Effects of Si Content on the Growth of Oxide Layers in Carbon Steels during the Heating Process

Abstract

A prevalent metal surface defect is hot-rolled iron oxide; thus, it is critical to regulate the production and growth of oxidized iron during the hot-rolling process. To analyze the influence of Si content on the growth laws of the oxidized layer in carbon steel during heating, three types of carbon steel with significant differences in Si content were selected for research on the growth laws of the oxidized layer at different heating temperatures. The production law and micromorphology of the oxidized layer were analyzed using methods such as scanning electron microscopy and thermodynamic phase diagram calculation, and an oxidation dynamic model was obtained. The predicted control values of the model are highly consistent with the measured values. This study reveals that the heating temperature significantly impacts the thickness of the oxidized layer of carbon steel. At temperatures below 500 °C, the oxidation is not evident, and the layer is thin. Between 500 °C and 900 °C, the steel’s composition affects the thickness. Carbon steels with high Si content form a dense iron olivine layer, which slows down the oxidation rate. However, heating temperatures above 900 °C cause the protective oxidized film to reach the melting point of iron olivine, increasing the oxidation rate. At 1200 °C, the oxidized layers of the three types of carbon steel remain consistent. This paper’s research findings offer theoretical guidance for large-scale industrial production practices and serve as a reference for similar studies on steel oxidation behavior.