Nitrogen pressure can be a basis for the most general classification of steel, alloyed by nitrogen. Nitrogen steels are made under normal pressure, high nitrogen steels are made under pressure that is higher than atmospheric in special units. Nitrogen, as well as carbon, also strengthens austenite, but increases thermal stability of austenite, has the smaller sizes of ions and high solubility in γ- and α-phases. The result is smaller size of nitrides, smaller superficial energy, their higher strengthening effect and possibility of simultaneous increase in durability and corrosion resistance of austenite. The article considers the mechanisms of nitrogen influence on properties of steel, thermodynamics and kinetics of steels alloying with nitrogen, critical concentration of nitrogen and influence of nitrogen on properties of steel. There is no uniform balanced database and thermodynamic model now. Therefore any choice of values of equilibrium constant and parameters of interaction according to tabular data reduces the accuracy of calculations of nitrogen solubility in steel. In the circumstances it is better to use experimental data for concrete alloy from original works. At the choice of data it is necessary to be guided by the following control values: K_N = 0,044, A ≥ 600. The nitrogen solubility in liquid metal, in α- and γ-phases is significantly various. Critical nitrogen concentration N_k, which excess leads to formation of bubbles and interstices at steel solidification, depends on composition of steel. Now the acceptable results when determining critical nitrogen concentration, can be received from the following condition: during the whole time of solidification the nitrogen content in residual liquid has to be less its equilibrium with the general pressure in the system of content in liquid metal at the same temperature T. Examples of nitrogen and high nitrogen steels, including steels with special properties, such as corrosion-resistant in bioactive environments, bactericidal steel, alloyed according on the scheme C + N steels, are given.

The article is devoted to study of the process of mold inoculation of high manganese steel castings using titanium carbonitride. Introduction considers basic principles, alloying and inoculation of casting alloys. Review of the papers on this topic made by native and foreign researchers was given. Conclusions were made on the materials presented in the studied papers, goals and tasks for studies were formed. Besides, in this part of the article relevance of the conducted researches was substantiated as well as practical significance for casters. The second part of the article describes routine of experiments. Materials involved when conducting experimental works were considered in details: charge materials, treatment agent, materials for foundry molds. Besides, there are also described the way to receive experimental cast products, methodology to determine thermal conditions for forming experimental models in foundry mold and regimen of thermal treatment. Herewith, methodology for conducting metallographical test was considered. The third part of the article mentions the results received during carrying out experimental works on mold inoculation using fine titanium carbonitride powder of high manganese steel castings. Influence of inoculation on the level of performance properties expressed via coefficients of abrasive wear and wear striking resistance was considered as well as change of the indicated peculiarities in relation to not inoculated alloy was evaluated. Besides, results of metallographical tests were given which allowed to substantiate change of the performance properties level of high manganese steel. Influence of thermal conditions of forming cast products was also evaluated, in particular speed of alloy cooling in foundry mold on the level of performance properties of inoculated high manganese steel. In final part of the article conclusions on the results of conducted researches were made as well as manufacturing recommendations were given for practical implementation of the work results to increase the level of performance properties of high manganese steel. Besides, recommendations on the most reasonable expenditure of titanium carbonitride powder ensuring receipt of the necessary characteristics of microstructure and as a consequence, increase of the level of performance properties were given.

Large-sized rings, manufactured by various methods of metal forming, are used in many industries. For the power industry, it is relevant to manufacture of retaining rings made of non-magnetic austenitic steel in order to strengthen the winding frontal parts of the rotors of turbine-type generators of a large unit capacity. In the process of generator operating, the retaining ring is one of the most loaded elements. As a result, material of retaining rings should have high strength properties, sufficient plasticity and good magnetic inductivity. Deformation of rings by internal pressure is the most promising and effective way of their cold hardening, providing a favorable and uniform stress-strain state of the metal in the manufacture of non-magnetic retaining rings for powerful turbine-type generators. Since the finished ring must acquire specific dimensions and a specified deformation degree in the process of cold hardening, the urgent task is calculation of the billet dimensions. The existing calculation procedure relies heavily on experimental manufacture data and is applicable only to a narrow range of rings, which reduces the accuracy of calculation and, ultimately, leads to an increase in ring allowances and a decrease in the metal utilization factor. In this research work a new technique for calculating the initial dimensions of rings, which is based on the incompressibility condition was developed and proposed. Taking into account the assumed boundary conditions, a system of two equations with three terms is compiled. To solve an incomplete equation system, it was suggested to introduce additional equations – in first version of the technique, the well-known solution of Nadai was used. In the second version – the condition of constancy of relative thickness of the ring wall permissible from the experimental data of deformation of rings of different sizes was used. The results of calculating the rings initial dimensions for both proposed techniques were compared with the experimental data. The maximum deviation from experimental data does not exceed 4 % and the deviation average value does not exceed 1 %, which indicates a sufficiently high accuracy of the proposed calculation techniques and the possibility of using them in manufacturing practice.

Technogenic wastes are by-products of any production. At the same time, they can be a raw material for obtaining useful products. In particular, the waste from the Shabrovsky talcum combine, can be used to produce magnesian fluxes. They are dispersed, so must be agglomerated. Therefore, a method has been proposed for the preparation of non-roasting pellets. As a binder, a mixture of water and peat, treated in a hydropercussion cavitation device, was used. The resulting material is a colloidal system with particle size of less than 10^–4 m. To measure the particle size, dynamic light scattering method was used. For comparison, a similar mixture of water and peat treated in a planetary mill was studied. An analysis of the data obtained has shown that particles of micron size occupy up to 90 % of volume in the sample after treatment of the mixture in hydropercussion cavitation device. In a sample that was ground in a planetary mill, most of the particles are characterized by tens or even hundreds of microns. Determination of crushing strength of non-roasting pellets is performed by compressing in a tensile machine of model P-0.5. For this purpose, the granules were used both immediately after granulation and after drying at 105 °C to a moisture content of less than 1.5 %. With an optimum proportion of binders of 15 – 20 %, the strength of raw pellets was 15 N, and the strength of dry pellets was 90 N. With a binder percentage of less than 15 %, both raw and dried pellets had low strength. With a binder content of more than 20 %, the mixture had excessive plasticity and tackiness, which led to the formation of conglomerates of several granules. Despite the fact that the strength parameters of the non-roasting pellet are lower than those of pellets used in blast-furnace production, they are sufficient for use in steelmaking processes.

The paper proposes a method for calculating convective heat transfer in the interaction of a single circular jet with a flat surface. The differences of the proposed method from the existing ones are given. The concepts “energodynamic potential of the flow” and “energodynamic power of the flow” are introduced, allowing to determine the intensity of convective heat transfer at “gas-solid” boundary. Differences of the proposed definitions from the existing ones are given: heat flux and heat flux density. The principal difference between the heat flux density q and the energy dynamic potential q_э is as follows: the heat flux density q for convective heat transfer problems means the amount of heat that is transferred from a liquid to a solid surface (or vice versa) per unit of time through a unit of heat exchange surface area. Thus, quantity q characterizes the intensity of convective heat transfer process at the interface. The energy dynamic potential q_э characterizes the flow property as a source or carrier of heat. Value of q_э characterizes the specific energy power of the fluid flow. When calculating the heat transfer, it was proposed to divide the jet when interacting with the flat surface into two parts: before the interaction – the jet part, after – the fan flow. The method for calculating convective heat transfer under jet heating, in which the Reynolds criterion calculated by characteristics of the gas at the nozzle exit is decisive, is not entirely correct. It is proposed to use criteria specific to the fan flow. Characteristic values for the fan flow are its initial average velocity U_вп, distance from the critical point of the jet (point of intersection of vertical axis of the jet with the surface) to the current coordinate of radius downstream. To assess the changes in basic characteristics of a free jet at different distances from the nozzle exit to limiting surface, dependences of the following criteria are presented: jet expansion coefficient; jet injection coefficient; velocity coefficient for any jet section; velocity coefficient for any jet section, except h/d₀ = 0; relation of the Reynolds criteria, confirming the need to carry out calculations of heat transfer on the values characteristic separately for the fan flow.

 Influence of introduction of tungsten powder and tungsten concentrate into surfacing flux-cored wire on structure, structural components microhardness, hardness and wear of the surfacing layer has been studied. Flux cored tungsten-containing wires of H- and E-types according to the IIW classification were manufactured for surfacing in laboratory. Powders of silicon KR-1 (GOST 2169 – 69), manganese MR-0 (GOST 6008 – 82), chromium PKhA-1M (industrial standard TU 14-1-1474 – 75), vanadium VEL-1 (industrial standard TU 48-0533 – 71), nickel PNK-1l5 (GOST 9722 – 97), aluminum PAP-1 (GOST 5494 – 95), tungsten PVT (industrial standard TU 48-19-72 – 92) and iron powder PZhV-1 (GOST 9849 – 86) were used as fillers. In some wires tungsten concentrate KSh-4 (GOST 213 – 83) produced by “AIR” mining company” JSC was used instead of tungsten powder. Gas cleaning dust of aluminum production of the following chemical composition: 21.00 – 43.27 % Al₂O₃; 18 – 27 % F; 8 – 13 % Na₂O; 0.4 – 6.0 % K₂O; 0.7 – 2.1 % CaO; 0.50 – 2.48 % SiO₂; 2.1 – 2.3 % Fe₂O₃; 12.5 – 28.2 % C_gen; 0.03 – – 0.90 % MnO %; 0.04 – 0.90 % MgO; 0.09 – 0.46 % S; 0.10 – – 0.18 % P (by weight) was used as a carbon-containing reducing agent. Wire with diameter of 5mm manufactured at laboratory installation ASAW 1250 tractor was used for surfacing. Surfacing modes were: I_s = 400 – 450 A; U_d = 32 ÷ 36 V; V_s = 24 ÷ 30 m/h. Surfacing was performed under a layer of AN-26S flux and flux made of silicomanganese slag; number of deposited layers – 5. Chemical composition of deposited metal was determined, metallographic analysis of deposited layer was carried out: size of the former austenite grain, size of martensite needles, degree of contamination by nonmetallic inclusions were stated and wear tests were carried out, hardness and microhardness were measured. The possibility in principal of using tungsten concentrate instead of tungsten powder in studied flux cored wires is shown, degree of tungsten extraction was calculated. For H-type fluxcored wire, introduction of tungsten concentrate instead of tungsten powder into the charge of wire does not increase contamination of deposited layers with nonmetallic inclusions and reduces size of the primary austenite grain. Use of tungsten concentrate in E-type flux-cored wire manufacturing helps to reduce size of the primary austenite grain and size of martensite needles, increasing microhardness of martensite in structure of deposited layer. Introduction of tungsten concentrate instead of tungsten powder into the composition of the charge of H-type wire provides a significant increase in hardness and wear resistance of deposited layer.

At present time, metallurgical wastes are used in metallurgical alloys production more and more. The volume accumulation and increase of return age effect on charge pollution by undesirable elements and nonmetallic inclusions. As a result, structure and properties of the casting inevitably get worse. This circumstance must influence on polytherm’s character of physical properties of the melt, necessary temperature and time parameters of the heat-resistant alloy’s melting accordingly. We have researched the temperature dependences of electrical resistance and kinematic viscosity of liquid heat-resistant composites based оn Ni – Nb – Cr – Mo systems. The critical temperatures were determined for the EP902 alloy. Heating up to these temperatures leads to irreversible changes in direction of the melt improving. Interaction was found between the amount of foundry waste and features of temperature dependences of the melt physico-chemical properties. An increase in the amount of foundry waste using in remelting results in the critical temperatures increasing. Influence of the melt conditions on crystallization process and on the structure of hard metal has been studied. The process of alloy EР902 solidification was researched by differential thermal analysis method. It has shown that the crystallization process starts with extraction of solid solution on the base of γ-phases and ends with forming of the eutectic based on the Ni₃Nb intermetallic compound. Heating of the melt over the critical temperature leads to an increase of supercooling and does not effect on the eutectic temperature. The processing mode of the high temperature melt treatment was proposed based on the research results of physico-chemical properties of the liquid metal and process of the melt crystallization. It allows obtaining the highest quality of casting of heat-resistant EР902 alloy, which contains significant amount of foundry waste in the charge. The mechanical tests were implemented for experimental samples melted out by the optimal mode of high-temperature melt treatment (HTTM). Application of HTTM for the melts, contained 50 % of foundry waste in charge, allows obtaining the level of strength and plastic properties exceeding the technical requirements, stabilizing and combining it from melt to melt.

The powder metallurgy method was used to obtain materials in the form of a single-phase alloy based on Ni₃Al and in the form of composite material (Ni₃Al + W) with cell structure based on it. The structural unit of the composite material was a round granule (grain) with average size of 25 μm from nickel alloy, on which the continuous tungsten coating with thickness of ~0.4 μm was deposited by chemical vapor deposition. Compression tests at room temperature have shown that the yield stress of composite material (Ni₃Al + W) with cell structure at temperatures of 20 – 1000 °C is higher than of single-phase Ni₃Al-based alloy (up to 1.7 times), but at higher test temperature the yield strength of the composite is compared with the yield strength of the nickel alloy. The specific yield strength (that is, normalized for the density of 7.8 g/cm³ for the alloy and of 9.5 g/cm³ for the compo site) behaves similarly. At the temperature of 1300 °C, single-phase Ni₃Al-based alloy exhibits solid-liquid behavior under compression. Creep tests were carried out for compression under vacuum at temperatures of 1000 – 1200 °C. Using the pair and parametric methods of mathematical analysis of creep processes according to Hollomon, regression equations of creep rate, stress and temperature of the test were obtained. The ultimate strength of creep for the given tolerances for steady-state creep rate and inverse values were calculated. It is shown that at all test temperatures the composite material has lower creep rate (up to 7 times) and higher ultimate strength of creep (up to 2.5 times) than the nickel alloy on which it is based. Creep activation energies of the materials studied are determined using the exponential law of coupling of experimental values. The creep activation energy for the nickel alloy found is close to the activation energy of nickel self-diffusion in Ni₃Al and materials based on it (230 ÷ 310 kJ/mol), and for the composite – to self-diffusion activation energy of tungsten (503 kJ/mol).

The promising direction in improving the strength properties of low-carbon steels is the use of controlled rolling providing formation of structures with prevalence of a bainite component. Analysis of the references has shown that now there are no detailed researches which allow to approve what morphological type of bainite provides the most optimal properties. In this regard in the present work the influence of cooling rate on the structure, properties, and structuralphase transformations of low-carbon complex-alloyed pipe steel containing 0.062 % C; 1.80 % Mn; 0.12 % Mo; 0.032 % Cr, 0.90 % Ni and other elements (Al, Cu, V, Nb, Ti) was studied. The dilatometric method was used to construct the CCT diagram of the decay of supercooled austenite of low-carbon complex-alloyed pipe steel. The qualitative and quantitative analysis of microstructure was carried out and hardness after various speeds of cooling was determined. There were identified the cooling rates providing bainite structures and increase in the strength properties of steel with specified composition. At a cooling rate since 0.05 to 6 °C/s, along with ferrite, a globular bainite is formed in the microstructure, consisting of bainitic α-phase and “islands” of martensite-austenite component ranging in size from 1 – 6 μm. At a cooling rate of 6 °C/s, conversion to reed bainite is observed, along with the borders of which the carbides and residual austenite are located. At cooling rates of more than 16 °C/s, bainite becomes bag-rack. With an increase in cooling rate from 50 to 150 °C/s, the average width of the bainite α-phase rails decreases from 2.22 to 1.32 μm.

 Thermodynamic analysis of the effect of silicon on the solubility of oxygen in Ni – Co – Cr melts has been carried out at 1873 K. Silicon at low contents practically does not affect the concentration of oxygen in Ni – Co – Cr melts, which is determined by the chromium content. With a higher content of silicon after changing the interaction mechanism of chromium and silicon with oxygen, when silicon already determines the solubility of oxygen in the melt, the oxygen concentration decreases. However, the deoxidizing ability of silicon at elevated contents in Ni – Co – Cr melts is much lower than in Ni – Co melts.

The effect of electric field on the gas content of cast iron has been experimentally established on the basis of electrochemical studies in the system “liquid cast iron – slag – gas phase”. The author has carried out the studies aimed at obtaining cast iron sparingly alloyed with nickel, equal to Ni-resist cast iron in its mechanical and performance characteristics. For this purpose, austenitic cast irons melted in induction furnace with electrocorundum lining have been studied. Samples prepared from the obtained cast iron have been subjected to further treatment with electric field in order to research the influence of static electric field on fixation of atomic nitrogen in the alloy, and ultimately, on the structure of metal matrix. According to the experimental data, the effect can be enhanced by application of electric field. The application of negative charge to metal appears to be more effective, although, in case of anode metal, certain “capture” of nitrogen in cast iron also occurs. This may be explained by the fact that, at the initial moment of time, there is a stationary electric field between the movable (free) electrode and surface of the melt, where the charged particles are stationary in this reference frame, which is registered as no current by ampere-meters integrated in the circuit. The application of static electric field facilitates is capture of nitrogen in cast iron. According to further experiments, at 8 – 9 % of Ni, it is necessary to apply significant voltage for the manifestation of this influence. The studies have shown that the issue of stabilizing austenite with nitrogen in cast iron was not so simple, and, apparently, the influence of the field in case of the introduction of nitrided ferrochrome affected decomposition of nitrides, recharging of nitrogen ions, and non-equilibrium conditions of their diffusion and transition to gaseous phase. It was confirmed by a wide variation of the results of nitrogen analyses. Some samples have shown 0.04 – 0.05 % of N (with the introduction of nitrided ferrochrome, and a “minus” applied to metal), but most analyses have indicated considerably lower values. For foundry industry, electrochemical deoxidation of alloys that are difficult to deoxide by other methods, e.g. aluminum cast iron alloy, is of particular interest. Aluminum is an active element, which, in case of unfavorable arrangement of mass flows, is difficult to remove even using calcium. It leads to the emergence of Al₂O₃ inclusions in metal with the density close to melt, which complicates their coagulation and emersion. A double deoxidation has been tried. After the melt’s exposure lasted for 1 hour, its EMF has almost “returned” to its initial state (0.8 V). The subsequent deoxidation of melt for 15 minutes facilitated three-fold decrease in oxidation degree as compared to the initial one. Thus, the possibility of electrochemical deoxidation of iron-carbon melts and expediency of double deoxidation have been experimentally proved. As a result, the method of applying electric field in order to change the gas content of cast iron, as well as the method of practical application of electrochemical deoxidation of iron-carbon alloys have been suggested.