V. Ya. Dashevskii

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.

Deep decarburization of steel

The process of deep decarburization of steel during argon or hydrogen-argon mixture injection has been studied. Experimental heats show that the gas-mixture injection into a melt is a very effective way to increase the degree and rate of decarburization. Hydrogen diffusion into argon bubbles decreases the partial pressure of CO in bubbles, which also increases the degree of decarburization.

Thermodynamics of Oxygen Solutions in Fe-Ni-V Melts

The oxygen solutions in Fe-Ni melts with up to 5% V are analyzed thermodynamically. The results of the works in which the fields of the vanadium-deoxidized oxide phases in iron and nickel were determined are generalized. The thermodynamic model developed for the calculation of the deoxidation of iron-nickel alloys with vanadium is shown to be adequate. The deoxidizing capacity of vanadium decreases insignificantly as the nickel content in the melt increases to 20% and increases substantially as the nickel content increases further. The oxygen solubility curves pass through a minimum, whose position changes from 2.3192% V for pure iron to 0.7669% V for pure nickel. We determined the equilibrium point [V]* between the (Fe, Ni)V2O4 and V2O3 oxide phases for alloys of six compositions at 1873 K. In nickel, [V]* is almost 200 times lower than in iron. The deoxidation of the Fe-40% Ni melt with vanadium is studied experimentally, and the experimental results agree satisfactorily with the calculated data.

Thermodynamics of the oxygen solutions in manganese-containing Fe-Co melts

Thermodynamic analysis of the oxygen solutions in manganese-containing Fe-Co melts has been performed. The equilibrium constants of deoxidation reaction of iron-cobalt melts with manganese, the activity coefficients during infinity dilution, and the interaction parameters in various melts are found. During the deoxidation of manganese-containing Fe-Co melts, the oxide phase contains FeO and CoO along with MnO. The compositions of the oxide phase above Fe-Co-Mn-O melts are calculated. When the cobalt and manganese contents in the melts increase, the mole fraction of manganese oxide increases, and it approaches 1 in the case of pure cobalt. The dependences of the oxygen solubility in the melts on the cobalt and manganese contents are calculated. The deoxidizing capacity of manganese increases substantially with increasing cobalt content in the melt. The curves of oxygen solubility in Fe-Co melts have minima, whose values shift toward low manganese content in a melt. The manganese contents are determined at the minimum points in the oxygen solubility curves, and the corresponding minimum oxygen contents are found.

Solubility of oxygen in carbon-bearing Fe-Ni melts

Oxygen solutions in carbon-bearing Fe-Ni melts are analyzed thermodynamically. The equilibrium oxygen concentrations in Fe-Ni alloys in the presence of carbon have been determined for the first time over a wide composition range and a wide range of the partial pressures of carbon mono-and dioxides. As the carbon concentration increases, the oxygen concentration decreases in melts of all compositions. As the nickel content in the melt increases, the equilibrium oxygen concentration decreases at the same carbon concentration. The difference in the oxygen concentrations in iron and nickel at the same carbon concentration is almost two orders of magnitude, which can be explained by the substantial weakening of the bonding forces of oxygen in the melt and the less pronounced weakening of the bonding forces of carbon atoms with increasing nickel content. The oxygen solubility curves pass through a minimum, whose position changes with the nickel content from 2.443% C for pure iron to 2.842% C for pure nickel. The solubility of oxygen in a Fe-40% Ni melt is experimentally studied at various carbon contents. The experimental results agree well with the calculated data.

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.

Thermodynamics of the oxygen solutions in aluminum-containing Fe-Co melts

Thermodynamic analysis of aluminum-containing Fe-Co melts is performed. The equilibrium constants of the deoxidation of iron-cobalt melts with aluminum, the activity coefficients during infinite dilution, and the interaction parameters in melts with various compositions are determined. The oxygen solubility in the melts under study is studied as a function of the cobalt and aluminum contents. Aluminum is characterized by a very high affinity to oxygen in iron-cobalt melts. The deoxidizing capacity of aluminum substantially increases with the cobalt content in the melt. The curves of the oxygen solubility in aluminum-containing iron-cobalt melts have a minimum, whose position shifts to lower aluminum contents as the cobalt content in the melt increases. Further aluminum additions increase the oxygen concentration in the melt: the higher the cobalt content in the melt, the sharper the increase in the oxygen concentration after the minimum when aluminum is added to the melt. The aluminum contents at the minimum points in the oxygen solubility curves are determined, and the corresponding minimum oxygen concentrations are found.

Oxygen solubility in silicon-containing Fe-Co melts

Thermodynamic analysis of the oxygen solutions in silicon-containing Fe-Co melts is performed. The equilibrium constant of silicon deoxidation of iron-cobalt melts, the activity coefficients for infinite dilution, and the interaction parameters for melts differing in composition are determined. The dependences of the oxygen solubility in the melts under study are calculated for different cobalt and silicon contents. The deoxidizing capacity of silicon increases substantially as the cobalt content in a melt increases. The curves of oxygen solubility in Fe-Co melts have a minimum; the minimum oxygen solubility shifts to a low silicon content as the cobalt content in the melts increases. The silicon contents for the minima in the curves of oxygen solubility and the minimum oxygen concentrations corresponding to the silicon contents are determined.

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).