Optimization design and operating parameters of induction heat-ing system for hardening

The paper deals with the problem of optimizing the design and operating parameters of an induction heating system for surface hardening of a steel stepped shaft. The problem of optimal design of an inductor is formulated based on a nonlinear two-dimensional numerical model of coupled electromagnetic and temperature fields, developed in the ANSYS Mechanical APDL software. Alternance method of parametric optimization of systems with distributed parameters is used to optimize induction hardening system. MATLAB software has been used for developing parametric optimization subroutine, which was incorporated into the numerical ANSYS model to simulate a process of induction heating. Commonly used a multi-turn solenoid-style coil fabricated from rectangular copper tubing has been used as a hardening inductor. Besides that, an application of profiled copper turns has been investigated. Optimization of induction hardening system described above allows one to substantially improve heating uniformity and enhance metallurgical characteristics of as-hardened stepped shaft. Localized temperature surplus at an upper diameter shoulder has been minimized. At the same time, sufficient austenitization in the fillet area near stepped region (diameter transition) has been obtained.

FEATURES OF THE FORMATION OF THE STRUCTURE OF A CEMENTLESS MATRIX COMPOSITE BASED ON MECHANICALLY ACTIVATED TECHNOGENIC RAW MATERIALS

The creation of composite materials using mechanically activated technogenic raw materials is relevant today as part of a large-scale task of construction and technological utilization of technogenic formations. The change in the crystal structure using mechanochemistry increases the activity of technogenic products: the number of coagulation contacts of dissimilar particles increases, increases the plastic strength of the hardening mixture, formation of hydration products is accelerated. The article is devoted to the study of the mechanism of structural and rheological transformations of a cementless hardening system based on activated steelmaking. Steel melting slags were used as raw materials - energy-saturated large-capacity waste of the West-Siberian Metallurgical Combine (Novokuznetsk). As components - activators - waste from the coal industry of the «Abashevskaya» mine (Novokuznetsk) - burnt rocks with heaps and slimes, obtained by neutralization of spent acid battery electrolytes with lime batteries for industrial vehicles. Based on used mechanically activated technogenic raw materials the binder composite material of the matrix structure is obtained. To assess structural and material changes in the hardening system comprehensive physical and chemical studies were carried out: IR - spectroscopy, thermogravimetric and x-ray phase analysis. Electron microscopy investigated the structure of the stone. It was found that the matrix structure of the composite material is a dispersion medium - matrix of dense fine-grained masses calcium sulfate hydrate; dispersed phase from lamellar crystals of quartz and magnesium oxide, and tubular crystals of calcium orthosilicate; and transitional interfacial layer from structured grains of calcium hydrosulfoaluminate. In the process of forming the structure interdependence of phases from each other was accompanied by a sequential transition of some types of structures to others: coagulation→ crystallization- condensation→ crystallization. The article presents the results of the self-organization of the structure, the interaction of oxide systems in the process of hydration is considered, major mineral neoplasms are established, possessing astringent properties and providing strong bonds between structure-forming components.

FEATURES OF THE SELECTION OF THE RATIONAL STRUCTURE OF THE COMPOSITIONAL GIPS BINDER

the dynamically developing construction in the Russian Federation makes it necessary to expand the range of alternative types of binders and materials based on them. Such a binder is a previously developed composite gypsum binder (CGB), used for the production of materials of various functional purposes. The manufacture and use of CGB-based composites was made possible by studying the Portland cement-gypsum-water system, the stability of which is ensured by introducing an appropriate amount of active mineral additives that reduce the concentration of Ca(OH) 2 in the liquid phase of the hardening system and create the possibility of hardening under certain conditions without dangerous internal stresses. In this paper, we consider the possibility of using composite gypsum binder for fine-milled quartzitic sandstone crushing dropout and concrete scrap crushing dropout as an active mineral additive. Rational compositions of composite gypsum binder are developed and their basic properties are studied. The reasonable choice of the amount of active mineral additive allows optimizing the properties of the composite gypsum binder.

Modified Composition for Fixing Sandy Soils

The possibility of using a modified composition based on slag Portland cement with the addition of stabilized finely dispersed slag in geotechnical construction and in landscape design is considered. The physical, mechanical and structural characteristics of samples hardening in normal conditions and under the influence of aggressive media were studied. It is established that the compressive and flexural strength of the modified samples is higher than that of the control sample. When hardening in normal conditions, on the first day, the flexural strength of modified specimens increased by 59%, at the grade age by 51%, compressive strength - 2.3 times and by 83%, respectively. When hardening in aggressive media, an increase in the strength of the modified specimens is also observed (flexural by 35–58%, compressive by 7–15%). This is explained by the fact that stabilized slag particles in a hardening system perform two functions: they are centers of directional crystallization for nucleation and growth of newgrowths, and full participants in the hydration process, binding calcium hydroxide to crystallohydrate compounds, thereby preventing the formation of ettringite when the concrete structure is exposed to aggressive media.

Влияние критических параметров технологии на свойства композитов на основе портландитовой матрицы

Представлены результаты экспериментальных исследований критических параметров технологии на свойства контактно-конденсационных бесклинкерных систем твердения на основе портландитовой матрицы и алюмосиликатного наполнителя. В исследованиях в качестве алюмосиликатного наполнителя использовался трепел. Выявлены основные факторы, влияющие на свойства изделий, полученных по технологии контактно-конденсационного твердения. К ним относятся прежде всего характеристики наполнителя (минералогический состав, тонкость помола) и параметры технологии (соотношение матрицы и наполнителя, величина прессового давления). С помощью рентгенофазового анализа установлено, что минералогический состав выбранного алюмосиликатного компонента (трепела) позволяет получать композиты по контактно-конденсационной технологии. Получены количественные данные о влиянии соотношения матрицы и наполнителя и величины прессового давления на прочность композита разных сроков твердения. Структура этого композита состоит из кристаллических сростков в основном матричной субстанции с присутствием низкоосновных гидросиликатов и гидроалюминатов кальция. Установлено, что оптимальный расход наполнителя составляет 15–30% от массы матрицы, давление прессования – 80 МПа. Ключевые слова: портландитовая матрица, алюмосиликатный компонент, контактно-конденсационная технология, бесклинкерная система твердения, диаграмма Исикавы, прессовое давление. The results of experimental studies of critical parameters of the technology on the properties of contact-condensation linker-free hardening systems based on portlandite matrix and aluminosilicate filler are presented. The flutter was used as an alumosilicate filler in studies. The main factors affecting on properties of the products obtained with the contact-condensation hardening technology have been revealed. These include, first of all, the characteristics of the filler (mineralogical composition, fineness of grinding) and the technology parameters (matrix to filler ratio, press pressure). Using X-ray phase analysis, it was found that the mineralogical composition of the selected aluminosilicate component (trepel) allows to obtain the composites using contact-condensation technology. The quantitative data on effect of matrix-filler ratio and press pressure value on strength of obtained composite in different hardening periods are obtained. The structure of this composite consists of crystalline splices in the main matrix substance the portlandite with the presence of lowbase hydrosilicates and calcium hydroaluminates. It has been established that the optimal flow rate of the filler is 15–30% of the mass of the matrix, the pressing pressure is 80 MPa. Keywords: portlandite matrix, aluminosilicate component, contact-condensation technology, linkless hardening system, Ishikawa diagram, press pressure

Design of an Integrated Anti-Hardening System for Carbon-In-Leach Tanks

Slurry density monitoring is of paramount importance in the industrial world. Most industries, especially cement and mineral processing industries, employ this method to obtain good quality products. However, most Carbon-In-Leach (CIL) tanks of gold processing industries do not use slurry density monitoring systems. As a result, many a time, agitation difficulties occur when the slurry begins to harden. This paper, therefore, seeks to design an integrated anti-hardening system for CIL tanks, with the aid of a microcontroller, to monitor the density of the slurry in order to prevent it from hardening. Slurry density measurement was achieved with the help of a strain gauge pressure sensor and a couple of level sensors. Atmega 328p microcontroller board was programmed to continuously compute the density of the slurry from values of pressure and level of slurry in the tank indicated by the pressure and level sensors, respectively. The microcontroller responds to slurry hardening by activating a light emitting diode and triggering the piezo buzzer when a set point is reached. The designed circuit was successfully simulated using Proteus 8.2 design suite software to ascertain its functionality. Based on the results obtained, the light emitting diode and piezo buzzer activated when the set point was reached. It was concluded that the anti-hardening system is effective for constantly monitoring the density of the slurry to prevent it from hardening. It was also recommended that the mining industries could employ the designed system to monitor the density in order to prevent hardening of slurry in CIL tanks. Keywords: Carbon-In-Leach Tanks, Slurry Densisty, Strain Guage Pressure Sensor, Microcontroller

A parallel multi-fidelity optimization approach in induction hardening

Purpose Reliable modeling of induction hardening requires a multi-physical approach, which makes it time-consuming. In designing an induction hardening system, combining such model with an optimization technique allows managing a high number of design variables. However, this could lead to a tremendous overall computational cost. This paper aims to reduce the computational time of an optimal design problem by making use of multi-fidelity modeling and parallel computing. Design/methodology/approach In the multi-fidelity framework, the “high-fidelity” model couples the electromagnetic, thermal and metallurgical fields. It predicts the phase transformations during both the heating and cooling stages. The “low-fidelity” model is instead limited to the heating step. Its inaccuracy is counterbalanced by its cheapness, which makes it suitable for exploring the design space in optimization. Then, the use of co-Kriging allows merging information from different fidelity models and predicting good design candidates. Field evaluations of both models occur in parallel. Findings In the design of an induction heating system, the synergy between the “high-fidelity” and “low-fidelity” model, together with use of surrogates and parallel computing could reduce up to one order of magnitude the overall computational cost. Practical implications On one hand, multi-physical modeling of induction hardening implies a better understanding of the process, resulting in further potential process improvements. On the other hand, the optimization technique could be applied to many other computationally intensive real-life problems. Originality/value This paper highlights how parallel multi-fidelity optimization could be used in designing an induction hardening system.

EFFECTIVE CELLULAR CONCRETE ON THE COMPOSITE GYPSUM BINDER

The dynamically developing construction of the Russian Federation makes it necessary to expand the range of alternative types of binders and materials based on them. Such binders include a composite gypsum binder used for the production of materials for various functional purposes. The manufacture and use of products based on composite gypsum binders is made possible by studying the Portland cement – gypsum – water system, the stability of which is ensured by introducing of an appropriate amount of active mineral additives. Such additives reduce the concentration of Са (ОН) 2 in the liquid phase of the hardening system and create the possibility of hardening under certain conditions without dangerous internal tensions. This article discusses the obtaining of effective cellular concrete on a composite gypsum binder. Cellular concrete surpasses some traditional materials in its structure, properties, methods of preparation, and they are universal in terms of operational properties. The possibility and expediency of using thin-ground concrete scrap as a mineral additive in the composition of composite gypsum binder for cellular concrete is established in the work. Thermal insulation and structural cellular concrete of D600 and D700 grades are obtained. It is revealed that the stepwise loading of the components of the concrete mixture with the initial introduction of a gypsum binder is rational.

Improving the properties of composite materials for civil engineering

It is shown that a highly-efficient chemical activation of the cement-containing composite mixture with the help of a new generation nanostructural additive makes it possible to develop high-strength finegrained and heavy-weight concretes with the improved strength and deformation characteristics. The recommended nanostructural additive has an increased triple effect: reactive, catalytic, and plasticizing. The use of the proposed additive many times increases the hydration activity of the hardening system, exerting a double energy effect on it, chemical and thermal, thus making it possible to develop the composite building material of a new level of physical and mechanical properties.