Studies On The Microstructure Of Calcined Bauxite And The Relationship Between Microstructure And High Temperature Properties

Bauxite based refractory materials are used in refractory industry early becauseof its excellent performance, refractories that aggregate is bauxite grogs are widelyused in steelmaking and ironmaking industry, such as blast furnace, ladle slag line andwall, hot-blast stoves, electric furnace roof, etc. At present, there are two ways toproduce bauxite grogs: ore bulk sintering and homogenized sintering. Theperformance advantages and using scope of bauxite-based homogenized grogs has notbeen fully understand in practice. Only on the foundation of traditional bulk sinteredbauxite simply. In addition, broken ore produced by the process of bauxite miningcan’t be calcined directly in the kiln. Homogenized sintering process crush thesebroken bauxite into power, and make them into green body, which make the bauxiteresources are used efficiently. But the bauxite power fineness is usually under0.044mm, effect of different fineness on the sintered bauxite was rarely reported. Thispaper mainly research the above problems.The traditional bulk sintered bauxite and homogenized grogs were researched toanalyze phase composition, physical properties and microstructure, especiallyresearched the distinction of grogs produced by different process, and then analyzeperformance differences in the industrial application. Homogenized grogs grain is bigand the grain boundary is obvious and broad. Impurities are homogenized anduniformly distribute in the grain boundary prevents direct contact between the grains.The traditional bulk sintered bauxite grain is small and the grain boundary is notobvious. Many small grains are connected to form a network structure of “large grain”,and the impurity phase reticulate in it. This microstructure determines thecharacteristics of the traditional bulk sintered bauxite have better high temperatureperformance than homogenized grogs.Different fineness(0.147~0.075mm,0.075~0.044mm,＜0.044mm) of bauxitefrom Shanxi province were used as raw material to prepare adobe with bond andcalcined in the electric furnace. The sintering condition of different grade bauxite andfineness under different temperature was studied. Phase composition andmicrostructure properties were analyzed by X-Ray diffraction, thermal analysisinstrument, scanning electron microscope, etc. The results show different grade ofbauxite suitable sintering temperature and fineness: The optimum sinteringtemperature of89%Al2O3bauxite is1580℃, and the optimum fineness is0.075~0.044mm; The optimum sintering temperature of84%Al2O3bauxite is1600℃,and the optimum fineness is0.075~0.044mm; The optimum sintering temperature of74%Al2O3bauxite is1650℃, and the optimum fineness is0.147~0.075mm. Thefiner the fineness of bauxite is, the faster the reaction rate. Reaction and diffusioncapacity enhancement will lower the temperature at the maximum reaction rate. It has many pores in the grains after calcined when the fineness is under0.044mm, whichlead to the decrease of bulk density.