CUTTING STONE BUILDING MATERIALS WITH CUT WHEELS OF CUBIC BORON NITRIDE

The advantage of cutting stone building materials with SSM (synthetic superhard materials) wheels is that, first of all, it is possible to obtain high processing productivity and dimensional stability, which are 3..5 and 50…100 times higher than those of traditional tools based on carborundum, respectively. The study of the process of cutting stone materials with CBN (cubic boron nitrite) wheels is aimed at establishing force dependences, determining the cutting power and heating temperature of the cutting disc during operation. The forces were measured using a tensometric dynamometer UDM-50. To measure and calculate the cutting temperature, a thermoelectric method based on the formation of practically not inertial microthermocouples during cutting was used. The temperature to which the CBN cutting wheel on a metal base is heated is a limiting factor in processing, since when heated to a temperature of 600ºС, the strength of the wheel decreases by half, which can cause its rupture under the action of centrifugal forces, as well as loss of stability and jamming during cutting. In the present study, the wheel temperature was measured after one minute of continuous operation. The values of the component of the cutting force PY, depending on the processing modes, can reach values of the order of 70 N. The values of the component of the cutting force PZ, depending on the processing modes, can reach values of 45 N. The cutting power can be 2800W. The temperature resistance of the wheel (heating time of the wheel up to 600ºС) when cutting dry is maximum 28 minutes, when grinding with cooling of the cutting zone with negative temperature air from a Ranque-Hilsch tube, the temperature resistance is 35 minutes, with ejector cooling of sprayed coolant 37 minutes and with jet-pressure cooling it is 40 minutes. The maximum cutting length is respectively 0.7: 0.8; 0.9 and 2m. The cutting power is 600...2800W.

Efeito da soldagem nas propriedades mecânicas e metalúrgicas do aço API 5L X65

Este estudo avaliou as propriedades mecânicas e metalúrgicas de uma junta de topo soldada em tubulação de aço API 5L X65, aço microligado, amplamente utilizado na indústria offshore. O procedimento inicia com o revestimento (cladding) da região a ser soldada e vizinhança com metal de adição, através do processo de soldagem TIG que também é utilizado nos diferentes passes de raiz. O revestimento da junta soldada foi realizado pelo processo SMAW. Esses procedimentos de soldagem foram avaliados com a utilização de corpos de prova, submetidos a ensaios mecânicos e metalúrgicos requeridos por normas aplicáveis à indústria offshore. Adicionalmente, foram realizados ensaios complementares, relacionados ao tamanho de grão austenítico na Zona Termicamente Afetada (ZTA) e Zona de Fusão (ZF). Concluiu-se que o procedimento de soldagem utilizado pode ser largamente aplicado na indústria, sem comprometimento significativo do metal base, ZTA e ZF, minimizando a necessidade de tratamentos térmicos posteriores. Palavras-chave: Soldagem. Cladeamento. Microligado.

Increasing the tribological properties of the sur-face layer of cast iron by treatment in the envi-ronment of overheated steam of aqueous solution

The formation of the surface layer of cast iron during the processing of cast iron in the environment of superheated steam of an aqueous solution of salts is considered. An ecologically cleaner method of chemical-thermal treatment is offered. The article considers the surface layer obtained in the environment of superheated steam of an aqueous solution of water-soluble salts of ammonium molybdic acid. The layer is formed on the surface of the matrix and around the graphite inclusions. The impact of temperature on the formation of a multilayer coating by increasing the temperature in contact with the metal surface is the dissociation of chemical compounds in solution, with the formation of atomic oxygen, sulfur, nitrogen, molybdenum. The formation of the surface layer occurred not only on a metal base, but also on the boundaries of graphite, both lamellar and globular, coming to the surface of the metal without breaking the solid layer. It is established that as a result of interaction of technological parameters of temperature, holding time and concentration of saturated medium graphite in the surface layer changes its shape, becoming spherical, although in the matrix it had a lamellar shape. It is multiphase and contains soft and hard structural components. Comparative studies have shown that the wear rate of untreated cast iron is much higher than that of treated cast iron, and reaches 0.8 ∙ 10-4 μm/km at a load of 400 N. This increases the wear resistance of cast iron and at the same time improves the workability reducing the coefficient of friction. The effect of the coating on the workability show that the stabilization of the friction moment occurs faster in samples with a multilayer coating. Thus, for gray cast iron with lamellar graphite, the stabilization time of the friction moment in a multilayer coating is 0.6 h compared with 2 h for a single layer coating; in high-strength cast iron it is, respectively, 5.2 and 6.3 hours.

HIGH TEMPERATURE CORROSION OF THIN SHEET STEEL 08KP IN AIR

The study of the nature of high-temperature corrosion of metals is one of the tasks in substantiating the relevance of the use of corrosion-resistant, heat-resistant coatings and barrier layers obtained on the basis of the natural oxidation process. The article presents the gradation of oxidation of surfaces of 08kp thin-sheet steel at diff erent temperature-time parameters of one cycle “heating-cooling”. To regulate the processing modes and register thermal eff ects, a diff erential thermal analysis device was used. It is shown that the eff ect of elevated temperatures on steel in air at atmospheric pressure triggers an intensive growth of scale, which peels off from the metal base and breaks down. After descaling on the steel surface, in addition to blue tarnishing, in some cases, fi lms of a red tint were found. Based on the data of diff erential thermal analysis, an att empt was made to separate and interpret transformations related directly to steel and to reactions in scale associated with iron oxides.

Hydrometallurgical Treatment for the Extraction and Separation of Indium and Gallium from End-of-Life CIGS Photovoltaic Panels

This study presents experimental results for the development of a process for the recovery of indium and gallium from EoL CIGS (CuGa1−xInxSe2) panels. The process consists of a thermal treatment of the panels, followed by a hydrometallurgical treatment, where quantitative leaching of In, Ga, Mo, Cu and Zn is achieved. The elements are subsequently separated and recovered from the leachate by solvent extraction. For the development of the process, samples of EoL CIGS PV panels were used, which contained a thin film of Mo (metal base electrode), sputtered on the supporting soda-lime glass and covered by the thin film containing In, Ga, Cu and Se (1 μm). These films were detected by SEM-EDS in polished sections. The thermal treatment at 550 °C for 15 min, in excess of air, led to the successful disintegration of ethyl vinyl acetate (EVA) and delamination of the thin film-coated glass from the front protective glass. The glass fragments coated by the thin film contained the following: Se: 0.03–0.05%; In: 0.02%; Cu: 0.05%; Ga: 0.004–0.006%; and Mo: 0.04%. Following thermal treatment, thin film-coated glass fragments of about 1.5 cm × 1.5 cm were used in acid leaching experiments using HNO3, HCl and H2SO4. Quantitative leaching of Cu, Ga, In, Mo, Zn and Cu was achieved by HNO3 at ambient temperature. The effects of pulp density and acid concentration on the efficiency of metal leaching were investigated. Part of Se volatilized during the thermal treatment, whereas the rest was insoluble and separated from the solution by filtration. Finally, the separation of the elements was achieved via solvent extraction by D2EHPA.

Polymerase-mediated synthesis of artificial RNA-DNA metal base pairs

Metal-mediated base pairs are formed by the connection of two nucleobases via coordination to a metal cation. The resulting metal-containing duplexes have been used in a large variety of applications ranging from allosteric control of functional nucleic acids to the construction of nanowires. Recently, enzymatic approaches are being developed for the construction of metal-mediated base pairs. Here, we have studied the possibility of constructing HgII- and AgI-mediated DNA/RNA hetero base pairs using primer extension reactions. The high kinetic and thermodynamic stabilities of metal base pairs can be harnessed to trigger the formation of multiple rU-HgII-dT base pairs.

Refinement of the method for selecting the width of the conductor of printed circuit boards on a metal base, working in the absence of convection

The article proposes a refined method for calculating the width of the conductors of printed circuit boards on a metal base for the onboard devices of spacecraft, depending on the current flowing. The constructed refined mathematical model of the process of conductive heat exchange between the conductors and the metal base is described. The results of calculations of various, most common, locations of layers of printed circuit boards are presented. An analysis was carried out and a refined methodology was developed based on the results obtained. It allows you to easily (without complicate calculations) calculate the necessary values of the width of conductors. This technique is based on graphical methods, but allows you to perform technical calculations with sufficient accuracy. Accuracy is achieved by using special formulas that simplify the determination of the value of a physical quantity on a logarithmic scale. The disadvantages of the proposed method are indicated.

On a possibility of replacing grey cast iron for manufacturing cast elements of electrolyzer gas collecting bell

The main process leading to the destruction of the cast elements of gas-collection bell of electrolyzer, made of grey cast iron, is the oxidation of iron by oxygen, SO2 gas and sulfur vapors to form magnetite, hematite and pyrrhotin. The simultaneous formation of iron oxides and sulfides does not prevent further corrosion, since scale is formed with a loose structure that does not have protective properties. Reducing the length of the interfacial boundaries inside the material of the cast enables to reduce the rate of corrosion destruction, which can be achieved by modifying the cast iron to change the shape of graphite inclusions, i.e. obtaining high-strength cast iron with a spherical shape of graphite inclusions. However, the obtaining spherical graphite in cast iron using magnesium modification does not exclude the access of aggressive gases to the surface of the products and the possibility of their diffusion along the grain boundaries. It was shown that alloying can be an alternative, which leads not only to the exclusion of lamellar secretions of graphite in the structure of cast iron, but also to the formation of surface oxide layers based on the alloying element preventing the corrosion. Alloying with chromium gives cast iron high abrasive resistance due to the presence of a carbide component in the structure, as well as corrosion resistance due to the alloying of the metal base, heat resistance due to increasing the electrochemical potential of the metal base and creating a strong neutral oxide film on the surface of the castings, heat resistance, etc. An experimental comparative analysis of the corrosion resistance of cast iron used for manufacturing of gas collecting bell of electrolyzers showed that chromic cast iron ЧХ3 has a higher corrosion resistance than high-strength cast iron with spherical graphite ВЧ50 and much higher than grey cast iron with lamellar graphite. However, chromic cast iron ЧХ3 has low casting properties, is very sensitive to the cooling rate and has a large heterogeneity in structure, which makes it difficult to use it for the manufacture of gas collecting bell of electrolyzers.

Adhesives for the Installation of Cast Basalt Elements on Metal and Comparison of Properties when Using Different Types of Fillers

The polymeric adhesives for the installation of basalt elements on a metal base are designed primarily for environments with increased chemical and mechanical stress. They are composed of polymer resins (epoxy, polyurethane) as binders, as well as organic additives and mineral admixtures that mainly fulfill the function of filler. In all sectors of today's construction industry, maximum efficiency in the production of materials is required for sustainability purposes, which, however, must never be at the expense of the quality or the required performance. Due to these requirements, great emphasis is placed on the maximum use of secondary raw materials. Talc is used as the primary filler for polymer adhesives. Sawdust, tire rubber, and fly ash are used as secondary raw materials. The use of these in building supplies can positively affect some physical and mechanical properties of polymeric adhesives. Also, the use of secondary raw materials has the above-mentioned ecological benefit. Basic properties, such as bulk density and adhesion to both metallic and basalt elements, were monitored. The details of the cohesion of the adhesive with the bonded material, as well as the distribution of secondary raw materials in the polymer matrix, were assessed microscopically.

Study of making the SnO2/Sb2O3 membrane mixture on aluminum metal base as insulation and heat transfer material

SnO2 materials are attracting the attention of many scientists, because nano-sized SnO2 materials are applied to sensor, new energy, semiconductors field, etc. A typical application when coating SnO2/Sb2O3 on aluminum substrates is as a thermally conductive insulating material for electronic components such as IC cooling, microprocessors, leds, .... When changing factors such as pH solution, dipping time, calcination and calcination temperature, the structure and morphology also change, leading to changes in physico-chemical properties. The research on synthesizing nano SnO2/Sb2O3 (0.6%) by hydrothermal method brings very good results because this material has both insulating ability and high chemical and electrochemical strength, low toxicity to environment.Aluminum base is a material with mechanical strength (plasticity, malleability), high chemical resistance, good heat dissipation. When coated with SnO2/Sb2O3 on an aluminum base, this material can become a heatsink integrated board for accessories and electronic equipment (resistance value from 5÷ 15MW, thermal conductivity reaching 93.4% efficiency).