With Al2O3 in different contents and crystal forms added,the ultra-low cement bonded SiC castables is cast with vibration,and then subject to nitridation at 1420 ℃ in high-purity nitrogen flow to obtain the refractory material with Sialon bonded SiC. With the testing of the conventional physical properties of the nitrided sample,the paper emphasizes the effect of Al2O3 with different contents and crystal forms on the flexural strength at a high temperature(1200 ℃ and 1400 ℃)and thermal shock resistance of the sample,and analyzes its phase and microstructure by XRD and SEM adopted. The results show that Sialon can be formed by the in-situ reaction of Si with the binding phase at a high temperature in nitrogen,and is distributed in a network like interweaving pattern. It can enhance the bonding between SiC particles and the matrix,hence improving the high-temperature performance of the sample of SiC castables. When the content of corundum is 3％,the flexural strength at a high temperature(1200 ℃ and 1400 ℃)is 64.3 MPa and 13.7 MPa respectively. As such content increases,the Sialon phase begins to rise,but the flexural strength does not change much. When the content of Al2O3 micro powder is 3％,the Sialon phase increases to 15％,which is higher than the sample with 12％ corundum content. And the flexural strength is 64.3 MPa and 15.2 MPa. Besides,the overall thermal shock resistance of the original sample is better than that of the one with corundum newly added.
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