Effects of Different Boron Compounds on the Corrosion Resistance of Andalusite-Based Low-Cement Castables in Contact wit
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Today, the use of nonwetting additives is commonplace in refractories for the aluminum industry, particularly for holding and melting furnaces. It is believed that these additives could decrease significantly the corrosion of refractories, mostly because of a decrease in the availability of free silica by molten aluminum.[1] Boron-containing materials such as B2O3 and BN have rarely been used as coatings[2–4] or additives[5,6] in applications involving molten Al alloy contact, and these materials showed outstanding performance in these applications. However, the interfacial behavior of these materials with molten Al alloy, especially with regard to aluminosilicate refractories, is not clear, and comprehensive research on the interfacial reactions has not been explained. In this work, the interfacial behavior ESMAEIL ADABIFIROOZJAEI, Graduate Student, formerly with the Department of Materials Engineering, Isfahan University of Technology, Isfahan 8415683111, Iran, is now with the Amol Refractory Industry Company, Amol, Mazandaran 4616159748, Iran. Contact e-mail: e.adabifi[email protected] PRAMOD KOSHY, Research Associate, and CHARLES CHRIS SORRELL, Professor, are with the School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia. Manuscript submitted June 18, 2011. Article published online December 21, 2011. METALLURGICAL AND MATERIALS TRANSACTIONS B
of andalusite low-cement castable (LCC) refractories (containing boron compounds) with molten Al alloy at 1123 K and 1433 K (850 C and 1160 C) is investigated using the Alcoa cup test. An andalusite LCC refractory was chosen as the base material, and its properties are listed in Tables I and II, and the chemical composition of used Al alloy are presented in Table III. The testing of refractory corrosion resistance (extent of metal penetration) was carried out at using the Alcoa cup test at 1123 K (850 C) for 150 hours and 1433 K (1160 C) for 75 hours. The method of preparing the test samples and the procedure for the Alcoa cup test are listed in our previous publications.[7,8] All raw materials for the tests were provided by Amol Refractory Industries Company, Iran, and were of industrial purity. Figure 1 shows the images of the sectioned samples after testing at different temperatures. These figures show that sample A (without any additive) has undergone extensive corrosion by molten aluminum. However, samples B, C, and D (containing B2O3, B4C, and BN, respectively) showed good resistance to Al alloy penetration. Figure 2 shows the X-ray diffraction (XRD) patterns of the different samples prefired at various temperatures 873 K to 1373 K (600 C to 1100 C) for 5 hours. The base refractory (BS1100) contains andalusite as the major phase, with kyanite, corundum, anorthite, and cristobalite as minors. Andalusite and kyanite are polymorphs that tend to coexist naturally[9]; anorthite forms from reactions between cement and microsilica,[8,10–12] whereas cristobalite forms from microsilica transformations.[1] The absence of nonw
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