Volume 57, Nº 3 (2016)

Operation of a section CBCM steel-pouring ladle–tundish, and also questions of organizing steel flow movement in the tundish receiving chamber are analyzed. The considerable effect of new components of refractory structures on metal flow parameters in the tundish receiving chamber is demonstrated. Contemporary equipment of the receiving chamber provides effective formation of metal flow in the chamber and trouble-free CBCM operation.

Monoblock stoppers of different quality in metallurgical enterprises are analyzed and the effect of stopper material on metal pouring stability in a CBCM is demonstrated.

A simplex-lattice method is used for planning an experiment for sorting the grain size composition of high-alumina chamotte grade RASC in order to prepare mullite material. Optimum chamotte grain size composition is established proving an improvement in operating properties.

The structure of hardened CLCP-stone is studied using petrographic, x-ray structural, differential-thermal, chemical, and electron microscope methods.

are given for a study of the effect of introducing different amounts of graphite modified PFR and graphite into a periclase-carbon (PC) refractory charge based on fuzed periclase. The PFR modifier used is ÉTS-40, and the graphite modifier is a sol based on ÉTS-40 hydrolysate and 20% NiCl₂ solution. A production scheme is proposed for preparing PC-refractories with combined modification of components, and also a charge composition with 15 – 20% graphite demonstrating sufficiently good slag resistance.

Production features of micromachining ceramic workpieces using electrical-discharge machining are studied. The effect of pulse duration, breakdown voltage, voltage gain factor, peak current strength, and working voltage for electrical-discharge machining of VOK71 ceramic workpieces on roughness at the bottom of a channel and electrode-tool end wear are established. A mechanism is proposed for surface formation with electrical-discharge machining of current-conducting ceramic and recommendations are formulated for improving micromachining efficiency for components of this material.

For protecting a cathode block surface and a whole electrolyzer lining it is proposed to use boron and titanium compounds in the form of an active substrate of their carbides (TiC and B₄C) that under successive electrodeposition conditions with transformation and reaction transitions create a layer wettable with aluminum. Combined synthesis processes are studied for wettable coatings and the mechanism of carbide formation on carbon cathode surface layers. Possible processes of aluminum carbide formation with its transition into carboxide surface substances are suggested for discussion.

Results are given for a study of the mechanism of periclase wetting by coal-tar pitch. Features are revealed for pitch reaction with a periclase surface caused by differences in pitch chemical composition and conversion of components during thermal action.

The structure of permeable ceramic made from narrow-fraction electrocorundum grade F 240 and corundum hollow microspheres is studied using computer analysis of images obtained in a scanning electron microscope. Such quantitative indices are determined as pore shape, pore shape distribution, pore twisting factor, etc. It is shown that pore shape has a decisive effect on specimen permeability.

The effect of adding copper oxide in an amount of 0.9 wt.% on sintering capacity, microstructure, and phase composition of material based on zirconium dioxide stabilized with yttrium oxide is studied. Powder is prepared by reverse precipitation with ammonia from aqueous solutions. It is shown that in the presence of copper oxide there is formation of monoclinic zirconium dioxide, appearance of a liquid phase in the range 1120 – 1200°C, and a change in material color and porosity.

Industrial test approval is carried out in AO Magnezit Combine for Satkinsk magnesite separation technology using an x-ray transmission separator XSS(T). Favorable results are obtained with a “dry” enrichment method of x-ray transmission separation. A procedure is worked out for enriching magnesia raw material of different quality using magnesite (SiO₂ content not more than 1.1%; CaO not more than 2.1%) corresponding to specifications for producing standard grades of basic composition objects.

Dust formation in refractory production quarries and its danger for the health of service personnel are studied. Dust properties are provided in relation to particle size. Well-known methods are considered for collection of harmful dust and disadvantages are considered. A new means of transport is considered for high throughput using an air cushion for collection and transport of dust-forming loose materials under conditions impassable by land.

Models are considered for vermiculite heat assimilation and thermal conductivity during heating in electric furnaces with a “zero” module using the internal thermal exergy for mechanical transformation of its grains without an external heat source. Models are analyzed taking account of vermiculite fine fraction and inert material stored energy, and evaluation of their effect on heat assimilation and structure formation of coarser fractions.

The effect of repeated nonisothermal heating to 1500°C on shrinkage and crystallization of quartz ceramic with added alkali (0.5% Na₂O) and monolithic fuzed quartz is studied. Marked (up to 10%) tridymite formation is detected in specimens with added alkali and with a predominant cristobalite content. Some properties are provide for specimens after single-stage heating to 1500°C. Depending on additive content specimens have open porosity of 6 – 9% and ultimate strength in compression of 130 – 185 MPa.

Within the scope of a model for a viscous compressible liquid spatial dust and air flow in an aspirated shelter fitted with a rotary suction cylinder is studied. Structural and regime parameters are determined for a rotary suction cylinder effectively influencing a reduction in dust entrainment in an aspiration circuit.

The possibility is considered of using a hot-wire method (cross-array method) for determining heat insulation material thermal conductivity at high temperature. These tests show that different indices obtained by the hot-wire method and the steady-state standard do not exceed 12 – 15%.