Abstract: The magnesia-hercynite refractories were prepared with magnesia and hercynite by sintering process. The bulk density, apparent porosity and cold crushing strength were measured. The elastic modulus of samples was measured by the method of stress and strain. The phase constituents of specimens was analyzed by X-ray diffraction (XRD), and the microstructure was observed with scanning electron microscopy (SEM).The experimental results show that the appropriate sintering temperature for samples is 1600 ℃ with the highest bulk density and the lowest apparent porosity . The cold crushing strength of samples decreases with the adding of the content of hercynite. The optimum content of hercynite is 3%-4%. The specimens with addition of hercynite particles have higher elastic modulus, so the specimens with addition of hercynite particles have better thermal shock resistance than the specimens with hercynite powder. Thermodynamic calculation show that: the magnesia reacts with hercynite resulting in magnesia-alumina spinel at temperature higher than 182 ℃. The microstructure photos also show that iron protoxide in hercynite can diffuse into magnesia particle and reacts with magnesium oxide, and forms magnesia-alumina spinel ring around magnesia when magnesia-hercynite refractories are sintered at high temperature. The reaction leads to produce microcrack between hercynite and magnesia particle.

Key words: magnesia-hercynite refractories%elastic modulus%thermal shock resistance