Vol 58, No 2 (2017)

Among the range of many products is so-called “aluminum-free” steel within which the aluminum content is limited to thousandths of a percent. Normally during extra-furnace treatment of these steels it is prohibited to use material containing metallic or oxidized aluminum. Results are given in this article for industrial experiments pointing to the possibility of using a dilute alumina material maintaining a low aluminum content in steel and forming a phase in slag favorable from the point of view of using solidified slag in building.

Reasons for formation of large accretions are studied from results of work. A number of high-temperature refractories of magnesia composition are studied, exhibiting the least impregnation by melt reagents, high service temperature, and abrasion resistance. It is established that the most reaction resistant refractory is periclase-carbon fuzed refractory with an increased Cr₂O₃ content (PKhPP). A zone is selected for using PKhPP and combination of sections of PKhPP and PKhS refractories is established. PKhS and PKhPP refractory thermal conductivity is studied. Tests demonstrate absence of accretion formation in the reaction zone, and an increase in Waelz kiln lining life in the Ust-Kamenogorsk Lead and Zinc, and Leninogorsk Polymetal Combines by a factor of 1.6 – 1.8.

Insulating refractory bricks with different densities have been successfully produced from firing of sludge of water treatment produced from the water treatment plant at El-Kureimat power station (Giza, Egypt) and rice husk ash mixtures. Different batches from the sludge of water treatment (SWT) with varying amounts of rice husk ash (RHA) were well mixed, formed, dried, and finally fired at different temperatures ranging (800 – 1200°C). The filter pressed sludge was dried and fired at the same temperature range. The physico-mechanical properties of the fired specimens of sludge-rice husk ash batches and the filtered press sludge were investigated and evaluated. The results showed that the sludge of water treatment plant can be used successfully to produce high quality insulating refractory bricks for various thermal insulating applications.

Mechanochemical synthesis of titanium carbide via vibrational activation was limited by the carbon structural modifications resulting from pyrolysis of plant biomass and the ash content of natural graphite. Natural graphite and amorphous carbon modifications prepared from plant biomass were demonstrated to be promising for synthesizing titanium carbide with minimal sulfur contents.

The possibility is considered of preparing finely crystalline yttrium-aluminum garnet using high-temperature processes in solar furnaces. The effect of concentrated radiation heat flow density during treatment of a mixture of yttrium and aluminum oxides on phase composition of the melt obtained is revealed. The optimum radiation flux density for preparing specimens of finely crystalline single-phase yttrium-aluminum garnet is 8.4 MW/m².

Multi-wall carbon nanotubes (MWCNTs) reinforced Al₂O₃ composites (MWCNTs/Al₂O₃) have been prepared by a hot-pressing method, and the mechanical properties of the composites are investigated. Compared with the pure alumina, when adding 1.5 wt.% MWCNTs into the Al₂O₃ matrix, the composites have much higher flexure strength (403.6 MPa) and fracture toughness (4.21 MPa·m^1/2), which shows a simultaneous increase of 38% in flexure strength and 35% in fracture toughness. The microstructural observations of MWCNTs/Al₂O₃ composites show that MWCNTs are homogeneously dispersed and embedded strongly in the alumina matrix due to the electrostatic interaction between MWCNTs and Al₂O₃, resulting in great improvement of flexure strength and fracture toughness. The reinforcement mechanism of the composites is mainly the pullout of MWCNTs from the matrix, MWCNTs bridging and crack deflection.

Results are given for application of nanofilms (nanocoatings) to refractory material powders (diamond, boron nitride, silicon carbide, tungsten metal) by iodine transport. The method developed makes it possible to prepare coatings on powders with particle sizes from 10 nm to several microns, and on the surface of large objects. Coating thickness varies in the range from 1 nm to several microns. Composite materials are prepared from powder modified with nanocoatings of metals and their compounds, and the physicomechanical properties are studied that appear to be significantly better than for materials sintered from the same powders without nanocoatings. Potential areas for use of the composites obtained are determined from the results of work.

Results are given for a study of the effect of surface grinding regimes with diamond wheels on the surface condition of reaction-sintered ceramic based on silicon carbide (SiSiC-ceramic). The effect on machined surface is revealed for grinding depth, longitudinal and transverse feed on roughness, waviness, and morphology. It is established that a SiSiC-ceramic surface after grinding has an original morphological picture.

The effect of firing temperature of the properties of materials prepared on the basis of complex composition HCBS with a different Al₂O₃ and SiO₂ content is studied. Three typical isothermal firing temperature ranges are established for materials of all compositions: predominantly sintering or shrinkage (900 – 1200°C), predominantly mullitization, accompanied by growth (1200 – 1400°C), and mullitized material sintering (1400 – 1600°C). Comparative analysis is provided for material sintering and mullitization in nonisothermal heating regimes and with isothermal firing. It is established that even during heating to a prescribed firing temperature a marked reduction in porosity and considerable sintering or mullitization are noted.

An inorganic water-repellent coating based on quartz slip with alumochromophosphate binder exhibiting improved heat resistance and good physicomechanical indices is developed in AO ONPP A. G. Romashin Tekhnologiya. Technology is developed for applying a coating to specimens and composite material objects. Coating heat resistance is studied, and demonstrated in air above 1200°C. A marked reduction in porosity and moisture absorption of composite material with maintenance of dielectric properties is achieved in specimens and models.

Information is summarized and results are given for comprehensive study of the substance composition and properties of titanium-alumina slags. Research is conducted over several decades by both domestic specialists and authors of the present article. Chemical, mineral compositions, and ferrotitanium slag compositions are provided. Experience is reflected of utilization and prospective areas for use of ferrotitanium slag.

Methods are considered for preparing periclase-carbon refractories of “mini-key” (MK) format by compaction sideways and edgeways. Under OOO Ogneupor conditions objects are prepared with dimensions 102/113/160/200 mm that are installed edgeways in the lining of OAO MMK steel-pouring ladles. Objects demonstrate good life, there are no typical vertical cracks, and there is no erosion of horizontal joints.

Methods are described for producing aluminium-magnesium spinel by solid phase synthesis using commercial alumina and caustic magnesite. It is proposed to replace commercial alumina by dust deposited in the aspiration system for an aluminum hydroxide calcination rotary furnace that makes it possible to exclude the stage of milling alumina. Methods are provided for spinel synthesis in electric arc furnaces with block melting and pouring of a charge. The effect of the MgO/Al₂O₃ ratio in electrically melted material on its properties, method for adding a charge to an electric furnace during melting for pouring, features and properties of spinel materials with subsequent molded object sintering, are studied.

The field velocities near a round suction channel with funnel are determined by means of a newly developed iteration procedure for the construction of the free surface of a flow. A series of limiting trajectories of the dust particles are constructed and dependences of the ventilation coefficient on the length of the funnel and its inclination are constructed.