Том 59, № 2 (2018)

This article provides an analysis of the effect of adding hot-briquetted iron (HBI) on the main smelting production indices, DSP-150 lining working layer life, and refractory material consumption for servicing under PAO Tagmet electric steel smelting workshop conditions. Various schemes are considered for HBI charge fractions to a furnace and the optimum version is determined. Changes in slag composition are analyzed with use of HBI. Recommendations are proposed for furnace lining servicing under conditions of using HBI on the example of DSP-150 operated on a solid charge in order to improve its life. The economic saving effect of introducing the recommendations is demonstrated.

Results are provided for a study of refractory objects based on fuzed periclase after service in the suction pipe of an RH-degasser in two metallurgical enterprises. In one enterprise the pipe operates in contact with slag, containing fluorspar with an alumina slag-forming component as a homogenizing addition, and in the second with slag for whose homogenization only fluorspar is used. In both cases, but in different pipe service conditions, there are 100 melts, and the operating duration is 1550 – 1800 min. It is established that the depth of molten slag component filtration into refractory depends on the form slag homogenizing additive in the steel-pouring ladle. Slag containing a combination of feldspar with alumina slag-forming additive penetrates into the refractory microstructure to a greater depth, which leads to a change in the initial phase composition of an object with formation of a considerable amount of secondary phases.

Corundum composition heat insulating materials are used successfully for high-temperature insulation and are mainly produced by casting that has a number of disadvantages. The authors of the present article propose a vibration-compaction method for producing such materials that makes it possible to intensify the production process. Results are provided for a study of the compositions for preparing corundum heat-insulation materials based on hydraulic binders. The main features are established for the effect of charge component content on specimen physicomechanical properties. Optimum compositions are revealed satisfying the specifications of GOST 5040–2015.

The influence of both organic and inorganic additives to calcium aluminate cement on the processes of hydration and structure formation of concrete both at normal and elevated temperatures is investigated here. The results of investigating phase transformations in hardened calcium aluminate samples during heating from 20 to 900°C are given. The structure change mechanism and the reasons for the reduction of the strength of concrete under the influence of high temperatures are described.

We study the destruction of graphitized electrodes in the course of their operation. It is shown that the predicted behavior of an electrode column under thermal shocks guarantees the possibility of application of integrated performance characteristics of graphitized electrodes, including the thermal stability of the electrode material as a technological factor of production and the dependence of the admissible operating current on the quality criterion of the electrode column regarded as a structural element of the electric furnace as an operational factor.

Results are reported on the sintering ability of pure synthetic magnesium oxide (MgO) using variously pretreated eutectic sintering additives. It was established that the sintering ability of synthetic MgO was affected by the type of precursors used to prepare both the MgO and eutectic sintering additives. The best sintering ability was observed for MgO prepared from magnesium bicarbonate. The sintering additive made of natural quartzite and technical aluminum and magnesium hydroxides was most effective.

The results of investigations of mechanoactivation of a mixture of hafnium and carbon black powders in conditions of intensive vibration treatment using grinding bodies made of VK6 hard alloy and ShKh15 steel are presented. It is shown that the vibration treatment of the initial components leads to a mechanochemical synthesis of hafnium carbide starting from the first seconds of activation. Moreover, in the proposed treatment conditions, it is preferable to use steel grinding bodies.

An opportunity of using solar energy to develop a multicomponent ceramic material synthesis technology using melts has been demonstrated. Optical and energy parameters of the 1 MW Large solar furnace for synthesizing aluminum titanate-based materials are presented along with their phase and grain size compositions depending on the melt cooling rate. A possibility of obtaining a two-phase material containing the tialite phase and spinel is shown. A positive effect of the spinel phase on the properties of ceramics made from the material synthesized by using solar energy has been established.

We present the results of experimental investigations in the field of formation of ceramic aluminooxide coatings by the method of microarc oxidation of aluminum. The research works were carried out at the “Prometei” CSRS of Structural Materials of the “Kurchatov Institute” SRC.

Strength, morphology, and phase composition are analyzed for a ceramic composite system based on fibers of tetragonal ZrO₂ and a matrix with different content of SiO₂ and Al₂O₃. It is shown that with an Al₂O₃ content from 0 to 20 wt.% there is formation of a precipitation-hardened structure and an increase in material ultimate strength in bending. The reduction in strength with a further increase in Al₂O₃ content is due to a deficiency in SiO₂ binder and inadequate Al₂O₃ and mullite particle sintering with each other. Features of the structure and phase composition are demonstrated for a composite based on ZrO₂ fibers with a different Al₂O₃:SiO₂ ratio in the matrix.

Results are presented for comparative tests of refractory concretes in a rotary type laboratory furnace by means of which it is possible to model conditions actually existing during heating unit operation. This in turn makes it possible to provide an objective prediction of the efficiency of using different refractories as lining material for one or another heating unit. In addition it is possible to conduct dynamic study of several types of refractory object during one experiment and correspondingly comparative analysis for refractories in a specific corrosive medium.

Previous research in the field of preparing SiC-containing suspensions, and also refractory materials based on them, are analyzed. The effect of SiC additive fineness in composite HCBS of the Al₂O₃–SiO₂–SiC system is studied with a predominantly high-alumina composition on the properties of materials based upon them after firing the range 1000 – 1400°C. The effect of firing temperature on specimen shrinkage and growth, and their porosity and strength in bending are studied. For specimens after firing at 1200, 1300, and 1400°C a weight increase is detected pointing to SiC oxidation with formation of SiO₂. The maximum ultimate strength in bending (110 – 130 MPa) is achieved with a firing temperature of 1200°C, and the ultimate strength in compression for specimens of all compositions after firing at 1200°C is 200 – 425 MPa.