SU910556A1 - Method for mixing refractories - Google Patents

Description

The invention relates to the refractory industry and can be used in the manufacture of large-dimensioned corundum and mullite-corundum shaped products, working under conditions of prolonged exposure to mechanical loads at high temperatures and in various corrosive environments, such as steel-casting refractory parts. A known method for producing corundum large-size articles based on technical alumina by preliminarily firing a briquette from technical alumina, its subsequent grinding to a grain size of 4 mm and smaller, and subsequent sintering roasting of products at a temperature of 1650-1750 ° С L1J, the density of the products obtained according to this method, it is provided by intensive sintering them in roasting, after preliminary low-temperature roasting of the briquette carried out at 1200-1300 ° C. However, intensive sintering of the product in the firing process is accompanied, along with compaction, by a significant change in their linear dimensions. Linear shrinkage of products obtained by this method reaches 15–20%, which leads to the formation of shrinkage cracks in the products and makes it impossible to manufacture large-sized products of complex shape. A significant disadvantage of such products is also increased deformation, especially clearly manifested under service conditions under prolonged exposure to high temperature and mechanical stress. The closest technical solution to the invention is a method of making refractories from technical alumina by briquetting a mixture of alumina and 3-8 clay component, burning the briquette, grinding, preparing the molding material, molding and burning products 2. At the same time maintaining a high density while reducing linear shrinkage is ensured by the clay component and the burning of the briquette and the product at the same temperature in the range of 15201630 0, and the heating and cooling of the briquette is carried out at a rate corresponding to nno 30-35 and 70-80 degrees / h, and products 20-25 and 50-80 degrees / h. The products obtained by this method have an open porosity of not higher than 121, linear shrinkage in this case does not exceed 5. However, for a number of particularly important refractory steel-casting products, for example, slide gate plates, these indicators are not sufficient, since, in order to prevent the penetration of the molten metal and slag into the refractory during the operation of the product should have even greater density with minimal linear shrinkage. A significant obstacle to long-term use of such products in the service is also their low resistance to stresses: under prolonged loading of the scientific research institute at high temperature, the product is deformed, and their further operation becomes impossible. The aim of the invention is to reduce open porosity, linear shrinkage and increase creep resistance. The goal is achieved by the fact that in the method of manufacturing refractories by briquetting a mixture of technical alumina and a clay component, burning the briquette, grinding and preparing the molding material, molding products and burning them at a temperature of 1550-1750 C and at a heating and cooling rate of 20-60 and 40-100 degrees / h, respectively, brie bake (eta is carried out at a temperature of 1700-180C, and the heating and cooling of the briquette is carried out at a speed of BOO-TLU degree / h. The baking is fired at a higher temperature than the sintering baking of the products allows In order to prepare the molding mass, a high-density, chamotte filler: the introduction of such a high-density filler into the mixture at-5 leads to the fact that the linear shrinkage of the products in the calcination is reduced to 2-3%. The increase in the density of the products is provided as an introduction to the briquette - 3-20, 6 as well as adjustment of the rate of heating and cooling of the briquette and products. Slow heating of the products ensures recrystallization of their sintering. Slow cooling prevents thermal cracking in the product. The high-speed (6001100 degrees / h) baking and cooling of the briquette contributes to the preservation of its high reactivity, which further provides intensive sintering of products based on it. Along with the intensification of sintering products, obtaining a dense-baked briquette leads to an increase in the creep-proof of products. The content of the clay component is less than 3, as well as lowering the firing temperature of the products below leads to a decrease in the density of the products. The content of the clay component over 20 leads to a significant increase in the content of the glass phase in the product, "the NTO will negatively affect its slag resistance. Firing products at a temperature above is unacceptable due to the lack of the necessary furnace, units. The method of manufacturing technical alumina products is carried out as follows. The raw materials (technical alumina and clay component are subjected to joint grinding, moistened with sulphite-alcohol bards or sulphite-yeast brewing solution and briquetted with semi-dry or plastic method. in its composition not less than 35% of particles smaller than 0, OBZ mm and. Prepare the molding material, from which the products are pressed, and are burned at a temperature of 50-150 C lower than the briquette was made, i.e. at a temperature of 1550-175О S. Skoros The heating and cooling briquette is 600-1100 ° C, and the products 20-60 and tO-IOO C, respectively. The composition of the briquette mixture and the burning mode are shown in Table 1, and the properties of the products are given in Table 2.

Table 1

Comparative properties of products

Briquette water absorption,

Temperature. First deformation under load 2 kgf / cm, ° С

table 2

0.2 2.0

0.0

1650 - 1580.

1680

1720

Continuation of 1lbl. 2

Claims (1)

Claim A method of manufacturing refractories by briquetting a mixture of technical alumina and 3-20%. Clay component, firing the briquette, grinding and preparing the molding material, molding the product and firing them at 1550-1750 ° C and at a speed of cooling 20-60 and 40 100 deg / h, respectively, characterized in that, in order to reduce open porosity, linear shrinkage and increase creep resistance, the briquette is fired at 1700-1800 C, and the briquette is heated and cooled at a speed of 6001100 deg / h.