The effect of MgO on liquidus temperatures of fayalite slags
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RODUCTION
MOST copper smelting slags lie in the vicinity of the fayalite (2FeO?SiO2) primary phase field. The major components of the copper smelting slags are iron oxide, silica, and calcium oxide. In practice, however, the slags contain not only “FeO,” CaO, and SiO2, but also other components such as Al2O3 and MgO that are introduced through the mineral concentrates, fluxes, recycled converter slag, coal ash, or dissolved refractories.[1–4] As a first approximation, the system “FeO”-CaO-SiO2 can be used to estimate the liquidus temperatures of the fayalite slags. The system “FeO”-CaO-SiO2 in equilibrium with metallic iron was first investigated by Bowen et al. who carried out research in the high silica region.[5] Allen and Snow studied this system in the low silica region.[6] Muan and Osborn then constructed the whole of the ternary diagram based on these experimental data.[7] Authors reinvestigated this system in fayalite primary phase field in equilibrium with metallic iron.[8] The system “FeO”-MgO-SiO2 in equilibrium with metallic iron has been studied by Bowen and Schairer.[9] Wu et al.[10] conducted a thermodynamic assessment of this system. Their results show that the liquidus temperatures in the fayalite primary phase field are gradually increased with increasing MgO content. However, to determine the liquidus temperature accurately in the multicomponent system MgOCaO-“FeO”-SiO2, the effects of CaO should be taken into account. A number of researchers[11–17] have investigated phase equilibria in the system MgO-CaO-“FeO”-SiO2 in equilibrium with metallic iron. However, investigations of magnesia-containing slags have not been carried out in the composition ranges relevant to copper smelting so that the results cannot be used to accurately predict the liquidus temperatures of fayalite slags. In fact, to date, no experimental information appears to be available in the literature on the effect of magnesia on the liquidus temperatures of fayalite slags. B. ZHAO, Research Officer, E. JAK, Senior Research Fellow, and P.C. HAYES, Associate Professor, are with PYROSEARCH, Department of Mining, Minerals and Materials Engineering, The University of Queensland, St Lucia, Queensland, 4072, Australia. Manuscript submitted November 24, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS B
The objective of the present work is to determine the liquidus temperatures in the fayalite primary phase field, i.e., in the multicomponent systems MgO-“FeO”-CaOSiO2, in equilibrium with metallic iron. The investigation is concentrated in the composition range relevant to the copper smelting slags, i.e., in the fayalite primary phase field close to silica saturation. The experiments were also carried out in the system Al2O3-MgO-“FeO”-CaO-SiO2 in equilibrium with metallic iron to determine the effect of Al2O3 and MgO on the liquidus temperatures of the fayalite slags.
II. EXPERIMENTAL The experimental procedure used in this investigation has been described in detail in another publication[8] and is essentially similar to that previously us
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