Effect of spinel content on hot strength of alumina-spinel castables in the temperature range 1000-1500 degrees C

Hot modulus of rupture of Al2O3-spinel castables containing 5-15 wt% alumin a-rich magnesia alumina spinel and 1.7 wt% CaO generally increases with inc rease in spinel content and temperature from 1000 to 1500 degrees C. The ma gnitudes of hot modulus of rupture of castables containing 15 wt% spinel an d 1.7 wt% CaO are 14.3 MPa at 1400 degrees C and 15.6 MPa at 1500 degrees C , while those of castables containing 20 wt% spinel and 1.7 wt% CaO are 12. 5 MPa at 1400 degrees C and 14.7 MPa at 1500 degrees C. The former castable s contained 15 wt% spinel of -75 mu m size, while the latter contained 10 w t% spinel of + 75 mu m size and another 10 wt% spinel of -75 mu m size. The bond linkage between the CA(6) and spinel grains in the matrix is believed to cause both the spinel content and temperature dependence of hot strengt h of Al2O3-spinel castables, as well as fine grain spinel even in amount le ss than coarser grain spinel to be more effective for enhancing hot strengt h. The trend of the magnitude of thermal expansion under loan (0.2 MPa) abo ve 1500 degrees C of the castables is not necessarily indicative of the mag nitude of hot modulus of rupture at 1400 or 1500 degrees C. (C) 1999 Elsevi er Science Limited. All rights reserved.