Metallurgist最新文献

Gas purification in ferroalloy furnaces is vital for the efficiency and quality of the entire production process. To enhance the efficiency of the gas purification system, an upgrade to the bag filter regeneration control system has been proposed. Using the SimInTech dynamic modeling environment, the performance of the control system was evaluated before and after modernization. Key quality indicators and misalignment errors were calculated to assess the proposed engineering solution. The speed increased by 3.8 times, reducing response time to 2.9 s, the stability increased by 3 times, achieving a stability degree of 1.05, the reliability of the control system increased by 4.2%, reaching a reliability rate of 96.3%, and the misalignment error decreased by 30 s, resulting in a misalignment error of 25 s. Operational data from the Aktobe Ferroalloy Plant were used to assess the impact of the modernization on productivity, energy efficiency, and the overall quality of the gas purification system. The average efficiency coefficient of the regeneration system was determined to be 34.75%.

The paper addresses the issue of early detection of steel ladle slag in the continuous casting of steel. In this study, the vibration method of slag detection was evaluated due to the high informative value of the vibration signal. The analysis is based on the variation in the character of the vibration acceleration signal of the protective tube manipulator of the continuous casting machine when slag enters the intermediate ladle. The envelope method of the vibration power spectrum was used to derive five empirical criteria for slag cut-off. In addition, these criteria included data on the molten mass in order to reduce the occurrence of false alarms. A generalized measure was developed to determine the performance quality of the criteria which was estimated to be 91.79%. This result validates the efficiency of these criteria and their suitability for testing in real production conditions.

The composite powder containing Al₃Ni and Al₃Ni₂ intermetallic compounds was obtained by vacuum synthesis to reinforce the aluminum matrix of the developed composite. For this purpose, nickel and aluminum powders were mixed in a ball mill, followed by heating the resulting mixture in vacuum to 650 °C to initiate an exothermic reaction between the powder components. To obtain an Al–Al₃Ni composite, the synthesized composite powder and matrix aluminum powder were mixed in a mill, followed by compacting the resulting mixture and sintering the obtained samples in vacuum. It has been found that vacuum synthesis results in the formation of a composite powder with heterogeneous phase composition, including Al₃Ni, Al₃Ni₂, Al₄C₃, and Al. Carbon formed as a result of thermal decomposition of stearin on the surface of aluminum particles reacts with aluminum to form aluminum carbide. After sintering the compacted mixture of aluminum and composite powders, a composite reinforced with Al₃Ni and Al₄C₃ phases is formed. Tribological tests have shown that the obtained composite is a promising wear-resistant material with hybrid reinforcement by intermetallic and carbide phases.

The paper considers the results of a study on the oxidation kinetics of lead babbit B(PbSb15Sn10) with calcium in a temperature range of 373–473 K. In addition, the resulting oxidation products of alloys and their microstructure are examined. The studies were carried out using the thermogravimetric method in air at atmospheric pressure within the temperature range of 373–473 K. It was found that the oxidation process in the entire studied temperature range can be accurately described by a degree four polynomial. In the experiments, a variation in the oxidation rate was measured over time. The kinetic and energy parameters of the alloy oxidation process were determined. It was found that calcium additives increase the oxidability of the initial alloy B(PbSb15Sn10) in the temperature range of 373–473 K. It was demonstrated that the additives of the alloying component significantly alter the alloy microstructure. X‑ray diffraction analysis revealed that the oxidation products of lead babbit B(PbSb15Sn10) with 1.0 wt % calcium include the following oxides: Pb₂Sn₂O₆; PbO; Sn₂O₄, SnO, Pb_0.866O_{2, Sb2O5}, Ca(Sb₂O₆), and Ca₂Sb.

In this work the effect of 2% calcium on the structure, deformability and physicomechanical properties of Al-3%Mg‑0.8%Mn alloy is investigated. A hot rolling temperature of 400 °C for the alloy with calcium without prior homogenization appeared to be low, resulting in cold rolled sheets containing multiple defects, in contrast to a refrence alloy without calcium. During homogenization annealing at 550 °C aluminum-calcium eutectic is highly fragmented, which facilitates rolling. Evaluation of alloy with calcium resistance to recrystallization shows that hot-rolled sheets begin to lose strength after 250 °C, while for cold-rolled sheets this temperature is limited to 200 °C. Cold-rolled sheets of Al-3%Mg‑0.8%Mn alloy also have a temperature for the start of recrystallization of 250 °C, which is associated with liberation during hot rolling of nanosized dispersoids of Al₆(Mn, Fe) phase, which as a result of heterogenization at 550 °C have micron sizes. At the same time, cold-rolled sheets with added calcium have higher hardness and yield strength after one-hour annealing at 400 °C (71/61 HV and 124/107 MPa). Relative elongation is also better for alloy with added calcium. It is also shown that calcium addition increases corrosion current density from 0.71·10⁵ to 0.92·10⁵ A/m², while its value remains at the level for AMg5 alloy or grade 5182 alloy.

Axial chemical inhomogeneity in metals is a common issue in the production of thick-sheeted products from microalloyed pipe steels. To study the behavior of liquation zones during rolling, a model has been developed to describe and analyze the stress-strain state throughout the rolled section, including the axial chemical inhomogeneity zone. This mathematical model was implemented using the finite element software Abaqus. This paper investigates the influence of deformation direction (longitudinal and transverse), degree of deformation, and metal temperature on the changes in chemical inhomogeneity during thick-sheeted rolling. It has been found that the degree of deformation has the greatest influence on the transformation of chemical inhomogeneity. The results suggest that rolling with a reduction of at least 10–15% is optimal, since this level of deformation significantly enhances the fragmentation of chemical inhomogeneity. This is achieved by increasing the stress and strain intensities in the axial zone, which helps break the bonds between different areas of chemical inhomogeneity of the metal.

Heat-resistant nickel alloys are promising materials for manufacturing structural elements used in high-temperature nuclear power plants. Nickel alloys are characterized as difficult-to-weld materials; this is one of the main factors limiting their use. This paper presents the results of the development and industrial exploitation of welding technology for heat-resistant nickel alloy grade CrNi₆₂MoCh₂-VI (EC 199-VI). The quality control results of the obtained welded joints are presented. Notably, the welded joints of the CrNi₆₂MoCh₂-VI alloy exhibit resistance to intercrystalline corrosion and demonstrate improved mechanical characteristics.

On the basis of the results of experimental studies aimed at the investigation of the influence of dielectric permittivity of a working liquid on the size characteristics of powders obtained under the conditions of electroerosion metallurgy of the wastes of TN20 tungsten-free hard alloy, it was discovered that the higher dielectric permittivity of water leads to a greater loss of the pulse energy required for its breakdown than in the case of breakdown in ethanol and the formation of powder characterized by a smaller average size of particles, namely, 14.3 and 28.4 μm, respectively. The results of conducted experimental studies enable us to solve the problem of recycling of the wastes of tungsten-free hard alloys and their subsequent utilization, thus reducing the cost of production of cutting tools.

Presently, the main trend in thin-sheet steel production, including the high-strength automobile steel, is to reduce production costs while retaining essential properties and quality. A considerable part of the cost of high-strength steel comes from alloying with expensive chemical elements such as vanadium and niobium. Simply reducing the content of these elements in finished products would compromise the mechanical properties of rolled products, leading to inferior quality and defects. This work, based on statistical analysis for steel grade S355MC, demonstrated the potential to reduce alloying while maintaining the required yield strength by adjusting the hot rolling conditions. It was also revealed that, in addition to the concentration of chemical elements and the hot rolling mode, the thickness of the finished product affects the tensile strength. Therefore, the analysis was performed exclusively on products with a thickness of 4 mm. The study resulted in a regression equation that illustrates the dependence of yield strength on vanadium content and hot rolling parameters.

The paper addresses the importance of using aluminum for the production of drill pipes. It also discusses one of the problems associated with the production of drill pipes having a protective thickening (central upset), such as the formation of a “streak delamination” type defect in the protector formation zone. Pipes with internal end and central upsets made of alloy D16T were selected as study objects. The extrusion process was performed under the following two experimental conditions: workpiece metal temperature—440 °C, punch travel speed—1.4 mm/s (option 1) and workpiece metal temperature—4 00 °C, punch travel speed—0.9 mm/s (option 2). It has been experimentally established that lowering the workpiece metal temperature by 40 °C and punch travel speed by 0.5 m/s during the extrusion process promotes the formation of a homogeneous macrostructure. By simulating the described experimental options of the processes, it was found that a 40 °C decrease in the workpiece metal temperature and a 0.5 m/s decrease in the punch travel speed during the extrusion process lead to a 50% reduction in the maximum deformation rate in the deformation zone, and to a 14% reduction in the degree of deformation. By calculating the stress condition parameter in the deformation zone, it became possible to show that performing the process according to option 2 results in a more favorable stress condition of the metal compared to option 1, which could also contribute to the reduction in the number of “streak delamination” type defects in the protector zone.