Vol 58, No 5 (2018)

The lining of oxygen converters is a structural component, which requires permanent attention and significant investments in all metallurgical plants. These investments are connected with the necessity of application of high-cost refractory materials and with the expenses spent for the repairs of lining and relining, which strongly affects the cost of melting of steel. In this connection, in recent years, the metallurgical works all over the world try to find new efficient constructive solutions and improve the already existing technologies. One of these solutions is called the residual slag splashing technology.

Reasons are considered for crack formation in periclase-carbon, aluminopericlase-carbon and spinel-periclase-carbon refractories, and also partial effect on life of flux-cored wire and inert gas blowing intensity in enterprises smelting low-alloy, carbon, and low-silicon materials. The turnover of a steel-teeming ladle is more than 4 – 5 melts/day: the proportion of melts treated in FLU is 100%; open stream casting into a CBCM. Defining factors and the proportion of their effect on steel-teeming ladle life are evaluated from the results of this work.

The chemical and mineral compositions of periclase-chromite refractories used in the lining of the furnace for the processing of sulfide raw materials were investigated before and after the overhaul period. It was shown that dusty gas has an effect on the refractories composition and structure, causing saturation of the surface layer with both dust and gas components. Copper, zinc and lead penetrate the materials at a depth of up to 5 mm, whereas traces of elevated levels of sulfur associated with the formation of sulfates Fe₁₂S₁₁O₅₁, MgSO₄ and PbSO₄ were detected at 20 mm deep. Waste refractories can be used as lining at the non-critical components of thermal units and kilns, and as refractory powder to prepare gun mixtures.

Single-stage wet grinding is used to prepare composite composition HCBS based on bauxite, electrocorundum, and very fine fuzed quartz with a moisture content of 11%. Properties are studied for specimens fired in the range 900 – 1640°C. Depending on firing temperature T_fir three typical ranges are separated corresponding to primary sintering and shrinkage (up to 1200°C), mullitization and growth (1200 – 1400°C), and sintering of mullitized material (above 1400°C). The maximum value of ultimate strength in bending of 140 – 150 MPa corresponds to T_fir = 1250 – 1400°C and in compression 750 MPa at 1640°C.

Highly porous cellular material (HPCM) made from ceramic based on SiC is prepared with addition as a binder of 20% previously synthesized mullite with 1, 3, and 5 wt.% Y₂O₃ added (above 100% with respect to mullite). The HPCM was prepared by duplicating a matrix of foam polyurethane and sintering at 1350 and 1450°C and has open permeable porosity of about 95%. The ultimate strength in compression of the HPCM obtained did not exceed 0.15 MPa, and for sintered bars that simulate bridges it did not exceed 1.5 MPa. Strength increases with an increase in Y₂O₃ content and firing temperature.

Pelletizing of alumina-foam polystyrene mixtures is determined by presence of physicomechanical and physicochemical bonds. Decisive effects in this process are molecular and capillary forces whose value is determined by the individual properties of granulated material, layer structure, and amount of moisture. The hydrophilic nature of the test system surface and its hydrodynamic tendency towards pelletizing are established.

In an attempt to provide a new advanced carbide/nitride ceramic material with high sinterability and density for high-temperature and solar energy applications, this work inspected the effect of different sintering atmospheres on the processing of near-fully dense SiC/AlN ceramic composites. Several SiC/AlN (0 – 40 wt.%) composites were produced by pressureless sintering at a temperature of 2080°C for 2 hrs using a sintering additive of 2.5% yttria + alumina. Influences of argon/vacuum and nitrogen/vacuum atmospheres on the reaction response and the densification behavior of SiC/AlN composites were examined and analyzed. Results show that sintering of SiC/AlN ceramics in a nitrogen atmosphere increases mass loss of the different composites during sintering and leads to a decrease in their densification parameters. However, sintering in an argon atmosphere promotes both the sintering and densification processes, making argon atmosphere more convenient for sintering SiC/AlN ceramics. The use of SiC/AlN composites prepared by pressureless sintering is suitable for high-temperature applications.

Features of Si₃N₄-ceramic specimen edge morphology formation with diamond surface grinding are studied, and forms of chipping and geometric parameters are determined. On the basis of correlation revealed for grinding depth, horizontal and longitudinal feed with geometric parameters of chipping, a requirement is determined for planning a production process for manufacturing components and tools of Si₃N₄-ceramic taking account of edge defectiveness.

Data from a study of the resistance of volume-modified refractory components based on artificial ceramic binders of mullite-silicon carbide composition to the effect of melts of borosilicate glass and metallurgical slag are presented. Laws governing the variation of the wetting angle and degree of impregnation with melts of corrosive media as a function of the molding method compared to the comparable indicators of a factory prototype are established.

The use of vortex layer plants for dry grinding and regrinding of different powder-like materials (quartz sand, cement, micro-marble, chalk, dolomite, and diatomite) is considered. The high degree of efficiency of the plants is experimentally confirmed. Certain technological features of the process of milling of powder-like materials in a vortex-layer plant are established.

Scientific research work performed using titanium-alumina slag starting from the 1940s is reviewed. It is shown that use of titanium-alumina slag as a sintering additive makes it possible to improve the functional properties of various refractories, magnesite (periclase) powder, and some forms of refractory concrete. The slag serves as a secondary raw material or for TiO₂ preparation, and is also used successfully in manufacturing acid-resistant materials.

The important role of the volume concentration factor for HCBS in final material production and properties is accentuated. Taking account of experimental data and 30 years of experience of developing and improving quartz ceramics proposals are formulated for improving existing manufacturing technology for quartz ceramic rocket cones. The efficiency of using quartz ceramic and quartz sand suspensions as a components of high-alumina HCBS and materials based on them is demonstrated. Using composite HCBS of this composition multi-tonnage manufacture of molded and unmolded refractories is accomplished.

The effect of kaolin firing regimes on its properties are considered. Heat-treated specimens are studied by x-ray phase analysis, infrared spectroscopy, and gel pycnometry. It is established that the most active metakaolin (additive activity 360.5 mg/g) forms at 650°C and isothermal exposure for 30 min.

Asimplex-lattice planning method for an experiment is used to study the effect of periclase filler fraction composition on PC-refractory properties during whose production there is use of complex modification of charge components heat treated at 180 and 1350°C. The periclase filler fractional composition is optimized providing achievement of prescribed PC-material property indices for improving oxidation resistance due to creating Al + SiC + Ni(NiO) antioxidant from an organic-inorganic complex (–CH₃)–(SiO₂)_n–Ni(NiO)–C using inorganic nickel salt as its source.

On the basis of the hydrodynamical equations for the ejected and recirculated air flows in systems of loading telescopic tubes and bypass chambers, we propose a method for the evaluation of the flow rate of air entrained by the loose material and the required flow rate of aspirated air. It is shown that the energy consumption of the aspiration-technological units of telescopic plants can be significantly reduced by using coaxially arranged charging telescopic chutes with corrugated impenetrable walls placed around them and with the help of sealing of the neighboring upper and lower shelters.

Figure 5 is incorrect on page 423. The correct Fig. 5 appears here: