake as the rate-controlling step of reaction. Internal oxidation depth particularly along grain boundaries increased considerably with increasing silicon content. Differences in microstructure and near-surface chemistry of the alloys as a function of the silicon content are discoursed on. The results point to the crucial role of a thin oxide layer, a solid solution between FeO and MnO, in the oxidation process.