G. I. Kuznetsov

Effect of certain transition-metal oxides on the structure and properties of periclase-chromite refractories

ConclusionsThe solubility of the oxides of the transition metals in fused chromium spinellide decreases in the following order: iron oxide, manganese oxide, vanadium oxide, and titanium oxide. This series corresponds to the well known series [12] of increasing atomic volumes of the elements.When firing the periclase-chromite systems based on the chromium spinellides containing the oxides of the transition metals, the migration of these metals into periclase decreases in the following order: iron → manganese → vanadium.It was revealed that the addition of manganese oxide to iron-free chromium spinellide decreases its microhardness. However, in this case, the addition of manganese oxide does not affect the other properties of the specimens.

Effect of iron oxides on the service life of periclase-spinellide refractories

ConclusionsThe conducted tests showed that low-silica periclase-spinellide refractories having an excess iron content in the chromium-containing component are not suitable for use because of their rapid slag-induced chemical corrosion.In continuously operating metallurgical units where splitting of the lining due to the action of the slags is not a decisive factor, it is advisable to use refractories having the optimum content of iron oxides for the formation of a homogeneous spinellide matrix.In units operating cyclically under the most severe conditions (for example, in the ASEA-SKF type installations), the periclase-spinellide products in which the spinellide having the minimum content of iron oxides acts as a fused synthetic chromium-containing component are suitable since they exhibit the best high-temperature thermomechanical properties and stability.

Periclase-spinel products based on sintered materials for vacuum treatment of steel outside the furnace

ConclusionsA technology was developed for periclass-spinel, low-silica chrome-concentrate (SiO2 <1.5%) and sintered periclase (MgO 91–92%, SiO2 < 3%). As regards the resistance in the walls of the metal zone of circulation vacuum equipment, these refractories are not inferior to PKhP periclase-chromite goods made from fused materials.In the production of PShKh articles it is recommended that titanium additives be used to ensure sintering of the chrome-concentrate to a low porosity, and to stabilize the properties of goods made with it.It is desirable to make wider tests of these refractories in vacuum units of different types. The introduction of PShKh articles based on sintered materials in the walls instead of PKhP articles should reduce the consumption of scarce fused materials for vacuum treatment and cut the costs of the linings.

Refractories for vacuum degassing of steel

New equipment for outside-the-furnace vacuum degassing of steel includes argon-oxygen refining units, circulation flow vacuum degassing units, and units for steel degassing in the ladle with electric arc heating. The refractories developed for use in this equipment include magnesia, periclase-carbon, corundum, alumina, periclase-lime, magnesia-dolomite, forsterite, and unformed and vibrocompacted refractories. The refractories were selected for heat resisting and thermal insulation applications. This paper reviews at length the raw material base, production processes, and applicable properties of these refractories under degassing conditions, including slag and silicate resistance, temperature and phase behavior, permeability, compression strength, service life, and wear behavior. In addition, specifications are given for a wide range of refractories and their applications in specific pieces of equipment. Savings in refractory and power consumption are discussed.

Masses based on Arkalyk clay for guniting steel-teeming ladles

ConclusionsThe authors investigate the properties of gunite masses based on Arkalyk clays with regard to service conditions in steel-teeming ladles used in open-hearth manufacture of steel. The optimal composition of the mass is as follows: 90% chamotte, 10% clay, and 10% binder (above 100%). Industrial tests have been performed on a mass for guniting 230-ton steel-teeming ladles of the MMC. The durability of a gunite layer 30–35 mm thick is about 6 pourings. The results confirm that Arkalyk clay is a promising material for making gunite masses.

Influence of the quality of fused periclase on the properties of plates and their service in sliding gates of steel-teeming ladles

ConclusionsThe authors have established that the structure and properties of periclase inserts and their durability during service in the sliding gates of steel-teeming ladles depend on the chemical and mineral compositions, the structure of the fused periclase, and the procedure used to obtain it.

Experience gained in guniting of pouring ladles at the Magnitogorsk Metallurgical Combine

ConclusionsThe Magnitogorsk Metallurgical Combine has adopted guniting of the lining of 230-ton and 300-ton pouring ladles with chamotte-clay compounds, which are now being manufactured by its refractory sector.

THERMOPLASTIC AND THERMOPHYSICAL PROPERTIES OF MAGNESIA--SPINEL REFRACTORIES FOR STEEL VACUUMING INSTALLATIONS

ConclusionsThe authors have obtained the dependences of the thermoplastic and thermophysical properties of magnesia-spinel refractories for SVI on the tensile loads and the vacuum.The best thermomechanical properties are exhibited by MKhVP refractories, obtained on the basis of fused periclase-chromite material.At an air pressure of less than 6 mm in the refractory pores, the thermal conductivity and thermal diffusivity of magnesia-spinel artifacts increase with temperature.

Refractories based on fused pe riclase — Chromite material for vacuum steel refining plants

ConclusionsThe relevant technology was developed and production has started of high-quality refractories based on a high-density fused periclase —chromite material.The refractories are characterized by a low content in silica and silicates, well-developed direct bonds between the high-refractoriness minerals, and high indices for density, cold-crushing strength, thermal strength, refractoriness under a load, and in-vacuo stability to the action of slag and steel melts and the gases. The most favorable combination of properties was achieved when using starting materials of high-purity, fused periclase-chromite with a maximum grain size of 5 mm, batches with a low content of fine-ground components, high specific molding pressures, high firing temperatures, and long holding times at the peak temperature.The refractories are designed for the lining of the pipe, bottom, and walls of the chamber of equipment for vacuum steel refining and can be used with good results in the lining of converters, electric-arc and plasma furnaces, and other installations for melting high-temperature materials.

The wear of refractories of a fused periclase-chromite material in equipment for the batchwise vacuum refining of steel

ConclusionsAn investigation revealed an interrelation between the pattern of destruction of the refractory in the lining of BVRS equipment and its conditions of service. The severe spalling of the brick is caused by the formation and growth of open cracks in the intermediate zone of the refractory as a result of the abrupt changes in the mechanical loads and gaseous medium (from slightly oxidizing to reducing) and the additional stresses produced by the crystallization of the silicate melts in the cracks and pores of the refractory during the process of cooling and the consequent considerable shrinkage.The displacement of the primary high-refractoriness minerals by the low-melting components of the steel and slag melts promote the formation of relatively low-melting phases in the reacted crust (i. e., on the boundary between the refractory and the melt). The rate of the chemical erosion of the refractory depends on the total amount of these phases. This factor did not play a significant part in the overall pattern of the wear of the lining (in the first campaign).