DEVELOPMENT OF LOW-MELTING GLASSCERAMIC BONDS FOR HIGH RESOURCE DIAMOND-ABRASIVE TOOLS

Research is aimed at creating high-resource diamond-abrasive tools with a large-pore structure of the working layer, the use of which reduces the occurrence of grinding defects when processing materials sensitive to overheating. The formation of an open structure of the working layer ensures effective chip removal, which excludes a decrease in the сutting ability of the tool due to contamination with grinding sludge and creates favorable conditions for intensifying the processing of materials when using high-speed cutting modes. As part of the research, low-melting glass-ceramic binders for diamond-abrasive tools have been developed, which make it possible to increase the tool service life due to the prevention of diamond grains premature destruction and the creation of a large-pore open structure of the working layer. Using a set of calculated data about the main characteristics of glass compositions by factor planning means, the dependences «composition - properties» were determined and the area of optimal compositions of glass-ceramic bonds was established, which ensure sintering of a diamond-containing composite at a temperature of 550–650 °C. The efficiency of the use of alumino-silicate microspheres of technogenic origin as a structure-forming filler providing the formation of a large-pore structure is shown. The features of the chemical and phase composition of the technogenic spheres recovered from the fly ash of the Krivoy Rog TPP have been determined. It has been established that when the diamond-bearing layer of the tool is sintered in the shell of the ash spheres, crystalline new formations with high hardness (hercynite, mullite, maghemite, spinel) are formed. Using ash spheres and developed low-melting binders, which include up to 30 mass. % of glass waste, the laboratory samples of diamond-containing composites with open porosity of 45-50% were made. Studies of their microstructure and morphological features made it possible to determine the pore size (130-200 μm) and establish that during grinding, partial destruction of ash spheres occurs with the formation of additional cutting elements, which increases the tool cutting ability. The research results indicate the advisability of using the proposed approach for selection of the diamond-ceramic composite components and the modes of heat treatment of the diamond-bearing layer when creating a tool. This approach will significantly expand the possibilities of manufacturing large-pore diamond-abrasive tools with a high service life at minimal material costs and will improve the processing of parts made of difficult-to-machine materials.

Effect of the heat treatment mode of high chrome iron rolling mills on chrome redistribution in the stress field

Heat treatment is an important stage in the technology of rolling rolls, due to the fact that the thermal stresses that occur during rapid or uneven heating summing up with the rather high residual stresses after casting, create a risk of cracking. Goal. The aim is improving the quality of rolling rolls by varying the modes of heat treatment. Therefore, it is important to assess the level of thermal stress. Method. Evaluation of thermal stresses arising in heating and cooling in the heat treatment process that summing up to the relatively high residual stresses after casting, creates the risk of fractures. The profile of the distribution of chromium in the cross section of the working layer at each time under the action of the stress gradient that occurs during heat treatment of the roll is obtained by calculation. Results To ensure a minimum temperature difference between the surface and the core, it is necessary to reduce the heating and cooling rate, as well as increase the duration of exposure at a given temperature. Reducing the cooling rate from 17 to 3.7°C/h decreases the temperature difference at the surface and in the center of the roll and the intensity of thermal stresses from 29 to 7 MPa. It is established that the rate of heating and cooling should not exceed 10– 15° C/h, and exposure to annealing should be at least 5–7 hours. Scientific novelty. The modes of heat treatment of rolling rolls with a high-chromium cast iron working layer are designed by estimating the level of thermal stresses. The profile of distribution of chromium after various modes of heat treatment is calculated analytically and its mode at which the most uniform distribution of chromium on section of a working layer remains is offered. Practical significance. The developed technique allows to calculate analytically the profile of distribution of chromium after various modes of heat treatment and to choose such a mode at which the most uniform distribution of chromium remains on the section of a working layer.

THE PRINCIPLE OF CONSTRUCTING A MICROSYSTEM INDICATOR OF THE STATE OF THE BRAKE PAD OF A ROBOTIC CAR

Проблема и цель. С развитием и широким применением колесной наземной транспортной техники выдвигаются повышенные требования к устройству машин, их управляемости с одновременным упрощением требований к водителю по управлению машиной и обеспечению ее функционирования в широком диапазоне технических возможностей. Целью исследований явилось теоретическое обоснование и практическая реализация способа непрерывного мониторинга состояния накладок тормозных колодок автомобиля КамАЗ. Методология. Разработано микросистемное устройство для контроля состояния тормозной колодки, отвечающее требованиям автоматизации и роботизации. Электрическая схема устройства построена по аналоговой форме с непрерывной регистрацией неэлектрического сигнала о состоянии (толщине износа) накладки в преобразованной электрической форме. Принцип действия сигнализатора состояния тормозной колодки автомобиля построен на использовании явления изменения электрической емкости конденсатора с изолирующей прокладкой между электродами при изменении толщины этого изолятора. Если встроить в керамическую (изолирующую) накладку тормозной колодки металлический электрод, то он образует электрическую емкость с поверхностью тормозимого металлического тела. Это позволяет в качестве изолирующей прокладки использовать изнашивающийся слой фрикционной накладки тормозной колодки. В таком датчике первичным источником информации будет являться непосредственно контролируемый параметр – остаточный рабочий слой фрикционной накладки тормозной колодки Результаты. Разработано индикаторное устройство, позволяющее водителю, находящемуся в кабине автомобиля, не отрываясь от управления осуществлять непрерывный мониторинг состояния тормозных накладок (толщины рабочего слоя) вплоть до критического, при котором дальнейшая эксплуатация транспортного средства становится небезопасной. Заключение. Применение разработанного индикаторного устройства для визуального функционального контроля водителем состояния тормозных колодок автомобиля делает возможным предотвращение нештатных ситуаций, которые могут возникнуть из-за невозможности эффективного использования рабочей тормозной системы автомобиля по причине предельно допустимого или неравномерного износа фрикционных накладок тормозных колодок. Problem and purpose. With the development and widespread use of wheeled ground transport equipment, increased requirements are put forward for the device of machines, their controllability, while simplifying the requirements for the driver to control the machine and ensure its functioning in a wide range of technical capabilities. The aim of the research was the theoretical substantiation and practical implementation of the method for continuous monitoring of the state of the brake pads of the KamAZ car. Methodology. Microsystem device for monitoring the condition of the brake pad, which meets the requirements of automation and robotization. The electrical circuit of the device is built in an analog form with continuous registration of a non-electrical signal about the state (wear thickness) of the pad in a converted electrical form. The principle of operation of the signaling device of the state of the brake shoe of a car is based on the use of the phenomenon of change in the electrical capacitance of a capacitor C with an insulating gasket between the electrodes when the thickness of this insulator changes. If a metal electrode is embedded in the ceramic (insulating) lining of the brake shoe, then it forms an electric capacitance C with the surface of the braking metal body. This allows the wear layer of the brake pad friction lining to be used as an insulating pad. In such a sensor, the primary source of information will be the directly monitored parameter - the residual working layer of the friction lining of the brake shoe Results. Development of an indicator device that allows the driver, who is in the cab of the car, without interrupting control, to continuously monitor the state of the brake linings (thickness of the working layer) up to the critical state, at which the further operation of the vehicle becomes unsafe. Conclusion. The development of an indicator device for visual functional control by the driver of the state of the brake pads of a car makes it possible to prevent abnormal situations that may arise due to the impossibility of effective use of the working brake system of the car, due to the maximum permissible or uneven wear of the friction linings of brake pads.

STRUCTURAL INVESTIGATION OF A HIGH-CHROMIUM MATERIAL USED AS AN EXTERNAL, WORKING LAYER OF A BIMETALLIC MILL ROLLER

The bimetallic mill roller has been produced by the method of vertical axis centrifugal casting. The processes, accompanying the formation of the structure of the external (working) layer from high chromium material of the bimetallic roller have been investigated. A mathematical model for the geometry of the working layer was created. By using the MAGMA Soft software package, simulations of the processes of casting and crystallization have been made. A metallographic assessment of the microstructure has been made.

Application of the shotcreting method to restore the working layer of the lining of steel-pouring ladles of the oxygen-converter shop of PJSC MMK

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Effect of chemical composition on the performance of centrifugally cast indefinite chilled cast iron rolls

Problem Statement (Relevance): An urgent task of rolling mill operators includes minimizing the cost of manufactured products while ensuring the required quality. To accomplish the task, measures are being taken to optimize the rolling process aimed at increasing the duration of the rolling campaigns and reducing the number of roll regrinds. The performance of the rolls is influenced by the properties of the working layer material which determine wear resistance, formation and development of fire cracks, as well as resistance to metal sticking. Finishing mill rolls dictate the surface quality of the rolled steel. That is why it is important to make timely regrinds in order to completely remove the fire crack layer. The removal depth and the acceptable duration of the campaigns depend on the properties of the roll working layer material. To improve the properties of the rolls, the roll manufacturers need the actual roll operation data to be able to analyze how the chemical composition and the structure of the roll working layer is related to the roll performance. Such analysis will help improve the structure and properties of the materials used, as well as develop new ones. Objectives: The objective of this research is to understand how the chemical composition of the working layer of indefinite chilled cast iron rolls used in finishing mills dictates the roll performance, to evaluate the effect of each chemical element, and to determine what concentrations of the chemical elements could most effectively benefit the performance of indefinite chilled cast iron rolls. Methods Applied: The methods applied include building a database of the finishing mill indefinite chilled cast iron rolls and using artificial neural networks based on a dual-function algorithm. Originality: The authors built a neuromodel which can help understand the effect of the chemical composition of the roll working layer and predict the performance of indefinite chilled cast iron rolls. The authors studied the effect of carbon, silicon, manganese, chromium, nickel, molybdenum, vanadium, niobium and boron on the performance of indefinite chilled cast iron rolls. Findings: Graphic diagrams were built which demonstrate the effect of each chemical element on the performance of indefinite chilled cast iron rolls at constant concentrations of the remaining elements. The authors looked at the relationship between the chemical elements and the roll performance in terms of the impact of the former on the structure of indefinite chilled cast iron rolls. The effective concentrations of the chemical elements were also determined. Practical Relevance: The authors developed a new chemical composition of indefinite chilled cast iron to be used for the working layer of finishing mill rolls. As a result, a 12–14% increase in the roll performance was achieved.