During service most refractories undergo chemical reaction with corrosive agents (usually with a liquid phase). The kinetics of this process, for certain chemical compositions of the refractory and liquid phase, and for a given working temperature, are determined by the structure of the material. The influence of the refractory's structure follows directly from the fact that its solubility obeys Fick's law, in which the magnitude of the surface of the reaction is directly connected with the structure of the refractory, and is understood as the total surface of the refractory reacting with the melt. For each individual case, it should depend on the volume and size of the pores in the refractory and on the capacity, of these pores to absorb the melt.The resistance of the refectories in contact with liquid phase depends also on the rate of suction (capillary impregnation) of the melt and the solution of refractory in it. From the theory of capillary suction in a porous body for laminar flow of a liquid in a viscous schedule, it is known that the depth of movement of the melt is described by the expression (ignoring the force of gravity) [1]:where I is the depth of penetration, K is a constant of the rate of penetration, and ~" is time.Furthermore, the mass of dissolved refractory, due to the reaction with the melt, depends on the process occurring with minimum rate. In fact, if the solution rate is high and the penetration rate is low, then the wear rate in the refractory is determined by the latter process. Conversely, if the rate of penetration is high and the solution rate low, then the decisive rate of the process is the rate of solution. Since in practice, in most cases the worn refractory has a working zone impregnated to a certain depth, the wear should be determined by the solution rate.The total volume of melt Q penetrating the refractory, according to Zagar [2], is calculated from the equation:where A is the area of the section of the specimen in the direction perpendicular to the impregnation front; K is a coefficient; Fief f is the effective porosity; reff is the effective pore radius; 3, is the surface tensionofthemelt; ~ is the viscosity of the melt; 0 is the wetting angle; and ~-is time. Equation (1) is suitable only for the qualitative evaluation of the impregnation process, since refractories have complex structures and pore-size distributions. However, in practice it is simpler to regulate the penetration through the structure factor (IIeff2reff) '/2 than by the others. With a reduction in the open porosity and pore size, there is a fall not only in the magnitude of the structure factor but also in the numerical value of the remaining factors, since the behavior of the melt in capillaries of large and small diameter is not appropriate, and according to Strelov [1] metallurgical slag does not enter into capillaries measuring less than 5 txm.In practice the open porosity of the refractory is more often reduced, and the pore sizes more rarely reduced. The latter react with the grain composition of the...

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Dunites from the Kytlymsk (lovsk) deposits, which in mineral composition are actually olivine rock [i], are of substantial interest as a raw material for magnesia--silicate refractories.Using these dunites would contribute to the extension of the raw-material base for the production of forsterite articles and would improve their quality.The main physicochemical, thermal, and other properties of these dunites were studied previously [2][3][4]. The studies showed that the use for the manufacture of forsterite refractories of dunites with a low degree of serpentinization, and hence with a low loss on calcination, yields high-grade articles without preliminary calcination of the raw materials.A project was developed for a production schedule for forsterite articles from unca!-cined Kytlymsk dunites in the refractories division of the Nizhnetagilsk metallurgical combine [3]. Separate batches of industrial specimens of forsterite goods which fully met the requirements of GOST 14832-79 were made.This article gives the results of industrial tests in the lining of heating units at the Verkh-lsetsk factory, using experimental forsterite articles that were made without precalcining the raw materials.The test batch weighing i0 tons was made at the experimental factory of the East Institute of Refractories using industrial samples of Kytlymsk dunites supplied by the planning office of Uralgeologiya~The output of articles measuring 230 • 115 x 65 mm was done in accordance with the technological schedules [3]. The articles satisfied the demands of GOST 14832-79 (Table i).The goods were tested in the overflow (pouring) and main ladles of the electric furnaces, and also in the "false" walls of the slag chamber of the open-hearth furnace in the steel melting shop.When the tests were being carried out in the DSP-25 electric furnace, transformer steel was being melted.The pouring process consisted of the following: liquid metal was poured from the furnace into the overflow (20-ton capacity) and partly in the main (30-ton capacity) ladles; then the metal was poured from the overflow ladle into the main one; since a layer of synthetic slag forms in the main ladle on the surface of the metal with a basicity of from 1.7 to 2.6, then during passage through it metal jets were additionally cleaned to remove harmful impurities. The dwell-time of liquid metal in the overflow ladle was 15 min, and in the main ladle 40 min.The wear of the lining in the steel-pouring ladles is mainly due to the sudden thermal shocks, and also the chemical and erosive effects of the liquid metal and slago When the tests were done in the overflow ladle it was lined with experimental forsterite articles in only the two upper courses, and the remaining part w~th the chamotte refractories that are normally used. The life of the lining was 35 heats (average for the shop), and in this case the residual thickness of the experimental and chamotte articles came within the range 60-70 and 40-50 mm, respectively.The working layer of the lining of the main ladle was made wi...

A significant number of studies [1][2][3][4][5] deal with the synthesis of products in the MgO--Cr203 system; these studies describe the synthesis from the original materials based on pure oxides and also the effect of the disperseness of the original materials, their ratios, the method used in the preliminary preparation, and the addition of various oxides on the mechanism and kinetics of the synthesis and the sintering and recrystallizatiDn of products in the MgO-Cr20s system.The most complete mutual distribution of MgO and Cr203 can be obtained chemically by the use of soluble compounds. The method used to obtain synthethic materials in the MgO-Cr203 system is based on the interaction of caustic MgO with chromic anhydride [6].

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