Bulletin PNRPU. Mechanical engineering, materials science

Universal tendencies in manufacture of railway rails are directed on increase in length of rails, increase of their hardness, decrease in level of internal residual pressure, maintenance of the profile of level of properties differentiated on section, and also application of technologies of thermal processing saving up resources with use of non-polluting cooling environments and use is economical - the alloyed marks of steels. For the purpose of maintenance of let out production to modern requirements in 2012-2013 on joint-stock company “EVRAZ ZSMK” radical reconstruction of rail manufacture with development of technology of the differentiated heat hardening of railway rails with use of heat of rolling heating is spent. During development of new technology a number scientifically-research works on revealing of an optimum chemical composition and modes of thermal processing of rails has been spent. In the given work results of research by means of electronic microscopy of a microstructure of rail steels of four various chemical compounds on the basis of a perlitic steel of mark Э76ХФ in accordance with GOST R 51685 carbon different by the maintenance, manganese, silicon, chrome, vanadium are presented. Besides, two skilled fusions in addition micro alloyed by niobium. Research spent on the samples who have been cut out from not heat strengthened rails of type Р65, rolled from continuously cast preparations of swimming trunks of a skilled chemical compound. Samples before research heated up to temperature 950 °С and subjected to the accelerated cooling in the air environment with a speed of 1-5 degrees a second. By results of research influence of the maintenance of the basic and microalloying chemical elements on parametres of a microstructure of rails is established. Rational speeds of cooling of a rail steel of the various chemical compound, providing formation of optimum parametres of structure of metal are defined. It is established that the most homogeneous microstructure Small disperse a perlite in wider range of speeds of cooling (to 3 degrees a second) is formed in a rail steel with the moderate maintenance of chrome (0,46%), manganese (0,78%), the raised maintenance of silicon (0,55%), the carbon maintenance close to eutectoid to structure (0,79%) and microalloyed by vanadium in number of 0,07%.

The article is devoted to experimental and theoretical analysis of the process of flat grinding by a wheel end face, taking into account the specifics of the elastic suspension of the grinding head. Difference between the power circuit of the kinematic and geometric chain “grinding wheel - machined surface” is shown. Feature of the power circuit of the kinematic chain is spontaneous formation depth of cutting during grinding process. The formation depth of cutting depends on such factors as contact pressure, the geometry and physic mechanical properties of the machined surface, cutting conditions, etc. A mathematical model for determining the depth of cutting at the power circuit of the kinematic chain of technological process is presented. The model showed quantitative correlation between the cutting depth of the grinding wheel and a complex of factors correlation The received correlation allows to use cutting depth as a controlled parameter of machining. The results of experimental verification of the mathematical model are given. The deviation between calculated and experimental results does not exceed 12%. The possibility of practical implementation of the research results, using example of the technological process of grinding rails by rail-grinding trains, is shown. The method of setting cutting conditions for rail grinding is offered. Industrial testing of method showed opportunity to raise the quality of rail grinding work in terms of increasing the accuracy of formation geometric shape of rails and provide required level of quality of machined surface. The results of research allowed to make the grinding technology by wheel end face using elastic suspension grinding head control to be implemented in the field of optimization of the abrasive tool and improve the efficiency of the operation as a whole abrasive treatment.

In recent years on the OJSC "Magnitogorsk Iron and Steel Works" the leading enterprises of the Russia metallurgical industry the latest technology of production of modern and advanced types of cold-rolled products has been mastered. In rolling shop No. 11 in the head of the units of the second stage the consolidation of the rolls by laser welding method are carried out for the production of products for the automotive and construction industries, as well as for the production of consumer goods. The influence of the power of preheating and the final heating on microstructure and microhardness of welded joints at the integration of cold rolled products grade 10пс obtained by laser welding on Miebach laser machines in an environment of continuous process units in the new cold rolling complex are investigated. The description of the preheating and final heating are given. The features of these operations on the Miebach company welding machines are described. The description of research methods of welded joints made by laser welding are carried out in the framework of this work. Presented experimental welding modes for the welding of the cold-rolled stripes ends. The metallographic analysis results of the welded zone in the rolled low-carbon steel grade are shown. Based on a comparison of the experimental data revealed patterns of change in length of the welded joints structural zones according to the conducted heat treatment. Established that with increasing power of preheating and final heating the length of softening zone increases. Moreover by increasing the final heating power above 4,5 kW abruptly increases the recrystallization zone length and the length of softening zone, which leads to deterioration of the welded joints.

Mechanical properties of 38ХС steel after different conditions of the isothermal quenching in the bainite interval of temperatures and chrome-nickel-molybdenum-silicon steels with carbon content 0,18 and 0,27 % after slow continuous cooling in the bainitic temperature range with cooling rate v cool = = 5 °С/min were investigated. It was shown that after such heat treatments after such heat treatment the structure of carbide-free-bainite represented as two-phase mixture of carbon depleted bainitic ferrite and carbon enriched retained austenite with different morphology were formed in the investigated steels. The aim of this work was to research the influence of tempering at different temperatures on behavior of retained austenite and the mechanical properties of steels with the carbide-free-bainite formed during isothermal quenching and slow continuous cooling in the bainite range of temperatures. The main methods were electron-microscopic investigations of the peculiarities of bainite structure formed during isothermal heating of 38ХС steel and slow continuous cooling of chrome-nickel-molybdenum-silicon steels 18Х2Н2СМ and 27Х2Н2СМ mechanical tests and measuring of crystal lattice parameters of the retained austenite presented in steels structures after different heat treatments including tempering at various temperatures. Retained austenite in such carbide-free-bainite is substantially enriched with carbon and contain the considerable part of steel total carbon content. It was shown that tempering at a temperature of 300 °С during 1-2 hours raise the values of impact strength of isothermally quenched steel 38ХС and steels 18Х2Н2СМ and 27Х2Н2СМ after the slow continuous cooling, having in a structure different correlation of lower lath and upper globular bainite, retained austenite and martensite. It was found that at such tempering it happen the retained austenite stabilization by means of the noticeable increasing of carbon content in it.

In this article the influence high-temperature heating on microstructure aluminum and titanium electro-spark deposits was considered. Electro-spark procedure was carried on conventional parameters by means of rotating electrode atop surfaces sheet - samples of low carbon steel in air environment. High-temperature Joule-heating was realize with use new device, based on welding transformer TSD-1000-3, with attachment analog-to-digital converter for voltage-, current- and temperature monitoring. Heating speed was maximum close to real welding heating speed. Was fixed, that after electro-spark alloying by means of both electrodes formed hard deposits contained cracks and heat affected zone below. For aluminum deposit, high-temperature heating perform it to whit more thick layer with low micro-hardness. In heat affected zone was appeared more rich ferrite partially decarburization zone. In place former titanium deposit was appeared local small volumes of melting with dendrite structure and middle micro-hardness. Below it located thin completely decarburization zone and large (about 1 mm) partially decarburization zone. Monitored temperature data was shown local melting for both deposits in range 500-650 °C, that was reason for observed structure changes. Equilibrium structural diagrams iron-aluminum and iron-titanium shows eutectic in same temperature range.

Formation of the welding seam during the electron beam welding is a complex process. It’s a result of many factors (heat and mass interchange, gas liberation, dispersion and reflection of the elect- ron beam, etc.) working together and produced by the impact of the concentrated energy source - bunch of electrons on the welded materials. Complexity and multi-faceted nature of this welding type creates many issues that need to be solved during the process using technical tools to control welding seam formation to deliver the required quality of the welding seam. Visual observation can become one of these tools to study physical processes occurring in the welding channel and used to control formation of the welding seam. Concomitant breaking X-ray radiation is practically the only source of the information for this purpose. This paper provides research results for implementation of visual observation of the welding channel in the X-ray spectrum. We look at the method of creating a stereoscopic image of the welding channel by means of commutation on the screen of the two axonometric images of the channel and observing them with a binocular device which has the transparency of the left and right oculars commuting in sync with the commutation frequency of the axonometric image. Every axonometric image of the welding channel is received through a formed data array about the topography of the welding channel. For each axonometric image, signals about electron beam penetration into the material are captured from various points in the vicinity.

The article deals with modern methods of controlling an electron beam in electron beam welding. By these methods include pulse modulation of the electron beam current leads to a change in heat input; vibrational impact beam focal plane displacement in the vertical (dynamic focus) weld formation in electron beam welding; oscillation beam with various scan directly on the junction of the weld joint leads to an increase in the area of ​​the beam action area; multibeam (mnogovannovaya) welding, at which an electron beam is scanned over the surface of the article with a high frequency (about 5 kHz or more) to several points from one to the other and back, each located at a distance from each other; multifocal welding, resulting in a synchronous dynamic change in focus and deflection of the electron beam to a specific point. Application of these methods is aimed at eliminating specific defects in welds, such as root defects (Pointed depth of penetration, the presence of voids or poor fusion), extended cavity in the seam volume, the "middle" crack and seam deviation from the joint due to residual or induced magnetic fields. It is also possible carrying out welding in several treated areas, welding or welding to form a plurality of consecutive baths each other, or a combination of welding and heat treatment. Multipath technique can be successfully used in combination of dissimilar materials, such as bronze worm wheel rim to the hub of the cast iron or steel wheels to reduce the cost, as well as other compositions for welding, for example, copper or tungsten steel with aluminum through a copper gasket.