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.

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.

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.

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.

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 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 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.

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.

Sulfur (S) and phosphorus (P), as typical harmful impurities in steel materials, significantly influence the forming quality and service performance of welds in advanced steel materials. In terms of forming, S affects the shape and contour of the weld pool by altering its flow characteristics and surface tension, while P primarily modifies the surface tension of the molten metal, thereby influencing the spreading behavior and wettability of the weld pool on the base material. In terms of performance, S readily forms low-melting-point sulfide inclusions that accumulate at grain boundaries, not only increasing susceptibility to hot cracking but also severely degrading the toughness and plasticity of the weld metal. P, on the other hand, undergoes significant grain boundary segregation during solidification, weakening the bonding strength of grain boundaries. This serves as a source for crack initiation and propagation and significantly reduces the toughness and strength of welded joints. This article reviews the impact of S and P elements on weld formation and performance based on the latest research and summarizes current control strategies for both elements.

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.

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%).

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 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.

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.

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.

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.

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%.

Micro-grain casting process can strengthen alloys under medium and room temperature by refining grains. However, the increased transverse grain boundaries may deteriorate the stress rupture and creep proprieties under high temperature creep conditions, leading to premature failure of components. In this work, stress rupture tests under 760 ℃/724 MPa were conducted on K447A alloys produced by conventional, fine-grain and micro-grain casting processes. The original and deformed microstructures were characterized by SEM, EDS and ECCI. The effect of micro-grain casting process on the stress rupture property of K447A alloy was studied and discussed. Results show that the stress rupture life of micro-grain casting K447A alloy is increased to 194 h, which is 134% and 69% higher than that of the conventional and fine-grained ones, respectively. The deformation is dominated by dislocation shearing, and cracks initiate on the sample surface and propagate transgranularly. The refined grains and carbides, the increased γ′ volume fraction and the disappeared dendrite structures induced by micro-grain casting process effectively inhibit crack initiation and propagation, significantly improving the stress rupture life of K447A alloy under this condition. Intergranular oxidation cracks along grain boundaries are observed in micro-grain K447A alloy, while their detrimental effect on mechanical property is much weaker than that of strengthening effect induced by grain refinement, thus significantly improving the stress rupture property of K447A alloy.

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.

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%.

The surface adsorption principle of H₂ on two crystal surfaces of Fe₂O₃(0 0 0 1) and Fe₂O₃(1 $\bar{1}$ 0 2) is investigated by a first-principles approach based on Density Functional Theory (DFT). The study focuses on the adsorption mechanism, adsorption energy, and electronic structure analysis of the H₂/Fe₂O₃ system. The results show that the adsorption of H₂ on the crystal surfaces of Fe₂O₃(0 0 0 1) and Fe₂O₃(1 $\bar{1}$ 0 2) are physisorption, with the vertical adsorption at the top of the vacancies being more stable than the other positions, and the adsorption energies of the adsorption are 20.99 and 26.44 kJ/mol, respectively. The interaction between H₂ and the crystal surface is mainly due to the orbital overlap hybridization effect between H and Fe, and the exchange, recombination, and energy conversion of electrons between the two occurs through the Mulliken charge fabrication analysis. The adsorption of H₂ to Fe₂O₃(0 0 0 1) and Fe₂O₃(1 $\bar{1}$ 0 2) produces H₂O, which needs to be dissociated from O atoms of the crystal surface across the energies of 1.999 and 2.496 eV. The dissociation of H₂O from O atoms on the crystal surface requires crossing an energy barrier of 1.999 and 2.496 eV, respectively, and releasing 1.894 and 1.573 eV of energy. The relatively high adsorption energy of H₂ on the crystal surface of Fe₂O₃(1 $\bar{1}$ 0 2) suggests that the adsorption of H₂ on Fe₂O₃(1 $\bar{1}$ 0 2) is more facile and stable. The energy barriers for the dissociation of the H₂O molecule from Fe₂O₃(0 0 0 1) are lower than those for Fe₂O₃(1 $\bar{1}$ 0 2), which implies that the reaction products on the crystal surface of Fe₂O₃(0 0 0 1) are more easily and steadily adsorbed. Fe₂O₃(0 0 0 1), implying that the reaction products dissociate more easily in Fe₂O₃(0 0 0 1).

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.

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.

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.

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.

The 862 MPa high-strength oil well tubing, known for its exceptional strength, toughness, and corrosion resistance, is particularly suitable for severe conditions containing high concentrations of CO₂,H₂S, and elemental sulfur. The effects of the initial microstructure on the properties of 862 MPa high-strength oil well tubing steel prior to the quenching and tempering heat treatment were investigated. The microstructures and properties after same heat treatments were compared for different initial microstructures. The findings reveal that the martensitic initial microstructure with a high density of crystal defects exhibited a significant reduction in martensite lath size by over 50% following quenching and tempering, achieving a simultaneous enhancement in strength and toughness through grain refinement strengthening. The morphology of Cr₂₃C₆ precipitates transitioned from intergranular chain-like structures to intragranular dispersed spherical structures, which increased the sulfide stress cracking critical stress intensity factor (K_ISSC) by approximately 10%. Further research indicates that the H₂S stress corrosion failure process of the material is the result of the synergistic effects of surface pitting and hydrogen-induced cracking.

Steel pipelines are key facilities for oil and gas transportation, and their structural integrity is crucial for securing energy supply. As an important means of failure analysis, fracture analysis techniques are valuable for revealing the causes of pipeline failure and preventing future risks.Four main fracture analysis techniques were systematically introduced, including compositional analysis, structural analysis, morphological analysis and inversion analysis, which reveal the causes of pipeline failure from different perspectives. The application of related fracture analysis techniques in pipeline failure analysis was further discussed, and the applicability of related techniques in pipeline failure analysis were compared. Results show that each technique has a specific scope of application, and its comprehensive use can significantly improve the accuracy of pipeline failure analysis and provide a scientific basis for pipeline design, maintenance and emergency response. Future research should focus on the comprehensive application of these techniques to cope with more complex working conditions and prevent the risk of pipeline failure on this basis.

The influence of MgO on the viscosity and free running temperature of laterite nickel ore smelting slag was investigated. The structural change of the slag was analyzed by Fourier infrared spectroscopy and Raman spectroscopy. Meanwhile, the heat capacity, enthalpy change and extreme heat release of laterite nickel ore smelting slag were calculated by thermodynamics. The results show that the viscosity of laterite nickel ore smelting slag decreases with the increase in MgO content, and the viscosity is lower than 1.0 Pa·s at temperatures higher than 1 450 ℃. The free running temperature increases slightly, which exhibits good fluidity. The heat capacity, enthalpy change, and the extreme heat release of laterite nickel ore smelting slag gradually increase with the increase in MgO content. The Q⁰ and Q¹ structural units in laterite nickel ore smelting slag increase, while the Q² and Q³ structural units decrease significantly. The average NBO/Si increases from 1.79 to 2.06 with MgO content. The slag structure becomes simpler and increases the fluidity. The addition of MgO can effectively improve the fluidity of laterite nickel ore blast furnace smelting slag, and has a positive effect on improving the thermal stability of laterite nickel ore smelting slag.

Ultra-low carbon silicon steel was prepared using a short process technology in a CO₂-CO atmosphere. The experiment focuses on a thin strip of Fe-0.1%C-3.5%Si alloy with a thickness of 0.5 mm. The thermodynamic equilibrium phase diagram of Fe-C-Si alloy thin stripwas calculated through thermodynamic software and solid-state decarburization experiments in CO₂-CO atmosphere were conducted. The results show that when the temperature is between 800 ℃ and 1 300 ℃ and the P_CO2/P_CO value is lower than 0.22, SiO₂ is preferentially generated in the cross-section of the thin strip. The comparison between surface XRD phase analysis and thermodynamic analysis shows that the results are basically consistent. When P_CO2/P_CO=0.08, the decarbonization effect is better when the carbon content is 0.005 97 wt.% after 10 min of decarbonization. The carbon content after decarburization at 1 150 ℃ for25 min is 0.002 62 wt.%, indicating good decarburization effect and meeting the carbon content requirements of ultra-low carbon silicon steel. The thinner the Fe-0.1%C-3.5%Si alloy ribbon thickness, the faster the decarburization rate and the faster the growth rate of the oxide layer. Calculations from the study of the kinetics show that the average carbon content of Fe-0.1%C-3.5%Si alloy thin strips with different thicknesses varies exponentially with time; the decarburization of Fe-0.1%C-3.5%Si alloy thin strips of 1 mm in thickness by gas-solid reaction can be approximated as an apparent first-order reaction, and the apparent decarburization rate constant k can be approximated as 0.083 49.

With the development of information technology, fully mining, screening and analyzing the big data of steel production is of great significance for achieving intelligent control, energy conservation and efficiency improvement in steel production. Through in-depth analysis of 425 groups of real-time test data of furnace gas composition of a 200 t converter in a steel plant, based on the carbon integral model, it is transformed into carbon composition and temperature time series data, and the data are normalized and preprocessed.A Long Short-Term Memory (LSTM) network model was developed to predict carbon mass fraction and temperature during the steelmaking process, with feeding and flue gas information serving as input variables. By comparing the measured end-point data from 50 production batches with the model′s predicted values, the results show that the hit rate of the end-point prediction error of the carbon mass fraction within ±0.03% is 96%, and the hit rate of the end-point prediction error of the temperature within ±15 ℃ is 92%. The deviation between actual and predicted values from the LSTM model is minimal, and the end-point hit rate within the specified range surpasses that of ELM and BP models. The LSTM model is beneficial to the dynamic prediction and control of smelting process.

Iron coke as a new type of low-carbon ironmaking raw material, has a good reactivity. The use of appropriate amount of iron coke in blast furnaces (BF) can improve gas utilization efficiency and strengthen energy conservation and carbon emission reduction. Iron coke needs to have high mechanical strength and high reactivity to meet the requirements of production, transportation, and low-carbon blast furnace smelting of iron coke. Carbonization treatment is a key process for the transformation of iron ore-coal mixture into iron coke, which has a significant impact on the metallurgical properties of iron coke, such as mechanical strength and reactivity. The study of pyrolysis behavior and carbonization consolidation mechanism of iron coke is crucial for optimizing the metallurgical properties of iron coke. The research progress of pyrolysis behavior and carbonization consolidation mechanism of composite iron coke was reviewed. The current research results, the contents that need to be further studied and the prospect of theoretical research on iron coke carbonization consolidation were analyzed and summarized. To a certain extent, the key theoretical basis for the pyrolysis behavior and carbonization consolidation mechanism of iron coke has been summarized, which will theoretically clarify the carbonization process of iron ore-coal mixture into iron coke, promote the optimization of carbonization process technology path of iron coke, and advance the technology of iron coke preparation and its use in BF smelting.

To facilitate the construction of new-type power systems and achieve carbon peaking/carbon neutrality goals, new-generation coal-fired peak-shaving units have been extensively deployed, exposing key high-temperature components to damage mechanisms dominated by creep-fatigue interaction. Based on current design codes and material test data including P91/P92 etc., this study systematically investigates temperature, stress, and load variations in boiler thick-walled components under both steady-state and flexible peak-shaving operations. Comparisons reveal critical discrepancies between laboratory high-stress creep/fatigue testing conditions and actual low-stress service environments with frequent load fluctuations. The mechanisms governing how stress levels, temperature ranges, and load variation parameters such as amplitude, frequency and ramping rate influence creep void evolution, fatigue crack propagation, and coupled creep-fatigue damage are thoroughly elucidated. Results demonstrate that transient thermal stresses and localized plastic strains intensify substantially under peak-shaving conditions, causing a paradigm shift in dominant failure modes from time-dependent creep failure under steady-state operation to complex damage patterns dominated by low-cycle thermal fatigue and creep-fatigue interaction. The proposed countermeasures, informed by engineering failure cases, encompass the adoption of advanced alloys such as G115 and C630R for their superior creep-fatigue resistance, geometric optimization to mitigate stress concentration, and the implementation of online life-assessment systems. Crucially, establishing near-service creep-fatigue interaction test protocols, developing multi-factor coupled damage models, and formulating material selection guidelines tailored for peak-shaving units are identified as essential strategies to ensure long-term operational safety and reliability.

Iron and steel is a pillar industry in China, and the production quality of steel products is key to the performance andprice. In order to solve the problems of poor accuracy, low efficiency and complex model structure in strip surface defect detection, we proposed a lightweight strip surface defect detection algorithm based on YOLOv11 (PSN-YOLO). Firstly, the P-GELAN_CAA feature extraction-fusion module was designed, and PSConv was introduced based on GELAN to process multi-scale information, optimize parameter utilization, and integrate CAA to enhance feature representation. Secondly, the lightweight and efficient SCDown downsampling was selected to expand the receptive field, reduce the information loss, and reduce the complexity of the model. Finally, NWD is used to improve the loss function of the bounding box, focusing on irregular and complex micro-texture features, so as to better measure the distribution similarity between the bounding boxes and improve the detection accuracy. Experimental results on the NEU-DET dataset show that compared with the benchmark model, the mAP of the proposed model is increased by 3.1%, and the number of parameters and computation are reduced by 20.3% and 19.0%, respectively, which better balances the detection accuracy and lightweight requirements. In addition, the model shows good generalization ability on the Severstal dataset, which meets the practical engineering needs and has important application value.

In the context of China′s “dual carbon” policy, the iron and steel industry is confronted with significant challenges in energy conservation and consumption reduction. The recovery of waste heat from blast furnace slag and the efficient utilization of coal are considered crucial for promoting the green development of the iron and steel industry. Thermodynamic and energy utilization studies were conducted on coal gasification reactions driven by blast furnace slag waste heat. A thermodynamic model for the coal gasification reaction was established based on the principle of minimizing Gibbs energy. The effects of the gasification reaction under varying temperatures,n(H₂O(g))/n(C) ratios, and pressure conditions were explored, leading to the identification of optimal operating conditions. At 1 073 K, with an n(H₂O(g))/n(C) ratio of 2.00 and a pressure of 0.10 MPa, the total syngas production was found to be 3.28 kmol, with a carbon conversion rate of 0.93 and a syngas production rate of 1.56. Additionally, a comprehensive analysis method incorporating both energy analysis and exergy analysis was employed to evaluate the energy utilization efficiency of the coal gasification reaction. The results indicated that the energy efficiency of the coal gasification reaction reached 73.22%, with an exergy efficiency of 70.81%.

The effect of the quenching-partitioning-tempering (Q-P-T) process on the microstructure evolution laws and regulation mechanisms of mechanical and forming properties for cold-rolled Q&P980 steel at 285, 310 and 335 ℃ quenching temperatures has been investigated. The results indicate that increasing quenching temperature promotes the transformation of martensite morphaology from coarse blocky structures to uniformly distributed fine laths. The volume fraction of retained austenite and its carbon content exhibit a trend of first increasing and then decreasing, with the optimal mechanical properties achieved at a quenching temperature of 310 ℃. An increase in quenching temperature leads to a decrease in hole expansion rate,plastic strain ratior-value, and limiting forming curves, while the plastic anisotropy index(Δr-value) shows an upward trend. At a quenching temperature of 285 ℃, strong recrystallized {111} texture and high-angle grain boundaries weaken the planar anisotropy caused by grain orientation differences, resulting in the best forming performance. Quenching at a temperature of 335 ℃ resulted in the deterioration of the material′s formability, which is attributed to the presence of a strong α-fiber texture coupled with a decrease in the intensity of the γ-fiber texture. It is indicated that while there is a certain correlation between forming performance and mechanical properties, more attention should be paid to the influence of texture types and their microstructural distribution on forming performance.

The long-term corrosion behavior of 12Cr13 steelwas investigatedin a static oxygen saturated liquid lead-bismuth alloy at 450 ℃ for 6 000 h. The morphology, composition, and corrosion kinetics of the oxide film during the corrosion process were analyzed. The results indicate that the growth rate of the oxide film on 12Cr13 steel is slow, and the thickness of the oxide film follows a parabolic law. After3 000 h of corrosion, a typical double-layer structure oxide film forms with an inner layer of Fe-Cr spinel and an outer layer of Fe₃O₄. The diffusion of Cr at the micron scale plays a crucial role in forming the surface oxide film and inward steady progression of the inner oxide layer. Additionally, there is an evidence of peeling-off phenomenon in the oxide film after 3 000 h, which may be associated with unevenness on original corroded sample surfaces. Based on these experimental findings, a corrosion model for 12Cr13 steel in liquid lead-bismuth was proposed.

Technical means such as SEM, TEM, XRD, and EBSDare usedto systematically study the effects of nickel and cobalt elements on the new NiCrMoV hull steel microstructure, second phase, and properties. The results showed that after quenching and tempering, the steel structure was composed of tempered martensite and a spot of reversed austenite, and during the tempering process, a fine-needle Mo-Cr-V-rich M₂C phase was mainly precipitated. Afterquenching at 850 ℃ and tempering at 580 ℃, theyield strength of new NiCrMoV steel can reach 1 140 MPa, and -84 ℃ low temperature impact effect reaches 76 J. With the increase of Ni content in steel, the grains are refined, the large angle grain boundaries increase, and the reversed austenite increases, which effectively obstructs the propagation of cracks and further improves the low-temperature toughness to 82 J. After adding the Co element in the test steel, the dislocation density is increased, and the precipitated M₂C phase increases and becomes more dispersed, which effectively improves the ultra-high yield strength of the test steel to 1 216 MPa.

Microstructural evolution and Invar effect of Fe_42.7Co_39.6Cr_8.6Ni_9.1 high-entropy alloy were investigated. After 50% cold rolling, alloy was annealed at 800, 900 and 1 000 ℃. Microstructures were characterized using electron backscattered diffraction, while Invar effect was analyzed using dilatometer. Results indicate that FCC grain size generally increases with increasing annealing temperature and time; static recrystallization model is established and activation energy is determined to be 109.5 kJ·mol^-1, which is similar to high-entropy alloys in the CoCrFeMnNi alloy system. During cooling after annealing, FCC→BCC martensitic transformation takes place; nucleation and growth of BCC are affected by grain boundaries and other factors, so the evolution of BCC fraction with annealing condition is complicated. Additionally, Invar effect is confirmed between 27-218 ℃. It is because the spontaneous magnetostriction effect of ferromagnetic FCC phase counteracts with volume expansion partially caused by lattice vibration. When BCC fraction increases from 5.6% to 25.2%, thermal expansion coefficient decreases from 3.8×10^-6 to 3.3×10^-6 ℃^-1. This indicates that thermal expansion coefficient only slightly changes; therefore, mechanical properties can be tuned through microstructural control while still keeping Invar effect.

Nb can significantly improve the strength and toughness of niobium-containing steel due to its grain refinement crystal and precipitation strengthening effects. However, it can also cause the crack sensitivity if the Nb-containing precipitates occur at the austenite boundary, which will be the stress concentration point. To solve the problem of crack defects on Nb-containing alloy steel during the continuous casting process, the evolution mechanisms of microstructure and precipitates in Nb-containing alloy steel were investigated under controlled cooling conditions. Results show that the γ→α phase transformation appeared first at the austenite boundary when the temperature decreased. This phase transformation also occurred within the interior of the austenite grain with the further decrease in the temperature. Meanwhile, the second phase precipitates formed at the grain boundary area when the temperature reached around 1 000-1 200 ℃. EDS analysis results suggest that Nb and N content in precipitates reduced with the increase in the cooling rate, the average content of Nb reduced from 9.81 to 5.49 wt.%, and that of N reduced from 1.4 to 0.57 wt.%, when the cooling rate increased fromto 20 ℃/s. Generally, the main second-phase precipitates were NbN and NbC. These results also indicate that the precipitation of Nb-containing precipitates can be inhibited, and the ratio of crack defects on the slab can be reduced when the cooling rate is enhanced.