Gallium is an important rare metal resource. Gallium and its compounds have been found extensive applications in diverse fields, e.g. solar energy, semiconductors, biology, chemical engineering, and alloys. Gallium resources have evolved into a crucial strategic asset owing to the continually increased demand. Gallium is sparsely distributed within minerals like bauxite, apatite, nepheline, and alunite in an extremely scarce quantity. More than 90% of the world's primary gallium is derived from the by-products of alumina production. Currently, methods for recovering gallium from Bayer liquor can be included as precipitation, electrochemistry, extraction, and resin adsorption. However, improving the recovery efficiency of gallium and reducing its recovery cost are remained key concerns in the relevant industry. Recent research findings on the occurrence forms of gallium in bauxite, the migration behavior of gallium during the Bayer process cycle, and methodologies for gallium separation, extraction, and recovery are presented. The current status of gallium resource recovery from bauxite is mainly introduced, the advantages and disadvantages of the employed technologies are summarized, and some future research directions for gallium extraction from bauxite are outlined.

The sintering process constitutes a crucial stage in the blast furnace ironmaking technology, but it also generates significant amounts of pollutants. In the context of ultra-low emissions, steel enterprises urgently need to upgrade and transform their existing desulfurization and denitrification processes to address the problems that exist in their practical applications. Based on the current status of flue gas desulfurization and denitrification technologies in sintering processes of steel enterprises, mainstream desulfurization and denitrification technologies applied in China′s sintering flue gas treatment field are systematically introduced. Meanwhile, an outlook is provided for the removal technologies of sulfur dioxide and nitrogen oxides in sintering flue gas that are widely applied in steel enterprises currently. Selecting mature desulfurization and denitrification processes based on flue gas characteristics will become the main path for the steel industry to complete ultra-low emission transformation. The semi-dry desulfurization technology needs to actively develop technologies for the harmlessness and resource utilization of desulfurization ash, and at the same time apply automation and intelligentization technologies to address the problem of desulfurization efficiency under changing operating conditions.The research focus of SCR denitrification is low-temperature SCR technology, especially the development of low-temperature catalysts with anti-water and anti-sulfur poisoning ability.The simultaneous desulfurization and denitrification process of active coke should be studied more in the aspects of preventing crystallization plugging, system corrosion and standardized operation.

Hydrogen energy, as a critical component of future energy systems, necessitates efficient transportation methods to facilitate global energy transition. Pipeline transportation has emerged as the preferred solution for long-distance hydrogen delivery due to its safety and economic advantages. However, hydrogen embrittlement in pipeline steels remains a primary safety concern, involving multi-scale mechanisms spanning hydrogen atom behavior and dislocation movement that challenge comprehensive characterization. This review summarizes predominant hydrogen embrittlement mechanisms in hydrogen pipelines, including hydrogen-enhanced decohesion, hydrogen-enhanced localized plasticity, and hydrogen adsorption-induced dislocation emission, with emphasis on their synergistic interactions. Key influencing factors of hydrogen embrittlement are discussed in terms of chemical composition, microstructure, precipitated phases, inclusions and segregation. Meanwhile, a multi-dimensional characterization method, ranging from macroscopic mechanical testing to microstructure characterization, is summarized for the cross-scale behavior of hydrogen in the steel of hydrogen transmission pipelines. Addressing energy transition imperatives, enhancing hydrogen embrittlement resistance has become pivotal for scaled hydrogen transportation. Innovative approaches integrating machine learning and cross-scale modeling are introduced for anti-hydrogen embrittlement material design, demonstrating how inverse design strategies accelerate development of high-strength hydrogen embrittlement-resistant pipeline steels. Finally, combined with the current research status of hydrogen pipeline steels, the key points and prospects for future research on hydrogen pipeline steels are summarized.

Foamed slag technology is the core process of ultra-high-power electric furnace steelmaking, which is crucial for enhancing thermal efficiency, protecting furnace lining and optimizing molten steel quality. It takes biomass charcoal as the research object, systematically analyzed its performance and influencing factors as a blowing agent, and compares it with traditional fossil-based blowing agents (coke, graphite, anthracite). Waste wood block charcoal, corn stover charcoal, waste bamboo charcoal and industrial wood charcoal were used in the experiment, combined with chemically formulated electric furnace slag, and their foaming ability was evaluated by high-temperature foaming experiments with comprehensive foaming index (K). The results showed that the waste wood charcoal showed the best overall performance due to its high fixed carbon and low ash. The corn stover charcoal significantly reduced the viscosity of the slag due to its high ash content and high alkali metal content, resulting in the worst foaming area and duration. The waste bamboo charcoal, although with the highest fixed carbon, had a high potassium content in the ash content that exacerbated the deterioration of the foam stability, and had a second best overall performance than that of the waste wood charcoal. Compared with fossil blowing agents, graphite showed the highest maximum foaming area and comprehensive foaming index, but industrial wood charcoal showed substitution potential by virtue of its longer foaming time and low-carbon environmental protection characteristics. The synergistic effects of slag alkalinity, viscosity and surface tension on foaming performance were further revealed. It was pointed out that alkali metals (e.g., K, Na) in the ash fraction of biomass char reduced the viscosity by disrupting the silica-oxygen network, but an excessive amount shortened the foam life. This study meets the development needs of green metallurgy under the "double carbon" strategy, and provides a theoretical basis for the large-scale application of biomass carbon in electric furnace steelmaking.

With the rapid development of China′s industry, higher requirements are put forward for high-speed and heavy-load railway tracks, stable and safe mechanical bearings, efficient and environmentally friendly mining. At the same time, it also leads to a rapid increase in the consumption of materials in the corresponding field in terms of wear failure, resulting in huge economic losses. As an important engineering material, bainite wear-resistant steel can obtain excellent strength, toughness and wear resistance by adding low-cost alloy elements and simple heat treatment process. It has broad application prospects in mining, railway, machinery and other fields. The research results of bainite wear-resistant steel in China are reviewed from the aspects of composition design, heat treatment process and microstructure on wear resistance. It is expected to provide reference for the design, preparation and application of bainitic wear-resistant steel by analyzing and summarizing the research status of various aspects. Finally, combined with the current research results, the development trend of bainite wear-resistant steel and the research direction that needs to be paid attention to in the future are discussed.

Hot-rolled ribbed steel bars constitute the largest proportion of steel consumption in China, with low cost, high strength, multi-functionality, and long life being the trends in their development. Microalloying technology, serving as a primary means of enhancing steel bar properties, is employed by domestic steel enterprises in the production of hot-rolled ribbed steel bars. Numerous studies have shown that the strengthening mechanisms of microalloying elements primarily involve solid solution strengthening and precipitation strengthening of carbonitrides. V, Nb, and Ti are commonly used microalloying elements for strengthening. With the in-depth research on strengthening mechanisms and the upgrading of production equipment, the roles of rare earths in enhancing mechanical properties, corrosion resistance, weldability, and cost reduction have emerged as new directions in the development of seismic steel bars. The current research status of microalloying in seismic steel bars is introduced and reviewed, aiming to provide a reference for the preparation of microalloyed seismic steel bars with superior performance.

With the increase of industrial activities such as aluminum smelting, coal utilization and mining, the production of solid waste such as aluminum ash, cinder and red mud is increasing year by year, which seriously affects the sustainable utilization of ecological environment and resources. This study aims to explore and evaluate the synergistic treatment effect of three industrial waste residues, secondary aluminum ash, cinder and red mud, in the process of high temperature roasting, aiming to realize the resource utilization, harmlessness and by-product of valuable alumina powder. The effects of different roasting temperature, holding time and liquid-solid ratio on the leaching rate of alumina powder were investigated by high temperature roasting experiment, and the three-phase roasting conditions were optimized by orthogonal experiment. The results show that, under the conditions of calcination temperature, holding time and liquid-solid ratio of 1 100 ℃, 40 min and 11∶1, the three solid wastes can effectively promote the formation of alumina, and the recovery rate of alumina in the calcined product can reach 89.88%. If the temperature is too low, harmful substances are difficult to volatilize. If the temperature is too high, liquid phase will appear in the clinker, which will affect the recovery rate of alumina. Under the optimal process conditions, 89.88% of alumina powder can be recovered for every 1 g of secondary aluminum ash, 1 g of cinder and 2 g of red mud consumed. In the whole process, harmful substances volatilize into the waste gas, and silicate phase substances such as MgO, SiO₂ and CaSiO₃ are formed in the leaching residue. This process realizes the transformation of hazardous waste into ordinary solid waste, so as to achieve the purpose of treating waste with waste, which lays a foundation for the resource and reduction of solid waste.

The iron and steel industry is one of the major source of carbon emissions, and advancing pellet technology is one of the effective measures to achieve the "dual-carbon" goals. Excessive reduction swelling of pellets can degrade reactor permeability and even leads to production accidents. This paper systematically reviews the primary mechanisms of reduction swelling in iron ore pellets, including lattice expansion from phase transformations, iron layer cracking due to gas pressure, structural damage induced by carbon deposition, cracking resulting from uneven reduction stresses, and the precipitation morphology of nascent iron. Studies have shown that regulating the formation of iron whiskers is a key breakthrough in inhibiting malignant expansion, while reduction swelling is significantly influenced by preheating/roasting parameters, porosity, gangue composition, and reduction conditions. Key measures to suppress pellet swelling involve optimizing ore blending, rational control of basicity, refining preheating/roasting processes, and restricting harmful element intake. It provides a theoretical foundations and technical pathways for optimizing pellet performance and advancing low-carbon ironmaking technologies.

Under the background of the "dual carbon" era, the EAF mini mill steelmaking process is regarded as an effective carbon reduction technical route. More and more EAF steelmaking capacity has been further expanded in the world. The study on the global layout of EAF steel production capacity reveals that according to the output of EAF steel in major countries, which can be divided into five echelons. The layout of production capacity is affected by six factors, which are trade circulation, energy conditions, economic development, technological innovation, environmental protection policies, and market demand in the world. The analysis of more than 210 existing enterprises with EAF equipment in China shows that nearly 200 enterprises are located on the east side of the "Hu Line". The layout of production capacity mainly presents four characteristics, which are resource supply, energy reliance, green orientation, and group model. There are problems such as weak cost competitiveness of short-process enterprises compared to long-process enterprises in the same region, serious product homogeneity among enterprises in the region, and insufficient green environmental protection advantages. Based on the current status of the layout of EAF steel production capacity in China, four optimization directions for the existing layout are proposed, along with two development trends for future layouts. The layout of EAF steel production capacity is prospected from aspects of location, production capacity and time. It is essential to manage both the existing and incremental EAF steel capacity well to fully utilize the crucial role of EAF steel in the green and low-carbon transformation and development of the steel industry. It is suggested that the development of EAF mini mill steelmaking process should not be decided in isolation. A comprehensive judgment should be made on the strategies for the layout of EAF steel production capacity in different periods.

High strength low alloy (HSLA) steel is widely used in building and bridge construction, oil and gas pipelines, ships, and offshore platforms due to its excellent comprehensive properties and cost advantages. The yield ratio serves as a key indicator in the development and application of HSLA steel. This review first summarizes the yield ratio of single-phase steels, such as ferritic, pearlitic, and martensitic steels, as well as ferrite/austenite multi-phase steels, at different strength levels. In general, steels with higher yield strength exhibit higher yield ratio. The introduction of ferrite or austenite phases in steel is beneficial for reducing the yield ratio. Subsequently, recent advances in the design of multi-phase microstructure and the control of rolling and heat treatment processes for high-strength steels with low yield ratio are discussed. Finally, progress in the use of machine learning and artificial intelligence for assisting the study of mechanical properties of HSLA steels is introduced. Achieving a favorable combination of low yield ratio, high toughness, and high plasticity is a development trend in HSLA steel. Constructing multi-phase, metastable, multi-scale, and multi-morphological microstructures provides an effective approach for developing high-strength, high-toughness, and low yield ratio steels. And the integration of physical metallurgy and data science is becoming a key pathway for precise microstructure design of such steel grades.

Driven by the "dual carbon" strategic objectives, the iron and steel industry, as a major carbon emission sector, underwent technological innovations in low-carbon ironmaking that became crucial pathways for achieving carbon neutrality. This led to the development of several key technologies including fluxed pellet production with large pellet ratio blast furnace operation, composite iron coke, hydrogen-enriched carbon cycling blast furnace, and hydrogen-based shaft furnace short process. The application of fluxed pellets and high pellet ratio in blast furnace optimized the burden structure by partially replacing sinter. Composite iron coke served as highly reactive material that substituted for conventional coke. The core principle of hydrogen-enriched blast furnace technology involved injecting hydrogen or hydrogen-rich reducing gas through tuyeres to replace carbon-based fuels. Hydrogen-based shaft furnace short process emerged as an alternative ironmaking process that utilized hydrogen as reducing agent, demonstrating advantages in efficiency, environmental friendliness and energy conservation. All the aforementioned low-carbon ironmaking processes demonstrated carbon emission reduction potential. A systematic investigation of low-carbon ironmaking technology systems was required, involving both the advancement of traditional blast furnace processes and the development of alternative ironmaking technologies. The selection of appropriate low-carbon technological pathways was projected to contribute significantly to achieving carbon neutrality in China′s steel industry.

Hydrogen embrittlement is a complex phenomenon in materials science and engineering, which can lead to a decrease in the mechanical properties of high-strength age-hardened aluminum alloys and seriously affect the service life of aluminum alloy products. Firstly, the forms of hydrogen entering the material are introduced, including hydrogen absorption introduced during the manufacturing process, hydrogen exposure, hydrogen absorption caused by corrosion, and artificial hydrogen charging. Secondly, the interaction between hydrogen and microstructure is summarized, focusing on the effects of precipitates, dislocations, and grain boundary states on hydrogen embrittlement in alloys with different aging tempers. Finally, the relevant mechanisms of hydrogen embrittlement are discussed, including hydrogen-enhanced decohesion mechanism, hydrogen-enhanced localized plasticity mechanism, adsorption-induced dislocation emission mechanism, and mixed mechanism. Future research work in this field is also prospected, in order to provide a theoretical reference for the design of hydrogen-embrittlement-resistant aluminum alloys and hydrogen storage aluminum alloys.

As the dominant process in the zinc industry, the hydrometallurgical production system generates cobalt-bearing supernatant solution and cobalt residues with considerable resource value during operation. Efficient recovery and utilization of these by-products can promote solid waste resource utilization and alleviate China's shortage of cobalt resources. This paper provides an in-depth analysis of cobalt removal technologies from zinc sulfate leaching solutions, systematically comparing the principles, efficiency, cost effectiveness, and environmental impact of various methods, including zinc dust cementation (activated by arsenic/antimony salts), organic reagent-based cobalt removal, and redox precipitation for cobalt removal. Furthermore, a comprehensive review is conducted on the treatment of cobalt residues through leaching followed by multi-metal ion separation, summarizing the technical advantages and drawbacks of different leaching approaches (selective leaching, acid leaching, alkali leaching, and combined leaching) and separation techniques (oxidation precipitation, chemical precipitation, solvent extraction, ion exchange, and membrane electrolysis). A case study from the zinc smelting plant of Baohui Group is presented to trace the migration and transformation behavior of cobalt throughout the entire process, including oxidative roasting, acid leaching, three-stage purification, and cobalt residue treatment. Zinc hydrometallurgical plants should design suitable technical routes based on process technology, production costs, energy conservation, and environmental sustainability. This entails optimizing leaching and separation parameters, developing novel cobalt removal agents, establishing cobalt-zinc co-production systems, and enhancing the economic benefits of cobalt recovery while ensuring electrolytic zinc quality.