Fundamentals of Silico-Ferrite of Calcium and Aluminum (SFCA) and SFCA-I Iron Ore Sinter Bonding Phase Formation: Effect
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LICO-FERRITE of calcium and aluminum (‘SFCA’) phases are the key bonding materials of industrial iron ore sinter.[1] Sinter is a major feedstock material of blast furnaces, utilized extensively worldwide in the production of steel from iron ore. Increased understanding of the compositional and thermal stability domains of SFCA phases, and their formation mechanisms, has the potential to improve the efficiency of the sintering process by being better able to predict the optimal sintering conditions (e.g., temperature,
NATHAN A.S. WEBSTER, Research Scientist, is with the CSIRO Mineral Resources Flagship, Box 312, Clayton South, VIC 3169, Australia, also with the Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia. Contact e-mail: [email protected] MARK I. POWNCEBY and IAN C. MADSEN, Principal Research Scientists, are with the CSIRO Mineral Resources Flagship. ANDREW J. STUDER, Research Scientist/Instrument Scientist, is with the Australian Nuclear Science and Technology Organisation. JAMES R. MANUEL, Research Projects Officer, is with the CSIRO Mineral Resources Flagship, PO Box 883, Kenmore, QLD 4069, Australia. JUSTIN A. KIMPTON, Principal Beamline Scientist, is with the Australian Synchrotron, 800 Blackburn Rd, Clayton, VIC 3168, Australia. Manuscript submitted November 24, 2013. Article published online July 22, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
oxygen partial pressure) required to produce highquality product based on the chemical composition and physical characteristics of a given iron ore sinter mixture. Additionally, it may allow better prediction of the chemical and physical modifications of a particular iron ore sinter mixture that is required to produce highquality product for given sintering conditions. A detailed description of the sintering process, as well as a schematic diagram,[2] has been published previously.[3] The ‘SFCA’ in iron ore sinter has been categorized on the basis of composition, morphology, and crystal structure into two main types. The first is a high-Fe, low-Si form called SFCA-I which has a characteristic platy (also described as acicular) morphology. Mumme et al.[4] reported that an SFCA-I phase in industrial sinter contained 84 wt pct Fe2O3, 13 wt pct CaO, 1 wt pct SiO2, and 2 wt pct Al2O3, and also synthesized SFCA-I material which had the composition 83.2 wt pct Fe2O3, 12.6 wt pct CaO, and 4.2 wt pct Al2O3. The second ‘SFCA’ type is a low-Fe form called SFCA which is described as having a columnar morphology. SFCA found in industrial sinters typically contains 60 to 76 wt pct Fe2O3, 13 to 16 wt pct CaO, 3 to 10 wt pct SiO2, 4 to 10 wt pct Al2O3, and 0.7 to 1.5 wt pct MgO,[5,6] and with basicity (CaO:SiO2 ratio) values in the range 1.6 to 4.4.[7] Figure 1 shows typical optical micrographs for SFCA-I and SFCA found in iron ore VOLUME 45B, DECEMBER 2014—2097
Al2O3 CA3
SFCA-I Fe2O3
SiO2
CF3
C4 S3
CaO
Fe2 O3
(a)
20 µm
CA3 = CaO.3Al2O3
(a)
35 30
Fe3 O4
25 20
SFCA
15
4/10
2.5/10
5/10 10 5
C4 S3
CF3
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