G. G. Mel'nikova

Structure and electrical conductivity of polycrystalline silicon carbide

ConclusionsUsing the methods of optical and electron microscopy and EPR, we identified and determined the electrophysical characteristics of SiC′ and SiC″ in self-bonding polycrystalline silicon carbide. It was established that the relative content of SiC″ can differ from the content of the carbide-former depending on the prevailing mechanism of formation of SiC″ (reaction sintering or recrystallization). The temperature dependence of the specific electrical conductance (conductivity) of the fired polycrystalline silicon carbide materials was calculated in the 20–1500°C.

A study of protective plasma coatings

ConclusionsThe specimens covered with plasma coatings have a denser structure and finer pores as compared to the refractory products used as substrates. Plasma coating of the specimens improves some of their important service characteristics such as slag resistance and gas permeability.Based on the conducted experiments, it can be expected that the products covered with plasma coatings exhibit better service life under the conditions of corrosion and erosion action of reagents.

Structure of the calcareous gunite-coatings of the linings of converters

ConclusionsA study of the structure of the calcareous gunite coatings before and after bringing them into contact with a lime-fayalite melt showed that due to the effect of high temperatures, a dense refractory coating forms at the surface of the lining. The obtained coating corresponds to the lime-periclase refractories with respect to composition. It exhibits high slag resistance, thermal shock resistance, and mechanical strength and improves the service life of the converters. The optimum specific consumption of oxygen was determined for carrying out guniting.The obtained results form a basis for improving the properties of the calcareous gunite coatings of the converter linings.

Influence of addition of pyroxene raw material on the mechanical properties of aluminosilicate refractories

ConclusionsA qualitative interpretation of the results of mechanical tests of specimens was obtained and the influence of the structure of a refractory on its strength properties was confirmed. It was shown that addition of pyroxene raw material in a quantity of 5–15 wt.% to an aluminosilicate base makes it possible to increase the bend strength by 7–35% and the heat resistance by 2.0–2.5 times and to decrease the abrasive wear of the parts by 2–4 times.

Refractories from Verkhne-Shchugorsk bauxite deposits

Fabrication de briques refractaires a partir de ces bauxites, etude de leurs caracteristiques physico-chimiques

Reinforcement of periclase refractories with filamentary crystals of magnesium oxide

ConclusionsThe effect of additions of filamentary crystals of MgO on the properties of periclase specimens of a grainy structure has been studied. It is shown that the addition of FC of MgO makes it possible significantly to increase the thermal-shock resistance and strength of the specimens, including these characteristics at high temperatures, by comparison with the unreinforced specimens. The addition of MgO FC to periclase with a high concentration of MgO is particularly effective.

Making and testing refractories from high-density, high-purity magnesite powder

ConclusionsTest results for the trial batch of refractories made of dense magnesite powder in the converter lining in the trunnion zone showed that they are promising for application compared with ordinary dolomite goods with a pitch bond. The average wear of the test refractory is not more than 1.0 mm/heat, while dolomite-pitch shows a wear of 1.5 mm/heat. The resistance of blocks of dense magnesite powder in the lining of steel discharge apertures of a converter also proved to be higher than periclase (83 heats against 69).

Anisotropy of the structure of refractory products

ConclusionsA connection between the acoustic (propagation of ultrasonic vibrations) and the structural anisotropy of refractories has been established.Monitoring the anisotropy of the USV propagation velocity can be used to estimate the uniformity of the articles and the extent to which technological factors influence the structure-formation process.It seemed reasonable to study the connection between the structural anisotropy and the properties of the refractories which determine its behavior during service.

Fracture pattern of refractories in the system dolomite-magnesite based on a tar binder

ConclusionsIn a laboratory converter the wear of tar-bound refractories based on a dolomite-magnesite composition is due to fusion of the working layer. The service life of the refractories increases with their magnesium oxide content.

Phosphate binders in refractories for steelcasting

ConclusionsNozzles for steelcasting are more durable when produced with an aluminochromophosphate binder than with an aluminophosphate binder, the reasons being the more favorable conditions for the preparation of the batch and the state of the bond during firing and in the steelcasting process. Nozzles containing ACPB No. 2 binder should also be produced and tested on an industrial scale.