In the construction of the core, the following must be taken into account: a downward taper of roughly 1-10% caused by the shrinkage of the ingot as it cools; the possibility of collapsing across a section if the core is squeezed when the ingot crystallizes; the possibility of independent movement relative to the immobile crucible when selecting the optimum level of installation of the core; and the use of screens to protect the pipes bringing water to the core since these pass through the zone of radiation from the melt.We melted shaped blocks under laboratory conditions in high-frequency equipment one of which had a power of 60 kW and a frequency of 5.28 MHz while the other had a rating of 120 kW at 1.76 MHz. In the first equipment we obtained rectangular mullite, corundum, and baddeleyite-corundum blocks of maximum section 200 • 220 mm and also pipe-shaped blocks and arched muffles of corundum with a maximum section of 220 • 250 mm and a wall thickness of 20 mm (Fig. 5). In the second equipment we melted blocks of magnesial spinel, forsterite, and mullite with a maximum section of 300 • 300 mm and length up to 1600 ram.In order to prevent descruction by thermoelastic stresses, the blanks were heat treated or cooled slowly. CONCLUSIONSIt is shown that the use of induction melting of oxide materials in a cold crucible makes it possible to achieve a high-productivity process for melting into blocks or with discharge for the production of fused material for industrial refractories and also to provide fused blanks for lining blocks and arched muffles.

In blast furnace production it is advantageous to use compact stoves with spherical checkers*, a subcupola temperature of 1550~ and a service temperature for the checkers in the upper layer of 1450~ diminishing over the height of the stoves, and also to use compact stoves with multilayer checkers made from refractories in temperature ranges corresponding to the service temperatures of each material.In connection with this, it has become necessary to develop a technology for granulated bodies based on aluminosilicate powders with various A1203 concentrations.Moreover, it is desirable to investigate the influence of the alumina's concentration of the s-form, which is determined by the grade of the alumina, and also by the method of treating the aluminum oxide for granulation, since the previously developed technology [i] is based on the use of scarce grade-GK alumina.The preparation of the starting materials, whose properties are shown in Tablel, includes vibrogrinding @ to a predominant grain size of minus i0 ~m.The specific surface of the powders, determined by the nitrogen-adsorption method, with the required grinding fineness (90% grains measuring less than i0 ~m) with an increase in the A1203 content in the alumina of various grades and high-alumina chamotte is increased (Fig. la). This is due to the better grindability of the alumina, which is connected with the marked brittleness of its particles, in contrast to particles of chamotte powders, which, because of the high content of glass phase, possess a higher impact strength. The specific surface of the powders is determined by the concentration of fine fractions (minus 5 ~m), which is seen from In [2] it is shown that the bulk density and angle of natural slope of powders significantly affect the densification of the material. The bulk density of powders was determined according to GOST 11035-64, pouring the powders through a funnel into the measuring metal nozzle of 1000-cm 3 capacity, the internal diameter of the nozzle being 45 mm. The angle of natural slope was determined by forming the powdered body in the shape Of a cone, for which the powder was poured through a funnel onto a flat surface; the cone was then measured with the aid of a protractor [3].During the process of granulation the granules undergo continuous densification, so we studied the influence of the bulk density and angle of natural fall on the granulation capacity of the powders and the resulting granules. Figure 2 shows that, with an increase in the specific surface of the powders, there is a reduction in their bulk density.Moreover, an increase in the content of A1203 in chamotte powders increases their bulk density (Fig. 3); the same is noted for spinel powders, although their bulk density is lower than that of chamotte powders, despite their higher true density. This is a result, firstly, of the somewhat greater specific surface, and secondly, of the peculiarity of the structure of the particles of alumina, including the presence of internal pores in the crystals.The powders were ...

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High-temperature heating of air and gases is a pressing problem in blast furnace production and a number of branches of technology. An increase in blast temperature in blast furnace production to 1400-1500 ~ makes it possible to save about 15 kg of coke per ton of iron melted. One of the methods of increasing blast temperature is the use in high-temperature hot-blast stoves of bulk spherical checkers the specific surface of which is i00 m2/m 3 with a sphere diam. of 20 mm.The first production test of a stove spherical checkers was made at Kosogorsk Metallurgical Plant, in which an experimental production block of stoves for No. 2 Blast Furnace was constructed and is in service. To provide the block of stoves of Kosogorski Metallurgical Plant with 680 tons of spherical checkers (340 tons for each stove) Belokamensk, Kazakh, and Krasnogorovka Refractory Plants have introduced the earlier developed method of production of corundum spherical checkers by the granulation method with participation of Ukrainian Scientific-Research Institute for Refractories [I].The equipping of these plants with different types of grinding and forming equipment and kilns for firing of parts made necessary some modification of the method (grinding, granulating, and firing of the granules) for the conditions of each plant.In the method developed for production of granulated corundum spherical checkers the original raw material is alumina with an a-Al20 a content of not less than 70%*. Types GK, GN-I, GN-2 (GOST 6912-74), and GKIS (TU 48-2853-310-81) alumina satisfy this requirement. The use of types G-00 and G-0 alumina (GOST 6912-74) is also possible with the condition that it is fired at a temperature of not less than 1550~In introduction of production of corundum checkers at Belokamensk Refractory Plant commercial grade alumina fired loose with simultaneous impregnation of it with magnesium chloride was used. The e-Al203 content in the fired alumina was 90-95% as compared with 25% in the unfired.After vibrogrinding of the fired alumina until obtaining finer than i0 Dm grains the forming mixture was prepared and it was granulated in disk granulators with a disk diameter of i000 mm. The granules were dried under natural conditions and fired at a temperature of not less than 1750~ in tunnel or batch kilns. In firing of the granules in 36 m long tunnel kilns uniformity of firing under the specified conditions was provided by channeling of the floor of the car and cutting of the lining on the car with gaps of 15-20 mm.The shrinkage of the granules in firing was 14-15%. To obtain granules corresponding in dimensions to TU 14-8-458-84 with Change No. 1 (type KN-20) the diam. of the green granules was increased to 25-26 mm. As experience in granulation of finely dispersed oxide powders shows, an increase in granule size leads to an increase in surface roughness of the spheres and the formation of a loose noncompacted surface layer. For compaction of the granules and the formation of a smoother surface the finished granules were finish rolled fo...