Search Results (243)

The 1.9 billion metric tons of steel globally manufactured in 2023 justify the steel industry’s pivotal role in modern society’s growth. Considering the rapid development of countries that have not fully taken part in the global market, such as Africa, steel production is expected to increase in the next decade. However, the environmental burden associated with steel manufacturing must be mitigated to achieve sustainable production, which would align with the European Green Deal pathway. Such a burden is associated both with the GHG emissions and with the solid residues arising from steel manufacturing, considering both the integrated and electrical routes. The valorisation of the main steel residues from the electrical steelmaking is the central theme of this work, referring to the steel electric manufacturing in the Dalmine case study. The investigation was carried out from two different points of view, comprising the action of a plasma electric reactor and a RecoDust unit to optimize the recovery of iron and zinc, respectively, being the two main technologies envisioned in the EU-funded research project ReMFra. This work focuses on those preliminary steps required to detect the optimal recipes to consider for such industrial units, such as thermodynamic modelling, testing the mechanical properties of the briquettes produced, and the smelting trials carried out at pilot scale. However, tests for the usability of the dusty feedstock for RecoDust are carried out, and, with the results, some recommendations for pretreatment can be made. The outcomes show the high potential of these streams for metal and mineral recovery. Full article

The metallurgical industry is integral to industrial development. As technology advances and industrial demand grows, the annual output of metallurgical waste slag continues to rise. Combined with the substantial historical stockpile, this has made the utilization of metallurgical slag a new research focus. This study comprehensively sums up the composition and fundamental characteristics of metallurgical waste slag. It delves into the application potential of non-ferrous metal smelting waste slag, such as copper slag, nickel slag, and lead slag, in both sensible and latent heat storage. In sensible heat storage, copper slag, with its low cost and high thermal stability, is suitable as a storage material. After appropriate treatment, it can be combined with other materials to produce composite phase change energy storage materials, thus expanding its role into latent heat storage. Nickel slag, currently mainly used in infrastructure materials, still needs in-depth research to confirm its suitability for sensible heat storage. Nevertheless, in latent heat storage, it has been utilized in making the support framework of composite phase change materials. While there are no current examples of lead slag being used in sensible heat storage, the low leaching concentration of lead and zinc in lead slag concrete under alkaline conditions offers new utilization ideas. Given the strong nucleation effect of iron and impurities in lead slag, it is expected to be used in the skeleton preparation of composite phase change materials. Besides the aforementioned waste slags, other industrial waste slags also show potential as sensible heat storage materials. This paper aims to evaluate the feasibility of non-ferrous metal waste slag as energy storage materials. It analyses the pros and cons of their practical applications, elaborates on relevant research progress, technical hurdles, and future directions, all with the goal of enhancing their effective use in heat storage. Full article

This research provides a detailed investigation into the mechanical properties and microstructural evolution of heat-resistant steel P92 subjected to both initial (i) welding procedures and simulated (ii) repair welding. The study addresses the influence of critical welding parameters, including preheating temperature, heat input, and post-weld heat treatment (PWHT), with a particular emphasis on the metallurgical consequences arising from the application of repair welding thermal cycles. Through the analysis of three welding probes—initially welded pipes using the PF (vertical upwards) and PC (horizontal–vertical) welding positions, and a PF-welded pipe undergoing a simulated repair welding (also in the PF position)—the research compares microstructure in the parent material (PM), weld metal (WM), and heat-affected zone (HAZ). Recognizing the practical limitations and challenges associated with achieving complete removal of the original WM under the limited (in-field) repair welding, this study provides a comprehensive comparative analysis of uniaxial tensile properties, impact toughness evaluated via Charpy V-notch testing, and microhardness measurements conducted at room temperature. Furthermore, the research critically analyzes the influence of the complex thermal cycles experienced during both the initial welding and repair welding procedures to elucidate the practical application limits of this high-alloyed, heat-resistant P92 steel in demanding service conditions. Full article

As a critical impurity in the production of solar-grade silicon, the concentration of phosphorus (P) significantly affects photoelectric conversion efficiency. To address the challenge of P removal in solar-grade silicon production, this study proposes a combined process of Si-Fe solvent refining and SiO₂-TiO₂-CaO-CaF₂ slag treatment. Under conditions utilizing collaborative refining with an alloy composition of Si-10 wt. %Fe and a slag composition of 32 wt. %SiO₂-48 wt. %CaO-10 wt. %TiO₂-10 wt. %CaF₂, the removal rate of P in silicon can reach up to 96.8%. This paper investigates the effectiveness of combining solvent refining with slag making under fixed conditions of a Si-10 wt. %Fe alloy paired with various slag systems (no slag addition, binary slag SiO₂-TiO₂, ternary slag SiO₂-CaO-TiO₂, and quaternary slag SiO₂-TiO₂-CaO-CaF₂). Based on the experimental results, the optimal TiO₂ content in the slag system for maximizing P removal was analyzed and determined. Finally, leveraging both theoretical analysis and experimental findings, the mechanism of P removal was elucidated as a dual process: P is oxidized into Ca₃(PO₄)₂ within the slag phase, and residual P is captured by the Fe-Si-Ti ternary phase. Full article

Blast furnace slag, a high-temperature molten by-product generated during the ironmaking process in the metallurgical industry, has garnered significant attention for its resource utilization technologies. Compared to the traditional water-quenching method, dry granulation offers notable advantages. This paper systematically compares and analyzes the performance parameters of three typical dry treatment processes: mechanical crushing, air-quenching granulation, and centrifugal granulation. It reveals that the centrifugal granulation process demonstrates substantial technical superiority in key metrics, such as particle size distribution uniformity, particle morphology optimization, and heat recovery efficiency. Building on this, this study provides a comprehensive review of the current state of centrifugal granulation technology, from both experimental and simulation perspectives. Additionally, the combined processes of centrifugal granulation and air quenching can fully exploit the synergistic benefits of each technology, thereby enhancing overall efficiency. However, the wind’s cooling effect can lead to the premature solidification of molten slag when it splits into liquid filaments, resulting in slag wool. To address this, this paper proposes a centrifugal granulation device equipped with a windbreak board, which facilitates temperature zoning. This approach prevents premature solidification in the liquid filament region while ensuring the timely cooling and solidification of slag particles, offering a novel technical solution for optimizing centrifugal granulation in metallurgical solid waste resource utilization. Full article

The environmental impacts of industrial processes have increased the demand for sustainable alternatives in wastewater treatment. Conventional chemical coagulants, though widely used, can generate toxic residues and pose environmental and health risks. Biocoagulants, derived from natural and renewable sources, offer a biodegradable and eco-friendly alternative. This review explores their potential to replace synthetic coagulants by analyzing their origins, mechanisms of action, and applications. A total of 15 studies published between 2020 and 2025 were analyzed, all focused on industrial wastewater. These studies demonstrated that biocoagulants can achieve similar, or the superior, removal of turbidity (>67%), solids (>83%), and heavy metals in effluents from food, textile, metallurgical, and paper industries. While raw materials are often inexpensive, processing costs may increase production expenses. However, life cycle assessments suggest long-term advantages due to reduced sludge and environmental impact. A textile industry case study showed a 25% sludge reduction and improved biodegradability using a plant-based biocoagulant compared to aluminum sulfate. Transforming this waste into inputs for wastewater treatment not only reduces negative impacts from disposal but also promotes integrated environmental management aligned with circular economy and cleaner production principles. The review concludes that biocoagulants constitute a viable and sustainable alternative for industrial wastewater treatment. Full article

To develop a high-efficiency process for removing phosphorus (P) from metallurgical grade silicon, a novel method of combining Si-Cu solvent refining and CaO-CaF₂-CaCl₂ slag treatment was investigated through simultaneously re-constructing P-containing phases of CaCu₂Si₂ in the Si-Cu alloy and Ca₃P₂ in the slag. After acid leaching, P-containing phases can be eliminated, whereupon high-purity silicon could be recovered from the Si-Cu alloy. The effect of slag components and alloy composition on the P removal efficiency was studied systematically. When the Si-40 wt.% Cu alloy is treated with 20 wt.% CaO-32 wt.% CaF₂-48 wt.% CaCl₂ slag for 60 min at 1400 °C, the P removal efficiency reaches 90.1%. Furthermore, the mechanism of enhanced P removal was also discussed. It was indicated that a silicothermal reduction reaction occurred between CaO and Si, which caused Ca to migrate into the alloy and precipitate the P-containing CaCu₂Si₂ in the Si-Cu alloy. Simultaneously, P in silicon is reduced to P³⁻ at the slag–alloy interface, forming Ca₃P₂ in the slag, thereby establishing a dual-path purification mechanism. Hence, this study provides new insight into silicon high-efficiency purification from economical and practical considerations. Full article

The study examined the influence of ion-plasma nitriding on the structure, mechanical, and tribological properties of high-speed steels AISI M2 and AISI M41. A comprehensive study was conducted on the changes in phase composition, microhardness, and wear resistance of the obtained modified layers. It was established that the optimal approach was the formation of high-nitrogen martensite without excessive nitrides, which ensured improved mechanical properties of the steels. The dependence of the nitrided layer depth and its microhardness on nitriding temperature and duration was investigated. It was found that at a temperature of 480–520 °C and a processing duration of up to 1 h, a hardened layer with a depth of 25–40 μm was formed, exhibiting increased wear resistance and microhardness of up to 10–12 GPa. The analysis of structural transformations confirmed the presence of ε and γ’ phases, which contributed to increased strength and reduced friction coefficient. The obtained results can be used to improve the technological processes of heat treatment for high-speed steels used in the production of cutting tools. The proposed nitriding parameters contribute to extending the service life of steel components, which is relevant for the mechanical engineering and metallurgical industries. Full article

The Fe-36Ni alloy, with ultra-low thermal expansion and stable properties, is essential for aerospace remote sensors and aircraft load-bearing structures, widely used in aerospace. Additive Manufacturing, an emerging rapid prototyping technology with short cycles, high efficiency, and flexibility, addresses complex structural fabrication challenges. While selective laser melting (SLM) enables complex geometry fabrication, post-process treatments (e.g., annealing-induced homogenization, thermal aging for stress relief, surface polishing) remain critical for attaining metallurgical stability in as-built components. The impact of different laser scanning speeds (500 mm/s, 1000 mm/s, 1500 mm/s, 2000 mm/s) on the microstructure and mechanical and thermal expansion properties of the Fe-36Ni alloy fabricated by selective laser melting was studied. The results indicate that all Fe-36Ni alloys predominantly exhibit the γ-phase. Interestingly, a small amount of α precipitates was also observed, which is primarily attributed to the formation of a supercooled region. Notably, at a scanning speed of 1000 mm/s, the Fe-36Ni alloy samples exhibit optimal mechanical properties, with a tensile strength of 439 MPa and an elongation of 49.0%. This improvement is primarily attributed to the enhanced molding quality and grain refinement. The minimum coefficient of thermal expansion occurs at a scanning speed of 2000 mm/s, likely due to the elevated defect density. Full article

This study proposes a synergistic treatment method for BOF slag and copper slag via oxidation–magnetic separation, with the dual goals of preparing MgFe₂O₄ magnetic material and stabilizing the non-magnetic slag. The effects of copper slag addition, the oxidation temperature and the oxidation time on the phase transformation and MgFe₂O₄ morphology during the oxidation process are investigated. The results show that copper slag addition can release the simple iron oxides of FeO and Fe₂O₃ from iron-containing phases from BOF slag and copper slag, promoting the synthesis of MgFe₂O₄. Furthermore, the oxidation temperature and oxidation time have a significant influence on the size of the MgFe₂O₄ particles. To obtain the MgFe₂O₄ magnetic material, the optimum oxidation parameters were used, with an oxidation degree of Fe²⁺ of 95.85% and a yield of MgFe₂O₄ of 90.31%. In addition, the main phase of non-magnetic slag was Ca₂SiO₄, and both free CaO and free MgO from BOF slag were eliminated, indicating a potential application in construction materials. This technology maximizes resource utilization and the valorization of metallurgical solid waste. Full article

This study investigates the synergistic strengthening effects of in situ synthesized nano (ZrB₂ + Al₂O₃) particles and rare earth Er microalloying on the microstructure and mechanical properties of 7085 aluminum alloy. The composite material was prepared through a melt direct reaction combined with rolling and T6 heat treatment, with microstructural evolution characterized by metallurgical microscopy, XRD, and SEM. Results demonstrate that the addition of 3 vol.% in situ nano (ZrB₂ + Al₂O₃) particles optimally enhances both strength and toughness, achieving a tensile strength of 635.4 MPa (16.2% increase) and elongation after fracture of 16.2% (14.9% improvement) compared to the matrix alloy. Excessive particle content (5 vol.%) leads to severe clustering and deteriorated interfacial bonding, causing performance degradation. Introducing 0.3 wt.% Er improves particle distribution uniformity and promotes Al₃(Er,Zr) precipitate formation, refining grains and strengthening interfaces. This further elevates tensile strength to 654.8 MPa (19.7% increase) and elongation to 16.6% (17.7% improvement). The research reveals the synergistic optimization mechanism between particle content and Er addition, providing theoretical support for designing high-performance aluminum matrix composites. Full article

Advancing material efficiency in the steel and cement industry is essential for achieving climate goals. One approach to addressing this is to increase the provisioning of alternative reactive binder materials from residues, in this case, from the steel industry. Different mixtures of identified residues are evaluated for metal recovery and suitability as supplementary cementitious material. For this purpose, suitable combinations are modeled according to specified quality requirements from the cement industry. These mixtures are heated up to 1600 °C for a targeted reduction of predominantly transition metal oxides and a separation into a mineral fraction. Subsequently, controlled cooling of the molten material is implemented through water granulation. The produced granulate is crushed and sieved, and finally, the metallic and mineral fractions are magnetically separated. The chemical modification, reduction, and phase modification are tested to prevent landfilling and provide alternative secondary resources for the steel and cement industry. According to the results, it is possible to recover metals from metallurgical residues and simultaneously separate the modified mineral fraction as an alternative cement constituent. These findings will be further investigated through additional research to identify the variables that influence and impact/affect the reduction efficiency. Full article

Annealing and rolling play critical roles in improving the mechanical properties of arc spraying coatings. In this work, we successfully fabricated copper–steel bimetallic sheets (CSBSs) using an arc spray-rolling short process and achieved excellent internal bonding of the copper coating and improved deep-drawing of the CSBSs via annealing and rolling synergistic treatment. The results indicate that the microstructure of the copper coating became dense, and the porosity effectively reduced after annealing–rolling–annealing (ARA) treatment. Tight bonding was also observed between the copper coating and steel substrate. The copper coating had a porosity of less than 0.2%, an average grain size of 3.8 μm, and a micro-hardness of 55 HV_0.05. After tensile testing, the As-sprayed coating generated brittle fractures and delamination. The A-R-A coating also displayed elongated dimples, with the majority oriented along the TD direction, and bonded well with the steel substrate. In addition, the As-sprayed coating fell off directly after deep drawing. In contrast, the A-R-A coating did not exhibit cracks and fall off. The fracture mechanism gradually changed from falling off and cracking, to toughness deformation due to the reduced porosity and tighter grain boundaries, and finally to cooperative deformation due to the metallurgical bonding of the sprayed particles and good interface bonding properties. These findings provide guidance and reference for the practical application of thermal spray additive manufacturing. Full article

Zinc-based oxides are the main products obtained after the Waelz process, a metallurgical method used industrially for the treatment of electric arc furnaces. These oxides have certain impurities in their composition, which can be a disadvantage. Carbochlorination reduction reactions have proven to be useful in eliminating certain impurities (especially Pb) through thermal treatments. In this work, a method for purifying Waelz oxide through carbochlorination reduction reactions is presented. Several experiments have been conducted with the aim of obtaining samples with potential end applications. A deep characterization of the purified oxides has been performed by means of X-ray microanalysis, X-ray diffraction, Raman spectroscopy, and cathodoluminescence. These measurements indicate the presence of ZnO and ZnFe₂O₄ in different proportions, depending on the different amounts of reducing and chlorinating agents used. Full article

Boehmite is an aluminum oxyhydroxide (AlO(OH)) and one of bauxite’s main mineral phases. This mineral is highly valued as an important source of aluminum for the metallurgical industry. However, the formation of synthetic boehmite has been observed in water treatment when aluminum anodes are used for electrocoagulation. This boehmite occurs in flocs that capture impurities from the water, but removing these flocs is a slow process. Therefore, the froth-flotation method was employed in the present study to float synthetic boehmite. This was achieved by evaluating the particle size of synthetic boehmite, generating microbubbles, and using an anionic collector system in a novel experimental setup. The results show that the surfactants sodium dodecyl sulfate (SDS) and potassium oleate (PO) favor the recovery of synthetic boehmite in different particle sizes, with the particle size favored related to the bubble size generated. It was noted that increasing the SDS concentration enabled the microbubbles to recover up to 95% of boehmite particles with diameters of less than 30 microns. Full article