Том 58, № 4 (2017)

Equipment installed in the pouring chambers of the tundish of continuous section casters is considered. Improvements made to the equipment assure efficient formation of the metal stream and create conditions for increasing the quality of the metal.

Technology is developed for two-stage processing of secondary zirconium-containing mineral resource. A production scheme includes mechanical treatment of bacor waste and subsequent chemical leaching of impurities. The main processes in the first (mechanical) stage are crushing and selective grinding with separation of high-zircon concentrate (Al₂O₃–ZrO₂ system) and aluminum-zirconia product leaner with respect to ZrO₂ (R₂O–Al₂O₃–ZrO₂–SiO₂ system). In the second stage the latter are leached with a fluoric acid solution. The waste-free technology proposed for enrichment makes it possible to use valuable secondary resources entirely with preparation of two end products: enriched bacor refractory and a slag-forming mixture for steel smelting production.

Development and implementation of technology for manufacturing quartz ceramics for space rocket technology, and subsequently for casting steel, and refractories for other purposes are unique examples of high-tech domestic technology in the field of inorganic materials science. Distinguishing features of domestic technology of quartz ceramic manufacture are the high strength and reduced porosity of the original semiproduct that make it possible to achieve the required operating properties with a reduced firing temperature and insignificant shrinkage. Quartz refractories and engineering quartz ceramics have fundamentally different manufacturing technology.

It is shown that the production of light porous materials, such as porousized ceramic brick and porousized blocks with the use of depleted admixtures based on modified milled peat, can be useful. Acomparative analysis of the performance indicators of test samples and known analogs of porousized ceramic is carried out. Porousized bricks based on a newly developed composition may be fabricated not only at the level of existing analogs, but also with higher operating thermophysical indicators of the properties.

Porous permeable materials of electromelted corundum with fineness of 2 – 3 and 0.5 mm are prepared with a porcelain mix binder. Ratios in filler fractions 2 – 3 and 0.5 mm: 0/95, 35/60, 40/55, 45/50, 50/45, and 95/0. Specimens are compacted under a pressure of 24, 50, and 100 MPa and fired at 1350 and 1450°C. Sintered specimen ultimate strength in bending is from 1.9 to 15.3 MPa, open porosity 17 and 26%, gas permeability coefficient of single-fraction compositions from 1.19 to 3.27 μm². The porous permeable ceramic material obtained is promising for use in the form of filters and ceramic membrane substrates.

The results of investigating the effect of liquid glass fluid grouts based on rotten stone (tripoli) on the basic properties of slag-lime heat resistant concrete are given, with titanium magnetite refinement tailings being used as the aggregate. The influence of three types of slag cement-based fluid grouts was analyzed. The residual strength of the concrete (after exposure at 800°C) exceeds the initial strength, the thermal stability of the concrete samples depending on the type of fluid grout reaches 32 water thermal cycles. The results of the study show that the heat-resistant slag-lime concrete based on liquid glass and titanium magnetite refinement tailings are promising for practical application.

The minimum content of functional component (titanium borideTiB₂) in cathodic refractory material that provides wetting with molten aluminum is substantiated. It is established that total cathode wetting with aluminum is observed with some minimum content of TiB₂ in a powder composite (16 – 18 vol.%), when according to occurrence theory there is formation of an “infinite cluster”, i.e., a bonded percolation network of titanium boride particles. The volume of wetted composite containing a fixed amount (for example, 1 kg) of TiB₂ does not depend on its phase composition and porosity, but is determined by the diboride volume content. A TiB₂ content in the range 18 – 20 vol.% should be considered the optimum that creates reliable continuous wetting of a composite surface.

The phase composition of synthesized TiC and TiN, microstructure, relative density, open porosity, linear shrinkage, elasticity modulus, Vickers hardness, ultimate strength in compression, and linear dependence of elasticity modulus and ultimate strength in compression of mullite–TiC–TiN-specimens with a different ratio of TiC and TiN sintered by a plasma-arc method in the range 1200 – 1600°C with a compaction load of 30 MPa, are studied. Synthesized powders have intense crystallization of TiC and TiN. Sintered specimens with a different ratio of TiC and TiN demonstrate intense mullitization in the range 1200 – 1600°C. Specimens with a TiC/TiN ratio of 50/50, 70/30, and 90/10 mol.% demonstrate a gradual increase in TiC from 1200 – 1400°C compared with a more intense increase in TiC from 1400 to 1600°C. An increase in TiC concentration and a reduction in TiN content in powder mixtures sintered at 1500°C facilitates formation of a uniform density sintered microstructure with presence of small pores. Specimens in the ratios TiC/TiN of 50/50 and 70/30 mol.% point to a more intense increase in relative density and linear shrinkage; a reduction in open porosity and an increase in elasticity modulus, Vickers hardness, and ultimate strength in compression. This leads to an increase in specimen crack formation resistance in the presence of microcracks with a relatively rectilinear propagation trajectory (composition M50TiC50TiN), and absence of microcracks (composition M70TiC30TiN) around an indenter impression, with the greatest linear dependence of elasticity modulus and ultimate strength in compression in the range 1200 – 1600°C.

Spectral (in the wavelength range of 1 – 25 μm) and total emissivity of reaction bonded silicon nitride were determined together with their temperature dependence in the range between room temperature and 1573 K. The influence of ytterbium oxide and nickel impurities on the optical properties of the material was investigated. Emissivity was determined from the total reflectance spectra at room temperature, the diffuse reflectance spectra at temperatures up to 1173 K, and by monochromatic radiation pyrometry, and measurement results were compared.

HCBS of composite composition are prepared by combined wet grinding using fuzed corundum-bauxite containing 93.4% Al₂O₃ (45%) and sintered Chinese bauxite (45%) as basic materials. The additional component within the composition of the milling charge is very fine quartz glass (10%). The effect of firing temperature in the range 900 – 1600°C on material sintering and mullitization is studied. Values of ultimate strength in bending of 150 MPa are achieved after firing specimens at 1200°C. The material sintering (shrinkage) and mullitization temperature ranges are established.

Problems that arise when attempting to establish a correlation between the specific energy capacity achieved in firing of vermiculite and the size grades of its raw concentrates are considered and efficient operating regimes of electric furnaces with vibrating bottom platform are identified. The temperature – time relationships are analyzed and the productive capacity and thermal power calculated for firing of vermiculite concentrates of different size groups. Based on empirical data, it is concluded for the first time that the specific energy capacity is independent of the particular size group of one and the same concentrate. It is shown that the quality of swollen product does not change if the furnace is set for a reduced temperature regime, while at the same time an additional 40% energy savings is achieved with this step, leading to the least possible specific energy capacity of the firing process (46 – 48 mJ/m³).

Results are given for the synthesis and co-existence of phases formed from components of complex organic-inorganic antioxidant formed during modification of phenol-formaldehyde resin (PFR) and graphite with silica alkoxide and inorganic or organic nickel precursors. Thermodynamic analysis is given for the Mg–Al–C and Mg–O–Ni–C systems. It is shown that the periclase and carbon can coexist with aluminum and nickel, and also that oxidized antioxidants Al₂O₃ and NiO can interact respectively with the periclase and with the synthesized SiC formed during modification of PFR with silica. In considering the NiO–MgO–Al₂O₃–SiO₂ system it is established that during service noble spinel will be synthesized from the complex antioxidant components, facilitating an increase in PC-refractory durability in service.