The production of KP-95 corundum files [1, 2] involves certain laborious and energy-consuming processes in obtaining kaolinized corundum chamotte, including dry pressing the finely milled mixture of alumina and kaolin, replacing the briquet on kil cars, drying it, and firing in a tunnel kiln at 1520-1580~The Semiluksk factory has developed and implemented a method for the production of high-grade tiles for gate valves, which involves replacing the kaolinized corundum chamotte by a more economical material. It is best to use m~lite--corundum chamotte obtained at the Semiluksk factory, using the normal methods.The water absorption of the mullite--eorundum ehamotte is not more than 2%, * A1203 content not less than 85%, Fe203 not more than 0.5%, and SiO 2 9-10%. The main requirement in changing from kaolinized corundum ehamotte (not less than 95% A1203, not more than 0.5% Fe203 and 1.8-2% SiO2) to a material with a lower refractoriness was the preservation, together with the high density, of adequately high-temperature strength and corrosion resistance, which ensure the stable operation of the tiles.It is known that the high-temperature strength and also the resistance to the action of molten slags and metal by aluminosilicate refractories of a granular structure depend on the composition and structure of the * Here and subsequently parts by weight.
Experience in the use of slide gates for teeming steel and the results of scientific investigations are an indication of the significant influence of the porous structure of the refractory plates on their service properties and their life in service.For example, it has been established [i] that refractory parts intended for operation in slide gates must contain primarily fine voids (finer than 30 ~m).Japanese investigators have assumed that in the periclase plates the average void size must be no greater than 2.5 ~m [2].From the results of a microscopic study of the structure of voids and the data of mercury porometry, in domestic production periclase plates about 65% of the volume of void space is due to voids with a diameter of less than 50 ~m. They are filled in impregnation of the plates with pitch [3].Using as a base periclase with a grain size of not more than 1.2 mm, plates were obtained with a fine porous structure (predominant size of the voids less than 16 Dm) which showed high wear resistance in service in steel-teeming ladle slide gates [4].The void space of the parts is formed by intragranular voids and intergranular spaces. Therefore, the distribution of voids by sizes must depend both upon the structure of the filler and the conditions of preparation of the raw material (grain and substance compositions of the charge, form and quantity of the binder, pressing pressure, etc.) and upon the character of sintering in firing.In connection with this the establishment of the interrelationship between the characteristics of part porous structure and the technical parameters of its production may be assumed to be very useful.However, information on the distribution of voids in the raw material for the periclase plates and on the change in their structure during firing is lacking.The purpose of this work was to investigate the porous structure of the periclase inserts of built-up plates after pressing and also of the changes in this structure during calcination and firing.
Sliding gates are becoming more and more widely used in steel casting in Soviet steelworks. Experience of the use of these gates is constantly being analyzed. On the basis of these analyses, the specifications for the refractory materials are refined and the operational conditions during casting improved.The main factor determining the reliable operation of the gates is their metal resistance, i.e., the ability of the material of the refractory tiles to withstand the aggressive action of liquid steel. From 30 to 5(f/o of unsatisfactory castings arise from factors associated with the development of excessive interaction between the tile material and the components of the liquid steel [1].
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