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Effects of magnesia fines addition (4％,6％ and 8％ in mass ) and spinel with different compositions (alumina-rich,magnesia-rich and stoichiometric spinel) on thermal expansion behavior of alumina magnesia castables were researched using tabular corundum,magnesia fines,spinel fines,p-Al2O3,Secar-71 cement and SiO2 fume as main starting materials.The results show that:(1) thermal expansion coefficients of specimens with 4 mass％ and 6 mass％ magnesia fines have the similar change tendency,increasing slightly with temperature rising; when magnesia addition is 8 mass％,the thermal expansion coefficient increases obviously at 1 050 ℃ and reaches the peak at 1 350 ℃ ;(2) when MgO content is the same,the specimen with magnesia-rich spinel has the lowest thermal expansion coefficient; (3) for the castables specimens with the same MgO content,the specimen with magnesia has higher thermal expansion coefficient than that with presynthesized spinel,which is related with the secondary spinelization during the heating process.