Under the strong impetus of the global“dual-carbon” strategy, the green transformation of the metallurgical industry is imperative. Blast furnace smelting technology with a high pellet ratio has emerged as a key research focus.High-silicon magnesium flux pellets is concentrated, examining their current research status and development trends. Pellets demonstrate significant advantages in low-carbon environmental protection. Their production entails low energy consumption and minimal pollutant emissions. Featuring high iron grade, uniform particle size, and low sulfur content, pellets create favorable conditions for low-carbon and stable blast furnace operation.It effectively advances the energy conservation and emission reduction efforts in the steel industry. High-silicon magnesium flux pellets exhibit distinctive characteristics. Utilizing high-silicon iron ore expands resource options and reduces costs. MgO enhances slag fluidity, facilitating desulfurization. Furthermore, flux pellets contain inherent flux components, which lower costs and improve pig iron quality. However, in blast furnace smelting with high pellet proportions, noticeable changes occur in burden distribution as the pellet ratio increases. The characteristics of the softening-melting zone also alter. Although the melting-dripping performance improves, the temperature of the softening-melting zone rises and its width expands, thereby disrupting gas flow. The slag system is significantly influenced by pellet composition. Variations in gangue elements such as silicon and magnesium modify the slag system’s composition and properties, consequently affecting desulfurization efficiency. Synthesizing existing research, blast furnace smelting technology with high pellet ratios, while promising, still confronts numerous challenges. Future research should prioritize optimizing pellet production processes, precisely regulating blast furnace operational parameters and innovating burden structure design. These efforts will establish a technical foundation for the sustainable development of the steel industry and contribute to the steady realization of the “dual-carbon” goals.

The deep-bed sintering technology, which fully exploits the heat storage effect of the sinter bed, has significant advantages in greatly reducing the solid fuel consumption, improving sinter yield and quality. It has become one of the effective measures for reducing carbon emissions and strengthening the sintering process of ore blends with high-proportion of goethite-type iron ores.The thermal state of the condition of deep-bed sintering and basic properties of materials in each reaction zone under deep-bed sintering conditions in terms of four typical ore blends with different proportions of magnetite and hematite concentrates was mainly investigated. Conventional sinter pot tests were carried out to acquire samples for mineralogical studies using optical microscopy and X-ray diffraction analysis. The results show that at a fixed bed height of 900 mm, the combustion zone possesses thickness of 100-180 mm, high-temperature retention time (above 1 200 ℃) of 3-7 min, and maximum temperature of 1 350-1 400 ℃. The fine ore sinteringis characterized with a narrower combustion zone, longer high-temperature retention time, and a lower cooling rate, which is more conducive to obtaining better sinter quality and output indicators. However, addition of fine iron ore concentrates, results in widening in the thickness of the combustion zone, a decrease in the heating rate of the sinter bed, and an increase in the cooling rate. Consequently, the formation of complex calcium ferrite is restricted, and the sinter bed is more prone to collapse and form a “large pore and thin wall” sinter structure. The properties of the combustion zone in the deep-bed sintering process of different ore blends are similar, while the high-temperature cooling zone is the key stage determining the sinter strength.

The peephole of the lower tuyere of the blast furnace can monitor the key smelting status information such as the combustion characteristics and coal injection status of the blast furnace raceway in real time and then judge the important parameters such as gas flow distribution and hearth activity. To address the issues of subjectivity and time lag in tuyere monitoring,an intelligent blast furnace tuyere monitoring model TI-ViT was developed, based on unstructured big data from tuyere images and the Vision Transformer architecture. First, the collected tuyere images were preprocessed, and a typical furnace condition dataset was constructed through feature discrimination and label annotation. Subsequently, the TI-ViT image recognition model was built based on the Vision Transformer architecture. Finally, the performance of the TI-ViT model was evaluated, with a focus on investigating the impact of model depth on accuracy, parameter count, training time, and inference time. A comparison was also made with traditional convolutional neural network (CNN) models. Experimental results show that the TI-ViT model achieved an accuracy of 97.7%, which is 9.1% higher than that of the CNN-based model, with an inference time of only 15.75 ms per image. The "Smart Eye" system, developed based on this model, was applied in field practice and achieved an identification accuracy of 95.2%. This demonstrates that the system enables real-time monitoring, recognition, and early warning of blast furnace tuyere conditions, helps reduce the cost of monitoring and diagnosing abnormal tuyere states for iron and steel enterprises, and provides a new direction for the intelligentization of blast furnace ironmaking.

The temperature and carbon content of molten steel are regarded as critical indicators at the converter endpoint.The accurate prediction of carbon temperature is beneficial to improve the end-point hit rate, reduce the end-point peroxidation, improve the alloy yield, and promote the high efficiency and low cost smelting of the converter.In order to improve the prediction accuracy of carbon content and temperature at the end-point of converter steelmaking, a support vector machine (SVM) model combined and optimized by various algorithms was proposed. Factor analysis was used to screen and reduce the dimension of the characteristic parameters. The prediction model of carbon content and temperature at the end of converter steelmaking based on support vector machine extreme gradient boosting decision tree (SVM-XGBoost) was established, and compared with the basic model SVM, support vector machine optimized random forest (SVM-AdaBoost) and support vector machine optimized gradient boosting decision tree (SVM-GBDT). The results show that SVM-XGBoost has the highest hit rate. When the prediction error of the end-point carbon content of the converter is ±0.01% and ±0.02%, the end-point hit rates are 87.53% and 91.60%, respectively. When the temperature error is ±5 and ±10 ℃, the end-point hit rates are 76.47% and 92.20%, respectively. Compared with the SVM model, its hit rate within the error range of ±0.01% end-point carbon content increased by 14.26%, and the hit rate within the error range of ±5 ℃ end-point temperature increased by 7.74%. Compared with the other three models, the prediction results of SVM-XGBoost are more accurate, which has a good reference effect on the actual smelting process control and end-point rate improvement of the converter.

Aiming at the optimization of high-efficiency and low-cost production process and the improvement of intelligent level of electric furnace, a comprehensive intelligent steelmaking model system of electric furnace is constructed based on metallurgical principle, mathematical model and information technology. The intelligent steelmaking technology of electric furnace is introduced, and its application effect is analyzed. This technology deeply integrates the real-time online monitoring system such as visual image and audio recognition with the intelligent steelmaking process model of electric furnace, and constructs a digital, standardized and modeled smelting process control system. The industrial application data show that the average phosphorus content at the end point of the electric furnace shows a downward trend, and the average carbon mass fraction at the end point increases by 47.8%. The average total iron content in the final slag decreases by 11.9%, the peroxidation phenomenon is effectively suppressed, and the yield of molten steel is significantly improved. The smelting cycle of the electric furnace is shortened by 1.5 min on average, the power consumption per unit of molten steel is reduced by 15 kW·h /t on average, and the annual production cost is expected to be reduced by about 8.25 million yuan. Based on optimizing the quality of molten steel, this technology has realized the reduction of smelting cost and the improvement of smelting efficiency, which provides important technical support for the intelligent upgrading and green low-carbon transformation of the iron and steel industry.

In the process of electroslag remelting of rack steel, the consumable electrode will be oxidized at high temperature and short time before inserting into the slag surface. The oxidation products enter the slag pool with the electrode, which leads to the increase of oxygen potential and the burning loss of easily oxidized elements in the molten bath. However, it is difficult to formulate a reasonable deoxidation system due to the unclear oxygen increasing law.Therefore, it is urgent to systematically study the oxidation mechanism of the consumable electrode and establish the electrode oxidation mass gain model. Isothermal oxidation tests were carried out at 900, 1 000, 1 100, 1 200 and 1 300 ℃ in air atmosphere, respectively. The phase composition of the oxide scale was determined by X-ray diffractometer. The cross-sectional microstructure and cross-sectional element distribution of the rack steel were characterized by electron probe microanalysis. The evolution of the surface morphology of the sample, the formation of the precipitated phase and the distribution of the alloying elements were systematically studied. The formation mechanism of the oxidation products was analyzed by combining the oxidation kinetics law and the thermodynamic database, and the role and behavior of the alloying elements in the high temperature oxidation process were discussed. A multi-stage formation mechanism model describing the high temperature short-time oxidation of rack steel was established. Based on the results of isothermal oxidation test and the simulation results of electrode surface temperature field, the mathematical model of oxidation massgain of consumable electrode in electroslag remelting process of rack steel was established. The oxidation mass gain of electrode in a certain period of time was calculated, and the prediction results were verified by industry. The results show that the isothermal oxidation kinetics curve of rack steel in air atmosphere follows the parabolic law, and the activation energy of oxidation of rack steel is 197.17 kJ/mol. The oxide layer of the consumable electrode is mainly composed of Fe₂O₃, Fe₃O₄, FeO, SiO₂, TiO₂, Fe₂SiO₄ and FeCr₂O₄. Internal oxidation is more likely to occur at 1 200 ℃, which may be due to the penetration of molten Fe₂SiO₄ into the matrix and the exfoliation of the outer TiO₂, which provide channels for oxygen diffusion. The oxidation mass gain model of rack steel consumable electrode was established, and the quantitative prediction of electrode oxidation amount in different time was realized, which could provide theoretical basis for the development of deoxidation system. In order to verify the accuracy of the oxidation mass gain model, the amount of deoxidizer added was calculated according to the oxidation mass gain model in industrial production. The qualified rate of 80 furnaces was 97.5%. It is of great significance for clarifying the oxygen transport mechanism and formulating the deoxidization system in the electroslag remelting process, and can lay a theoretical foundation for the high-performance preparation of rack steel materials for marine engineering equipment.

Ductile iron pipes possess excellent strength and toughness, making them a primary material for urban water supply and heating systems. In the production of ductile iron pipes using centrifugal casting technology, controlling the wall thickness variation is a key challenge in industrial manufacturing, while achieving stable wall thickness variation serves as an important foundation for reducing the weight of the pipes without compromising their performance.ProCAST software to simulate and analyze the influence of process parameters on wall thickness variation during the production of centrifugal ductile iron pipes in a factory was utilized, providing a pathway for process optimization to control wall thickness variation. The results indicate that adjusting the pouring flow rate alters the axial velocity of the molten metal, thereby affecting its flow behavior. When the pouring flow rate is set at 32 kg/s, the optimal flow behavior of the molten metal is achieved. If the flow rate is lower or higher than this value, issues such as uneven mold filling or splashing of the molten metal are likely to occur. Additionally, the rotational speed of the pipe mold significantly influences the wall thickness uniformity of the cast pipe. As the rotational speed increases, the wall thickness uniformity gradually improves. In conclusion, the optimal process parameters are determined as a pouring flow rate of 32 kg/s and a pipe mold rotational speed of 600 r/min.

The 18CrNiMo7-6 gears are prone to failure due to factors such as wear, fatigue, and overload, with the failure areas mainly concentrated near the tooth tip and root. Through simulation of the 18CrNiMo7-6 gear die forging process,the tooth tip and root regions of the gear after die forging are stress concentration areas is found, with stress of 214.1 and 238.5 MPa, respectively. Along the direction from the tooth tip to the root, the equivalent strain increases from 1.53 to 1.97. By hardness measurements of the carburized sample from the surface to the core, it is found that the carburized layer depth and hardness in the tooth tip area are higher than those in the tooth root area. Subsequently, electron backscatter diffraction technology is used to analyze the microstructure of 18CrNiMo7-6 gears after carburization. Compared with the tooth root area, the proportion of low-angle grain boundaries in the tooth tip area is low, the dislocation density is high, and both the martensite grains and the reconstructed original austenite grains are fine. Therefore, from the microstructure analysis, the tooth tip area exhibits strong resistance to crack initiation and propagation.

Different microalloying elements, sintering processes, and heat treatment processes are key factors in controlling the properties of powder maraging steel. Therefore, the relative density, microstructure, mechanical properties of the maraging steel Fe-13Co-8Ni-8Cr-6Mo-0.4Nb-0.1Al after microalloying with Cu, V, and Ti under different sintering conditions (temperature and duration) were studied. Based on the theory of powder metallurgy sintering densification and microalloying, three types of maraging steel were fabricated using powder injection molding and sintered at 1 330-1 390 ℃ under vacuum. The microstructure was characterized by optical microscopy, scanning electron microscopy, and X-ray diffraction, and the mechanical properties were tested using a Vickers micro-hardness tester and a computer-controlled electronic universal testing machine, and the results show thatthe sample with V addition of 0.3%(mass fraction) sintered at 1 330 ℃ for 4 h achieved a hardness of 353HV and a yield strength of 675 MPa;the sample with Cu addition of 3%(mass fraction) sintered at 1 330 ℃ for 4 h exhibited an elongation of 50% with predominant dimples in the fracture morphology;the sample with Ti addition of 0.4%(mass fraction) showed significantly smaller average grain size than the other two samples, reaching an average grain size of 12.58 μm after sintering at 1 390 ℃ for 4 h. Furthermore, after a solution treatment at 1 040 ℃ for 1 h followed by aging at 510 ℃ for 4 h, the yield strength of the V-containing steel is 1 803 MPa with an elongation of 3.02%, which are improved in comparison with the unalloyed base steel. The research demonstrates that V enhances the strength of steel in its aging state while maintaining a high strength in the sintered state, Ti effectively refines grains, and Cu substantially improves elongation. By changing microalloying elements, sintering conditions, and heat treatment processes, the microstructure of maraging steel can be tailored, thereby optimizing its overall performance. The further research could be focused on exploring multi-component microalloying strategies to achieve better performance and promote the application in practical engineering.

Under the background of carbon neutrality, automotive lightweighting has become one of the key paths to reduce carbon emissions. Ultra-low carbon steel is widely used in the automotive industry due to its excellent deep drawing performance, and rare earth elements have shown significant value due to their unique functions. Based on this, by adding different contents of rare earth La to ultra-low carbon steel and using scanning electron microscopy and EBSD technology, the influence of rare earth La on the microstructure and texture transformation of hot rolling, cold rolling and recrystallization of ultra-low carbon steel was studied. And the influence of La on the forming performance was studied in combination with the tensile test. The results show that with the increase of La content, the grain size of hot-rolled steel decreases from 353 μm to 82 μm, and the γ texture weakens. When the La mass fraction is 3.2×10^-5, the recrystallization process is strongly delayed, the recrystallization grain size is refined, and the tensile strength increases from 219 MPa to 251 MPa. When the La mass fraction increases to 1.5×10^-4, the recrystallization process is promoted, and the volume fraction of recrystallized γ texture decreases from 48% to 40%, resulting in a decrease in plastic strain ratio from 3.15 to 2.78.

With the development of advanced nuclear energy systems, high requirements have been placed on core structural materials.High performance 9Cr-ODS steel plates were prepared based on powder metallurgy combined with hot rolling and heat treatment, and their three-dimensional microstructure and mechanical properties were systematically investigated. The results show that the three-dimensional microstructure of the 9Cr-ODS steel exhibits typical rolling characteristics. The rolling direction-transverse direction plane is composed of equiaxed grains, while the transverse direction-normal direction and rolling direction-normal direction planes consist of severely deformed and elongated grains, with an aspect ratio greater than 10.The Cr distribution in the 9Cr-ODS steel is inhomogeneous, and a high density of dislocations as well as dispersed spherical strengthening particles are observed. The mechanical properties of the 9Cr-ODS steel show some inhomogeneity. The difference in properties among standard large-sized tensile samples is small. In contrast, the properties of small plate-shaped samples vary significantly and are closely related to the sampling location. Particularly for the fracture elongation, the maximum difference among these small samples can exceed 30%.Fracture in the 9Cr-ODS steel occurs mainly by intergranular and transgranular modes, and obvious necking is observed during the tensile process. The fracture surface exhibits a laminated fibrous morphology with an inter-laminate spacing of approximately 3-5 μm.

The hot corrosion behavior of GH4720Li alloy in molten NaCl-Na₂SO₄ at 700 ℃ was investigated, in order to clarify its corrosion kinetics and micro-mechanisms, and to provide experimental basis for its application in aero-engine turbine disks. Crucible molten salt hot corrosion tests were conducted, combined with X-ray diffraction, scanning electron microscopy, electron probe microanalysis, and electron backscatter diffraction, to systematically analyze the corrosion products, microstructural evolution, and corrosion kinetics of the alloy under different exposure time (1-200 h). Themass gain of GH4720Li alloy followed a parabolic law, with the corrosion rate gradually increasing over time. A dense Cr₂O₃ layer formed on the surface played a major protective role in the initial stage. After the rupture of the oxide film, sulfur reduced from the molten salt preferentially corroded along grain boundaries and γ′ precipitates to form sulfides, which were subsequently oxidized into a loose oxide layer. The hot corrosion process of GH4720Li alloy follows a sulfidation-oxidation mechanism and can be divided into four stages: oxide film formation and protection, oxidation-sulfidation, accelerated oxidation, and internal sulfidation. Controlling grain size and precipitate content is beneficial to improving the corrosion resistance.

Aiming at the high value-added utilization of steel slag, the influence mechanism of Fe₂O₃ content on the phase composition, microstructure and physicochemical properties of steel slag was systematically studied. Using electric furnace steel slag as the raw material, the slag was treated by the pure reagent addition method. The quenched and temperedsteel slag was subjected to high-temperature remelting and rapid cooling processes to prepare steel slag samples with different Fe₂O₃ contents. Subsequently, a comprehensive phase analysis and physicochemical property determination were carried out on this series of samples. The results show that Fe₂O₃ can promote the formation of spinel phase while inhibiting the formation of Ca₂Fe₂O₅ and Ca₂SiO₄ phases. With the increase of Fe₂O₃ content, the mass fraction of f-CaO in the quenched and temperedsteel slag first decreases and then increases, but it is all below 2.23%; the average Vickers hardness is between 825.87 and 931.38, showing a trend of first increasing and then decreasing. When the mass fraction of Fe₂O₃ is 21.50%, the mass fraction of f-CaO is the lowest, at 1.88%; the maximum average hardness is 931.38HV. Under this condition, the treated steel slag samples exhibit good stability and high hardness characteristics and have the potential to be used as non-metallic abrasives.