Metallurgical and Materials Transactions B最新文献

The multi-lance top-blown converting furnace is pivotal in the converting process of molten white matte (copper content nearly 75 pct) in continuous copper smelting technology. The complex multiphase hydrodynamics and phase interaction mechanisms inherent in this furnace significantly influence converting efficiency of blister copper. This study numerically explores the intricate gas–melt flow hydrodynamics and stirring dynamics in the multi-lance top-blown converting furnace based on the OpenFOAM platform. Following model validation, this study elucidates various aspects of bath dynamics in the furnace. The findings reveal that the arrangement of multiple lances along the longitudinal axis introduces an offset effect on longitudinal momentum transfer and a superposition effect on transverse momentum transfer, unlike the single-lance blowing configuration. A linear empirical relationship between jet momentum number and length group under multi-lance top blowing is established, with a determined constant value of 3.65 for turbulent gas jet. Additionally, a strong correlation between dimensionless cavity shape index and the kinetic energy of molten slag is observed, leading to the formulation of a functional relationship equation demonstrating exponential growth: E_b = exp(− 2.81011–0.79077 ({I}_{text{cm}}) + 0.13479 ({{I}_{text{cm}}}^{2})). Moreover, both the internal flow of molten bath and the shear stress on the furnace wall exhibit a step-like periodic oscillation mode. Notably, based on the similarity observed in the main frequency peaks, a robust correlation between the two phenomena is inferred. Under conditions of small lance spacing and diameter, an increase in the cavity aspect ratio enhances momentum transfer efficiency and stirring performance of bath, but it also exacerbates erosion of the lances and the furnace. This study elucidates the multiphase mixing characteristics, phase interaction mechanisms, and furnace wall erosion patterns in a multi-lance top-blown converting furnace, providing a crucial theoretical foundation for the design, operation, and optimization of such systems.

The vacuum carbon deoxidation process via CO formation has the ability to achieve high cleanliness of nickel alloys in vacuum induction melting. In the present study, the effect of vacuum degree in melting chamber, melt temperature, and initial carbon content on deoxidation efficiency was studied. The reactions of vacuum carbon deoxidization and MgO decomposition were strongly affected by chamber pressure and melt temperature. Low chamber pressure and high melt temperature resulted in a severe MgO-crucible decomposition reaction and increased oxygen supply to molten nickel alloy, and hence, decreased the deoxidation efficiency. Therefore, moderate vacuum degree in the chamber and lower melt temperature would improve the vacuum carbon deoxidation efficiency. The reaction rates of vacuum carbon deoxidization and MgO decomposition were controlled by the mass transfer of oxygen in liquid boundary layers near the reaction interfaces. The nitrogen in molten nickel alloy could be well removed together with carbon deoxidation under the vacuum conditions in the present study. A prediction model of deoxidation and carbon loss in vacuum melting process was established to determine the optimum temperature and vacuum conditions in vacuum carbon deoxidation process.

Efficient and stable lithium-ion batteries (LIBs) have garnered considerable attention; yet, the development of anode electrode materials continues to pose substantial challenges. While CoO electrode material boasts an ideal specific theoretical capacity, it is not without drawbacks, including significant volume expansion and concerns over safety performance, which hinder its viability as an anode material. In this research, we synthesized CoO/Co₃O₄ through a straightforward secondary hydrothermal treatment that locally oxidizes CoO, simultaneously creating oxygen vacancies. The incorporation of oxygen vacancies enhances the material’s internal conductivity and expedites the diffusion of electrons and ions, culminating in superior rate performance. Furthermore, the heterojunction structure diminishes the diffusion barrier, significantly enhancing the electrode’s reaction kinetics and overall electrochemical performance. At a modest current density of 0.1 A g⁻¹, the CoO/Co₃O₄ composite demonstrates enhanced cycling stability, delivering a capacity of 1022 mAh g⁻¹ after 100 cycles. Remarkably, even at an elevated current density of 1 A g⁻¹, it sustains a capacity of 768.8 mAh g⁻¹ over 400 cycles. The method of creating oxygen vacancies via autoxidation may pave the way for the advancement of multivalent oxide anode materials.

As the production of high-quality titanium (Ti) metal increases significantly, the generation of low-quality Ti scraps increases and exceeds the demand for current cascade recycling in ferrous metallurgy. Therefore, the development of an upgrading recycling technology, in which scraps are refined and reutilized, is required. The magnesium (Mg) deoxidation assisted by the formation of oxychlorides of rare earth metals is currently considered a promising process for upgrading recycling technology, during which YOCl is formed as a byproduct. In this study, we investigate the synthesis and separation of YCl₃ from YOCl via carbochlorination at 973 and 1073 K and confirmed that YCl₃ can be regenerated from YOCl at a high conversion rate (82.7 pct at maximum). YCl₃ was also formed even in the presence of MgCl₂; however, MgCl₂ decreased the conversion rate (49.8 pct at minimum). The conversion rate in the temperature region where YCl₃ is a liquid (1073 K) was lower than that in the temperature region where YCl₃ is a solid (973 K). Therefore, an operation with temperature cycling, in which YCl₃ is formed at a temperature where YCl₃ is a solid and then the temperature is increased to a temperature where YCl₃ is a liquid to drain the molten mixed salt, is efficient.

Improving the corrosion resistance of carbon steel is of great importance to realize widely use in various industries. The anti-corrosion coating is a significant protective strategy. Therefore, uniform aluminum coatings (AlO_x-CS), electrodepositing in ionic liquid electrolyte at room temperature, was developed to enhance corrosion resistance of carbon steel. The lower part of the electrode has a better distribution uniformity than the upper part of the electrode, and the distribution of a line has the lowest variance. The uniform AlO_x-CS coating is the most corrosion resistant due to sealed Al₂O₃ layers. The corrosion rate of the AlO_x-CS coating is 0.4 mm a⁻¹. The self-corrosion current density of AlO_x-CS coating is 34.4 μA cm⁻², nearly 2 times compared with pristine carbon steel. The impedance value with AlO_x-CS coating is increased by nearly 300 times compared with pristine carbon steel. The morphology and composition of aluminum-based reinforced coatings had no significant changes in atmospheric exposure, 3.5 pct NaCl salt spray and 3.5 pct NaCl immersion environments. The aluminum-based reinforced coatings can enhance the lifespan of carbon steel materials, while also reducing economic losses and safety hazards.

Vanadium redox-flow batteries (VRFBs) have recently gained attention because they resolve the intermittent and uncontrollable characteristics of renewable energy sources. Consequently, the increasing demand for VRFBs will increase the demand for V. This study investigated a roasting process for V extraction from Korean vanadiferous titanomagnetite ores. The optimum roasting conditions and mechanisms were studied for the combination of Na₂SO₄ roasting and water-leaching processes. The effects of roasting temperature and mixing ratio of Na₂SO₄ were investigated, revealing the more prominent effect of roasting temperature compared with that Na₂SO₄ mixing ratio. The leaching efficiencies for other impurities were investigated by varying the Na₂SO₄ mixing ratio and roasting temperature. The X-ray-diffraction-analysis results indicated no notable phase change during the roasting process. Moreover, the hot-stage-microscope-analysis results demonstrated that the roasting temperature was higher than the softening temperature, implying no reaction between the liquidus and solid ore. The formation of sulfuric gas was verified by thermodynamic calculations, differential scanning calorimetry, and evolved gas analysis. The reaction of V₂O₅, SO₃, and SO₄ was expected to form a water-soluble VOSO₄ phase. The gas–solid reaction in the Na₂SO₄ roasting process resulted in high selectivity and high leaching efficiency for V.

The present study delves into the challenges of slurry erosion in hydropower plant components, particularly focusing on Stainless-Steel 304 (SS304) limitations under high-velocity conditions. It proposes Mo₂C coating combinations applied via High-Velocity Oxy-Fuel (HVOF) spraying as a promising solution due to their high hardness, wear, and corrosion resistance. Three coatings (Coating A, Coating B, and Coating C) were formulated with varying Mo₂C, Co–Ni, and graphene nanoparticles (GNP) percentages, demonstrating unique erosion-resistant properties. Microscopic analysis revealed wear mechanisms, with Coating A displaying particle breakage, Coating B exhibiting fractured Mo₂C particles, and Coating C showing dynamic interactions with GNP, enhancing resistance. The findings suggest that tailored coatings incorporating GNP offer potential for erosion resistance improvement, prompting further exploration into optimizing GNP concentrations, refining deposition techniques, and assessing long-term durability under diverse operational conditions.

An advanced 2D axisymmetric magnetohydrodynamics model, including calculations for electromagnetic, thermal, and flow fields, fully coupled with a thermal stress-strain model, allowing the computation of solid mechanical parameters like stress, strain, and deformation within the ingot of the vacuum arc remelting process is presented. This process encounters challenges due to solidification shrinkage, which causes losing contact between the ingot and the mold, reducing the cooling efficiency of the system, resulting in a deeper melt pool and decreasing ingot quality. Herein, the width of the air gap along the ingot, the precise position of contact between the ingot and mold, and the profile of the melt pool, affected by gas cooling, are calculated. The global pattern of transport phenomena, such as (electro-vortex) flow and electromagnetic fields in the bulk of the ingot, is insensitive to helium gas cooling through the shrinkage gap. However, including gas cooling significantly improves heat removal through the mold, which consequently reduces the pool depth of the Alloy 718 ingot, leading to an improvement in the quality of the ingot.

Recycling presents a waste-free solution to substantial disposal of welding slags which retain most components originated from the original fluxes. However, uncertainties in weld appearance and element contents render it unjustified to reuse welding slags as fluxes. In the present study, a manganese-silicate flux has been demonstrated to be fully recyclable subject to submerged arc welding (SAW) for three times. The weld appearance is assessed against the initial weld metal (WM), while alloying element contents are evaluated according to AWS (American Welding Society) requirements. Flux composition and structure, two decisive factors affecting welding performance, are quantified. It is manifested that compositional changes mainly occur in the contents of MnO (39.50 to 34.66 wt pct), SiO₂ (38.46 to 34.25 wt pct), and Fe_tO (1.55 to 6.78 wt pct). Moreover, crystalline structures of MgMnSiO₄, and Mg_0.6Mn_1.4SiO₄ appear in the initially amorphous flux. The crystallinity is enhanced to 32.7 wt pct through flux recycling. Slight depolymerization is found in the amorphous structure, as the NBO/Si (non-bridging oxygens per silicon atom) is elevated by 0.2. Overall, this study demonstrates the capability of recycling welding fluxes and is poised to offer insight into further sustainable applications.

The rare earth element Gd was added into a resulfurized steel to enhance its performance. Non-metallic inclusions in the steel, the hardness and the microstructure of the steel were analyzed. The addition of Gd resulted in the formation of Gd–O–S and Gd–S inclusions which served as cores of MnS inclusions so that the resistance to the deformation of inclusions was improved. When the content of the total gadolinium (T.Gd) increased from 0 to 198 ppm, the hardness of the steel matrix increased from 60.4 to 80.4 HRA. The microstructure predominantly consisted of a substantial number of pearlites with a minor presence of ferrites distributed in a network-like pattern. The distribution of ferrites along the grain boundary was weakened when the T.Gd content in the steel was 79 ppm. The tensile fracture of the steel exhibited a mixed ductile-brittle pattern while its impact fracture displayed brittle characteristics.