Volume 56, Nº 5 (2016)

New equipment that has been installed in the pouring chambers of continuous-caster tundishes is discussed. The equipment upgrade ensures efficient formation of the flows of metal in the tundish and creates the conditions necessary to improve its quality.

The use of a technology for the plasma deposition of bulk ceramic products to make permeable diaphragms with channel porosity is described along with the results that have been obtained.

Power-driven covered apparatuses in the production of ceramic articles, vapor-curing chambers for stimulating hardening of concrete, in reclamation of depleted land containing clay materials for use in the construction industry, and in growing farm crops on clay soils are proposed. A description of the structural features of a power-driven covering apparatus is given. The physico-mechanical properties of polymer films and comparative data on their basic properties are presented.

The requirements and service conditions of the refractories used to line rotary kilns in the cement industry are examined and possible ways of using them more efficiently are discussed. Results obtained from an analysis of the durability of the linings and the properties of the refractories are used to propose a new classification for the factors that affect the service life of rotary kilns in the cement industry.

Results are provided for development of optimum technology for preparing periclase-carbon refractory (PCR) by introducing carbon and antioxidizing agents into periclase refractory in different ways, i.e., pressing or vacuum impregnation with coal tar paste. Lining zones are determined within which use of PCR is rational. PCR refractories are tested and introduced into the slag belt of a reverberatory furnace in the Krasnoural Copper Smelting Combine, and KhPT refractory impregnated with carbon paste is introduced into the lining of Chelyabinsk Electrolytic Zinc Plant and Ust’-Kamenogorsk Lead-Zinc Combine Waelz kilns. Use of this lining increased a unit campaign by 40 – 45%.

Powder mixtures are considered containing ammonium hydrophosphate and calcium carbonate intended for preparing biocompatible porous ceramic in the CaO–P₂O₅ system. Pore formation on heating in workpieces based on the powder mixtures in question occurs due to occurrence of gas liberation in the presence of melt in the NH₃–H₂O–CO₂–CaO–P₂O₅ or CO₂–CaO–P₂O₅ systems. Gas phase formation is due to liberation of gaseous water and ammonia, thermal hydrolysis of calcium polyphosphate, decomposition of calcium carbonate, and oxidation of carbonized organic compounds remaining within a powder mixture in the form of associated calcium carbonate synthesis reaction product.

Aconnection is established by experiment of air-abrasive production parameters with the surface morphology of VOK71 cutting tips made of oxide-carbide ceramic. Features are revealed for ceramic surface formation in this process and mechanisms participating within it. High efficiency is demonstrated for air-abrasive treatment in order to improve ceramic object operating properties.

A comparative analysis is made of certain types of ceramic products and the processes that are chosen to make them in order to ensure that they have a certain level of physico-mechanical properties. Some of the features and capabilities of hot casting are examined in the fabrication of high-porosity and high-strength thin-walled ceramic products of complex shape. Results are presented from experiments and studies of ceramic specimens made by hot casting. It is shown how the strength properties and open porosity of the ceramics change in relation to the parameters of the production process.

This article describes features of the manufacture of high-porosity silicon semifinished products in the form of hollow cylinders by the warm centrifugal casting of elements obtained from cutting up castings of a silicon-based thermoplastic slip. Silicon nitride obtained by plasmochemical synthesis is added to the slip to impart the necessary rheological properties. Products in the form of hollow cylinders with walls made of a highly porous silicon nitride material are obtained from the semifinished products by removing the binder through sublimation and then subjecting the semifinished products to reaction sintering in nitrogen. The areas of application proposed for the material and the hollow products obtained from it: porous partitions for the filtration and combustion of natural fuels in power plants; porous inserts for the local reinforcement of die-cast products made of light metals.

Results are given for titanium carbide synthesis by reaction of titanium metal with carbon black, graphite, diamond, and butane in the presence of iodine vapor. It is shown that iodine significantly reduces carbide-forming reaction activation energy. It is established that TiC of stoichiometric composition may be prepared at 400°C. Titanium carbide powder with a block size from 19 to 30 nm is synthesized.

Results are given for a study of the effect of treatment temperature on oxidation kinetics of nanodiamond particles. Kinetic models are compared for oxidation by oxygen of nanodiamond powder previously heat treated at different temperatures. It is established that depending on treatment temperature (600 and 1400°C) the kinetic models of oxidation are different. For a specimen treated at 600°C the best model appeared to be two parallel reactions. Oxidation of a specimen heated at 1400°C proceeds according to a model of a single-stage n-th order oxidation reaction. Differences in kinetic models and oxidation reaction kinetic parameters are due to a change in the nature and morphology of specimens, which is connected with nanodiamond transformation into nano-onion-like carbon during heat treatment at a higher temperature.

Staurolite shales alongside kyanite shales are extensively developed in the central part of the Kola Peninsula. In addition, staurolite is waste during electromagnetic separation of kyanite ores, since it is classified as an undesirable impurity (high iron content). Use of this raw material increases the value of the Keiv kyanite deposit as a source of compound ores.

This article describes the pattern of longitudinal wear of the blades of high-speed mixers. It has been established that it is best to strengthen the blades by reinforcing them with hard-alloy plates of variable thickness.

The design features and operating parameters of a cupola-based equipment complex developed by the Italian company “Gamma Meccanica” are analyzed in connection with the increasing use of this equipment in the production of heat-insulating mineral-wool products. The limitations of the injection system are discussed and it shown that the main physico-chemical, gasdynamic, and thermal processes which take place are quite nonuniform, which restricts the maximum productivity of the complex to 6 tons/h and limits its overall thermal efficiency to 11.78%.

The effect of nonisothermal heating temperature in the range 1100 – 1500°C on shrinkage indices and and degree of cristobalitization is studied for quartz steel-pouring refractory specimens with a ceramic concrete structure. Cristobalite formed at elevated temperature has a reduced (150 – 220°C) transition temperature into the low-temperature form. Quartz steel-pouring refractories with a ceramic concrete structure have good thermal shock resistance, and in contrast to corundum-graphite refractories, requiring preliminary high-temperature heating, may operate without the latter (“cold start”).