Effect of spinel content on slag attack resistance of high alumina refractory castables

High alumina refractory castables based on the Al2O3-MgO-CaO diagram ternary system were prepared using tabular alumina, white electrofused corundum, calcined alumina, synthetic spinel, dead-burned magnesia, dolomite, and calcium aluminate cement as starting raw materials. Two kinds of slags with 9.02 and 4.14 CaO/SiO2 ratios were studied for slag resistance by means of Crucible tests. The corrosion thickness increases with increase in magnesia content in all the designed compositions. The slag penetration decreases with increases in spinet content. Taking into account these results a refractory castable composition for its positioning into a steelmaking ladle was chosen. Microstructural studies by SEM of samples taken from the slag line and wall in a steelmaking ladle were carried out. The correct amount of spinel required for practical applications was determined by the Al2O3-MgO-CaO-SiO2 diagram quaternary system. A detailed model of the attack mechanisms is proposed. (C) 2007 Elsevier Ltd. All rights reserved.