L. Ya. Pivnik

Possibility of the Industrial use of forsterite products from Kytlymsk dunites

ConclusionsDunites from the Kytlymsk deposits are of considerable interest as a source of raw material for the production of forsterite refractories.Experimental forsterite articles, prepared without prefiring of the Kytlymsk dunites, completely satisfy the requirements of GOST 14832-79.Industrial tests established that the forsterite articles are suitable for use in the lining of steelcasting ladles, and also as facing material for the “false” walls of the slag pockets of open-hearth furnaces.

Phase changes in fused oxide refractories in contact with semimild and stainless steels and their slags

ConclusionsThese studies show the significant reaction resistance of the articles made from electrocorundum to 20 sm steel and its slag. The slag and oxidation products of the 20Kh23N18 steel penetrate the articles made from grainy electrocorundum to a greater depth, causing the corrosion of the corundum grains.In the case of the fused silicon-containing periclase articles, the thickness of the least-changed zone, like the concentration in it of the basic phase (periclase), is significantly larger after the interaction with the 20Kh23N18 steel than with the 20 sm steel. As a result of the interaction with the oxidation products of the 20Kh23N18 steel, the appearance of a solid solution MgO-NiO can be seen in the periclase articles. The articles made from fused zircon-containing periclase can be recommended for industrial use in contact with a high-alloy, heat-resistant (stainless) steel while those made from electrocorundum are recommended for use with a semimild steel, e. g., in continuous casting with mechanical treatment on the liquid phase.

Wear of magnesia spinel refractories in portion vacuum-processing steel plant

ConclusionsThe processes of wear in the lining of vacuum chambers of outdoor-furnace vacuum-treatment plants (UPVS) are due to the simultaneous action of high temperatures, deep vacuum, gaseous medium, molten metal, and slag. The corrosion and erosion of aggressive melts of slag and metal are the decisive forms of wear.Laboratory investigations established the relationship between slag resistance in vacuum and the ratio of corrosive and erosive constituents in the wear of different magnesia-spinel refractories and their phase composition, structure, and properties.Refractories obtained from fused periclase-chromite material with a low content of fusible silicates showed that in laboratory vacuum equipment and during service in the linings of the vaccum chamber of industrial plant they have higher slag resistance and lower wear than refractories based on sintered magnesite, spinel, and chromite ores.

Physicochemical processes in the linings of pellet-roasting machines

ConclusionsThe authors have investigated processes taking place in the lining of pellet-roasting machines at the NMBC. To ensure steady operation of the linings of the forward flow manifold, cooling zone I, and the gas-air chambers, they must be made of materials resistant to iron silicate melts at elevated (1200–1500°C) temperatures. Exceeding of the working temperatures in the manifold and branch connections (above 800°C) is due to “inverting” of the cone and its entry into the branch connections of the hearth.Taking account of experience gained in the use of OK-306 roasting machines at the NMBC, and on the basis of the results of our investigations, we can recommend refractories with an elevated A12O3 content for lining the hearth and manifold.However, the progress of roasting and the operation of the refractories must be constantly monitored; the principal criteria for the latter must be the flow rate of the gas and the temperature at the boundaries between the refractory and the heat insulation, and between the refractory and the gaseous working medium.

Refractory wear in sliding gates of steel-teeming ladles

ConclusionsAs a result of chemical and petrographic investigations of periclase and corundum plates and collectors, tested in sliding gates of steel-teeming ladles, the authors have established the disintegration mechanism of refractories and given a comparative estimate of their wear.The different zone-formation characters, chemical-mineralogical, and structural changes of the working zones of the refractories indicate that periclase plates are more durable than corundum ones during teeming of metal with a high temperature (more than 1600°C) from large ladles, and also when the gate is in the closed position for the least possible time.Corundum plates exhibit negligibly small wear during teeming of metal with a lower temperature (1580–1590°C) from ladles holding no more than 140 tons.

Porosity, apparent density, and structure of dinas blocks after heating

ConclusionsIt was established that no functional relation exists between the porosity and apparent density of dinas blocks and the temperature to which the blocks are heated. These properties can therefore not be used as criteria of the temperature reached by individual specimens cut from a block heated to a given temperature.The structure of the block undergoes appreciable compaction during the heating process.

The sintering of neodymia

ConclusionsAn investigation of the sintering process of neodymia in vacuo and in air showed that using industrial grade neodymia powder and firing the specimens in vacuo at 1800–1850°C gives a well sintered ceramic of relative density 0.96–0.98 for a true porosity of 1–1.5%.

Chamotteless ladle brick from primary kaolin

ConclusionsA technology was developed for producing semiacid chamotteless brick from fine-grained semidry batches processed from primary kaolin.The proposed method of molding gives a semiacid product with an open porosity of 18–20% and a finegrained structure which in service confines the interaction with slag to the surface of the refractory and thereby produces evenwear. Tests with ladle brick of an open porosity of 18–25% in 110-ton and 300-ton steel-making ladles showed that it is as durable as high-chamotte brick. In 25-ton ladles brick with an open porosity of 18–20% proved to be slightly more durable than high-density high-chamotte brick.The lower materials and processing costs in this technology give a saving of about 10 rubles per ton refractories.The technology of producing chamotteless products must be refined with a view to increasing the density and improving the structure of the brick.

Properties of aluminophosphate concretes containing various types of orthophosphoric acid

ConclusionsThe type of orthophosphoric acid has the maximum influence on the properties of corundum concretes, a lower influence on high-alumina concretes, and practically no influence on quartz-clay concretes. It is desirable to use wet-process orthophosphoric acid for refractory concretes. The excellent properties of concretes in the system A12O3-SiO2 based on this acid which is also cheaper enabled us to recommend it for preparing refractory concretes.The advantage of using H3PO4 of various types for corundum concretes is determined by the requirements placed on them in actual working conditions.

Effect of phosphoric acid concentration on some properties of finely milled refractory materials

ConclusionsThe concentration of phosphoric acid seriously affects the setting, weakening, and sintering of the finely milled refractory materials.Increasing the acid concentration boosts the setting rate of alumina, MgO·Al2O3, chromite, electrocorundum, dunite, and dinas, but hardly affects the setting of MgO, Cr2O3, magnesite, zircon, and quartzite.The materials that were studied are almost unaffected at 800°C. Increasing the concentration of H3PO4 improves the sintering of alumina, MgO·Al2O3, chromite, zircon, and dinas, but impairs the sintering of MgO, Cr2O3, magnesite, electrocorundum, dunite, and quartzite.