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.

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.

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.

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".

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.

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.

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 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.

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.

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 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.

Since the 18th National Congress of the Communist Party of China,the state has incorporated the prevention and control of air pollution into the overall social and economic development. The coking industry has become another industry that will implement ultra-low emissions after the thermal power and steel industries. China is the world's coke production,consumption and supply center,in 2023,China's coke production of 490 million tons,accounting for 70% of the world's total output. The implementation of ultra-low emission transformation in the coking industry is a systematic project,and it is necessary to coordinate the whole process to improve the air pollution control technology of enterprises. The implementation process of ultra-low emission transformation should realize the coordinated control of multiple pollutants,and promote the "double reduction" of pollutant emission intensity and carbon emission intensity. There are prominent problems in China′s coking industry, such as a wide variety of polltats, large emissions, and high ultra-low emission costs. The key technologies of typical air pollution control for reducing pollutant and carbon in the coking industry are reviewed. The pollutant source control technology represented by coke oven wall channeling control technology and waste gas reallocation technology can achieve significant reduction of SO₂ and NO_x,and the pollutant source reduction can relieve the pressure of flue gas end treatment. The difficulty of multi-pollutant collaborative treatment of coke oven flue gas is NO_x removal. Multi-pollutant control technology of activated carbon method and low-temperature SCR denitrification technology coupled with SDA desulphurization can achieve step-by-step removal of sulfur and nitrogen,which can achieve high denitrification efficiency and low-cost recovery of sulfur. Facing the national " carbon neutrality” and “carbon peaking" goal and the major demand of hydrogen metallurgy,coke oven gas uses CH₄ to transform into H₂ and CO through reforming reaction to achieve high value utilization and preparation of hydrogen-rich reduction gas to provide technical support for hydrogen-rich metallurgy,and realize the resource of greenhouse gases. The promotion and implementation of collaborative pollution reduction and carbon reduction air pollution control technology in the coking industry will be conducive to the green and high-quality development of the coking industry.

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.

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.

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.

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.

Under the "carbon peaking and carbon neutrality" target, scrap steel is becoming more and more important in the global steel industry due to its green and low-carbon characteristics. Enhancing the recycling level of scrap steel has become a key strategy for the transformation and upgrading of the steel industry. Currently, most research is focused on the contribution of using scrap steel to reduce emissions in the steel industry. However, there is still a lack of research on the development trends of the scrap steel industry and the carbon emissions in its production process. Based on the "emission-factor approach", the carbon emission level of scrap recycling process was quantitatively analyzed. Considering the three factors of energy efficiency, cost-effectiveness and environmental impact （especially carbon emissions）, the optimization model of scrap steel recycling process aiming at maximizing enterprise profit was established. The impact of scrap steel market prices, carbon trading prices, equipment energy consumption, and renewable energy applications on enterprise profits and carbon emissions was analyzed. The results of the study show that when carbon emissions are taken into account in production planning, the carbon emissions of scrap steel enterprises are reduced by 12.23%. At the same time, with the rapid construction of the national carbon market system, scrap steel enterprises can increase profits by selling excess carbon allowance indicators. While steel enterprises need to purchase extra carbon indicators, in which enterprises using short-process steelmaking reduce carbon trading costs by 55.6% compared with long-process enterprises. The increase in the proportion of photovoltaic power generation can achieve better carbon emission reduction effect. When the proportion of photovoltaic power generation is increased to 71.3%, carbon emissions can be reduced by 51.51% and the cost of purchased electricity can be reduced by 63.2% compared with the current scheme. Since the cost of purchasing raw scarp steel accounts for more than 70% of the total cost, market price fluctuations have a much greater impact on company profits than the fluctuations in energy costs or carbon emission income. When the purchase price and the selling price of scrap steel increase proportionally, the enterprise profit increases with the growth of scrap steel price. This study aims to provide guidance for scrap steel enterprises to optimize production planning in the context of "carbon peaking and carbon neutrality, "thereby achieving a win-win situation in both economic and environmental benefits.

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.

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.

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.

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.

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.

In order to study the characteristics and formation mechanism of inclusions in the smelting process of Fe-Cr-Ni corrosion-resistant alloy, industrial experiments were conducted to sample the entire process of 8810 nickel based alloy. Scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS） were used, and thermodynamic and kinetic calculations were combined to explore the characteristics and formation mechanism of large-sized inclusions. The research results indicate that the large-sized inclusions appearing in steel can be mainly divided into two types. One type is the micro inclusions of low melting point SiO₂-CaO-Al₂O₃-MgO large particles containing mass percent of SiO₂ bout 37%-45%, another type is low melting point CaO-Al₂O₃-MgO large particle micro inclusions without SiO₂. By comparing the composition of inclusions and slag, as well as calculating the size of slag inclusions using a model, it was verified that both types of inclusions were formed due to the inclusion of slag during the AOD stage steel stirring. However, during the AOD reduction period, the former was either removed or modified as CaO-Al₂O₃-MgO inclusions due to the recreation of slag and the increase of Al content. In the statistical analysis of inclusions, it is indicated that, the CaO-Al₂O₃-MgO inclusion is more severe than the SiO₂-CaO-Al₂O₃-MgO inclusion in the subsequent process, and it still exists until the casting period. Therefore, the behavior of low melting point CaO-Al₂O₃-MgO inclusions in subsequent smelting was analyzed through dynamic calculations and Thermo Calc software. The results show that the inclusions are not easy to float and remove from the appearance of AOD tapping until the end of LF hanging ladle. At the same time, it leads to the precipitation of TiN with CaO-Al₂O₃-MgO inclusions as the core during the solidification stage of mold casting, forming composite inclusions, as well as single TiN inclusions appearing during the solidification stage, which ultimately become the main types of inclusions in the ingot.

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.

Differential scanning calorimetry （DSC） is a precise technique for quantitatively analyzing thermophysical changes and thermal transition information in materials during thermal variations, characterized by high accuracy, rapid testing, and minimal sample requirements. The advancements in DSC have significantly broadened the scope of material property testing in steel and alloy research, facilitating a deeper investigation into the thermodynamics and kinetics of material thermal transitions. It commences with the fundamental theory of DSC, detailing its classifications and signal compositions, and offers a comprehensive overview of DSC's current applications in steel and alloy research. The advantages and limitations of DSC, particularly in the study of specific heat, phase transitions, precipitation and decomposition of secondary phases, and the glass transition in amorphous alloys are discussed. The integration of DSC with other techniques is also explored. Furthermore, it summarizes the current state of kinetic research utilizing thermal analysis data from DSC, including studies on activation energy and transition mechanisms in alloy phase transitions, as well as the development of kinetic models for alloy transformations. A comprehensive analysis of the thermophysical parameters of steels and alloys through DSC, combined with an in-depth understanding of the thermodynamics and kinetics of alloy phase transitions, is expected to provide robust theoretical support for the development, manufacturing, and application of alloy materials.

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.

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.

Sintering flue gas circulation technology has become an important technical measure for sintering machine to increase air volume and output, reduce CO, reduce air leakage, and reduce solid fuel consumption. Driven by the pollution reduction and carbon reduction policy of the iron and steel industry, increasing the flue gas circulation ratio can further strengthen the effect of pollutant emission reduction and waste heat utilization. Therefore, the high proportion of sintering flue gas circulation is an important trend of future technological development. The development and application status of flue gas circulation technology at home and abroad is systematically summarized, it is considered that sintering flue gas circulation technology has been perfect, and the main technical route should be the flue gas internal circulation scheme of high and low temperature flue gas combination. According to the different needs of sintering production, there are some differences in the selection of bellows, locations and air distribution schemes. In addition, in terms of process optimization, with the increase of flue gas circulation ratio, it should pay more attention to problems such as the decrease of oxygen volume fraction, the increase of water volume fraction, and the balance of air volume and heat. In the process of technology application, it should focus on the reliability of gas extraction, ash accumulation in pipeline, fan matching, flue gas distribution and the uniformity of the sealed hood flow field. On the basis of the research and application analysis of sintering flue gas circulation technology, the process design concept of high proportion flue gas circulation is introduced in detail, focusing on the high proportion flue gas circulation project applied by HBIS Group as an example. Through cycle process innovation, core equipment breakthrough and operation parameter optimization, HBIS Hansteel and Tangsteel New District have stably achieved a high proportion of more than 30% flue gas cycle, and achieved project promotion in 46 sintering machines. And practical experience for the implementation of high proportion flue gas circulation technology in sintering machines is provided. This is of great significance for vigorously promoting the application of sintering flue gas circulation technology and accelerating the process of pollution reduction and carbon reduction in the iron and steel industry.

With the rapid development of oil and gas industry, the requirements for the strength, toughness and weldability of pipeline steel are constantly increasing. Optimizing the argon sealing process during continuous casting is crucial for reducing or avoiding internal defects caused by argon bubbles, which is of great significance for improving the quality of pipeline steel products. L485M pipeline steel was taken as the research object, the effect of the sealed argon flow rate of the submerged entry nozzle on the internal defects of the pipeline steel L485M was studied by controlling the sealed argon flow rate and the casting speed. Then optimized the argon flow rate and casting speed to solve the internal defects of the slab caused by the argon bubble. The results show that,the argon bubble is generated when the flow rate is too high, which is easily captured by the solidification front of the slab and leads to the internal defects of the slab, formed elliptical flattened defects after rolling, distributed near the surface of the steel plate; An increase in argon sealing gas flow rate or casting speed will both lead to a higher occurrence rate of steel plate defects. Reasonable argon flow rate and casting speed of continuous casting machine are important parameters to ensure that bubbles can float up in time and not enter the slab. The reasonable casting speed of L485M pipeline steel slab with a specification of 260 mm×2 070 mm is 0. 75m/min, and the argon flow rate of split nozzle should not be greater than 2.5 L/min. The integral nozzle can effectively avoid the internal defects caused by argon bubble. The research results are of great significance for improving the theoretical process of argon sealing in the continuous casting of pipeline steel and enhancing the quality of pipeline steel products. They also provide reference value for the optimization of the submerged entry nozzle sealing process for other steel grades, the effect of continuous casting speed on internal defects caused by argon bubbles in slab, and the behavior of argon bubbles in the protective continuous casting process.

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.

Against the backdrop of achieving carbon peaking and carbon neutrality goals, China's steel industry is facing three challenges： international low-carbon trade barriers, entering the national carbon trading market, and demand for low-carbon products in downstream industries. Steel enterprises should adhere to the direction of intelligent and green development, accelerate the construction of digital carbon management systems that conform to their own characteristics, and better support their low-carbon and green development. It was focused on the integration of new generation digital technology and carbon management in steel enterprises, proposed a digital carbon management system architecture based on the level of enterprise informatization development and software and hardware conditions, and emphasized the coupling of digital carbon management system and enterprise business management processes. Based on the WisCarbon digital platform for carbon neutrality independently developed by HBIS Group, it was pointed out that data exchange is the fundamental for the integration of carbon management and process production management, digital carbon platform and information system, and the carbon data measurement and monitoring function of HBIS was introduced relying on the digital carbon management platform to collect, process and model production data related to carbon emissions in steel enterprises. Based on the digital carbon management system, an improvement has been realized in the carbon governance capabilities of HBIS main production lines, and good practical results in enterprise digital carbon accounting, product carbon footprint digital assessment, and CBAM digital reporting for export have achieved , providing a good demonstration for the steel industry to cope with increasingly severe carbon emission challenges.

The iron and steel industry is facing the problem of depletion of high-quality coal carbon resources and green carbon reduction, combined with the uneven distribution of coal resources in China, the large proportion of bituminous coal reserves and the global "carbon peak, carbon neutral" development background. The injection of high proportion bituminous coal can make full use of resources, alleviate the smelting cost of enterprises, and reduce the carbon emission of blast furnace smelting, which will become the mainstream trend in the future. In order to investigate the effect of high proportion bituminous coal injection on the process of blast furnace, a mathematical model of high proportion bituminous coal injection in blast furnace was established based on the production data of large blast furnace and the material balance and heat balance. Through theoretical calculation, the variation law of theoretical combustion temperature, gas content, direct reduction degree, carbon and heat distribution and carbon dioxide emission in blast furnace with the increase of bituminous coal injection ratio was analyzed. The results show that when the proportion of bituminous coal is increased by 10 percent point, the theoretical combustion temperature decreases by about 6-7 ℃, the direct reduction degree decreases by about 0.012, and the gas content in the furnace bosh increases by about 5 m³. Regional carbon, including the total carbon per ton of iron into the furnace, the carbon consumption of direct reduction of iron, the carbon consumption of desulfurization, and the carbon consumption of burning before the tuyere, all show a decreasing trend. The effect of heat distribution in the furnace is obvious. In terms of heat income, the heat release of carbon combustion decreases, the heat release of C and H elements increases, the physical heat brought by hot air decreases, and the overall heat income shows a downward trend. In terms of heat expenditure, desulfurization heat consumption decreases, coal decomposition heat increases, iron oxide decomposition heat consumption is basically unchanged, total heat expenditure is basically unchanged, and the whole furnace heat loss shows a downward trend with the increase of bituminous coal proportion. At the same time, the theoretical combustion temperature and heat loss decrease caused by the increase of bituminous coal ratio by 10 percent point, and the oxygen enrichment rate of 0.3 percent point and the coal ratio of 2.1 kg need to be increased at the same time to maintain the normal condition of the blast furnace. After blast furnace injection of high proportion bituminous coal, the carbon dioxide emission shows a decreasing trend, and the reduction of ton iron is about 3-5 m³.

Compared with sintering production, pellet production is more energy-efficient and environmentally friendly. The burden structure with high proportion of pellet is an effective way for blast furnace to achieve low carbon and green ironmaking. It is the key to realize the industrial production of fluxes pellets in blast furnace for high proportion pellet smelting. The belt roasting machine to produce fluxes pellets has great technological advantages. The three 3 000 m³ blast furnaces in Tangsteel New District designedly adopted 50%-70% pellet structure, and two 624 m² large-scale belt roasting machines were set up. In order to break the long-term technological monopoly for large-scale belt roasting machine abroad, the comprehensive research and development on the process technology and equipment of belt roasting machine was carried out in Tangsteel. Through the development of fine powder pretreatment, ore blending and roasting technology, the production technology of medium and high silicon flux pellets was mastered. With the design, manufacture and application research for the equipment localization, the localization of the core equipment of the large-scale belt roasting machine was realized to break the long-term monopoly of foreign countries. Through the development and application of intelligent technology, the efficient cooperation of pellet production line was obtained, and the production efficiency of belt roasting machine was significantly improved. Additionally, with the development and application of low energy consumption and low emission technology, the energy consumption and pollutant emission of the pelleting process were significantly reduced, the low-carbon and green production was realized. Apparently, the development and application of large-scale belt roasting machine in Tangsteel has achieved the full independent research, development and design of large-scale belt roasting machine and the localization of equipment for the first time, which has opened up a new situation for the promotion and application of belt roasting machine. To date, the production technology of flume pellets and the smelting technology of high proportion pellet in blast furnace have been mastered by Tangsteel. And these exploration and practice for burden structure in blast furnace of Tangsteel have played the good leading and demonstrative role in the popularization and application of burden structure with high proportion pellet in China.

With increase in the high top pressure, the BF iron-making process has obtained obvious improvement in China, and the intensified operation on BF also has been unprecedentedly increased. Apparently, this technology of intensified operation on BF with high top pressure has been widely adopted and recognized by industry. Nevertheless, the systematic theoretical research about this technology is relatively scarce currently, and the available research basically focused on the effect of high top pressure on the volume and flow rate of gas in BF. Therefore, based on the actual production, the impact mechanism of high top pressure on the smelting process of BF is systematically studied in this paper. Firstly, the effects of high top pressure on smelting intensity, lumpy zone, the pressure difference of burden columns, the distribution of gas flow and fabric, the activity of tuyere and hearth, the discharge of iron and slag, and the reaction of non ferrous elements are elaborated. Secondly, the actual level of different bosh gas index under high top pressure operation is statistically analyzed, and the revision suggestions also are proposed for the control standards of bosh gas index. It is point out that the relatively reasonable bosh gas indexes of BFs about 3 000, 2 000-3 000, and 1 000-2 000 m³ is 58-66, 58-70 and 58-85 m/min respectively. Finally, the theoretical research on high top pressure technology above has been applied and verified in the production of two 1 500 m³ BFs at Tangyin Company of Hebei Iron and Steel Group. Specifically, on the basis of successful blow-on and production, the intensified operation technologies mainly include high top pressure, large air volume, high oxygen enrichment, and low furnace temperature are used by the two BFs, as a result, the smelting of BF has been effectively strengthened, the various technical and economic indicators of BF also have been rapidly improved, and the successful application of intensified operation on BF with high top pressure has been achieved, which could provide certain reference significance and promotion value.

Competitive grain growth is a common problem in the solidification process, and these competitive behaviors ultimately affect the service performance of the production. At the same time, in the manufacturing process of single crystal turbine blades by directional solidification, grain competition is involved whether selected crystal method or the seeding method is used to control crystal orientation, which plays a decisive role in the successfully preparation of complete single crystal. Taking the model of competitive grain growth by directional solidification as an entry point, the research progress of the competitive grain growth mechanism is sorted out in detail. The factors influencing the competitive growth of grains are reviewed and their regulatory mechanisms are summarized. Firstly, differences in the outcome of competitive grain due to changes in the temperature gradient are presented. Secondly, in terms of solute concentration, the elimination behaviour of grains is presented in relation to solute interactions. And then, for the effect of crystal orientation, in order to better obtain the competitive grain results, the competitive relationship between the primary dendrite of grains deviating from the direction of the temperature gradient and the competitive relationship between the secondary dendrite deviating from the grain boundary by a certain angle are explored respectively, and the competitive elimination mechanism of grains is explained by expanding it from the initial two-dimensional to the three-dimensional orientation. Furthermore, it is summarized that the withdrawal rate, as the only parameter of directional solidification, which can be regulated over a wide range, affects the consistency of the elimination results, and the influence of cooling rate on competitive grain growth in the industrial production of iron and steel materials is clarified specially. Eventually, the prospects for future researches on competitive grain growth by directional solidification are further concluded, and urgent issues for future research are pointed out. In particular, the importance and application of competitive grain growth to alloy materials in practical industrial production is emphasised, helping to provide guidance to the manufacturing sector.

In recent years, the total steel production of China is about 1 billion t/a, and annual carbon emissions have reached 2 billion t, accounting for 15% of the total yearly carbon emissions of China, as is the industry with the highest carbon emissions in 31 manufacturing categories. Under the background of the national " Carbon neutrality" strategy, the low-carbon-production transformation and upgrading of the steel industry is imminent. Zhang Xuan Tech of HBIS firmly implements the national development strategy, takes the lead in closing the original blast furnace basis ironmaking equipment while building the world's first COG basis zero reformer direct reduction plant （DRP）, with an annual output of 1.2 million t of cold direct reduced iron （CDRI）. The construction of this plant was completed in December 2022, and stable continuous production was achieved in May 2023. In the initial stage of production, some problems were exposed in the heating furnace system, gas compressor system, water treatment system, etc. Although these problems did not affect normal production, they limited the further improvement of the plant's performance. In addition, the quality requirements for pellets in hydrogen-basis shaft furnaces far exceed expectations, such as the compression strength and other properties are insufficient, resulting in a higher DRI crushing rate and higher fines content in the DRI product during the initial production stage. Through in-depth analysis of the problems and continuous improvement and optimization of the process and equipment, great improvement has been gained in technical and economic indicators such as COG gas consumption and DRI metallization rate, which are even better than the design rate. Compared with the traditional blast furnace ironmaking plant, our new DRP has gained these achievement, CO₂ emissions are reduced by more than 70%, SO₂ emissions are reduced by more than 30%, NO_x emissions are reduced by more than 70%, dust emissions are reduced by more than 80%. The success of this plant represents a alternative road for the steel industry in China, and also marks the subversive, demonstrative and key footprint in the transformation of China's steel industry from traditional "carbon metallurgy" to a new type of "hydrogen metallurgy", which will further lead the transformation of traditional iron and steel metallurgy process and fully open a new era of green and low-carbon development.

OY furnace is a smelting reduction ironmaking technology,with the characteristics of pure O₂ blast,low burden height,and large temperature gradient,which is helpful to inhibit the formation of Ti（C,N） phase with high melting point and improve the gas and liquid permeability of the burden when smelting the vanadium-titanium magnetite. However,the softening,melting and dropping behaviors of vanadium-titanium burden in OY furnace are different from those in a conventional blast furnace because it employs a charging mode with mixed DRI and coke/coal. Therefore,it is of great significance to carry out a study on the influence of the mixed ratio of DRI and coke/coal on the softening and melting behavior of vanadium-titanium burden in the OY furnace. The effects of the mixed ratio of DRI/coke-coal on the burden of softening and melting temperature parameters,dropping ratio,and pressure drop are studied,and the properties of the dropping and residual slag and iron are analyzed by electron probe X-ray microanalysis. The results show that the mixed loading of DRI and coke-coal promotes the reduction and carburization of the vanadium-titanium DRI during the softening and melting process,enhances the deformation resistance of DRI before melting,and moves the softening interval to higher temperature zone. At the same time,the dropping temperature of DRI decreases,and the melting zone contracts to a lower temperature zone,thereby thinning the cohesive zone of OY furnace. As the mixed ratio of DRI and coke-coal increases （from 0 to 100%）,the dropping ratio of slag is nearly doubled,the vanadium yield of the hot metal is also improved. Although the increase of the mixed ratio accelerates the reduction of TiO₂ and the formation of TiC in the slag,it has the effect of weakening the slag foaming phenomenon due to the decreased residual slag used for foaming in the dropping zone,and the permeability of the burden layer is also improved. It can be seen that the mixed loading of iron ore and coke/coal in the molten gasifier is beneficial to the smelting of vanadium-titanium magnetite. The theoretical and technical basis for the smelting of vanadium-titanium ore in OY furnace is provided.

Under the target of carbon-peaking and carbon neutral, process change, optimization of raw materials and energy structure, and improvement of energy efficiency are the three main directions of carbon reduction for iron and steel industry. At present, low-carbon breakthrough metallurgical technology has not yet been deployed on a scale and there is a lack of sufficient and cheap clean energy, energy efficiency improvement is the most economical and effective measures for industry decarbonization. Benefiting from years of technology introduction, digestion, absorption and re-innovation, energy efficiency of Chinese iron and steel sector has reached the world advanced level, which leave it limit space for further improvement of energy efficiency. The status of domestic and foreign iron and steel industries/enterprises was researched and compared from three perspectives, production process, raw materials and fuels, as well as energy efficiency. Combined engineering practice with the domestic industrial structure and process characteristic, 7 directions and 24 correspondingly technologies are proposed under the vision of energy saving and carbon reduction,recovery and utilization of residual heat and energy, reduction of energy consumption and production loss, reduction of energy loss on techno-interface of production processes, energy efficiency improvement technologies for key energy-using equipment and relating systems, switching towards low-carbon-emission feedstocks and fuels as well as recycling of secondary resources, digital driving improvement of systems energy efficiency, and application of new materials. Based on study above, analyzed energy efficiency improvement potential of iron and steel sector from three directions, residual heat and energy, techno-interface heat convergence, and iron and steel production practice. The results shows that（measured in standard coal equivalent）, to produce 1 t of hot-rolled steel, the residual heat and energy of the main production process is about 185.0 kg/t, among them the utilization potential is about 129.4 kg/t; the available energy at each techno-interface of BF-BOF, BOF-continuous casting, continuous casting-hot rolling are about 10.5, 2.6 and 9.3 kg respectively. Taking a million-ton capacity integrated steelmaking enterprise as example, by application of energy efficiency improvement technologies, it can save 40.4 kg of energy per ton of hot-rolled steel.

In recent years, the steel industry has faced increasing pressure to reduce energy consumption and emissions. It has become the development direction of many steel companies to produce high-Mn cryogenic steel by using an efficient, energy-saving, and low-cost "converter/electric furnace→refining→continuous casting" process. However, high-Mn cryogenic steel has a high manganese and carbon content, which results in poor thermal conductivity of the molten steel and a large line expansion coefficient of the solidified slab shell during cooling. This can lead to considerable thermal stresses during cooling, increasing the risk of steel leakage. In addition, the reaction（[Mn] + （SiO₂） → [Si] + （MnO）） inevitably occurs at the steel-slag interface in the mold during the casting process, which leads to the change of slag composition and properties, and deteriorates the lubrication and heat transfer control function of mold flux. During the preliminary research, it is found that domestic steel mills using the continuous casting to produce high-Mn cryogenic steel are not running successfully, with the cast slabs prone to longitudinal cracks and frequent steel leakage accidents, some mills even have difficulty in batch cast. The surface defects of the slab and frequent steel leakage accidents have seriously hindered the large-scale production of high-Mn cryogenic steel. As one of the key technologies of continuous casting, mold flux technology has an important influence on ensuring the successful production and the surface quality of slab. At present, the research of high-Mn cryogenic steel mainly focuses on composition design, rolling heat treatment, welding technology and so on. However, there is no systematic report on the research and development of special mold flux system. Therefore, the reactivity of high-Mn steel between slag and steel, the influence of MnO on the rheological characteristics of slag, and the control of heat transfer through the slag film are reviewed, and the research focus of CaO-SiO₂-MnO based low reactivity slag system is clarified. The development of low reactivity slag for high-Mn cryogenic steel has important significance, which expands and deepens the theory of heat and lubrication coordination control of mold flux for difficult-to-cast steel species, promotes the efficient, green, and low-carbon production of the defect-free slab, and is also the development direction of future special slag systems.