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REFRACTORIES play a significant role in a number of core industries, particularly in the iron and steel sector, which alone accounts for the consumption of nearly 70 pct of total refractories produced.[1] These are used extensively by the steel industry in applications such as the internal linings of furnaces, in vessels for holding and transporting metal and slag, slide gate plates, shrouds, and tundish rods.[2,3] Various forms of carbon are being used to an ever increasing extent in combinations with oxides such as magnesia, alumina, silica, calcia, and zirconia to impart special properties including resistance to slag corrosion, improvements in thermal conductivity, thermal shock, and wear resistance at high temperatures.[4,5,6] However, the degradation of carbon-based refractories through carbon depletion is an important issue as it can result in a decreased refractory resistance to chemical attack, carbon pickup by steel, and inclusions in molten metal. When hot metal comes in contact with a refractory, it can dissolve carbon from the RITA KHANNA, Senior Research Associate, and VEENA SAHAJWALLA, Professor, are with the School of Materials Science and Engineering, The University of New South Wales, Sydney NSW 2052, Australia. Contact e-mail: [email protected]. BRENTON RODGERS, Process Leader, is with Boral Bricks, Bringelly, Sydney, NSW, Australia. FIONA McCARTHY, Senior Analyst, is with AME Mineral Economics, Sydney, NSW, Australia. Manuscript submitted January 9, 2006. METALLURGICAL AND MATERIALS TRANSACTIONS B

contact surface leaving behind a porous region. While an increase in porosity leads to a reduced resistance to chemical attack, carbon from the refractory can also be a source of carbon pickup particularly for the ultra-lowcarbon steel. When the surface structure becomes porous, some aggregate particles may come off the hot face and fall into molten steel to become inclusions. Refractory failure/wear can lead to a loss of production time, equipment, and sometimes the steel product itself. A fundamental understanding of refractory behavior at high temperatures and research into the service life of carbon-bearing refractories is therefore crucially important. The focus of this article is on the dissolution of carbon from alumina-carbon mixtures into liquid iron at 1550 °C. Literature is available on the high-temperature interactions of individual components such as carbon and alumina with liquid iron, along with a few studies on aluminacarbon composites.[7–11] In a systematic study, Zhao and Sahajwalla carried out experimental investigations on a range of alumina-synthetic graphite mixtures and liquid iron at 1550 °C and have reported results on the interfacial phenomena, wettability, and carbon dissolution.[12] While good wetting (contact angles ;38 deg) was observed between liquid iron and 100 pct graphite sample, measured contact angles between 100 pct Al2O3 and liquid iron were very high (;125 deg) indicating poor wetting. Contact angles for alumina-graphite mixtures in the intermediate