卷 57, 编号 6 (2017)

A contemporary procedure is discussed for improving the structure of chromite-periclase refractory based on analyzing corrosive action of a reaction charge fired in aWaelz kiln. It is established that refractory wear during service proceeds by a frontal scheme through a series of successive transformations of the microstructure. On the basis of studying corrosion results for refractory objects of fayalite composition by slag manufacturing technology is developed for chromite-periclase refractories more resistant to Waelz material components.

An electron microscope and local x-ray microanalysis are used to determine quantitative and qualitative compositions of mullitized glass, i.e., the main structural element of ceramic providing finished object strength during research into compositions of pyrophyllite and aluminum containing nanotechnogenic raw material ceramic mix compositions.

There exist a number of different designs of furnace screens. In the case of high-speed smelting units, the most appropriate are cooled metallic caissons with refractory packing placed in tenons on the working side. A structural design of such a caisson employed in a glassmaking furnace of the future is presented in the article.

Amathematical model of the movement of moisture in refractory water-sealed materials of different densities where there is an external temperature field present is constructed. The Fourier thermal conductivity equations, Fick’s diffusion equation, and the method of finite elements are used to solve the problem. The diffusion coefficients of water in the test materials are determined by means of laboratory tests from the loss of mass in the course of drying of the samples. Features typical of the movement of moisture in refractory concrete for the case of deposition on cold and hot surfaces are determined as a result of a subsequent computational experiment, using as examples the casting bottom of a casting ladle and guniting of an intermediate ladle.

The problem is considered of including in the raw material base for manufacturing the main refractory products hydraulically mined economic minerals (quartzite, sandstone, refractory clay, kaolin, bauxite, sillimanite, serpentinite, bischofite, etc.). It is noted that the specific nature of hydraulic mining gives rise to the possibility of comprehensive use of natural raw material components and simplified preliminary preparation technology for use within the composition of refractory objects. A mechanized hydraulic device is proposed for mining economic minerals, effective for enriching and classifying sand and clay mixtures in flooded sand, and sand and gravel deposits.

Porous permeable ceramic is prepared from electromelted corundum (EMC) with fineness of about 0.5 mm with added porcelain. Compositions are prepared with different ratios of EMC/porcelain: 99/1, 97/3, 95/5, 93/7, and 90/10. Specimens in the form of bars with a size of 40 × 7 × 6.5 mm are prepared by uniaxial semidry compaction under a pressure of 25 and 50 MPa and fired at 1350 and 1450°C. Specimen open porosity varies from 22 to 30%, and ultimate strength in bending from 1.1 to 9.3 MPa. Porous ceramic is promising for filters and ceramic membrane substrates.

Certain principles for the construction of the diamond component of segments of a cutting and grinding tool for use in cutting of hard brittle materials, including refractories, are considered. Examples of constructions of segments designed for a particular function are presented. Principles for the construction of compound “smart segments” that exert additional effects in the cutting zone (besides cutting itself) which serve to adapt the cutting conditions to the tool are presented. Examples of cutting of different materials that demonstrate the universality and efficiency of the proposed segments are presented.

This article examines the effect of the structural parameters of isotropic and anisotropic pitch cokes that change with an increase in graphitization temperature on these cokes’ reactivity in relation to a silicon melt. The graphitization temperature at which the siliconized material is completely impregnated and contains the maximum amount of silicon carbide is determined for both cokes.

The phase composition for synthesized titanium carbide TiC and zirconium carbide ZrC powders is provided, and development of the crystal phases, microstructure, relative density, open porosity, true shrinkage, hardness, strength in compression of mullite–TiC–ZrC-specimens with a different ratio of TiC and ZrC sintered by a plasma-arc method in the range 1200 – 1500°C is demonstrated. Synthesized TiC and ZrC powders have intense crystallization of TiC and ZrC phases, and sintered specimens with a different ratio of TiC and ZrC have different mullitization in the range 1200 – 1500°C and degree of TiC and ZrC phase development at up to 1500°C. Above 1500°C there is development of TiC or ZrC phases in relation to the ratio of TiC and ZrC within sintered materials. Specimens with a higher TiC concentration have a denser sintered microstructure compared with specimens containing a greater amount of ZrC. This facilitates an increase in relative density, linear shrinkage and a reduction an open porosity, formation of harder specimens with uniform indentation impression without damage formation around it, and with the best strength indices in compression.

Formation and sintering of nanostructured Al₂O₃ and boehmite powders prepared by hydrothermal synthesis from aluminum powder are studied. Formation of workpieces (green bodies) is performed by extrusion, static and explosive pressing followed by high-temperature sintering. Use of explosive pressing increases raw material density, reduces the temperature for α-Al₂O₃ formation, activates sintering, and improves ceramic operating properties.

Possibilities are considered for using discrete carbon fibers as a reinforcing element within the structure of carbon-containing refractories. Results of laboratory and pilot plant tests are provided.

Results are given for a study of the microstructure, composition, and mechanical properties of ceramic based on silicon nitride prepared using three-dimensional printing technology and reaction sintering. In order to prepare workpieces of silicon powder an experimental three-dimensional printing unit is used, operating by binder injection technology. Synthesized specimens have high porosity and consist predominantly of α-Si₃N₄.

A method of nondestructive testing of the elements of a construction to which there is no direct access is presented. The method utilizes natural vibrations of the construction that have been excited by impacts of a special head of a hammer at specific spots. The method comprises a certain sequence that determines the position of the points of application of the impacts and measurements of the vibrations, the distribution of the frequencies of the vibrations by range, and the construction of a limited number of ranges of the spectrum of frequencies of the natural vibrations. The state of a controlled element of the construction is determined from the distributionof the frequencies of the natural vibrations in the spectrum. Results of experimental investigations of the inner jackets of eight nozzle heads by means of this method are presented.