Oxidation behaviour of hot-rolled Si-containing steel in water vapour between 600 and 900°C

Abstract

The oxidation behaviour of hot-rolled Si-containing steel in the water vapour atmosphere was investigated. The hot-rolled steel strips was produced from conventional slab with silicon content of 0.026 to 0.193 wt.%. A Thermogravimetric measurement was conducted for observing oxidation kinetics on steel oxidised in 20%H2O/Ar between 600 and 900°C at 16 h. The result shown that the oxidation rate and scales thickness decreased with increasing silicon content in the hot-rolled steel. The oxidation temperature was affected to oxidation rate, which was increased with increasing temperature. The parabolic oxidation kinetics was observed. The measured activation energies were 151 and 181 KJ.mol-1 for the hot-rolled 0.026 wt.% Si and 0.193 wt.% Si steels respectively. The metallography of the oxide scales on the hot-rolled steel was examined by scanning electron microscope (SEM). X-ray diffraction (XRD) was performed for phase identification. The oxide scales was formed on the hot-rolled steel consisted of hematite Fe2O3, magnetite Fe3O4 and wustite FeO as well as Fe2SiO4. The internal oxidation was also observed in the both studied steel particularly in the 0.193 wt.% Si steel which was shown oxide contained Si band. The hot-rolled 0.193 wt.% Si steel was exhibited lower oxidation rate. This was due to the oxide contained Si, which was improved the passivity of the steel.