Bulletin PNRPU. Mechanical engineering, materials science

The polytherms of the properties of multicomponent melts differ significantly from polythermal pure metals. They are almost never monotonous, let alone linear. For each grade of alloy (steel), the temperature dependences have their own characteristic appearance with features caused by the composition, the raw materials used in their manufacture, and also the specificity of production. For the first time in the conditions of JSC "Vyksunsky Metallurgical Plant" an experimental work was carried out to study the physical properties and structure of tubular steels near the phase transition. The temperature dependences of the structure-sensitive properties of iron-based liquid alloys are studied. The polytherm of heating revealed special points and areas. All the polyterms constructed are characterized by a mismatch between the heating and cooling branches (hysteresis), which indicates a disequilibrium in the structure of the samples after their melting. Heating the system to temperatures tan ensures the presence of stable hysteresis and indicates a multi-stage transition to equilibrium. As a result of the work, new experimental data were obtained on the physical properties of carbonaceous melts on the basis of industrial pipe steel grades (steel grade 22GYU) produced in electric arc furnaces. The influence of charge materials on the physical properties of melts has been studied. The kinematic viscosity and surface tension of industrial melts of iron-based pipe grades in the temperature range from the liquidus with an excess of 100-200 °C were measured. As a result of the experiment, polytherms obtained by measuring the kinematic viscosity and surface tension on samples of two melts have been constructed and given for visual comparison using various types of charge materials. To test the results, another 20 samples were analyzed from real melts, smelted in accordance with the current orders in the casting and rolling complex. Based on the experimental data obtained, the following recommendations were issued: maximum heating in the EAF furnace to a temperature of 1670 °С, holding for 5-10 minutes for homogenization of the melt, output of melting from the furnace. Recommendations are given on the further temperature preparation of melts of pipe marks on the basis of iron. At the same time, the issue of the resistance of the refractory lining of steel casting ladles is of particular importance in connection with higher temperatures of melting from an arc furnace.

Technological residual macro-stresses that arise in the process of manufacturing responsible and expensive engineering products by methods of cutting or processing metals by pressure determine their quality, resource and reliability during operation. For a number of products, the level of residual macrostress is regulated in the design documentation, which requires the development of technologies for controlling their level using non-destructive methods. The control of the level of residual macrostresses by methods of nondestructive testing in the surface layers of products is actual. The article describes the results of studying the effect of processing regimes on the level of residual macrostress using the X-ray diffractometry method using the robotic complex XStress 3000 robotic complex. Objective: to study the effect of machining regimes of 38KhN3MFA steel on residual macrostresses. The methods used: X-ray diffractometry was used, which allow to determine the residual stresses in the surface layer of products from any polycrystalline materials. Used equipment: X-ray diffractometer 3000. Novelty: the dependence of change in residual macro-stresses for 38KhN3MFA steel under various cutting regimes has been experimentally obtained. The dependence of the level of residual macro-stresses on the parameters of the cutting-feeding and cutting rates has been established. It is shown that, in the selected range of parameters of cutting conditions, the minimum level of residual macrostress is observed when using the cutting mode with minimum speed and feed. The obtained data can serve as a basis for creating a database of a technologist and will allow to control the level of residual macrostresses with the purpose of design- nating machining regimes in the design of technological processes, which will enable to improve the quality of products, increase the resource of equipment and reliability.

The processes taking place in the raw composition for the production of fluorophlogopite under heating depend on the kind of components of the raw composition, their mineral and chemical compositions, the structure, the particle size of the prepared dispersed raw materials, and a number of other specific features. The paper considers the analytical data and the results of experimental studies on the detection of the sequence of melting of the components of the fluorophlogic dust charge and the phase transformations occurring at temperatures from 100 °C to the temperatures of complete homogenization (≈1400 °C). Experimental results were obtained with the use of thermal analysis and in studying the sequence of melting fluorophlogopite samples in a resistance furnace with silicate electrodes. Details of the sequence of processes preceding the formation of the melt, their physical essence and chemistry are considered in detail. Analytical review of information on the structure-forming processes, allowed the authors to establish that the amount of fluorine-containing component of the charge, determines the amount of fluorophlogopite and the qualitative composition of the concomitant products of crystallization. The article establishes that the grain boundary of the batch is the reaction zone, and the area of their surface determines the rate of processes and reactions in this zone. The authors draw attention to the prospect of introducing a nanotechnological approach to modernizing the technology of obtaining fluorophlogopite, and also points to the principles of using mechanochemical treatment of charge components and the use of nanosecond electromagnetic pulses with high-concentrated electropulse energy to improve the operational properties of products from fluorophlogopite. The conducted research established the sequence of processes during heating and melting of the main components of the charge for obtaining fluorophlogopite: dehydration → solid-phase reactions → thermal decomposition of components → secondary reactions and sintering → formation of the liquid phase → melting → homogenization of the melt. Complete homogenization of the melt occurs at a temperature of 1380-1400 °C.

Results on development of a computation procedure and designing for metal-cutting plasmatrons are presented. It is noted, that the similar technique should be based on functional, systemic and optimal principles. Any method of designing DC arc plasmatrons should take into account the main factors of electroplasmic technologies, generalized principles and methods of their design. The principles of functionality, consistency and optimality should be the basis of such method. Special attention at designing it is necessary to turn on gas-dynamic factors and safety of plasma technologies. In this regard, the features of several known methods of gas-dynamic design of plasmatrons are considered. It is noted that they do not take into account the inevitable pressure losses arising in the areas of the gas-air path preceding the nozzle chamber (primarily in the swirl). Also, the asymmetry of the gas supply distribution along the section of the plasma torch path is not taken into account. The offered method includes calculation of gas-dynamic losses and plasma gas uniformity in cross-section of an air-gas path. The results of gas-dynamic analysis are used for profiling an air-gas path in view of design principles. Discussed the feasibility of applying specialized software for the study of processes and design of plasma torches. As an example, the work of the software package EFD.lab in the design of plasma torches for cutting metals is presented. Also presents the results of computer-aided design in electroplating technologies. The considered technique is applied for new plasmatrons development, including narrow jet plasma technology.

For a certain group of technological machines, the problem of increasing the wear resistance of working parts is studied, which, performing the functions of grip-feed, pressure and cutting, form pairs of friction steel-steel with the object of labor. A hypothesis has been put forward that the wear of the working parts is due to the formation in the process of friction of dispersed secondary microstructures with increased hardness as a result of chemical processes with the creation of strong covalent bonds. In this case, the initial reagents are carbide-forming chemical elements of the material of the working parts, the transfer of which into the lattice of the conjugated solid is realized by diffusion and adhesion processes. Experimental modeling of mass transfer processes and the formation of wear-out dispersed solid particles is achieved by reproducing these phenomena in conditions of deterministic friction using the example of the tribosystem high-alloy steel R6M5-carbon steel. In this case, the possibility of reducing the wear of the indenter by magnetizing it in a pulsed magnetic field is studied, based on the use of magnetic influence as an energy factor in controlling the process of mass transfer in the interaction zone of conjugated crystal lattices. Based on the results of microhardness measurements, the formation of secondary structures with high hardness, unattainable for strain hardening, was revealed. The conclusion is made about the decisive role in their formation of the mechanism of solid-solution hardening, initiated by the effect of self-organization in friction as a thermodynamic phenomenon. By studying the elemental content of the surface layer of the counterbody by spectral analysis using the Q4 TASMAN spectrometer, the principle possibility of transferring the carbide-forming elements from the indenter to the counter-body by diffusion and adhesion is established. The results of the evaluation of the effect of magnetic processing of the indenter on the transfer efficiency of these elements (in 7-20 times) are presented. Using experimental results and the foundations of materials science and tribology, it was shown that solid secondary structures can be carbide phases and intermetallides with an increased fraction of the covalent bond characteristic of these chemical compounds.

Products with helical surfaces are widely used in the automobile industry, machine tool manufacturing and tool industry. The helical surface machining, including spiraled flute of cutting tool, is a difficult analytical task in the cutting tool design. In connection with severization of requirements to metal-cutting tools quality, machining helical surface, the learn of disk tools installation options for machining helical surfaces is one of the most important and complicated problem in tool industry. This circumstance is explained by the fact that the profile of the helical surface does not match the profile of the tool, and the source data from the detail drawing is often defined in different cross-sections and different parameters: without taking into account the need to solve the problems of installation options choice: аw - the centre distance of detail and disk tool; e - the angle of crossing between the positive direction of the part axis and the negative direction of the tool axis (axial angle) and y - the rotation the end profile part relating to the line of the centre distance perpendicular. The method of blocking lines is proposed. It lets find the optimum parameters of the installation disk tools right without connecting curves and undercuts in the touch area of the helical surface profile with the tool of the second order. The analysis of blocking lines graphic forms depending on disk tools installation options, machining helical surfaces with a smooth undercut profile, is done. Research results that show the influence of the lean angle of helical surface to blocking lines form and installation options limits are given. It is found that with changing the lean angle of helical surfaces the installation settings tools also change. With the angle increase w - the setting y is growing, but the setting e is reduced. The most optimal installation settings can be achieved only if the angle w is in the range of 10° to 60°. Within these limits the approximate equality of angles t in the nodal points of helical surface profile is achieved.