Том 47, № 1 (2017)

New approaches are required in the industrial processing of tailings slag from steelmaking. It has been shown in recent years that slag may be processed to obtain not only construction materials but also metal suitable for industrial use. In the present work, we study the expediency of reducing steelmaking slags as to obtain metallic and oxide phases for use in steelmaking and the construction industry. In particular, we consider slag from the tailings at Zlatoust Metallurgical Plant. FactSage software (version 6.4) is used for thermodynamic modeling of high-temperature slag reduction. Three slag compositions are considered, with 5, 10, and 15 wt % FeO. Modeling is undertaken for temperatures at intervals of 5°C in the range 750–1650°C, at a gas pressure of 0.1 MPa. We assume that a known excess of carbon (graphite) is introduced in the system. For convenience of analysis, the basic calculation results are presented as temperature dependences of the masses of the components and the composition of the phases considered. Modeling shows that, beyond 1340°C, practically all the iron is reduced and passes to the melt. Nickel and copper behave analogously. However, the results indicate that complete extraction of manganese in the metallic melt on reduction by carbon should not be expected. Even with maximum manganese extraction in the metallic melt, its presence in the slag and gas phases remains pronounced. The volume of gas phases formed in reduction at different temperatures is estimated. Modeling convincingly shows that, over the whole temperature range considered, carbon monoxide predominates in the gas phase. Information regarding the enthalpy of the system as a function of the temperature permits estimation of the thermal energy that must be expended to bring the system to a state at which the required reduction processes are possible.

The manufacture of diamond drill bits (diameter up to 212 mm) at pressures up to 1.5 GPa and temperatures up to 1250°C is described. This technology includes sintering by electric heating within a thermally and electrically insulating shell in a steel high-pressure chamber, for 120 min. Such high-pressure sintering is found to be a relatively rapid process, and the equipment may be employed repeatedly. Steel highpressure chambers of cylinder–piston type with working diameters up to 280 mm are developed and produced. In bit manufacture by this means, matrix material with diamonds may be pressed onto steel housing; alternatively, it is possible to use a powder housing with diamonds or with holes for subsequent attachment of diamonds by soldering or mechanical methods. Bits with model cutting elements made of polycrystalline carbonado diamonds are manufactured, and their operational properties are verified. In drilling a marble block under loads up to 50 kN, at speeds of 355 rpm, mechanical speeds up to 20 m/h are attained. In the technology developed, the cutting properties of carbonado diamonds may be retained, but the thermal stability matches that of PCD diamond–hard-alloy composites. The bits are rugged enough for use in the most challenging drilling conditions. The metal–ceramic matrix permits the reliable attachment of cutting elements made of ASPK diamond composites. It is strong and wear-resistant. This is an energy-saving technology with little environmental impact and is fast. It may be used to produce wear- and corrosion-resistant metal–ceramic housings, with subsequent attachment of diamonds by soldering or mechanical methods, on the basis of PCD composites with varying thermal stability.

The density and surface tension of melts of ferronickel (0–100% Ni) and oxidized nickel ore are measured by the sessile-drop method, as well as the interface tension at their boundary in the temperature range 1550–1750°C. The composition of the nickel ore is as follows: 14.8 wt % Fetot, 7.1 wt % FeO, 13.2 wt % Fe₂O₃, 1.4 wt % CaO, 16.2 wt % MgO, 54.5 wt % SiO₂, 4.8 wt % Al₂O₃, 1.5 wt % NiO, and 1.2 wt % Cr₂O₃. In the given temperature range, the density of the alloys varies from 7700 to 6900 kg/m³; the surface tension from 1770 to 1570 mJ/m²; the interface tension from 1650 to 1450 mJ/m², the density of the oxide melt from 2250 to 1750 kg/m³; and its surface tension from 310 to 290 mJ/m². The results are in good agreement with literature data. Functional relationships of the density, surface tension, and interphase tension with the melt temperature and composition are derived. The dependence of the alloy density on the temperature and nickel content corresponds to a first-order equation. The temperature dependence of the surface tension and interphase tension is similar, whereas the dependence on the nickel content corresponds to a second-order equation. The density and surface tension of the oxide melt depend linearly on the temperature. The results may be used to describe the formation of metallic phase when carbon monoxide is bubbled into oxide melt.

The continuing significance of the metallurgical sector in the Russian economy is noted. The structural changes in the consumer market for metal goods are refined, in the light of the continuing demand from the power industry. It is important to take account of the geographic integration of markets in contemplating further industrialization. On the basis of a model proposed by Glushchenko for assessing the integration of the internal consumer market, the interregional integration of markets is analyzed for the example of several submarkets for metal products used in the oil and gas industry and in construction. Market integration is assessed in terms of compliance with the uniform-price law, which proposes a single price for a particular product over several geographically distinct market segments, with no barrier to trade between them. An autoregression model is used to assess the rate of price convergence between regions and also the convergence to the national average. This approach permits comparison of the regional markets for high-tech, high-quality, and regular metal products in terms of geographic integration. The results show relatively weak integration of the regions in all three submarkets. For each one, the structure of integrated relations is different. On the basis of the results, a map of geographic integration of the market for high-tech metal products used in the oil and gas industry is plotted, reflecting the price convergence in the regions in a time-series model. The geographic distance between the market segments has no great influence on the rate of price convergence. It is expedient to consider the geographic integration of the markets in order to assess the indeterminacy when developing a strategy for new industrialization in Russia. In expanding the domestic consumer market for high-tech metal products with high added value, the development of interregional communication tends to reduce competitive risks and creates positive multiplicative and synergetic effects.

Further evidence is found to confirm that blast-furnace performance is not always improved when the gas pressure in the furnace is increased as a result of artificial drag in the gas-supply network. What is important is not simple increase in the gas pressure but optimization of this pressure and also the total pressure difference in the furnace in specific operating conditions.

The influence of dendritic crystallization on the structure and properties of continuous-cast pipe blanks (diameter 150 mm) made from steel with 0.2% C is studied, in the cast and heat-treated states. Dendritic crystallization results in different chemical composition of the austenite and the boundary between the crystals, with different properties. That affects the structure of the steel. Besides the familiar factors, the improvement in the mechanical properties of cast subeutectoid steel after heat treatment is associated with the formation of impurity-rich ferrite in segregated sections of the dendritic structure.

In a test melts, high-carbon ferrochrome is produced from chrome sinter and chrome-ore fines in an arc electrofurnace. Two types of sinter with the best performance—the best sintering rate, strength, and product yield—are studied. It is demonstrated by experimental melts that high-carbon ferrochrome can be produced from proposed agglomerates. An estimation of smelting parameters for production of high-carbon ferrochrome is made.

The diffusional chrome plating of nonalloy steel by the gas transport of iodides is investigated. The formation of chromium-bearing coatings on steels with different carbon content is studied. Iodide transport may effectively be used in diffusional chrome plating.