The choice of materials for car bodies varies significantly, driven by the dual objectives of minimizing body weight to improve fuel efficiency and enhancing passive safety for occupants. To integrate these diverse materials, a variety of joining techniques are used, including resistance spot welding, mechanical fastening, and adhesive bonding. The selection of materials for car body production is a critical determinant of vehicle performance, safety, manufacturing efficiency, and environmental impact. The car body-in-white (BIW), which serves as the vehicle's structural framework, must meet a diverse set of requirements, including a high strength-to-weight ratio, energy-absorption capacity during crashes, formability, corrosion resistance, and cost-effectiveness. This necessitates the use of a combination of materials, predominantly various grades of steel, along with aluminum alloys, polymers, and composites. Numerical simulations in the process of optimizing clinched joints represent an extremely effective tool that allows us to shorten the time of technology development and reduce the number of time-consuming and financially demanding experimental tests. However, the simulation outputs must be systematically verified and validated against experimental results. Only the combination of a suitable assembly and a reliably functioning numerical model with thorough experimental verification can lead to a technological solution that is operationally safe, secure and economically optimized at the same time. At the same time, the set of knowledge created in this way enables the systematic optimization of process parameters and increases the transferability of the obtained results to industrial practice.

This study investigates the influence of current intensity, relative travel speed of the TIG torch on the cylindrical S45C steel surface, and axial displacement speed on hardness distribution in deep layers after arc quenching. The process forms three distinct zones: quenched, heat-affected, and base metal. The quenched zone transforms from the original ferrite–pearlite structure into martensite, residual austenite, and bainite. The heat-affected zone contains bainite, pearlite, and ferrite. These phase variations result from rapid heating and cooling. Hardness evaluation across 25 cases shows the 0.4–0.6 mm range provides the most stable and highest hardness. Taguchi analysis reveals that axial travel speed mainly affects arc width and has little influence on hardness by depth. In contrast, current intensity strongly impacts heat input: higher current increases heating from the TIG tip, while higher relative travel speed reduces heat input. The highest hardness values were identified at different depths: 37.7 HRC at 0.2 mm (case 17), 38.2 HRC at 0.4 mm (case 21), and the maximum for 0.6 mm occurred in case 2 with 42.3 HRC. At deeper layers, hardness increased significantly, with 43.8 HRC at 0.8 mm (case 1) and 41.7 HRC at 1 mm (case 1). The results of the study confirm that variations in current intensity and relative travel speed play decisive roles in determining the hardness distribution of S45C steel subjected to TIG arc quenching.

This study presents an experimental approach to the synthesis of silicon carbide (SiC) using technogenic and biogenic wastes—microsilica and rice husk. The synthesis was carried out by carbothermal reduction in a self-designed and constructed laboratory resistance furnace. The starting materials were subjected to preliminary mechanical activation in a planetary centrifugal mill, which enhanced their reactivity. The morphology and elemental composition of the samples were examined using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results demonstrated the formation of characteristic SiC crystals and confirmed their composition, close to stoichiometric. X-ray diffraction analysis revealed the presence of β-SiC (3C) and hexagonal polytypes (4H, 6H-SiC), as well as secondary phases of silicon dioxide (cristobalite, tridymite), reflecting the specific features of the reaction at high temperatures. It was established that mechanical activation promotes more intensive SiC formation and reduces the amount of residual oxide phases. The obtained results confirm the potential of utilising secondary silicon-containing resources for SiC synthesis, which is significant for the development of environmentally oriented technologies and for expanding the raw material base for high-value-added materials.

Partial joint penetration (PJP) welding is widely applied in structural, mechanical, and piping systems where full penetration is not required, offering benefits in cost, time efficiency, and reduced heat input. The main goal was to evaluate the effects of Heat Input on the weld geometry and ultimate tensile strength of low-carbon steel tubes. Therefore, the welds were carried out using Orbital TIG Welding, designed to achieve partial joint penetration (PJP). The number of experiments and the welding parameter matrix were created using the Taguchi method (L9) for various diameters of Ø48×3.2mm, Ø60×2.6mm, and Ø89×2.9mm. The results indicated that, under the same Heat Input levels, variations in tube thickness had a greater impact on weld profile and ultimate tensile strength than changes in diameter. Furthermore, the ANOVA analysis ranks the influence of welding factors on tensile strength. This study proposes an optimal set of welding parameters and predicts the corresponding tensile strength for each pipe diameter, thereby providing valuable insights for improving the reliability and performance of welded joints.

Due to the sharp increase in demand and prices for nickel and cobalt, the search for new sources of raw materials has become a pressing issue. This study presents a comprehensive thermodynamic and kinetic analysis of the combined method of oxygen-deficient oxidative roasting and subsequent acid leaching to extract nickel and cobalt from pyrite waste sourced from Kazakhstani enterprises. The thermodynamic analysis showed that, under oxygen deficiency, thermal decomposition of higher sulfides forms non-stoichiometric, soluble lower sulfides of iron, nickel, and cobalt. The kinetic study revealed that the process is complex and multi-stage, and that it proceeds at a high rate in the 610–680 °C range, where kinetic factors control it. Activation energies were calculated for three stages: 105–115 kJ/mol for Stage I (450–479.3 °C), 310–320 kJ/mol for Stage II (661.8 °C), and 390–420 kJ/mol for Stage III (749.7–789 °C). Experimental studies confirmed the effectiveness of roasting at 700 °C for 60 minutes. Subsequent sulfuric acid leaching of the obtained sinders under optimal conditions (sulfuric acid excess coefficient R of 1.5 times the stoichiometric amount, temperature of 100 °C, and a duration of 2 hours) yielded high metal recoveries: 94.5% Fe, 93.4% Ni, and 91% Co. The developed technology, combining thermal activation and leaching, proved effective and is recommended for processing similar raw materials.

This study explores the influence of high-carbon retained austenite content, as modulated by niobium additions and austempering time, on the hardness, wear resistance and impact toughness of ductile iron. Four alloys containing 0, 0.1, 0.2 and 0.3 wt.% niobium were austempered at a constant temperature of 350 °C for 15, 30, 60 and 90 minutes. Alloys with higher niobium contents (0.2 and 0.3%) reached their maximum retained austenite fractions at 30 minutes (40.67 and 41.98%, respectively), while peak values for the 0 and 0.1% niobium alloys were observed at 60 minutes. A clear inverse relationship was found between hardness and retained austenite content, with lower hardness values corresponding to higher austenite fractions enriched in carbon.

Oxidative roasting aims to convert rhenium into a water-soluble form, followed by leaching into solution and subsequent sorption–desorption steps to obtain ammonium perrenate. It was found that the presence of iodine significantly affects the technological parameters of rhenium extraction during sorption and desorption stages, reducing the ion-exchange capacity for rhenium due to the simultaneous transition of iodide and perrenate species into solution. The main objective of this study was to determine the technological parameters that ensure effective separation of iodine and rhenium during oxidative roasting. Experimental data showed that the maximum transfer of rhenium (up to 95.6%) into water-soluble compounds occurs at 300–400 ℃, when iodine compounds have not yet volatilized. At temperatures above 400 ℃, iodine sublimates mainly as PbI₂, accompanied by a decrease in rhenium extraction efficiency. It was experimentally established that, under optimal roasting conditions, rhenium is concentrated in the solid phase as perrenates and iodides, ensuring almost complete dissolution during subsequent leaching. The volatilisation of iodine at elevated temperatures leads to the decomposition of rhenium iodides and the formation of insoluble metallic phases, thereby negatively affecting extraction.

This work investigates the surface hardness after arc quenching S45C steel with a convex surface, including arc length, current intensity, travel speed, gas flow rate, and the pulse duration. The surface hardness is mostly determined by the intensity of the current. Interestingly, the convex surface shows an impressive 108% increasing from its initial hardness of 182 HV. Increased heat input at high current intensity may be the cause of the overheating and melting phenomena as well as the decreased hardness. Surface hardness generally increases with increases in gas flow rate, resulting from an enhanced gas cooling rate. Similar to the gas flow rate, surface hardness rises with TIG gun travel speed. In addition, the convex surface hardness's Taguchi prediction value is 359.6 HV. The ideal parameters are 90 A for the current intensity, 2.5 mm for the arc length, 12 l/min for the gas flow rate, 200 mm/min for the travel speed, and 0.7 s for the pulse duration. In addition, 3D surface plots were also used to evaluate the degree of interaction between parameters with each other. For the S45C convex surface, the maximum case depth of the arc quenching is 3500 µm. The hardened area, the heat-affected area, and the base substrate are the three regions of the arc quenching sample's microstructure.

Alloys of the Al-Fe-Si system have a complex phase composition that determines their properties. With a certain combination of temperature and composition, the conditions for the formation of the α phase are formed. However, with decreasing temperature, the α↔β transformation is observed. Suppression of the formation of the β phase is possible by doping. The main goal of this work was to substantiate theoretically the introduction of manganese and chromium into the alloy, and to explain the required number of alloying elements through a detailed analysis of the phase composition. The temperature limits for the formation of the α phase in the Al-Fe-Si ternary system and the kinetics of its recrystallisation were revealed. A justification for the value of the mass fraction of alloying elements that contribute to the suppression of the α↔β transformation with the formation of the cubic α phase was developed. The most successful suppression of the formation of the β phase occurs with joint alloying with manganese and chromium, with the formation of a predominantly cubic phase Al15Si2(Fe, Cr, Mn)4 with a volume fraction of more than 95%, which predicts the possibility of plastic processing of iron and silicon-rich alloys of the Al-Fe-Si system.

This article presents the results of thermodynamic modeling of the process of obtaining chromium-manganese ligature from ferro-manganese ore and dust from crushing ferrosilicochrome (FeSiCr). The calculations were performed using the “HSC Chemistry” software package, where dust from crushing FeSiCr was used as a reducing agent. The analysis was performed by varying the reducing agent dust FeSiCr from 10 to 100 kg in increments of 10 kg per 100 kg of ferro-manganese ore, at temperatures of 1400°C, 1600°C and 1800°C. The mechanism of combined metallothermic reduction of chromium (Cr), manganese (Mn), and iron (Fe) was studied in a multicomponent Fe-Cr-Mn-Si-Al-Ca-Mg-O system. Based on thermodynamic data, it was found that the optimal consumption of reducing agent is 50 kg per 100 kg of ore, and the most effective melting temperature is 1600 °C, at which the best yield of chromium-manganese ligature is achieved. Additionally, laboratory tests were conducted under specific conditions, resulting in experimental samples of the ligature with the following chemical composition, %: Fe – 28.39, Cr – 16.58, Mn – 32.55, Si – 3.56.