With the proposal and implementation of the strategy of “carbon peak and carbon neutralization” in China, the metallurgical industry is facing huge pressure on carbon emission reduction. Compared with traditional blast furnace-converter steelmaking, electric arc furnace (EAF) steelmaking has lower carbon emissions, which is one of the important ways of near-zero carbon emission steelmaking. Scrap, the main raw material of EAF steelmaking, contains residual harmful elements, such as copper, tin, arsenic and antimony, which have an important impact on the smooth progress of the production process and the final properties of iron and steel products. The research progress on the source, control standard, hazard mechanism, removal and mitigation methods of typical residual elements was reviewed. The solute solidification segregation of residual elements in liquid steel during solidification is easy to produce internal cracks, and the decrease of grain boundary strength due to segregation at grain boundaries will lead to poor thermo-plasticity or the second kind of temper brittleness of steel. In addition, the enrichment between steel matrix and oxide layer will also cause surface hot brittleness. The ingredient dilution method, as the main means to control the harm of residual elements in industrial production, has a high cost and cannot fundamentally solve the problem of residual elements. The addition of inhibitory elements such as boron and rare earth can form residual element compounds to float and remove or form competitive segregation to reduce the harm of residual elements.

The construction of kinetic equations for the phase transition of C-Mn steels is of great significance in guiding its microstructure regulation and mechanical property enhancement. Continuous cooling transformation behavior of C-Mn steel was investigated by Gleeble-3500 thermal simulator, optical microscope (OM), field emission scanning electron microscope (SEM). The conventional JMAK equation was optimized based on the phase transformation products. The results show that the C-Mn steel was cooled at a rate of 0.5-50 ℃/s after complete austenitising at 1 000 ℃. With the increasing cooling rate, the supercooled austenite undergoes the phase transformation of ferrite, pearlite, bainite and martensite successively. The organisation is fully martensitic when the cooling rate is greater than 20 ℃/s and the corresponding transformation temperature intervals are 728-516, 517-400 and 330-190 ℃. When the cooling rate increases, the critical time span t₀ of the phase transition product transformation decreases exponentially, with an exponential fit as t₀=120.6 v^-0.83. Based on the influence of different phase transition products on the n value,the functional equation of the n value on the cooling rate was established under different cooling rates. The kinetic equations for the JMAK phase transition were constructed. Eventually, model prediction accuracy has been improved. The JMAK equation has a driving role in describing the multiphase transformation process under non-isothermal rapid cooling conditions.

The turbine blades made of superalloy are among the most critical components in the hot section of aero-engines and gas turbines. Operating within a complex environment of high temperatures, stress, and gas corrosion over extended periods, they are susceptible to various forms of damage. Turbine blades made of superalloy is costly, so it is not economical to replace blades with only minor damage. Therefore, research on the turbine blades damage and repair technology is crucial for reducing the overall repair and manufacturing cost associated with superalloy turbine blades. The necessity for researching turbine blade damage and repair technology was firstly clarified. Then, the main types of service damage experienced by superalloy turbine blades were classified, including internal metallurgical microstructure damage and apparent damage. Various repair technologies were summarized, including welding repair technology, damage repair technology based on additive manufacturing, and recovery heat treatment technologies while analyzing their respective advantages, disadvantages and applicability. Finally, it provides an outlook on the future development direction of superalloy turbine blade repair technologies.

With the development of the aerospace technology, the reverts of Ni-based superalloy is accumulated increasingly. To efficiently mitigate the waste of precious metals and promote the circular economy, it is crucial to control the composition and properties of revert alloys to be equivalent to those of virgin alloys through purification and utilization technology. However, with the wide variety and complex composition along with the impurities and flaws presented in the reverts, the difficulty is rising in purifying and utilizing the Ni-based superalloys. The effects of revert proportion and recycle times on the composition, microstructure and mechanical properties are summarized. The worldwide pretreatment technology and melting purification methods for revert are discussed , focusing on the cleanliness analysis method. Furthermore, some valuable suggestions are provided on enhancing the recycling of superalloy revert.

High-entropy alloys (HEAs) demonstrate exceptional resistance to hydrogen embrittlement due to complex chemical composition, disordered atomic structure, severe lattice distortion effect and so on. These factors result in distinct hydrogen solubility, hydrogen diffusion coefficients, and hydrogen trapping ability compared to other metallic materials. In order to accelerate the development of HEAs in the field of hydrogen embrittlement resistance, it reviews the existing studies, summarizes the influence and mechanisms of microstructure, alloying elements, sources of hydrogen and preparation parameters on the resistance to hydrogen embrittlement of HEAs, and finds that there is a specific range of influence for the aforementioned factors on the resistance to hydrogen embrittlement of HEAs, and this specific range needs further experimental research and theoretical analysis to determine for different HEAs. Finally, some design strategies are introduced to enhance the resistance to hydrogen embrittlement of HEAs, such as grain boundary engineering, gradient nano-twins, introducing nano-carbide/nitride, computer aided design, and the focus of future research work of resistance to hydrogen embrittlement of HEAs is prospected.

Electrolytic ironmaking from aqueous solution, an emerging hydrometallurgical technology, aims to produce pure iron by electrolytic reduction of iron compounds, offering significant environmental and energy advantages. In recent years, with the continuous advancements in materials science, electrochemical technology, and energy systems, substantial research progress has been made in electrolytic ironmaking processes and techniques. However, certain technical challenges remain. For instance, the gas element content in the electrolytic products is high, necessitating further treatment to achieve higher purity iron. The stability of the electrolyte is poor, and ferrous ions are prone to oxidation and degradation.The state-of-the-art principles, processes, equipment, and control technologies of electrolytic ironmaking both domestically and internationally were reviewed. Corresponding solutions to the technical challenges have been suggested. For example, increasing the electrolysis temperature could reduce the gas element content in the products, thereby shortening the process, and adding stabilizers (such as ascorbic acid and sodium citrate) could inhibit the oxidation of ferrous ions. Finally, recommendations and outlooks for the future advancement of electrolytic iron production are given,including improvements in electrolysis equipment and the shortening of process flows to save energy consumption and intelligent systems implemented for real-time monitoring and other applications.

The development of high-pressure hydrogen storage materials has become a key goal in promoting China's hydrogen energy construction. With good hydrogen embrittlement resistance, formability, and low-temperature toughness, austenitic stainless steel (ASS) is considered to be an excellent candidate material for high-pressure hydrogen storage containers. However, the excessive use of precious metals in traditional ASS makes it unsuitable for large-scale application, and the low strength of ASS can also cause safety hazards. Therefore, thermodynamic phase diagram calculation methods are used to design an ASS (named NEASS), and slow tensile testing and various microscopic characterization methods are used to evaluate its hydrogen embrittlement resistance. The results show that the strength and hydrogen embrittlement resistance of NEASS are about 15% and 70% higher than those of 316L stainless steel, respectively. During the deformation process after hydrogen charging, NEASS exhibits a special multidirectional slip mechanism, which alleviates local stress concentration and effectively inhibits the initiation and failure of hydrogen-induced cracks.

The iron and steel industry is a crucial foundational sector in China's national economy and a major carbon emitter, producing 1.3 billion tons of CO₂ annually, which accounts for 15% of the nation's total carbon emissions. Annual steel slag generation also reaches 150 million tons. Utilizing the bulk steel slag generated by the industry itself to sequester significant amounts of CO₂ enables“treating waste with waste”, provides an outlet for captured CO₂, and makes deep decarbonization of the steel industry feasible. The major advantages and existing problems of steel slag carbonation technologies are reviewed, which could be categorized them into two main types (direct and indirect carbonation). These can be implemented through three specific approaches: hot slag direct carbonation, cold slag direct carbonation, and cold slag indirect carbonation. It could be pointed out that both hot steel slag direct carbonation technology and cold steel slag indirect carbonation technology are suitable for China's context in achieving its dual-carbon goals. Hot slag direct carbonation seamlessly integrates with existing steel slag treatment processes in steel plants. Cold slag direct carbonation has relatively lower carbonation efficiency and capacity due to its lower reaction temperature, whereas cold slag indirect carbonation achieves higher-value utilization of the slag.

Under the dual context of China′s dual carbon strategy and the EU′s carbon border adjustment mechanism, significant transformation in the structure of steelmaking raw materials is being observed. The future development trend is characterized by both a high scrap ratio in basic oxygen furnaces and the utilization of electric arc furnaces operating with 100% scrap. However, the extensive introduction of scrap steel presents challenges to the cleanliness of molten steel and the subsequent quality of steel products, particularly concerning the impact of nitrogen content and titanium nitride inclusions on steel performance. Based on previous theoretical and industrial experimental research on the“nitrogen content-titanium nitride inclusions-material performance” relationship, progress in studies on the formation and control of titanium nitride in steel is summarized. The precipitation mechanism of titanium nitride in steel is analyzed from a thermodynamic perspective, and microsegregation and coupled precipitation models are reviewed. Key factors influencing titanium nitride precipitation are quantitatively analyzed. Through an analysis of the nitrogen content evolution during the steelmaking process, nitrogen content control methods in molten steel are systematically studied from the perspectives of raw material control, vacuum degassing, and slag-based nitrogen removal. The results of this review provide theoretical guidance for the production of high-quality titanium-containing steel in the context of changing raw material structures in steelmaking.

Super-high bed sintering is an important route to reduce carbon emissions in the steel industry. However, as the sintering bed depth increases in practice, the severe inhomogeneity of sinter products adversely affects the blast furnace production. Joint analysis of mixture and sinter was carried out on more than 10 industrial sintering machines in China with bed depth of not less than 900 mm. It is revealed that the inhomogeneous quality of sinter products mainly manifested in the longitudinal direction, transverse direction, and between the strands. The root reason is that the uneven liquid phase composition and heat caused by unreasonable distribution of mixture particle size, chemical composition, and air cannot satisfy the requirements of liquid phase homogeneous mineralization. To address the above problems, an ideal bed structure matching the liquid phase and heat was developed. Besides, the optimized ore blending technology for liquid phase composition regulation, the enhanced mixing and granulation technology, synergistic feeding technology, and air reorganization sintering technology were developed to achieve this bed structure. By optimizing the chemical composition of liquid phase, regulating the distribution of liquid phase within the sintering bed, and matching the heat with the liquid phase quantity, the efficiency of heat and suction was improved, and homogeneous mineralization was achieved. After the implementation of those technologies, the solid fuel consumption was reduced by 1.2-7.9 kg/t, the tumble index increased by 3%-6%, and the difference of tumble index within the sintering bed was reduced to 5.08%. Furthermore, the metallurgical performance of the sinter improved, with the reduction disintegration index RDI_{+3.15 mm} increasing by 10% and the difference of RDI_{-0.5 mm} decreasing to 1.99%. The productivity of the blast furnace improved, and the solid fuel consumption was reduced by 6.58 kg/t at the highest.

In response to the phenomenon of “desulfurization and resulfurization” of steel during the process of adding scrap steel in a diversified smelting mode of a certain enterprise in China, the composition of refining slag was optimized reasonably. Firstly, the thermodynamic software FactSage 8.1 was used to simulate the iso-oxygen lines of CaO-SiO₂-Al₂O₃-5%MgO slag system and Q235 steel equilibrium was simulated and calculated under the temperature condition of 1 600 ℃. Meanwhile, the sulfur capacity and sulfur distribution ratio of the slag system were calculated by using the optical basicity of the refining slag to measure the desulfurization ability of the refining slag. Secondly, high-temperature equilibrium tests on steel slag were carried out using five different designed refining slags in the laboratory. After the experiment, the composition of the refined slag was determined through XRF analysis, and the elements within the steel samples were analyzed using ICP-AES, an oxygen-nitrogen analyzer, and a carbon-sulfur analyzer. Field emission scanning electron microscopy was employed to study the structure and makeup of inclusions within the steel samples. A statistical evaluation was conducted to assess the number and dimensions of these inclusions. Finally, industrial experiments were conducted to verify the results. The results show that by optimizing the composition of the slag system, the mass fractions of CaO, SiO₂, Al₂O₃, and MgO are controlled within the range of 47.7%-55.2%, 0-20.5%, 26.85%-55%, and 4%-7%, respectively. The mass fraction of dissolved oxygen in the steel can be controlled within 0.001%. A slag system composed of 54.27%CaO, 7.43%SiO₂, 33.3%Al₂O₃, and 5%MgO was selected, achieving a desulfurization rate of 54.73% and reducing the total oxygen in steel to 0.002 1%. The experimental results validated the accuracy of the thermodynamic calculations.

Grain oriented electrical steel (GOES) is one of the most fundamental and important materials in the construction of modern power energy systems, playing an indispensable role in high-efficiency power transmission and transformation. Due to its complex manufacturing process, high precision requirements for equipment functionality, and stringent process control challenges, producing high-performance GOES necessitates significant breakthroughs both in manufacturing equipment and process technologies. The technological advancements and development of GOES throughout its entire production process were explored, including composition design, microstructure control, and processing techniques. The roles of alloying elements in GOES and the key manufacturing technologies to achieve the target composition were specifically analyzed, the microstructural evolution during the rolling and heat treatment processes was summarized, the impact of critical process parameters in rolling and heat treatment on the microstructure of GOES was investigated, and the characteristics of key post-processing coatings and magnetic domain refinement technologies were outlined. Finally, in light of the severe challenges faced by GOES development, the future research directions and development trends in this field were proposed.

In order to meet the requirement of real-time acquisition of 3D flow field data in ladle bottom-blowing refining, a fast prediction model of 3D flow field based oncomputational fluid dynamics (CFD) and proper orthogonal decomposition (POD) was established. The three-dimensional flow field data of single-nozzle bottom blowing of ladle were simulated and calculated by establishing the numerical model and the water model, and the data set was established. The mode and mode coefficient of the data set were extracted by the POD method. Through the back propagation neural network (BPNN), the mapping relationship between operating parameters and modal coefficients was constructed, and the velocity field and three-phase volume fraction in the bottom-blowing ladle can be predicted quickly. The results show that the proposed model can reconstruct the main characteristics of the flow field in the ladle through a few modes. The POD-BPNN prediction model has a high accuracy of calculation results, and the average relative error of calculation results is less than 4%. The calculation speed of the model is fast, and the average calculation time to obtain the flow field in the ladle is reduced from about 246 h required by CFD simulation to about 54.6 h by the POD method.

In the field of modern bridge construction, steel structures are widely employed in key load-bearing and connection components, including main beams, main cables, stiffening girders of suspension bridges, piers, bearings, and composite bridge deck structures. This is attributed to their excellent mechanical properties and constructability. They play an indispensable role in ensuring the stability and safety of bridges. However, the corrosion of steel structures poses a significant threat to both the safe operation and the service life of bridges. Bridges are constantly exposed to complex and dynamic natural corrosion environments, including wind, sunlight, rain erosion, and various chemical substances, all of which can contribute to severe corrosion of steel structures. A comprehensive review of the corrosion status of bridge steel structures is reviewed and the corrosion behavior of these structures in various natural environments is meticulously examined, including marine, inland, and complex environments characterized by alternating dry and wet conditions. The analysis focuses on the corrosion characteristics and severity affecting different components, such as piers, bridge bodies, cables, and bearing systems. In investigating the corrosion mechanism, the differences between chemical and electrochemical corrosion are elucidated, further classifying and analyzing uniform and localized corrosion within the realm of electrochemical corrosion. Specific forms of localized corrosion, including pitting, crevice, and stress corrosion, are examined in detail with respect to their formation mechanisms, influencing factors, and the severity of damage that they inflict on bridge steel structures. Based on the analysis of corrosion conditions, corrosion protection strategies for bridge steel structures are systematically summarized and organized, including material selection, coating systems, cathodic protection, and other advanced technical methods. By applying and optimizing these measures, a solid scientific basis and reliable technical support for corrosion prevention are provided, thereby reducing safety risks associated with steel structure corrosion, promoting technological innovation in bridge engineering, and ensuring the long-term durability and safe operation of bridges.

The color and texture of the flame at the converter mouth are closely related to the carbon content and temperature of the converter. The prediction of the carbon content and temperature of the converter through the flame characteristics of the converter mouth collected by the spectrometer provides a new idea for the end point control of converter steelmaking. Based on the flame spectrum data set of the converter mouth and the PSO-ELM neural network, a prediction model of the carbon content and temperature of the converter is established. In view of the fact that the original spectrum contains more noise, stray light, etc., wavelet algorithm is used to reduce the noise of the spectral data set. Due to the large amount of flame spectrum data at the converter mouth and the large amount of redundant information, the attribute reduction algorithm of the Skowron difference matrix is used to find the smallest data set with the smallest decision set coverage from the given 2 048-dimensional wavelength data, and 8 special diagnosis indicators are obtained. By calculating the MIC coefficients of the 8 indicators, it is proved that the selected indicators are independent and non-collinear, avoiding the risk of unstable modeling and overfitting due to the high correlation among the indicators. A prediction model is established based on the PSO-ELM neural network, and the particle swarm optimization algorithm is used to optimize the defects of the input weights and hidden layer thresholds randomly generated by the ELM during initialization. By applying the PSO-ELM model to the prediction of carbon temperature of converter, the example validation shows that the model has high accuracy and good prediction effect on carbon temperature prediction, which is suitable for the prediction of carbon temperature of converter and has a better engineering application prospect.

To establish the relationship between composition, heat treatment process, and creep performance of austenitic heat-resistant steels with 18%-25%Cr under various temperature and stress service conditions, the chemical composition, heat treatment process, creep test rupture time, and creep test temperature of nine types of austenitic heat-resistant steels were used as input parameters, with creep strength as the output parameter. Using SHAP values and maximum marginal correlation to select features, a prediction model for the creep performance of 18%-25%Cr austenitic heat-resistant steel based on a BP neural network was established. The results indicate that when compared to traditional methods, this model can construct the relationship between the composition, heat treatment process, and creep rupture properties of 18%-25%Cr austenitic heat-resistant steels under complex service conditions, achieving accurate prediction of creep rupture property for 18%-25% Cr steels. For specific steels, the combination of the BP neural network model and thermodynamic calculation methods can further screen and optimize the composition combination of the steel from the perspective of structure-property.

To further understand calcium treatment technology, industrial experiments were carried out in the refining process of Q355 Ti-bearing Al-killed steel grades, and the inclusions in steel and the cleanliness of the steel were investigated considering different feeding lengths of Ca wires. The results show that the solid inclusions during the refining process transformed into the liquid CaO-Al₂O₃ inclusions, and the feeding length of calcium wires did not affect the evolution trend of the inclusions. After calcium treatment, the total oxygen content of the steel increased, while the average size of the inclusions decreased. Furthermore, both the occurrence of the large-sized CaO-Al₂O₃ inclusions and the degradation of refractory wereaggravated by calcium treatment. After ensuring steel castability, a smaller feeding length of Ca wire is beneficial for the cleanliness of the steel. If there are no castability problems, calcium treatment can even be eliminated.

Q890 high-strength structural steel was used to explore the influence of intercritical quenching temperature and tempering temperature on the microstructure and precipitates by using ThermoCalc software, transmission electron microscope and tensile testing machine. The results indicate that with decreasing the intercritical quenching temperature (840, 800, 760 ℃), the proportion of ferrite increases, and the types of the precipitated particles increase, and the average diameter and the volume fraction of the precipitated particles decreases. After 840 and 800 ℃ quenching, the strength of the tested steel is similar. After reducing the quenching temperature to 760 ℃, the yield strength of the tested steel decreases by about 200 MPa, and the fracture elongation increases to 18.5%. With the increase in tempering temperature (200, 400, 600 ℃), the dislocation density of the texted steel decreases, and the matrix softens; the type of the precipitated particles increases, and the average diameter and the volume fraction of the precipitated particles increase, and thus the precipitation strengthening is significantly increased. As the tempering temperature increases, the yield strength of the tested steel gradually decreases (1 210, 1 120, 817 MPa), and the fracture elongation gradually increases (14.0%, 14.2%, 21.8%).

Controlling the size of slag eye by bottom blowing in steel ladle can improve the quality of steel liquid. Based on the argon bottom blowing process in steel ladle, a three-dimensional unsteady multiphase flow water model is established by coupling the Discrete Phase Model (DPM) and the Multiphase Flow (VOF) model. The slag eye size and slag eye interface velocity obtained from numerical simulation are validated and analyzed using a 1:5 water model. The research investigated the impact of different parameters (bottom blowing flow rate, oil layer thickness, and bottom blowing position) on the distribution of slag eye size and slag eye interface velocity. Finally, the relationship between dimensionless slag eye area and dimensionless flow rate was obtained through data fitting methods. The results indicate that the slag eye area gradually increases with the increase of blowing flow rate and the decrease of oil layer thickness, with a more significant effect for higher bottom blowing flow rates. A greater eccentricity of the nozzle leads to a more noticeable change in slag eye area with respect to blowing flow rate. For eccentric bottom blowing, there is a critical flow rate value, beyond which the slag eye area decreases. For instance, with an oil layer thickness of 25 mm and a blowing flow rate of 2.26 L/min, the slag eye area decreased by 180 cm² compared to that when the blowing flow rate was 1.87 L/min.

The mechanical properties and fatigue performance of injection-production pipelines are vital for ensuring long-term safety and durability of underground gas storage (UGS).Mechanical performance tests and microstructural analysis on L360 pipeline steel base metal (L360-BM) and welds(L360-WM) were conducted. To address the challenge of testing high-cycle fatigue in injection-production pipelines, a high-cycle fatigue simulation model was developed for both base metal and welds based on experimentally measured material properties, and its accuracy was verified through high-load fatigue tests.The fatigue life evolution under varying loading conditions is further explored, comparing the fatigue performance of the base metal to that of the weld specimens. Results indicate that the plasticity of L360-WM is markedly lower than that of L360-BM, with elongation at break is 26.1% for L360-BM and 21.6% for L360-WM, characterized by ductile fracture and quasi-cleavage fracture, respectively. Both L360-BM and L360-WM specimens exhibit a decrease in fatigue life as the average tensile load and load spectrum amplitude increase. For a tensile load of 6.5 kN and an amplitude greater than 0.075, the fatigue life of L360-WM specimens is 44.7% of that of L360-BM specimens. These findings offer valuable data and theoretical insights to support material selection and pipeline failure prevention in UGS.

The granulation of iron ore is indispensable in sintering process, which ensures the quality of sintering production. Under the background of the iron ore resources gradually depleting and the imported iron ore prices fluctuating, to improve and prefect the granulation process is crucial for enhancing the permeability of the material layer, increasing sintering production efficiency, and reducing energy consumption and production costs. The research progress of sintering granulation strengthening technology and process of iron ore is reviewed, including two aspects: conventional granulation strengthening technology and innovative granulation process. The advantage, disadvantage, and application scope of various technologies and processes are analyzed, aiming to provide reliable theoretical basis and practical guidance for iron and steel enterprises to scientifically select the granulation process according to their own raw material conditions and industrial needs, contributing to improved resource utilization and economic efficiency in sintering production.

Carbon content affects the distribution of carbides and element segregation during the solidification process of high-temperature alloys, thereby determining the microstructure and mechanical properties of superalloys. The effects of different carbon contents on the carbide distribution and quantity in GH3536 alloy ingots were investigated, and the elemental segregation behavior of the ingots was further analyzed. The results indicate that carbides in GH3536 are mainly M₆C and M₂₃C₆ types. Thermodynamic equilibrium calculation shows that the melting temperature range of carbides increases with the increasing ofcarbon content. M₂₃C₆ and M₆C can transform into each other. However, the remelting temperatures of carbides are not affected by the carbon content in DSC analysis. The addition of carbon content promoted the formation of two types of carbides, the carbide area increased significantly and morphology changed from block to net-like with the increasing carbon content which affected the ingot thermo-plasticity. The addition of carbon content also reduced the secondary dendrite spacing and inhibited the segregation of Cr, Mo and Ni. The segregation of elements reduced due to the precipitation of carbides occupies which consumed a large number of carbide-forming elements.

The microscopic mechanism of non-equilibrium segregation has not been fully elucidated. The solute-vacancy binding energy is an important parameter which is closely related to physical phenomena such as grain boundary segregation and diffusion. However, the experimental data are difficult to obtain. A database of solute-vacancy binding energy in fcc Fe based on an Anti-ferromagnetic double-layer (AFMD) structure was established based on first-principles density-functional theory. The correlation analysis of this binding energy shows a strong positive correlation between the first nearest-neighbor (1NN) solute-vacancy binding energy and solute impurity volume for transition metal solutes, and a strong positive correlation between the 1NN solute-vacancy binding energy and electronegativity for main-group elements. The calculated results successfully explain the reason of non-equilibrium grain boundary segregation of B, P and S. Results also predict that Si and As are also likely to form solute-vacancy complexes. The results not only reveal the microscopic mechanism of non-equilibrium grain boundary segregation, but also provide guidance in grain boundary engineering for utilizing alloyed elements.

In order to investigate the effect of austenitizing process on the grain growth behaviors of Nb-Ti microalloyed steel, thermal simulation experiments were conducted to study the austenite grain growth behavior of the experimental steel within the range of austenitizing temperature (1 140-1 220 ℃) and holding time (180-540 s). The mathematical models for austenite grain growth and its distribution were established. The results indicate that when the holding time is kept constant, the austenite grains tend to grow larger and become more uniformly distributed. When the austenitizing temperature is held constant, prolonging the holding time slows down the growth rate of austenite grains, and the size distribution of the austenite grains will also tend to become more uniform. The mathematical models for the average austenite grain size and its distribution closely match the measured values. Contour plots are generated for the average austenite grain size and grain size distribution parameter under different austenitizing process conditions, which provide a theoretical foundation for determining reasonable austenitizing processes for experimental steels.

Pulverized coal injection technology is the main technology to reduce iron-making production costs and improve blast furnace (BF) smelting efficiency. Biomass used for BF injection is one of the key technologies to achieve low-carbon iron-making due to renewable low-carbon energy source property. Three types of biomass hydrochar produced industrially were used to investigate the feasibility of applying the hydrothermal carbonization products (hydrochar) of low-quality biomass to BF injection. The results showed that hydrochar has high volatile content and low calorific value, while orange peel and olive pomace hydrochar have low ash and alkali metal content, which can be used as substitutes for bituminous coal for BF injection. The experiments of hydrochar mixed with anthracite show that hydrochar has strong explosiveness. Mixing anthracite with hydrochar can effectively suppress explosiveness. When the proportion of hydrochar added is less than 20%, the mixed sample has no explosiveness. Hydrochar has a lower ignition point and excellent combustion performance. As the mixing ratio of hydrochar increases, the ignition point of the mixed sample decreases, and the combustion curve moves towards the low-temperature zone, gradually improving the combustion performance. Based on the above research, hydrochar produced from orange peel and olive pomace can be used as BF injection fuel, and the proportion of hydrochar added to mixed anthracite should be controlled below 20%.

By conducting controlled rolling and cooling tests on dual phase steels of C-Si-Mn-Nb-Ti chemical system, ferrite bainite (FB) dual phase steels with polygonal ferrite structure and acicular ferrite structure were obtained, respectively. FB dual phase steel with acicular ferrite structure showed higher hole-expansion ratio, higher yield strength, tensile strength, and better elongation in the expansion and SEM in-situ tensile tests. During the plastic deformation process, the micro voids formed in acicular ferrite structure are finer and more dispersed. Due to its small and staggered distribution of acicular ferrite, it effectively reduces stress concentration, resulting in the generation of new and small voids during stress transmission, effectively preventing the propagation of macroscopic cracks. Therefore, FB dual phase steel with acicular ferrite structure has lower defect sensitivity and better formability than that with polygonal ferrite structure.

In order to investigate the effect of Al content on oxygen content and inclusions in 2507 duplex stainless steel, ingots with different Al contents were melted using a laboratory vacuum induction furnace. The O content in the steel was detected, and the morphology, composition, and size of inclusions were observed using a scanning electron microscope and an energy spectrometer.The results were statistically analyzed, and the effect of Al content on the type and content of inclusions was calculated using FactSage software. In the study of the effect of Al content on O content, it was found that the O content in steel first decreased rapidly with the increase of Al content, and the O content was kept at about 0.001 mass% when the Al content was 0.1 mass% to 0.3 mass%, and gradually increased with the increase of Al content. In the study of the effect of Al content on inclusions, it was found that at w(Al_t)≤14×10^-6, Al in the steel is not enough to generate Al₂O₃ inclusions, and Si, Mn and Cr elements will react with O to generate SiO₂-MnO-Cr₂O₃ inclusions; when the Al_t content is 44×10^-6, in addition to the SiO₂-MnO-Cr₂O₃ class inclusions,aggregated Al₂O₃ inclusions began to appear in the steel, and at the same time, SiO₂-MnO-Cr₂O₃ inclusions that were not completely reduced by Al due to the lack of Al were observed; when the Al_t content was higher than 98 ×10^-6, the Al in the liquid steel was sufficient to reduce all of the SiO₂-MnO-Cr₂O₃ inclusions, and all the inclusions observed in the steel were Al₂O₃ inclusions. In addition, the sizes of inclusions in steel at different Al contents were counted, and it was found that the average size of SiO₂-MnO-Cr₂O₃ inclusions was larger than the average size of Al₂O₃ inclusions when the Al content in steel was low, while the maximum and average sizes of Al₂O₃ inclusions gradually increased with the increasing Al content in steel. According to the results of thermodynamic calculations, in order to obtain 2507 duplex stainless steel with lower O content and smaller inclusions size, it is necessary to control the aluminum content of steel above 72×10^-6.

In order to improve the effect and efficiency of cold straightening of plate in medium plate production line, an analytical model of nine-roll cold straightening process was established based on curvature integration method. The influence of different plate factors and process strategies on the main parameters such as curvature ratio and straightening force was discussed. It was verified that the total straightening force deviation of the model was within 10%. With this model, the influence of different plate factors on straightening force and residual curvature was analyzed. Among them, the influence of steel grade and plate thickness is greater, and that of initial curvature ratio is smaller. With this model, the influence of the reduction of No.1, No.2, No.8 and No.9 straightening rollers on the straightening was analyzed. Among them, the residual curvature ratio and the total straightening force increase with the increase in the reduction. The No.8 roller has the strongest ability to control the residual curvature ratio after straightening, and the No.2 roller has the greatest influence on the total straightening force.In contrast, the effects of No.1 and No.9 rollers are small.Referring to this research results, the field straightening strategy is adjusted. The proportion of plates that need to be straightened for 3 passes or more is reduced from 30%-35% to 10%-15%.

The plate DC53/42CrMo composite casting billet was successfully prepared by electroslag remelting equipment. After annealing at 750 ℃, the microstructure, composition and interfacial element transition were studied by OM, SEM and EBSD, and the mechanical properties at the bimetal composite interface were characterized. The results show that the prepared DC53/42CrMo bimetallic composite casting billet has good bonding without slag inclusion and porosity. Element diffusion occurs at the composite interface, in which element C diffuses upslope from the 42CrMo side with low C content to the DC53 side with high C content. During the bimetallic liquid-solid recombination process, the activity of C in 42CrMo is much higher than that in DC53. On the 42CrMo side, there is a ferrite matrix + lamellar pearlite structure. On the 42CrMo side, there is a heat affected zone with a width of about 100 μm near the binding interface, and on the DC53 side, there is an element diffusion affected zone with a width of about 30 μm. The DC53 side is composed of pearlite matrix and undissolved carbide. The microhardness of the composite decreases first from 42CrMo to DC53, and then increases. The hardness of the heat-affected zone on the 42CrMo side is the lowest, with an average hardness of 192.9HV. The average tensile strength of the interface of the composite sample is 632.73 MPa and the shear strength is 586.12 MPa. The tensile fracture position of the composite sample is located at the 42CrMo side rather than the bonding interface, indicating that the bimetal interface is not a weak area and the interface bonding performance is good. The internal relationship between interface structure and properties was investigated, which provided reference for the preparation of bimetal composite cutter ring.

With the development of blast furnace ironmaking technology, the rising price of raw materials and fuels, and the proposed goal of“double carbon”, the development and application of metallized charge have become a hot research topic in recent years. The types and source of different metallized charges were introduced, the physicochemical characteristics and compositions of typical metallized charges were compared, and the utilization status of metallized charges in a blast furnace was analyzed. The metallized charges mainly include scrap, direct reduction iron(DRI), ferro-coke, and metallized sinter, etc. Scrap and DRI have higher iron grades than traditional iron ore and have good metallurgical properties. However, the shape of scrap is different, and its composition is complex, limiting its utilization. Thus, it is necessary to establish a unified industry standard to guide the rational utilization of scrap in a blast furnace. The use of DRI in blast furnace smelting has a remarkable effect of increasing production and reducing carbon emission, but it is expensive. New metallized charges, such as ferro-coke and metallized sinter, are mainly in the basic research stage at present and have not been applied in large-scale industrial practice. The physicochemical properties of various metallized charges are quite different. Suitable particle size, regular shape, and good metallurgical properties are usually required when added to the blast furnace. And the harmful element content should be controlled within a reasonable range. A large number of production practices at home and abroad have shown that the use of metallized charges can reduce the reducing agent ratio of blast furnace production, thereby improving production efficiency and reducing CO₂ emissions; with every 10% increase in the addition of metallized charges, the output of hot metal is increased by about 8%, and the CO₂ emissions of ironmaking system are reduced by 6%. To sum up, the metallized charge has a wide application prospect in blast furnace, and is one of the effective measures to achieve the goal of “double carbon” in the steel industry.

Under the background of the “Carbon Neutrality 2060” initiative, the significance of studying the application of steel slag carbon capture is self-evident. To enhance the comprehensive utilization of steel slag resources and reduce CO₂ emissions during the steelmaking process, wet leaching technology was employed to extract Ca and Mg components from steel slag. Focusing on the resulting Ca-Mg-Si-Al system, experimental studies were conducted to prepare CO₂ adsorbents using three different methods: chemical co-precipitation, sol-gel, and hydrothermal synthesis. The physicochemical properties and cyclic adsorption performance of the adsorbents were characterized and analyzed by XRF, XRD, SEM, BET, and other detection methods. The results indicated that, compared to other two methods, the adsorbent prepared by the chemical co-precipitation method under conditions of 50 ℃, pH=10, and an aging time of 2 h exhibited a higher initial adsorption capacity of 0.258 g/g. Different preparation methods demonstrated various patterns in the cyclic adsorption performance of the CO₂ adsorbents. The adsorption capacity of the adsorbent prepared by the chemical co-precipitation method showed a decreasing trend with an increase in the number of cycles, while the adsorbent prepared by the hydrothermal synthesis initially exhibited an increase followed by a decrease in adsorption capacity.

Different temperature annealing treatments of non-magnetic structural steel hot-rolled sheets were used to study the changes in microstructure, mechanical properties and magnetic properties. The results show that with the increase in annealing temperature, the tensile strength of non-magnetic structural steel hot rolled plate shows a decreasing trend, and the elongation increases slowly. A large number of deformation twins are generated within the austenitic grains of non-magnetic structural steel in different states after stretching, and these deformation twins can obstruct the dislocation motion and crystalline slip, which increases the hardness of non-magnetic structural steel. The XRD analysis shows that the hot rolled non-magnetic structural steel sheets did not induce phase transformation after annealing at different temperatures. Meanwhile, the magnetic permeability test results show that the relative magnetic permeability fluctuates between 1.002 18 and 1.002 06, which meets the requirements of non-magnetic structural steel for magnetic properties.

When low-pressure carburizing technology is applied to the third-generation ultra-high-strength gear steel, there still exist process problems such as carbide aggregation, austenitic soft layer, contradiction between carburized layer quality and thickness. This study investigates the effect of the introduction of the "double carburizing" process on the quality of the carburized layer, hardness and microstructure of 1900 MPa aerospace low-pressure carburized gear steel. SEM, XRD, EPMA, EBSD and TEM techniques were employed to precisely characterize the microstructure from carburized layer to core. The results show that after the introduction of the "double carburizing" process, no network distributed carbides existed, the overall carbon content of carburized layer increased, and the hardness of carburized layer increased by ~20 HV. The micron-sized block or strip shaped Cr-rich carbides at the same depth position increased, and this type of carbides located in the surface layer was mainly transformed from M₂₃C₆ to M₇C₃. The submicron-sized spherical M₆C carbides slightly decreased in quantity, meanwhile substantial amounts of submicron-sized M₂₃C₆ carbides, nanometer-scale MC and M₆C carbides are generated. At the same time, the carburized shell layer thickens and the transitional layer narrows. In addition, the hardness of the core of the "double carburizing" specimen is slightly reduced due to the decrease in dislocation density.

The mechanical properties of rolled plate will be significantly reduced if the shrinkage holes of continuous casting slab are not completely healed during rolling process. With the samples from slab, intermediate slab, and plate of E355 pipeline steel, the industrial computed tomography (CT), scanning electron microscope (SEM), and optical microscope were applied to analyze the shrinkage holes evolution in the rolling process. The results show that the slab surface layer has a dense solidification structure, where the shrinkage hole appears to be small size and single type. With the distance from the slab surface increasing, the number density of shrinkage holes rises, the size is enlarged, and it becomes the through type holes. The number density of shrinkage holes in the slab center is 5.510 mm^-3, the volume rate increases to 2.191‰, and the average and maximum sizes are 0.140 and 1.493 mm, respectively. After rough rolling process, the shrinkage hole extends along the rolling direction, the size decreases, and the number density increases. In the center of the intermediate slab, the number density is 61.744 mm^-3, the volume ratio is 0.395‰, and the maximum and average diameters are 0.038 and 0.023 mm, respectively. No large-size holes are found in the final plate, and the shrinkage holes are completely welded during finishing rolling, but the small-size holes are still observed near the MnS inclusions.

The steel metallurgy industry is a crucial component of the basic industries, where the quality stability of sinter is vital to the entire production process. A novel online prediction framework, the Process Feature Serialization and Extraction Prediction model (PFSE) is proposed to predict the FeO content in the sinter accurately. The framework first serialized and differentiated the raw data to enhance its expressiveness. Subsequently, it employed feature extraction techniques such as Grey Relational Analysis (GRA) and Correlation Coefficient (CC) to identify key process characteristics. Then, a prediction model for FeO content was constructed using Recurrent Neural Networks (RNN) and its variants, such as Long Short-Term Memory (LSTM) networks and Gated Recurrent Units (GRU). Experiments conducted on sintering process data from a steel plant between 2022 and 2023 validated the PFSE framework, demonstrating good stability and accuracy. With an error tolerance of 0.1, the model achieved a high accuracy rate of 85.3%. which confirms the effectiveness and reliability of this method.

Gear and bearing are two kinds of key parts in mechanical equipment, which are often broken due to fatigue, and their fatigue strength is the key performance index. The torsional fatigue behavior of BG801 gear bearing steel with four kinds of carburized layer depths was studied in order to clarify the fatigue cracking mechanism of carburized gear bearing steel and establish a rapid fatigue strength evaluation method on the basis of it. The results show that the carburizing layer of BG801 gear bearing steel is mainly composed of martensite and a large number of long-strip or elliptic carbides. The fatigue cracking is caused by cleavage cracking of large size carbide clusters. The crack initiation plane is 45° from the loading axis and is dominated by normal stress. Based on this, a method for evaluating the fatigue strength of carburized gear bearing steel is proposed, which can predict the fatigue strength under long life conditions by high stress and short life samples. For the materials studied, the prediction error is about 10%, which is conservative.

To develop and promote the application of new weathering bridge steel, the effect of Ni on the corrosion behavior of Q690qENH weathering bridge steel in industrial atmosphere was studied by using the accelerated corrosion test and electrochemical test methods, combined with scanning electron microscopy (SEM), X-ray diffraction (XRD), electron probe (EPMA) and X-ray photoelectron spectroscopy (XPS). The results show that the addition of Ni can improve the corrosion resistance of Q690qENH steel in industrial atmosphere. The addition of Ni can improve the self-corrosion potential of Q690qENH steel and increase the resistance of rust layer. Ni is distributed uniformly in the rust layer, mainly in the form of NiFe₂O₄. On the one hand, NiFe₂O₄ improves the ion selectivity of the rust layer and prevents SO₂ from penetrating into the substrate. On the other hand, it promotes the transformation of γ-FeOOH to α-FeOOH in the rust layer. With the increase of Ni content from 0.31% to 0.52%, the enrichment of S in the rust layer decreases obviously, the protection index α/γ^* value of the rust layer of Q690qENH steel increases, the corrosion rate decreases, and the corrosion resistance improves.

With the development of electric arc furnace, the demand for direct reduced iron will also increase. The use of low temperature reduction to optimize magnetite is an important source of direct reduced iron. In order to study the mechanism of Fe₃O₄ reduction promoted by high volatile matter in coal, the pyrolysis gas composition and pyrolysis characteristics of Guanghui coal were analyzed. The pyrolysis of Guanghui coal and Fe₃O₄ reduction were studied by non-isothermal kinetics analysis method. The activation energy of the reaction was calculated by FWO, KAS and Starink methods. The Satava-Sestak method was used to fit the reaction model. The difference of kinetic mechanism of Fe₃O₄ reduction between activated carbon and coal was emphasized. The results show that the retorting gas of Guanghui coal is mainly composed of H₂, CH₄, CO and CO₂. In the reduction temperature range, the H₂ content and CO content of coal pyrolysis can reach 55 and 25 vol.%,respectively,which provides a good atmosphere for the reduction of Fe₃O₄. The temperature range of activated carbon reduction of Fe₃O₄ is 980-1 140 ℃, and the initial activation energy is 319.66 kJ/mol, while the reduction temperature range of Guanghui coal is 680-1 030 ℃, and the initial activation energy is 288.62 kJ/mol. The results show that the high volatile matter in Guanghui coal plays a catalytic role in the reduction process and significantly reduces the reduction temperature and activation energy.

Hardenability is a key performance parameter of steel materials, reflecting the ability of steel to achieve uniform hardening during the quenching process, which directly affects the mechanical properties and service life of the steel. Traditional physical models have limited accuracy in predicting hardenability due to their inability to handle complex compositions and process parameters accurately. The application of machine learning models such as Support Vector Machine (SVM), Decision Tree (DT), Neural Network (NN) and deep learning in the prediction of steel hardenability is reviewed, and the prediction accuracy, data requirements and computational efficiency are compared and analyzed. The future research directions are prospected, including key issues such as improving data quality, fusion model and enhancing physical interpretability. With the continued development of machine learning technology, the accuracy and generalizabilityof hardenability prediction are expected to be significantly improved, providing strong scientific support for the intelligent production of steel in the industry.

In the process of Basic Oxygen Furnace (BOF) smelting, accurate prediction of the carbon content in molten steel within the bath represents a pivotal aspect of endpoint prediction technology. However, deciphering the profound correlation between the characteristics of the furnace mouth flame and the final carbon content to achieve more precise predictions remains a prevailing challenge. To address the issue of flame texture irregularity and high similarity under varying carbon contents, a multi-directional weighted complex network (MDWCN) model is established for extracting color texture features. This model employs a sliding window to select neighboring vertices around a central point, thereby establishing neighborhood relationships. Weighted edges are constructed using color distances between vertex pairs, leading to the formation of detailed color texture and regional color texture complex networks. Ultimately, the network's vertex degree distribution characteristics are utilized to quantify network properties, yielding a color texture feature descriptor. This descriptor, combined with extracted color features, forms a flame feature descriptor, enabling the prediction of final carbon content through a regression model. The effectiveness of the proposed method has been validated through experimental investigations using actual production data from converter steelmaking.