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The requirements for the quality and performance of the brake pads of railway rolling stock made of various materials are analyzed. The advantages of cast iron brake pads produced at foundries are shown. The disadvantages of brake pads made of composite materials based on rubber, asbestos, barite, carbon black and other components are noted. Ways to improve standards, specifications and other documentation for these products are proposed.
The results of the analysis of various methods of refining aluminum alloys from dissolved gases and non-metallic inclusions are presented. The influence of a number of technological features of each method on the quality of the melt has been studied. Examples of equipment for the implementation of processes are presented. To analyze the effectiveness of the use of various technologies for refining aluminum alloys, their ranking was carried out. The results of the analysis are in correlation with the trends in the spread of various processes for the refining of aluminum alloys in foundries. It is shown that blowing the melt with inert gases through a rotating impeller is the most effective in terms of a set of indicators in comparison with other methods.
In the production of mineral raw materials in cupolas, as a by-product and harmful product, a significant amount of cast iron (up to 3 % of the raw material) is formed and, as a rule, thrown into the dumps. The article presents technical solutions that ensure the separation of mineral melt and cast iron. In addition, the article describes the results of optimizing the design of ladders used for draining liquid metal from the mineral wool cupola and transporting it. The resulting cast iron ingots can then be used as a charge in the smelting of branded cast alloys.
The publication describes modern methods of production of fine plastic art castings. The stage of production of the smelted model and development of casting technology is considered. The theoretical basis for obtaining smelted models of a given quality is given. The review of technologies of production of standard castings is presented.
The technique of physical modeling of macro processes of solidification of castings on transparent models and liquids has been developed. The model liquids may be water with different salt contents. Glass bottles can be used for transparent models. Thermal insulation of the top of the model is required. The developed technique allows to investigate the effect of dissolved gases on the microstructure of castings. It has been shown that gases dissolved in liquids have a direct effect on the solidification process and its kinetics. It has been shown that hot water containing less dissolved air than cold water solidifies in the freezer faster than cold water.
The experience of the Physico-technical Institute (PhTI) of the National Acdemy of Sciences of Belarus in the harmonization of international standard ISO 17804 (Founding – Ausferritic spheroidal graphite cast irons – Classification) and development of the Belorussian analogue STB ISO is described. The reasons for the choice of austempered ductile iron (ADI) as an object for standard harmonization are presented: it is the most promising cast iron in comparison with gray and classical ductile iron. The work procedure on harmonization is described: how to include the task into the State Plan on standardization, specificity of translation of the text, peculiarities of with state organizations responsible for approbation of standards such as Belorussian Institute for Standardization and Certification (BelGISS) and State Committee on Standards (Gosstandart), writing a summary of external reviews, working with critical comments from potential users. It is outlined that any foreign standard does not exists independently but is closely connected with at least 10 to 20 other standards. Thus, harmonization necessitates coordination with other standards and sometimes even with handbooks by adding annexes to the main text. The importance of a proper choice of the standard status is outlined: identical (ID) or modified (MOD). Developing an identical standard is prestigious but difficult because is requires harmonization of all the referenced standards, which is a very labor-consuming procedure. It is argued that the most suitable is ‘intermediate’ variant: adopting the authentic text of the international standard (in high-quality translation) but with annexes reflecting national specificity in this area. As a result, a harmonized standard is developed which, for the first time in Belarus, standardize the tensile strength of 800 MPa in combination with the elongation of 10 % and the tensile strength of 1400 MPa in combination with the elongation of 1 % for cast irons.
The annual demand for ADI in Belarus is estimated as about 10,000 ton. It is shown that in Belarus, where about 60 industrial enterprises have a foundry and almost every engineering plant has a heat-treatment shop, austempered ductile cast (ADI), which features a high strength, can successfully compete with rolled steel in certain applications.
Metallurgy
One of the most effective micro-alloying elements in the production of class 500 fittings is vanadium. However, the production technology is multi-stage and expensive, so the use of ferrovanadium makes the production of vanadium-containing fittings for mass use unprofitable. In this regard, it is necessary to reduce the cost of finished products by replacing ferrovanadium with ferroniobium while preserving all the mechanical, physical and operational characteristics of the metal.
Objective: to determine the effect of the quantitative content of niobium in steel in the production of hot-rolled rebar S-500WC in coils at the mill 370/150 of OJSC “BSW – Management Company of the Holding “BMK” in accordance with the requirements of the Israeli standard SI 4466-3:2013 at various temperature and speed parameters of rolled products. The normalized mechanical properties of s-500WC reinforcing steel of all profiles (No. 8–16) in accordance with THE requirements of si 4466-3:2013 are: yield strength – 500–650 MPa, ductility – 1.15–1.35, elongation of – at least 11 % and total elongation at break of – at least 7.5 %.
Fasteners are widely used as machine parts, structures and mechanisms. Medium-carbon alloy steels and boron-containing alloy steels are used as materials in production. Boron-containing steels have a good combination of strength and plastic properties, as well as a high level of hardenability. This article describes the research work carried out in the laboratory, and considers the reasons for obtaining low values of physical and mechanical parameters of parts manufactured at competitive enterprises. The qualitative characteristics of the metal are determined. The results of chemical, physical-mechanical and metallographic tests, as well as the results of the chemical composition of non-metallic inclusions are presented. The reasons for the discrepancy of mechanical properties in boron-containing steels are considered. The dependence of the introduction of chemical elements into steel: nitrogen, titanium, aluminum is determined. The possibility of evaluating the content of “effective boron” at OJSC “BSW” – the Management Company of the Holding “BMC” is described. The mathematical model used at OJSC “Oskol electrometallurgical combine”, which allows to carry out a theoretical calculation of the value of “effective” boron, is described. Recommendations for improving the technological process of smelting boron-containing steels are given.
A method for measuring the mass fraction of phosphorus in steels by atomic emission spectrometry with the inductively coupled plasma (AES-ICP) has been developed. Possibilities of atomic emission spectrometers of iCAP series for determination of phosphorus in steels allowing to reduce considerably duration of the analysis and to increase its profitability in comparison with chemical methods of the analysis are investigated. A method of decomposition of steel for the complete transfer of phosphorus into solution is proposed. The possibility of software spectrometers “iTeva” in the analysis by the method of relative concentrations. Calibration of the spectrometer was carried out on aqueous solutions with a known concentration of phosphorus using the method of relative concentrations. For the preparation of calibration solutions, chemically pure salt was used. The analytical line free from spectral overlays is selected. A good correlation of the calibration graph is obtained. The correctness of the determination is confirmed by the analysis of standard samples and comparison with the results of the determination in accordance with the chemical method. The developed technique is used in determining the mass fraction of phosphorus in steels. Validation of the methodology was carried out. iCAP spectrometers can be used to determine the mass fraction of phosphorus in steels.
OJSC “BSW–Management Company of the Holding “BMC”, non-contact systems for measuring the outer diameters of products are widely used for measuring geometric dimensions. Diameter measurement systems are used to obtain reliable, true and accurate measurements. The method that provides continuous and non – contact control of these systems is the light -and – dark method of measuring the diameter.
To ensure the reliability of the measurement results, the diameter measurement systems must undergo metrological control – calibration. Calibration is carried out according to the developed methodology, which specifies the order of work, requirements for standards, processing of measurement and evaluation results, and registration of calibration results. To assess the extended uncertainty, a mathematical model is created that takes into account all the corrections that affect the result of the assessment, each of which is subjected to a thorough analysis.
Calibration of diameter measurement systems allows to evaluate their real deviations in operating conditions, which allows to ensure the accuracy and reliability of measuring the geometric dimensions of metal products at all stages of its production.
One of the ways to increase the strength and reliability of building structures is the use of steel – fibre reinforced concrete. Steel – fibre reinforced concrete has significant advantages over conventional concrete. A high degree of resistance to cracking contributes to an increase in such physical and mechanical parameters as compressive, tensile and bending strength, water resistance, frost resistance, resistance to water and chemical penetration. In steel – fibre reinforced concrete, steel – fibre is used as a reinforcing material, evenly distributed over the volume of concrete.
In the process of steel – fibre production, the fiber is cut with carbide knives. The article deals with the issues of increasing the wear resistance of carbide knives used for cutting steel – fibre, and suggests ways to increase the durability of cutting tools. The influence of the quality of tungsten-cobalt hard alloy on the wear resistance of knives is analyzed, and a knife attachment device is developed.
The article describes experiments on the reconstruction of the technology of the one-step process of obtaining iron-carbon alloys in furnaces based on archaeological sources. It contains the description of furnace design, metallurgical process technology and raw materials preparation. The process of refining the iron bloom by forging is described. Scientifically grounded assumptions are made about possible technological methods of obtaining steels in the pre-industrial period on the territory of modern Belarus.
The article deals with the issues of processing of dust from electric steelmaking production by the method of thermodynamic extraction of iron, zinc and lead in order to reduce the environmental impact and increase the resource base of the industry. The paper presents various methods of zinc extraction from dust and gas purification, thermodynamic calculation of the decomposition and reclaiming of zinc ferrite.
Science of materials
The effect of laser radiation on a solid body leads to a change in the temperature field of the processed substance. The nature of heating, which is determined by the rate of change in temperature and temperature gradients, is different depending on the properties of the processed material and processing conditions.
The main physical parameters of the process of laser processing of solids are the specific power of the absorbed laser stream 104–109 W/cm2 and the interaction time of the metal with the beam – 10–5–10–8 s. When such radiation pulses interact with the surface, an instantaneous explosive melting of a part of the material occurs and the substance surrounding the surface is transferred to the plasma state. The subsequent expansion of the plasma is accompanied by the appearance of a shock wave with a peak pressure of 1–10 GPa, which acts on the material, and the metal is dispersed.
The mathematical problem of heating and melting a cylindrical plate with a laser light flux that normally affects its surface is solved. this problem is described by a system of thermal conductivity equations in three sections of the heated plate, which are characterized by the time factor of the laser radiation effect on the substance 1) 0 ≤ t ≤ tm; 2) t > tm; 3) tm < t ≤ th (here tm, th is the time moment corresponding to the beginning of the formation of the liquid phase and the end of the melting of the plate, respectively).
The calculated dependences of changes in the surface temperature of metal alloys X18N10T, X15N60 during the action of a laser radiation pulse with a duration of τ=5 ms are presented. The presence of a phase transition associated with metal melting (an inflection in the curves) leads to a temporary decrease in the rate of temperature growth. The distribution of temperature fields causes a significant heterogeneity in the distribution of temperature over the thickness of materials, which reaches 2000 °C or more depending on the thickness of the metal and the conditions of exposure. The temperature curves of the surface heating repeat the shape of the pulse, and the temperature of the rest of the metal has a nonlinear tendency to increase with the output to the asymptote.
It is established that the process of explosive metal sputtering requires heating the volume of the material above the melting point at a thickness of 300–350 microns and an impact energy of 7–8 J. Reducing the level of energy impact to 5–6 J and increasing the thickness of the workpiece more than 500 microns does not provide the distribution of temperature fields required for the implementation of the spraying process.
The aim of the paper is investigation of neutralization of solvent vapors of the brand 646 by an adsorption-catalytic method. The adsorption-catalytic method includes the following stages: adsorption of the solvent components by adsorbent, thermal desorption and periodic flameless catalytic oxidation of organic substances to carbon dioxide and water. Synthetic zeolite of the NaX brand was used as a sorbent, catalyst was porous Al2O3/SiO2 ceramic foam material with an active catalytic phase. Solvent contains aceton, toluene, butylacetate, ethanol, ethyl cellosolve, n-butanol. It is shown that the value of the sorption volume of zeolite for each class of compounds depends on the certain factors: the length and structure of the carbon skeleton, the position of the hydroxyl group (for alcohols and esters), number of methyl groups in the molecules (for benzene derivatives). The conversion of the mixed solvent components was 65.4–90.1 %.
This article is a continuation of the series devoted to the creation and application of nanomaterials and nanotechnologies in modern industry in general and in metallurgy, materials science and foundry production in particular. The article deals with the choice of equipment and the development of effective methods for obtaining nanomaterials. Examples of the application of the developed equipment, technologies and materials obtained in the Republic of Belarus and abroad are given.
At the Navoi Mining and Metallurgical Combine, which uses a large number of machine parts for mining operations, the issue of optimizing the compositions of wear-resistant chromium cast irons while maintaining their operational characteristics has arisen. The paper presents the results of studying the phase composition of the cast alloy, as well as the effect of heat treatment of cast iron with a high chromium content on its structure and properties. As heat treatment operations, quenching in various modes and low tempering were used. The study made it possible to systematize the known literature data on the heat treatment parameters of a group of wear-resistant chromium cast irons, as well as to optimize their heat treatment modes for parts operating in mining and processing industry.
Protection of labour
The results of the study of working conditions in aluminum casting shops worksites are presented. The results of these studies showed that in worksites there are exceedance of the permissible limits for noise, vibration, the content of harmful substances in the working environment, intensity of infrared (thermal) radiation and air temperature. There is effect of electromagnetic radiation on the workers during the service of induction furnaces. In addition, the main harmful production factors include the severity of work and the intensity of the labor process. The efficiency of the protective screens of the IAT-6 induction crucible furnace was evaluated.
Information
The main results of the tasks of the subprogram “Metallurgy” obtained by the organizations of the National Academy of Sciences of Belarus, the Ministry of Education and the Ministry of Industry of the Republic of Belarus are presented. Their contribution to the solution of scientific and practical problems in the field of metallurgy is shown.
The article presents promising developments proposed for implementation in 2021–2025, aimed at optimizing existing foundries, improving the quality of products, reducing of production costs, and ensuring maximum utilization of foundry capacities.
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ISSN 2414-0406 (Online)