The European Union （EU）'s Carbon Border Adjustment Mechanism （CBAM） has been officially released, which has attracted extensive and sustained attention from all sectors of society. Among the six categories of products covered by CBAM, iron and steel products are the most affected due to high carbon emissions and large export volume. Therefore, it is extremely urgent to quantitatively analyze the possible impact of CBAM on China's iron and steel exports and explore countermeasures. From 2020 to 2023, China's iron and steel products exports worldwide show a trend of volume increase and price decrease, and the export destinations are mainly distributed in the Association of Southeast Asian Nations （ASEAN）, South America and the EU. In 2023, China's total iron and steel products directly exported to the EU grew less than expected, indicating that CBAM has had a negative impact on China's iron and steel exports to the EU. China's iron and steel products are indirectly exported to the EU through Southeast Asia, so the comprehensive impact of CBAM o n China's iron and steel exports must be considered in parallel with indirect exports. The main target countries of China's iron and steel exports to the EU are Italy, Belgium and Germany. In 2023, China's total exports volume to the three countries fell sharply year-on-year, which is far more than the overall situation of iron and steel exports to the EU, indicating that the main importers of iron and steel products purchased from China in the EU are gradually changing. In addition, due to the high unit price of iron and steel products exported to Germany and France, the overall export volume is stable, indicating that high value-added iron and steel products have strong competitiveness in the EU. Finally, the impact of CBAM implementation on China's iron and steel exports is analyzed, and the response work is proposed from the four directions of adapting to the carbon market, keeping up with international carbon-related policies, continuous process optimization and carbon reduction, and building a full-process green supply chain, aiming to help China's iron and steel industry comprehensively respond to international carbon-related trade barriers, and provide reference and support for the high-quality and sustainable development of the industry.

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.

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.

In order to address the common problems of uneven temperature distribution of rolling rolls, frequent fluctuations in hot roll profiles, and local hotspots in traditional cooling modes of hot rolling, a finite difference model for segmented cooling of work rolls in hot rolling was established based on the dynamic thermal conductivity characteristics of online rolling rolls to quantitatively adjust the transient temperature gradient of rolling rolls and online hot roll profiles, and better control the horizontal thickness difference accuracy of products. Firstly, a contact thermometer was used to quickly measure the temperature along the horizontal direction of the work roll, and the convective heat transfer coefficient of the online temperature field was reverse calculated. Combined with actual operating parameters, the temperature field of the rolling process was simulated. By comparing the simulation results with the on-site measured data, the reliability of the model was verified. Subsequently, taking into account key factors such as opening water volume, bandwidth, and rolling time, a comprehensive analysis was conducted on the dynamic changes in roll temperature and thermal convexity during the hot rolling process. The results show that increasing the total cooling water opening ratio by 20% results in a 6.5 ℃ decrease in roll temperature, a 32.0 μm decrease in thermal convexity; a 10 s decrease in rolling time, a 5.1 ℃ decrease in roll temperature, and a 24.3 μm decrease in thermal convexity. However, the uniformity of thermal expansion of wide strip steel is better. By comparing three typical horizontal segmented cooling modes, it is found that when the horizontal distribution of cooling water is adjusted online, the roll temperature and thermal convexity dynamically change accordingly. Choosing the appropriate segmented cooling mode according to the working conditions can accurately adjust the overall roll temperature and horizontal temperature difference to the set range. An important basis is provided by this study for the optimization for the selection of segmented cooling modes and comprehensive optimization of plate shape and convexity for multi stand hot rolling. A theoretical foundation is laid for the design of high-efficiency hot rolling cooling devices and multi condition coupled segmented cooling systems.

The consumption of fossil energy in the steel industry intensifies environmental pressures, with the ironmaking process serving as a critical link in energy conservation and emission reduction throughout the sector. In the context of China's goals for "carbon peaking" and "carbon neutrality", the exploration and utilization of green renewable energy sources as substitutes for fossil fuels is an essential pathway for the development of the steel industry. Biomass, recognized as a green, carbon-neutral resource, possesses characteristics such as widely distributed, low pollution, and renewability. The application of biomass energy in ironmaking can significantly contribute to energy savings and emission reductions, playing a crucial role in mitigating carbon consumption in the steel industry. The distribution of biomass resources, pretreatment methods, utilization approaches, and the physical and chemical properties of biomass were systematically discussed, while the current research status of natural biomass, biomass char, and biomass derivatives was discoursed in direct iron reduction, blast furnace injection, biomass coke, biomass pellets, and biomass sintering. Firstly, it is noted that biomass can be directly added as a reactant to pellets for the reduction of biomass iron ore pellets, and that syngas generated from biomass pyrolysis and gasification can also be used for the reduction of iron ore. Furthermore, future efforts could focus on improving biomass processing methods to optimize the quality of biomass sinter and biomass pellets by enhancing raw material particle size and ratios, thereby optimizing the use of biomass for blast furnace injection or existing charge preparation processes. Given the inherent physicochemical properties of biomass, further fundamental research is necessary for its application as energy in the ironmaking process. Specifically, exploration and practical studies on the crushing strength and metallurgical properties of biomass composite iron ore raw materials developed for large blast furnaces are needed. Additionally, strengthening inter-industry collaboration to develop high-strength, highly reactive biomass composite materials suitable for blast furnace production represents one of the future research directions.

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.

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.

In recent years,promoting the high-quality development of China's iron and steel industry and working to achieve the "dual-carbon" goal are the overall guiding principle of the development of China's iron and steel industry. Under this background,the characteristics of China's iron and steel industry have changed significantly. The characteristics of the iron and steel industry are described in detail,including the analyses of crude steel outputs and annual growth rates of China from 2000 to 2023. Combined with the evolution modes of crude steel output in developed countries,the phase of China's steel output is predicted. Based on the proportion of different iron and steel manufacturing processes in China from 2000 to 2023,the CO₂ emission values per year of the whole iron and steel manufacturing process is calculated,which plays the role in judging the urgency and necessity of achieving the "dual carbon" goal in China. The current situations of the iron and steel manufacturing process in major steel producing countries are used as the research object for explaining the features of ensuring the best quality of steel products and reaching the best steel manufacturing efficiency. This also can clarified the current roles and effects of various iron and steel manufacturing processes. Combined with the above analysis,the corresponding strategy of the structural adjustment of iron and steel manufacturing process in China is studied with the perspective of engineering philosophy and overall strategic thoughts. Meanwhile,the structural adjustment scheme of "BF-BOF" traditional process,"Short process of" total scrap-EAF " and" 100% hydrogen base reduction DRI-EAF " process are proposed to adapt the new iron and steel characteristics. Three critical issues in the process of iron and steel manufacturing process are discussed,including the scrap quantity for EAF steelmaking,the mathematical prediction of powder consumption during the process decarbonization and innovate ways for eliminating steel quality defects due to scrap smelting process residual elements enrichment in EAF steelmaking process. Once these issues are solved successively,it will benefit the iron and steel manufacturing process structural optimization and high quality development in China.

Under the current "dual-carbon" framework, the high-value utilization of typical large-scale solid wastes from metallurgical processes and other major industrial sources has emerged as a critical issue demanding urgent resolution within the industry. Large-scale solid wastes from metallurgical processes, including blast furnace slag and dust ash, as well as other major industrial solid wastes such as fly ash and coal gangue, are rich in valuable resources like silicon and aluminum. Through appropriate conditioning and proportioning treatments, these solid wastes can be transformed into inorganic fiber materials exhibiting excellent thermal insulation and refractory properties, thereby achieving high-value utilization of both metallurgical and other major industrial solid wastes. The research progress in preparing mineral wool fibers is reviewed, using conditioned blast furnace slag as the raw material and silicon-aluminum-based ceramic fiber materials using dust ash in combination with fly ash or coal gangue. It analyzes the advancements in the production of inorganic fibers via the spray-blowing method and the centrifugal method from three perspectives, fundamental principles, experimental studies, and industrial practices. Pilot-scale experimental studies are conducted to produce mineral wool fibers from conditioned blast furnace slag using both spray-blowing and centrifugal methods. The results indicate that spray-blowing pressure significantly affects the content of fiber slag balls, while having minimal impact on the average fiber diameter. Specifically, increasing the spray-blowing pressure from 0.20 MPa to 0.38 MPa reduces the fiber slag ball mass fraction from 25% to 16%, with negligible changes in fiber diameter. Conversely, roller speed has little effect on fiber slag ball content but significantly influences fiber diameter; as roller speed increases, the average fiber diameter decreases from 3.17 μm to 2.73 μm. The study further compares the differences between mineral wool fibers produced by the two methods in terms of fiber diameter, fiber slag ball content, and fiber compressive strength. Additionally, it outlines the application prospects of silicon-aluminum-based inorganic fiber materials, derived from metallurgical large-scale solid wastes in conjunction with other major industrial solid wastes, in sectors such as construction, industry, aerogels, and photocatalytic materials. Building upon the existing research foundation, future research directions for the production of inorganic fiber materials from metallurgical large-scale solid wastes is proposed, aiming to further advance waste valorization, energy conservation, and carbon reduction.

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.

Two types of turbulence inhibitors, namely cylindrical turbulence inhibitor and impact pad, were used in a 6-strand tundish with side-arranged inlet of a steelmaking plant. In order to evaluate the metallurgical effect of the two types of tundish during the ladle changeover process, the flow field distribution of the two type of tundishes and the slag entrapment situation in the water model, evolution of inclusions during the ladle changeover process were studied by industrial sampling, physical model, and numerical simulation methods. Particle image velocimetry （PIV） was applied to measure the flow field distribution and velocities at the water oil interface. The morphology, size, and composition of inclusions in the two type of tundishes during the ladle changeover process were explored by industrial sampling and Scanning Electron Microscopy-Energy Dispersion Spectrometer （SEM-EDS）. The results show that the velocity spatial distribution inside the tundish is uneven, with higher velocity in the impact zone and lower velocity at the edge strand. There is an upward backflow in the tundish with a cylindrical turbulence inhibitor. At a normal casting rate of 2.65 t/min, the maximum fluid velocity at the water oil interface of both types of tundish is around 50 mm/s, indicating a relatively stable water oil interface. When rapidly refilling （5 t/min） after ladle change, a circulation is formed near the wall in the impact zone of the tundish with a cylindrical turbulence inhibitor, and a strong horizontal flow that paralleling to the liquid surface towards the outlet is formed. The maximum velocity at the water oil interface is 285.16 mm/s, and the slag eye area is 735.42 cm². A large number of large-sized oil droplets are entrained in the impact zone. For the tundish with an impact pad, the impact zone forms an upward flow field along the wall, with a maximum velocity of 186.54 mm/s at the water oil interface and a slag eye area of 399.27 cm². Small oil droplets are entrained in the impact zone, forming a water oil mixture. The sampling results before and after the ladle change show that no large-sized （≥50 μm） inclusions are found in both types of tundish at the end of casting of the previous heat. After the liquid level rise to the normal working level, a large-sized inclusion with a size of 240.32 μm is found in the tundish with a cylindrical turbulence inhibitor. The average size of the inclusion increases from 13.18 μm to 29.88 μm, and the proportion of large-sized （≥50 μm） inclusions is 24%. The mass fraction of CaO in the inclusion increases significantly. However, no inclusions with a size larger than 100 μm are found in the tundish with an impact pad, and the average size of inclusions remains basically unchanged. The proportion of large-sized （≥50 μm） inclusions is 6.7%. Overall, the metallurgical effect of the impact pad is superior to that of the cylindrical turbulence inhibitor.

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.

The smelting tasks at blowing stage in converter vanadium extraction process are different,and the composition and temperature of the molten pool are constantly changing,which makes the working conditions such as oxygen supply lance position and flow rate change at different stages of smelting,resulting in different stirring characteristics of the molten pool at different stages of blowing. The stirring energy model of converter molten pool was established,and the effects of temperature,oxygen supply flow and bottom blowing on the stirring energy of molten pool in different blowing stages were studied. It is found that the energy density of top blowing stirring in each stage of converter vanadium extraction process is significantly smaller than that of bottom blowing stirring,and the CO bubble stirring energy generated by chemical reaction only accounts for 0.41%-1.74%. With the smelting process,the top blowing stirring energy density decreases from 165.30 W/t to 144.63 W/t,and then gradually increases to 192.84 W/t. The stirring energy density produces by CO bubbles is up to 15.21 W/t. The stirring energy density produced by bottom blowing nitrogen gradually increases from 786.92 W/t to 865.57 W/t. In the smelting process,the stirring energy of the molten pool is reasonably increased by changing the top blowing lance position and bottom blowing flow rate at different stages,and the carbon loss can be effectively reduced. On this basis,the effects of different Mach number,oxygen flow rate,lance position and bottom blowing intensity on the impact characteristics and mixing time of molten pool were studied by 1∶3 water model experiment. With the progress of blowing,the impact depth of the molten pool is 61-90 mm under the condition of Mach number of 1.97,and the impact range of the molten pool is 19.93%-29.41%. The change degree of impact diameter is 37.41%-42.54%. The longest mixing time is 54 s and the shortest is 39 s. The process system of vanadium extraction from converter is optimized. In addition,when the bottom blowing intensity is greater than 0.09 m³/（min·t）,the mixing time of the molten pool is significantly reduced. When the bottom blowing intensity reaches 0.12 m³/（min·t）,the stirring intensity of the molten pool decreases. When the bottom blowing flow rate increases to 0.15 m³/（min·t）,the mixing time of the molten pool reaches a minimum of 27 s. In order to reduce the mixing time of the molten pool,the bottom blowing intensity can be appropriately increased to improve the efficiency of vanadium extraction. It is beneficial to achieve vanadium extraction and carbon conservation in the converter by adjusting the lance position and gas supply intensity at different stages of vanadium extraction and blowing,and reasonably controlling the stirring characteristics of the molten pool.

As the blast furnace production process becomes increasingly complex,the thermal conduction characteristics of the cooling wall under extreme high-temperature and high-pressure conditions are facing more stringent demands. Traditional heat conduction models can no longer meet the need for precise predictions. Therefore,fractional-order heat conduction models,which effectively describe complex media and multi-scale heat transfer phenomena,have garnered widespread attention. A review of heat transfer research on blast furnace cooling walls based on fractional-order heat conduction models is provided, aiming to offer a theoretical foundation for thermal management and prolonging the service life of cooling walls. Firstly,the mathematical basis of fractional-order heat conduction models and their associated equations are introduced,followed by an analysis of the characteristics of fractional-order equations and commonly used solution methods. Next,the heat conduction mechanisms of the blast furnace cooling wall under extreme conditions such as high temperatures and pressures are discussed in detail. A method for establishing a three-dimensional fractional-order heat conduction equation is proposed,and the framework for analyzing the heat transfer process is explored through numerical simulations and experimental validation. Finally,the current state and challenges of applying fractional-order models to the study of blast furnace cooling walls are analyzed. The potential applications of these models in the design of cooling wall materials and structures,offering future research directions,including model accuracy enhancement,optimization of computational methods,and promotion of practical engineering applications are explored. These studies provide valuable theoretical support and technical references for the thermal management and optimization design of blast furnace cooling walls.

In order to realize the efficient treatment and resource utilization of steel slag, it aims to use blast furnace slag as a "modifier" to modify high basicity steel slag,improve the physical properties of steel slag, optimize the mineral composition of steel slag,and reveal the influence mechanism of slag microstructure on viscosity. The experimental raw materials and modified slag were analyzed by high temperature physical property tester,X-ray diffractometer（XRD）,scanning electron microscope（SEM-EDS）and Raman spectroscopy（Raman）. The results show that with the increase of the basicity（1.6-2.4）of the mixed slag,the melting temperature decreases first and then increases. When the basicity is 2.0,the high-temperature physical properties are the best. At this time,the proportion of blast furnace slag is 35.19%（mass fraction）,the melting temperature is 1 383.30 ℃,the melting time is 1.05 s,and the viscosity（temperature more than 1 405 ℃） is lower than 0.25 Pa·s.The homogeneous reaction effect is good,and the structure of each mineral is clear and evenly distributed. It is mainly composed of gehlenite（Ca₂Al₂SiO₇）,magnesium pyroxene（Ca₃MgSi₂O₈）, cementitious minerals dicalcium silicate（Ca₂SiO₄）and tricalcium aluminate（Ca₃Al₂O₆）,which realizes calcium stabilization and enrichment of cementitious materials. In addition,with the increase of basicity from 1.6 to 2.0,the high polymerization degree units in the slag microstructure undergoes a depolymerization reaction,and the relative content of the low polymerization degree unit QSi0 increases,which simplifies the microstructure and reduces the polymerization degree parameter n（BO/T）_e（the average number of bridging oxygen per tetrahedron in the network structure）to a minimum value of 0.87.When the basicity increases from 2.0 to 2.4,the role of [AlO4] in network construction is enhanced,the number of high polymerization degree units QAl3 and QAl4 increases,and the n（BO/T）_e value increases to 1.69. The calculated value of n（BO/T）_e is in good agreement with the experimental results of viscosity. This study can provide reference for the research on the viscosity of blast furnace slag quenched and tempered steel slag,the optimization of the phase composition and structure of steel slag,and is expected to promote the resource utilization of iron and steel solid waste（blast furnace slag,steel slag）.

The thermodynamic characteristics, reaction mechanisms, and the impact of temperature and time on the reduction process of hematite （Fe₂O₃） by ammonia （NH₃） were to be explored. The standard Gibbs free energy of the reduction reactions between Fe₂O₃ and Fe₂SiO₄ with NH₃, H₂, and CO was calculated using HSC Chemistry 6.0 software to assess the feasibility of NH₃ as a reducing agent. The horizontal high-temperature furnace was used to heat and reduce hematite, with the reduction effects investigated under various temperature and time conditions with NH₃. The results show that NH₃ can effectively reduce Fe₂O₃ at 290 ℃, while H₂ requires a higher temperature of 542 ℃, indicating that NH₃ has a reduction advantage at lower temperatures. The thermodynamic reaction temperature for NH₃ reduction of Fe₂SiO₄ is 480 ℃, in contrast, CO and H₂ are not spontaneous at this temperature, demonstrating the thermodynamic advantage of NH₃ in reducing Fe₂SiO₄. As the temperature increases, the weight loss and reduction rates of hematite increase, and hematite can be completely reduced by NH₃ with the volume fraction of 30% at 900 ℃. The extension of reduction time also leads to an increase in weight loss and reduction rates, with 90% reduction rate achieved in 60 min and 100% reduction rate in 180 min. Characterization of the reduced samples by XRD, SEM, and OM reveals that Fe₂O₃ is first converted to Fe₃O₄, then rapidly to FeO, and finally FeO is converted to pure iron （Fe）. EDS spectral analysis shows that as the reaction proceeds, the content of O atoms decreases while the content of Fe atoms increases, ultimately achieving the complete reduction of Fe₂O₃ to pure Fe. During the NH₃ reduction of Fe₂O₃, the number of N atoms first increases and then decreases, indicating that Fe is nitrided by NH₃ to form Fe₄N, which then decomposes at high temperatures to produce Fe and N₂. NH₃ shows a significant thermodynamic advantage in the reduction of hematite, and the reduction process can be divided into several stages, initial slow conversion, rapid reaction in the middle, and a decrease in reaction rate in the later stage due to product coverage. The entire process is completed within 30 min, ultimately achieving the complete conversion of Fe₂O₃ to pure Fe. Theoretical basis and experimental data support are provided for the industrial use of NH₃ to reduce hematite.

Steel slag tailings are the main solid waste produced in the steelmaking process. With the increase of steel production, the stock of steel slag tailings is increasing year by year, which has a great impact on the environment. The content of basic oxides such as CaO in steel slag tailings is high. One of the most important ways to use it is to replace part of the sintering flux to return to sintering, but it cannot be determined whether the steel slag tailings participate in sintering and mineralization. The influence mechanism of steel slag tailings on sintering and mineralization is unknown. Therefore, with the help of the basic characteristics test method of high temperature sintering, the influence of using steel slag tailings and Ca（OH）₂ reagent to adjust the basicity on the basic characteristics of high temperature sintering was studied, and the sintering cup experiment to verify whether the steel slag tailings were involved in the sintering reaction was carried out. The process mineralogy analysis of sinter was carried out by X-ray diffraction and metallographic microscope, and the related mechanism of steel slag tailings participating in mineralization was revealed. The results show that the assimilation temperature of the sintering raw material with steel slag tailings decreases and the liquid phase fluidity index increases. The main factor is that the steel slag tailings contain SiO₂. When the content of SiO₂ increases, the low melting point compounds of olivineincrease correspondingly, which will promote the formation of silicate low melting point system, so as to increase the amount of liquid phase and enhance the strength of the bonding phase. At the same time, the Al₂O₃ in the steel slag tailings will promote the formation of composite calcium ferrite, which is conducive to obtaining the best bonding phase, and the amount of calcium ferrite increases significantly. When steel slag tailings are used as flux, under the condition of basicity 1.82, the drum strength of sinter reaches 65.5%, and the yield reaches 82.8%. In the microstructure of sinter, hematite and magnetite are mostly porphyritic structure, and calcium ferrite is mostly acicular. The dicalcium silicate is mostly willow leaf-like, and the calcium ferrite and magnetite are interwoven and embedded in the structure, indicating that the addition of steel slag tailings in sintering can promote the sintering mineralization reaction.

The efficient recovery and utilization of residual energy from converter flue gas plays a significant role in reducing carbon emissions in steel production. Based on Gibbs free energy minimization principle, a thermodynamic model for producing high quality syngas from carbon-containing raw materials in vaporizing cooling flue of converter was established by Aspen Plus. The effects of water content and added amount of pulverized coal, biomass and waste tire powder, temperature and composition of the flue gas on CO₂ gasification were discussed. The results indicate that, under identical injection conditions, the pulverized coal exhibites the most substantial impact on increasing the volume fraction of CO and heating value of the syngas, followed by waste tire powder and biomass. Additionally, biomass demonstrates a higher carbon conversion rate compared to pulverized coal and waste tire powder. Furthermore, waste tire powder exhibites a higher gas production rate and H₂ content compared to pulverized coal and biomass. It is evident that the addition of raw materials has a marked effect on the concentration of CO and H₂, and the gas calorific value, particularly in the case of pulverized coal. However, it should be noted that an excessive amount of raw materials can lead to a decline in the gas production rate and carbon conversion rate. Increasing the moisture content of the raw material to 20% can promote the generation of H₂ to a minor extent. However, it will result in the inhibition of CO generation and a consequent reduction in gas calorific value, carbon conversion rate and gas production rate. Conversely, an elevated flue gas temperature has been observed to enhance the concentration of H₂ and CO in the product, as well as the carbon conversion rate, but excessively high temperature leads to a decrease in H₂ concentration. Correlation analysis reveals that the raw material addition and flue gas composition are the most influential factors on the gasification process. The flue gas temperature exertes a greater influence on carbon conversion rate and gas yield, while the moisture content has a comparatively minor effect. In summary, under the conditions of 1 400 ℃, biomass addition M/G （carbon-containing material mass per unit volume of converter flue gas）= 0.09, pulverized coal addition M/G=0.06, waste tire powder addition M/G=0.05, raw materials moisture content less than 1%, and a flue gas composition of φ（CO）/φ（CO₂）=3, the gasification process of carbon-containing raw materials injected into converter flue can achieve the best gasification performance. This study provides valuable technical support for improving the resource utilization efficiency of converter flue gas and promoting the green and low-carbon transformation and development of the iron and steel industry.

The low-temperature reduction degradation index（I_{RD>3.15 mm}） is a critical measure for assessing the quality of sinters. However, complicated test methods, high equipment requirements, and long test times are the existing problems. The thermoelectric coefficients of five representative high-basicity sinters from Hebei Province were systematically assessed using polarizing microscope and thermoelectric coefficient tester to identify a straightforward, eco-friendly, and effective testing approach. Moreover, the relationship between the thermoelectric properties of these sinters and I_{RD>3.15 mm} was examined. The results show that the 5 typical high-basicity sinters have obvious thermoelectric properties, and the thermoelectric coefficient is mainly distributed in 60-270 μV/℃. Furthermore, a significant negative relationship is observed between the thermoelectric coefficient and I_{RD>3.15 mm}. Due to the heterogeneity of the sinter structure, there is a variation in the thermoelectric characteristics across different sections of the same specimen. The area where the protogenetic granular hematite is concentrated has no thermoelectric property. The thermoelectric coefficient of the interlaced/erosion structure composed of silica-ferrite of calcium and aluminum （SFCA） and magnetite is mainly distributed in the range of 60-160 μV/℃, and the average thermoelectric coefficient is 114.77 μV/℃. The thermoelectric coefficient of the concentrated secondary skeleton crystalline hematite is significantly increased in the region of orientation, mainly distributed in 190-270 μV/℃, and the average thermoelectric coefficient is 221.81 μV/℃. The secondary skeleton crystalline hematite content is the key factor in determining the average value of the pyroelectric coefficient of the sinter. With the increase of the secondary skeleton crystalline hematite content, the average value of the pyroelectric coefficient of the sinter increases, and the I_{RD>3.15 mm} decreases. There are obvious correlations among the sinter's average thermoelectric coefficient, secondary skeleton crystalline hematite content, and the low-temperature reduction disintegration index I_{RD>3.15 mm}. The results provide a new idea for evaluating the low-temperature reduction pulverization properties of sinter and have guiding significance for applying mineral thermoelectric characteristics in the metallurgical field.

Hydrogen energy is one of the most promising clean energy sources in the 21st century. Low temperature liquid hydrogen storage has been adopted as an efficient hydrogen storage method in the industry. TAS31608-LH is liquid hydrogen storage tank material and produced by Taiyuan Iron and Steel Stainless Steel Co., Ltd. This material is used at ultra-low temperatures （-253 ℃）, which puts extremely high requirements on the microstructure and comprehensive properties. So it is necessary to conduct research on the thermal deformation behavior that directly affects the microstructure of materials. The hot compression experiments of continuous casting billets taken from industrial production was studied, with deformation temperatures ranging from 950 ℃ to 1 200 ℃ and strain rates ranging from 0.01 s^-1 to 10 s^-1. Based on the true stress-strain curve, the thermal deformation behavior of the material was studied, and Arrihenius and BP neural network constitutive models were established for the relationship between deformation parameters and rheological stress. The hot working diagram was constructed based on a dynamic material model, and the optimal hot working range of the material was determined through microstructure analysis. Research has shown that the rheological stress of TAS31608-LH decreases with increasing temperature and decreasing strain rate. The deformation temperature has significant impact on the softening mechanism of materials. When the temperature is below 1 050 ℃, the true stress-strain curve is mainly of dynamic recovery type, while when the temperature is above 1 050 ℃, the curve gradually transforms into dynamic recrystallization type. BP neural network constitutive model has more training samples and wider prediction range, resulting in higher prediction accuracy than the Arrihenius model with strain compensation. Based on the hot working diagram, the microstructure under different deformation conditions was analyzed, and the reliability of the hot working diagram was verified. The optimal hot working range for TAS31608-LH is determined to be 1 150-1 200 ℃, with a deformation condition of 10 s^-1. In addition, research has found that the solidification residue of the continuous casting billet δ-Ferrite has an excitation effect on the dynamic recrystallization of austenite during hot deformation, which can lead to uneven overall microstructure size and distribution.

To study the effect of w（（CaO））/ w（（Al₂O₃）） in the refining slag on the molten steel during the secondary refining process, the w（（CaO））/ w（（Al₂O₃）） was adjusted through industrial trial. The change of the sulfur content in steel was analyzed. The results shows that the desulfurization ability of the refining slag with the w（（CaO））/ w（（Al₂O₃）） of 2.0 is better than that of refining slag with the w（（CaO））/ w（（Al₂O₃）） of 1.6. The melting temperature, solid phase fraction, viscosity, and sulfide capacity of the refining slag with different w（（CaO））/ w（（Al₂O₃）） are calculated. When the w（（CaO））/ w（（Al₂O₃）） in the refining slag exceeded 1.8, the refining slag transitions from the liquid phase to a semi-liquid phase, and the solid phase fraction of the refining slag increases continuously at 1 873 K. The influence of viscosity kinetic factor on the desulfurization ability of slag was considered. A dimensionless desulfurization index of S_index was proposed to represent the desulfurization ability of the refining slag. It is revealed that with the increase of w（（CaO））/ w（（Al₂O₃）） in the refining slag, the viscosity of the slag first decreases and then increases. When the w（（CaO））/ w（（Al₂O₃）） is 1.8, the viscosity η reaches a lowest level. With the increase of w（（CaO））/ w（（Al₂O₃）） in the refining slag, the sulfur capacity C_s gradually increases. With the increase of w（（CaO））/ w（（Al₂O₃）） in the refining slag, the value of S_index first increases and then decreases. When the w（（CaO））/w（（Al₂O₃））of the slag is 2.0, the value of S_index reaches a highest level. It is suggested that control the w（（CaO））/w（（Al₂O₃）） of the slag within the 1.8 to 2.0 is more beneficial for improving the desulfurization ability of the slag. Finally, the S_index of CaO-Al₂O₃-SiO₂-5.68%MgO refining slag at 1 600 ℃ was calculated. In the liquid region of the refining slag, the S_index increases with a higher w（（CaO））/ w（（Al₂O₃）） in the refining slag, which is beneficial to improve the desulfurization efficiency of the molten steel.

Longitudinal off-corner cracks on the wide face of stainless steel slabs were found in a domestic steel plant. The formation mechanism of longitudinal off-corner cracks on the wide edge of continuous casting slabs was revealed through laboratory testing and analysis, and stress simulation. The grains near the longitudinal off-corner cracks were coarse, and there was a layer of pre-precipitated ferrite with a thickness ranging from tens to hundreds of microns at the original austenite grain boundary, and the cracks mainly occurred along the filmy pre-precipitated ferrite. The characteristic element Na of the mold powder was detected inside the longitudinal off-corner cracks on the wide face of slabs, therefore it was determined that the longitudinal off-corner cracks were generated in the mold. When the distance from meniscus was greater than 0.2 m, the stress on wide surface of continuous casting slab increased with the distance from corner. The maximum value was reached near the corner, and then the stress value gradually decreased and tended to be stable. The corners of continuous casting slab were subjected to two-dimensional cooling, resulting in a large solidification shrinkage and led to the appearance of gaps, which weakened the cooling intensity of the corners and caused the thinnest point of the solidified shell to appear near corner on the wide face of slab. Due to the solidification shrinkage, there was maximum stress near the edge of continuous casting slab. When the taper of mold could not completely match the solidification shrinkage, depressions or cracks would appear at the thinnest point of solidified shell at the wide face edge of continuous casting slab. The formation mechanism of longitudinal off-corner cracks on the wide face of stainless steel slabs is revealed, and a theoretical basis for controlling surface defects in continuous casting slabs is provided.

Concentrated solar power plants usually use a mixture of NaNO₃ and KNO₃ molten salt as the heat transfer fluid for the thermal storage system. The high-temperature corrosion resistance of 304 austenitic stainless steel used for the thermal storage system structure in the molten salt environment is particularly important. The influence of microalloying element Nb on the steel mainly lies in the refinement of grains, precipitation strengthening, and improvement of toughness. However, the mechanism of 304 austenitic stainless steel's high-temperature corrosion in molten salt under Nb is not clear, which is worth further research. Two groups of test steels containing 0.49Nb and 0Nb were subjected to a 0-200 h molten salt corrosion test at 565 ℃ under a constant temperature molten salt immersion method, and the corrosion mass loss was measured and the corrosion rate was calculated. The corrosion layer and base material organization were characterized using scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and energy dispersive spectrometry （EDS）. The research results show that when the corrosion time is 200 h, the corrosion rates of 0Nb and 0.49Nb are 178.1 μm/a and 133.9 μm/a, respectively, indicating that adding Nb element can improve the resistance to molten salt corrosion. Both samples form a double corrosion product layer on the surface, with the inner layer mainly being FeCr₂O₄ and the outer layer being Fe₂O₃ and Fe₃O₄. The internal stress generated by Fe oxides is easy to produce defects or cause the corrosion layer to peel off, leading to the intrusion of oxidizing ions in the molten salt and the deterioration of the protective properties of the Fe oxide layer. Nb has a low content in the corrosion layer and forms uniform and dispersed NbC in the steel matrix, inhibiting the precipitation of Cr carbide at grain boundaries, while the precipitation of Cr carbide at grain boundaries is prone to causing intergranular corrosion, and intergranular corrosion will introduce more stress into the corrosion layer. The corrosion layer of the steel sample without Nb is thicker and has more cracks, indicating that the addition of Nb element can improve the high-temperature corrosion resistance of 304 austenitic stainless steel in molten salt.

As a high-carbon emission field, the green low-carbon transformation of the steel industry is of great strategic significance to achieve the goal of "double carbon". The deep integration of hydrogen energy and steel processes, especially hydrogen metallurgy technology, fundamentally reduces the dependence on carbon by replacing "hydrogen" with "carbon" reduction, and has become an important direction of future ironmaking technological innovation. The current mainstream multi-hydrogen metallurgy process technology and its implementation path are systematically described, in-depth analysis is carried out from multiple dimensions such as raw material acquisition and preparation, core reaction mechanism, key equipment application to process flow construction, and is the characteristics, advantages and limitations of each process technology comprehensively evaluated. The coke oven gas zero reforming hydrogen metallurgy demonstration project （HyMEX） of HBIS Group is focused on, and its process technology innovation and operation practice is introduced in detail. The HyMEX project successfully applied the "coke oven gas zero reforming direct reduction technology" engineering for the first time, breaking through the international conventional means of using natural gas to produce reduction process gas, and becoming the direct reduction process of gas-based shaft furnace with the highest proportion of hydrogen in industrial production, setting a benchmark for the industrial application of hydrogen metallurgy technology. Combining with China's industrial policy orientation and the characteristics of resource endowment, the development prospect and sustainable development technology path of shaft furnace hydrogen metallurgy in China is deeply discussed. As the world's largest steel producer, China has rich coke oven gas resources, which provides a unique resource advantage for the large-scale promotion of hydrogen metallurgy technology. In the future, with the continuous improvement of the hydrogen energy industry chain and the reduction of costs, hydrogen metallurgy technology is expected to achieve large-scale commercial application in China, so as to promote the steel industry to accelerate the transformation to the green and low-carbon direction, and provide strong technical support for the realization of the "double carbon" goal.

Reasonable operation of the furnace type is the key to its long life, stable operation, and sound economic and technical indicators for the blast furnace. Based on the production data of a certain steel plant's blast furnace, the blast furnace type optimization method was studied, providing scientific guidance for blast furnace operation. First, the Isolation Forest and Boxplot methods were adopted to identify and process noise in the data, and then Principal Component Analysis （PCA） was used for dimensionality reduction to eliminate noise and data redundancy, providing a high-quality data foundation for subsequent cluster analysis. Next, the application effects of two clustering algorithms, K-means and DBSCAN, were compared. The K-means algorithm achieved the best silhouette coefficient when the number of clusters was 14, indicating that the blast furnace type could be divided into 14 categories; the DBSCAN algorithm exhibited a lower Davies-Bouldin Index（DBI） when Neighborhood Radius （E_ps） and Minimum Neighborhood Sample Count（min_samples） were 6.25 and 2, showing the best clustering effect and the ability to effectively identify clusters of any shape, especially suitable for handling the complexity and nonlinearity of blast furnace production data. To evaluate the advantages and disadvantages of different furnace types, an evaluation method for operating furnace types based on comprehensive production indicators was established, selecting coke ratio, fuel ratio, output, and iron loss as key performance indicators and assigning different weights. The results show that the fourth type of furnace type performs the best in terms of blast furnace operation indicators and can be used as the operating target for a reasonable furnace type. To achieve blast furnace type optimization, the implicit relationship between blast furnace operating parameters and furnace types was explored using the Random Forest method, determining the key feature parameters that affect furnace types, including burden matrix parameters, permeability index, gas utilization rate, and standard wind speed. By analyzing the evolution of furnace types and the trend of blast furnace parameters, it is found that the deterioration of furnace types is mainly related to the decrease in permeability, which leads to uneven airflow distribution, reduces gas utilization rate, and increases pressure drop. A new method for optimizing blast furnace type management is established, providing valuable data analysis and operational guidance for on-site personnel, helping to improve blast furnace operation level, reduce energy consumption and costs, and achieve long life, stable operation, and efficient production of blast furnaces.

IF steel is widely used in automobile panel and home appliance panel manufacturing due to its excellent deep drawing performance. Therefore, there are strict requirements for its surface quality, and surface quality defects caused by large-size inclusions are still inevitable problems in the production process. According to the size and distribution of large size inclusions in IF steel, the deformation characteristics of large size inclusions in different positions and sizes during rolling process were studied. The laboratory hot rolling experiment was carried out by the method of prefabricating inclusions in the slab, and the corresponding finite element model was established. The correctness of the model was verified by experiments. At the same time, according to the on-site rolling process, a rolling process evolution model of large-scale inclusions in the surface layer of IF steel slab was established. The deformation law of inclusions with diameters of 0.1, 0.5 and 1.0 mm at different depths from the surface was analyzed. It is found that the closer to the surface, the greater the length change of inclusions along the rolling direction. The deformation rates of inclusions with a diameter of 0.1 mm from the surface of 5, 10 and 15 mm are 11.353,9.884 and 7.859, respectively. The deformation rates of inclusions with a diameter of 0.5 mm are 9.124,8.016 and 7.411, respectively. The deformation rates of inclusions with a diameter of 1.0 mm are 7.906,7.156 and 6.830, respectively. By comparing the deformation law of inclusions with different diameters at the same position, it can be found that the larger the diameter of inclusions with the same depth, the smaller the deformation rate. The deformation rates of inclusions with diameters of 0.1, 0.5 and 1.0 mm from the surface layer 5 mm are 11.353,9.124 and 7.906, respectively. The inclusions deformation rates of 10 mm from the surface layer are 9.884,8.016 and 7.156, respectively. The inclusions deformation rates of 15 mm from the surface layer are 7.859,7.411 and 6.830, respectively. At the same time, it is found that the deformation of inclusions is not obvious when the total reduction rate is less than 30% at the initial stage of rolling, and with the increase of the reduction rate for the rolled piece thickness, the inclusions are obviously elongated along the rolling direction.

The submerged entry nozzle （SEN） is an important limiting link in rare-earth alloyed steel continuous casting,seriously restrict the production efficiency of continuous casting. The nozzle clogging behavior of rare earth microalloying oil casing steel test during continuous casting was studied. SEM-EDS and XRD were used to analyze the chemical composition,phases and morphology of SEN. The results show that the composition of the clogging at the upper,middle and bottom parts of the submerged nozzle is different. The upper part is composed of solidified steel,magnesia-aluminum spinel,CaO·Al₂O₃ （CA） and Ca-RE-Al-O inclusions. The nozzle in the middle part is composed of partially solidified steel and a small amount of magnesium aluminate spinel and CA. The clogging at the bottom of SEN is a mixture of CA and CA₂,solidified steel,silicate and Ca-RE-Al-O inclusions. The most serious clogging layer is at the bottom part of SEN. The cross-sectional channel area at the bottom of the submerged nozzle is reduced by about 66%. The reason for this phenomenon is that the bottom part of the SEN is located in the molten steel. The refractory material at the bottom part of the SEN is scoured by the fluctuation of the molten steel level in the mold. Simultaneously,the slag line will also erode it. Inner and outer walls and outlet of the SEN become rough,and its loose cracks provids good conditions for the adhesion of inclusions. During rare earth microalloying oil casing steel continuous casting process,when rare earth is not added,the SiO and CO gases produced after preheating and decarburization of the SEN react with Al₂O₃ and CA to form liquid silicate phase. Simultaneously,this silicate phase forms CaO-SiO₂-MgO-Al₂O₃ inclusions with MgO and spinel phases in the molten steel,and adheres to the inner wall of the nozzle. Therefore,the internal clogging of SEN is mainly composed of CaO-SiO₂-MgO-Al₂O₃ phase,calcium aluminate （CA,CA₂,CA₆）,solidified steel and magnesia-aluminum spinel. After poured rare earth steel,Ca-Al-O inclusions are modified by rare earth elements into Ca-RE-Al-O inclusions,which are attached to the inner wall of the SEN together with the original inclusions. The thickness of the clogging is increased.

RIST A continuously studied the non-ideal operating lines of blast furnaces from his initial laboratory research to his later theoretical research. He believed that the non-ideal operating line was due to the fact that the residence time t_s of the charge in the furnace was shortened and couldn't reach the critical residence time t_s^* of the ideal reduction state, so that the operating line in the Rist diagram was pushed away from the blast furnace efficiency R point by the envelope curve. Firstly, based on the basic theory of blast furnace ironmaking and the production practices of blast furnaces, the authors of this paper try to make the link between the five parameters, which are used to evaluate the production efficiency of blast furnaces with Rist diagram in terms of mathematical relations. The residence time t_s of the charge in furnace is replaced by t_g of the gas in furnace, and then, the relationship among t_g, the bosh gas volume index χ_BG, the bosh gas volume V_BG and bosh gas volume per ton of hot metal $v_{\mathrm{O}_{2}}$ is shown. The relationship between t_g and R point of gas residence time is very complicated, which needs a large number of actual measurement data of the process in the blast furnace and can be determined by mathematical model and computer calculation. However, there are few researches in this field, and there are still many difficulties in its application in production practice. Secondly, in order to solve the operation problem in the actual non-ideal state conveniently and quickly, a method to calculate the envelope curve is suggested based on the operation data of blast furnaces. Since R point is significantly related to the gas utilization rate η_CO, the position of R point can be determined by the level of the gas utilization rate η_CO. During the on-site calculation of blast furnaces, the Rist operating line is often determined by the gas utilization rate η_CO and the tuyere oxygen consumption per ton iron $v_{\mathrm{O}_{2}}$. Therefore, the change of the gas utilization rate η_CO, which determines the change of the operation line, can be obtained by the change of the tuyere oxygen consumption per ton iron $\mathcal{U}_{\mathcal{O}_2}$ according to the method of analyzing production data. It also can obtain the characteristics and the change of the envelope curve in the Rist diagrams. The change of important parameters of the Rist model in actual production can predict the change of blast furnace condition.

At present, the classical K-M（Koistinen-Marburger） model is commonly used to describe the martensite transformation kinetics in steel, but the accuracy of the model is closely related to the composition of the steel. Based on quenching experiments with different cooling rates, the martensite transformation kinetics of common medium-carbon high-silicon quenching-partitioning（Q&P） steels were studied by expansion method and metallography method. Meanwhile, an improved martensite transformation kinetic model suitable for medium-carbon high-silicon Q&P steels was established based on the traditional K-M model and verified. The results show that under different cooling rates, the martensite transformation kinetic curves of medium-carbon high-silicon Q&P steel are "S" shape, not "C" type. The phase transformation process is divided into the acceleration period at the beginning, the high-speed period in the middle, and the deceleration period in the end, which may be caused by the self-tempering phenomenon of martensite. In addition, the martensite formed near the martensite start temperature is relatively coarse, and carbon atoms diffuse from the supersaturated martensite to the surrounding unconverted austenite at the relative high temperature. The carbon enrichment of austenite increases the stability of remaining austenite, and the supercooling degree for the further martensite transformation needs to be further increased, thus reducing the martensite start temperature of the remaining austenite. The equation of martensite transformation kinetics index β is a constant of 1-2. The sensitivity of β value to quenching temperature depends on the carbon content of steel. When the carbon content increases, the sensitivity of β value to quenching temperature decreases significantly and can be basically ignored. The rate parameter α is a cubic polynomial function of the quenching temperature. With the increase of cooling rate, the rate parameter α gradually decreases, indicating that the martensitic transformation may be a time-dependent phase transformation. The equation index β gradually increases with cooling rate, which is related to the suppression of austenite plastic accommodation on martensite transformation. Considering the instantaneous dynamics of martensite transformation, the improved K-M model has a better match with the experimental data than the traditional K-M model.

Introducing irreversible hydrogen trap into steel is a common method to improve the hydrogen embrittance resistance of structural steel. In order to reveal the hydrogen trap characteristics of TiN precipitated phase interface in high strength steel based on α-Fe matrix, based on the microscopic analysis of TiN/α-Fe interface, the hydrogen trap properties of 0.21Ti-0.08N-Fe （mass fraction,%） materials with different TiN/α-Fe interface misfit were characterized by thermal desorption spectroscopy, and the hydrogen adsorption strength of the hydrogen trap at the TiN/α-Fe interface was simulated by first principles simulation calculations to explore the mechanism of hydrogen adsorption at the hydrogen traps on the interface. The results show that the characteristics of desorption peaks at low temperature are very similar in the four samples with different TiN/α-Fe interfaces. The peak at middle temperature is positively correlated with the content of semi-coherent interface in the sample, and the peak at high temperature is positively correlated with the content of TiN/α-Fe interface in the sample. The sample with the most coherent TiN/α-Fe interfaces has the most irreversible traps, and the binding ability of different interfaces to hydrogen atoms is in the order of coherent interface>semi-coherent interface>non-coherent interface. The simulation calculation results show that the octahedral gap, mixed tetrahedral gap and pure iron tetrahedral gap are all effective binding sites for hydrogen atoms on the coherent TiN/α-Fe interface with B-N orientation relationship, and the octahedral gap has the lowest hydrogen binding energy （-0.10 eV）. The hydrogen binding energy of the mixed tetrahedral gap closer to the interface （-0.04 eV） is lower than that of the pure iron tetrahedral gap （-0.01 eV）. The variation of atomic spacing and charge density distribution around the interstitial gap before and after hydrogen atoms are dissolved shows that the stress field generated by lattice mismatch at the α-Fe side of the interface can promote the binding of the three interstitial gaps, especially the octahedral gap, to the hydrogen atoms, which can effectively hinder the diffusion of hydrogen in the steel. The properties of TiN/α-Fe interface in steel can be controlled by proper heat treatment, the content of irreversible hydrogen trap can be increased, and the hydrogen diffusion coefficient can be reduced, which is beneficial to improve the hydrogen embrittance resistance of microalloyed structural steel.

Bearings are one of the most critical foundational components in the rotating parts of various mechanical equipment. As they are often used at key points such as the heart and joints of the main machine, the quality and fatigue life of the bearings are crucial to the overall performance and reliability of the primary equipment. As the total oxygen content in bearing steel decreases, the size and number of oxide inclusions in the steel are effectively controlled. Consequently, the impact of TiN inclusions on the fatigue life of bearing steel becomes more pronounced, leading to stringent control requirements for Ti content in bearing steel. Compared to controlling Ti content through raw materials and alloys, achieving low Ti content in bearing steel through slag-steel reactions during the refining process offers a more cost-effective solution. Based on thermodynamic calculations and the liquidus temperature of slag, the composition range of CaO-SiO₂-Al₂O₃-0.05%TiO₂-5%MgO（mass fraction） refining slag to control ultra-low Ti content in bearing steel was studied. The effects of refining slag basicity and Al₂O₃ content in the slag on the Ti and Al contents in the steel, TiN size distribution, and steel cleanliness was investigated by slag-steel reaction. The results indicate that 25%-58% Al₂O₃ containing slag with the basicity of 2-4 can effectively control the Ti and Al contents in the steel [w（[Ti]）<0.001 2%、w（[Al]）<0.015 0%]. As the basicity of the refining slag decreases, the Ti and Al contents in the steel decrease, and the slag with the basicity of 3 meets the expected requirements for Ti and Al contents. The low-basicity refining slag is beneficial for controlling TiN inclusions in steel, proving the feasibility of the slag design. As the basicity of the refining slag increases and the Al₂O₃ content decreases, the number density and average size of inclusions in the steel decrease, consistent with the trend in the oxygen content. For refining slags with the same basicity, as the Al₂O₃ content in the steel decreases, the ability of slag to absorb inclusions increases, resulting in higher steel cleanliness. The 48.71%CaO-16.24%SiO₂-30%Al₂O₃-0.05%TiO₂-5%MgO（mass fraction）refining slag can effectively control Ti content and TiN inclusions in the steel, and the higher cleanliness is achieved.

At present, the high-grade wear-resistant steel with high additional value is still relied on imports to make up for the market demand in China. This leads to problems such as increased maintenance cost and time cost of maintenance and replacement, and limited technical support. Therefore, from the perspective of saving energy and improving economic benefits, it is urgent to develop new wear-resistant steel with low cost and high wear resistance. The microstructure and properties of newly developed HB500 grade low alloy high strength wear-resistant steel were studied by means of optical microscope, scanning electron microscope, transmission electron microscope, X-rays diffraction, tensile test, impact test and sliding wear test , and compared with commercial Hardox450 steel. The possibility of HB500 steel replacing Hardox450 steel in sliding wear condition was evaluated according to their composition and performance. The results show that the alloy content of HB500 steel is low with respect to composition. In terms of mechanical properties, the tensile strength of HB500 steel is 1.25 times that of Hardox450 steel, and the low-temperature impact toughness is 66% of Hardox450 steel. With regard to wear performance, compared with Hardox450 steel, the relative wear degrees of HB500 steel at 10, 50, 90 N are 89.7%, 90.8% and 99.0% respectively, indicating that HB500 steel is more wear-resistant under lower load, while the wear degree under high load is comparable to that of Hardox450 steel. Therefore, HB500 steel can replace commercial Hardox450 steel from the perspective of composition and performance. Moreover, different from the reported results, when the load increases from 10 N to 50 N, the mass loss increases significantly, however, when the load further increases to 90 N, the mass loss is less than that under 50 N load. In addition, the friction coefficient decreases with the increase of load and material hardness, but the friction coefficient is more sensitive to load than hardness. The research results provide a reference for the development of new wear-resistant steel with low cost and high wear resistance, which can replace commercial Hardox450 steel.

In the production of high-quality strip, the phenomenon of performance difference in the wide direction of hot-rolled high-strength strip has a greater negative impact on its quality stability control in the cold rolling process, which is one of the main reasons for restricting the accuracy of strip shape control of this type of product, and also one of the bottlenecks restricting the further thinning of the specifications for this type of the strip. For such problems, taking 1 780 mm strip cold rolling mill as a prototype, a three-dimensional cold rolling simulation model of high-strength strip was established based on the elastic-plastic finite element method, taking into account the differences in the distribution of the wide direction for performance of the rolled strips. The calculated value of thickness distribution in the wide direction and the measured thickness distribution had a high degree of consistency. The relative error between calculated value and measured value of rolling force in the stable rolling stage was controlled with in ±6%, and the relative error between caculated value and measured value of center thickness in wide direction was controlled with ±0.2%. Through the numerical simulation of wide direction performance differentiation, the influence of wide direction performance difference on the three-dimensional deformation of rolled metal, rolling pressure distribution and strip shape regulation were analyzed, and the influence of such differences on the plate convexity and strip shape were described. The results show that the three-dimensional distribution of rolling force between the work rolls and the strip in the contact deformation zone is highly similar to the distribution trend of original mechanical properties of the strips, while the rolling force of the homogeneous model is nearly consistent throughout the strip width range. The inherent differences in the wide direction performance result in an asymmetric influence of the actuators on the adjustment of the crown and flatness. The strip shape control becomes more challenging as the difference in deformation resistance between the center and the edge of the strip increases, and becomes more difficult as the average deformation resistance in the wide direction of the strip increases. Under the same conditioning process, the flatness actuators are less capable of conditioning the shape of strips with primitive differences in wide direction properties than that of homogeneous strips, which ultimately leads to deviations in strip shape conditioning.

In the iron and steel industry, iron ore resources are stuck and it urgent needs to reduce costs and increase efficiency, how to optimize the allocation of iron ore resources to achieve safe, low-carbon and high-quality development of the iron and steel industry is a very important issue. Laboratory experiment research, big data analysis, mathematical model construction and other research methods were used to carry out research on integrated ore blending technology based on multi-objective system optimization of ironmaking, aiming at developing integrated ore blending technology from the whole process of ore blending-sintering-blast furnace, realizing cross-process collaborative optimization of ironmaking system, and providing effective guarantee for iron and steel enterprises to reduce cost and increase efficiency. The results show that a large database of mineral powder properties is built based on the basic experimental study of mineral powder, and a prediction model of sinter properties is constructed by using neural network according to the model prediction results. The model can be used to predict the sinter drum strength, low-temperature reduction powdering index and chemical composition, and the fitting effect of model prediction is better. The prediction model and error tracing model of BF furnace condition index based on RBF neural network were established. Through error tracing and parameter optimization model, the specific contribution rate of operating parameters to fuel ratio fluctuation could be accurately calculated, and the standard value of parameters obtained by the optimization model could be replaced, which could realize the precise regulation of bottleneck factors causing the fluctuation of BF core economic index. An integrated ore blending model with cross-process coupling through ore blending-sintering-blast furnace process was established. The application in A steel plant shows that a more advantageous alternative scheme is obtained through the calculation of the integrated ore blending model. Compared with the original scheme, the fuel ratio of blast furnace is reduced by 1.6-15.8 kg/t, the carbon emission of ton of iron is reduced by 5-45 kg, and the benefit of ton of iron is 10-50 yuan.

Cold rolled low alloy high strength steel （HSLA） is one of the most successful steel grades in the development of automotive high strength steel in recent years. To meet the requirements of automotive lightweight and safety development, steel mills are actively developing higher grades, of which H800L, a typical representative is widely used in structural parts such as seat sliders, door sill parts and anti-collision beams. Aiming at the problem of low batch performance of cold-rolled low alloy high strength steel H800L in industrial production, traceing back to the cooling process after the hot rolled coil is off-line. Starting from the variable of different cooling methods, the reasons for the performance differences are explained through the evolution law of microstructure. Optical microscope （OM）, transmission electron microscope （TEM） and energy dispersive spectrometer （EDS） were used to study the effect of the cooling mode of hot rolled coil on the microstructure of hot strip and continuous annealing plate. With the help of comparative analysis of acid rolling force, the difference mechanism was elaborated by focusing on the type, size and distribution of microalloyed second phase precipitates, and the root cause of the low performance of continuous annealing products was revealed. Slow cooling inside the wind barrier makes the microalloy second phase precipitate NbTiC mature and promotes the ferrite grain growth of the hot plate, and the large particle NbTiC during semi-annealing has no obvious inhibitory effect on the recrystallization of the cold rolled ferrite fibrous structure, and a large amount of polygonal ferrite appears in the continuous annealing structure, which is the root cause of the unqualified of the properties of the continuous annealing plate. The natural cooling mode in the warehouse area makes the precipitates of the second phase more fine and dispersed, that refines the microstructure of the hot plate, and inhibits the semi-annealed recrystallization behavior of the cold-rolled ferrite fiber. The semi-annealed structure with a large amount of distortion energy and deformation dislocation is the key to ensure high strength.

Digital and intelligent technologies are driving the intelligent transformation of blast furnace ironmaking in China, emerging as a kind of new quality productive forces. Nowadays, using the universal large language models （U-LLMs） as a base framework to build industrial vertical large language models （V-LLMs） for guiding industrial production via secondary training with domain-specific corpora has become a new trend. Despite the emergence of V-LLMs for the entire steelmaking process, research on V-LLMs specifically for blast-furnace operations is still in its infancy. By reviewing the recent evolution of blast furnace ironmaking intelligence, a new idea of its paradigm reconstruction and fusion driven by V-LLMs was proposed. Classifying the blast furnace V-LLM tasks scenario into scheduling and decision making, the "Data-Application-Perception" penetration and application path is presented for the first time. Also, 5-dimensional evaluation system for future performance assessment and optimization is puts forward, including process understanding, safety and reliability, knowledge transfer, real-time performance, and continuous learning. Then, 3 kinds of new paradigms for intelligent upgrade driven by blast furnace V-LLMs are discussed, including blast furnace condition characterization, blast furnace condition metaverse, and multi-scene fusion. A 3-dimensional collaborative deep representation architecture of "Physical↔Virtual↔Perception" with blast furnace V-LLMs as the core and a new concept of “blast furnace portrait” are proposed. The construction route of blast furnace condition metaverse and the policy of multi-scene fusion are sorted out and discussed. Finally, the key issues and possible solutions in the future development of blast furnace V-LLMs are analyzed. Focused on the feasibility of blast furnace V-LLMs in construction, application, and evaluation, the paradigm reconstruction of intelligence update driven by V-LLMs in the context of industry development is discussed. It aims to offer theoretical guidance for the deep application of V-LLMs in China's blast furnace ironmaking and further promote its intelligent transformation and development.

High-strength ferrite-martensite dual-phase steels usually suffer from low elongation and fracture strain. To solve this problem, a Ti-bearing low carbon DP steel was designed to prepare a 980 MPa grade DP steel with excellent elongation and fracture strain by narrowing the strength difference between ferrite and martensite as well as refining the grains. Based on the design steel, the effect of the annealing temperature （780, 80, 800 ℃） on microstructure and mechanical properties was further studied. It is demonstrated that the ferrite volume fraction decreases from 57% to 32% and the ferrite grain size decreases from 2.1 μm to 1.6 μm for the experimental steel as the annealing temperature is increased from 760 ℃ to 800 ℃. Regarding the mechanical properties, the ultimate tensile strength increases from 983 MPa to 1 081 MPa, the total elongation decreases from 17.6% to 13.9%, and the fracture strain increases from 0.41 to 0.62 for the experimental steels as the annealing temperature is increased from 760 ℃ to 800 ℃. The increasing annealing temperature increases the martensite volume fraction and therefore reduces the carbon content in martensite, which in turn reduces the ferrite-martensite strength difference, promotes the coordinated deformation ability between the two phases, and ultimately inhibits the ferrite-martensite interface decohesion. Moreover, the reduced martensite carbon content also improves the martensite toughness, thereby inhibiting martensite fracture. The combined effect of these two factors is the main reason for increase in fracture strain of experimental steel with increasing annealing temperature. In addition, compared with the reported DP steels, the 800 ℃ annealed experimental steels exhibit higher fracture strains at identical ultimate tensile strength. This can be attributed to three factors. Firstly, TiC particles reduce the strength difference between ferrite and martensite, promote the coordinated deformation ability between the two phases, and thereby suppress the ferrite-martensite interface decohesion. Secondly, the combination of low carbon content and high martensite volume fraction reduces the martensite carbon content, which improves the martensite toughness and thus suppresses the martensite cracking. Finally, TiC particles refine the grains and further improve the matrix toughness.

Under the background of "double carbon", the recovery of waste heat from high temperature oxidized pellets becomes an energy saving potential point in steel production. Pre-reduction and cooling of oxidized pellets using H₂ can not only improve the quality of pellets, but also reduce the energy demands of subsequent processes. The exergy analysis method is adopted to quantitatively evaluate the energy utilization of the new process. The effects of H₂ content in the cooling gas and oxidized pellet temperature on the effective energy utilization efficiency of the new process were investigated. Based on this, experiments were conducted, and the following conclusions were obtained. Under the condition of 100% H₂ （volume fraction）and 1 000 ℃ of oxidized pellets, the maximum metallization rate of pre-reduction pellets can reach 32%. The demand for H₂ is 866.53 m³/t（oxidized pellets）. The hydrogen utilization rate, energy efficiency, and general and objective exergy efficiency are 25.55%, 25.46%, 92.03% and 22.11%, respectively. When the volume fraction of H₂ in the cooling gas decreases from 100% to 60%, the demand for cooling gas decreases 315.77 m³, but the general exergy efficiency decreases by 6.54%. As the temperature of the top gas increases, the proportion of hydrogen should not be lower than 70%. When the temperature of the oxidized pellets increases from 950 ℃ to 1 150 ℃, the demand for hydrogen increases by 140.95 m³, and the metallization rate of the pre-reduced pellets increases from 30.50% to 38.51%. However, the utilization rate of hydrogen decreases, and the general and objective exergy efficiency decreases. Under the condition of 100% H₂ （volume fraction）and 1 000 ℃ of oxidized pellets, the metallization rate of the pre-reduced pellets reaches 34.77%, and the compressive strength and drum index are 1 902 N/pellet and 98.21%, respectively, meeting the production requirements of subsequent processes.

The catalytic purification of carbon monoxide （CO） from sintering flue gas in the steel industry has attracted increasing attention in recent years due to its unique advantages in energy conservation and environmental protection. However, challenges such as catalyst poisoning and barriers to large-scale implementation have so far prevented the realization of practical engineering applications both domestically and internationally. An industrial-scale CO catalytic purification project implemented on a 435 m² sintering machine at Handan Steel was reported, handling the full flue gas volume of 1.6×10⁶ m³/h （standard condition, wet basis）. The project employed noble metal honeycomb catalysts loaded into the spare layer of the original denitrification （DeNO_x） tower, achieving CO reduction without the need for additional external equipment. Moreover, the heat released from CO oxidation significantly reduced the consumption of coke oven gas required for flue gas reheating during catalytic denitrification. Results from 4 months of operation show stable overall performance, with CO catalytic conversion efficiency ranging from 76% to 85%, CO emission concentrations between 1 070 and 2 365 mg/m³ （well below the current environmental limit of 2 800 mg/m³）, flue gas temperature increase of 33-55 ℃, and a coke oven gas saving rate of 63% to 100%. Based on continuous monitoring data, it analyzed how flue gas temperature, flow rate, and the presence of other pollutants affect the CO catalytic performance. Special attention was given to system performance during key operational phases, including initial start-up, temporary shutdowns, and switching of flue gas circulation. The findings indicate that the current system is resilient to operational fluctuations and is capable of achieving both compliant CO emissions and complete coke oven gas savings. This translates to an energy consumption reduction of 3.4 kg of standard coal per ton of sintered product. An engineering demonstration system for catalytic purification of CO in sintering flue gas was established, providing an industrial-scale practical paradigm for synergistic multi-pollutant control in the steel industry. Furthermore, it offers a technical foundation for advancing the coordinated optimization of energy conservation, emission reduction, and cleaner production in sintering processes.