In Situ Spinel Formation In Al2o3-Mgo-C Filter Materials For Steel Melt Filtration

Spinel-based ceramics for molten steel filtration were prepared from a mixture of alumina, magnesia and carbon precursors. Samples were analyzed in the form of bars heat treated at different temperatures, or as reticulated foams, after immersion in a steel melt at 1640 degrees C. An effect of the composition of the filters on the amount of spinel formed after the heat treatments was observed, which favored the MgO-rich composition. The formation of spinel successfully decreased the disadvantageous shrinkage occurring because of high temperature sintering and pyrolysis phenomena. The presence of carbon affected the rate of spinel formation, and led to additional carbide-based phases after heating at 1600 degrees C. The immersion of reticulated foams, only pre-heated at 800 degrees C, into molten steel at 1640 degrees C led to the virtual transformation of the starting oxides into spinel, and the foams survived well the thermal shock. These materials are therefore well suited for the fabrication of advanced ceramic filters for molten metal filtration. (C) 2014 Published by Elsevier Ltd and Techna Group S.r.l.