2016 Volume 56 Issue 10 Pages 1728-1737
The “FeO”-containing slags in the low part of blast furnace (BF) are of great importance to the operation of BF, particularly the primary and bosh slags. To optimise the slag components for the smooth operation of BF, the phase equilibria studies have been carried out in the system “FeO”-CaO-SiO2-Al2O3-MgO in equilibrium with metallic iron. High temperature equilibrations followed by quenching were conducted in experiments and electron probe X-ray microanalysis were employed to analyse the samples. For better interpretation and easy implementation of experimental results, the data obtained from measurements were symmetrically analysed and then plotted in the pseudo-ternary phase diagrams of (CaO+SiO2)-Al2O3-MgO with fixed CaO/SiO2 weight ratio of 1.3 and “FeO” of 15 and 20 wt%, respectively. The primary phases such as melilite, Ca2SiO4, merwinite, spinel and (Mg, Fe2+)O were observed with liquid phases and metallic iron in the composition range. The liquidus temperatures increase in melilite and spinel primary phase fields, but decrease in dicalcium silicate and merwinite primary phase fields with increasing Al2O3/(CaO+SiO2) ratio. In addition, the liquidus temperatures firstly increase then decrease with increasing MgO/(CaO+SiO2) ratio in dicalcium silicate and melilite primary phase fields, while they have an increasing trend in merwinite and monoxide primary phase fields. The data resulted from this study provide accurate experimental information that can be used for optimisation of the computed thermodynamic models.
The ironmaking blast furnace (BF) process is the primary technique used to produce the pig iron whilst still being affordable. The fundamental knowledge about the ironmaking BF process is well introduced by Biswas and Geerdes et al.1,2) The increasing demand for the utilization of low-grade iron ores and poor quality of fuels brings on the new challenge of low gas permeability and formations of hearth accretions in modern BF operation. These issues can be overcome by better understanding the properties of the ironmaking BF slags (primary, bosh and final slags) and their variations which may be determined or predicted through systematic and accurate phase equilibria measurements. These slags can be formed by complicated reactions between iron ores with coke/coal and fluxes1,2) in cohesive zone, belly, bosh and hearth of BF. It is relatively easy to determine the chemical compositions of the final slags with plenty of measured data available as most investigations which were related to the BF slags are focused on the final slags in the system CaO-SiO2-Al2O3-MgO. The typical CaO/SiO2 weight ratio of the final slags is between 1.10 and 1.30.3,4,5,6,7) The effect of the basicity in the system of CaO-SiO2-Al2O3-MgO in the steel-making process8,9) and the effect of the basicity and “FeO” in the softening and melting temperature10) were reported previously. However, the slag system containing “FeO” has been not fully understood due to a lack of a systematic investigations about the phase equilibria study of “FeO”-CaO-SiO2-Al2O3-MgO related to BF slags. In fact, for the operation of the ironmaking BF, the primary and bosh slags are generally considered to have more responsibilities than the final slags. It is therefore very important to conduct the systematic and accurate phase equilibria study in order to better understand the chemical compositions and liquidus temperatures of the primary and bosh slags.
Slag Atlas presents the early results of the phase equilibrium.11) The “FeO” containing phase diagrams in equilibrium with metallic iron from binary system “FeO”-SiO2,12) ternary system “FeO”-CaO-SiO2,13,14,15) “FeO”-SiO2-MgO16) and “FeO”-SiO2-Al2O317) to quaternary system CaO-SiO2-Al2O3-“FeO”18,19,20) have been studied. However, only few experimental determinations have done in the system “FeO”-CaO-SiO2-Al2O3-MgO in equilibrium with metallic iron.
In the authors’ previous research, phase equilibria study in the system “FeO”-CaO-SiO2-Al2O3-MgO with CaO/SiO2 ratio of 1.3 and 0, 5 and 10 wt% of “FeO” related to ironmaking BF slags was investigated.6,7) The current work extends the study to the expanded systems with higher “FeO” concentration of 15 and 20 wt%, which are highly related to primary and bosh slags in BF. The properties of such slags with the phase equilibria will be discussed systematically in terms of the chemical compositions and liquidus temperatures associated with pseudo binary and ternary phase diagrams, respectively. Both Fe2+ and Fe3+ are present in the quenched samples, however, only metal cation concentrations can be measured by EPMA. Since the slag was saturated with metallic iron, Fe2+ was dominant in the slag at low oxygen partial pressure. All iron, consequently, was recalculated to “FeO” for presentation purpose only.
The experimental procedure in this investigation has been described in details in a previous paper.7) The samples of the desired compositions were prepared by mixing high-purity chemicals of Fe2O3, Fe, MgO, Al2O3 and the master slag (CaO+SiO2) in agate mortar. Excess Fe powder (20 wt% of the mixture) was added to certify that the slags were always in equilibrium with metallic iron. About 0.3 g of the mixture was collected, pelletized, and then put into an iron envelope made of 0.1 mm pure Fe foil. The iron envelope was then placed in an iron dish to avoid mixture spillage by the wetting flow during the equilibration. The high temperature equilibrium experiments were conducted in a vertical electric resistance furnace at the ultrahigh pure Ar gas environment. This was done for 30 mins pre-melting at 30 K higher than the desired temperature and for 3 to 10 hours melting at the predetermined liquidus temperature. The temperature was monitored using a Pt-30 pct Rh/Pt-6 pct Rh thermocouple. The overall absolute temperature accuracy of the experiments was estimated to be ±3 K. Lastly, the samples were dropped into iced water straight from the hot zone of the furnace for the quenching. The collected specimens were mounted in the epoxy resin and the resin blocks were polished for the sample examinations. The microstructures were examined by scanning electron microscopy coupled with energy-dispersive spectroscopy analysis (SEM-EDS). Compositions of the liquid and solid phases were measured by a JEOL JXA-8200 Electron Probe X-Ray Microanalyser (EPMA) with Wavelength Dispersive Spectrometers (WDS). The EPMA measurement conditions were the same as previous work.7) The EPMA measurements have ±1 wt% accuracy in average.
Over 200 phase equilibria experiments have been carried out in the system “FeO”-(CaO+SiO2)-Al2O3-MgO with CaO/SiO2=1.3 and fixed “FeO” of 15 and 20 wt%, which are directly related to ironmaking BF slags. Figure 2 shows the typical microstructures of the analysed samples. As describe in the previous section, pre-melting was done at 30 K higher than liquidus temperature for 30 mins. During the pre-melting, the samples could be fully melted, then the crystallisation of solid phases was taken place from the fully melted liquid in equilibrium at the desired temperature. The rapid quenching technique can preserve the glass of liquid phase and the primary solid phase. Some dendritic crystals may precipitate in the liquid during the quenching depending on the slag chemistry, so the liquid composition was carefully measured in the outer well-quenched glass region. The liquid phase was in equilibrium with the five different primary solids and metallic iron. The metallic iron is present in all samples, implying that the oxygen partial pressure was controlled by the equilibration with iron. Figure 2(a) shows the equilibration of liquid with melilite and iron. Figure 2(b) presents a typical quenched microstructure of dicalcium silicate primary phase field. Figure 2(c) shows the equilibration of liquid with (Mg,Fe2+)O, spinel and iron. Figure 2(d) reveals that liquid was in equilibrium with merwinite and iron. Tables 1 and 2 show the chemical compositions of the analysed samples with “FeO” concentration in liquid at approximately 15 and 20 wt%, respectively. Melilite is a complex solid solution formed by akermanite (2CaO·MgO·2SiO2), (2CaO·FeO·2SiO2) and gehlenite (2CaO·Al2O3·SiO2) as shown in the tables. The spinel [Al2O3·(Mg,Fe2+)O], merwinite [3CaO·(Mg,Fe2+)O·2SiO2] and monoxide [(Mg,Fe2+)O] were also observed in the investigated composition range. These accurately measured data of the solid solutions can be used invaluably for the optimisation of thermodynamic model.
Pseudo-ternary sections at fixed “FeO” concentrations in the system “FeO”-(CaO+SiO2)-Al2O3-MgO with CaO/SiO2=1.3.
Typical microstructures of the quenched slags from primary phase fields of (a) melilite, (b) Ca2SiO4, (c) (Mg,Fe2+)O and spinel, and (d) merwinite.
| Experiment No. | Temperature (K) | Phase Assemblages | Composition (wt%) | CaO/SiO2 | ||||
|---|---|---|---|---|---|---|---|---|
| CaO | SiO2 | MgO | Al2O3 | FeO | ||||
| Liquid only | ||||||||
| 362 | 1653 | Liquid | 33.6 | 23.6 | 7.5 | 17.7 | 17.5 | 1.42 |
| 364 | 1653 | Liquid | 36.5 | 25.4 | 8.0 | 17.0 | 13.0 | 1.43 |
| 367 | 1653 | Liquid | 35.6 | 24.9 | 6.6 | 15.5 | 17.4 | 1.43 |
| 77 | 1673 | Liquid | 34.8 | 27.3 | 5.9 | 16.1 | 15.3 | 1.27 |
| 78 | 1673 | Liquid | 33.3 | 25.1 | 6.3 | 17.7 | 17.3 | 1.33 |
| 129 | 1673 | Liquid | 36.5 | 27.6 | 5.2 | 13.0 | 17.5 | 1.32 |
| 134 | 1673 | Liquid | 35.0 | 27.2 | 6.4 | 18.0 | 13.5 | 1.29 |
| 170 | 1673 | Liquid | 34.2 | 26.7 | 7.7 | 16.7 | 14.2 | 1.28 |
| 171 | 1673 | Liquid | 40.0 | 31.3 | 0.1 | 12.9 | 15.3 | 1.28 |
| 172 | 1673 | Liquid | 39.1 | 30.6 | 0.0 | 13.5 | 16.5 | 1.28 |
| 175 | 1673 | Liquid | 38.6 | 30.1 | 3.6 | 13.3 | 14.1 | 1.28 |
| 177 | 1673 | Liquid | 37.0 | 28.9 | 5.2 | 13.3 | 15.4 | 1.28 |
| 187 | 1673 | Liquid | 37.9 | 29.0 | 6.2 | 13.4 | 13.5 | 1.31 |
| 189 | 1673 | Liquid | 38.0 | 28.8 | 5.6 | 13.2 | 14.4 | 1.32 |
| 369 | 1673 | Liquid | 35.4 | 24.6 | 9.0 | 13.7 | 17.4 | 1.44 |
| 396 | 1673 | Liquid | 38.8 | 28.5 | 6.8 | 9.3 | 16.5 | 1.36 |
| 417 | 1673 | Liquid | 34.0 | 26.8 | 8.0 | 17.0 | 14.2 | 1.27 |
| 418 | 1673 | Liquid | 33.8 | 26.9 | 9.1 | 15.6 | 14.7 | 1.26 |
| 212 | 1703 | Liquid | 39.4 | 30.3 | 0.0 | 14.9 | 15.3 | 1.30 |
| 385 | 1703 | Liquid | 34.8 | 27.0 | 8.4 | 12.6 | 17.1 | 1.29 |
| 386 | 1703 | Liquid | 33.8 | 26.0 | 9.4 | 16.7 | 14.0 | 1.30 |
| 422 | 1703 | Liquid | 34.3 | 26.0 | 9.0 | 18.0 | 12.7 | 1.32 |
| 439 | 1703 | Liquid | 34.5 | 25.8 | 6.7 | 15.3 | 17.5 | 1.34 |
| 440 | 1703 | Liquid | 32.7 | 24.2 | 8.1 | 18.2 | 16.6 | 1.35 |
| 509 | 1703 | Liquid | 35.0 | 27.5 | 10.4 | 12.4 | 14.7 | 1.27 |
| 510 | 1703 | Liquid | 33.6 | 26.1 | 11.0 | 14.1 | 15.1 | 1.29 |
| 513 | 1703 | Liquid | 34.1 | 26.3 | 10.5 | 16.0 | 13.1 | 1.30 |
| 43 | 1723 | Liquid | 32.9 | 25.1 | 11.5 | 16.3 | 13.7 | 1.31 |
| 62 | 1723 | Liquid | 32.4 | 25.3 | 7.7 | 18.1 | 16.1 | 1.28 |
| 67 | 1723 | Liquid | 33.8 | 26.1 | 10.2 | 16.5 | 13.1 | 1.29 |
| 68 | 1723 | Liquid | 32.1 | 24.7 | 9.9 | 16.4 | 16.4 | 1.30 |
| 117 | 1723 | Liquid | 32.3 | 24.4 | 7.0 | 21.5 | 14.8 | 1.32 |
| 288 | 1723 | Liquid | 36.0 | 27.3 | 4.5 | 16.7 | 15.5 | 1.32 |
| 390 | 1723 | Liquid | 32.1 | 24.8 | 9.1 | 18.9 | 15.1 | 1.29 |
| 430 | 1723 | Liquid | 31.8 | 24.2 | 8.4 | 17.7 | 17.8 | 1.31 |
| 453 | 1723 | Liquid | 33.1 | 26.0 | 12.3 | 15.1 | 13.5 | 1.28 |
| Liquid with one solid phase | ||||||||
| Melilite primary phase field | ||||||||
| 545 | 1623 | Liquid | 37.1 | 27.4 | 5.7 | 13.3 | 16.5 | 1.35 |
| Melilite | 40.8 | 25.6 | 2.1 | 30.3 | 1.2 | |||
| 365 | 1653 | Liquid | 38.0 | 26.5 | 4.8 | 15.3 | 15.4 | 1.43 |
| Melilite | 41.1 | 24.3 | 2.0 | 31.5 | 1.1 | |||
| 517 | 1653 | Liquid | 39.9 | 30.5 | 2.1 | 13.0 | 14.6 | 1.31 |
| Melilite | 41.0 | 24.3 | 1.2 | 32.0 | 1.5 | |||
| 518 | 1653 | Liquid | 39.8 | 30.0 | 4.6 | 13.2 | 12.4 | 1.33 |
| Melilite | 41.2 | 25.4 | 2.1 | 30.3 | 1.1 | |||
| 525 | 1653 | Liquid | 38.8 | 30.4 | 0.1 | 13.6 | 17.0 | 1.28 |
| Melilite | 40.9 | 23.2 | 0.1 | 33.8 | 2.0 | |||
| 527 | 1653 | Liquid | 38.1 | 31.0 | 2.4 | 13.7 | 14.8 | 1.23 |
| Melilite | 40.9 | 24.5 | 1.3 | 32.0 | 1.3 | |||
| 528 | 1653 | Liquid | 36.2 | 28.6 | 5.0 | 14.8 | 15.4 | 1.27 |
| Melilite | 40.9 | 26.1 | 2.4 | 29.5 | 1.1 | |||
| 29 | 1673 | Liquid | 37.9 | 31.3 | 3.4 | 14.4 | 13.0 | 1.21 |
| Melilite | 40.3 | 25.5 | 1.8 | 31.2 | 1.2 | |||
| 133 | 1673 | Liquid | 35.7 | 27.8 | 5.9 | 16.9 | 13.7 | 1.28 |
| Melilite | 40.8 | 25.2 | 2.0 | 31.0 | 1.0 | |||
| 158 | 1673 | Liquid | 34.5 | 26.8 | 4.5 | 17.8 | 15.9 | 1.29 |
| Melilite | 40.0 | 24.3 | 1.4 | 33.2 | 1.1 | |||
| 159 | 1673 | Liquid | 33.5 | 26.3 | 5.2 | 19.0 | 15.8 | 1.28 |
| Melilite | 39.9 | 24.3 | 1.4 | 33.2 | 1.1 | |||
| 160 | 1673 | Liquid | 32.6 | 24.7 | 3.9 | 20.0 | 18.4 | 1.32 |
| Melilite | 40.2 | 24.0 | 1.2 | 33.3 | 1.2 | |||
| 162 | 1673 | Liquid | 40.1 | 31.1 | 0.0 | 15.0 | 13.5 | 1.29 |
| Melilite | 40.0 | 23.1 | 0.1 | 34.9 | 1.9 | |||
| 182 | 1673 | Liquid | 38.2 | 28.8 | 4.0 | 15.3 | 13.3 | 1.32 |
| Melilite | 41.4 | 24.8 | 1.8 | 30.9 | 1.1 | |||
| 207 | 1673 | Liquid | 33.3 | 27.6 | 5.6 | 18.5 | 15.0 | 1.20 |
| Melilite | 39.5 | 26.0 | 2.1 | 31.5 | 0.9 | |||
| 259 | 1673 | Liquid | 34.1 | 30.2 | 5.0 | 17.1 | 13.7 | 1.13 |
| Melilite | 37.8 | 27.0 | 2.2 | 32.0 | 1.0 | |||
| 260 | 1673 | Liquid | 34.5 | 31.3 | 2.0 | 16.3 | 15.8 | 1.10 |
| Melilite | 37.5 | 25.9 | 1.2 | 33.9 | 1.5 | |||
| 262 | 1673 | Liquid | 35.9 | 27.9 | 6.3 | 16.6 | 13.2 | 1.29 |
| Melilite | 41.5 | 25.3 | 2.2 | 30.4 | 0.6 | |||
| 348 | 1673 | Liquid | 34.2 | 27.5 | 3.1 | 18.1 | 17.2 | 1.24 |
| Melilite | 40.8 | 24.1 | 1.0 | 32.9 | 1.2 | |||
| 205 | 1703 | Liquid | 35.8 | 29.0 | 0.0 | 18.7 | 16.5 | 1.23 |
| Melilite | 39.6 | 23.1 | 0.0 | 36.2 | 1.1 | |||
| 217 | 1703 | Liquid | 36.1 | 27.2 | 0.0 | 18.9 | 17.8 | 1.33 |
| Melilite | 41.6 | 22.5 | 0.0 | 34.4 | 1.5 | |||
| 228 | 1703 | Liquid | 38.7 | 28.6 | 0.1 | 17.4 | 15.3 | 1.35 |
| Melilite | 41.3 | 22.4 | 0.0 | 34.9 | 1.3 | |||
| 229 | 1703 | Liquid | 36.3 | 29.8 | 0.0 | 18.9 | 15.0 | 1.22 |
| Melilite | 41.0 | 22.8 | 0.0 | 34.9 | 1.3 | |||
| 341 | 1703 | Liquid | 37.0 | 29.7 | 1.9 | 18.2 | 13.2 | 1.24 |
| Melilite | 40.8 | 23.8 | 0.9 | 33.5 | 1.0 | |||
| 86 | 1723 | Liquid | 37.2 | 24.5 | 3.2 | 21.4 | 13.7 | 1.52 |
| Melilite | 41.0 | 23.2 | 0.8 | 34.3 | 0.7 | |||
| 121 | 1723 | Liquid | 33.6 | 25.4 | 0.0 | 23.9 | 17.0 | 1.33 |
| Melilite | 41.3 | 22.1 | 0.0 | 35.5 | 1.1 | |||
| 276 | 1723 | Liquid | 34.1 | 29.2 | 0.0 | 21.7 | 15.0 | 1.17 |
| Melilite | 38.7 | 23.9 | 0.0 | 36.1 | 1.3 | |||
| 277 | 1723 | Liquid | 30.9 | 28.1 | 0.1 | 25.8 | 15.1 | 1.10 |
| Melilite | 38.8 | 23.6 | 0.0 | 36.5 | 1.1 | |||
| Spinel primary phase field | ||||||||
| 80 | 1673 | Liquid | 34.3 | 26.0 | 9.5 | 16.5 | 13.4 | 1.32 |
| Spinel | 0.1 | 0.2 | 25.4 | 69.1 | 5.1 | |||
| 339 | 1703 | Liquid | 30.4 | 25.0 | 5.4 | 22.1 | 17.0 | 1.22 |
| Spinel | 0.1 | 0.0 | 22.3 | 68.0 | 9.5 | |||
| 420 | 1703 | Liquid | 32.4 | 24.5 | 9.1 | 18.2 | 15.8 | 1.32 |
| Spinel | 0.1 | 0.0 | 26.6 | 70.1 | 3.2 | |||
| 506 | 1703 | Liquid | 32.6 | 25.5 | 11.2 | 16.7 | 14.0 | 1.28 |
| Spinel | 0.2 | 0.1 | 26.9 | 70.0 | 2.8 | |||
| 92 | 1723 | Liquid | 29.9 | 21.6 | 4.8 | 25.1 | 18.6 | 1.38 |
| Spinel | 0.1 | 0.1 | 20.8 | 67.0 | 12.0 | |||
| 115 | 1723 | Liquid | 30.5 | 23.3 | 5.4 | 23.7 | 17.0 | 1.31 |
| Spinel | 0.1 | 0.0 | 21.5 | 67.7 | 10.6 | |||
| 284 | 1723 | Liquid | 30.8 | 26.0 | 7.9 | 20.8 | 14.5 | 1.19 |
| Spinel | 0.0 | 0.0 | 24.4 | 68.5 | 7.0 | |||
| 293 | 1723 | Liquid | 31.1 | 23.2 | 4.5 | 26.3 | 14.9 | 1.34 |
| Spinel | 0.7 | 0.4 | 20.0 | 66.7 | 12.2 | |||
| 294 | 1723 | Liquid | 30.7 | 23.1 | 4.2 | 26.5 | 15.4 | 1.33 |
| Spinel | 0.3 | 0.0 | 19.8 | 67.1 | 12.8 | |||
| 425 | 1723 | Liquid | 32.0 | 24.7 | 7.0 | 21.9 | 14.4 | 1.30 |
| Spinel | 0.2 | 0.0 | 24.3 | 68.6 | 6.9 | |||
| 426 | 1723 | Liquid | 32.0 | 24.0 | 6.2 | 23.2 | 14.6 | 1.33 |
| Spinel | 1.3 | 1.1 | 23.4 | 67.3 | 7.0 | |||
| 448 | 1723 | Liquid | 31.1 | 23.8 | 10.0 | 18.3 | 16.7 | 1.31 |
| Spinel | 3.3 | 2.9 | 24.3 | 62.4 | 7.0 | |||
| Ca2SiO4 primary phase field | ||||||||
| 531 | 1653 | Liquid | 41.7 | 32.2 | 1.8 | 10.1 | 14.1 | 1.30 |
| Ca2SiO4 | 60.6 | 34.6 | 0.7 | 0.3 | 3.8 | |||
| 472 | 1673 | Liquid | 39.3 | 30.1 | 4.6 | 9.8 | 16.3 | 1.30 |
| Ca2SiO4 | 60.2 | 34.4 | 1.7 | 0.2 | 3.6 | |||
| 573 | 1673 | Liquid | 40.4 | 30.0 | 2.4 | 10.5 | 16.6 | 1.35 |
| Ca2SiO4 | 60.6 | 34.9 | 1.0 | 0.2 | 3.3 | |||
| 463 | 1703 | Liquid | 42.2 | 33.6 | 0.2 | 8.8 | 15.2 | 1.26 |
| Ca2SiO4 | 61.2 | 34.5 | 0.1 | 0.2 | 3.8 | |||
| 464 | 1703 | Liquid | 38.4 | 29.4 | 6.4 | 9.0 | 16.8 | 1.31 |
| Ca2SiO4 | 59.1 | 35.0 | 2.4 | 0.2 | 3.3 | |||
| 566 | 1703 | Liquid | 40.5 | 29.4 | 4.7 | 9.8 | 15.7 | 1.38 |
| Ca2SiO4 | 60.8 | 33.9 | 1.8 | 0.2 | 3.3 | |||
| 409 | 1723 | Liquid | 43.7 | 34.7 | 0.1 | 7.4 | 14.1 | 1.26 |
| Ca2SiO4 | 60.5 | 34.8 | 0.1 | 0.3 | 4.3 | |||
| 410 | 1723 | Liquid | 43.2 | 34.2 | 0.1 | 7.2 | 15.3 | 1.26 |
| Ca2SiO4 | 60.6 | 34.8 | 0.0 | 0.2 | 4.3 | |||
| 413 | 1723 | Liquid | 41.8 | 32.6 | 4.4 | 7.8 | 13.4 | 1.28 |
| Ca2SiO4 | 60.2 | 34.8 | 1.7 | 0.2 | 3.1 | |||
| 414 | 1723 | Liquid | 41.5 | 32.1 | 4.6 | 7.7 | 14.1 | 1.29 |
| Ca2SiO4 | 60.1 | 35.0 | 1.7 | 0.1 | 3.1 | |||
| 415 | 1723 | Liquid | 42.2 | 31.3 | 2.3 | 7.4 | 16.7 | 1.35 |
| Ca2SiO4 | 60.32 | 34.78 | 0.89 | 0.16 | 3.85 | |||
| Merwinite primary phase field | ||||||||
| 543 | 1653 | Liquid | 37.7 | 30.0 | 7.2 | 10.3 | 14.8 | 1.25 |
| Merwinite | 50.5 | 36.2 | 11.0 | 0.1 | 2.2 | |||
| 544 | 1653 | Liquid | 37.6 | 29.7 | 7.7 | 10.8 | 14.3 | 1.27 |
| Merwinite | 50.7 | 36.1 | 11.1 | 0.1 | 2.0 | |||
| (Mg, Fe2+)O primary phase field | ||||||||
| 372 | 1703 | Liquid | 35.0 | 24.3 | 10.3 | 14.1 | 16.4 | 1.44 |
| (Mg, Fe2+)O | 0.3 | 0.0 | 64.0 | 0.8 | 34.8 | |||
| 373 | 1703 | Liquid | 33.9 | 23.7 | 10.3 | 15.2 | 16.9 | 1.43 |
| (Mg, Fe2+)O | 0.4 | 0.0 | 62.9 | 0.9 | 35.7 | |||
| 438 | 1703 | Liquid | 34.5 | 26.1 | 11.9 | 14.3 | 13.2 | 1.32 |
| (Mg, Fe2+)O | 0.3 | 0.0 | 70.1 | 0.9 | 28.7 | |||
| 375 | 1723 | Liquid | 32.4 | 23.1 | 10.5 | 16.6 | 17.4 | 1.40 |
| (Mg, Fe2+)O | 0.3 | 0.0 | 62.6 | 1.1 | 36.0 | |||
| 377 | 1723 | Liquid | 34.2 | 24.7 | 11.4 | 15.8 | 14.0 | 1.39 |
| (Mg, Fe2+)O | 0.3 | 0.0 | 70.4 | 1.0 | 28.4 | |||
| 378 | 1723 | Liquid | 33.0 | 23.8 | 11.4 | 17.9 | 13.8 | 1.39 |
| (Mg, Fe2+)O | 0.3 | 0.0 | 70.7 | 1.2 | 27.8 | |||
| 380 | 1723 | Liquid | 34.5 | 25.0 | 10.0 | 15.5 | 15.1 | 1.38 |
| (Mg, Fe2+)O | 0.3 | 0.0 | 64.8 | 0.9 | 34.1 | |||
| 441 | 1723 | Liquid | 34.1 | 26.4 | 11.1 | 11.3 | 16.8 | 1.29 |
| (Mg, Fe2+)O | 0.3 | 0.0 | 62.3 | 0.8 | 36.1 | |||
| Liquid with more solid phases | ||||||||
| 526 | 1653 | Liquid | 33.7 | 26.3 | 6.6 | 18.0 | 15.4 | 1.28 |
| Melilite | 41.1 | 24.9 | 2.0 | 31.0 | 1.0 | |||
| Spinel | 0.2 | 0.0 | 23.5 | 67.5 | 8.7 | |||
| 538 | 1653 | Liquid | 33.5 | 26.8 | 6.6 | 17.9 | 15.2 | 1.25 |
| Melilite | 40.6 | 25.2 | 2.0 | 31.2 | 0.9 | |||
| Spinel | 0.2 | 0.0 | 23.8 | 68.2 | 7.9 | |||
| 210 | 1703 | Liquid | 31.0 | 25.7 | 5.6 | 23.8 | 14.0 | 1.21 |
| Melilite | 39.0 | 24.8 | 1.5 | 33.9 | 0.7 | |||
| Spinel | 0.2 | 0.0 | 25.1 | 68.4 | 6.3 | |||
| 238 | 1703 | Liquid | 29.7 | 23.5 | 2.8 | 27.5 | 16.5 | 1.26 |
| Melilite | 41.2 | 22.9 | 0.5 | 34.8 | 0.6 | |||
| Spinel | 0.1 | 0.0 | 17.9 | 66.2 | 15.9 | |||
| 239 | 1703 | Liquid | 29.5 | 23.7 | 2.8 | 27.9 | 16.1 | 1.24 |
| Melilite | 41.0 | 22.9 | 0.5 | 34.8 | 0.8 | |||
| Spinel | 0.2 | 0.0 | 16.8 | 65.7 | 17.3 | |||
| 554 | 1623 | Liquid | 38.0 | 26.3 | 5.8 | 14.4 | 15.6 | 1.44 |
| Melilite | 40.7 | 25.7 | 2.2 | 30.3 | 1.1 | |||
| Merwinite | 50.6 | 36.4 | 10.8 | 0.1 | 2.1 | |||
| 395 | 1673 | Liquid | 39.8 | 29.5 | 6.9 | 9.3 | 14.4 | 1.35 |
| Ca2SiO4 | 59.7 | 33.8 | 3.0 | 0.2 | 3.3 | |||
| Merwinite | 52.3 | 34.5 | 11.2 | 0.1 | 1.8 | |||
| 460 | 1673 | Liquid | 38.3 | 29.7 | 6.6 | 9.8 | 15.6 | 1.29 |
| Ca2SiO4 | 58.6 | 35.3 | 2.7 | 0.2 | 3.1 | |||
| Merwinite | 51.2 | 35.7 | 11.3 | 0.1 | 1.8 | |||
| 435 | 1703 | Liquid | 37.3 | 27.0 | 9.1 | 9.3 | 17.3 | 1.38 |
| Ca2SiO4 | 59.8 | 34.3 | 3.1 | 0.1 | 2.7 | |||
| Merwinite | 51.1 | 35.9 | 11.7 | 0.1 | 1.2 | |||
| 462 | 1703 | Liquid | 38.2 | 29.5 | 8.4 | 8.3 | 15.6 | 1.30 |
| Ca2SiO4 | 59.2 | 35.0 | 3.3 | 0.1 | 2.4 | |||
| Merwinite | 50.8 | 36.1 | 12.0 | 0.1 | 1.1 | |||
| 54 | 1673 | Liquid | 33.2 | 24.7 | 10.3 | 15.8 | 15.5 | 1.34 |
| Spinel | 0.5 | 0.3 | 25.3 | 68.1 | 5.6 | |||
| (Mg, Fe2+)O | 0.3 | 0.0 | 62.9 | 0.9 | 35.1 | |||
| 370 | 1673 | Liquid | 33.9 | 23.5 | 10.1 | 16.4 | 16.1 | 1.44 |
| Spinel | 0.2 | 0.0 | 25.7 | 68.1 | 5.9 | |||
| (Mg, Fe2+)O | 0.3 | 0.0 | 62.0 | 1.0 | 36.7 | |||
| 428 | 1723 | Liquid | 31.6 | 24.5 | 12.9 | 17.5 | 13.5 | 1.29 |
| Spinel | 0.3 | 0.1 | 26.7 | 69.9 | 2.9 | |||
| (Mg, Fe2+)O | 0.3 | 0.1 | 72.3 | 1.2 | 26.2 | |||
| 553 | 1623 | Liquid | 38.0 | 26.3 | 5.7 | 14.1 | 15.9 | 1.44 |
| Melilite | 41.0 | 25.8 | 2.0 | 30.1 | 1.2 | |||
| Ca2SiO4 | 57.3 | 35.5 | 5.1 | 0.1 | 2.1 | |||
| Merwinite | 50.7 | 36.2 | 10.9 | 0.1 | 2.1 | |||
| Experiment No. | Temperature (K) | Phase Assemblages | Composition (wt%) | CaO/SiO2 | ||||
|---|---|---|---|---|---|---|---|---|
| CaO | SiO2 | MgO | Al2O3 | FeO | ||||
| Liquid only | ||||||||
| 362 | 1653 | Liquid | 33.6 | 23.6 | 7.5 | 17.7 | 17.5 | 1.42 |
| 366 | 1653 | Liquid | 38.8 | 27.0 | 2.8 | 12.6 | 18.7 | 1.44 |
| 535 | 1653 | Liquid | 34.9 | 27.7 | 0.0 | 13.9 | 23.4 | 1.26 |
| 539 | 1653 | Liquid | 35.8 | 27.9 | 3.6 | 8.3 | 24.3 | 1.28 |
| 541 | 1653 | Liquid | 38.1 | 30.0 | 0.1 | 8.6 | 23.2 | 1.27 |
| 542 | 1653 | Liquid | 37.4 | 29.4 | 3.2 | 8.4 | 21.6 | 1.27 |
| 17 | 1673 | Liquid | 37.2 | 28.2 | 2.4 | 11.6 | 20.2 | 1.32 |
| 34 | 1673 | Liquid | 32.8 | 25.2 | 5.5 | 14.8 | 21.7 | 1.30 |
| 74 | 1673 | Liquid | 35.4 | 27.8 | 2.9 | 15.5 | 18.0 | 1.27 |
| 123 | 1673 | Liquid | 36.5 | 27.5 | 0.1 | 13.9 | 21.8 | 1.33 |
| 131 | 1673 | Liquid | 34.0 | 26.2 | 5.9 | 14.2 | 19.4 | 1.30 |
| 132 | 1673 | Liquid | 33.2 | 25.6 | 5.8 | 15.3 | 20.0 | 1.30 |
| 168 | 1673 | Liquid | 33.5 | 26.4 | 5.4 | 16.3 | 18.2 | 1.27 |
| 383 | 1673 | Liquid | 30.5 | 23.5 | 8.5 | 17.0 | 20.6 | 1.30 |
| 384 | 1673 | Liquid | 31.5 | 24.3 | 7.2 | 17.5 | 19.4 | 1.30 |
| 394 | 1673 | Liquid | 40.0 | 31.3 | 0.2 | 9.6 | 18.9 | 1.28 |
| 397 | 1673 | Liquid | 38.5 | 28.1 | 4.3 | 9.2 | 19.7 | 1.37 |
| 398 | 1673 | Liquid | 38.7 | 28.3 | 4.7 | 10.1 | 18.0 | 1.37 |
| 352 | 1703 | Liquid | 33.0 | 23.7 | 1.8 | 22.0 | 19.5 | 1.39 |
| 385 | 1703 | Liquid | 34.8 | 27.0 | 8.4 | 12.6 | 17.1 | 1.29 |
| 439 | 1703 | Liquid | 34.5 | 25.8 | 6.7 | 15.3 | 17.5 | 1.34 |
| 42 | 1723 | Liquid | 32.2 | 24.3 | 10.5 | 13.9 | 18.7 | 1.32 |
| 61 | 1723 | Liquid | 31.9 | 24.4 | 6.2 | 18.4 | 18.8 | 1.30 |
| 63 | 1723 | Liquid | 30.7 | 23.8 | 7.4 | 17.8 | 20.0 | 1.29 |
| 69 | 1723 | Liquid | 29.8 | 23.1 | 10.3 | 16.1 | 20.3 | 1.29 |
| 111 | 1723 | Liquid | 28.9 | 22.2 | 4.7 | 23.6 | 20.6 | 1.30 |
| 114 | 1723 | Liquid | 30.8 | 23.5 | 5.4 | 22.0 | 18.2 | 1.31 |
| 421 | 1723 | Liquid | 30.3 | 23.6 | 8.1 | 16.3 | 21.7 | 1.29 |
| 430 | 1723 | Liquid | 31.8 | 24.2 | 8.4 | 17.7 | 17.8 | 1.31 |
| 431 | 1723 | Liquid | 30.4 | 23.9 | 8.1 | 16.3 | 21.4 | 1.27 |
| 445 | 1723 | Liquid | 36.3 | 26.5 | 2.7 | 15.5 | 18.8 | 1.37 |
| 487 | 1723 | Liquid | 39.7 | 31.0 | 0.1 | 8.3 | 20.7 | 1.28 |
| 494 | 1723 | Liquid | 32.4 | 25.8 | 10.4 | 10.9 | 20.3 | 1.25 |
| 495 | 1723 | Liquid | 33.4 | 26.2 | 9.4 | 8.7 | 22.1 | 1.28 |
| 500 | 1723 | Liquid | 29.0 | 22.3 | 11.2 | 15.6 | 21.8 | 1.30 |
| Liquid with one solid phase | ||||||||
| Melilite primary phase field | ||||||||
| 135 | 1623 | Liquid | 32.3 | 25.0 | 5.7 | 14.5 | 22.5 | 1.29 |
| Melilite | 40.9 | 24.8 | 2.1 | 30.7 | 1.6 | |||
| 546 | 1623 | Liquid | 38.8 | 31.3 | 0.1 | 11.8 | 18.0 | 1.24 |
| Melilite | 40.5 | 23.8 | 0.1 | 33.0 | 2.6 | |||
| 359 | 1653 | Liquid | 39.1 | 27.5 | 0.1 | 13.8 | 19.5 | 1.42 |
| Melilite | 41.0 | 21.7 | 0.0 | 35.4 | 1.9 | |||
| 361 | 1653 | Liquid | 33.6 | 23.3 | 2.7 | 17.3 | 23.0 | 1.44 |
| Melilite | 40.9 | 23.1 | 1.0 | 33.7 | 1.4 | |||
| 537 | 1653 | Liquid | 35.1 | 28.1 | 2.1 | 15.4 | 19.3 | 1.25 |
| Melilite | 40.6 | 24.6 | 1.2 | 32.0 | 1.6 | |||
| 25 | 1673 | Liquid | 34.5 | 26.4 | 0.0 | 16.5 | 22.5 | 1.31 |
| Melilite | 40.2 | 22.8 | 0.0 | 35.1 | 1.9 | |||
| 125 | 1673 | Liquid | 36.8 | 28.0 | 0.1 | 15.5 | 19.5 | 1.31 |
| Melilite | 41.4 | 22.7 | 0.0 | 34.0 | 1.9 | |||
| 126 | 1673 | Liquid | 35.9 | 27.7 | 0.1 | 16.1 | 19.9 | 1.29 |
| Melilite | 41.3 | 22.9 | 0.1 | 33.5 | 2.2 | |||
| 149 | 1673 | Liquid | 30.8 | 22.8 | 2.2 | 21.2 | 22.8 | 1.35 |
| Melilite | 41.4 | 22.4 | 0.7 | 33.9 | 1.5 | |||
| 150 | 1673 | Liquid | 30.9 | 23.2 | 3.1 | 21.2 | 21.4 | 1.33 |
| Melilite | 41.5 | 22.9 | 0.8 | 33.6 | 1.1 | |||
| 151 | 1673 | Liquid | 29.1 | 22.4 | 2.6 | 22.5 | 23.2 | 1.30 |
| Melilite | 39.9 | 23.1 | 0.7 | 34.9 | 1.4 | |||
| 156 | 1673 | Liquid | 33.0 | 25.9 | 2.8 | 18.3 | 19.7 | 1.27 |
| Melilite | 40.4 | 23.8 | 1.1 | 33.3 | 1.4 | |||
| 157 | 1673 | Liquid | 32.5 | 26.1 | 3.1 | 18.9 | 19.0 | 1.25 |
| Melilite | 40.8 | 24.0 | 1.1 | 32.7 | 1.3 | |||
| 160 | 1673 | Liquid | 32.6 | 24.7 | 3.9 | 20.0 | 18.4 | 1.32 |
| Melilite | 40.2 | 24.0 | 1.2 | 33.3 | 1.2 | |||
| 349 | 1673 | Liquid | 35.0 | 27.4 | 2.0 | 17.2 | 18.4 | 1.28 |
| Melilite | 40.8 | 24.0 | 0.9 | 32.8 | 1.4 | |||
| 217 | 1703 | Liquid | 36.1 | 27.2 | 0.0 | 18.9 | 17.8 | 1.33 |
| Melilite | 41.6 | 22.5 | 0.0 | 34.4 | 1.5 | |||
| 121 | 1723 | Liquid | 33.6 | 25.4 | 0.0 | 23.9 | 17.0 | 1.33 |
| Melilite | 41.3 | 22.1 | 0.0 | 35.5 | 1.1 | |||
| Spinel primary phase field | ||||||||
| 139 | 1623 | Liquid | 32.3 | 24.1 | 7.4 | 14.0 | 22.2 | 1.34 |
| Spinel | 0.2 | 0.0 | 23.4 | 67.3 | 9.1 | |||
| 140 | 1623 | Liquid | 33.1 | 24.3 | 7.7 | 14.3 | 20.5 | 1.36 |
| Spinel | 0.1 | 0.1 | 23.2 | 67.3 | 9.3 | |||
| 536 | 1653 | Liquid | 31.4 | 24.7 | 5.8 | 17.5 | 20.6 | 1.27 |
| Spinel | 0.3 | 0.0 | 22.5 | 66.8 | 10.4 | |||
| 39 | 1673 | Liquid | 30.6 | 23.6 | 9.6 | 16.2 | 20.0 | 1.29 |
| Spinel | 0.2 | 0.0 | 25.0 | 68.5 | 6.3 | |||
| 257 | 1673 | Liquid | 30.4 | 23.2 | 4.3 | 21.0 | 21.1 | 1.31 |
| Spinel | 0.1 | 0.1 | 20.2 | 66.7 | 12.9 | |||
| 248 | 1703 | Liquid | 30.3 | 24.4 | 6.6 | 20.1 | 18.6 | 1.24 |
| Spinel | 0.3 | 0.2 | 23.1 | 67.0 | 9.4 | |||
| 387 | 1703 | Liquid | 28.7 | 22.1 | 8.1 | 17.7 | 23.3 | 1.30 |
| Spinel | 0.2 | 0.0 | 23.7 | 67.3 | 8.7 | |||
| 92 | 1723 | Liquid | 29.9 | 21.6 | 4.8 | 25.1 | 18.6 | 1.38 |
| Spinel | 0.1 | 0.1 | 20.8 | 67.0 | 12.0 | |||
| 96 | 1723 | Liquid | 27.8 | 18.2 | 5.5 | 22.8 | 25.8 | 1.53 |
| Spinel | 0.1 | 0.0 | 21.0 | 66.6 | 12.2 | |||
| 112 | 1723 | Liquid | 26.4 | 20.2 | 4.3 | 23.3 | 25.8 | 1.31 |
| Spinel | 0.3 | 0.2 | 17.8 | 65.0 | 16.7 | |||
| 285 | 1723 | Liquid | 26.7 | 22.2 | 7.5 | 19.5 | 24.1 | 1.20 |
| Spinel | 0.0 | 0.0 | 22.7 | 66.8 | 10.5 | |||
| 286 | 1723 | Liquid | 26.8 | 22.7 | 7.5 | 19.6 | 23.4 | 1.18 |
| Spinel | 0.0 | 0.1 | 22.7 | 67.5 | 9.8 | |||
| 432 | 1723 | Liquid | 29.1 | 22.1 | 10.5 | 18.3 | 20.0 | 1.32 |
| Spinel | 0.2 | 0.0 | 25.5 | 69.2 | 5.1 | |||
| Ca2SiO4 primary phase field | ||||||||
| 550 | 1623 | Liquid | 36.0 | 25.4 | 5.1 | 9.6 | 23.9 | 1.42 |
| Ca2SiO4 | 59.5 | 35.0 | 2.1 | 0.1 | 3.2 | |||
| 551 | 1623 | Liquid | 37.2 | 26.8 | 2.4 | 11.2 | 22.4 | 1.39 |
| Ca2SiO4 | 60.2 | 34.8 | 1.0 | 0.2 | 3.9 | |||
| 552 | 1623 | Liquid | 35.8 | 25.7 | 3.1 | 9.7 | 25.7 | 1.39 |
| Ca2SiO4 | 59.3 | 35.2 | 1.3 | 0.2 | 4.0 | |||
| 530 | 1653 | Liquid | 38.7 | 28.4 | 4.8 | 8.1 | 20.0 | 1.36 |
| Ca2SiO4 | 59.8 | 34.8 | 1.9 | 0.2 | 3.4 | |||
| 555 | 1653 | Liquid | 39.8 | 28.5 | 0.2 | 11.0 | 20.5 | 1.40 |
| Ca2SiO4 | 61.6 | 33.8 | 0.1 | 0.2 | 4.3 | |||
| 567 | 1653 | Liquid | 40.3 | 29.5 | 0.1 | 11.6 | 18.6 | 1.37 |
| Ca2SiO4 | 60.3 | 34.9 | 0.1 | 0.2 | 4.5 | |||
| 568 | 1653 | Liquid | 36.4 | 25.6 | 5.9 | 8.7 | 23.4 | 1.42 |
| Ca2SiO4 | 60.0 | 34.7 | 2.2 | 0.1 | 3.0 | |||
| 569 | 1653 | Liquid | 38.7 | 27.7 | 4.0 | 10.6 | 19.0 | 1.39 |
| Ca2SiO4 | 60.3 | 34.7 | 1.6 | 0.2 | 3.3 | |||
| 570 | 1653 | Liquid | 39.7 | 28.7 | 2.0 | 11.1 | 18.5 | 1.38 |
| Ca2SiO4 | 60.7 | 34.5 | 0.8 | 0.2 | 3.7 | |||
| 471 | 1673 | Liquid | 39.6 | 30.4 | 2.6 | 9.2 | 18.1 | 1.30 |
| Ca2SiO4 | 59.7 | 34.6 | 1.1 | 0.2 | 4.4 | |||
| 560 | 1673 | Liquid | 38.3 | 27.5 | 2.3 | 9.4 | 22.4 | 1.39 |
| Ca2SiO4 | 61.2 | 34.0 | 1.0 | 0.2 | 3.7 | |||
| 561 | 1673 | Liquid | 40.3 | 29.3 | 0.2 | 10.4 | 19.9 | 1.38 |
| Ca2SiO4 | 61.8 | 33.8 | 0.1 | 0.2 | 4.1 | |||
| 562 | 1673 | Liquid | 38.3 | 26.9 | 6.5 | 9.8 | 18.5 | 1.42 |
| Ca2SiO4 | 60.5 | 34.0 | 2.4 | 0.2 | 2.8 | |||
| 571 | 1673 | Liquid | 39.7 | 28.9 | 0.1 | 9.3 | 22.1 | 1.37 |
| Ca2SiO4 | 61.2 | 34.8 | 0.0 | 0.2 | 3.8 | |||
| 574 | 1673 | Liquid | 38.7 | 27.6 | 4.1 | 9.3 | 20.3 | 1.40 |
| Ca2SiO4 | 60.8 | 34.5 | 1.5 | 0.1 | 3.1 | |||
| 563 | 1703 | Liquid | 38.7 | 27.4 | 5.8 | 8.5 | 19.7 | 1.41 |
| Ca2SiO4 | 61.3 | 33.5 | 2.1 | 0.2 | 2.9 | |||
| 565 | 1703 | Liquid | 41.0 | 29.8 | 0.2 | 9.1 | 19.9 | 1.38 |
| Ca2SiO4 | 62.2 | 33.4 | 0.1 | 0.2 | 4.1 | |||
| 416 | 1723 | Liquid | 40.0 | 30.2 | 2.0 | 6.5 | 21.2 | 1.32 |
| Ca2SiO4 | 60.2 | 34.7 | 0.8 | 0.1 | 4.2 | |||
| 467 | 1723 | Liquid | 39.9 | 30.9 | 0.3 | 6.6 | 22.3 | 1.29 |
| Ca2SiO4 | 60.8 | 34.4 | 0.1 | 0.1 | 4.5 | |||
| 468 | 1723 | Liquid | 36.0 | 27.6 | 7.2 | 6.3 | 22.8 | 1.30 |
| Ca2SiO4 | 58.7 | 35.2 | 2.7 | 0.1 | 3.2 | |||
| 489 | 1723 | Liquid | 40.6 | 30.5 | 0.1 | 6.6 | 22.0 | 1.33 |
| Ca2SiO4 | 61.5 | 34.4 | 0.1 | 0.1 | 3.8 | |||
| 490 | 1723 | Liquid | 37.6 | 28.4 | 7.0 | 7.1 | 19.7 | 1.32 |
| Ca2SiO4 | 59.71 | 34.57 | 2.41 | 0.11 | 3.16 | |||
| (Mg, Fe2+)O primary phase field | ||||||||
| 436 | 1703 | Liquid | 35.8 | 26.7 | 9.3 | 9.7 | 18.6 | 1.34 |
| (Mg, Fe2+)O | 0.3 | 0.0 | 58.8 | 0.6 | 40.2 | |||
| 501 | 1703 | Liquid | 31.4 | 24.6 | 10.0 | 12.6 | 21.1 | 1.27 |
| (Mg, Fe2+)O | 0.3 | 0.0 | 54.0 | 0.9 | 44.5 | |||
| 375 | 1723 | Liquid | 32.4 | 23.1 | 10.5 | 16.6 | 17.4 | 1.40 |
| (Mg, Fe2+)O | 0.3 | 0.0 | 62.6 | 1.1 | 36.0 | |||
| 376 | 1723 | Liquid | 31.0 | 22.1 | 9.8 | 15.5 | 21.6 | 1.40 |
| (Mg, Fe2+)O | 0.3 | 0.0 | 59.5 | 1.0 | 39.1 | |||
| 379 | 1723 | Liquid | 28.9 | 21.0 | 10.5 | 17.4 | 22.1 | 1.38 |
| (Mg, Fe2+)O | 0.4 | 0.0 | 56.6 | 1.3 | 41.8 | |||
| 442 | 1723 | Liquid | 33.6 | 26.0 | 9.6 | 7.5 | 23.1 | 1.29 |
| (Mg, Fe2+)O | 0.4 | 0.0 | 52.5 | 0.6 | 46.2 | |||
| 496 | 1723 | Liquid | 36.0 | 27.7 | 9.2 | 5.7 | 21.2 | 1.30 |
| (Mg, Fe2+)O | 0.5 | 0.0 | 54.2 | 0.4 | 44.4 | |||
| Liquid with more solid phases | ||||||||
| 137 | 1623 | Liquid | 31.5 | 24.9 | 6.2 | 15.1 | 22.4 | 1.26 |
| Melilite | 41.2 | 25.7 | 2.8 | 28.7 | 1.5 | |||
| Spinel | 0.2 | 0.0 | 21.3 | 65.7 | 12.7 | |||
| 138 | 1623 | Liquid | 32.0 | 25.4 | 6.6 | 14.9 | 21.1 | 1.26 |
| Melilite | 41.2 | 24.5 | 2.1 | 30.8 | 1.4 | |||
| Spinel | 0.2 | 0.0 | 21.7 | 66.4 | 11.7 | |||
| 547 | 1623 | Liquid | 38.4 | 28.4 | 2.5 | 11.9 | 18.8 | 1.35 |
| Melilite | 40.5 | 25.1 | 1.5 | 31.1 | 1.7 | |||
| Ca2SiO4 | 59.0 | 35.2 | 1.0 | 0.3 | 4.5 | |||
| 548 | 1623 | Liquid | 37.9 | 27.2 | 3.4 | 12.9 | 18.6 | 1.39 |
| Melilite | 40.6 | 25.1 | 1.7 | 31.1 | 1.5 | |||
| Ca2SiO4 | 59.7 | 35.5 | 1.4 | 0.2 | 3.2 | |||
| 363 | 1653 | Liquid | 40.6 | 28.5 | 0.1 | 12.8 | 18.0 | 1.42 |
| Melilite | 40.8 | 22.5 | 0.0 | 34.7 | 2.0 | |||
| Ca2SiO4 | 61.5 | 34.1 | 0.1 | 0.2 | 4.0 | |||
| 55 | 1673 | Liquid | 28.8 | 21.7 | 9.0 | 15.8 | 24.4 | 1.33 |
| Spinel | 0.2 | 0.0 | 23.7 | 67.3 | 8.6 | |||
| (Mg, Fe2+)O | 0.4 | 0.0 | 45.8 | 1.1 | 52.6 | |||
| 556 | 1653 | Liquid | 37.4 | 26.5 | 6.1 | 10.4 | 19.6 | 1.41 |
| Ca2SiO4 | 60.4 | 34.3 | 2.4 | 0.1 | 2.7 | |||
| Merwinite | 51.3 | 35.7 | 10.5 | 0.1 | 2.4 | |||
| 435 | 1703 | Liquid | 37.3 | 27.0 | 9.1 | 9.3 | 17.3 | 1.38 |
| Ca2SiO4 | 59.8 | 34.3 | 3.1 | 0.1 | 2.7 | |||
| Merwinite | 51.1 | 35.9 | 11.7 | 0.1 | 1.2 | |||
The pseudo-ternary sections of (CaO+SiO2)-Al2O3-MgO with CaO/SiO2 ratio 1.3 and fixed “FeO” concentrations is an effective method to yield experimental results. However, there are usually differences between predetermined values and the experimental results in the CaO/SiO2 ratio and “FeO” concentration in liquid phases, due to the precipitation of primary solid phases and the oxidation of metallic iron. A large number of experiments therefore had to be carried out and the experimental data are required carefully analysed for the construction of the phase diagram.
In the present study, “FeO”-(CaO+SiO2)-Al2O3-MgO with the CaO/SiO2 ratio 1.3 and fixed “FeO” as 15 and 20 wt% were investigated firstly in terms of the pseudo ternary sections as shown in Figs. 3 and 4. Thick lines in the figures indicate boundaries between primary phase fields and the thin ones are the isotherms derived from the experimental data. In addition, each experimentally determined liquid compositions are represented as symbols in the figures. At the low MgO region, the melilite and dicalcium silicate primary phases are stable, comparing with the higher MgO region where the spinel, merwinite and monoxide [(Mg,Fe2+)O] are major primary phases. Liquidus temperature increases in the melilite and spinel primary phase fields, but it decreases in the dicalcium silicate and merwinite primary phase fields with increasing Al2O3 concentration and is not sensitive in monoxide primary phase field. The effects of the different components on liquidus temperatures will be discussed in details later. The present technique can determine the liquidus accurately. The equilibration temperature was accurately controlled within ±3 K using a Pt-30 pct Rh/Pt-6 pct Rh thermocouple and the chemical compositions of the liquid and solid phases present in the quenched sample were accurately measured by EPMA. However, the experimental data was not exactly on the drawn isotherm lines. For example, the data points on the liquidus lines should be exactly 1.3 of CaO/SiO2 ratio and 15 wt% of “FeO” concentration in Fig. 3. The experimentally determined points do not always have the exact CaO/SiO2 ratio of 1.3 and “FeO” concentrations of 15 wt%. The location of the isotherms should be defined carefully considering the effects of CaO/SiO2 ratio and “FeO” concentration on the liquidus.
Experimentally determined pseudo-ternary section (CaO+SiO2)-Al2O3-MgO with CaO/SiO2=1.3 and 15 wt% “FeO”.
Experimentally determined pseudo-ternary section (CaO+SiO2)-Al2O3-MgO with CaO/SiO2=1.3 and 20 wt% “FeO”.
FactSage,21) a useful thermodynamic modelling program to predict slag chemistry, was employed for comparison in the present study. The databases selected in FactSage 6.2 are “Fact53” and “FToxide”, and the solutions species selected in calculation are “FToxide-SLAGA”, “FToxide-SPINA”, “FToxide-MeO_A”, “FToxide-bC2S”, “FToxide-aC2S”, “FToxide-Mel_”, and “FToxide-Merwinite”. In the compound species, the activity of pure solid iron was set to unity in the iron-saturated condition. The experimental data resulted from the present study and the predictions calculated by FactSage 6.2 are shown in Fig. 5. The thick solid lines are the boundaries between the primary phase fields and thin continuous lines are the 1673 K isotherms determined by experimental results. The thick and thin fragmented lines are the corresponding boundaries and isotherms predicted by FactSage 6.2 calculations. As can be seen from this figure, the same primary phase fields are predicted in the composition range of the present investigation by FactSage, but the range and position of each primary phase field predicted are different with the experimental results. The experimentally determined spinel, melilite and monoxide primary phase fields are generally smaller although there are wider ranges in the dicalcium silicate and merwinite primary phase fields than those predicted by FactSage 6.2. The boundaries in addition of the primary phase fields shift to the direction of increasing Al2O3 wt%. The experimentally determined liquidus temperatures are significantly lower than those predicted by FactSage 6.2 in the spinel, merwinite and monoxide primary phase fields. Only the liquidus temperatures are closed at lower MgO concentration in the melilite and dicalcium silicate primary phase fields. These considerable differences between the predictions and the experimental results indicate that the thermodynamic database for this important slag system need further improvement. In other words, the thermodynamic models dealing with the extensive solid solutions in particular will be enhanced if using the present data.
Comparisons of boundaries and liquidus temperatures between FactSage 6.2 calculations and present results.
In order to compare the boundaries and isotherms, the 1723 K liquidus and boundary lines are projected on the pseudo-ternary section of MgO-(CaO+SiO2)-Al2O3 with CaO/SiO2 = 1.3 as shown in Fig. 6. These are including the previous data of “FeO”-free system,6) 10 wt% “FeO” sections7) as well as the present data at 20 wt% “FeO”. It can be seen from this figure that there are differences in the boundaries of the primary phase fields with “FeO” concentration variation. The melilite and dicalcium silicate primary phase fields are smaller with increasing “FeO” concentration, but the primary phase fields of monoxide and spinel are wider. “FeO” concentration does not have an effect on the range of the merwinite primary phase field. The liquidus temperatures in monoxide primary phase field are not sensitive to the “FeO” concentration although the addition of “FeO” has a significant effect on the liquidus temperatures. The isotherms move to the high-liquidus direction in the primary phase fields of the melilite, dicalcium silicate, spinel and merwinite. The effect of “FeO” on the liquidus temperatures is shown in Fig. 7 as a function of “FeO” concentration. The liquidus temperatures have a general deceasing trend with increasing “FeO” concentration in the primary phase fields of the dicalcium silicate, melilite, merwinite and monoxide. However, it has a less significant effect in the spinel primary phase field. The effect of “FeO” on the liquidus temperatures is almost similar in the melilite and spinel primary phase fields, whilst there are substantial difference in the isotherms between “FeO”-free and 5 wt% of “FeO”. This means that the variations of “FeO” from 0 wt% have considerable effects on the liquidus temperature in the primary phase fields of the merwinite and dicalcium silicate while only slightly change the isotherms when the “FeO” increases from 5 to 20 wt% in these primary phase fields. This may be due to the solubility of “FeO” in the solid solutions, depending on Al2O3 and MgO concentrations in slags. It can be seen from Figs. 3 and 4 that in the dicalcium silicate primary phase field, the liquidus temperatures decrease with increasing Al2O3 concentration at a given MgO. The Al2O3 concentrations as a function of “FeO” concentration in liquid is shown in Fig. 8 for the 1723 K liquidus in the dicalcium silicate primary phase field. The solubilities of “FeO” in the corresponding dicalcium silicate as a function of “FeO” concentration in liquid are also present in Fig. 8 for comparison. It can be seen that “FeO” concentrations in the dicalcium silicate increase rapidly at low “FeO” level and then slowly at higher “FeO” level. The decrease of Al2O3 concentration in the liquid with increasing “FeO” shows the same trend.
While the pseudo ternary sections of phase diagrams provide a large amount of fundamental information for complex slag systems, pseudo-binary phase diagrams can be used more conveniently and easily in practice both for research and engineering applications, in particular to evaluate the effects of slag compositions on the liquidus temperature. They can be derived directly from the experimentally determined pseudo-ternary phase diagrams.
Figure 9 shows the liquidus temperatures as a function of Al2O3/(CaO+SiO2) ratio at fixed MgO of 5 (Fig. 9(a)) and 10 wt% (Fig. 9(b)), respectively. The continuous lines present the experimentally determined results of 15 and 20 wt% “FeO”, and the dotted lines the previous ones of 0, 5 and 10 wt% “FeO”.6,7) It can be seen from Fig. 9(a) that more primary phases are present at 15 and 20 wt% “FeO” than 0, 5 and 10 wt% “FeO” at fixed 5 wt% MgO. At 15 and 20 wt% “FeO”, dicalcium silicate, merwinite, melilite and spinel are the primary phase fields, while merwinite and spinel are not stable at 0, 5 and 10 wt% “FeO”. The liquidus temperatures decrease in dicalcium silicate and merwinite primary phase fields, but increase in melilite and spinel primary phase field with increasing Al2O3/(CaO+SiO2) ratio. As can be seen from the figures, the higher “FeO” concentration in the slags leads to the lower liquidus temperatures in the primary phase fields of dicalcium silicate, melilite and spinel, slightly increased in merwinite primary phase field with incresing “FeO” from 15 to 20 wt%. It can be seen from Fig. 9(b) that more primary phase fields are present at fixed MgO of 10 wt% than 5 wt%. At 15 and 20 wt% “FeO”, dicalcium silicate and melilite primary phases are not stable, but the primary phase fields of merwinite, monoxide [(Mg,Fe2+)O] and spinel are existing. The liquidus temperatures in general decrease in dicalcium silicate, merwinite and monoxide, but increase in melilite and spinel with increasing Al2O3/(CaO+SiO2) ratio. The increase of “FeO” decreases the liquidus temperatures significantly, as shown by the lines of 0 and 5 wt% “FeO” in Fig. 9. However, there are only slight effects of “FeO” concentration in the slags on the liquidus temperatures from 5 to 20 wt% “FeO” at fixed MgO of 10 wt%.
Figure 10 shows the liquidus temperatures as a function of MgO/(CaO+SiO2) ratio at fixed Al2O3 of 10, 15 and 20 wt%, respectively. At 10 wt% Al2O3, the liquidus temperatures of “FeO”-free slags are very high, which were not measured. For 15 and 20 wt% Al2O3, the five lines corresponding to “FeO” concentration of 0, 5, 10, 15 and 20 wt% are respectively shown for comparison. The previous results of 0, 5 and 10 wt% “FeO” are presented in these figures, shown with dash lines.6,7) The continuous lines illustrate the present experimentally determined data corresponding to 15 and 20 wt% “FeO”, respectively. It can be seen from Fig. 10(a), at fixed Al2O3 concentration of 10 wt%, the dicalcium silicate is the primary phase at lower MgO/(CaO+SiO2) ratio, but merwinite and monoxide are stable at higher MgO/(CaO+SiO2) ratio. The liquidus temperatures initially increase then decrease with increasing MgO/(CaO+SiO2) ratio in dicalcium silicate primary phase field, while they exhibit increasing trend in merwinite and monoxide primary phase fields. At fixed Al2O3 concentration of 15 wt%, melilite is the primary phase field at lower MgO/(CaO+SiO2) ratio. In this primary phase field, liquidus temperatures increase firstly then decrease at 0, 5 and 10 wt% “FeO”, but there are only decrease trend in the liquidus temperatures at 15 and 20 wt% “FeO” with increasing MgO/(CaO+SiO2) ratio. At higher MgO/(CaO+SiO2) ratio, merwinite and/or spinel and monoxide are stable depending on the “FeO” concentrations. The liquidus temperatures increase with MgO/(CaO+SiO2) ratio in those primary phase fields. Lastly, at fixed Al2O3 concentration of 20 wt%, melilite and spinel primary phase fields can be the primary phase fields. The boundary between melilite and spinel moves to low MgO/(CaO+SiO2) ratio direction with increasing “FeO” concentration. This means that, before “FeO” fully reduced from the slags, melilite primary phase is more stable than spinel at low Al2O3.
As discussed above, the even well-developed thermodynamic model such as FactSage still needs to be enhanced for the more accurate description of the phase equilibria and liquidus temperatures. The present study reveals there are the significant differences between the experimental data and FactSage predictions. The accurate data of the solid solution resulted from the present work provide experimental information to optimise the thermodynamics models including FactSage. It is only possible to improve the thermodynamic models with a large number of accurate experimental data including solid solutions. Since “FeO” concentrations in the melilite are affected by CaO, Al2O3 and MgO, the distribution of “FeO” between liquid and melilite is more complicated than the other primary solids. Figures 11(a) and 11(b) show the distribution of “FeO” between liquid and dicalcium silicate at 1673 and 1723 K, respectively. The distribution curve should always pass the point of origin (0, 0). Since the data points do not have exactly 1.3 of CaO/SiO2 and desired MgO concentration, the effect of CaO/SiO2 and MgO concentration in liquid on the solubility of “FeO” in the Ca2SiO4 should be carefully considered to locate the curve of distribution of “FeO”. It can be seen from the figures that “FeO” concentration in solid slightly increases with increasing “FeO” concentration in the corresponding liquid. Figures 12(a) and 12(b) show the distribution of “FeO” between liquid and solid of spinel and monoxide, respectively at 1673 K and 1703 K. As seen Fig. 12, “FeO” concentration in the spinel increases slightly with increasing “FeO” concentration in the corresponding liquid while it increases significantly in monoxide primary phase. The values were also affected by the MgO concentration in the corresponding liquid, due to MgO can substitute “FeO” in spinel and monoxide. It can also be seen from Fig. 12 that “FeO” concentration decreases with increasing the liquidus temperature in spinel and monoxide primary phase fields.
Distribution of “FeO” between liquid and Ca2SiO4 at (a) 1673 K and (b) 1723 K, CaO/SiO2 ratio in liquid = 1.26 − 1.33.
Distribution of “FeO” between liquid and solid in (a) spinel and (b) (Mg, Fe2+)O primary phase fields.
Phase equilibria and liquidus temperatures have been investigated in the system “FeO”-CaO-SiO2-Al2O3-MgO with CaO/SiO2 ratio of 1.3 and at fixed “FeO” of 15 and 20 wt%. The “FeO”-containing blast furnace slags can be characterised accurately by experimentally determined phase diagrams of the liquidus temperatures and slags compositions in the primary phase fields of melilite, dicalcium silicate, spinel, merwinite and monoxide. Those phase diagrams presented in present study were obtained through the carefully designed experiments with well-developed experimental techniques and systematic analyses of a large amount of measured data. The results illustrate that the liquidus temperatures of the blast furnace slags generally decrease with increasing “FeO” concentrations. The series of pseudo-binary phase diagrams were directly derived from the pseudo-ternary phase diagrams, providing useful tools to easily evaluate the effects of the slag compositions on the liquidus temperatures. There are significant differences in the liquidus temperatures and slag compositions between the experimental results and the FactSage 6.2 predictions. The experimentally determined data can be directly used for the optimisation of the thermodynamic models. Combined with our previously reported data, this study represents a systematic investigation on the system “FeO”-CaO-SiO2-Al2O3-MgO in equilibrium with metallic iron. It provides the extensive experimental data fulfilling the current knowledge gap that can be used for better understanding the complex reactions consisting of multi-component slag systems, such as slags in the iron-making blast furnace.
The authors wish to thank Baosteel through The Baosteel-Australia Joint Research and Development Centre (BAJC) for providing financial support for this project. Mr. Ron Rasch and Ms Ying Yu of the Centre for Microscopy and Microanalysis at the University of Queensland, who provided technical support for the EPMA facilities, are grateful.
