SOLUBILITY AND ACTIVITY OF CALCIUM IN MOLTEN IRON IN EQUILIBRIUM WITHLIME AND THERMODYNAMICS OF CALCIUM-CONTAINING IRON MELTS

Determination of solubility and activity of calcium in liquid Fe+Ca+O alloys in equilibrium with lime at 1 823 K were carried out by means o f the distribution equilibrium of calcium via gas phase in a closed ta ntalum vessel between iron melts and Ag+Ca alloys. Solubility of calci um in equilibrium with lime increases with increase of calcium potenti al of the system. Within the concentration range from 3 to 270 mass pp m Ca, the activity coefficient of calcium referred to the hypothetical pure liquid calcium does not change apparently and its value is 7.8+/ -0.7. Solubility of calcium in iron under the condition of both CaO an d Ca+O alloy saturation was found to be 270+/-15 mass ppm. The partial pressure of calcium at this three phases equilibria is 1.2 x 10(5) Pa . Based on the results and the literature data, determination procedur e of interaction parameter between calcium and oxygen in molten iron w as discussed.