Internal oxidation of Fe–3%Si alloys annealed under H2O–H2 atmosphere

Abstract

AbstractInternal oxidation phenomena during decarburization annealing are very important in the manufacturing process of grain oriented electrical steel. In the present study, the internal oxidation of nearly pure Fe–3%Si alloy was investigated, as a basic study for decarburization annealing. Annealing was performed at various $P_{{\rm H}_{{\rm 2}} {\rm O}} /P_{{\rm H}_{{\rm 2}} } $ ratios and at 1123 K for 300 s. The transition of external to internal oxidation took place at $P_{{\rm H}_{{\rm 2}} {\rm O}} /P_{{\rm H}_{{\rm 2}} } $ around 0.01. The morphologies of oxide in the internal oxidation zone (IOZ) were filamentary or needle‐like shapes and different from the reported oxide shapes in industrial electrical steel. These peculiar morphologies affected the kinetic aspects such as the depth and the enrichment of oxide in the IOZ.