Laboratory methods for the study of rod mixtures at high temperatures

The article presents an analysis of laboratory methods for studying temperature and phase expansions and changes in the properties of molding and core mixtures during heating. The analysis of laboratory equipment offered on the Belarusian market for high‑temperature testing of molding materials and mixtures is carried out, the methodology for conducting such tests using devices from leading world manufacturers is described. The results of high‑temperature test tests of mixtures based on furan binders are presented.

Fullerenes and prospects of their use in foundry and metallurgical production

The article is devoted to a special nanostructured form of carbon – fullerenes; the discovery of which became one of the most important events in the field of physics in the 80s of the last century. The article discusses the issues of obtaining and using fullerenes and other nanostructured materials; including hybrid ones; in foundry and metallurgical production: for modifying casting alloys; binders and auxiliary molding materials; for obtaining ceramic and hybrid nanocomposites; and for other purposes. It also provides information on the creation and operation of the world’s leading research centers specializing in the synthesis and application of nanomaterials in metallurgy and foundry.

On the Relation between the Gas-Permeability and the Pore Characteristics of Furan Sand

Furan sand is one of the most commonly used chemically bonded molding materials in foundries across the world. It consists of a furfuryl alcohol-based resin and an acid-based liquid catalyst. When the molding material comes in contact with the molten metal, it undergoes a thermal shock accompanied by a certain release of volatile gases. In order to evacuate these gases, molds and cores should have optimal gas permeability values and proper venting by design. If the volatile compounds are not appropriately evacuated, they are prone to enter the melt before the first layer of solidified metal is formed which can lead to the formation of gas-related casting defects. Standard gas permeability measurements are commercially available tools used in the industry to compare and to quality control different sands, however, they only provide reference numbers without actual units. Permeability in a standard unit, m2, provides uniformity and helps the comparison of results from difference sources. In this paper, a new method using Darcy’s law (prevalent in earth sciences), was adapted to measure the gas-permeability of furan samples made of silica sand with various grain size distributions. The effect of grain size distribution on the gas-permeability of furan sand samples was studied. Gas-permeability values in m2 were then correlated with mercury-porosity measurement results to bring new light on the relation between pore size, pore volume and the permeability of molding materials.

RESEARCH OF THE RATE OF COOLING AND SELECTION OF THE MATERIAL FORM FOR THE MECHANICAL CHARACTERISTICS OF CAST IRON CASTINGS

The structure and properties of cast iron castings depends not only on the chemical composition of molten cast iron and the technology of its smelting, but also on many other conditions such as cooling and crystallization of castings, especially on further solidification of castings in casting molds. The article presents the established dependences of the influence of the cooling rate of castings on the mechanical properties of the obtained parts, the investigated microstructures of experimental samples from the selected molding materials and it is established that the thermal conductivity of materials affects the structure of graphite in cast iron castings. Computer models of dependencies and regression equations of the processes are proposed.

Use of silicones in fixed aesthetic rehabilitations: clinical case

Molding in a fixed prosthesis is one of the most important stages in rehabilitative treatment, as it is there that attempts are made to reproduce dental preparations and adjoining regions by using appropriate materials and techniques. Among the fixed prosthesis molding materials available on the market, the elastomers stand out, which are polymers where the prey occurs through the increase of the chain and the establishment of cross-links. The objective of the study is to present a clinical case and perform a literature review on the use of condensation silicone and addition to molds in Fixed Prosthesis. In this literature review, a survey of PubMed, Scielo and Lilacs data was performed, using the descriptors: Denture, Partial, Fixed; Dental Impression Materials and Elastomers. It is possible to conclude that in the field of Dentistry, the elastomers, among them the condensation-cured and addition-cured silicones, both provide high precision models and are the most used materials in works with fixed partial dentures. Therefore, it is up to the professional to know the properties and adapt to the best group of chosen materials.

Characterization of sand and sand–binder systems from the foundry industry with electrical impedance spectroscopy

The global economy consumes an estimated 4×1010 t of sand per year, with only 2×1010 t of sand being reproduced by natural sedimentation (Götze and Göbbels, 2017; Peduzzi, 2014). Among other things, sand is also used as a basic material for the production of molds and cores in the foundry industry. The consumption and the economic as well as ecological savings' potential in this area of application can be appreciated by way of an example: the environmental certificate of a single, albeit big German foundry (5160 employees) can be consulted, which states that 39 820 t of sand for casting molds had to be purchased in 2017 (Denes, 2018). In order to avoid having to dispose of the used sand in landfills and to reduce the use of new sand, it is therefore advantageous to renew the used sand in a so-called regeneration process and reuse it as a substitute for new sand in the production of molds and cores. It would be very advantageous if the condition of molding materials (sand–binder systems) in regenerator units could be monitored in real time because of the economic and ecological advantages of a monitored and optimized regeneration process. This work presents the results of investigations in this direction. The objects of investigation in this work are typical molding materials in the foundry industry, e.g., quartz sand, chromite sand, and bentonite as a binder, which are measured impedimetrically with the help of a plate capacitor measuring cell which is connected to an LCR meter (Agilent E4980A). The impedance of the filled capacitor is measured in a frequency range from 1.2 kHz to 1 MHz, containing 123 frequency points. The aim of this research is to work out if the mentioned substances can be measured with the presented measuring method and classified on the basis of impedance characteristics and thus whether impedance spectroscopy can be considered for process monitoring in the molding industry. It is shown that the condition monitoring can possibly be based on impedance spectroscopy because the resulting curves are characteristic of the material used. New and used sands as well as two-component mixtures of sands and binders showed a systematic behavior, which allows the sand or the composition of the mixture to be identified (classified) in the future. The examination of the scatter of the measurement results shows that the impedance data obtained with this method can be measured reproducibly. A descriptive model for multi-component systems is developed in order to be able to interpret the impedance scatter results and their representation in Nyquist plots. From this model, the filling density of the measurement cell and the density of conduction paths can be extracted as essential influence quantities.

Analytical method of calculation of thermal fields of cast parts during crystallization

The aim of the work is to create a mathematical method that allows to calculate the distribution of thermal fields in cast parts during crystallization using a system of analytical formulas. During the calculations, a combination of known analytical formulas GF was used. Balandin, AY Weinik, S. Schwartz with their own original mathematical solutions created on the basis of the analysis of thermophysical processes in castings in the process of their crystallization. Computer simulation of thermal fields using the LVMFlow program was used to compare the results. According to the created mathematical method, examples of calculation of thermal fields for two castings made of steel 25L of hollow cylindrical shape, the wall thickness of which is 100 mm and 4 mm, respectively, are given. Calculations were performed for the conditions of crystallization of castings in a single sand form. The comparison of results of calculations by the developed method and with use of the existing software is presented. For the first time, based on our own mathematical and thermophysical developments, a comprehensive calculation method for determining the thermal field of the casting during crystallization and cooling was developed. casting. The technique is expressed in a number of analytical formulas, each of which describes a specific thermal process that occurs in the casting. This takes into account the features of the casting configuration. The created complex method of calculation of thermal fields of cast parts is a mathematical basis for determining the thermal fields of molds and rods, which allows to predict their properties and select the optimal molding materials. The created technique can also be offered as a mathematical basis for refining applied computer programs for foundry production. CASTING, TEMPERATURE, THERMAL FIELD, COOLING DYNAMICS, COOLING DURATION, MATHEMATICAL LAW, COLORING FRONT, CALCULATION

TECHNICAL AND TECHNOLOGICAL STUDY OF CERAMICS OF THE FIRST HALF OF THE 20TH CENTURY FROM THE TERRITORY OF THE TABUNSKY DISTRICT OF THE ALTAI REGION

The article is devoted to the publication ofmaterials of a technical and technological analysis of ceramics discovered on four nowadays non-existent settlements, founded during the Stolypin reforms, on the territory of the modern Tabunsky district of the Altai region. As a result of the study, it was found that ceramic products from clays of medium and strong ferrous content, of various plasticity prevailed there. Three recipes for molding materials have been founded. Most of the products were fired at high temperatures with oxygen access. Most of the crockery were not subjected to additional surface treatment; glazed items are also found, one vessel was ornamented. The data obtained agree with the available written and ethnographic sources. Further work on the technical and technological analysis of “Russian” ceramics, as well as conducting archaeological and ethnographic research, can provide more complete information about the level of development of pottery production in Altai, as well as reveal the specifics and local features of different districts. Keywords: pottery, ceramics, first half of the 20th century, altai, technical and technological analysis

Ceramic Production of the Kulai Culture in the Novosibirsk Ob Region: Based on Materials from the Kamenny Mys Burial Ground

Purpose. The Kulay Cultural-Historical Community was one of the largest formations in Western Siberia in the early Iron Age. The Kamenny Mys burial ground is located in the Kolyvan district of the Novosibirsk region. The study is devoted to the technical and technological analysis of 49 vessels of Kulay ceramics (Novosibirsk variant) of the Kamenny Mys burial ground. Results. It was determined that natural clays of medium plasticity, possibly pretreated, were used as the initial plastic raw material. The dominant recipe for the clay paste is clay + broken stone (68 %). The construction was carried out according to the tank-bottom program with the help of flaps. The hollow body was constructed using patchwork molding. Mainly mechanical smoothing processed the surfaces of the vessels. The firing of dishes could be carried out in fireplaces or hearths. Conclusion. Ceramic technology reflects the initial mixing of different pottery skills. Stability is retained by the substrate skills of the selection of the initial plastic raw material, the design of the beginning and the hollow body. Mixing is manifested at the level of adaptive skills – methods of composing molding materials and machining surfaces. Such a situation may be a consequence of the interaction of groups of the Kulay population with the carriers of the Bolsherechenskaya culture and the beginning of their mixing, which led to the fusion of technological pottery skills.