Vol 57, No 1 (2016)

This article examines the designs of sets of equipment installed in the discharge chambers of the tundishes on continuous section casters. Further refinement and practical introduction of the designs will effectively extinguish the eddies that form above the discharge nozzles and improve the quality of the castings by forming a well-organized stream of molten metal.

Astudy is made of local (pitting) wear of the working layer of a periclase-carbon lining in a steel-pouring ladle used in a ladle-furnace unit without vacuum degassing of the steel that is being treated. The main causes of this type of wear are evaluated.

Laser flashing and thermal analysis are used to determine thermal conductivity and linear thermal expansion coefficient of low density carbon-carbon materials based on two types of graphite foam differing in degree of graphite matrix defectiveness, and pyrocarbon. It is shown that density after compaction and not the ratio of carbon components has the main effect on thermal conductivity. Carbon-carbon material based on electrochemical graphite foam has low values of thermal conductivity λ = 0.5 – 2.0 W/(m·K) over a wide temperature range (30 – 900°C), whereas for specimens based on traditional graphite foam low values of λ are only typical at high temperature.

Results are given for a study of physicochemical processes occurring on heating synthesized antioxidant precursor, i.e., nickel oxalate salt. It is shown that after heating at 300°C NiO is formed that is an antioxidant. Salt before and after heat treatment at 300 – 500°C may be used as an antioxidant

Development of new highly efficient composite materials is an important area for effective activity of refractory enterprises. It is established that use of binder suspensions as both a mix component, and as an independent material, makes it possible to expand the field of developed material application. The efficiency of using corundum coatings increases heating unit service life.

Information is provided for chromium-containing refractory used in founding alkali-free borosilicate glass E. It is shown that melted and cast chromespinelid refractory KhPL-85 developed, containing 80% Cr₂O₃ with respect to corrosion resistance in molten glass E, is at the same level as industrial chromium oxide refractories.

A dependence is established for acid-resistant material pore structure on firing temperature and gas parameters. It is expedient to fire acid-resistant materials up to 1100°C in an oxidizing atmosphere, and at 1100 – 1200°C in a reducing atmosphere. With this regime firing provides an improvement for acid-resistant material pore structure.

Examples are provided of the efficiency of adding refractory clays in HCBS technology and ceramic concretes. Properties of castings prepared by slip casting based on HCBS of composite composition in bauxite – very fine quartz glass (VFQG), and additions of refractory clay (1 – 10%) are studied. The effect of continuous nonisothermal heating up to 1500°C on specimen linear dimensions is studied by means of a high-temperature dilatometer. Data obtained are compared with specimen apparent porosity after isothermal firing with soaking for 1 h in the range 800 – 1500°C. Maximum linear shrinkage with nonisothermal heating and minimum value of apparent porosity after isothermal firing correspond to the range 1200 – 1500°C. Maximum indices are noted at 1500°C for both specimen growth and also porosity due to occurrence of secondary mullitization.

The method of slip casting is used to make dense ceramic crucibles of cerium-doped alumo-yttrium garnet. Use of the crucibles to heat-treat this material does not lead to its contamination at temperatures up to 1600°C. A laboratory technology for making the crucibles is described.

Research is carried out on different types of artificial ceramic binders based on single-crystal and polycrystalline zirconia and corundum composition raw material. Features are established for composite compaction in relation to molding conditions and raw material type. The possibility is demonstrated of using these binders for preparing high density ceramic composites with improved operating properties.

The movement of charged dust particles of different sizes in an electrostatic precipitator is studied. It is found that such particles acquire different velocities before they are deposited in the precipitator. They differ significantly from one another in the curvature of their trajectories, which makes it easier to precipitate nanoparticles from the general dust-air flow. A unit is proposed for capturing the nanosized fraction of dust particles in the upward pneumatic transport of bulk materials during alumina production.

A technology for firing vermiculite conglomerates with a high content of inert material is examined. The firing operation is completed in an additional “zero” module by the internal heat accumulated in the conglomerate itself. Heat is transferred by radiation from particles of the inert material to the vermiculite granules inside the conglomerate. At the same time, heat is being transferred by conduction from the outer layers of the granules to their inner layers. Such a method of using recuperated heat makes it possible to mitigate the temperature regime of the electric modules, reduce the consumption of electric power, and decrease the energy content of the process.

are provided for a study of the effect of different graphites GÉ-1 and GCh (Russian Federation), Falke 94100 and Falke 9280 (Brazil), +592 (PRC), +595 (Madagascar), and FLS 897 (Norway) on physicochemical properties of periclase- and corundum-graphite refractories. It is shown that the type of graphite affects charge properties even in the preparation stage, and object physicochemical properties.

Current near a round local ventilation suction port in the form of a funnel situated above an impermeable plane is considered. Limiting trajectories of dust particles are constructed in the velocity field found from a new computer program and the capture coefficient as a function of the slope and length of the funnel and distance from the plane is determined. The geometric dimensions of the separation region at the inlet to the funnel as functions of the distance from the plane and the length of the funnel are determined.