L. I. Leont’ev

Thermodynamics of oxygen solutions in the complex reduction of Fe-Co melts

Thermodynamic analysis of the complex reduction of metal melts is considered. The proposed analytical method identifies the influence of the weaker reducing agent in amplifying the effect of the stronger reagent. The curves of oxygen solubility pass through a minimum. Analysis of the extremal curves of oxygen concentration in the melt as a function of the content of reducing agents yields a formula for the content of the stronger reducing agent such that the oxygen concentration is minimal. Thermodynamic analysis of the combined influence of aluminum and silicon on the oxygen solubility in Fe-Co melts indicates that the reaction products may contain both mullite (3Al2O3 · 2SiO2) and kyanite (Al2O3 · SiO2). The presence of silicon in the melt intensifies the reducing action of aluminum: slightly when mullite is formed and significantly when kyanite is formed. When kyanite is formed, the curves of oxygen solubility pass through a minimum, whose position depends on the aluminum content in the melt but not on the silicon content. The aluminum content at the minimum declines slightly from iron to cobalt, as for Fe-Co-Al systems. Further addition of aluminum elevates the oxygen concentration. The formation of the compounds Al2O3, 3Al2O3 · 2SiO2, Al2O3 · SiO2, and SiO2 is investigated as a function of the Al and Si content in the melt.

Effect of boron and yttrium on the phase composition and the microstructure of natural Nb-Si composites

The phase formation in Nb-Si composites of a eutectic composition alloyed with 0.2–2.0 at % B and 0.9–6.0 at % Y is considered on model specimens prepared by vacuum arc melting. The phase composition of three-component alloys and the phase transformation temperatures are determined by physicochemical analysis, the specimen density and microhardness have been measured, and the content of alloying elements in the alloys has been determined. It is found that the solidus and liquidus temperatures of the alloyed alloys are almost unchanged within the yttrium and boron concentrations under study, and the difference between the densities of the model specimens and the base Nb-18.7 at % Si is ±1.6%. The introduction of yttrium and boron into the natural Nb-18.7 at % Si composite increases the microstructure dispersion and influences the composition of the strengthening phase: yttrium stabilizes high-temperature silicide Nb3Si at low temperatures, and boron, conversely, catalyzes its decomposition with formation of α-Nb5Si3.

Calculation of the value of manganese ore raw materials

The variety of the types of manganese ore raw materials used in ferroalloy production causes the development and improvement of approaches to their metallurgical evaluation. The calculation methods are based on the chemical composition of the raw materials. The most widely used method of determining the quality of manganese ores and concentrates from their chemical compositions [1] also takes into account the manganese, iron, and phosphorus contents and the amount and composition of gangue. As a result, it can estimate the possible degree of manganese reduction from statistical formulas derived for the manufacture of high-carbon ferromanganese and silicomanganese. For metallurgical evaluation, we chose promising manganese ore materials located in various deposits in Russia, Ukraine, and the Republic of South Africa (Table 1). The metallurgical evaluation performed according to the statistical procedure in [1] demonstrates that these materials can be used for the manufacture of both high-carbon ferromanganese and silicomanganese. The main quality indices ( KS is the phosphorus content availability of the ore, RO is the amount and composition of gangue, MF is the specific iron content in the ore) for the manufacture of carbon-containing ferromanganese are given in Table 1. The higher coefficient KS , the higher the availability of the raw materials in terms of a phosphorus content and the higher the amount of phosphorus manganese ore raw materials to be added to these materials. The sign minus before the index indicates that an alloy cannot be made with a given phosphorus content without adding high-quality raw materials with a low phosphorus content.

Status and Prospects of Ferroalloys Production in the Russian Federation

Data are presented on the production and consumption of ferroalloys in the Russian Federation from 1994 to 2014. The quantities of the main ferroalloys that were made during this period are compared to the volume of steel production, and a comparison is also made between the structure of ferroalloys production in Russia and abroad. Data on the import, export, and apparent consumption of ferroalloys ate also reported. It is noted that Russia needs to expand its raw-materials base in order to make the main ferroalloys: manganese-, chromium-, and silicon-based ferroalloys. Such expansion is necessary to ensure that Russian companies can compete in the international market and that Russia is not threatened economically. These goals can be accomplished only with the support of the government.

Hydrogen reduction kinetics of electrometallurgical slime

The interaction of hydrogen with the zinc-containing electrometallurgical slime of the Severstal’ metallurgical works has been studied. The sequence of transformations in the slime heated to 1100°C in hydrogen or air has been established. The experimental and calculated weight losses coincide. Some of the carbonates are shown to decompose in the temperature range 300–700°C, and most iron and zinc oxides are reduced to a metal. In the temperature range 650–850°C, zinc is almost completely sublimated. At temperatures above 800°C, complex oxides are reduced and calcium and magnesium carbonates and sulfates are likely to decompose. Experimental digital data on the zinc sublimation rate are processed by the least squares method with approximating equations used in thermal analysis. The kinetics of nonisothermal zinc sublimation is comprehensively analyzed using a unique procedure developed for taking into account the background of a peak and the effect of accompanying processes. An equation for the calculation of the zinc sublimation rate under experimental conditions (fluidized bed) is given and tested.

Thermodynamics of oxygen solutions in Fe-Ni, Fe-Co, and Co-Ni melts

By thermodynamic analysis of oxygen solutions in Fe-Ni-O, Fe-Co-O, and Co-Ni-O melts, the composition of the oxide phase is established for the first time. In addition, the equilibrium oxygen concentrations in these melts are determined over the whole range of alloy compositions. In Fe-Ni-O and Fe-Co-O melts, the oxide phase mainly contains FeO over a relatively broad of alloy compositions. Sharp increase in NiO content is only observed when the molar fraction of nickel exceeds one; sharp increase in CoO content is only observed when the molar fraction of cobalt exceeds 0.8. In the Co-Ni-O system, the oxide phase contains both CoO and NiO over the whole range of alloy compositions. In the Fe-Ni system, adding nickel to the melt reduces the solubility of oxygen as a result of weakening of the oxygen bonds in the melt by nickel and consequent increase in oxygen’s activity. With further increase in nickel content in the melt, the oxygen content rises at first slowly and then very sharply. In the Fe-Co system, analogously, adding cobalt to the melt reduces the solubility of oxygen as a result of weakening of the oxygen bonds in the melt and consequent increase in oxygen’s activity. With further increase in cobalt content, the oxygen content rises at first slowly and then relatively rapidly. In the Co-Ni system, adding nickel to cobalt increases the solubility of oxygen over the whole range of alloy compositions, on account of the significantly greater solubility of oxygen in nickel than in cobalt.

Solubility of oxygen in niobium-bearing iron-nickel melts

The solubility of oxygen in niobium-bearing iron-nickel melts is studied experimentally, for the example of Fe-40% Ni alloy at 1823 K. Niobium reduces the solubility of oxygen in this melt. Values are determined for the equilibrium constant of the reaction between niobium and oxygen dissolved in the given melt (logK(1)(Fe-40% Ni) = −4.619), the Gibbs energy (ΔG(1)(Fe-40%Ni)o = 161210 J/mol), and the interaction parameters (eNb(Fe-40% Ni)O = −0.630; eO(Fe-40% Ni)Nb = −0.105; eNb(Fe-40% Ni)Nb = 0.010). Over a wide range of concentrations, the Gibbs energy of the reaction between niobium and oxygen dissolved in Fe-Ni melts, the equilibrium constants, and the interaction parameters at 1823 K are determined. The solubility of oxygen in Fe-Ni melts of different composition containing niobium is determined at 1823 K. With increase in nickel content in the Fe-Ni melts, the oxygen affinity of niobium increases significantly, on account of the decrease in oxygen binding forces with increase in nickel content in the melt (γO(Fe)∘ = 0.0084, γO(Ni)∘ = 0.297).

Physicochemical properties of the zinc-containing dusts of electric furnace steelmaking

The properties of the dusts of electric-arc melting in the Severstal’ metallurgical works are studied by X-ray diffraction, Mössbauer spectroscopy, and electron microscopy. The elemental compositions of dust particles of various sizes are determined, and the complex structural composition of iron-containing oxide phases is revealed. It is shown that, in these systems, the carbon reduction of zinc from zincite is possible in the solid state in the temperature range 600–1000°C. In this case, zinc passes into a gaseous phase and iron oxides are reduced to form metallic iron.

Study of the phase composition of metallurgical slimes by Mössbauer spectroscopy

The phase composition of blast-furnace and electric-furnace slimes is studied by Mössbauer spectroscopy and X-ray diffraction. The iron distribution over iron-containing phases in the slimes is studied. As a result of analyzing the Mössbauer and X-ray diffraction spectra of the slimes, it is found that a number of elements present in the slimes form solid solutions with iron oxide phases. A combination of Mössbauer spectroscopy and X-ray diffraction is shown to give the most full and precise data on the character of the iron-containing phases existing in metallurgical slimes.

Formation of metallic phase on reducing-gas injection in multicomponent oxide melt. Part 2. Density and surface properties

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.