Role of spinel composition in the slag resistance of Al2O3–spinel and Al2O3–MgO castables

The slag resistance of Al2O3–spinel, Al2O3–MgO and high-Al2O3 castables was tested using a gas-fired rotary slag test furnace and BOF slag (CaO/SiO2=3.8, Fe2O3=33.4 wt.%). The spinels used in the test contained 73, 90 and 94 wt.% Al2O3. The XRD patterns showed that no spinels can be identified in the mixes consisting of 75 wt.% BOF slag +25 wt.% spinel and being fired up to 1400° or 1500 °C. The same mixes were used for a sessile drop test using a prefired Al2O3–spinel castable as a substrate. The experimental results indicated that the penetration decreases with the increasing MgO content in spinels. The role of spinel composition in the slag resistance of Al2O3–spinel and Al2O3–MgO castables is to dissolve itself in the penetrating slag and as a result to lessen the penetration.