Carburization of iron using CO−H2 gas mixture

Abstract

Iron carbides formed on the surface of iron and iron oxide samples at 640 °C in a gas mixture of CO−H2 were characterized by scanning electron microscopy (SEM), Mossbauer spectroscopy, X-ray diffraction patterns (XRD), and by measuring mass change. The Fe3C amount of the samples has been quantitatively evaluated by the weight change during carburization. While Fe2O3 powder was mostly completed to Fe3C in the early stage, within 5 min after reduction reactions, the conversion of Fe powder sample to Fe3C (iron carbide) was almost finished after 10 min. The carburization rate of a Fe sheet was very slow and intermediate products (Fe2C, Fe5C2) were observed. This phenomenon is largely due to the difficulty of carbon diffusion into its dense surface. It was found that the carburization rate was affected by change of surface conditions and surface area by reduction, degradation, and cracks at high temperature. This study should help provide a fundamental understanding of carburization in the field of iron-making and suggest a direction for its further development.