Ferrous calcium silicate slags are used in primary and secondary metallurgical processes (described by the FeO-Fe 2 O 3 -CaO-SiO 2 system). Despite the industrial and scientific importance of this system, the phase equilibria have not been fully investigated. Characterization of this slag system is necessary to improve the design and optimization of new and existing metallurgical processes, particularly in relation to fluxing practice and operating temperatures. Experimental methods have been developed to investigate the phase equilibria of these slags involving the equilibration of samples at fixed oxygen partial pressures, rapid quenching, and the analysis of the compositions of solid and liquid phases using electron probe X-ray microanalysis (EPMA) with wavelength dispersive detectors. Liquidus and solidus data are reported for the primary phase fields of spinel, pseudo-wollastonite, and tridymite in the temperature range of 1200°C to 1350°C at an oxygen partial pressure of 10 -6 atm, and at 1250°C at an oxygen partial pressure of 10 -5 atm. The resulting data have been used to construct liquidus and solidus isotherms in the ''FeO''-CaO-SiO 2 system directly relevant to industrial processes.

Ferrous calcium silicate slags (described by the FeO-Fe 2 O 3 -CaO-SiO 2 system) are the basis for a number of slag systems used in nonferrous smelting. Characterization of this slag system is necessary to improve the design and optimization parameters of new processes, including fluxing and operating temperatures. Particularly of interest are the phase relations at intermediate oxygen partial pressures relevant to processes such as copper converting. Experimental data on the phase equilibria of these slags at controlled oxygen partial pressures in the temperature range between 1200°C and 1350°C are discussed, differences between various data sources are analyzed, and discrepancies are resolved. An evaluation of two thermodynamic computer models is undertaken to verify the computer-aided predictions using the experimental data. New experimental data for this system are reported for the temperature condition of 1300°C, defined using the equilibration/rapid-quenching/electron probe microanalysis (EPMA) with wavelength dispersive detectors technique. This new information, combined with results from the previous study, has enabled the equilibrium liquidus compositions to be defined over a wide range of temperatures and oxygen partial pressures.

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