E. Kh. Shakhpazov

Thermodynamic Properties of Intermediate Ni–P Phases (26–32.5 at. % P) between 971 and 1440 K

The vapor composition over and thermodynamic properties of crystalline nickel–phosphorus alloys (26–32.5 at. % P) are studied by Knudsen cell mass spectrometry between 971 and 1440 K. Mass spectra of the saturated vapor in the Ni–P system indicate the presence of the Ni+, P+2, and P+ ions. The P concentration in the vapor phase does not exceed 1% of the Р2 concentration. The experimental data are used to evaluate the complete set of thermodynamic functions of nickel phosphides. Based on the data for the low-temperature (α, γ) and high-temperature (β, δ) forms of Ni5P2 and Ni12P5 , the thermodynamic characteristics of the corresponding polymorphic transformations are evaluated. The results obtained for a large number of compositions under different experimental conditions (different effusion-cell and coating materials and effusion-orifice diameters) coincide to within the experimental error and are in good agreement with earlier reported phase-equilibrium data and enthalpies of formation, attesting to the high accuracy and reliability of the calculated thermodynamic functions.

Modern trends in the development of ladle metallurgy and the problem of nonmetallic inclusions in steel

The main trends in the development of the ladle treatment of steel have been analyzed. The most complex problem is shown to be the formation of nonmetallic inclusions having a certain type and a low concentration. The main parameters of the ladle treatment of steel that control the type and amount of nonmentallic inclusions in ready products are analyzed using the data of industrial heats, laboratory experiments, and physicochemical simulation and computation. The principles of control of steel purity in nonmetallic inclusions are formulated, and the main trends in the development of the concepts of nonmetallic inclusions are determined.

An Investigation of Evaporation of Liquid Alloys of Iron with Copper

The Knudsen method of mass-spectrometry and the integral option of the Knudsen effusion method realized under conditions of ultrahigh oilless vacuum are used in the overall temperature range from 1440 to 1916 K to investigate the evaporation of pure iron and copper and of a dilute liquid Fe–Cu solution with the copper content ranging from 0.17 to 10.1 at. %. The obtained data are used to calculate the values of standard sublimation enthalpy for Fe and Cu, as well as the partial and integral thermodynamic characteristics of liquid alloys of iron with copper. Significant positive deviations from Raoults law are observed.

Physicochemical Prediction of the Types of Nonmetallic Inclusions: Complex Deoxidation of Steel with Aluminum and Calcium

The complex deoxidation of steel with aluminum and calcium is used as an example to analyze the state of the art in the methods of physicochemical prediction of the types of nonmetallic inclusions forming during ladle treatment of steel. The uncertainty existing in the thermodynamic description of the simplest object of metallurgical technologies, i.e., iron-based dilute liquid solutions, is shown to lead to radically different versions of the oxide-precipitation diagram of the Fe-Ca-Al-O system. The physical causes of this discrepancy are revealed. It is demonstrated that the concentration and temperature dependences of the thermodynamic properties of iron melts can be well approximated using an approach based on the concept of associated solutions. This approach has been used to adequately interpret the reactivity of calcium in iron-based solutions for the first time. The modern methods of physicochemical prediction of the types of nonmetallic inclusions in steel are noted to require detailed theoretical and experimental grounds.

The conditions of formation and stability of quasi-crystalline phases in aluminum-manganese alloys

The conditions of formation, stability, and thermodynamic properties of the icosahedral and decagonal quasi-crystalline phases in the Al-Mn system were studied experimentally. The thermodynamic properties of equilibrium crystalline Al-Mn compositions over the composition and temperature ranges 0–26 at % Mn and 628–1193 K, respectively, and of melts over wide temperature and composition ranges (1043–1670 K and 0–50.1 at % Mn) were determined. Measurements were made by the integral variant of the effusion method under the conditions of an ultrahigh oilless vacuum and Knudsen mass spectrometry. An original technique based on the initiation and study of equilibria in reactions of the alloys with special admixtures of sodium or magnesium fluorides with the formation of volatile products was used to extend the interval of measurements to low temperatures. Complete, reliable, and consistent data on the thermodynamic properties of icosahedral and decagonal quasi-crystalline and crystalline phases based on aluminum and Al-Mn melts were obtained for the first time. Al-Mn melts were shown to contain associates of three types, AlMn, Al2Mn, and Al5Mn. The contributions of covalent interactions to the Gibbs energy and enthalpy of mixing was found to be by far predominant. The thermodynamic properties of alloys of the same chemical composition in the quasi-crystalline and equilibrium crystalline states were compared. The decagonal phase was found to be more stable than icosahedral quasi-crystals. The difference of the Gibbs energies of quasi-crystals of the two types and crystalline compositions increased as the temperature lowered. Arguments in favor of the entropy nature of the stabilization of quasi-crystals were obtained. These phases, like metallic glasses, are only an intermediate state between liquids and crystals and cannot be ground stable alloy states. The conditions of obtaining quasi-crystalline phases from melts were found to be controlled by the appearance of a substantial fraction of icosahedral short-range order in liquids in the region of compositions where associates of a certain kind (Al5Mn) were formed in substantial amounts, x(Al5Mn) ≥ 0.11.

Thermodynamic Properties of Magnesium Silicates

Being a constituent of numerous minerals, magnesium silicates are of extraordinary interest for the Earth and planetary sciences, as well as for cosmology. At the same time, they have many industrial and technological applications, including those associated with the building industry. Reliable data on the thermodynamic properties of magnesium silicates at high temperatures are necessary for the forecasting of various natural phenomena, optimization of technological parameters in a wide range of technological processes and production techniques, and for the development of novel ceramic and ceramic-metal materials, glasses, fluxes, slags and slag-forming mixtures. However, these data are at present almost entirely absent. Results from the direct measurement of thermodynamic characteristics for a magnesium-silicate melt have been reported by a single group only [1, 2]. However, these results do not agree with the data related to the phase diagram [3]. The description of the thermodynamic characteristics of intermediate phases is mainly based on low-temperature measurements and the extrapolation of temperature dependence for specific heats [4]. The present study is aimed at determining the thermodynamic properties of all phases existing in the MgO‐SiO 2 system within the wide temperature range 1571‐1873 K for the entire set of chemical compositions. The measurements were performed by the Knudsen mass-spectrometry method using the approach of [5], which was based on the generation of volatile reaction products formed as a result of the reduction of oxide components. When the MgO‐SiO 2 mixture interacts with the reducing agent R, which is, in this case, either the material of the effusion cell itself (R = Ta, Nb, Mo) or the purposefully added powders of these metals, the following chemical reactions occur: n MgO(solid, liquid) + R(solid)

Key Trends in the Development of a Metallurgical Technology to Meet the Growing Steel Quality Requirements

The recent increase in the requirements for the service properties of steels of certain grades is discussed. The main trends in this field are noted, and examples are given for improving technological processes according to these requirements that ensure a stable chemical composition of steel, a decrease in the content of harmful impurities, and a decrease in the number of “dangerous” nonmetallic inclusions in steel. It is important to create and effectively use through technological schemes and models for the production of steel products that can correct the process of the next processing stage depending on the results of the previous stage.

On continuous casting of steels using pulse-periodic cooling in a mold

The causes of the difficulties that appear during continuous casting of steels with a wide solidification range are analyzed. It is shown that these difficulties can be overcome using a mold design that provides a pulse-periodic change in the intensity of heat removal from the mold tube walls.

Effect of the Composition and Quality Characteristics of the Metallic Charge on the Operational Indices of Converter Steelmaking

This article examines features of a new process for forming the metallic cold charge in the working volume of a 360-ton oxygen converter. The new process, using new composite materials of the Sintikom® type, is contrasted with the standard process employing charge materials of the traditional composition. The article examines the effect of the composition of different combinations of charge materials and the methods used to charge them on the operational indices of converter steelmaking.

Effect of Composites of the Sintikom® Class on Iron Losses in Converter Steelmaking

It is shown that a technology which uses the composite Sintikom® is helping the Hutta-Katovitse plant (in Poland) to increase the output of liquid steel from a charge which contains considerably less iron than a standard cold charge. Any metallurgical plant that organizes the on-site production of Sintikom® will be able to recover iron from the plants own waste products.