Obtaining alumina insulating refractories with polystyrene additions

Structure formation of water suspensions of alumina containing polystyrene additions

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Increasing the working temperature and using protective and controlled atmospheres in furnaces require a Boost in the production and an expansion of the range of corundum, heatinsulating products of high purity with more than 99% concentration of ~-A1203.Corundum insulating articles produced by our industry in grades KL-I.3, with a reduced concentration of A1203 (95%) and a high porosity (62-65%) possess moderate working temperatures (1550~ and a low corrosion resistance (they contain 3.5% CaO and 0.5% Si02).Previous studies were made of the effect of powdered AI=03 fineness [i], the pH of the dispersion medium [2], and surface-active agents [3] on the casting properties of slips and the properties of the corundum articles.The present article gives the results of a study of the rheological and structuralmechanical properties of alumina suspensions with additions of polystyrene used for preparing, by casting, corundum heat-insulating articles containing not less than 98% AI=O3, of a stated structure and with an application temperature of up to 1800~ (after-contraction not more than 1%).The starting components consisted of alumina grades GK and G-O0, and powdered formed polystyrene as the additive [4].The rheological properties of the alumina suspension were determined on a rotation viscometer RV-8, and the fluidity of the slips on the "Konus AzNII" apparatus~ The electrolytes used to alter the pH consisted of HCI and NH~OH.The experiments were done with the use of polystyrene balls diameter <0.5, <i, and <2 mm~ It was found that the properties of the suspension are affected by the grain-size composition of the polystyrene (Table i). An increase in the diameter of the polystyrene balls from <0.5 to <2m m leads to a reduction in the amount (Fig.

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Influence of the type of alumina and additives on the properties of corundum heat-insulating refractory

“…The articles were prepared by slip casting in metal molds and the pore-forming agent consisted of ashless combustible -foamed polystyrene [2] with grain sizes of less than 3 mm in amounts of 60% (by volume) in relation to the alumina. The bond constituent consisted of alumina G-00 ground in a vibromill to a grain size of 6-12 ~m, to which we added three types of filler in order to reduce the shrinkage: unground alumina grade GK and G-00, and also alumina calcined at 1550~ and vibromilled to a grain size of less than 4 #m using the G-00 type.…”

Vibratory densification of thermal insulation corundum products

“…Numerous technological routes based on casting and semidry compaction have been developed for manufacturing lightweight corundum products; however, the products contain significant amounts of impurities [4][5][6][7][8][9] or exhibit low strength [i, i0] and high apparent density [ii]. Lightweight high-alumina corundum products are obtained by treating with a hydrochloric acid solution [12], introducing ashless combustible additives like polystyrene [13,14], or using hollow corundum granules [15]. However, the first method is quite complex, the second method requires machining for producing shaped products, and the third method has not yet been developed completely.…”