Continuous casting shows an advantage in energy saving, cost and scale in comparison with mold casting, and the continuous casting production of various kinds of low-density high-Al steels with aluminum content from 0.5%-3% or even up to 5%-12% have been implemented or planned in recent years. However, the reaction of high-Al steel with mold flux （i.e. [Al]+（SiO₂）→[Si]+（Al₂O₃） ） can change the composition and properties of mold flux, which prevents the normal functions of lubrication of casting strand and control of heat transfer. As a result, the casting strand surface quality such as depression and crack and the production accidents such as sticking breakout occur frequently, and this is the main bottleneck and limiting step of continuous casting of high-Al steel. In order to improve the surface quality of casting strand and assure the smoothness of continuous casting process, it is the inexorable requirement for the continuous casting of high-Al steel to weaken the change range of flux properties caused by slag-steel reaction. Therefore, lots of attempt and exploration have been taken by the researchers at home and abroad, and different technological ideas and realizing approaches have been put forward. The low basicity and low viscosity mold flux is first proposed to realize the rapid renewal of flux composition. However, the viscosity of flux will increase gradually and the consumption of flux will decrease in the process of reaction. Consequently, it is hard to maintain the relative stability of flux properties, and the industrialization of the continuous casting can be hindered by frequent casting strand surface quality and sticking breakout. Thus, low reactivity and non-reactive flux emerges as the times require, and it becomes a research hotspot in the field of mold flux for high-Al steel. This paper reviews the characteristics and research progress of high basicity and high glassy mold flux, CaO-SiO₂-based high reactivity mold flux, CaO-SiO₂-Al₂O₃-based low reactivity mold flux and CaO-Al₂O₃-based non-reactive mold flux, and the research emphasis and development direction of mold flux for high-Al steel in the future is also put forward.

Under the policy constraints of the national dual carbon goals, the blast furnace converter process will face increasingly severe low-carbon transformation pressure. After hundreds of years of development, the modern blast furnace ironmaking process has been very mature. A reactor better than the blast furnace haven't been found in today's metallurgical industry, whether on thermal efficiency or capacity scale. It is a huge loss to completely abandon the blast furnace process, which is not feasible in the short term. In order to meet the requirements of low-carbon development and extend the vitality of blast furnaces, China Baowu has independently developed a new process called HyCROF （Hydrogen-enriched Carbonic oxide Recycling Oxygenate Furnace）, aiming to achieve significant carbon reduction in ironmaking through carbonic oxide recycling and clean energy substitution. In order to turn technological concepts into reality, China Baowu conducted basic research on four major technical difficulties deep economic removal of CO₂ from the top gas of HyCROF, safe and efficient heating of high reduction potential gas, design of tuyere injection device based on competitive combustion, and reasonable gas distribution under pure oxygen injection and carbonic oxide recycling. Then, an industrial scale HyCROF test platform was constructed through transformation. A large amount of industrial empirical research has continuously conducted on the platform. The results of industrial empirical research show that the new HyCROF process is safe, stable, smooth, efficient, and has strong resistance to fluctuations. It can significantly reduce the proportion of reducing agents. When the coal injection ratio is equivalent, the consumption of solid fuel has decreased by about 30% compared to the baseline period. The main reduction is coke consumption, and the carbon emissions per ton hot metal have decreased by more than 20%. It has good compatibility with traditional manufacturing processes and has certain advantages in manufacturing costs compared to other carbon reduction technologies. Given the excellent experimental results of the HyCROF process, its technology has been applied to a 2 500 m³ blast furnace.

As the leading force in recommending new industrialization, new quality productivity plays an important role in the construction and high-quality development of the country's new economic system. It analyzes the mutual promotion and mutual support between colleges and universities and the development of new productive forces, and emphasizes that colleges and universities and iron and steel enterprises should give full play to their educational advantages in their respective fields. Strengthening personnel training around basic research, engineering technology and other aspects is the key to realize the demand for talents in Chinese modernization. At the same time, starting from the dialectical relationship between accelerating the development of new quality productivity and the high-quality development of the iron and steel industry, it analyzes the value significance of new quality productivity to the high-quality development of the iron and steel industry, which is mainly reflected in the iterative upgrading of the production mode and the optimization and adjustment of the industrial structure of the iron and steel industry driven by innovation, so as to promote the whole industry to jump to the high end of the value chain. It expounds the key links and focus areas of international competition, such as developing new quality productivity to promote the upgrading and development of industry in the direction of intelligence, greenization and high-end, and supporting strategic emerging industries and future industries with new quality productivity. Focusing on the new workers, new labor materials, new labor objects and other factors that constitute new productivity, it focuses on the factor guarantee to promote the high-quality development of the steel industry. Finally, from the perspective of iterative renewal of new production relations, the paper focuses on giving full play to the advantages of the new national system, forming an institutional mechanism that integrates and promotes the integration of promising government, effective market and organic society, and puts forward the institutional guarantee to promote the high-quality development of the iron and steel industry. This paper provides path thinking for new quality productivity to promote high-quality development of other industries.

Energy efficiency improvement is not only an inherent requirement for the transformation and upgrading of the steel industry but also a key driver for its realization of green,low-carbon,and high-quality development. The Ultimate Energy Efficiency Project promoted by the China Iron and Steel Industry Association is an industry-wide project aimed at achieving the ultimate efficiency of iron and steel through the rapid promotion of mature technologies,collaborative research and development of common technical challenges,and the formulation of a series of policies,regulations,and standards. The "Three-Year Action Plan for Energy Efficiency Benchmarks" is an important measure to implement the Ultimate Energy Efficiency Project of iron and steel. The practical progress and implementation performance of this measure are summarized,which also proposes that a data system is essential as the foundation for achieving energy efficiency benchmarking and capacity governance. It takes data system governance as the research objective,and based on the principle of mass-energy balance,proposes a new method for energy consumption data quality diagnosis and a three-layer and multi-level theoretical energy consumption data evaluation mechanism for typical processes. Finally,taking the processes of sintering and blast furnace as examples,it discusses and sorts out the data quality and evaluation mechanism from multiple perspectives such as the boundary division of collected data,the determination of the calculation method for theoretical energy consumption at different stages,the data quality diagnosis of key elements conservation in the process,and the reasonable selection of conversion factors for different energy sources. Utilizing the established the three-layer and multi-level energy consumption calculation model,under the premise of equivalent conversion between heat and standard coal,the theoretical,technical,and actual extreme energy consumption of the sintering process has been obtained. The key parameters affecting the energy consumption of the sintering process have been ranked in terms of sensitivity,with the order from highest to lowest include ratio of leakage air,ratio of water,sinter basicity,return ratio of sinter,ratio of heat loss,lime mass,FeO content of sinter,and MgO content of sinter. Concurrently,the theoretical and actual extreme energy consumption of blast furnace process has also been obtained,providing certain theoretical data support for energy conservation and carbon reduction in the steel industry.

High casting speed is the hot research topic in the field of slab continuous casting with the direct effect on equipment design, manufacturing processes, product quality, cost control and energy saving and consumption reducing. In comparison to the level of high casting speed in abroad, the technical index in domestic plants is still behind. However, some researchers succeeded in exploring high speed slab continuous casting and improved the casting speed to higher than 1.5 m/min, even over 2.0 m/min ranking as the advanced level. High speed slab continuous casting is actually a systematical engineering, with great demand on the supporting technologies to make it run at high efficiency, high safety and high stability. The tailored design and optimization should be carried out including submerged nozzle structure parameters, mold oscillation, mold flux, mold cooling, flow control by electromagnetic field and level fluctuation compensation. The results in previous studies show that the key factors influencing the product quality and safety and stability in high speed continuous casting are the steady flow and heat transfer of liquid steel in the mold, together with the even growth and good lubrication of the shell. Low carbon steel and hyper-peritectic steel are preferentially employed in the trial of high speed continuous casting, and the casting speed of hypo-peritectic steel and high carbon steel is still falling behind, although it increases obviously. The definition of high speed continuous casting is different with the variation of steel grade, strand type, equipments, operation, and technology, and the level of high casting speed is also different in different era. High speed mold metallurgy technologies are the core guarantee for high efficiency slab continuous casting. It is expected that the contents and conclusions of the study can be the theoretical and technological references for the experts and researchers regarding the issue of high speed continuous casting.

The iron and steel industry occupies a crucial position in the process of economic and social development. With the continuous growth of China's iron and steel production, the subsequent treatment problem of steel slag has become increasingly prominent. Due to the problems of poor stability, high abrasion resistance and low cementation of steel slag, the treatment and resource utilization of steel slag are restricted, and a large amount of steel slag is piled up for treatment, which not only occupies land resources, but also harms the surrounding environment and residents' lives. In the context of "green sustainable development" and "carbon neutral", in order to meet the urgent needs of modern steel mills for environmental protection and resource reuse, the development of steel slag treatment and resource utilization technology is imperative. It reviews the research progress of steel slag treatment technologies and resource utilization, and introduces the current mainstream treatment technology of steel slag, including pretreatment process, steel slag modification process and wet treatment process. The technical characteristics of different treatment processes, resource recovery and potential application pathways of products are elaborated in detail, and the technical advantages of different treatment processes are analyzed. In addition, the exploration and research progress of steel slag in the field of environmental remediation are discussed and analyzed, pointing out the application potential of steel slag in this field and the future research direction. The resource utilization of steel slag in China is still facing many problems such as pre-treatment and technological breakthroughs for the expansion of high-quality application areas. The purpose is to analyze the overview of steel slag treatment technology and resource utilization, and to propose that the future research on steel slag, while focusing on the full use of sensible heat and the recovery of valuable resources such as iron, should focus on and strengthen the basic research on the regulation of the evolution of steel slag composition and physical phase. On this basis, new technologies should be developed in the direction of environmental remediation, preparation of new materials and high-value products to expand the high-quality utilization of steel slag and improve the comprehensive utilization rate of steel slag.

As a key link of the steel industry,the ironmaking industry has achieved high levels of energy utilization efficiency. However,in the face of the severe challenges posed by global climate change,achieving large-scale carbon reduction targets still relies on the development and application of a series of breakthrough new technologies. By analyzing the current and future potential low-carbon or near-zero carbon ironmaking processes which include the traditional and hydrogen-rich blast furnace processes,direct reduction processes,smelting reduction processes,and electrolysis ironmaking processes,it was found that the energy characteristics in terms of carbon,hydrogen,and electricity are different for different processes. Based on this,the latest technological advancements and carbon reduction pathways in ironmaking in regions or countries such as China,South Korea,Japan,Europe,and the United States have been summarized and comprehensively discussed. Despite the differing approaches of various countries,the common goal is to increase the proportion of green energy sources replacing fossil fuels. The blast furnace-basic oxygen furnace （BF-BOF） process will continue to dominate steel production in the near to medium term. However,continuing to rely on carbon metallurgy presents significant challenges for CO₂ emissions reduction. Utilizing hydrogen-rich carbon cycle blast furnace technology or other new technologies coupled with green electricity could significantly reduce CO₂ emissions from this process. While the direct reduced iron （DRI）-electric arc furnace （EAF） process is developing rapidly,it also faces challenges related to resources,technology,and costs. Electrolysis ironmaking is also becoming a research focus in Western countries,but large-scale production remains a long way off. Currently,no single method can achieve deep emissions reductions in the steel industry at a low cost. This underscores the need for different countries and regions to determine locally appropriate carbon reduction technology pathways based on their specific resource conditions and circumstances.

The steel industry is one of the major sectors for energy consumption and carbon emissions. Under the global dual carbon background, the heightened awareness of climate change and environmental protection, coupled with the strengthening of carbon tax policies, has intensified the pressure on the steel industry to reduce carbon emissions. Considering factors such as asset preservation and the maturity of technology, the low-carbon technology of blast furnace processes is currently the most direct and effective technical measure to reduce carbon emissions. The main technical routes and development directions of low-carbon metallurgy in blast furnaces both domestically and internationally are introduced, and the demonstration projects of low-carbon ironmaking in China's blast furnaces in recent years are summarized. The author believes that the hydrogen-rich blast furnace process is the preferred direction for process technology improvement at this stage. However, its capacity for carbon emission reduction is limited, only achieving a reduction of 10% to 30% in CO₂ emissions, and it cannot fundamentally solve the problem of high carbon emissions from blast furnaces. In response to this issue, a full-process low-carbon ironmaking technology with upstream carbon reduction of biomass, midstream carbon reduction of hydrogen enrichment, and downstream carbon fixation of CCUS for blast furnaces is proposed, and made an in-depth analysis of the key technologies of each route, and the carbon reduction cost and emission reduction potential of three processes are obtained. It is believed that the full-process low-carbon ironmaking technology will be an important direction for the future development of the steel industry, with high technical feasibility and emission reduction effectiveness. This will promote the steel industry to develop in a more clean and efficient direction, achieving dual carbon goals while maintaining the sustainability of economic development, and prospects for the future of China's low-carbon route in blast furnaces are also discussed.

Blast furnace slag is a typical byproduct in the ironmaking process of blast furnaces, with an emission temperature of up to 1 450-1 550 ℃. It has a large amount of high-grade thermal energy and accounts for nearly 30% of the total energy consumption of the steel industry. Efficient recovery of blast furnace slag waste heat provides a guarantee for the green and high-quality development of the steel industry. Blast furnace slag is currently efficiently treated via dry granulation technology. Scholars have conducted relevant research on the transformation from molten slag to granular slag and waste heat recovery in the granular slag flow process. They have achieved certain results. Through numerical simulation, costs can be reduced, and key links in the waste heat recovery process can be systematically summarized, providing theoretical guidance for practical operations. On this basis, this article systematically elaborates on the current status of physical method treatment for waste heat recovery of blast furnace slag and commonly used numerical methods for simulation of blast furnace slag. It provides a detailed introduction to the research status of multiphase flow and heat transfer characteristics of blast furnace slag in the centrifugal granulation process and heat exchanger. In the centrifugal granulation process, researchers have utilized various models to conduct numerical simulations on the solidification process of slag. This research aims to investigate the impact of particle properties and operating conditions on waste heat recovery, as well as to optimize operating parameters. During the cooling process of the heat exchanger, scholars utilized DEM-CFD simulation to conduct an in-depth investigation into the multiphase flow and heat transfer characteristics of blast furnace slag in fluidized beds, fixed beds, and moving beds. Numerical simulation provides guidance for optimizing waste heat recovery processes, but most studies focus on multiphase flow characteristics of blast furnace slag with limited research on heat transfer and chemical reactions. Moreover, slag particle modeling has certain conditions and ignores deformation and agglomeration. Therefore, finding suitable mathematical models and strengthening research on heat transfer characteristics and chemical reactions to optimize the slag waste heat recovery process and improve recovery efficiency have become the future development direction.

By extracting the frame image of BF tuyeres' video data, and combining with advanced image recognition algorithm to monitor the working state of tuyeres' area, and analyzing the corresponding blast furnace parameter adjustment strategy in real time, which is conducive to reducing the air rest rate and duration, and at the same time making up for the process defects of the response lag and inaccurate results in judging tuyere's state by relying on manual experience at this stage, so as to ensure the long-term stability and smooth movement of blast furnace. Based on the tuyeres' video data of a domestic steel plant between June 1 to June 31, 2023, four common tuyere abnormalities in ironmaking process were sorted out, and main causes and countermeasures based on the principle of ironmaking were analyzed, including hanging slag, slag inflow, coal cutoff and water leakage. Then, the application route of image recognition technology in blast furnace tuyere recognition and monitoring is summarized, including image preprocessing, tuyere identification and early warning, and implantation of expert experience, and the widely used image recognition algorithms are introduced, including convolutional neural network. Transformer mechanism and graph neural network, and the latter two algorithms are affirmed and respected. Finally, based on the graph convolutional neural network, the monitoring and analysis system 1.0 of the blast furnace tuyere is developed, and its functions are briefly introduced. Adhering to the development principle of low latency and high precision, aiming to explore image recognition's application route of blast furnace tuyere in the future by combing the tuyere anomaly and image recognition algorithm, so as to provide a theoretical reference for China's steel enterprises to select reasonable tuyere monitoring technology and improve the intelligent level of tuyere identification and monitoring.

The development characteristics of carbon capture, utilization and storage （CCUS） technology in the iron and steel industry, the construction of the whole-process carbon reduction system and the technological progress are discussed. It describes the carbon emission characteristics of the iron and steel industry, the current status of carbon emission reduction technology development, and the development characteristics of CCUS technology. The iron and steel industry, as an important part of the heavy industry, has a large amount of carbon emission caused by the combustion of fossil fuels, such as coal, in the process of iron and steel production, and although the importance of CCUS has been increasing in recent years in our country, the whole process is still in the early stage of development, and further improvement of technology and policy support is needed. The "6C" system is constructed to create an integrated solution for the whole process of CCUS, detailing the technologies, strategies and application cases of the six links, including carbon capture, utilization, storage, verification, monitoring and assets, and how to achieve the goal of reducing carbon emissions through optimization, and at the same time providing valuable carbon emission control experiences and references for other industrial sectors, control experience and reference. The progress of the application of CCUS technology in typical iron and steel scenarios in the iron and steel industry is analyzed, and three carbon emission reduction paths are proposed, the traditional blast furnace CCUS route carries out CO recycling and CO₂ utilization through the source carbon capture and separation of part of the blast furnace gas, the direct carbon sequestration route in the end flue gas is proposed to reduce the purity of CO₂ at the capture end based on the current problem of high energy consumption and cost of carbon capture, and the hydrogen-metallurgy-coupled CCUS route reduces the CO₂ purity at the capture end by means of hydrogen metallurgy coupled with CCUS route through the combination of renewable energy hydrogen production and CCUS to obtain green methanol. The implementation of the three carbon emission reduction routes will promote the carbon reduction of traditional long processes, reduce the input of carbon sources, combine the utilization of carbon resources with the production process and realize the high value-added utilization of products, and the scaling up of the demonstration projects in the future will realize the internal circulation of CO₂ in the iron and steel industry and its cross-industry utilization, and put forward the suggestions and prospects for the promotion of the development of CCUS technology in the iron and steel industry.

The key factors affecting the fuel rate have long been the subject of debate in the ironmaking community. In fact, both theoretical and practical knowledge of blast furnace operation are required in order to reduce the fuel rate by studying the degree of direct reduction, or the heat consumption per ton of hot metal. This subject has a significant impact on the basic concepts, technical development directions, and production technical guidelines of the blast furnace. For example, in 2020, some people put forward the production principle of "Blast volume as the key link and hot metal temperature as the basis", which results in a high fuel rate. It raises the question of seeking the key factors to determine the fuel rate in the blast furnace operation. The Rist blast furnace operation diagram and evaluation method of blast furnace production is used for the analysis of the data collected from 22 blast furnaces （>4 000 m³）. The outcome of the analysis shows that the heat consumption per ton of hot metal plays a key role in the fuel rate. This means that the amount of combustibles burned and the oxygen consumed in the tuyere zone play a decisive role, rather than the direct reduction degree. In addition, the method of reduction kinetics and evaluation of blast furnace production efficiency is used to analyze a phenomena that the high gas utilization and shaft efficiency of some blast furnaces seem cosxisting with the blast volume and adopt excessive center coke charging operation. It is considered that this is against the law of blast furnace operation.The blast furnace should follow the basic principles generally recognized by the ironmaking industry which insure the high efficiency of the production, high quality of the hot metal, low consumption, long life and environmental protection. Reducing of the fuel rate is essential, along with efficization use of the resources, energy, improving of the efficiency of the blast furnace operation and itse the economic efficiency.

The idea of "hydrogen steelmaking" replaces "oxygen steelmaking" is put forward,and the research status of "hydrogen steelmaking" is summarized and evaluated. Hydrogen metallurgy steelmaking has unique advantages in energy saving,consumption reduction and product quality improvement. On the one hand,hydrogen has a highly efficient melting effect,which can effectively reduce the energy consumption of steelmaking. "Hydrogen" in plasma state has the advantages of high temperature and high thermal conductivity,which can be used as a highly efficient heat source to realize the melting of charge and heating of steel,and has been applied in steelmaking processes such as EAF,converter and tundish. Blowing gaseous "hydrogen" can accelerate the composition and temperature uniformity,and the movement of hydrogen bubbles can be adhered to and accelerate the floating of other non-metallic inclusions. At the same time,hydrogen reacts with oxygen in the liquid steel to release a large amount of heat,which improves the thermodynamic and kinetic conditions of the melt pool reaction. In addition,"hydrogen" can inhibit oxidation and reduce the loss of Cr,Mn and other alloying elements by creating a reducing atmosphere. On the other hand,"hydrogen" has a non-polluting refining effect that significantly improves the cleanliness of the steel. Based on the high activity and high reducibility of "hydrogen","hydrogen" can effectively remove impurity elements such as O,C,N,S and P in steel,especially "hydrogen" in plasma state,which can directly react with the impurity elements to generate H₂O,CH₄,NH₃,H₂S and PH₃ and other gaseous products that are easy to be volatilized and removed,so as to avoid the formation of non-metallic inclusions,and to realize the highly efficient and high-cleanliness steelmaking with "zero inclusions". Therefore,the development of a new generation of green,near-zero carbon, "zero inclusion" and pollution-free steelmaking process using "hydrogen" instead of "carbon" will accelerate the green,high-quality,and sustainable development of the steel industry and support China implement the strategy of "dual-carbon" and "manufacturing power".

Against the backdrop of rapid advancements in the automotive manufacturing industry, there is a mounting demand for higher quality in products such as cold-rolled and galvanized sheets, with the market aspiring for a "zero-defect" quality standard. In the context of continuous casting of high-grade steel for automotive applications, the issue of nozzle clogging and its potential impact on the final product quality has emerged as a pressing concern. It takes ultra-low carbon automotive sheet steel as the subject of study, comprehensively reviewing the progress in both domestic and international technologies for real-time monitoring of mold flow fields and measures to control bias flow, thereby providing theoretical and practical support for the stable production of high-quality automotive sheets. Addressing the challenge of bias flow in the mold during continuous casting, it explores quantitative assessment methodologies, such as calculating nozzle clogging coefficients and symmetry indices （S）, furnishing a scientific basis for predicting and controlling casting slab quality. Moreover, it introduces innovative real-time monitoring techniques, including the use of thermocouples to measure temperature differences and fiber optic sensors for temperature detection, which pave the way for enhanced quality control and process optimization in continuous steel casting. To effectively manage bias flow within the mold, it elaborates on several advanced control technologies, notably electromagnetic control, external electric nozzles, and electromagnetic swirling nozzles. These methodologies, by adjusting the flow distribution of molten steel in the mold, efficiently mitigate flow field asymmetry. Looking ahead, it underscores the broad application prospects of external electric fields in regulating the behavior of inclusions in molten steel and enhancing steel purity. Furthermore, the research highlights the potential significance of exploring the application of external electromagnetic fields in reinforcing the anti-clogging capability of submerged nozzles and optimizing mold flow fields, which hold profound implications for achieving more efficient and higher quality production of automotive-grade steel.

In order to meet the diversified needs of high-strength dual-phase steel users in automobile manufacturers, two kinds of high-strength dual-phase steels with different microstructure characteristics of F/M and B/Ar were obtained, adopting reasonable chemical composition design and process control. The process design principles and microstructure characteristics of F/M and B/Ar high-strength dual-phase steels were studied by means of SEM, TEM, tensile and hole expansion tests, and the influencing factors of mechanical properties were analyzed. The results show that the annealing temperature of F/M dual-phase steel is 810 ℃ in the range of （A_C1+A_C3）/2±8 ℃（A_C1 and A_C3 are the start and end temperatures of austenite transformation during heating, respectively）, which is mainly composed of 47% ferrite, 46% martensite and 7% block retained austenite. The ferrite has two forms of recrystallized ferrite and proeutectoid ferrite, and the grain size is 2.5-4.0 μm and 1.0-2.5 μm, respectively. The annealing temperature of B/Ar dual-phase steel is set to 900 ℃ in the single-phase austenite region. The microstructure is mainly composed of 84% bainite and 16% second-phase retained austenite. The bainite is based on the original γ grain. The phase transformation is formed, and the retained austenite is characterized by lamellar or discontinuous block. There are obvious differences in microstructure morphology between F/M and B/Ar dual-phase steels. The coordinated deformation effects of each phase structure are different during the deformation process, which affects its mechanical properties. The tensile strength can be controlled at the level of 1 000 MPa by both processes. The nano-sized VC precipitated phase particles with a diameter of 4-13 nm are dispersed in the matrix, and the precipitation strengthening amount exceeds 220 MPa, which interacts with high-density dislocations, and finally improves the strength and plasticity of the material. The tensile strength of F/M dual-phase steel is 1 035 MPa, and the elongation after fracture is 18.7%. Compared with F/M dual-phase steel, the tensile strength of B/Ar dual-phase steel increases by 111 MPa to 1 146 MPa, and the product of strength and plasticity reaches 19.83 GPa·%. It has the characteristics of high yield ratio and hole expansion rate, which are 0.709 and 38%, respectively.

At the end of ladle teeming,when the molten steel level is reduced to a certain height,a funnel-shaped confluence vortex will be formed in the ladle due to the interaction of viscosity of molten steel,initial tangential velocity and Coriolis force. Once the vortex penetrates into the pouring nozzle, the slag and air will be involved in the molten steel and pollute the molten steel. Therefore, it is necessary to accurately control the formation and penetration height of the vortex in production, so as to close the pouring gate in time when the vortex is formed. Additionally, by optimizing the process parameters of ladle to delay the generation of vortex, the steel residue in ladle can be reduced and the metal yield increased. There are few studies on the characteristics and influencing factors of vortex at the end of double nozzle ladle teeming. A 150 t industrial double-nozzle ladle in service was used as the prototype. Based on the similarity principle,a 1∶3.5 physical model was established by organic glass. The effects of ladle standing time,initial height of liquid level,nozzle position and structure,bottom blowing stirring and anti-vortex device on the formation process of vortex at the end of pouring were studied by water simulation. The results show that the standing time of molten steel and the initial height of liquid level have no significant effect on the formation height of vortex,while the nozzle position has a great influence on the formation height, and almost no effect on the penetration height. When the eccentricities of two pouring nozzles are 0.60 and 0.83 respectively, the formation height of vortex is the smallest with 17 mm. Compared with a funnel-shaped nozzle,the square-shaped nozzle can reduce the formation height of vortex. In addition,under the present experiment conditions,the bottom blowing stirring operation is not conducive to controlling the vortex,whereas setting an anti-vortex device near the connection line of the two nozzles at a distance of 0.6R （ R refers to the radius of the ladle bottom ） from the center of the ladle bottom will reduce the formation height of vortex,which is conducive to the suppression of vortex.

The characteristics of CO₂ capture and utilization of exhaust gas in iron and steel plants was analyzed systematically. The carbon dioxide utilization technology of exhaust gas was developed in Shougang Jingtang, and the CO₂ captured from the tail gas of lime kiln played a metallurgical role in the combined blowing converter process. The CO₂ concentration of the exhaust gas from the lime kiln increased from 23.5% to 99.8% using the comprehensive method of the pressure swing adsorption and cryogenic separation. Through a series of trials of bottom blowing and top blowing CO₂ in converter, the effect of CO₂ blowing parameters on the w（[C]）×w（[O]）, w（（TFe））of the slag , w（[N]）, the heat change and converter tuyere erosion were researched. The best results for the value of w（[C]）×w（[O]）, slag w（（TFe）） and dephosphorization were achieved when the CO₂ and O₂ mixture was blown at a CO₂ mixing ratio of 8.1%. The [N] content decreased with the extension of CO₂ blowing time. The CO₂ bottom blowing into the converter should be switched with Ar, and the blowing time of CO₂ should be controlled in the early 12 min to avoid increasing the w（[C]）×w（[O]） value and the w（（TFe）） in the slag. The temperature drop is estimated to be 6.4-8.3 ℃/ （m³·t）. The physical heat of molten steel is converted into chemical heat and stored in the BOF gas CO. In order to utilize the cooling effect of bottom blowing CO₂ to protect the bottom blowing tuyere and improve the reaction rate of CO₂ and [C], CO₂ should be blown in the high-speed decarburization period. In order to avoid the erosion of refractory, CO₂ should be avoided at the final stage, for the metal oxides produced by the reaction between the CO₂ and the molten steel result in a faster erosion of the refractory.

In the context of intelligent manufacturing, the defect detection of traditional metallurgical saw blades in enterprises has problems such as insufficient real-time performance, high missed and false detection rate and low accuracy, which is difficult to meet the needs of modern industry. An improved deep transfer learning method for metallurgical saw blade defect detection is proposed. Firstly, by extracting the feature information of the target domain and taking cosine similarity as the evaluation index, the source domain samples with high correlation with the defect dataset are selected from the source domain as the training objects and pre-trained. Then, the conditional parametric convolution（CondConv） module is introduced into the YOLOv7 algorithm, which significantly improves the inference efficiency. At the same time, a high efficiency layer aggregation network（ELAN-CA） is proposed to optimize the spatial information fusion between features, thus enhancing the network performance. Secondly, by introducing a new feature module（AFPN）, the defect information of different sizes is effectively integrated. Finally, based on the improved deep migration detection algorithm and the integration of Mysql database, an online metallurgical saw blade surface defect detection system is developed, which can carry out a variety of real-time defect detection methods, and store and analyze the detection information, which is convenient for real-time statistics of saw blade defect information, and improve the flexibility and adaptability of detection. The improved algorithm improves the detection accuracy of metallurgical saw blade defects to 93%. Compared with the basic network, the number of parameters is reduced by about 46%, and the accuracy and average precision mean are both increased by 5.2%. The improved algorithm can meet the requirements of real-time defect detection in metallurgical production sites, significantly improve the rapid response ability of quality control, and reduce the error and labor cost of manual detection. It provides important technical support for the full automation and intelligence of production line quality inspection.

The presence of residual ferrite in austenitic stainless steel significantly influences its performance. The characteristics of residual ferrite is related to composition, cooling rate, and solidification mode. It focuses on a 316L austenitic stainless steel continuous casting billet, which possesses a high nickel content and is in the eutectic point of composition. Moreover, its solidification mode exhibits susceptibility to alteration. The characteristics and distribution of residual ferrite in the thickness direction of 316L austenitic stainless steel billet were investigated using optical microscopy （OM） and image-pro-plus software. The results reveal that the residual ferrite exhibits a morphology characterized by short rods, granules, skeletal structures, and network formations along the thickness direction. Furthermore, the distribution pattern of ferrite resembles an "M" type distribution which is similar to that observed in slabs. The ferrite content （volume percent） exhibits a fluctuation around 2% from the billet surface to a depth of 55 mm, reaching its highest value （4.77%） at a distance of 65mm from the surface before abruptly decreasing at 75 mm. Subsequently, there is an increase in ferrite content towards the center. Electron probe microanalysis （EPMA） was employed to investigate Cr, Ni, Mo, Si, Mn and other elements, revealing that the secondary austenite formed through solid phase transformation retains certain compositional characteristics inherited from ferrite. The ternary phase diagram of Fe-Cr-Ni and the equilibrium solidification process of the edge and center of the billet were calculated using a thermodynamic calculation software （Thermo-Calc）. The results indicate that FA mode is observed at the edge while AF mode is observed at the center of the billet. Notably, the solidification mode determined by residual ferrite morphology differs from the thermodynamic calculation results. The casting billet solidifies in the AF mode at both the edge and center, while a skeleton-like ferrite forms which indicate the FA mode within the columnar crystal region. Subsequently, an analysis of the formation mechanism for residual ferrite distribution is conducted. The lower content of ferrite observed in the surface fine crystal region can be attributed to the AF mode of solidification on the surface. The ferrite content reaches its maximum value at a distance of 65mm from the billet surface due to a transition in solidification mode from AF to AF+FA. The decrease in ferrite content at 75mm is attributed to the shift back to AF mode during solidification. From 75 mm to the center of the billet, the equiaxed crystal structure and the reduced cooling rate increase the diffusion distance required for solid phase transformation, resulting in an increase in ferrite content.

Blast furnace is the key of energy saving and consumption reduction in global steel production. Ore blending optimization in sintering is the core of reducing cost and consumption in blast furnace. At home and abroad, a lot of work has been done from iron ore characteristics, sinter pot test, and mathematical model. The cost of iron ore normal temperature characteristics is low, which is the most used method in domestic and foreign steel mills. However, it is necessary to consider the influence of iron ore high temperature characteristics when the raw material conditions change greatly. The blending of iron ore through the characteristics can only meet the demand of ore blending in theory. The sinter pot test can verify the theoretical analysis results of iron ore characteristics and raw material technology, to avoid the large deviation of sintered mineral quality in actual production. The deficiency of sinter pot test lies in the high requirement of test equipment and the high cost of time and labor. In order to reduce the test cost and field work intensity, researchers combined theoretical analysis and field production conditions to develop optimization models based on mathematical planning or intelligent algorithm. At present, the ore blending optimization model has little consideration for sintering process and high-temperature metallurgical properties, which limits the potential of cost reduction. The ore blending optimization in sintering is prospected from iron ore characteristics, sinter pot test and optimization model. Collect iron ore powder data and establish an iron ore powder data platform. Develop a dynamic evaluation method for iron ore powder that meets the raw materials and production conditions, reduce testing costs and achieve accurate evaluation of iron ore powder. Based on the iron ore characteristics and production conditions, design sintering pot test plans carefully. Obtain the most effective sintering cup test results with minimal time and labor costs. The focus of ore blending optimization model includes the efficient utilization of sintering process and high-temperature metallurgical properties. Starting from the data and production conditions of iron production, a ore blending optimization model based on historical data such as raw material characteristics, sintering operation, room temperature and high temperature metallurgical performance of sinter, sintering-blast furnace state, etc. is constructed. Ultimately achieving stable sintering ore quality and reducing production costs through ore blending optimization.

In order to explore the influence of limonite ratio change on the morphology and micro-area composition of sinter calcium ferrite, and to clarify the change trend of drum strength performance of sinter when the limonite ratio increases, the FactSage 7.1 thermodynamic simulation software was used to calculate the adhesion powder content and liquid phase formation performance of mixed ore under different limonite ratio conditions. At the same time, the mineralogical characteristics of sinter and the micro-area composition of calcium ferrite were investigated by using the mineral phase microscope combined with OIA automatic mineral phase system and EPMA electron probe according to the different micro-morphological characteristics of calcium ferrite.The results show that the binder phase of sinter is mainly composed of calcium ferrite and silicate. The morphology of calcium ferrite is mainly needle columnar, supplemented by fibrous. The fibrous calcium ferrite is mainly formed in the early stage of the formation of calcium ferrite, which has the characteristics of high content of SiO₂ and low w（Fe₂O₃）/w（CaO）. With the development of the binder phase of calcium ferrite, the content of Fe₂O₃ component increases and w（Fe₂O₃）/w（CaO） increases, which promotes the development and growth of calcium ferrite grains and forms needle columnar.When the proportion of limonite increases from 33% to 50%, the content of adhesion powder decreases by 2.16% due to the increase of 21% of the proportion of coarse-grained LB ore. Thermodynamic theory simulation shows that the amount of liquid phase produced by unit mass adhesion powder decreases by 0.25% and w（Fe₂O₃）/w（CaO） decreases by 0.3, indicating that the increase of limonite ratio is not conducive to the formation and development of calcium ferrite in sinter. The thermodynamic simulation results are consistent with the actual sintering results. The total amount of calcium ferrite in the actual sinter is reduced by 7.75%, of which the content of needle columnar calcium ferrite is reduced by 9.78%. The w（Fe₂O₃）/w（CaO） in needle columnar calcium ferrite is reduced by 0.68, which weakens the development of needle columnar calcium ferrite grains to a certain extent. The morphology of calcium ferrite is mostly fine fibrous calcium ferrite, and the development of calcium ferrite is limited, which eventually leads to the adverse effect on the drum strength of sinter.

To achieve green and low-carbon transformation in the steel industry,China Baowu released a carbon neutral technology roadmap in 2021,with hydrogen metallurgy as one of the six major technological directions and two main technological paths. Due to the fact that current shortage of high-grade iron ore resources required by traditional hydrogen metallurgy,in 2023,China Baowu proposed a hydrogen reduction electric smelting process （HyRESP is Hydrogen Reduction and Electric Smelting Process） with a wider adaptability of iron ore resources,in which the hydrogen-based shaft furnace is one of the core facilities. The differences in reduction rate and low-temperature reduction degradation between lump ore and pellet under hydrogen rich atmosphere were studied. The results show that the reduction speed and low-temperature reduction disintegration index of pellets are better than those of lump ore,but there are significant differences in pellet indicators for different grades. At the same time,the difference in reduction swelling index of pellets under different hydrogen containing gases was studied. The results showed that as the proportion of hydrogen in the reduction gas increased,the reduction swelling index of pellets showed a decreasing trend. When the hydrogen content increased from 55% to 100%,the reduction swelling index of P1 pellets decreased from 16.05% to 9.32%. Based on the hydrogen reduction performance of the five furnace materials mentioned above,and comparing with the relevant standards of direct reduction shaft furnaces,only P3 pellets can be used 100%,while the other four require ore blending,gas composition adjustment,etc. to meet the requirements of vertical furnaces.The research results provide basic data for the commissioning and production adjustment of the one-million-ton hydrogen-based shaft furnace in Zhanjiang.

Impact absorbing energy is an important feature in evaluating the service performance of H11 die steel. Aiming at the phenomenon of large fluctuation of impact absorbing energy of H11 die steel produced by a domestic iron and steel company,combined with microstructure characterization,nonmetallic inclusion characterization and comparative analysis and thermodynamic theoretical calculation, the main reasons leading to the fluctuation of impact absorbing energy of H11 die steel and the transformation mechanism of Ca to MgO·Al₂O₃ inclusions were explored. The results showed that the large size of Ds inclusions was the main factor leading to the low and fluctuating impact absorbing energy of H11 die steel （the average value of unnotched impact absorbing energy at room temperature decreased from （327±3.4） J to （233±26.1） J）. It was determined that the Ca content in steel was the main reason cause of the exceeding of D/Ds inclusions. Combined with the calculation results of commercial thermodynamic software FactSage 8.2,it can be seen that when the Ca in the experimental steel is low （<0.000 5%）,the inclusions in the H11 die steel are dominated by high melting point MgO·Al₂O₃ inclusions,which are difficult to polymerize and grow. However,when the Ca in the experimental steel is high （0.000 9%）,the inclusions in the steel are dominated by low melting point CaO-MgO-Al₂O₃ inclusions,which are easy to polymerize and grow due to the modifying effect of Ca on MgO·Al₂O₃inclusions.Furthermore,it is difficult to remove the inclusions from the molten steel,which leads to excessive Ds inclusions in H11 die steel. It was found that under impact loading,large-size inclusions （>10 μm） would first debonding from the matrix and produce microcracks,and the local concentration of internal stress around the micropores would lead to crack initiation and crack propagation,thus reducing the impact absorbing energy of the experimental steel. Finally,it is proposed that reducing the Ca content by optimizing the smelting process is the main research direction to solve the problem of large size inclusions exceed in H11 die steel.

The process of global response to climate change is further accelerating, carbon themed trade rules and supply chain carbon neutral requirements continue to improve, green and low carbon development has become the high point of strategic competition in the global iron and steel industry. At the same time, the domestic requirements for the development of the new quality productive forces put forward, and further enriched the connotation of the green, low carbon and high-quality development of the iron and steel industry in the new era. On this basis, China's iron and steel industry low-carbon development practice from five aspects has been summarized, including industry top-level design, EPD platform construction, low-carbon emission steel standard formulation, extreme energy efficiency project promotion, and low-carbon frontier technology research and development promotion, and has analyzed the historical process of carbon emission in China's iron and steel industry from 1991 to 2022. The results show that China's iron and steel industry has achieved significant carbon reduction during the past 30 years. Through the analysis of the low-carbon development roadmap, it is believed that China's iron and steel industry has entered the platform of peak carbon emissions around 2010 and will continue to 2030, and has begun to step into a new era of green and low-carbon development. In the future, if all kinds of carbon reduction measures are reasonably adopted, the steel industry CO₂ emissions will steadily decrease, and it will be about 100 Mt in 2060, and further rely on CCUS and carbon sinks to achieve "carbon neutrality". In the process of implementing the "dual carbon" work in China's iron and steel industry in the future has been pointed out, the key issues such as capacity management and industrial layout, the development of all-scrap electric furnace process, the utilization of new energy, the research and development of subversive low-carbon technology, and the basic capacity building of carbon management are worthy of great attention. These issues are discussed and analyzed, and corresponding solution measures and policy construction are proposed.

The zero reforming of coke oven gas and direct reduced process is of great significance for the green transformation of steel enterprises, with significant energy-saving and emission reduction effects. Due to the high composition of φ（H₂）/φ（CO） and a certain amount of CH₄ in the reduction gas of this process, the reduction atmosphere conditions of this process were simulated, and the effects of different conditions on the metallurgical properties indicators such as reducibility, compressive strength, reduction swelling index, and whole ball index during the reduction process of pellets were explored. This is of great significance for the smooth operation and energy conservation of this process. The results indicate that, as the reaction temperature increases, the reduction degree, carbon content, and swelling index increase, while the compressive strength and whole ball index decrease. After the reduction temperature increased from 850 ℃ to 950 ℃, the increase in carbon content leads to severe expansion and fragmentation of the pellets in the later stage of the reduction reaction, and the reduction degree corresponding to the maximum swelling index changes from 40%-50% to about 60%. After replacing CO with an equal amount of H₂, in the early stage of the reaction, due to the increase in reduction rate, the swelling index gradually increases, while the compressive strength and whole ball index decrease. In the later stage of the reaction, due to the inhibitory effect of H₂ on the growth of iron whiskers and carbon deposition, the swelling index of the pellets decreases, while the compressive strength and the whole ball index increases. By using equal amounts of N₂ to replace CH₄, the reduction degree, carbon content, and swelling index of the pellets decrease, while the compressive strength and whole ball index increase. After the reduction degree of the pellets exceeds 40%, the range of changes in various metallurgical properties with the change of φ（CH₄） gradually increases. When the reduction time of pellets under various conditions is 20-40 min and the reduction degree is 60%-80%, the corresponding changes in metallurgical properties reach their extreme values. During the production process, attention should be paid to the indicators of pellets in this area. The carbon evolution process of CH₄ has a certain deteriorating effect on the metallurgical properties of pellets, and φ（CH₄） in the vertical furnace should be controlled.

Electroslag remelting is a method to purify molten steel, using the resistance heat generated by the current passing through the slag as a heat source for smelting. The products prepared by electroslag remelting have the advantages of high purity, dense structure, uniform composition, and smooth surface, so electroslag remelting is widely used in the preparation of high-end metal materials. To ensure the conductivity of the slag, the electric slag system contains a certain amount of CaF₂, which causes severe volatilization during the smelting process and pollutes the environment. The volatilization of fluoride causes significant fluctuations in slag composition, which affects the smelting process and product quality. From the aspects of slag composition, smelting environment, thermodynamics and kinetics, the factors affecting the volatilization of fluoride and the effective methods to reduce the volatilization of fluoride in the slag system are discussed. The effects of CaF₂, w（（CaO））/w（（SiO₂）） and w（（CaO））/w（（Al₂O₃）） on the volatilization of slag system are introduced. Reducing the content of CaF₂, increasing the w（（CaO））/w（（SiO₂）） and decreasing the w（（CaO））/w（（Al₂O₃）） in the slag would effectively reduce the volatilization of fluoride in the slag. And the possibility of using alkali metal oxides （Li₂O, Na₂O, K₂O）, TiO₂ and B₂O₃ instead of CaF₂ to develop low fluorine slag is discussed. One of the important directions for future development of low fluorine/non fluorine slag is to replace CaF₂ with Na₂O, TiO₂, B₂O₃, etc. The effects of smelting temperature and environmental humidity on the volatilization of fluorine-containing slag are reviewed. Reducing the smelting temperature, increasing the heating rate, premelting the slag system and maintaining dryness could effectively inhibit the volatilization of fluoride. On the basis of investigating the current research status of volatilization thermodynamics and kinetics of electric slag system, the applicability of the slag molecular ion coexistence theory to calculate the activity of slag system components is introduced, the kinetic mechanism of slag system volatilization is summarized, and the kinetic limiting links of fluorine containing slag volatilization in electric slag remelting process are summarized. The molecular ion model has high accuracy in calculating the activity of common slag system components, and its applicability to other special slag systems still needs further verification. Future research on volatilization kinetics of slag systems should focus on the mass transfer process of anions and cations participating in volatilization reactions from the main body to the reaction interface, as well as the nucleation, growth, and bubbling processes of reaction products, in order to reduce fluoride volatilization.

In non-oriented silicon steel, fine inclusions and precipitates can seriously deteriorate the iron loss and magnetic induction strength of material. The inclusions in the whole production process of a high-grade, non-oriented silicon steel 23W1700 which was produced by a steelmaking plant was studied. The morphology, size and type of inclusions were analyzed by scanning electron microscope and energy dispersive spectrometer analysis and the precipitates in the casting process was calculated. The results show that in the production process of non-oriented silicon steel, after adding aluminum in Ruhrstahl Heraeus （RH） Vacuum refining treatment, the primary inclusions are AlN, with a small amount of Al₂O₃ and its composite inclusions. After adding rare earth alloy to RH, the inclusions will transform into ReS inclusions and some of them are wrapped by AlN inclusion. After adding desulfurizer, the primary inclusions are small-sized Re₂O₂S wrapped by AlN composite inclusions. In tundish, the inclusions are Re₂O₂S or ReAlO₃ as the core and wrapped by AlN composite inclusions. In slab, spherical MgS was found and Re₂O₂S or ReAlO₃ cored inclusions with the same composition as in the tundish were also found. And the composition of two types of inclusions is slight different in tundish and slab. Throughout the entire smelting process, as the content of rare earth in liquid steel decreases, the trend of changes in rare earth inclusions is ReS→Re₂O₂S→ReAlO_3. The average size of inclusions mainly ranges from 2 μm to 4 μm, the inclusion size is the smallest before adding rare earth to RH, and the inclusion size increases slightly after adding rare earth to RH. After the completion of RH treatment, the inclusion size tends to stabilize, and ultimately the inclusion average size in the slab is 2.9 μm. Using the calculation software Thermo-calc, the precipitation of inclusions in molten steel was calculated. The thermodynamic calculation results showed that when the molten steel was not solidified, the primary inclusions were Al₂O₃. After all the molten steel solidified, Ce₂O₂S, Ce₂S₃, AlN, and MnS would precipitate in sequence, which is also consistent with the types of inclusions obtained in the experiment.

The high-quality utilization of scrap steel is an important way for China's iron and steel industry to achieve green and low-carbon development, as well as "carbon peak" and "carbon neutrality". It analyzes the current situation of scrap utilization worldwide, as well as the problems in scrap utilization in China's steel industry; the dynamic material flow analysis method was used to predict the changes in scrap steel resources and steel social stock under China's carbon neutrality target. The results showed that by 2030, when China is expected to achieve an overall carbon peak, the steel social stock is expected to reach more than 15 billion tons. Subsequently, due to the gradual decrease in steel demand and the stable development of downstream industries, the growth rate of steel storage will also slow down. After 2040, China's steel social stock will be maintained at around 20 billion tons, and the per capita steel stock will be on par with developed countries such as Europe and America. With the continuous increase in the accumulation of steel in society, the problem of insufficient scrap steel resources will be alleviated in the future. Before 2040, China's scrap steel resources will enter a period of stable development. After 2050, due to the trend of stable social development and the gradual decrease in steel demand, the scrap steel resources will also show a downward trend; from the perspective of the utilization of scrap in the blast furnace converter process and electric furnace process, it analyzes the changes in China's steel production process and the impact of scrap utilization on energy conservation and carbon reduction in the steel industry. The results showed that increasing the proportion of scrap utilization can significantly reduce the comprehensive energy consumption and carbon dioxide emissions per ton of steel, whether in long or short processes; it is pointed out that promoting the high-quality utilization of scrap steel resources should start from improving and perfecting the scrap steel recycling and utilization system, improving the classification and pretreatment capacity of scrap steel, expanding the use scenarios to improve scrap steel utilization, promoting tax incentives, and other aspects, in order to improve the efficiency of scrap steel resource recycling and help achieve carbon neutrality goals.

304 stainless steel is commonly deoxidized using ferrosilicon alloy in industrial practices. However, this ferrosilicon alloy often contains a certain amount of aluminum, leading to an increase in the Al₂O₃ content in inclusions and promoting the formation of spinel inclusions. In actual processes, calcium treatment is often carried out after deoxidation. Therefore, the influence of calcium treatment on rare earth elements needs to be considered during rare earth treatment. Industrial production experiments were conducted, and various techniques such as systematic sampling, SEM-EDS detection, and thermodynamic calculations were employed to investigate the effects of rare earth treatment, calcium treatment, and the combined calcium and rare earth treatment processes on inclusions in 304 stainless steel. A comparison was made with the process without alloying. Thermodynamic calculations were specifically analyzed to understand the impact of different calcium contents on the formation of rare earth inclusions Ce₂O₃ and Ce₂O₂S. The study findings demonstrate that under untreated conditions, rare earth （RE） treatment conditions, calcium （Ca） treatment conditions, and Ca treatment followed by RE treatment conditions, the typical inclusions in freshly refined steel are identified as Al₂O₃-SiO₂-MnO（+MnS）, （Ce,La）₂O₂S+（Ce,La）₂O₃-Al₂O₃-SiO₂, Al₂O₃-SiO₂-CaO, and （Ce,La）₂O₂S+（Ce, La）₂O₃-Al₂O₃-SiO₂-CaO type inclusions, respectively. In continuous casting slab, typical inclusions comprise Al₂O₃-SiO₂-CaO-MnO（+MnS） and MgO·Al₂O₃, （Ce,La）₂O₂S+（Al₂O₃）-SiO₂-（Ce,La）₂O₃, Al₂O₃-SiO₂-CaO-MgO（+MnS）, and （Ce,La）₂O₂S+Al₂O₃-SiO₂-CaO-（Ce,La）₂O₃ type inclusions. Following refinement, RE treatment significantly augments the density of inclusions, with minor impacts on the mean size of inclusions. In comparison to Ca treatment, Ca treatment followed by RE treatment marginally increases inclusion density with insignificant alterations in mean size. The size of inclusions post RE treatment predominantly inherits the parent inclusion size. From refinement to continuous casting billets, the inclusion density in Heats 1,Heats 2,Heats 3,Heats 4 decreases by 53.8%, 56.7%, 52.0%, and 31.1%, respectively, while the mean inclusion diameter increases by 29.3%, 23.3%, 56.1%, and 43.3%, respectively. Ca treatment exerts a notable influence on inclusion size. Both Ca treatment and RE treatment effectively diminish Al₂O₃ content in inclusions and forestall MgO·Al₂O₃ formation. Thermodynamic computations reveal that an escalation in Ca content suppresses the formation of Ce₂O₃ in RE inclusions within the steel melt, while the impact on Ce₂O₂S formation is minimal.

The iron and steel industry is a major energy consumer and carbon emitter in China. Developing electric arc furnace（EAF） steelmaking process is an important path to achieve carbon peaking and carbon neutrality goals. Improving the EAF production efficiency is important for the developing of iron and steel industry. The technical bottleneck of low carbon,high efficiency and intelligent EAF steelmaking technologies are discussed,the development status of relevant technologies,the research progress of Baosteel Zhanjiang Steel zero carbon demonstration line and Baosteel EAF process to produce high-quality steel are introduced,and the future development direction of EAF steelmaking process is prospected. At present,production efficiency of EAF is increased by improving energy input,promoting chemical reactions,reducing energy and material consumption,carrying out solid waste recycling,and improving intelligence level. However,there are also a series of problems such as steel peroxide,ineffective removal of residual elements,low energy efficiency,lack of online detection and control methods,and unclear metallurgical reaction mechanisms. In the future,with the diversification of raw materials and the scaling up of EAF,the importance of improving energy efficiency,enhancing the stirring of the molten pool,improving the reactivity and foaming of slag and other technologies should be further emphasized. The optimization of related supporting equipment and the classification of scrap need to be further promoted. Replace manual operation and empirical judgment by advanced detection technologies and control models,can also help to improve production efficiency of EAF. Promoting the progress of related work and achieving efficient and low consumption production of high-quality steel in EAF is the only way for the iron and steel industry to transform and develop towards the future.

Applying a large reduction amount of ≥20 mm to a single point of high temperature casting billet in the secondary cooling zone of continuous casting is an important technical means to solve the internal defects such as loose center of casting billet and improve the performance of steel plate, and it is also a hot field of continuous casting technology research in recent years. To implement the function of large reduction, the casting roll with large roll diameter is required. The rolling contact with the slab in the secondary cooling zone is continuous, high temperature and low speed, and the service environment is harsh. The cooling mode of the casting roll is the key factor affecting the effect of large reduction, the life of the roll and the surface quality of the casting slab. ABAQUS finite element software was used to build a two-dimensional heat transfer model of casting roll, and the overall temperature variation rule of casting roll surface and inside under three cooling methods of "double-sided water spraying", "single-side water spraying" and "single-side water spraying twice" was simulated. Under the two cooling methods of "double-sided water spraying" and single-side spraying twice water ", the proportion of the inner temperature of the casting roll ≤100 ℃ within a rolling cycle is equal, that is, the cooling effect of the roll is equivalent, which can ensure that the entire casting roll works at low temperature most of the time, and can improve the life of the roll. In the industrial experiment, the cooling water of the "double water spray" cooling method will drop a large amount of water on the surface of the casting billet before high pressure, and the local temperature will drop rapidly into the high temperature and low plasticity zone, which is easy to cause surface cracks after the implementation of high pressure. Therefore, the cooling method of "single side spraying twice water" is used in the actual production, which solves the problem of cooling water dripping on the surface of the casting billet before large pressure, and has high service life of the casting roll and no crack rate of the casting billet. It provides a good idea for the design of the cooling mode of thelarge roll diameter casting roll, and lays a foundation for the development and application of the slab heavy pressing technology in the secondary cooling zone.

Calcium treatment is employed to enhance the castability of aluminum-deoxidized DZ2 high-speed railway axle steel during continuous casting. Through the introduction of varied Ca content into steel, scanning electron microscopy （SEM） and energy dispersive spectrometry （EDS） are employed to scrutinize and count the morphologies, types, and sizes of inclusions in the smelting procedure and continuous casting billet. This endeavor aims to investigate the evolution patterns of inclusions and the effect of Ca content on the inclusions. Research indicates that the evolution patterns of inclusions during the smelting process exhibit a general similarity between low calcium feeding Steel A and high calcium feeding Steel B. From LF end to the tundish, the inclusions undergo a progressive transformation from Al₂O₃-CaO-MgO with diminished CaO content to compositions characterized by elevated CaO content, specifically CaO-Al₂O₃-MgO. Nonetheless, a notable emergence of CaO persists in the inclusions within the tundish of B. In the continuous casting billet of Steel A, the inclusions are mainly small-sized, low-CaO-content Al₂O₃-CaO-MgO formed during the cooling and solidification process of the molten steel. The large-sized （>10 μm） CaO-Al₂O₃-MgO inclusions, characterized by elevated CaO content, are present in only modest quantities. In the continuous casting slab of Steel B, the prevailing inclusions primarily consist of CaO induced by calcium treatment, exhibiting a larger size. The difference in the type and size of inclusions in the continuous cast slabs of Steel A and Steel B is intricately tied to the Ca content in the steel. Only a rational Ca content has the capacity to modify Al₂O₃ inclusions into purely liquid states. Excessive Ca content, however, leads to the emergence of solid inclusions, such as CaO and CaS. The calculation results from FactSage thermodynamic software reveal that the optimal Ca content for DZ2 axle steel, following calcium treatment, falls within the range of 0.000 5% to 0.001 8%. Prudent application of calcium treatment is imperative to secure the castability of molten steel. Furthermore, it is essential to optimize the metallurgical processes to eliminate large-sized liquid CaO-Al₂O₃-MgO inclusions formed after calcium treatment and during other refining stages.

Iron and steel industry is a typical intensively consuming-energy and CO₂ emission industry. China's iron and steel industry has grown rapidly in recent decades, with China now the world's largest producer and consumer of iron and steel. Compared with iron sintering, pelleting process is more friendly environmentally with lower energy consumption and less co₂ emissions. Development of direct reduction iron-making processes is important initiatives under the Background of Carbon Emission Peak and Carbon Neutrality. High grade hematite as the research object is taken to study the effect of basicity, blue charcoal dosage, binder type and dosage, thermal engineering system, etc. on the quality of green pellets and fired pellets with pure hematite concentrates by travel grate process. The experiment results show that compared to bentonite and Polyacrylamide （PAM）, F-binder is superior to improve the quality of pellets, with high grade hematite as raw material. The fired pellets prepared from high grade hematite's compressive strength beyond 2 500 N/P with natural basicity and F binder, while the fired pellets prepared with bentonite and PAM require a basicity greater than 0.3 to meet the production standard. Whether F binder, bentonite or PAM as binder for the production of high grade hematite pellets, the firing performance and compressive strength of fired pellets can be improved by increasing the basicity. In a certain range, the firing properties of the pellets prepared from high grade hematite can be improved by adding blue charoal. The fired pellets prepared form high grade hematite and with PAM as binder, under the optimal conditions, it can be revealed that iron grade of the fired pellets is as high as 68.22%, and the mass percent of （SiO₂+Al₂O₃） is blow 2%, and the compressive strength is over 2 500 N/P, and possess satisfactory metallurgical performance, which can meet the requirement of gas-based direct reduction process.

The high charging proportion of pellet in blast furnace enhances the ferrous content grade of burden, leading to a reduction in both slag volume and fuel consumption. The emission of CO₂ and other pollutants, such as SO₂, NO_x, and dioxins during the ironmaking process can be reduced, thereby contributing to green and low-carbon ironmaking. Given that the temperature and concentration of the reducing gas vary dynamically as the pellet moves downward in the lump zone of the blast furnace, an exploration of the pellet's reduction process, based on the conditions of the blast furnace's lump zone, is instrumental in understanding and controlling the reduction behavior of the pellet. This, in turn, facilitates efficient and low-carbon operation of the blast furnace. The pellet reduction process in a high-temperature reduction furnace, simulating the working conditions of the lump zone in the Jingtang blast furnace was studied. A comparative analysis was conducted between the actual working conditions and the national standard experimental conditions. The influence of residence time of pellet on the reduction was also discussed. Under the simulated conditions of the blast furnace lump zone, the degree of reduction of the pellet escalates as it descends within the blast furnace. Both the pellet reduction expansion index and the reduction degradation index show a progressive increase. However, when the temperature reaches between 800 ℃ and 1 000 ℃, the formation of a reduced iron shell layer on the pellet surface enhances its consolidation strength, leading to a sudden drop in the reduction degradation index. Under the simulated conditions of the Jingtang blast furnace's lump zone, the actual degree of reduction is lower than that under the national standard experimental conditions. The duration of the burden's stay in the burden zone is directly related to the extent of reduction loss and the degree of reduction, but it has minimal impact on the pellet ore reduction expansion index. This study elucidates the reduction process of pellet ore within a blast furnace, offering valuable insights. Furthermore, it establishes a theoretical framework for enhancing the reduction degree of pellet ore in the lump zone, thereby contributing to a decrease in solid fuel consumption in blast furnaces with a high pellet ratio.

Electric Arc Furnace（EAF） steelmaking has the characteristics of short process,low energy consumption and carbon emissions,and is an important driving force for the world's steel industry to achieve sustainable development. CISDI has conducted a series of research on electric furnace process theory,core equipment,intelligent control,and other aspects. Through technical research and development and pilot experiments, multiple green and efficient electric furnace steelmaking technologies have been developed, which focus on high efficiency,low-carbon,low energy consumption,and environmental friendliness. Among them,the high-efficiency scrap steel transportation technology can achieve an average scrap steel transportation speed of over 7 m/min;step rolling scrap preheating technology,increasing the preheating temperature of scrap by 70-100 ℃;IGBT flexible DC power supply,the power factor of the electric furnace can reach 0.97 or above;short network design optimization system to control three-phase impedance imbalance within 3%;intelligent electrode adjustment technology,with current fluctuations of less than 33% and 14% during the drilling and melting periods,respectively;the dioxin treatment technology can control the concentration of dioxin emissions from arc furnace flue gas to within 0.1 ng/m³; Efficient waste heat recovery system,with a steam recovery capacity of over 160 kg per ton of steel. Intelligent auxiliary equipments have been independently designed,such as automatic sand filling at the tapping hole,automatic cleaning of the furnace door,and automatic temperature measurement and sampling robots,which improved the intrinsic safety level of the enterprise. Engineering practice has proven that using CISDI's green EAF technology,the tap to tap time is 30 minutes and the power consumption is 300 kW·h per liquid steel,which helps to promote the green development of the steel industry. At the same time,the future development of electric arc furnace steelmaking technology is discussed,with the consumption of low-grade DRI as the main process route for the future development of electric arc furnace steelmaking,the production of high-quality steel as the most important research direction for the development of electric arc furnace steelmaking,and the use of digital smelting as the most effective means of electric arc furnace steelmaking production,contributing to the low-carbon transformation of the steel industry.

The high proportion of pellets in blast furnace smelting technology is an important solution to reduce carbon emissions and environmental pressures in the ironmaking system. Utilizing high-silicon ultrafine magnetite concentrate as raw material for pellet production helps expand domestic iron ore resources in China and increase the application of low-grade ores. The influence of basicity on the pelletization and reduction characteristics of high-silicon ultrafine magnetite concentrate pellets was systematically studied. Thermodynamic calculations, mineral phase analysis, scanning electron microscopy-energy dispersive spectroscopy （SEM-EDS）, and other methods were used to investigate their pelletization behavior and reduction characteristics. The research results show that with the increase of basicity, the compressive strength of high-silicon ultrafine magnetite concentrate pellets first increases and then decreases, while the porosity first decreases and then increases. Within the basicity range of 0.06 to 0.73, the compressive strength of the pellets exceeds 4 000 N/pellet. The highest compressive strength and lowest porosity of the pellets are achieved at an basicity of 0.24. Increasing basicity reduces the content of silica dioxide phase in the high-silicon ultrafine magnetite concentrate pellets and promotes the formation of calcium iron phase and silicate phase. Under the conditions of basicity of 1.20 and temperature of 1 300 ℃, the liquid phase proportion in the pellets can reach 24.38%. When the basicity is greater than 0.73, the amount of liquid phase in the pellets rapidly increases after 1 250 ℃. With increasing basicity, the calcium content in the slag phase and silicate phase of the high-silicon ultrafine magnetite concentrate pellets gradually increases. Additionally, higher basicity leads to a more polygonal structure of hematite grains and more filling of slag phase between grains. With increasing basicity, the reduction degree and reduction swelling rate of the high-silicon ultrafine magnetite concentrate pellets first decrease and then increase, and the anti-reduction pulverization performance of the pellets weakens. After an basicity of 0.24, the increased porosity and calcium iron phase content in the pellets facilitate the diffusion of reducing gases inside the pellets and promote reduction reactions, effectively improving the reduction degree of the pellets. The reduction degree of the pellets at an basicity of 1.20 is 34.9% higher than at an basicity of 0.06.

The energy consumption and emissions of the blast furnace ironmaking account for over 70% of the total energy consumption and emissions of the entire steelmaking process. Consequently, it has a great potential to reduce energy consumption and emissions of the blast furnace process. It is shown that hydrogen injection in blast furnace tuyere have promising benefits in low-carbon ironmaking. A prediction mathematical model of blast furnace with hydrogen-injected at tuyeres is established based on material balance, heat balance and the machine-learning dynamic model of indirect reduction degree. The mathematical model was applied to study the impact of hydrogen injection on the blast furnace indices such as fuel ratio, theoretical combustion temperature, direct reduction degree, blast volume, bosh gas volume, carbon consumption, and so on. The rationality and reliability of the model were validated using the actual industrial data of hydrogen-injected blast furnace of Jinnan Ironmaking Plant, and the relative errors of fuel ratio and gas utilization rate are controlled within 3%. Taking the oxygen content of the blast furnace and the amount of hydrogen injection as the main factors, the campaign behavior of blast furnace with single factor variation and two factors co-variation were studied and predicted. When just the oxygen content of the blast furnace is increased, the fuel ratio and theoretical combustion temperature of the blast furnace increase, while the direct reduction degree, blast volume and the bosh gas volume fall. Only when the hydrogen injection rate was increased did the fuel ratio, theoretical combustion temperature, and direct reduction degree of the blast furnace decrease, the blast volume decreases and the speed slows down, and the bosh gas volume declined first and then marginally increased. When the two factors are adjusted cooperatively, the theoretical combustion temperature can be controlled within （2 142±2） ℃ by increasing the hydrogen injection by 10 m³/t while simultaneously increasing the blast oxygen content by 0.43%. Finally, the carbon consumption could be reduced. By combining the traditional blast furnace mathematical model with machine-learning optimization algorithm, the industrial tests of hydrogen-enriched blast furnace could be cost-saving and optimized, and the theoretical guidance for the stable operation and prediction is realized.

In the context of "carbon peaking and carbon neutrality", blast furnace （BF） ironmaking is an important link in achieving the "carbon peaking and carbon neutrality" goal in the steel industry. Iron coke is a new material that can achieve low-carbon smelting in BF. The impact of iron coke on the softening-melting-dropping performance of the BF mixed burdens is crucial for the application of iron coke in low-carbon BF smelting. The softening-melting-dropping properties evolution of BF mixed burdens under different iron coke addition amounts and charging methods have been systematically studied. Furthermore, the rapid cooling experiment has been conducted to explore and analyze the reduction, softening-melting, slag-iron dripping and material layer structure evolution behavior of BF mixed burdens at different smelting stages, and the influence mechanism of iron coke on the softening-melting-dropping performance of BF mixed burdens has been revealed. The results indicate that the addition of iron coke among iron-bearing burdens has a significant improvement effect on the softening-melting-dropping properties of BF mixed burdens. 20%-30% is the appropriate addition amount of iron coke used for BF smelting, and mixed charging is the appropriate charging method for iron coke. Compared with the situation that without adding iron coke, the softening interval of mixed burdens under the above optimization condition is increased from 136 ℃ to 197 ℃, the melting temperature interval is decreased from 171 ℃ to 152 ℃, the position of cohesive zone is relatively low; the dripping rate of slag and iron is improved from 59.1% to 78.7%; the maximum pressure drop of burden bed is decreased from 39.5 kPa to 3.6 kPa, and the S value is reduced from 3 616.1 kPa·℃ to 276.6 kPa·℃. Through analysis and discussion, the mechanism of adding iron coke to improve the softening-melting-dropping properties of BF mixed burdens is obtained. The increase in the addition amount of iron coke and the adoption of a mixed charging method between iron coke and iron-bearing burdens both can increase the dispersion distribution of iron coke among iron-bearing burdens and strengthen the close contact between iron coke and iron-bearing burdens. The above effects will strengthen the reduction promotion effect of iron coke on iron-bearing burdens, adjust and optimize the slag composition to reduce the viscosity of slag, promote metallic iron carburization, and support and interval the iron-bearing burdens. This can significantly improve the softening-melting-dropping properties of BF mixed burdens.

Electric furnace short process steelmaking is an important way to realize carbon reduction in iron and steel industry. However,the traditional electric furnace short process steelmaking takes scrap steel as raw material and electric energy as the main energy source. The carbon-oxygen reaction in the molten pool is insufficient,and the arc continues to discharge and ionize the air,resulting in high mass percent of nitrogen in molten steel and difficult removal and control of nitrogen. Due to the influence of nitrogen on the quality of steel,the control of nitrogen mass percent in steel has long been the key and difficult point in the production of high-quality steel with short process of electric furnace. At present,almost all high-quality steel grades with strict requirements for nitrogen mass percent in steel are manufactured by long process. In order to expand the production of steel in the short process of electric furnace and improve the competitiveness of the short process industry of electric arc furnace,the harm of nitrogen in steel and the difficulty of nitrogen control in electric furnace steelmaking were reviewed. The mechanism of nitrogen removal in molten steel and the research progress of nitrogen control technology in electric furnace steelmaking were summarized. Combined with the research and practice of our team,CO₂ compound injection nitrogen control technology and hollow electrode hydrogen-rich gas injection nitrogen control technology were proposed. CO₂ compound injection nitrogen control technology combines CO₂ carrier gas injection carbon powder with CO₂-Ar mixed bottom blowing. On the one hand,the nitrogen absorption of molten steel is reduced by reducing the nitrogen partial pressure in the furnace and optimizing the formation of foam slag. On the other hand,the nitrogen mass percent of molten steel is reduced by using the principle of efficient adsorption and denitrification of CO₂-Ar mixed bottom blowing. The hollow electrode hydrogen-rich gas injection nitrogen control technology isolates the air around the arc while using the arc generated by the electrode to ionize the multi-component gas into a hydrogen-rich plasma and combine the nitrogen in the steel to escape the molten steel to achieve denitrification. The results of industrial practice show that the average nitrogen mass fraction of electric furnace tapping of all scrap steel can be reduced from 0.008 14% to 0.005 08% by CO₂ compound injection nitrogen control technology. After the application of hollow electrode hydrogen-rich gas injection nitrogen control technology,the average nitrogen mass percent of electric furnace tapping can be reduced from 0.005 85% to 0.004 66%,and the lowest is only 0.002 99%. It can effectively reduce the nitrogen content of steel produced by electric furnace smelting,help the further development of high-quality steel production with short process of electric furnace,and promote the realization of green and low-carbon development goals of iron and steel industry.

Due to its good mechanical properties and cutting performance, sulfur-containing free-cutting steel is widely used in industries such as automotive manufacturing, machinery manufacturing, and shipbuilding industry. With the development in the fields of infrastructure, passenger vehicles, and maritime transportation in recent years , the production volume and quality requirements of sulfur-containing free-cutting steel have also increased. The method of calcium treatment is usually used to regulate the inclusions in the steel. However, the sulfur-containing characteristics of sulfur-containing steel have a significant negative effect on the cleanliness and castability of the steel during the smelting and casting processes. Therefore, establishing a reasonable calcium treatment process is of great importance for improving the castability of sulfur-containing free-cutting steel. The effects of factors such as the timing of sulfur wire addition, the time interval between feeding calcium wire and sulfur wire, and the amount of calcium wire added on the cleanliness of the steel and the clogging of nozzle were systematically investigated, analyzing the main reasons for the nozzle clogging in sulfur-containing free-cutting steel. The research shows that inclusions with CaS on the surface and Al₂O₃ in the core are generated in the steel after feeding sulfur wire and calcium treatment. The continuous deposition and adhesion of these inclusions on the inner wall of the nozzle are the main cause of nozzle clogging. In steel with w （[Al]）=0.03%, when w （[S]） exceeds 0.015%, it is prone to the formation of high melting point inclusions, deteriorating the castability of the steel. For 140 t of 45S sulfur-containing free-cutting steel, feeding the sulfur wire separately after LF and RH, extending the feeding interval between calcium wire and sulfur wire to over 10 minutes, and reducing the total feeding amount of calcium wire to below 100 m can effectively reduce the quantity of CaS·Al₂O₃ inclusions in the steel. This can increase the number of continuous casting heats for 45S steel to over 15 heats. It provides a theoretical basis for optimizing the calcium treatment process of sulfur-containing free-cuttingsteel, which helps improve production efficiency and product quality. It is of great significance for promoting the application and development of sulfur-containing free-cutting steel in the fields of machinery, transportation, and other industries. Future research will focus on how to control the quantity and morphology of inclusions in sulfur-containing steel, the impact of inclusions on the quality of steel plates after rolling, and how to reduce the amount of calcium added.