The mixture for the manufacture of refractory products


C04B35/567 -

 

(57) Abstract:

Usage: the invention relates to refractory industry, in particular to techniques for the manufacture and operation carpetcleaningmiami shaped refractory products, such as melting crucibles. The inventive composition for the manufacture of refractory products, including silicon carbide, refractory clay, alumina, aluminium oxide and kaolin, further comprises aluminium oxychloride and oxide of rare earth metal from the group of La2O3Nd2O3, Gd2O3in the following ratios, wt.%: silicon carbide 32 - 40, refractory clay 13 - 20, alumina 15 - 25, electrocorundum 10 - 17, kaolin 3 - 15, aluminium oxychloride 0.5 to 4.5 oxide of rare earth material is 0.5 to 4.5. The invention allows to increase the life of the product by increasing their resilience in the face of impact melts of metals based on Ni or Co with repeated heating and cooling by improving the structural and physico-mechanical characteristics of the material. table 2.

The invention relates to refractory industry, in particular to techniques for the manufacture and operation carpetcleaningmiami refractories, and can be used for the safety shrouds, casting funnels and others, working in contact with molten metals, Nickel-based or cobalt.

The known composition of the charge on the basis of silicon carbide, refractory clay, alumina, oxide, and oxide or slurry of oxide doped with chromium oxides and titanium with a grain size of 0.01 0.20 mm [1]

In this material during sintering, the formation on the surface of grains of silicon carbide, including immediate contact with molten metals, layers enriched in large crystals of corundum. The growth in the number of open pores in the first channel, violates the integrity of the structure of refractories and increases the permeability of the membrane around the grains of silicon carbide. Thus, although the introduction of the doped oxide or slurry of the oxide provides the relative stability of the strength characteristics of products in operation, the presence of impurities of oxides of titanium and chromium leads to the reduction of corrosion and erosion resistance of the products in relation to the molten metal on the basis of Nickel and cobalt by increasing the rate of diffusion of the melt through the protective layer, and education in the layer structure compounds have the Vanir, first of all, for making agrarias and are not designed for operation in conditions of exposure to metal melts and rapid temperature changes.

Closest to the invention is a composition for the manufacture of refractory products, including silicon carbide, refractory clay, alumina, aluminium oxide and kaolin [2]

The additional introduction of the charge, as provided for in this invention, the battle of glazed porcelain and scrap kapseli to increase mechanical strength and turnover of products with a simultaneous reduction of the material leads to an increase in the content of impurities and the formation of low-melting eutectics, as well as to the heterogeneity of the chemical composition by volume of refractories, which degrades the properties of these refractories factor chemical resistance to molten metals, Nickel-based and cobalt and their thermo-mechanical characteristics, primarily the resistance; this ultimately leads to the destruction of the product during operation. This material is also not resistant to the molten metal during the casting and melting.

Known use in the manufacture of ceramics and refractories soluble aluminum salts which Finance product raw but as a result of thermal degradation (decomposition) are supplied to the reaction zone components in the active form (Al2O3), which should facilitate the sintering process. However, in mixtures of kaolinite-aluminium oxychloride having some difficulties education secondary mullite, due to lack of homogeneity of the initial mixtures, which slows down the reaction between SiO2and Al2O3made by kaolinite and oxychloride, respectively. In addition, linking oxychloride in mullite hampered by turning it in-Al2O3below 1200oC - the temperature of the beginning of intensive mullitization.

The objective of the invention is to increase the lifetime of refractory products by increasing their resilience in the face of impact melts metals Nickel-based or cobalt during repeated heating and cooling by improving the structural, physical and mathematical characteristics of the material.

This object is achieved in that a mixture comprising silicon carbide, aluminium oxide, alumina, refractory clay and kaolin additionally injected aluminium oxychloride and oxide of rare earth metal from the group of La2O3
refractory clay 13 20

alumina 15 25

oxide 10 17

kaolin 3 15

aluminium oxychloride 0,5 4,5

the oxide of rare earth metal 0,5 4,5

Simultaneous supplementation of oxychloride, which is when the heat goes into ultra-fine aluminum oxide, and oxide of rare earth metal increases the activity to the sintering of the original powders, resulting in reduced open porosity of the material and reduction of the hydraulic pore size. As a result, and also due to the formation of a layer containing crystalline phases and solid solutions on the basis of aluminum oxide, aluminates and silicates of rare earth metal and having a high chemical resistance to Nickel - and cobalt containing melts and reduced porosity, increased erosion and corrosion resistance of refractory products in the process of melting or casting.

At the same time, with thermal Cycling in the volume of the material due to the difference in coefficients of thermal expansion of coarse - and fine-crystalline phases at grain boundaries is formed layered microresistivity structure, providing the localization of nascent tensions sharp heating and cooling of the refractory materials.

Refractory products can be manufactured by casting, plastic forming, pressing or any other method, followed by firing in an oxidizing atmosphere before the formation of the sintered material.

In more detail the technology of manufacturing of refractory products in the form of the crucible illustrated by example.

Example. Ball mill loaded kaolin 10 wt. refractory clay 15 wt. alumina 20 wt. aluminium oxychloride 2.5 wt. the oxide of gadolinium 2.5 wt. and added water. The ratio of raw materials, high alumina balls was 1:2. The grinding was carried out for two hours at a relative humidity of suspension 58-60%

Pre-mixed separately from the fine-grained materials silicon carbide in the amount of 35 wt. fractions N 40 (20 wt.) and N 20-25 (15 wt.) and electrocorundum No. 6 in the amount of 15 wt. was added to the aqueous suspension and conducted joint stirring for 30 min at a relative humidity of slip about 40% of the Time was 18 19 sec.

The formation of the products was carried out in plaster molds "drain" injection molding method. After extraction of semi-finished products made of plaster moulds he was subjected to drying in natural conditions in air or in a drying furnace at a temperature of 65oC for 60 h

At tenfold remelting in a single product alloy composition 20Cr-13Mo-Ni chemical interaction of the material of the crucible with the melt were observed, which was confirmed by the lack of increase in oxygen content and inorganic impurities in the alloy. The crucibles were sustained temperatures of 20oC to 1450oC without failure. Products obtained by the prototype was destroyed in a single melting during the tests in the same conditions.

Used in the charge to the oxide of neodymium and lanthanum have properties identical to the oxide of gadolinium, and show them in the same manner as in the manufacture and operation of the refractories.

The increase in the content of oxychloride and alumina and a reduction in the content of the oxide of rare earth metal for the boundary values leads to deterioration of thermomechanical characteristics of products and a sharp decline in their metallostroiteley changes in the optimal phase composition chemically resistant layer on the surface of the refractories and improve its wettability by molten metals, Nickel-based and cobalt.

The decrease in the content of the oxychloride, kaolin and alumina and the structure of the porosity and permeability of the protective layer, increasing, thus, the degree of erosion of refractories by molten metals and reducing the service life of the products.

The mixture for the manufacture of refractory products, mainly melting crucibles, including silicon carbide, refractory clay, alumina, aluminium oxide and kaolin, characterized in that it further comprises aluminium oxychloride and oxide of rare earth metal from the group of La2O3Nd2O3, Gd2O3in the following ratio, wt.

Silicon carbide 32 40

Refractory clay 13 20

Alumina 15 25

Oxide 10 17

Kaolin 3 15

Aluminium oxychloride 0,5 4,5

The oxide of rare earth metal 0,5 4,5

 

Same patents:
Up!