N. G. Shaposhnikov

Surface tension of CaO-Al2O3, CaO-SiO2, and CaO-Al2O3-SiO2 melts

A method for the approximation of the temperature-concentration dependence of the surface tension of CaO-Al2O3, CaO-SiO2, and CaO-Al2O3-SiO2 melts was suggested. The method was based on the statistical-thermodynamic model of associated solutions. A comparison of the calculated surface tensions of the melts with the available literature data showed that the suggested approach allowed the surface tension of liquid slags to be correctly predicted as a function of temperature and composition.

Effect of Composition, Structural State, and Manufacturing Technology on Service Properties of High-Strength Low-Carbon Steel Main Bimetal Layer

The effect of composition, structural state, excess phase precipitation, and manufacturing technology parameters on service property indices of high-strength, low-carbon steel of a main bimetal layer is studied in detail. For the low-carbon, high-strength steels developed primary importance is attached to strengthening mechanisms, connected with formation of different size carbonitride precipitates with different fineness, and secondary importance applies to the presence of strong structural components. A simultaneous improvement in strength properties and preparation of good steel weldability may be achieved by some increase in carbon content using a balanced microalloying system with a reduction in concentration of manganese, chromium, nickel, and copper, and effective alloying with boron. It is shown that the possibility of achieving high strength properties for the low-carbon steel developed with relatively slow cooling rates creates favorable conditions for obtaining a clad rolled product with a good and stable set of mechanical and other service properties, and quality indices.

Experimental Study and Modeling of the Thermodynamic Properties of Magnesium Silicates

The thermodynamic properties of all MgO-SiO2 system phases were studied by Knudsen mass spectrometry over a wide temperature range (1571–1873 K) and the whole range of compositions. An approach based on the generation of volatile interaction products formed in the reduction of oxide components was used. The reducing agents were Nb, Ta, and Mo. The observed ion current intensity ratios I(Mg+)/I(SiO+) were used to calculate the activities and partial thermodynamic functions of the components in liquid and crystalline MgO-SiO2 mixtures and the integral thermodynamic functions of formation of magnesium ortho-and metasilicates. For the first time, direct and reliable information about the thermodynamic properties of all system phases at high temperatures was obtained. These results in combination with all the available data on the thermodynamic properties and phase equilibria in the MgO-SiO2 system were used to develop a statistical-thermodynamic model of liquid magnesium silicates based on treating them as associated liquids. Simultaneously, the problem of obtaining self-consistent data on the thermodynamic functions of all phases and conditions of equilibria between them was solved. In addition to polymeric silicon-oxygen structures of arbitrary sizes and spatial configurations, heteromolecular complexes such as MS, M2S, and M3S (S=SiO2 and M=MgO) were found to exist in liquid MgO-SiO2 mixtures. The correctness of the results obtained was substantiated by the virtually complete coincidence of the calculated thermodynamic properties and phase equilibrium conditions with experimental data and their conformity to the general patterns characteristic of binary silicate systems.

Analysis of thermodynamic properties and phase equilibria in the Si-P system

A self-consistent analysis of the available data on thermodynamic properties and phase equilibria in the Si-P system is performed. Thermodynamic properties of solid and liquid solutions of phosphorus in silicon are approximated on the basis of the concepts of dilute and ideal associated solutions. The thermodynamic properties and phase boundaries in the range of compositions 0 ≤ x(P) ≤ 0.5 are adequately described.

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.

Thermodynamic Properties and Amorphization of Zr–Si Melts

The relationship between the thermodynamic properties of Zr–Si liquid alloys and their propensity to amorphization is studied. The temperature–concentration dependences of the thermodynamic properties of melts are presented using the concept of associated solutions. It is shown that the range of amorphization coincides with the range of the predominant concentration of Zr3Si associative groups with low formation entropy.

Features of Titanium Carbide Precipitation in Low-Carbon High-Strength Steels Microalloyed with Titanium and Molybdenum

Theoretical and experimental study is carried out to establish features of all types of excessive phase precipitation in low-carbon steels microalloyed with titanium and molybdenum. It is established that the main type of precipitates controlling grain boundary and precipitation hardening mechanisms is FCCcarbide based on TiC. The optimum thermal deformation treatment regime is established providing simultaneously effective grain refi nement of steel structure and the formation of a system of nanosize carbide precipitates that control strengthening by a precipitation hardening mechanism. On the basis of the results obtained, chemical composition and heat-treatment regime are proposed for producing low-carbon TiM–Mo microalloyed steels with a ferritic microstructure and set of mechanical (tensile strength more than 850 MPa) and other service properties.

Features of Nonmetallic Inclusion (Precipitates) Evolution During Heating of Structural Steel for Rolling

Evolution of nonmetallic inclusions on heating a billet for rolling is studied using contemporary methods of electron microscopy and local x-ray spectral analysis for steels 20-KSKh and 13KhFA from an industrial melt. It is established that it is controlled by the occurrence of three main processes. The first consists in the deposition of manganese sulfide on the surface of aluminum-magnesium spinel and other oxide composites MgO–Al2O3–CaO both from solid solution and from soluble MnS precipitates, as a result of which inclusions become corrosion-active and their amount increases. An increase in metal heating duration leads to the coalescence of sulfide components from smaller to larger sizes. As a result of this, the number of inclusions exhibiting corrosion activity decreases. The majority of titanium nitride inclusions are retained with the metal composition outside a dependence on billet heating temperature and duration, and there may be formation of complex TiN inclusions with niobium nitride, with calcium and manganese sulfides, and also of even more complex composition, including aluminum-magnesium spinel, and these inclusions may have an unfavorable effect on the steel’s properties. In contrast, a favorable process is deposition during subsequent cooling on the surface of sulfide and other forms of inclusions of cementite and other carbides, which may lead to a marked increase in strength properties without a reduction in steel ductility. On the basis of results obtained, a number of effective production methods are suggested for improving steel resistance to local corrosion and other service properties.

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.

Conditions for Complex Precipitate Formation and Their Effect on Low-Carbon Steel Cold-Rolled Product Properties

The effect of chemical composition and recrystallization annealing regimes in continuously operating units on the mechanical properties of cold-rolled product of type 08Yu steels is studied. It is established that with a sulfur content of 0.012–0.018% during hot rolling an optimum amount and size distribution of manganese sulfide particles is achieved providing the formation on them of cementite and aluminum nitride precipitates. Complex MnS-cementite particles formed in an equalization chamber of a continuously operating hot galvanizing unit facilitate an increase in formability as a result of a reduction in the degree of the difference in grain size of the microstructure and an increase in cementite distribution uniformity. Precipitation of AlN on MnS particles in the course of metal hot rolling and cooling provides more complete removal of nitrogen from solid solution, and consequently a reduction in steel tendency towards strain ageing. A significant reduction in the proportion of fine AlN particles increases the rate of cold worked metal recrystallization, and this leads to a reduction in fineness of the microstructure and a corresponding reduction in yield strength and an increase in relative elongation.