High-efficiency reduction behavior for the oxide scale formed on hot-rolled steel in a mixed atmosphere of hydrogen and argon

In this study, a novel double-stage reduction method of “low temperature and high temperature” was proposed to improve the reaction efficiency of the hydrogen reduction technology of the oxide scale formed on hot-rolled steel. The reduction behavior of the oxide scale in 20 vol% H2–Ar at various reduction methods was investigated in detail. The weight change of specimen under various reduction methods was measured by thermogravimetric analysis, and then the reduction degree and the reaction rate were calculated based on the measured value. Scanning electron microscopy was used to observe the surface and the cross-sectional morphologies of the oxide scale after the reduction reaction, and the mass percent of oxygen and iron in the cross-sectional reduction layer was measured by energy-dispersive spectroscopy. X-ray diffraction was applied to characterize the phase transformation of the oxide scale in the heating process, and the phase composition of the oxide scale and reduction layer. The experimental results indicated that the reduction degree and the reaction rate of the oxide scale during the double-stage reduction method increased significantly compared with the traditional single-stage reduction method in the range of 500–800 °C. The mechanism of the double-stage reduction method was discussed from two aspects of the phase transformation of the oxide scale and the restrictive link of the gas (H2)–solid (Fe oxides) reduction reaction.