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The cooling rate of the liquid oxide can be controlled in industrial sintering processes through the draft pressure and has the potential to influence microstructure formation. The solidification of a liquid within the hematite primary phase field in the ternary "FeO"-CaO-SiO system in air was undertaken at different cooling rates to determine the impact of cooling rate on the formation of product microstructures. Samples with a bulk composition of 72.7 wt% FeO and a CaO/SiO ratio of 3.46, were cooled from 1623 K (1350°C) at 2 K/s, 0.5 K/s, 0.1 K/s and 0.01 K/s and quenched at 5 K temperature intervals from 1533 K (1260°C) to 1453 K (1180°C). During cooling, four stages of phase assemblage formation were consistently observed at all cooling rates; in order of formation these are, Liquid +hematite (I), Liquid+hematite+dicalcium silicate(CS)(II), Liquid+CS+calcium diferrite (CF)(III) and CS+CF+calcium ferrite (CF)(IV). An intergrowth of silico-ferrite of calcium and aluminium-I (SFCA-I) and CaFeFeO was observed to form in some conditions in regions free of hematite, present in liquids solidifying at 0.5 K/s and 0.1 K/s. The sizes and shapes of microstructures were observed to systematically change with cooling rate, with a slower cooling rate typically resulting in coarser coupled microstructures and larger individual crystals. A larger proportion of coupled microstructures are observed at slower cooling rates, this appears to be related to the degree of undercooling prior to the nucleation of new phases. The equilibrium silico-ferrite of calcium (SFC) phase was not observed at any of the cooling rates investigated.

The solidification of "FeO"-CaO-SiO liquids in air at a controlled cooling rate of 2.0 K/s for a range of FeO concentrations in the bulk has been investigated. The compositions investigated were selected such that the bulk compositions were within the hematite primary phase field and had a CaO/SiO ratio of 3.46 wt/wt. Non-equilibrium phase assemblages were formed for all bulk compositions investigated. Specifically, the silico ferrite of calcium (SFC) phase was not formed on cooling. The microstructures and proportions of the phase assemblages formed were found to vary with the FeO concentration in the bulk.

Experimental studies of the CaO-FeO-Fe2O3-SiO2 system in air from 1 200 degrees C to 1 260 degrees C have been carried out in the Fe -rich region with particular focus on the phase equilibria associated with silico-ferrite of calcium (SFC) phase. The measurements have been made possible through the use of a modified experimental technique involving high temperature equilibration and rapid quenching followed by electron probe X-ray microanalysis (EPMA). Isothermal sections for 1 220 degrees C, 1 240 degrees C, 1 255 degrees C and 1 260 degrees C are reported providing information on the limits of stability of the SFC solid solution and the liquidus in the SFC primary phase field for the first time.

Experimental phase equilibria studies have been carried out to investigate the phase chemistry in the CaO "Fe2O3"-SiO2 system related to the iron ore sinter making in 1 atm CO2 at 1 200-1 230 degrees C. The measurements have been performed using a modified experimental technique involving high temperature equilibration and rapid quenching followed by electron probe X-ray microanalysis (EPMA). In contrast to the equilibria in air, the experimental results show that no silico-ferrite of calcium (SFC solid solution) is formed in 1 atm CO2 within the temperature range investigated; that is, the SFC phase is not stable at liquidus temperatures. The liquidus for the iron -rich corner of the CaO "Fe2O3"-SiO2 system in CO2 atmosphere for the spinel (magnetite Fe3O4) and dicalcium silicate (C2S = Ca2SiO4) primary phase fields has been proposed.

A model has been developed that enables the viscosities of the fully liquid slag in the multi-component AlO-CaO-FeO-FeO-MgO-SiO system close to and at metallic iron saturation to be predicted within experimental uncertainties over a wide range of compositions and temperatures based on the Eyring equation to express viscosity. The model links both the activation and pre-exponential energy terms to the slag internal structure through the concentrations of various SiO, Me2/nO and Me 1/nSiO viscous flow structural units, of which the concentrations are derived from a quasi-chemical thermodynamic model of the liquid slag. The model describes a number of slag viscosity features including the chargecompensation effect specific for the AlO-containing systems. The present paper describes application of recent significant improvements in the model formalism to the multi-component system AlO-CaO-FeO- FeO-MgO-SiO, where both Fe and Fe effects on viscosity are individually evaluated. The present model reproduces viscosities of slags equilibrated with metallic iron, which mainly reflects Fe effects on viscosity including the charge compensation effect of the Fe as well as Ca and Mg2+ cations on the formation of tetrahedrally-coordinated Al3+. The model can also reproduce the compositional tendency of viscosity of the SiO-free CaO-FeO-FeO slag in air by incorporating the charge compensation effect of Fe to form tetrahedral coordination by basic cations such as Ca and Fe and to indicate viscosity maximum at an intermediate composition. Further analysis of the behaviour of the Fe cation in the silicate structure to describe corresponding effect on viscosities and to improve viscosity predictions is essential.

A structurally-based quasi-chemical viscosity model has been developed for the Al2O3–CaO–‘FeO’–MgO–SiO2 system. The model links the slag viscosity to the internal structure of melts through the concentrations of various anion/cation Si0.5O, Me2/nn+O and Me1/nn+Si0.25O viscous flow structural units. The concentrations of structural units are derived from the quasi-chemical thermodynamic model.The focus of the present paper is the analysis of experimental data for fully liquid slags in the ‘FeO’–MgO–SiO2, CaO–‘FeO’–MgO–SiO2 and Al2O3–CaO–‘FeO’–MgO–SiO2 systems in equilibrium with metallic iron. Model parameters for the quasi-chemical viscosity model for the system Al2O3–CaO–‘FeO’–MgO–SiO2 are presented. The model has been optimised for the whole composition range at temperatures between 1423 K and 1873 K.

A structurally-based quasi-chemical viscosity model for fully liquid slags in the Al2O3 CaO-'FeO'-MgOSiO2 system has been developed. The focus of the work described in the present paper is the analysis of the experimental data and viscosity models in the quaternary system Al2O3 CaO-MgO-SiO2 and its subsystems. A review of the experimental data, viscometry methods used and viscosity models available in the Al2O3 CaO-MgO-SiO2 and its sub-systems is reported. The quasi-chemical viscosity model is shown to provide good agreement between experimental data and predictions over the whole compositional range.

A structurally-based quasi-chemical viscosity model for fully liquid slags in the Al2O3 CaO-'FeO'-MgO-SiO2 system has been developed. The model links the slag viscosities to the internal structures of the melts through the concentrations of various Si0.5O, Me2/nn+O and Me1/nn+Si0.25O viscous flow structural units. The concentrations of these structural units are derived from a quasi-chemical thermodynamic model of the system. The model described in this series of papers enables the viscosities of liquid slags to be predicted within experimental uncertainties over the whole range of temperatures and compositions in the Al2O3 CaOMgO-SiO2 system.

A structurally-based quasi-chemical viscosity model has been developed for the Al2O3 CaO-'FeO'-MgO-SiO2 system. The model links the slag viscosity to the internal structure of melts through the concentrations of various anion/cation Si0.5O, Me2/nn+O and Me1/nn+Si0.25O viscous flow structural units. The concentrations of structural units are derived from the quasi-chemical thermodynamic model. The focus of the work described in the present paper is the analysis of experimental data and the viscosity models for fully liquid slags in the Al2O3-CaO-MgO, Al2O3 MgO-SiO2 and CaO-MgO-SiO2 systems.

Experimental studies have been carried out to determine the phase equilibria for the ternary MgO-"FeO"-SiO2, in equilibrium with metallic iron. Liquiclus isotherms have been determined in the temperature range from 1 578 to 1 898K in the silica and pyroxene primary phase fields using high temperature equilibration, modified quenching and electron probe X-ray microanalysis (EPMA) techniques.

Liquidus temperatures and phase equilibria have been determined in the olivine primary phase field of the MgO-FeO-SiO2-Al2O3 system. Liquidus isotherms have been determined in the temperature range from 1748 to 1873K. The results are presented in the form of pseudo-ternary sections of the MgO-FeO-SiO2 with 2 and 3wt% Al2O3 in the liquid. The study enables the liquidus to be described for a range of SiO2/MgO ratios. It was found that liquidus temperatures in the olivine primary phase field decrease with the addition of Al2O3.

The effects of alumina and chromite impurities on the liquidus temperatures in the cristobalite/tridymite (SiO2) primary phase fields in the MgO-FeO-SiO, system in equilibrium with metallic iron have been investigated experimentally. Using high temperature equilibration and quenching followed by electron probe X-ray microanalysis (EPMA), liquiclus isotherms have been determined in the temperatures range 1 673 to 1 898 K. The results are presented in the form of pseudo-ternary sections of the MgO-FeO-SiO, system at 2, 3 and 5 wt% Al2O3, 2 wt% Cr2O3, and 2 wt% Cr2O3+2 wt% Al2O3. The study enables the liquidus to be described for a range of SiO2/MgO and MgO/FeO ratios. It was found that liquiclus temperatures in the cristobalite and tridymite primary phase fields, decrease significantly with the addition of Al2O3 and Cr2O3.

Liquidus isotherms and phase equilibria have been determined experimentally for a pseudo-ternary section of the form MnO-(CaO+MgO)-(SiO2+Al2O3) with a fixed Al-2,O-3,/SiO2, weight ratio of 0.17 and MgO/CaO weight ratio of 0.17 for temperatures in the range 1473-1673 K. The primary phase fields present for the section investigated include manganosite (Mn,Mg,Ca)O; dicalcium silicate alpha-2(Ca,Mg,Mn)O (.) SiO2; merwinite 3CaO(.) ((Mg,Mn)O.2SiO(2); wollastonite [(Ca,Mg,Mn)(OSiO2)-Si-.]; ;tephroite [2(Mn,Mg)O.SiO2]; rhodonite [(Mn,Mg)O. diopside [(CaO,MgO,MnO,Al2O3)(SiO2)-Si-.]; tridymite (SiO2), SiO2] and melilite [2CaO (.) (MgO,MnO,Al2O3).2(SiO2,Al2O3)]. The liquidus temperatures relevant to ferro-manganese and silico-manganese smelting slags have been determined. The liquiclus temperature is shown to be principally dependent on the modified basicity weight ratio (CaO+Mgo)/(SiO2+Al2O3) at low MnO concentrations, and dependent on the mole ratio (CaO+ MgO+MnO)/(SiO2+Al2O3) at higher MnO concentrations.

Liquidus isotherms and phase equilibria have been measured in the olivine primary phase field of the MgO-"FeO"-SiO2 system in equilibrium with metallic iron. Liquidus isotherms have been determined in the temperature range from 1523 to 1898 K. The tie lines between liquid and olivine solid solutions have been determined and the results were compared with those obtained in previous studies.