Vanadium titanium magnetite is a featured strategic metal resource in China. The existing mainstream of vanadium extraction at home and abroad is the blast furnace ironmaking-converter process, which has high carbon emissions and low recovery rate of vanadium and titanium. A large amount of titanium element enters blast furnace slag and accumulates over 100 million tons, which not only wastes resources, but also significantly increases the pressure of environmental protection. The existing non-blast furnace smelting processes to make up for the shortcomings of the blast furnace process are introduced, including direct reduction process and smelting reduction process, and the process flow and application status are summarized. The principles, application status, advantages and disadvantages of titanium extraction methods of titanium-containing slag at home and abroad, such as modified enrichment, carbonization-chlorination and hydrometallurgical extraction, are summarized. In addition, the future development for comprehensive utilization of vanadium titanium magnetite is prospected. It is considered that the full-process technology of hydrogen-based shaft furnace reduction-electric furnace melting separation-comprehensive utilization of titanium slag for vanadium titanium magnetite holds tremendous development prospects. This technology can strongly support China's vanadium titanium steel industry in achieving the "dual carbon" goals.

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

The steel industry is an important construction foundation and industrialization support for the development of the national economy, while also directly affecting the living standards and national security of the people. To actively respond to China′s "carbon peak, carbon neutrality" and sustainable development policies, the future transformation direction of the Chinese steel industry will focus on high-quality development, green production, intelligent manufacturing, and enhancing international competitiveness, in order to achieve the goals of carbon reduction and sustainable development. Blast furnace ironmaking is an important part of steel production, with a complete automation system that generates a large amount of production data. In order to serve the intelligence of blast furnace ironmaking and promote the sustainable development of blast furnace ironmaking with these data. Data cleaning through data management technology can enhance data quality and provide a reliable basis for subsequent analysis. Based on the important parameters in the production process, the digital twin model of key variables is established by using big data analysis and artificial intelligence technology. Real-time monitoring, analysis and prediction can be carried out for multiple targets in the smelting process, combined with intelligent control strategies and optimization algorithms to achieve multi-objective collaborative optimization, which can improve production efficiency and reduce costs under the premise of ensuring production safety. The intelligence level and production efficiency of blast furnace ironmaking can be further improved by using data middle platform to integrate, analyze, apply and share the large amount of data generated by blast furnace ironmaking. Finally, the issues in the intelligentization of blast furnace ironmaking were summarized, and solutions were discussed in the conclusion. These insights provide guidance for the industry′s transformation towards intelligence and contribute to the sustainable development of the steel industry.

The cold rolling of high-grade thin-gauge silicon steel is prone to edge cracking, difficult deformation, and difficult shape control, so it has always been produced by a single-stand 20-high mill in a reversible rolling process, resulting in relatively low production efficiency and benefit. In recent years, both domestic and foreign countries have begun to explore the basic equipment for the cold continuous rolling production process of high-grade thin-gauge silicon steel. China has also taken the lead in rebuilding or newly building the silicon steel-specific cold continuous rolling production line with four stands, five stands, and six stands based on six-high mill. The roll profile, roll diameter, and roll system structure are all different, which brings confusion to the design of new similar projects. In order to study the specific rolling mill structure suitable for high-grade silicon steel cold continuous rolling mills, the following work was carried out. Firstly, 35WD1900 hot-rolled silicon steel plates was oampled and the stress-strain curve of the silicon steel was obtained through simulated continuous rolling experiments and normal temperature tensile experiments. Then, for the 1 500 mm UCMW mill, a finite element simulation model of single-stand rolling and simulated continuous rolling with integrated roll system was established based on the ABAQUS platform. Through a large number of working condition simulations and comparisons, it is determined that the optimal roll diameter range of the work rolls of the continuous rolling mill portal stand is between 320 mm and 360 mm, the optimal roll diameter range of the work rolls of the intermediate stand is between 300 mm and 340 mm, and the optimal roll diameter range of the finished stand work rolls is between 300 mm and 340 mm. At the same time, in the cold continuous rolling process, the five-stand continuous rolling has always been the mainstream choice. The influence rules of five-stand, six-stand, and seven-stand continuous rolling on the crown inheritance and evolution of the rolled strip were deeply compared. Comprehensively considering the economic cost, it is concluding that the six-stand is the better choice. Finally, the roll profiles of the intermediate roll and work roll are optimized for the continuous rolling production of high-grade silicon steel. The research results have reference value for the design of high-grade thin-gauge silicon steel cold continuous rolling mills and provide guidance for the improvement and optimization of silicon steel continuous rolling technology.

In order to provide theoretical basis for process optimization and quality control of the welding of clad plate, the structural characteristics, preparation technology and welding process of stainless steel clad plate are reviewed. Firstly, the layered characteristics of the stainless steel clad plate are analyzed, and the common preparation methods of the clad plate are introduced. Then, the welding characteristics and technical difficulties of stainless steel clad plate are analyzed. According to the structural design of welded joint of stainless steel clad plate, the influences of welding methods, welding materials, welding groove, welding sequence and pre-welding/post-welding treatment on the microstructure and properties of welded joint are discussed. The structure evolution of welding process and its relationship with the properties of welded joints are analyzed. The research status of welding performance control of stainless steel clad plate is summarized. Furtherly, on the basis of the development of welding technology, new methods, new materials for welding stainless steel clad plate are discussed. The numerical simulation method and its application for the study of welding properties are described. Finally, the welding method and performance control of stainless steel clad plate are prospected.

Lightweight is an important path for the automotive industry to address the air pollution problems and deliver on the goals of carbon peaking and carbon neutrality. The medium-manganese low-density steel, with Mn mass fraction of 3% to 12%, has low costs and good processing performance, showing excellent potentials for development and application in the field of automotive steel. The strengthening mechanism of medium-manganese Fe-Mn-Al-C low-density steel was systematically introduced based on the current research status at home and abroad, while the influence and mechanism of heat treatment process on the mechanical performance and strengthening mechanism of medium-manganese low-density steel were comprehensively summarized. In addition, the stability of residual austenite during deformation process was discussed. The characteristics of quenching and partitioning (Q&P) were analyzed according to the development process and current situation. The strengthening mechanism for quenched and proportioned steel was explored along with the influencing factors of mechanical properties of medium-manganese steel from such perspectives as heating temperature, quenching temperature, partitioning temperature and partitioning time. Based on the urgent need of boosting the comprehensive performance of medium-manganese Fe-Mn-Al-C lightweight steel, and on account of its element composition and microstructure characteristics, the volume fraction and stability of residual austenite in medium manganese Fe-Mn-Al-C low-density steel can be increased by Q&P process, as well as the mechanical performance will be enhanced, is proposed. The future research directions deserving attention need to be paid attention, firstly, reasonable Q&P process need to be controlled to avoid the precipitation of coarse κ-carbides in steel; secondly, the synergistic effect between κ-carbide strengthening and TRIP effect in medium-manganese need to be explored; finally, the effect of Q&P process on the size of original austenite grains and the non-uniformity of the martensitic structure during the phase transformation process needed to be analyzed, as well as the effect of different substructure characteristics of martensite on the nucleation sites and morphological features of residual austenite, so as to provide reference for the popularization, optimization and improvement of the production process.

The iron and steel manufacturing process is a manufacturing system integrated through the coupling of multiple procedures. Its physical essence lies in the fact that the ferrous substance flow, driven and influenced by the energy flow, undergoes a series of complex physical and chemical conversions or transformations to produce steel products. The substance flow, energy flow and information flow are mutually coupled and operated in synergy in the process, and dynamic operation is the predominant characteristic of the process. The steel manufacturing process operates far from an equilibrium state, characterized by nonlinear coupling and being an open irreversible process that entails the dissipation of matter and energy. The steel metallurgy engineering design is a systematic integration and optimization endeavor based on research findings in fundamental science, technical science, and engineering science pertinent to steel plant design. Contemporary steel metallurgy engineering design is guided by principles of engineering philosophy as well as metallurgical process engineering theory. It involves the judicious selection and systemic integration of metallurgical processes and technical equipment to establish a rational workflow with advanced structures, optimized functions, efficient operations, and competitive engineering solutions. At its core, contemporary steel manufacturing engineering design aims to achieve integrated objectives encompassing systematization, structuring, functional enhancement, high efficiency, sustainability, greenization, and intelligence throughout the entire project while pursuing structural integrity, functional efficacy, operational efficiency, and multi-objective optimization within the metallurgical processes. The connotations and methods of concept design, top-level design and dynamic precise design of the new generation steel plants are discussed, and the innovation and practical effects of the engineering design of Shougang Jingtang Steel Plant are expounded.

The changes of China's annual crude steel output, average daily crude steel production on a monthly basis over the past two years, end-of-month rebar prices, direct steel exports, indirect exports of steel products, and CO₂ emissions were reviewed and analyzed. It is concluded that China's crude steel production is generally in a situation of oversupply, and the steel industry has entered a downward phase of reduction fluctuations. Under the premise of no significant increase in crude steel output, China's steel industry can be considered to have entered a CO₂ emission stabilization period. The study explores targets and measures for total crude steel output control from perspectives including future production forecasts, supply-side structural reforms, and adjustments to import/export policies. By integrating projections of future crude steel output and scrap resources, it is proposed that under the goals of "Carbon peak and Carbon neutrality", China's steel industry will gradually develop three typical manufacturing processes: BF-BOF long process, full scrap EAF process, and hydrogen reduction-EAF process. The evolutionary alternation of these three processes is discussed, emphasizing that China's steel industry should leverage the "Carbon peak and Carbon neutrality" context to guide scrap resources toward EAF process, thereby gradually optimizing the sector's ferrous resource structure, product structure, and process structure. Pathways for enhancing manufacturing continuity are explored through interface technology optimization, dynamic precision design, and full-process intelligentization. Finally, through the construction and analysis of a "dual carbon" analytical model for the steel industry, the study identifies controlling and reducing crude steel output as the most effective decarbonization measure, with process structure optimization in steel plants being equally critical.

The steel industry is an important foundational industry of the national economy. The traditional engineering design theory faces significant challenges in promoting high-quality development of the steel industry. Metallurgical process engineering theory is an important theoretical basis for guiding the high-quality development of steel industry in the new era. The application of metallurgical process engineering theory in the integrated steel plant engineering was introduced. It is to construct a static system and achieve dynamic-orderly,coordinated-continuous,and stable-efficient operation of material flow,energy flow,and information flow by thoroughly studying the manufacturing physical system,optimizing its parameters,adopting green "interface technology", and determining the steady-state optimization goals of the physical system. By applying the metallurgical process engineering theory,a "compact" steel manufacturing process was created for the Han-Steel Project. And the impact of ultimate design on production operation, efficiency, energy conservation, pollution reduction, and carbon reduction was determined. Han-Steel New Area covers an area of 0.42 m² per ton of steel,a comprehensive energy consumption of less than 546 kg standard coal per ton of steel,a new water consumption of 2.5 t per ton of steel,and CO₂ emissions of less than 1.57 t per ton of steel,becoming a model for energy conservation and carbon reduction in the steel industry. The ultimate design of integrated steel plant based on metallurgical processes theory has laid the foundation for the enterprise to achieve a world-class factory that is "efficient,green,and intelligent".

Tangsteel New Area is a new generation of process steel plant designed and constructed by HBIS Group in accordance with high-quality development and green low-carbon transformation with the construction goal of "green, intelligent and branding", taking advantage of the opportunity of location adjustment. In the engineering design of Tangsteel New Area, the traditional static design of steel plant based on static capacity estimation of each process/device and different surplus coefficient assumption is abandoned, and the dynamic and accurate design of steel plant is used to construct the cyber-physical system of Tangsteel New Area under the guidance of metallurgical process engineering, laying a solid foundation for the optimization of the static structural framework of physical space and dynamic running path, trajectories and time-space boundaries. In order to implement the principle of dynamic and precise design, a series of digital technologies are used to build factory database platform, and integration planning schedule, system of whole processes dynamic scheduling, whole process digitalization, equipment intelligent operation and maintenance, and energy fine management system in the cyberspace. Through the mutual mapping, real-time interaction and efficient collaboration of the human, machine, material, method and environment in the cyberspace and the physical space, the resource allocation and operation in the cyber-physical system can respond on demand, quickly iterate and dynamically optimize, so as to solve the complexity and uncertainty problems in the process of production, manufacturing, and energy dissipation, then the material flow can be matched and equalized dynamically, stably and equably over a long period of time, the overall running time of the whole process and the energy consumption of the process can be minimized. Tangsteel New Area has contributed a green smart steel plant to the industrial upgrading of the metallurgical industry and the development of new quality productivity.

Shougang Jingtang Company follows the theory of metallurgical process engineering and has constructed a new generation recyclable steel manufacturing process with dynamic and orderly, continuous and compact, and efficient and stable production by analyzing and integrating the metallurgical functions of each unit production process in the production process. It adopts advanced "blast furnace-converter" and "continuous casting-hot rolling" interface technologies, as well as generic technologies such as hot metal pretreatment, matching between converter and continuous casting machine, optimizing and matching of steel refining, and high-efficiency continuous casting, to build a clean steel platform with high efficiency, low-cost, and stable production of high-quality steel. Through the continuous improvement of the scheduling model for the blast furnace-converter interface, the number of iron ladle turnover times has gradually increased from 3.8 times per day to more than 5.8 times per day, the temperature drop of hot metal has gradually decreased from 108.3 ℃ to 85.7 ℃, and hot metal charging accuracy (-0.5-0.5 t) has remained stable at over 98.5%. The continuous casting-hot rolling interface is based on the integrated platform of production and marketing, through the optimization of the rolling plan, the reduction of the blocking rate of the slab, and the online quenching technology of the slab, the hot charging rate of the hot rolling production line reaches 64.84%, and the hot charging rate of the medium-thick plate production line reaches 62.9%. In terms of specialized production, through reasonable optimization of process layout and differentiated equipment, specialized production lines with their own characteristics have been formed. The production line, represented by automotive sheet and tinplate, uses high efficiency production and low oxygen control technology throughout the entire process, to control the treatment time of KR, the treatment time of converter and the vacuum treatment time of RH within 32.2, 35, 20 min, respectively. The casting speed of peritectic steel is increased to 1.7 m/min, the casting speed of tinplate is up to 2.0 m/min, basically achieving the matching between converter and continuous casting machine. The oxygen mass fraction of molten steel in the tundish is reduced from 0.002 8% to 0.001 5%. The thin slab casting and direct rolling line represented by MCCR achieves efficient and stable production of ultra-low sulfur steel with w([S])≤0.001 2%, and low carbon and low silicon steel grades with w([Si])≤0.03%, w([S])≤0.001 5%, w([C])≤0.01%, and w(T[O])≤0.001% through ultra-clean steel technology. The surface quality of the pickled strip steel reaches the level of cold-rolled FB surface quality. For the medium-thickness plate production line represented by 9Ni steel, the slag system with ultra-high phosphorus distribution ratio and high-efficiency deep desulfurization, nitrogen, oxygen, hydrogen and inclusion control technology have been developed. The sum mass fraction of the five impurity elements (P+S+N+H+O) is as low as 0.004 01%. By using the slab heavy reduction technology, the center porosity of 300 mm and 400 mm thick slabs is not greater than 0.5 grade. Shougang Jingtang Company fully leverages the advantages of the new generation process, led by strategic products such as automotive sheet and tinplate, and has achieved first-time launches of a number of product technologies, realizing the brand concept of "making the best steel".

In the process of steelmaking and continuous casting,there will be many disturbances,resulting in the scheduling can not be carried out according to the original plan in many times,so it is necessary to adopt real-time scheduling strategy for dynamic scheduling of steelmaking and continuous casting production process. In order to ensure the stability of steelmaking and continuous casting process,a dynamic adjustment method based on "adjustable" buffer time and Flexsim backward working method was proposed. The rescheduling job plan was generated by adding restrictions such as crane rules,equipment selection rules,and ladle quantity limits. Through the optimized dynamic scheduling scheme,the influence of the disturbance in the process of steelmaking and continuous casting was well eliminated. In addition,comparing the present research scheme with the manual scheduling in terms of evaluation indexes such as equipment utilization,degree of continuity and production cycle time,the average production cycle time was reduced by 7.9 min and the degree of continuity was increased by 8.8%. The results show that this method can not only dynamically generate specific scheduling schemes based on rules and Flexsim,but also significantly improve the related indexes of the process,which provides a theoretical basis for Flexsim to guide field production in the future.

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

The hydrogen metallurgical electric furnace process is an important starting point for the steel industry to achieve green and sustainable development due to its potential to achieve nearly zero carbon emission steel production. The direct reduction iron provided by hydrogen metallurgy needs an electric furnace to obtain the ideal steel material because it is not a terminal product. The electric furnace process technology has been mature,but the technological breakthrough of the hydrogen metallurgy process is still a big challenge. The hydrogen metallurgy process is widely regarded as a frontier disruptive technology. Most of the domestic hydrogen metallurgy demonstration projects are in the industrial test stage,and there is still not enough to achieve the realization of real industrialization. The evaluation of the technology readiness of the hydrogen metallurgy process is helpful to scientifically understand its development history,evaluate its development status,and expect its future development trend. Based on the technical readiness criteria and process analysis,the technical readiness evaluation criteria and detailed rules suitable for hydrogen metallurgy processes were studied to evaluate and prospect the four kinds of hydrogen metallurgy processes. The results show that the comprehensive evaluation of the direct reduction process of a hydrogen-based shaft furnace is level 7,the direct reduction process of a hydrogen-based fluidized bed is level 6,the process of hydrogen-rich blast furnace ironmaking is level 7,and the hydrogen-based melting reduction ironmaking process is level 6. On the whole,the hydrogen metallurgical process is still in the stage of continuous exploration and development,and there are no mature and commercial manufacturers. Finally,the historical development process of the main hydrogen metallurgy process route is reviewed,and the future development trend and prospect of hydrogen metallurgy are discussed. Among the four processes,the direct reduction process of hydrogen-based shaft furnaces is expected to be commercialized at the earliest,and the replacement of hydrogen for carbon in the metallurgical process,helping to achieve nearly zero carbon emissions in steel production.

Due to the "homomorphic replacement" of aluminum-iron, Al-goethite is formed, and it is difficult to achieve aluminum-iron separation. H₂ was used as the reducing agent, the typical high-iron gibbsite was pretreated by levitation magnetization roasting. The iron was enriched in red mud by Bayer dissolution and separation. The effects of roasting conditions on its phase structure, microscopic morphology, specific surface area and dissolution properties were investigated, and its magnetic changes before and after roasting were analyzed. The results show that the roasted ore is loose and porous, the specific surface area is greatly increased. The aluminum mineral is transformed into γ-Al₂O₃, the dissolution activity is good, and the hematite is transformed into magnetite, while the Al-goethite is transformed into a porous aluminum replacing magnetite structure. The aluminum element does not migrate, the separation effect of aluminum and iron is improved, the optimal roasting conditions are 500 ℃, the time is 10 min, the volume fraction of H₂ is 20%, the total gas flow rate is 500 mL/min, the relative dissolution rate of alumina reaches 96.47%, and the aluminum content in the dissolved red mud is reduced. The iron content is increased, the TFe content reaches 60.56%, which is 11.28 percent points higher than that of the original red mud. The iron mineral still maintaines the magnetite structure, and the saturated magnetization is 54.1 A·m²/kg. Further improvement of iron grade through magnetic separation is beneficial for achieving reduction of red mud.

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

With the progress of energy-saving work, the difficulty of energy-saving of steel industry in China is increasing, and the potential is decreasing under traditional technological systems in steel manufacturing processes. In the new period of high-quality development on the constraint of the "dual control" of energy consumption and carbon emissions, the steel industry is entering a new stage with efficient energy conversion, intelligent energy-flow dispatching, and integrated matching optimization. Networked operation and intelligent dispatching of energy flow are important means to explore greater potential for energy-saving. Modeling for energy flow network is the foundation for intelligent dispatching and integrated optimization of energy system. Petri Net, as a formal model for describing net systems, is a modeling tool for describing the relationships between units and the resource changes in directed net systems. Both Places and Transitions have into two types: continuous and discrete, to represent continuous variables and discrete events respectively, and thus form a hybrid Petri Net for modeling hybrid system. Based on metallurgical process engineering, the essential features of the steel manufacturing process and its energy flow network system were analyzed, and the system structure and dynamic characteristics of the energy flow network for steel manufacturing process were analyzed as a "directed network" from "system" perspective. Based on the hybrid Petri Net modeling method, an energy flow network model for steel manufacturing process was developed by formally abstracting. This model can qualitatively and quantitatively describe the relationships between elements of the energy flow network system, thus visually and realistically describing the system structure and dynamic characteristics. Taking a typical steel plant as an example, the Petri Net model for the energy conversion process was established and simulated by Matlab software with a 1 h step based on production performance data from a sample day. The simulation results show that the model matches well with the actual system. This method can provide technical support for the energy evaluation, dynamic dispatching and optimization of the energy flow network system for steel manufacturing process.

With the increasing demand for domestic copper resources, there is a large gap between the production and consumption of refined copper, and the recycling of scrap copper has become a necessary way to solve the shortage of copper resources. Scrap copper can be divided into three categories according to copper grade, namely high, medium and low grade, in which the high-grade scrap copper can be recycled by direct utilization or one-stage process, while the medium and low grade scrap coppers are mainly recycled by two-stage process, flotation and hydrometallurgical process. The recycling process of different types of scrap copper was discussed in detail, and the principles, advantages and disadvantages of various processes were summarized by analyzing the implementation cases of pyrometallurgy, hydrometallurgy and flotation methods for scrap copper. Based on the current situation of copper scrap recycling in China, improving the classification standards and recycling system of copper scrap can effectively enhance the comprehensive utilization of scrap copper resources.

GH4738 alloy is a high-performance nickel-based superalloy. It plays a key role in aviation, aerospace and petrochemical industries due to its excellent high temperature strength and excellent creep and fatigue properties. The basic research progress of GH4738 alloy in the past half century is reviewed (from 1973 to present), including its composition, smelting process, homogenization treatment, hot deformation behavior, heat treatment and development trend. The innovative achievements of a series of engineering preparation technologies, such as the synergistic increase of Al and Ti content, the substitution of W for Mo to improve the comprehensive performance, the development of a triple smelting process and the control technology of inclusions and harmful elements, the establishment of a thermal deformation constitutive equation and recrystallization grain structure evolution model, and the application of finite element numerical simulation in the microstructure prediction of large-size complex forgings, are described, and the future development is prospected based on the current research situation. The aim is to meet the urgent needs of high performance, high reliability and long life of the new generation of aero-engine materials and to promote the further promotion of GH4738 alloy.

Compared with natural gas and pure hydrogen gas, coke oven gas(COG), a by-product gas of iron and steel works with stable output and low cost, is the most potential hydrogen-rich reduction gas that can be used in blast furnace injection. In order to obtain basic theroetical data of COG injection in the blast furnace, the suitable injection amount of COG and the operating conditions under different heat compensation modes were calculated. The carbon consumption of blast furnace under different operating conditions was compared and analyzed further. A mass-energy balance model of blast furnace with COG injection was established based on the raw materials and operation conditions of a 2 500 m³ blast furnace in a steel plant. The direct reduction degree of iron was iteratively calculated and applied to the calculation of material and heat balance according to the Rist operating line theory with hydrogen. The heat balance model of the whole furnace and high temperature zone was established. Subsequently, the energy utilization coefficient and heat utilization coefficient of the blast furnace with different injection amount and operating conditions were calculated, and the corresponding carbon consumption and emission reduction were discussed. The results show that when COG is injected alone, the bosh gas volume increases with the increase of COG injection volume, resulting in the theoretical combustion temperature decreases. Simultaneously, the heat consumption of direct reduction goes down and the temperature of top gas goes up which make the heat energy and energy utilization coefficient decrease. The injection of 1 m³ COG per ton of iron can reduce theory combustion temperature by about 0.9 ℃. Increasing oxygen enrichment rate and blast temperature is the most effective means of heat compensation for the blast furnace with COG injection. The injection of COG can reduce fuel ratio, comprehensive carbon consumption and carbon emission. Under the same COG injection amount, higher oxygen enrichment rate is needed to reach the theoretical combustion temperature before COG injection. An increase of oxygen enrichment rate by 0.91% enables COG injection volume to increase by 10 m³ for per ton of Fe. With the increase of blast temperature, the acceptable amount of COG injection increases, and it has little effect on heat and energy utilization coefficient of blast furnace. Under the calculation conditions, when the blast temperature is 1 250 ℃ and the COG injection amount is 100 m³, the coke ratio is reduced by 55.4 kg/t, and the replacement ratio between coke oven gas and coke is about 0.55 kg/m³. With the increase of COG injection, the comprehensive carbon consumption of blast furnace declines. In order to select a suitable COG injection volume while keeping the blast furnace running smoothly, it is suggested to consider the economic benefits of reducing cost and increasing production, the potential of saving energy, as well as the oxygen supply capacity of enterprises.

Constrained by energy structure and resource endowment, it is challenging to fundamentally alter the process structure of China′s iron and steel industry, dominated by the traditional blast furnace-converter long process. A theoretical model integrating gas-solid heat transfer and reaction kinetics was developed for the low-carbon blast furnace technology featuring gas injection as its core. Gas-solid heat transfer effects, ore reduction, coke dissolution loss, burden softening and melting, and slag-iron droplet influence on gas-solid phase interaction was considered in the model. The model was employed to simulate the smelting process of a 2 300 m³ blast furnace in China, yielding characteristic parameters consistent with production data, such as gas quantity in the belly and furnace top temperature. Furthermore, the model was used to study the impact of various injection volumes on gas flow distribution and temperature distribution within a 2 300 m³ blast furnace operating under CO-rich gas injection conditions. Results indicate that gas introduction fosters indirect reduction, leading to increased gas and charge temperatures in the upper furnace region with rising injection volumes, while causing a slight drop in pressure. The research work provides a theoretical basis for the parameter design of the subsequent low-carbon blast furnace technology.

To study the desulfurization behavior of CaO-Al₂O₃-MgO-SiO₂-CaF₂ slag in ladle refining process for high-manganese steel, the effect of CaO/Al₂O₃ mass ratio in CaO-Al₂O₃-5%MgO-5%SiO₂-10%CaF₂(mass fraction) refining slag on the desulfurization efficiency and the rate controlling step of the desulfurization of ZGMn13 high manganese steel at 1 873 K was investigated. The highest desulfurization efficiency of 97.9% achieved when the CaO/Al₂O₃ mass ratio in the slag was 1.8, while desulfurization effect was the worst when the CaO/Al₂O₃ mass ratio was 0.2. The mass transfer coefficient in the slag k_s was calculated as between 1.38×10^-7 m/s and 1.99×10^-6 m/s, and the mass transfer coefficient in the steel k_m was 7.85×10^-5 m/s. In addition, the overall mass transfer coefficient k_o of sulfur in high-manganese steel increases with the increase of CaO/Al₂O₃ mass ratio in the slag and gradually levels off. The change in k_o is not significant when the CaO/Al₂O₃ mass ratio in the slag is between 1.2 and 1.8(the change is 8.7×10^-6 m/s). This shows that the rate controlling step of desulfurization process was the transfer of sulfur in the slag when the CaO/Al₂O₃ mass ratio was lower than 1.2, while it changed to the mass transfer of sulfur in steel when the desulfurization reaction of the CaO/Al₂O₃ mass ratio was between 1.2 and 1.8. Compared to low alloy steels, the diffusion of sulfur in the steel was reduced due to the higher content of manganese in the steel.

With the urgent demand for energy conservation and emission reduction driven by "carbon peak" and "carbon neutrality", as well as the continuous increase in scrap steel production, high scrap ratio steelmaking technology has become an important direction for the development of converter steelmaking. A large steel enterprise gradually increased the converter scrap ratio to 27.01%, with a scrap consumption of 361 kg per ton of steel. In the face of insufficient iron resources, the steel production was significantly increased, and the higher scrap ratio also led to a rapid increase in steel material consumption. In order to study the reasons for the increase in steel consumption under high scrap ratio and find solutions, it is necessary to carry out targeted steelmaking process analysis and research. As the scrap ratio increases, the heat inside the converter furnace becomes uneven, and the scrap steel inside the furnace does not melt; The endpoint oxidation of the converter is enhanced, and the total iron mass fraction of the final slag increases from 14% to 19%; The low-temperature splashing rate increased by 7.7 percentage points in the early stage of smelting. Research has found that by increasing the target[Si] mass fraction of molten iron to 0.40%-0.50%, preheating the scrap steel in the molten iron tank to 800 ℃, and adding a warming agent to the converter, the source of heat for the converter can be increased. Adjusting the gun position control mode and adopting a low slag smelting optimize converter operation mode. Reducing the size of scrap steel entering the furnace by 14.3%, optimizing the loading system, and exploring multiple channels for refining and adding scrap steel promote scrap steel melting. Measures such as recycling furnace slag and continuous casting residue to reduce metal material loss have curbed the trend of steel material consumption increasing. The physical consumption of steel materials has decreased from 1 094.5 kg/t and stabilized at below 1 088 kg/t, laying a solid foundation for enterprises to maintain profitability in the severe market environment competition.

Ultra-high purity (UHP) AISI 316L austenitic stainless steel is a key material for semiconductor equipment components. Material produced through the vacuum induction melting (VIM) followed by vacuum arc remelting (VAR) process is referred to as Material A, while material produced through the argon oxygen decarburization (AOD) followed by VAR process is referred to as Material B. In order to investigate the quality gap between domestically produced and imported ultra-high purity 316L stainless steel, eight types of ultra-high purity 316L stainless steel A and B materials from different manufacturers were selected. The inclusion analysis was carried out using metallographic microscopy, scanning electron microscopy (SEM) with accompanying energy dispersive spectroscopy (EDS), and Thermo-Calc thermodynamic software. The results show that Material B from Domestic Manufacturer A has the lowest inclusion density and area fraction, indicating the highest cleanliness, followed by Material A from Domestic Manufacturer A, Material A imported from Japan, Material B imported from Japan, and Material A from Domestic Manufacturer B. The inclusion control level of Domestic Manufacturer A has reached international advanced standards, employing rare earth Ce-modified inclusions, primarily Ce₂S₃ and Ce₂O₂S. Inclusions in Material A from Japan and Material A from Domestic Manufacturer C consist of Al₂O₃. The high Mn content in Material A imported from the United States results in inclusions of MnO·Al₂O₃ and MnS. Both Material A from Domestic Manufacturer B and Material B imported from Japan undergo Mg modification treatment, leading to inclusions mainly composed of MgO·Al₂O₃ and Al₂O₃. Inclusions in Material B from Domestic Manufacturer B are large-sized Cr₂O₃ and Al₂O₃. The Thermo-Calc 2020b calculations for inclusion evolution during cooling are in good agreement with the experimental results.

To address the challenge of high carbon emissions in China's steel industry and promote green and low-carbon transformation, this study systematically reviews the carbon emission reduction pathways, technological advancements, and empirical achievements of long-process steelmaking under the framework of steel-chemical integration technology. It further reveals the potential and challenges in achieving near-zero carbon emissions. In terms of process optimization, steel-chemical integrated production utilizes the blast furnace gas (CO) in a directional manner, transforming the carbon resources traditionally emitted through combustion into chemical products such as formic acid and ethylene glycol, thus achieving a "use instead of discharge" carbon cycle mode. This can reduce carbon emissions by up to 79.68 kg/t in the steel industry and 259.16 kg/t in the chemical industry (calculated by molten steel). Simultaneously, the ironmaking process, through the collaborative application of hydrogen-based direct reduction iron (DRI), iron coke technology, and high-pellet ore smelting, can reduce the carbon emissions of molten iron from 1.7 t/t to 0.8 t/t. The BOF process, through low-carbon raw materials, energy substitution, and low-carbon smelting technologies, can reduce its carbon emissions from 159.6 kg/t to -165.95 kg/t (calculated by molten steel). Furthermore, dynamic models based on carbon flow analysis indicate that through the multi-path collaboration of steel-chemical integrated production, CCUS (carbon capture, utilization, and storage), and scrap ratio optimization, the carbon emissions of the BF-BOF long process can be reduced from the current 1 625.35 kg/t to 287.73 kg/t (calculated by molten steel). While the electric arc furnace (EAF) short process has an ultra-low-carbon potential of 64 kg/t, the long process will remain the primary decarbonization method until 2035.

As one of the implementation methods of heavy reduction technology, single roll heavy reduction is different from only using heavy reduction technology as a supplement or optimization of soft reduction technology. Instead, it is applied as an independent reduction technology different from soft reduction. It is necessary to verify the effectiveness of its process, and even systematically explain it based on practice. Based on the practical results of single roll heavy reduction of 82B steel grade with 180 mm×180 mm billets, and on the basis of reliable evaluation of center shrinkage and center segregation methods, the improvement effect of center shrinkage and center segregation after single roll heavy reduction at different pressing positions is analyzed to verify the effectiveness of single roll heavy reduction technology in independently improving the quality of casting billets. Combined with practice, the mechanism, method, and guiding principles of single roll heavy reduction process control are proposed. Finally, the advantages of single roll heavy reduction technology in simplifying equipment schemes are presented. The results of practice and research analysis under single roll heavy reduction show that the optimal reduction position for improving center shrinkage under continuous casting heavy reduction is before the filling and shrinking channels are closed and the shrinkage holes are formed, rather than welding after the shrinkage holes are formed. The optimal location for improving center segregation under heavy reduction is also before the filling and shrinking channels are closed and shrinkage holes are formed. The formation of center porosity, shrinkage, and center segregation are interrelated in mechanism. By applying single roll heavy reduction in suitable areas where the filling and shrinking channels are not closed and shrinkage holes are not formed, both center shrinkage and center segregation can be effectively controlled simultaneously, achieving the effect of improving the quality of the casting billet. As the amount of single roller reduction increases, there is a tendency for loose and shrinkage defects to aggregate towards the center, while the accompanying center segregation does not show an increasing trend. The critical position for the end of the filling and shrinking channel of 82B steel grade is around 0.73 in the center solid phase ratio. The single roll heavy reduction process will simplify the equipment for pressing billets, greatly reducing its cost.

The high temperature thermoplasticity of casting billet is an important basis for characterizing the performance and quality of casting billet. The traditional testing method is to slowly stretch cylindrical specimens at low strain rates at different temperatures until the specimens fracture. By analyzing the relationship between tensile temperature and cross-sectional shrinkage rate, the high temperature thermoplasticity of casting billet can be evaluated. However, the actual cooling process of the casting billet is relatively complex and has many influencing factors. If only a single variable is analyzed for the high temperature thermoplasticity of the casting billet, the information obtained is limited. Therefore, based on conventional high temperature tensile tests, the cooling and reheating thermoplasticity tests and different cooling rate thermoplasticity tests were innovatively designed. Taking V-containing microalloyed steel continuous casting billets as the research object, the influence of high temperature tensile temperature, cooling transition temperature, and different cooling rates on the high temperature thermoplasticity of casting billet was analyzed. By drawing a comprehensive diagram of high temperature thermoplasticity of continuous casting billets, the influence of cooling and reheating process at edge positions on thermoplasticity was supplemented, achieving a more systematic and comprehensive characterization of thermoplasticity, effectively solved the problems of cracking at the edges and corners of the casting billet, provided effective basic data support for solving the edge cracking problem of V-containing microalloyed steel. At the same time, by drawing a continuous cooling thermoplastic diagram, the graphical and numerical representation of continuous casting cooling rate process control have been achieved, providing a method and basis for formulating the optimal continuous casting process route.

With the increasing demand for pellet, more and more low-quality iron ore resources have be used for pellet production, but the iron ore concentrate after its fine grinding and deep separation is characterized by fine embedded particle size and large specific surface area. An experimental study on the preparation of oxidized pellets from ultrafine iron concentrate was carried out, and the high temperature consolidation behavior of pellets was analyzed. Results show that under the optimal conditions of 5 times high-pressure roller grinding, 1% bentonite A binder, under the optimized preheated roasting system, the drop strength, compressive strength and bursting temperature of the green pellets are 5.2 times, 12.71 N and 450 ℃, respectively. And the compressive strength of preheated pellet and roasted pellet are 499 N and 2 509 N, respectively. The drying process of ultrafine iron pellets should be maintained at 300 ℃, at this time the green pellet drying rate is fast and the time required for complete drying of pellet is 3 min. The main minerals of pellet are hematite and silicate, and the main bonding method of pellet is Fe₂O₃ recrystallization consolidation. Fully grown Fe₂O₃ grains and close interlinkages among the hematite grains result in the pellet structure being tight and homogeneous.

In order to improve the service life of ductile iron cooling staves, the damage mechanism was firstly discussed through theoretical analysis, focusing on aspects such as phase transformation damage, chemical erosion, and mechanical properties. Secondly, heat transfer analysis of ductile iron cooling stave was conducted using numerical simulation method. Finally, the management measures for cooling stave were given based on theoretical analysis with typical production practice, and the longevity concepts and suggestions for the operation of ductile iron cooling stave were proposed. The results show that the primary reason for the damage to ductile iron cooling stave is the long-term operation of the stave body above 400 ℃. Maintaining the stave body temperature below 400 ℃ in the long term and enhancing the slag-adhering ability of the "wet zone" of the cooling stave are crucial factors for achieving long service life of ductile iron cooling stave. It can be achieved by the excellent design combined with good operation, the reasonable control of the distribution of edge gas flow, reducing the thickness of water pipe gaps, and improving the stave′s heat load bearing capacity. The proposed longevity concepts and suggestions for ductile iron cooling stave can provide valuable guidance for blast furnace design and operation.

Under the background of global warming and environmental governance, aiming at issue of large CO emission and urgent pressure of emission reduction in sintering process, the current situation of CO emission and control in China's industry is expounded. The mechanisms of CO generation during the iron ore sintering process were discussed, the main pathways for CO production were revealed, including the oxidation of carbon and incomplete combustion of fuels, and the impact of these pathways on CO emissions was analyzed. On this basis, two key CO emission reduction technologies, hydrogen-rich gas injection and oxygen-rich ignition, were proposed. Employing numerical simulation and sintering cup test methods, the mechanisms and effectiveness of these technologies in reducing CO emissions during the sintering process were examined, and these two technologies were implemented in the sintering machine at Zhongtian Iron and Steel. The application results show that hydrogen-rich gas injection technology can achieve a 14.8% reduction in CO emissions in the sintering process, oxygen-enriched ignition technology can achieve a 5.8% reduction in CO emissions in the sintering process. The research findings provide new technological ways for CO emission reduction in the sintering industry.

SPHE steel is produced by the BOF-LF-RH-CSP process in a domestic steel mill. In order to control the cleanliness of the steel, the changing law of the type, quantity, and size of inclusions in the refining process of SPHE steel was investigated. The results demonstrates that throughout the entire refining process, the inclusions achieve the following modification process, Al₂O₃→MgO·Al₂O₃ spinel with high Al₂O₃ content →CaS·C₁₂A₇·MgO·Al₂O₃ composite inclusions. The number density of inclusions decreases from 97/mm² when entering the LF station to 12/mm² when leaving the RH station. Furthermore, the average size is gradually reduced from 5.2 μm to 1.5 μm, and the cleanliness of the steel is significantly improved. Thermodynamic calculations at 1 873 K show that the [Mg] mass fraction corresponding to the stabilization interval of the generated MgO·Al₂O₃ is 0.000 032 3%-0.001 800 0% for the [Al] mass fraction range of 0.021 6%-0.053 3% in the refining process. Upon entering the RH station, the [Al] mass fraction is 0.053 3%. The generation of liquid 12CaO·7Al₂O₃ (C₁₂A₇) is favored when the [Ca] mass fraction is in the range of 0.000 24%-0.000 87%. There is a strong tendency to generate MgO·Al₂O₃ during the refining process, which is the nucleation core of CaS·C₁₂A₇·MgO·Al₂O₃ composite inclusions. The evolution law of inclusions in the refining process under the BOF-LF-RH-CSP process is revealed by establishing a kinetic model of inclusion evolution. The research results provide data support for improving the castability of SPHE steel produced by the CSP process.