Abstract
The thermodynamics of manganese oxide in high-MnO-containing slags was investigated using the chemical equilibrium method in the temperature range of 1623 to 1723 K. MnO-SiO2-Al2O3 slags were brought into equilibrium with molten silver (Ag) under controlled CO/CO2 gas atmosphere. The equilibrium Mn concentration in the silver was measured by ICP-AES (inductively coupled plasma atomic emission spectroscopy) analysis after the experiment. Slag samples were analyzed by EPMA (electron probe microanalyzer) analysis. The obtained activity aMnO and activity coefficient γMnO were derived as a function of the slag composition and temperature. The activity coefficient of MnO within the investigated slag system increased with an increasing MnO/SiO2 ratio. The derived temperature dependence of the activity coefficient and partition ratio of Mn between the metal and the slag was strongly influenced by the slag composition. The thermodynamic assessment of the activity and activity coefficient of MnO was carried out by applying the regular solution model (RSM) on the basis of interaction energies of the cations and with FactSageTM 7.3. The theoretical calculations were compared with the experimentally derived values.
Highlights
Manganese is an essential alloying element used during the production of high-grade steel because of its properties, and it is present in most commercially made steels
The activity and activity coefficient of MnO were experimentally measured in the ternary MnO-SiO2-Al2O3 slag saturated with SiO2 on the basis of the equilibrium Mn content in the molten silver under a controlled of the regular solution model (RSM) and the conversion factor proposed by Ban-ya can only represent the system adequately for activity values below 0.15 [17,22]
The activity and activity coefficient of MnO were experimentally measured in the ternary MnO-SiO2-Al2O3 slag saturated with SiO2 on the basis of the equilibrium Mn content in the molten silver under a controlled gas atmosphere at 1623, 1673 and 1723 K
Summary
Manganese is an essential alloying element used during the production of high-grade steel because of its properties, and it is present in most commercially made steels. Mn reduces embrittlement caused by sulfur and improves the mechanical properties of steels, e.g., strength and hardness. Impurity content in the alloy, especially the phosphorus concentration, is absolutely critical, since phosphorus in steel separates at the grain boundaries and causes embrittlement [1,2,3,4,5]. Manganese alloys are made by reducing manganese ore composed of manganese, iron, and silicon oxides as well as phosphorus. During this reduction process, phosphorus oxides are reduced along with manganese oxides, and phosphorus is transferred into the alloy. It is necessary to decrease the P content in raw materials, i.e., in the ferromanganese or manganese ore
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