Machines. Technologies. Materials.
Vol. 19 (2025), Issue 8

Table of Contents

  • MACHINES

    • Reducing the number of pores in the tungsten-cobalt carbide tips of the road milling cutter in order to increase its wear resistance

      pg(s) 272-276

      Studies of the tip of a road milling cutter made of tungsten-cobalt alloy have been carried out. It is established that one of the factors influencing the wear resistance of the tip is the porosity of the sintered hard alloy. Laser treatment of the surface of the cutter tip was performed. It has been found that under certain laser radiation conditions, the number of pores in the cutter decreases.

    • Air-Side Pressure Drop and Heat Transfer Analysis in Slotted Fin and Tube Heat Exchanger

      pg(s) 276-279

      Compact air-cooled fin-and-tube heat exchangers are widely used in various fields, including the automotive and computer industries, as well as in heating, air conditioning, refrigeration, and process applications. Due to the thermal characteristics of air, the majority of heat transfer resistance occurs on the air side of the heat exchanger. As a result, research in this area primarily concentrates on enhancing the air-side performance. Numerous studies in the literature explore different fin and tube configurations aimed at optimizing the design of these heat exchangers however, pressure drop is sometimes neglected. In this study, a numerical analysis was conducted to investigate air-side pressure drop and heat transfer in various configurations of slotted fin-and-tube heat exchangers whereby heat exchangers with different ellipticity ratios were considered. The numerical model of the three-dimensional, laminar, steady-state problem of air-side flow and heat exchange was done using the finite volume method. The convection-diffusion equations were discretized using the Power Law scheme, and the SIMPLE algorithm was employed to couple pressure and velocity. Simulations were carried out in ANSYS Fluent 18.2. The validation of the proposed model was tested by comparing the numerical results with experimental measurements available in the literature whereby no discrepancies greater than 5% were observed. Four different inlet air velocities ranging from 1 to 4 m/s, corresponding to Reynolds numbers between 558 and 2233 were considered. Both the inlet air temperature and the tube surface temperatures were kept constant at 293 K and 373 K, respectively. The results emphasize potential benefits of using elliptic instead of round tubes in slotted fin and tube heat exchangers to achieve lower air-side pressure drop without penalty of lower heat transfer.

  • TECHNOLOGIES

    • Evaluation of the quality of forgings depending on the technological parameters of production

      pg(s) 280-284

      The article presents the results of research aimed at assessing the quality of forgings depending on the forging parameters used. The forging and subsequent heat treatment processes revealed the occurrence of cracks in the forgings. The article examines the possible causes of cracks, which can be caused by carburizing annealing and loss of plasticity during stress relaxation. Tool wear and damage during forging also affect the formation of cracks. These factors were identified as key factors contributing to the formation of non-metallic oxide inclusions, the transfer of surface defects and the formation of lamellar propagation during subsequent heat treatment. The findings highlight the influence of tool conditions and process parameters on the quality and reliability of steel forgings..

    • Formation of defects in railway wheel rims during operation

      pg(s) 285-288

      During operation, under the influence of mechanical stress, temperature, and external environment, the initial structure of a railway wheel undergoes changes that lead to its fatigue-corrosion wear.
      The wheels with different tread profiles that were removed from operation due to the maximum wear of the rims were studied. The studies were carried out using the metallographic method (Neophot-21) and scanning electron microscope JSM-35.
      The causes of cracks and wear particles formation near the tread surface of railway wheels associated with phase and structural changes occurring during operation were analyzed. The possibilities of changing the tread profile due to uneven wear were established. It was shown that structural and phase changes near the tread surface are associated with the development of plastic shifts due to the action of external loads, thermal stresses during braking, and the formation of “white layers” when the metal is heated by the heat of braking and abrupt cooling when the brakes are turned off. The role of non-metallic inclusions and corrosion products of wheel steel in the formation of cracks near tread of railway wheels has been established.

    • Determining natural gas consumption for slabs heating in a Pusher Furnace ahead of plate steel rolling

      pg(s) 289-292

      Natural gas serves as the primary energy source for heating slabs in the Pusher Furnace prior to their rolling into steel plates. The required quantity of natural gas for a 24-hour operational period must be estimated in advance. This study employs multifactor regression analysis to develop a straightforward yet effective predictive equation for natural gas consumption, incorporating key variables such as projected production, the number of slabs to be heated, effective operating time, and the average dimensions of the slabs over a 24-hour workday. Extensive data collected over an extended period formed the matrix for determining the regression coefficients. The resulting model demonstrates a high correlation coefficient (R² = 0.99), underscoring the accuracy of the regression equation. This indicates that the model reliably predicts natural gas consumption with minimal deviation from actual usage during a 24-hour workday.

    • Obtaining molybdenum trioxide enriched with Mo–98 regenerated from spent Tc-99m generators

      pg(s) 292-295

      The paper describes a technology for obtaining Mo-98 from waste from the production of industrial Tс-99m generators, followed by regeneration, purification and obtaining molybdenum trioxide enriched with molybdenum-98 for the purpose of reuse for the production of Tс-99m generators. Regeneration of molybdenum trioxide with Mo-98 from spent Tc-99m generators was carried out by the elution method in dynamic mode: aluminum oxide from industrial spent Tc-99m generators was loaded into the column and a solution of sulfuric acid (1 mol/l) was passed through the column at a rate of 2.0-2.5 ml/min.The purification of regenerated molybdenum trioxide with Mo-98 from possible radionuclide impurities and residues of sulfuric acid anions was carried out on an ion-exchange resin – anionite quaternary phosphonium base in Cl-form. Desorption of molybdenum from the solid phase of the sorbent was carried out with a solution of ammonium nitrate (1 mol/l) containing 0.01-0.05% hydrogen peroxide and 8-10% aqueous ammonia solution with an elution rate of 1 ml/min, while molybdenum was washed out with a yield of up to 80%.Using the emission spectral analysis method, it was determined that the mass fraction of metal impurities in the regenerated molybdenum trioxide enriched with Mo-98 complies with the requirements of Technical Specifications 95 641-79 “Molybdenum trioxide enriched with molybdenum-98″. During the neutron activation analysis of regenerated molybdenum trioxide enriched with Mo-98, only gamma spectra of the parent radionuclide Mo-99 with gamma lines of 180 keV, 740 keV and 780 keV and only the gamma spectrum of the daughter radionuclide Tc-99m with the gamma line of 140 keV were obtained, which proves the absence of any radionuclide impurities in the regenerated molybdenum trioxide.The developed technology for obtaining Mo-98 from spent Tc-99m generators, its subsequent regeneration and purification showed that regenerated and purified molybdenum trioxide enriched with molybdenum-98 can be used as a feedstock for the production of industrial Tc-99m generators.

    • Utilizing Geometric Modeling and Blender for Multimedia Support in Teaching Technological Processes in Engineering Education

      pg(s) 296-299

      University-level instruction in technically oriented subjects requires effective and illustrative tools for visualizing complex manufacturing processes. Academic staff in engineering disciplines generally possess solid knowledge and experience in using CAD systems for geometric modeling, which are a core component of modern technical education. However, the use of graphical systems for creating animations remains underutilized in many curricula. This paper presents an approach that builds on existing CAD models, created in widely used engineering software (e.g., SolidWorks or Inventor), and transforms them into professional multimedia teaching aids using the opensource software Blender. Using the example of cold drawing of seamless tubes, the complete process is demonstrated — from model creation and export to the animation of material deformation. Once a 3D model has been developed, only a small step is required to create a visually compelling and pedagogically valuable animation. Such multimedia outputs enhance the educational process, make the learning experience more attractive and engaging for students, and facilitate deeper understanding of complex technological phenomena. The article concludes with methodological recommendations for university educators on how to effectively integrate multimedia tools into engineering education with minimal additional effort.

  • MATERIALS

    • The highly dense titanium based metal matrix composites reinforced TiC densified by hot pressing

      pg(s) 300-302

      Titanium–titanium boride (Ti/TiC) metal matrix composites have been widely identified as promising materials for various applications. The traditional ingot metallurgy processing strategies used to fabricate these materials are energy intensive and have fallen short of their perceived mass production potentials. Powder metallurgy processing of Ti/TiC composites from titanium and TiC powder blends, is currently widely used for the cost-efficient production of such composites. Additional processing by the method of hot pressing improves the structure and mechanical properties of this class of materials. The composites have the heterogenous microstructure with areas high hardness area over 1173 HV. While matrix and inclusions had the value of 700 HV.

    • Study of the influence of combined thermomechanical processing modes on the mechanical properties of economically alloyed steel 5KHV2S

      pg(s) 303-305

      Despite the rapid development of metallurgical processes for the production of semi-finished products aimed at improving the modes of smelting, casting and crystallization, a significant improvement in the properties of any cast metal, ensuring its wide application in modern mechanical engineering, is achieved by combined thermomechanical processing of workpieces, combining hot metal forming and heat treatment. The technologies and equipment currently used in Kazakhstan by machine-building manufacturers have long been obsolete and ineffective. A common problem for everyone is the high energy intensity of production, its low productivity and the quality of forgings and blanks produced, which leaves much to be desired. Namely forgings and blanks are the starting materials for the manufacture of highquality tools and technological equipment at mining and metallurgical engineering enterprises. Therefore, the purpose of this work is to develop rational modes of thermal and thermochemical processing of 5KHV2S steel, previously forged in a tool that implements alternating strain in metal, as well as to study the influence of combined thermomechanical processing modes on the mechanical properties of this steel. The studies carried out in this work on the hardness of 5KHV2S steel samples subjected to combined thermomechanical processing showed that the developed technologies contributed to an increase in both total and surface hardness compared with samples not subjected to preforging in a new forging tool that implements alternating strain in the metal.

    • The Influence of Heat Treatment on Mechanical and Corrosion Properties of High- Chromium White Cast Irons Modified by Titanium and Boron

      pg(s) 306-309

      The effect of individual additions of Ti and B into high chromium white cast irons (HCWCIs) on the structure, corrosion and selected mechanical properties was investigated. Two different heat treatments were applied, high-temperature treatment at 960 oC/1h, and subcritical treatment at 550 oC/4 h. The microstructure was investigated by OM and SEM; compositions of matrix and carbides were analyzed by EDS. Mechanical behavior of HCWCIs was analyzed by measuring hardness, toughness, abrasive/wear resistance and resistance to repeated impacts. Corrosion behavior was evaluated electrochemically, by linear and Tafel polarization methods in 0,1M NaCl solution. The properties of the modified HCWCIs were compared with the properties of the base unmodified HCWCI alloy (ASTM A532-IIE).