Possibilities are studied of reinforcing refractory objects and unmolded materials with carbon fibers produced domestically. It is shown that with specific treatment fibers are effectively distributed within refractory materials, they reinforce them efficiently, increasing strength and thermal shock resistance, and they remain in refractory objects and dense concretes up to a heat treatment temperature of 1600°C.The reduction in the specific consumption of refractories for a unit of basic product (steel, cement, glass, etc.) is moving along the path of improving the quality of refractories and the production of new, more resistant forms of refractories, replacement of small-piece refractory objects by unmolded refractory materials, with production and use of new refractories not requiring manual labor. Another worldwide tendency in the refractory market is more extensive use of carbon-containing materials and objects exhibiting a valuable set of properties from the point of view of refractory operation, i.e. high heat resistance and corrosion resistance to melts based on iron, and high mechanical strength. Recently a tendency has been observed in increasing the specifications for refractories and mainly for achieving quality uniformity even as a result of an increase in cost. One method for improving the quality of refractory materials is reinforcement.Reinforced materials are composite materials, within whose composition there is additionally a fiber filler distributed within the volume. In a number of properties, including ultimate tensile strength and shear strength, impact and fatigue strength, crack resistance, fracture toughness and thermal shock resistance, reinforced materials surpass traditional materials, and this ensures their high efficiency in applications.Reinforcement with a fiber changes the behavior of the matrix of a refractory as a component of a specific structure, and this makes it possible to create the required strength reserve, retaining structural integrity even after development hairline cracks. In addition, as a result of a combination of fiber and matrix the refractory forms an additional set of composite material properties, whose components do not exhibit them individually. In particular, presence of an interface between the reinforcing elements and the matrix markedly increases crack resistance and increases material resistance to spalling. Thus, in composites an increase in static strength leads not to a reduction, but to an increase in fracture toughness. For example, introduction of silicon carbide fibers (whiskers) into a bauxite mix in an amount of 2 -4 wt.% increases the fracture toughness from 1.3 to 1.9 MPa 1/2 [1].Introduction of filaments (fibers) into a refractory charge provides three-dimensional volumetric strengthening and an increase in material endurance, a reduction in shrinkage during heat treatment, as a result of which there is a significant increase in crack resistance and impact strength. Volumetric reinforcement of a refractory makes it possible to reduce the ...
The results of an integrated study of high-alumina slag generated in the production of ferrotitanium, ferrochrome, and metallic chromium by the aluminothermic method at the Kluchi Ferroalloy Works are described. The chemical and mineral composition and refractoriness of the main varieties of slag are identified. The prospects for application of refractory slag are considered.The Klyuchi Ferroalloy Works is the only company in Russia and the CIS producing over 30 unique ferroalloys and alloying compositions using the method of aluminothermic reduction of metals from oxides and other compounds. Aluminothermic reduction of metals (Me) proceeds according to the following reaction: 2/m Me n O m + 4/3 Al ® 2n/m Me + 2/3 Al 2 O 3 .Consequently, in contrast to all other ferrous and nonferrous metallurgical slags, aluminothermic slag (ATS) is based on silica whose average content in the slag is at least 60 wt.%. The purpose of this study was to determine the mineral composition, microstructure, and physicochemical properties of the main ATS varieties and to issue recommendations for their more extensive application.
Data on the chemical and mineral composition and properties of bauxite in Russia and across the globe are reported. The material composition is shown to be a central factor that controls high-temperature properties of bauxites -refractoriness and melting point.At present and in the near future, the main types of refractories for ferrous metallurgy manufactured on a commercial scale are oxide-carbon materials in the four-component system MgO -Al 2 O 3 -SiO 2 -C.The primary physicochemical parameter that determines the wear resistance of a refractory under heavy-duty operating conditions is energy density [1 -3]. The energy density D, kJ/cm 3 , is the total amount of energy which is required for complete destruction of a unit volume of material; it is defined as the ratio of the energy of formation (Gibbs energy change DG T 0 ) to the molar volume V:The MgO -Al 2 O 3 -SiO 2 -C system can provide a total of seven refractory oxide compounds with melting points from 2800 to 1710°C and a graphite with a sublimating temperature of 3800 -4200°C. The energy density and melting point of aluminum and magnesium-containing compounds show no correlation with the melting point (Table 1). Table 1 shows that alumina-containing compounds offer a clear advantage over their chemical analogs of magnesian composition in the calculated (theoretical) energy density, despite the lower melting point of the corresponding simple and complex oxides.The high energy density of alumina-containing materials bears direct relevance to their other properties of practical importance such as enhanced resistance to the corrosive attack by basic slags (except for high-calcium slags), inertness in reducing liquid and gaseous media, low thermal expansion, high strength and hardness, and other properties. Based on densely sintered corundum, a unique heat-resistant material -tabular alumina -has been developed for wide application; currently, this material has no analog among hightemperature magnesian refractories.There are good reasons to believe that further progress in the field will be achieved by increasing the use of corundum-containing high-alumina refractories at the expense of
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