On the Behavior of MnO, SiO₂ or Cr₂O₃ Mixed with SolidIron during Heating in Reducing Atmosphere

Abstract

In the previous studies concerning the behavior of oxide inclusions in steels in the hot-rolling process, the steel specimens were made by the method of powder matallurgy: that is, the iron powder was mixed uniformly with a certain amount of synthetic oxide inclusions, shaped by pressing, and sintered in H₂ atmosphere. It was found that a part of mixed oxide inclusions disappeared by reduction.
This phenomenon suggested that a part of the synthetic oxide inclusions was reduced by H₂, and the metallic elements produced by the reduction were then dissolved in solid iron. Consequently, the activity of those elements was lowered, and the reducibility of oxides increased considerably.
The present investigation was carried out in order to make the behavior of oxides in steels clearer and know more about the reduction. The specimens made of the iron powder containing a certainamount of MnO, SiO₂ or Cr₂O₃ respectively were held at the constant temperature of 800°C to 1100°C and in the H₂-H₂O gas under the constant P_H2O/P_H2, ratio. When the equilibrium state was attained, the change of weight of these specimens due to the reduction of oxides was measured by thermo-balance, and the reducibility of the oxides at each temperature was investigated.
Furthermore, the activity and the activity coefficient of the Mn, Si and Cr elements in solid Fe-basealloys were calculated by combining the experimental value of Mn, Si and Cr concentrations and the thermochemical data concerning the reduction of the oxides.