Effect of heating temperature on oxidation behavior of low density steels with medium manganese content

Abstract

The high temperature oxidation behavior of Fe–C (0.22%)–Mn (5.3%)–Al (2.5–3.2%)–Si (2.2%) low density steel was studied in the atmosphere of (2%O2 + Ar) by high temperature oxidation simulation tests. The samples were kept at 900 °C–1300 °C for 30 minutes and the morphology and the content distribution of oxide layer in the scale were characterized by scanning electron microscope combined with energy dispersive spectrometer. The results show that: when the holding temperature is below 1150 °C, the oxidized weight gain increases parabolically with time; when the temperature is maintained above 1200 °C, the oxidized weight gain increases linearly. Oxidation activation energy decreases with experimental temperature from 225.31 to 43.4 kJ/mol and due to formation of liquid oxidation products the value of Ea decreases sharply from 1100 °C.For all range of temperature the outer layer of the scale is FeOn–MnO oxide while the scale is mainly SiO2–Al2O3–FeOn–MnO near the matrix. Few variations could be observed for the morphology of scales when the heating temperature ranged from 900 °C to 1100 °C. When the heating temperature is over 1150 °C the liquid Fe2SiO4 and FeO–SiO2–MnO phases in the scale were newly formed, leading to the penetration of liquid oxide scale into the steel, which makes descaling difficult. Therefore, to facilitate the descaling operation before hot rolling, temperature should be controlled below 1150 °C in the reheating furnace.