Initial Oxidation of Fe–Cr Alloys at Different Temperatures and Atmospheric Conditions: A ReaxFF Molecular Dynamics Approach

Abstract

Oxidation behavior during the continuous casting process significantly impacts steel quality. This study investigated the oxidation process of iron–chromium (Fe–Cr) alloys at different temperatures and atmospheric conditions using the molecular dynamics method. Results indicated that during oxidation, Fe and Cr atoms lost electrons while O atoms gained electrons. The ratio of consumed O positively correlated with temperature and O concentration. Oxidation severity was higher at increased O concentrations and 1373 K, with the most severe oxidation occurring at lower temperatures with higher O concentrations. The oxidation rate constant in wet O concentrations was lower compared with pure O, with a higher oxidation kinetic index, indicating that continuous casting billets in water-cooled conditions should have a limited duration. The initial oxidation kinetics of the Fe–Cr alloy surfaces are all manifested as the initial rapid oxidation, followed by the slow oxidation growth process Additionally, Mean-Squared Displacement (MSD) of Fe atoms is larger than that of Cr atoms and Cr oxidizes in the inner layer to form a dense oxide, it prevents Cr from continuing to oxidize and diffuse outward, thus generating Fe-rich products on the surface of Fe–Cr alloys.