Metallurgist最新文献

This study presents the results of an investigation into liquid-phase iron reduction technology. The goal of this technology is to improve the energy efficiency and environmental sustainability of metallurgical production. The primary objective was to determine the optimal composition of iron ore materials and the key parameters of the reduction process in order to minimize energy consumption and harmful emissions. Our methodology incorporated experimental tests in a Tammann furnace, thermodynamic calculations using the IVTANTHERMO software package, and mathematical modeling of the reduction process. Our findings suggest that an iron concentration of 53% in the raw material achieves a reduction degree of up to 99%. The study determined that the CO₂ emissions associated with liquid-phase reduction are 0.95 tons per ton of product. This figure is 1.6 times lower than the emissions associated with sinter-coke blast furnace technology and 1.3 times lower than the emissions associated with the MIDREX process. This work defines the optimal parameters for the reduction process and demonstrates a substantial reduction in the carbon footprint achievable with the developed technology. The potential for industrial implementation of this technology underscores the practical significance of the research. This technology can be used to produce high-quality iron-containing materials. It has minimal resource consumption and atmospheric emissions.

This analysis examines the boiling and condensation processes of heat carriers and presents the calculated heat transfer coefficients for these processes, which were incorporated into FloEFD simulations. Additionally, this study uses FloEFD solutions to model the circulation of the vapor-water mixture within the first cooling circuit of a cylindrical crystallizer with an evaporative-condensation cooling system. The calculations were performed using the adopted average coefficients, the dimensions of the first circuit elements, and the crystallizer design. The mass concentration of the heat carrier, the temperature of the mixture, the wall temperatures, and the velocity of the mixture circulation were determined for an average applied heat flux density of 1 MW/m². These calculations provide information for the modernization of the crystallizer, which aims to eliminate non-uniform cooling around the perimeter of the cylindrical steel billet. The highest vapor velocities, reaching 2–3 m/s, occur in the steam line, while the highest condensate velocities occur in the condensate line.

The article examines the effect of specific features of individual technological stages of manufacturing large-diameter straight-seam welded pipes, such as forming, assembly, and welding, on the accuracy and stability of the geometric parameters of welded seams. Technological recommendations are provided to minimize deviations of these parameters from the standardized values included in the user requirement specifications.

The study of corrosion resistance in the marine environment of 7 low-carbon steels similar in composition to shipbuilding steels was carried out using three different methods, including modeling of marine conditions. It was found that alloying with chromium, nickel and copper in concentrations of approximately 1, 2 and 0.4 wt. %, respectively, increases corrosion resistance, despite contamination with non-metallic inclusions that accelerate the corrosion process. With a decrease in the concentration of alloying components, the presence of non-metallic inclusions of various types leads to deterioration in corrosion resistance. Microalloying with carbide-forming elements can also have a negative effect due to the formation of nanosized phase precipitates.

Electromagnetic stirring (EMS) is widely used to control the solidification of continuously cast billets (CCBs). By promoting melt flow, it enhances heat and mass transfer under transient thermal conditions and can suppress radial macrosegregation by altering the transport of solute-enriched liquid and non-metallic inclusions (NMIs) toward the CCB centerline. Microsegregation is often underappreciated, although its development drives structural banding and degrades the mechanical and service properties of finished products. We compare the cast-metal structure of 26KhGMFA steel billets produced with and without EMS. Based on measurements of cast-structure parameters (e.g., dendrite metrics), the distribution of NMIs, and the microsegregation of elements, we quantify the effect of EMS applied in the primary cooling zone on the solidification of the CCB and the evolution of structural and microsegregation heterogeneity.

The authors studied the microstructure and mechanical properties of welded 34 mm joints of cold-resistant microalloyed heavy plate steel P460NL1 (specification EN 10028–3:2019), intended for use in high-pressure vessels, including mobile CO₂ storage tanks. The V‑groove welds were obtained by automatic submerged arc welding (process SAW 121–2) with heat input of 1.5±0.1 kJ/mm. The microstructural transformation patterns in the heat-affected zone (HAZ) and weld metal were analyzed, along with microhardness, and impact energy was determined at sub-zero temperatures. The steel weldability under controlled thermal severity (CTS) was examined, and a bead-on-plate (BoP) test was performed. In addition, aging tests were conducted to assess the effect of the base metal on impact toughness, and high-temperature tensile tests in the temperature range of 50–450 °C were performed to evaluate the level of strength characteristics of the base metal over a wide range of operating temperatures.

We compare three methods for quantifying the volume fraction of nonmetallic inclusions in steel: (i) automatic image analysis in accordance with ASTM E1245-03, (ii) fractional gas analysis (FGA) of O, N, and S with conversion to the volume fraction of inclusions, and (iii) spark optical emission spectrometry with pulse discrimination analysis (spark OES-PDA) supported by proprietary software that converts spectral line intensities into the volume fraction of nonmetallic inclusions, calibrated against quantitative metallography data.

We further propose an automated method to infer the oxide composition of inclusions from FGA data. The method is based on a mathematical model describing CO evolution during carbothermic reduction and the dissociation of oxide inclusions under non-isothermal heating. Model parameters are estimated using RMSProp with automatic differentiation, minimizing a loss function that balances data-fit accuracy with physically motivated constraints.

All the three methods yield broadly consistent estimates for the volume fraction of inclusions, with systematic differences among the methods. In all cases, the FGA-based calculation produced the highest values. On average, measurements per ASTM E1245 were 0.024% lower than the FGA calculation, whereas PDA results either agreed with it or were, on average, 0.017% lower, depending on specimen type.

This study investigates the influence of deposition parameters on the microstructure and physical-mechanical properties of TiZrNb-based vacuum ion-plasma coatings applied to nickel-titanium (TiNi) implants. Reducing the arc current from 110 to 90 A was found to increase the volume fraction of the β‑phase and decrease the α‑ and α′′-phases. This phase transformation correlates with a decrease in the elastic modulus (E) of a monolithic Ti18Zr13Nb (at %) coating from 90 to 72 GPa and a reduction in nanohardness (H) from 5.4 to 4.3 GPa. Consequently, the mechanical properties of the coating approach those of the underlying TiNi substrate. The results demonstrate that creating a functionally graded coating structure by saturating a pre-deposited Ti18Zr13Nb layer with nitrogen increases nanohardness H to 6.5 GPa. Furthermore, fabricating a graded multilayer architecture with alternating Ti18Zr13Nb and mononitride (Ti, Zr, Nb) N layers, with the nitride layer thickness gradually increasing from the substrate to the surface, increases the nanohardness to 12.5 or 16.4 GPa, depending on the specific architecture of the coating. This study also found that depositing these functionally graded coatings, which have a gradual increase in hardness from the substrate to the surface, improves the resistance of TiNi implants to pitting and fretting corrosion in a 0.9% NaCl solution.

This study focuses on the optimization of protective equipment for the tundish in the steel casting process. Specifically, it addresses the designs that shield the tundish wall from the liquid metal stream flowing from the ladle. A mathematical model was developed to simulate steel flow behavior. The simulation results indicated that the tundish pouring chamber design required modification. The newly developed components facilitate a more rational distribution of steel streams within the pouring chamber. This prevents severe erosion of the gunning mix lining and reduces the formation of non-metallic inclusions in the liquid metal before it enters the mold.

Contemporary industrial manufacturing requires materials with enhanced properties that are crucial for producing modern devices, machinery, and mechanisms featuring higher productivity, reliability, and durability. Intermetallic alloys of the Fe–Al system are among the most promising materials for mechanical engineering because they combine low cost with a range of important physical-mechanical and operational characteristics. Iron aluminides and their alloys have been successfully implemented as functional coatings. These coatings increase product lifespan and reliability, reduce weight, and decrease costly raw material consumption. However, broader adoption of these alloys in general industrial practice, including use as independent structural materials, is hindered by several challenges. These challenges involve improving the overall properties of the alloys, specifically increasing ductility while maintaining strength and hardness and reducing porosity. Additionally, existing production methods are problematic due to their technological complexity, multistage nature, and lengthy processing times. This study presents a potential solution to these challenges: applying centrifugal forces to alloys produced via aluminothermy with tungsten alloying during crystallization. The density of the investigated alloys increased from 5788 to 7271 kg/m³, and porosity decreased from 18.85% to 0.27%. Microhardness decreased from 317–362 HV to 306–323 HV, and compressive strength increased from 1350 to 1598 MPa. This increase in strength was accompanied by a change in strain from 26.76% to 35.27%. There was a slight reduction in grain size, from 105–680 µm to 102–400 µm. Additionally, the maximum mass gain during oxidation testing was 0.39% (0.71 mg/cm²). The thermite mixture compositions used provided an aluminum content within the alloys of 13.66–14.31 wt %, corresponding to the formation of an ordered D0₃ structure, which is known for its favorable service and mechanical properties. This work confirms the fundamental feasibility of producing cylindrical, hollow billets from Fe–Al alloys with satisfactory characteristics.