15 April 2026, Volume 61 Issue 4

    

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Technical Reviews
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  Research progress on effects of Sn and Sb on magnetic and mechanical properties of non-oriented silicon steel

  WANG Haijun, LÜ Zeyi, PEI Yinghao, XIA Xuelan, QIAO Jialong, QIU Shengtao

  Iron and Steel. 2026, 61(4): 1-15. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250659

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  Non-oriented silicon steel is a critical material for manufacturing drive motor cores in new energy vehicles, and its magnetic properties, mechanical properties directly determine the energy consumption and performance of the drive motors. Studies have shown that the addition of Sn and Sb can effectively enhance the magnetic flux density and reduce the iron loss of non-oriented silicon steel. Meanwhile, experimental results demonstrate that the incorporation of Sn and Sb strengthens the strength, hardness, and certain toughness of non-oriented silicon steel, thereby improving its mechanical properties. In recent years, synergistically optimizing the comprehensive properties of non-oriented silicon steel through microalloying （e.g., adding elements such as Sn and Sb） has emerged as a research hotspot and cutting-edge direction in this field. Based on this, this paper aims to systematically review the action mechanisms and related research progress of Sn and Sb on the microstructure, magnetic properties, and mechanical properties of non-oriented silicon steel. Special focus is placed on analyzing the segregation behavior of Sn and Sb at grain boundaries and their regulatory mechanism on the formation space of textures. When Sn and Sb enter the crystal interior, they induce lattice distortion and generate high strain energy, promoting their segregation to grain boundaries. Simultaneously, due to their strong electronegativity, they tend to acquire free electrons at grain boundaries, forming a stable structure. This paper provides a detailed review of the research progress made by relevant enterprises and research institutions at home and abroad regarding the improvement of magnetic properties of non-oriented silicon steel by Sn and Sb. The segregation of an appropriate amount of Sn and Sb at grain boundaries not only hinders grain boundary migration and refines grain size but also inhibits the nucleation and growth of the unfavorable {111} texture, reduces the surface energy of （100） grains, and promotes the development of the favorable {100} texture. Furthermore, Sn and Sb can suppress the precipitation of fine inclusions （AlN and MnS） in non-oriented silicon steel, increase the precipitate size, and thus improve the magnetic properties.
Raw Material and Ironmaking
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  Analysis and verification of impact of coke structure evolution on blast furnace permeability

  LIU Qihang, CHEN Hui, SONG Peng, WANG Miao, YANG Shuangping, ZHANG Wenda

  Iron and Steel. 2026, 61(4): 16-28. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250591

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  As the sole skeletal support in blast furnaces, the degradation behavior of coke exerts a crucial influence on blast furnace permeability. Three types of industrial cokes were selected as research objects. The evolutionary characteristics of coke microporous structure and the degradation distribution characteristics of particle size were analyzed via scanning electron microscopy-energy dispersive spectrometer （SEM-EDS）, mercury intrusion porosimetry, high-temperature carbon loss-drum test and other experimental methods, combined with porous media theory. The heterogeneity of high-temperature coke degradation was quantified, and its potential correlation with blast furnace permeability was further explored. Finally, the relationship between coke degradation heterogeneity and blast furnace permeability was verified through porosity and pressure difference simulation tests.The results show that after the carbon loss reaction, the pore walls of coke are eroded, some originally closed pores are gradually opened, and the interconnection of micropores facilitates the formation of macropores, leading to a significant increase in the number of pores. This structural change reduces the diffusion resistance of reactive gas into coke pores, resulting in a gradual decrease in the gas concentration gradient and a reduction in degradation heterogeneity. Due to differences in initial pore structure characteristics, the relative concentration gradients of the three cokes during the carbon loss process follow the order of Coke C>Coke B>Coke A. A higher concentration gradient leads to a more concentrated carbon loss reaction on the coke surface, i.e., more severe coke degradation heterogeneity. Thus, Coke C exhibits the strongest degradation heterogeneity, while the carbon loss process of Coke A is more uniform, which is beneficial to blast furnace permeability. This finding is fully consistent with the optimal application performance of Coke A in actual blast furnace production. In addition, the results of pressure difference and permeability simulation tests indicate that there are significant statistical correlations between the permeability index and both the post-reaction coke strength and the degradation heterogeneity index, which further verifies the important influence of coke carbon loss heterogeneity on blast furnace permeability.The research results provide an important theoretical basis for the rational regulation of coke pore structure via coking processes, thereby accurately improving coke quality and ensuring the stable operation of blast furnaces.
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  Influence of adding iron/titanium oxides on the properties and structure of composite coke

  LIU Yunbo, ZHANG Shengfu, ZHANG Xi, CHEN Jingbo, WEI Zhifang, WANG Jianming, BAI Chenguang

  Iron and Steel. 2026, 61(4): 29-40. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250669

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  The development and application of novel low-carbon ironmaking burden materials represent a critical pathway for blast furnaces to achieve carbon reduction and emission abatement. Although highly reactive iron coke can improve gas utilization, it suffers from low thermal strength. The incorporation of TiO₂ in the coking process is demonstrated to enhance the thermal strength of coke. In this study, iron-titanium composite coke was prepared by adding Fe₂O₃ and TiO₂ to coking coal through crucible coke experiments. The influence of adding Fe₂O₃ and TiO₂ on the morphology,shatter strength,carbon microcrystalline structure,and pore structure of the coke were investigated using Raman spectroscopy,N₂ adsorption,and other characterization methods. Furthermore,the mineral phase transformation of iron and titanium oxides during the coking process was calculated and analyzed using FactSage software. The results indicate that,compared with coke produced from raw coal,coke with added Fe₂O₃ is observed to exhibit more morphological cracks,and its shatter strength is reduced by 35 to 85 percent points. Conversely,coke containing added TiO₂ exhibits regular coke morphology,with a shatter strength decreases of only 2 to 15 percent points. Subsequent to the amalgamation of two additives,the morphology of the coke remains intact,and its shatter strength is positioned between that of iron coke and titanium coke. When the total blend ratio reaches 5%,the shatter strength of the iron-titanium composite coke attains 94.65% of that derived from raw coal. The evolution of the microcrystalline structure indicates that the defect structure is increased by Fe₂O₃ at elevated temperatures（850 ℃）,whereas the ordered arrangement of graphite microcrystals is enhanced by TiO₂ at temperatures exceeding 650 ℃. A synergistic enhancement in the ordering degree of the carbon structure throughout the entire coking temperature range is achieved by the composite addition of the two. In terms of pore structure, the development and interconnection of mesopores are facilitated by Fe₂O₃ within the temperature range of 450 ℃ to 650 ℃,thereby increasing both specific surface area and pore volume. Conversely, pore collapse during the high-temperature stage（≥850 ℃）is prevented by TiO₂ due to the thermal stability of the rutile phase. The evolution of mineral phases indicates that a volume "expansion-contraction" phenomenon is induced by the reduction of Fe₂O₃（Fe³⁺→Fe²⁺→Fe）,which in turn induces defects. Conversely,the low-temperature formation of ilmenite is promoted by TiO₂ through strong binding with FeO,the formation of iron olivine is inhibited,and lattice stress is mitigated. This study provides significant theoretical support for the preparation and performance optimization of high-quality iron-titanium composite coke.
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  Enhanced fluidized bed hydrogen reduction of ilmenite through granulation modification with Fe₂O₃

  DU Zhan, CHEN Bing

  Iron and Steel. 2026, 61(4): 41-49. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250607

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  To develop efficient direct reduction technology for ilmenite, this study innovatively proposed the use of Fe₂O₃ granulation modification to enhance its fluidized bed hydrogen reduction. Systematic fluidized bed hydrogen reduction experiments were conducted to investigate the mechanism of modification on the reduction behavior of ilmenite. The results demonstrated that Fe₂O₃ granulation modification exhibited a dual enhancement effect, as it can effectively inhibited defluidization at high temperatures and significantly increasing the reduction rate. The modified ilmenite particles could be stably fluidized in hydrogen at 940 ℃ for over 60 minutes, and the metallization degree of reduction product is increased from 12% to 97%. Mechanistic studies indicated that, at the level of physical effects, the granulation modification destroyed the dense iron shell newly formed on the surface of raw ilmenite particles. Simultaneously, the introduced non-sticky component materials acted as physical barriers, effectively reducing particle surface stickiness and thereby preventing the occurrence of defluidization. At the level of chemical effects, the granulation modification, through raw material refinement, completely eliminated the "chemical barrier effect" formed by the Fe_xMg_1-xO·TiO₂ solid solution. Kinetic studies revealed that the reduction process of the granulation-modified samples followed the 2D nucleation and grain growth model. The added Fe₂O₃ is converted into fine iron grains in the initial reduction stage. These grains acted as nucleation sites, greatly promoting the precipitation of iron from FeO·TiO₂ and significantly accelerating the nucleation rate. Calculation of the apparent activation energy for the reduction reaction showed that the activation energy for the Fe₂O₃-modified samples （80.47 kJ/mol） is lower than that of the unmodified samples （94.80 kJ/mol）, confirming its catalytic promoting effect on the reduction. Evaluation of the applicability to ilmenite from different sources verified the universal applicability of the Fe₂O₃ granulation modification method for enhancing reduction. This study provided a new approach to solving the challenges of defluidization and reduction stagnation in the fluidized bed hydrogen reduction of ilmenite and laid a theoretical foundation for the efficient utilization of ilmenite.
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  Effect of coke oven gas injection on pulverized coal combustion and metallurgical process in a blast furnace

  XU Runsheng, ZHOU Hanmo, HUANG Xu, ZHAO Yunjian, YE Lian, ZHANG Jianliang, DUAN Sijia

  Iron and Steel. 2026, 61(4): 50-60. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250597

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  Hydrogen-rich gas injection into the blast furnace （BF） is a key technological pathway for achieving low-carbon metallurgy. However, existing mathematical models often simplify the pulverized coal combustion rate as a constant value, neglecting the competitive combustion effect between the hydrogen-rich gas and pulverized coal during co-injection. This leads to deviations in the evaluation of smelting indices and carbon emissions. To accurately assess the impact of coke oven gas （COG） injection on the BF process, this study first determined the pulverized coal combustion rates under different injection volumes via high-temperature combustion simulation experiments. By coupling these experimental data with a hydrogen-rich blast furnace mathematical model, the effects of combustion rate variations on the coke ratio, coke replacement ratio, direct reduction degree, theoretical combustion temperature, and carbon emissions were systematically analyzed. The results indicate that as the COG injection volume increases from 0 to 60 m³/t, the pulverized coal combustion rate decreases from 72.0% to 64.2%. Constrained by the reduced heat release from coal combustion and the endothermic nature of the hydrogen reduction reaction, the coke replacement ratio shows an accelerated downward trend, dropping from 0.45 at 10 m³/t to 0.40 at 60 m³/t. Nevertheless, COG injection effectively improves smelting indices, reducing the direct reduction degree from 0.454 to 0.387 and the coke ratio from 377.5 kg/t to 353.5 kg/t. Regarding the thermal regime, large-scale COG injection causes the theoretical combustion temperature to decrease from 2 207.7 ℃ to 2 085.7 ℃, while the top gas temperature rises from 197.37 ℃ to 213.87 ℃. To maintain stable thermal equilibrium in the hearth and shaft, a coordinated operation window for the oxygen enrichment rate and injection volume was established. Under an injection volume of 60 m³/t, the oxygen enrichment rate must be adjusted to the range of 5.70%-13.19%. Quantitative evaluation of carbon emissions reveals that the indirect reduction effect of hydrogen-rich gas plays a dominant role in carbon reduction, while the impact of competitive combustion is minor. The carbon reduction attributed to the chemical reduction effect of COG is 31.2 kg/t, whereas the increase in carbon emissions caused by competitive combustion is only 0.5 kg/t.
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  Integrated ironmaking technology based on information fusion and spatial reconstruction

  SUN Xiaodong, ZHOU Ke, XIE Hao, XIAO Huiheng, HE Haixi, ZHAO Kuan, PAN Dong, JIANG Zhaohui

  Iron and Steel. 2026, 61(4): 61-71. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250594

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  As the core of the steel manufacturing process, the intelligent transformation of ironmaking is critical for achieving national "dual carbon" goals and advancing high-quality industrial development. An integrated ironmaking technology based on information fusion and spatial reconstruction was proposed to address the persistent challenges in conventional production, including pronounced data silos, operational inefficiencies, safety concerns, rigid management structures, high energy consumption and significant emissions. Regarding information integration, an industrial big data platform encompassing the entire ironmaking process was established, and a closed-loop collaborative control system integrating "key index prediction, anomaly condition warning, and operational collaborative control" was created, thus facilitating the shift from local optimization at individual processes to global optimization across the entire production line. In spatial reconfiguration, large-scale centralized control technology for cross-process and cross-system applications, as well as distributed control and linkage mechanisms based on multi-modal data fusion were developed. An ironmaking integrated centralized control center was built, achieving a leapfrog transformation from "decentralized control" to "centralized management and control". For organizational innovation, a process-reengineering-based organizational reform method was proposed, which drove the transformation of the organizational structure from "hierarchical and fragmented mode" to "flat and integrated one", ultimately achieving significant improvements in management efficiency and optimized organizational configurations. The technology is successfully applied at Guangdong Zhongnan Iron and Steel Co., Ltd., constructing the world's first long-distance and large-scale ironmaking centralized control center. The results show that the coordinated cross-process management and control across a 5-kilometer range is enabled, 42 control rooms are consolidated into a single integrated center, 82 operating positions are streamlined down to 50, and personnel operational efficiency is significantly improved.
Steelmaking
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  A new approach to reducing slag entrapment in continuous casting mold flux for ultra-low carbon steel

  HU Zhiyong, JIN Yuting, WU Xiaoxiao, WANG Qiangqiang, HE Shengping

  Iron and Steel. 2026, 61(4): 72-81. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250605

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  The entrapment of mold powder by meniscus hook-shaped solidified shells and the tearing of molten steel at the steel level in the mold are key factors inducing slag entrainment defects in ultra-low carbon continuous casting and restricting slab quality. Previous studies have mainly focused on the mechanism of steel tearings, with insufficient attention paid to slag entrainment caused by hook-shaped shells. To fill this research gap, an optimization strategy was proposed to suppress hook growth and reduce slag entrainment by increasing the break temperature of mold flux to reduce heat transfer through the slag film. Based on conventional high-viscosity slag systems for ultra-low carbon steel, using basicity, Na₂O, F, and Al₂O₃ as single variables, combined with principal component analysis and multiple regression fitting, a target mold flux with both high viscosity （0.40 Pa·s） and high break temperature （1 216 ℃） was obtained through parameter optimization. The results show that the surface tension of the target mold flux increased to 430 mN/m, while the steady-state heat flux density decreases to 1.53 mW/m². Among these factors, cuspidine crystals precipitated in the solid slag film play a critical role in suppressing heat transfer, while the liquid slag film maintains a glassy structure to ensure adequate lubrication. Through the synergistic effects of high surface tension and low heat transfer characteristics, the target mold flux not only enhances resistance to molten steel tearing but also effectively reduces the tendency of hook-shaped solidified shells to entrap liquid slag by inhibiting the growth of the initial meniscus shell. Industrial trials further validated the effectiveness of the target mold flux. After its application, the depth of the hook structure significantly decreases, and the slag defect rate in cold-rolled coils is further reduced to 0.53%. The research results provide a feasible new way for the design of slag entrapment prevention in ultra-low carbon steel continuous casting mold flux.
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  Effect of droplet characteristics on heat transfer behavior of air-mist cooling in secondary cooling zone

  WU Weili, CHENG Changgui, LI Yang, HUANG Xingyu, SUN Tianxu, GUAN Min, YAN Min

  Iron and Steel. 2026, 61(4): 82-94. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250618

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  The cooling efficiency of high-temperature slab in the secondary cooling zone of continuous casters depends on whether the droplets can penetrate the vapor and liquid films. This process is governed by the droplet dynamic parameters （velocity, size, and quantity）, which is closely related to the nozzle structure and process parameters. The internal-mixing air-mist nozzle of secondary cooling zone was taken as the research object, the cold state and hot state experiments were combined, the spray characteristics and the heat transfer mechanism on the slab surface under different process parameters were investigated, and the influence mechanism of droplet characteristics on the heat flux of slab surface was revealed. The results show that during the air-mist cooling process, as the temperature of slab surface decreases from 1 000 ℃ to 900 ℃, the surface heat flux exhibits a gradual increase, with the rate of increase diminishing progressively. Under different operating conditions, the local water flow density, droplet vertical velocity component and Sauter mean diameter on the slab surface exhibit a lateral decrease from the center toward the edges, resulting in a significantly enhanced heat transfer intensity at the center than at the transverse position 100 mm away from the center. An increase in spray height from 120 mm to 160 mm leads to a notable reduction in local water flow density, droplet vertical velocity component, and Sauter mean diameter at the center of slab surface. Consequently, the average cooling rate decreases from 22.3 ℃/s to 9.2 ℃/s, accompanied by a decline in the increase rate of average heat flux from 3 251.9 W/（m²·℃） to 2 175.0 W/（m²·℃）. As the air pressure increases from 0.2 MPa to 0.4 MPa, the main reasons contributing to the rise in the heat flux at the center of slab surface are the increase in the vertical velocity component of droplets and the decrease in the Sauter mean diameter of droplets. However, as the water pressure increases from 0.4 MPa to 0.6 MPa, the predominant factor contributing to the rise in heat flux is the increase in local water flow density. The average heat flux at the center of slab surface exhibits a positive correlation with the local water flow density and droplet velocity, while demonstrating a negative correlation with droplet size. The findings of this study provide experimental evidence and theoretical basis for optimizing spray parameters in the secondary cooling zone of continuous casters, establishing a regulation mechanism of cooling intensity on the slab surface for high-speed casting, and enhancing slab quality.
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  Crack analysis and submerged entry nozzle optimization for 165 mm × 365 mm rectangular billet

  LI Hongkang, LÜ Ming, GUO Hongmin, CHANG Zhuo, FENG Chao, ZHANG Zhaohui

  Iron and Steel. 2026, 61(4): 95-106. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250631

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  The thickness and uniformity of the solidified shell in the mold are essential prerequisites for defect-free billet production. While the influence of submerged entry nozzle structure on flow behavior of molten steel is a key factor causing fluctuations in the solidifying shell. In response to surface longitudinal cracks and breakout incidents observed during the continuous casting of 165 mm × 365 mm rectangular billets, the effects of mold flux lubrication performance, solidified shell morphology, and equipment operating conditions on crack formation were systematically analyzed. The results indicate that surface longitudinal cracks originate from remelting and thinning of the inner-arc shell. Under conditions of inadequate mold flux lubrication and oscillation frame misalignment, these defects are readily initiated and may develop into breakout accidents under severe conditions. On this basis, a finite element numerical simulation was conducted to investigate the effects of straight-through nozzle and bilateral-hole nozzle on the molten steel flow, heat transfer, and solidification behavior in the mold of a small-section rectangular billet. The results show that, for the straight-through nozzle, a concentrated high-temperature core region forms beneath the nozzle, which is unfavorable for superheat dissipation and uniform heat transfer. The impingement of high-temperature molten steel leads to remelting of the inner-arc shell, resulting in a minimum shell thickness of 8.79 mm at the mold exit and an impact depth reaching 0.82 m. Meanwhile, the overall temperature in the upper region of the mold remains relatively low, which is detrimental to mold flux lubrication and inclusion flotation. When the bilateral-hole nozzle is adopted, the high-temperature region within the mold shifts upward and the molten steel impact depth is significantly reduced, leading to a marked improvement in the uniformity of the inner-arc shell thickness. However, the side-port jets may cause erosion and thinning of the narrow-face solidified shell. When the port angle of the bilateral-hole nozzle is set at 25°, the minimum shell thickness at the mold exit exceeds 10 mm, with an average shell thickness of 15.17 mm. Under this condition, the meniscus fluctuation height is 2.53 mm and the average meniscus temperature reaches 1 521 ℃, effectively improving the temperature field distribution and promoting uniform shell growth within the mold.
Metal Forming
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  Effect of hot rolling deformation on microstructure and properties of 15-5PH stainless steel with different Ni contents

  YAN Chunyu, TIAN Shuai, CHU Weihan, HU Jiarui, SUN Xiaobao, ZHAO Wenyu, LIU Zhenbao

  Iron and Steel. 2026, 61(4): 107-118. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250622

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  To clarify the grain evolution behavior and aging response characteristics of 15-5PH stainless steels with different Ni contents during hot rolling, to reveal the effects of hot-rolling process parameters and alloy composition on the microstructural evolution and mechanical properties, and to provide a theoretical basis for the optimization of hot-rolling processing and compositional design of 15-5PH stainless steel plates. At a rolling speed of 0.4 m/s, the effects of two hot rolling temperatures （1 080 ℃ and 1 030 ℃） and four deformation levels （70%, 44.4%, 65%, and 28.5%） on grain evolution and aging properties of 15-5PH stainless steels with different nickel contents were systematically investigated. The results indicate that during the first hot rolling at 1 080 ℃, the plate microstructure exhibits a clear tendency toward inheritance and coarsening after heavy deformation of 70% and 65%, with no recrystallization occurring. When the once-rolled plate undergoes secondary rolling at 1 030 ℃, the prior deformation history plays a decisive role in grain evolution. Secondary rolling of the plate pre-deformed by 70% （with a second-pass deformation of 44.4% and a cumulative deformation of 83.3%） fails to refine the grains. In contrast, secondary rolling of the plate pre-deformed by 65% （with a second-pass deformation of 28.5% and a cumulative deformation of 75%） induces complete dynamic recrystallization, resulting in an equiaxed fine-grained structure, which represents the optimal hot rolling process. The hot rolling grain evolution trends are consistent across the three experimental steels, indicating that within the scope of this study, variations in nickel content under the same process have no significant impact on the grain evolution behavior. As the aging temperature increases, the strength of the three experimental steels decreases and the plasticity increases. The higher nickel content, the lower the strength. The primary reason is that nickel in the steel promotes the formation of reversed austenite, and the increase in austenite volume fraction reduces the strength of the steel. The research is not limited to the final deformation, but reveals its decisive role in grain evolution by analyzing the complete process path of multi-pass hot rolling. The findings are expected to provide direct experimental evidence for the independent optimization of composition design and hot rolling processes, offering important theoretical guidance for the precise engineering production of 15-5PH stainless steel plates.
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  Identification and warning of self-excited vibration in tandem cold rolling based on mechanism-data dual-driven

  CAO Lei, LI Xu, BAI Bing, GENG Mingshan

  Iron and Steel. 2026, 61(4): 119-133. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250644

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  The rolling mill vibration seriously affects the quality of thin-gauge high-strength steel products in the high-speed tandem cold rolling process. Regarding the problem, a vibration energy prediction method that integrated mechanism and data-driven approaches was proposed in this paper. It aims to break through the key bottlenecks that restrict the stability of production and the improvement of efficiency. Traditional analytical methods based on steady-state assumptions struggle to accurately describe dynamic roll gap characteristics under vibration conditions, while purely data-driven models lack physical mechanism interpretation. Therefore, a parabolic dynamic velocity field considering work roll vertical vibration was constructed firstly. An analytical model encompassing internal plastic deformation, friction, shear, and tension powers was derived based on the upper-bound approach. It can reveal the vibration mechanism from an energy perspective. Subsequently, 12 critical parameters, such as roll gap change rate, rolling force and back tension stress, were selected using the maximal information coefficient. Based on this, a bidirectional long short-term memory （BiLSTM） network integrating the attention mechanism was established to extract deep temporal features. Learning rate decay and the Dropout strategy had also been employed to optimize the training process. It demonstrates that the proposed Att-BiLSTM model performs excellently in both prediction accuracy （correlation coefficient R=0.968, determination coefficient R²=0.925） and computational efficiency （prediction time of 3.5 ms）. The model has excellent engineering practicability and can provide early warning for self-excited vibrations. Meanwhile, the feature importance analysis further clarifies that the roll gap change rate and the rolling force are the key influencing factors, and reveals that the recent historical information has a stronger contribution to vibration identification. Through the effective integration of mechanism and data, this work not only achieves high-precision and high-efficiency prediction of the rolling mill vibration energy, but also provides a new approach for vibration mechanism explanation and process optimization. It has significant value for promoting the high-quality production of strips.
Materials
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  Progress of press hardening steels： strengthening and toughening, oxidation resistance and hydrogen embrittlement resistance

  QI Guangjie, YU Yishuang, CAI Xiaorong, JIN Xuejun

  Iron and Steel. 2026, 61(4): 134-149. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250582

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  With the increasing demand for lightweighting and safety in the automotive industry, press hardening steels have been widely used in key structural components of automobiles due to their excellent mechanical properties and formability. However, press hardening steels still face three key challenges at present. They are the trade-off between strength and toughness, surface oxidation after forming, and the hydrogen embrittlement. These challenges restrict the further promotion and application of press hardening steels. To address these challenges, numerous researchers have delved deeply into two major technical paths in recent years, alloy composition design and process optimization. In terms of strengthening and toughening, new techniques such as press hardening-quenching and partitioning steels and medium manganese steels have achieved a product of strength and ductility exceeding 20 GPa·% by regulating the content and distribution of retained austenite, and significantly improved the toughness at the same time. Regarding oxidation resistance, in addition to conventional surface coatings, Cr-Si alloyed uncoated press hardening steels have made a breakthrough. Meanwhile, new processes such as rapid heating and pre-oxidation have also been proven to effectively alleviate surface oxidation during the forming process. Concerning hydrogen embrittlement resistance, researchers have dedicated to clarifying the interaction mechanism between hydrogen and coatings, grain boundaries, precipitates, and retained austenite, etc. By adding microalloying elements such as Nb and Ti, the microstructure is refined and hydrogen traps are induced to reduce the content of diffusible hydrogen. This paper systematically reviews the recent progress in strengthening and toughening, oxidation resistance and hydrogen embrittlement resistance of press hardening steels, focusing on alloy composition design and process optimization. With the development of artificial intelligence and the increasing demand for heavy-gauge press hardening steels, press hardening steels will continue to advance in the direction of multi-performance collaboration as well as intelligent research and development in the future.
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  Effect of Ti on microstructure and mechanical properties of CrNiMo low alloy cast steel

  WANG Fang, GUO Shimeng, CHANG Yunan, FAN Meifeng, ZHU Shiting, CHEN Huiqin, HOU Hua

  Iron and Steel. 2026, 61(4): 150-160. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250696

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  To improve the comprehensive mechanical properties of CrNiMo low alloy cast steel, the effects of micro-alloying element titanium and quenching temperature on its microstructure and performance were investigated. Utilizing various characterization methods such as scanning electron microscopy （SEM）, electron backscatter diffraction （EBSD）, transmission electron microscopy （TEM）, and optical microscopy （OM）, the influence of titanium content and quenching temperature on austenite grain growth behavior was analyzed, and the mechanism by which titanium affects the morphology of tempered sorbite and the final mechanical properties was explored. The results indicate that during quenching at 900-950 ℃, titanium content has no significant effect on the average austenite grain size but noticeably affects the uniformity of grain size distribution. When the quenching temperature exceeds 1 000 ℃, titanium plays a more pronounced role in inhibiting grain coarsening, and higher quenching temperatures lead to larger grain sizes. At quenching temperature of 950 ℃ and titanium mass fraction of 0.035%, the austenite grains are the finest and most uniform, with an average size of 11.13 μm. Mechanistic analysis reveals that at lower quenching temperatures, Ti（C,N） does not fully dissolve, and the quenching temperature dominates grain size evolution. If the titanium content is too low, the number of precipitates is insufficient, while excessive titanium content can lead to titanium atom segregation. Both scenarios weaken the pinning effect on grain boundaries and compromise microstructural uniformity. After tempering at 550 ℃, the test steel corresponding to the above process parameters shows the best mechanical properties, the tensile strength is 1 134.95 MPa, the yield strength is 1 101.59 MPa, and the impact energy at room temperature is 43.74 J. By regulating the quantity and size of Ti（C,N） precipitates, titanium enhances strength of steel while maintaining good toughness, achieving a comprehensive optimization of strength-toughness balance.
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  Local adaptive noise reduction method for the impact fracture surface of 9Ni steel based on RKMD algorithm

  XU Xiaoya, ZANG Ximin, ZHAO Heming, YU Hao, DU Lin, LI Zhipan, PANG Qihang

  Iron and Steel. 2026, 61(4): 161-172. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250592

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  9Ni steel serves as a critical material for liquefied natural gas （LNG）storage and transportation equipment. The accurate determination of its fracture modes heavily relies on high-quality scanning electron microscope （SEM） fracture images. However, image noise introduced during testing can obscure key microscopic morphological features. This not only significantly increases the difficulty and error rate of manual identification but also reduces the effectiveness of traditional image processing methods. Therefore, developing an adaptive denoising algorithm for fracture images that can effectively handle high noise interference is key prerequisite for providing high-quality data foundation for intelligent recognition. To address high-noise fracture images, an improved recursive kernel mean distance（RKMD） adaptive denoising algorithm was proposed. By incorporating wavelet transform through a local adaptive strategy, this algorithm effectively mitigates the excessive smoothing of critical features such as edges and textures during the denoising process of fracture images. By constructing an objective function aimed at minimizing residual kurtosis and integrating multi-scale edge-aware mechanism, the threshold selection strategy was dynamically optimized. This achieves a better balance between noise suppression and the preservation of edge topology in fracture features. Based on a dataset constructed from 3 050 sets of high-resolution fracture images, data-driven intelligent discrimination of fracture modes was achieved. Experimental results show that under extreme conditions with noise standard deviation as high as 30%, the proposed algorithm achieves a peak signal-to-noise ratio of 26.69 dB and a structural similarity index of 0.768 2, demonstrating significantly improves performance compared to traditional wavelet threshold denoising methods. The proposed denoising algorithm provides a clear and reliable image data foundation for subsequent intelligent recognition of fracture morphology. It notably enhances the robustness and accuracy of the fracture performance analysis process for 9Ni steel and also supplies high-quality standardized training data for subsequent deep learning models.
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  Influence of tempering temperature on microstructural evolution and mechanical properties of 1 000 MPa hydropower steel

  XIAO Guizhi, MENG Zhaolin, YANG Jixue, LI Dongyang, AN Ru, MA Jinlei, WANG Yuexiang

  Iron and Steel. 2026, 61(4): 173-184. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250663

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  With the development of hydropower engineering toward high-altitude and high-stress environments, there is an increasing demand for structural steels possessing gigapascal-level strength and excellent low-temperature toughness. Tempering, as key heat treatment process, plays a vital role in balancing strength and toughness in hydropower steels. Taking 1 000 MPa low alloy steel for hydropower as the research object, the microstructure evolution and corresponding mechanical properties of the steel tempered at 590-680 °C were systematically analyzed by means of scanning electron microscope （SEM）, transmission electron microscope （TEM）, tensile and impact tests. The results indicate that as the tempering temperature increases, the as-quenched lath martensite undergoes recovery and gradually widens, with its lath characteristics continuously weakening. The microstructure ultimately transforms into a stable structure dominated by equiaxed ferrite and spheroidized cementite. Concurrently, the grain orientation distribution tends to become more randomized, the proportion of high-angle grain boundaries increases, and the dislocation density continuously decreases. Correspondingly, the yield strength and tensile strength show a declining trend, while the elongation continuously improves. The impact absorbed energy exhibits a non-monotonic change, which increases first and then decreases, and rises again at 680 ℃. Quantitative analysis of strengthening mechanisms reveals that as the tempering temperature increases, the contributions of grain boundary strengthening, dislocation strengthening, and precipitation strengthening to yield strength all show a continuous decreasing trend. The tested steel achieves optimal comprehensive performance under the 620 ℃ tempering condition, with a yield strength of 947 MPa, tensile strength of 983 MPa, elongation of 16.3%, and impact absorbed energy of 158 J at -60 ℃. The research can provide theoretical support and microstructure control basis for the optimization of heat treatment process of high performance hydropower steel, and has certain guiding significance for the development and engineering application of high strength and toughness hydropower steel.
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  Evolution law of texture in grain-oriented electrical steel ultra-thin strips

  LI Yiwei, WU Zhongwang, LIU Baozhi, ZHANG Huimin, REN Huiping, DONG Rui

  Iron and Steel. 2026, 61(4): 185-196. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250650

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  Grain-oriented silicon steel ultra-thin strip shows broad application prospects in high-frequency power electronic devices due to its excellent magnetic properties. Its texture evolution directly affects the magnetic properties of the final product, and the annealing temperature is a key process parameter for controlling texture and magnetic performance. To investigate the texture evolution during the preparation of grain-oriented silicon steel ultra-thin strip and the influence of annealing temperature on microstructure, texture, and magnetic properties, a commercial substrate- glassless grain-oriented electrical steel sheet with thickness of 0.27 mm was used as raw material. An ultra-thin strip with thickness of 0.08 mm was prepared via single cold-rolling method. The specific process involved two-pass cold rolling, first pass reduction rate 63% and second pass 20%, followed by high-temperature annealing of the cold-rolled ultra-thin strip at different temperatures ranging from 800 to 940 ℃. The research primarily employed characterization techniques such as electron backscatter diffraction（EBSD） micro-texture analysis and X-ray diffraction （XRD） to systematically analyze the evolution of microstructure and texture during the cold rolling and annealing processes of the grain-oriented silicon steel ultra-thin strip. Experimental results indicate that the initial sample is dominated by Goss texture. After the two-pass cold rolling, the Goss orientation significantly transformes into {111}〈112〉 orientation, and this transformation becomes more complete with increasing reduction rate and strip thinning. Subsequently, after high-temperature annealing at different temperatures, the {111}〈112〉 orientation texture transformes back into Goss{110}〈001〉. As the annealing temperature increases, grain size gradually grows, and both the proportion of Goss texture and the magnetic properties show an upward trend. Under higher annealing temperatures, the comprehensive magnetic properties of the ultra-thin grain-oriented silicon steel are better. When the annealing temperature reaches 940 ℃, the magnetic induction B₈₀₀ reaches 1.725 T, and the iron loss P_1.5/400 is 15.76 W/kg, achieving the best comprehensive magnetic performance under the experimental conditions.
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  Effect of Cr content on microstructure and properties of Ni-Co ultra-high strength hull steel

  WANG Long, LI Jian, PAN Yingjun, LUO Xiaobing, CHAI Feng, ZHOU Shengxuan, FAN Wei, YAN Wenbing

  Iron and Steel. 2026, 61(4): 197-210. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250647

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  An appropriate Cr content can enable Ni-Co based ultra-high strength hull steel to achieve a good strength-toughness combination, but its strengthening and toughening mechanisms have not yet been fully elucidated. This study investigated the effects of Cr content on the microstructure,secondary phase precipitation behavior,and mechanical properties of Ni-Co based ultra-high strength hull steel using techniques including scanning electron microscope（SEM）,X-ray diffraction（XRD）,physical-chemical phase analysis,and transmission electron microscope（TEM）,combined with room-temperature tensile and low-temperature impact tests. Microstructural analysis indicated that the microstructure of the test steel consists of tempered martensite and a small amount of reversed austenite. As the Cr content increased,the martensite start temperature（M_s） of the steel decreased,austenite stability improved, and its volume fraction increased. Phase analysis and TEM results reveals that the main precipitates in the Ni-Co steel are M₂C phases,and the Cr content has a significant impact on the size of the secondary phases. At 2%Cr,the low lattice mismatch between the M₂C phase and the matrix promotes the precipitation of a large number of M₂C phases smaller than 5 nm. At 3%Cr,numerous M₂C phases larger than 200 nm are observed,indicating significant coarsening. Mechanical test results demonstrate that the yield strengths of the 1Cr,2Cr,and 3Cr steels are 1 317,1 258, and 1 137 MPa,respectively. The addition of Cr reduces the solid solubility of C in the matrix,promoting the precipitation of nano-sized M₂C phases. With increasing Cr content,the decrease in the solid solution strengthening increment exceeds the increase in the precipitation strengthening increment,resulting in a gradual reduction in yield strength. The impact energies at -84 ℃ for the 1Cr,2Cr,and 3Cr steels are 6,42,and 49 J,respectively. Cr improves the low-temperature toughness of the Ni-Co steel primarily due to the increased reversed austenite content,which enhances crack blunting,and also because Cr promotes the precipitation of coherent nano-sized M₂C phases with the matrix, which reduces strain accumulation and stress concentration, thereby effectively suppressing crack initiation. The 2Cr steel,with its abundant nano-sized M₂C phases and a certain amount of austenite,exhibits a good combination of strength and toughness.
Environmental Protection and Energy
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  Research status of resource utilization of steel slag and iron separation from RO phase

  LI Pengzhen, LI Chenxiao, YUAN Bo, WANG Yan, YAN Hongyan

  Iron and Steel. 2026, 61(4): 211-220. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250665

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  The progressive development of the steel industry has led to annually increase in the accumulation of steel slag, not only occupying large tracts of land but posing certain hazards to the ecological environment. It is very important to make the harmless treatment and resource utilization of steel slag. Driven by the principle that lucid waters and lush mountains are invaluable assets, research of the resource recovery of steel slag has emerged as a significant topic within the realm of sustainable development, achieving tangible progress across diverse sectors. Characterization of steel slag by techniques including X-ray diffraction（XRD） and scanning electron microscope（SEM） reveals its high cementitious properties and elevated contents of valuable metallic elements such as Fe. Steel slag can not only serve as a high-value-added cementitious material but also facilitate the extraction of valuable metals to achieve its multi-dimensional utilization. However, inherent limitations of steel slag, such as the presence of RO phase, which impairs its cementitious properties and grindability, restrict its large-scale utilization. Furthermore, most iron in steel slag exists in the form of FeO enriched in the RO phase or non-magnetic ferrites, which increases the difficulty of extracting iron. This paper comprehensively reviewed the current status of comprehensive utilization of steel slag in the fields of ceramic materials, functional fillers, and construction materials in recent years domestically and internationally, and analyzed the main factors restricting the application of steel slag in these fields. Based on the practical application, this paper proposes that the utilization of steel slag should evolve towards a multi-dimensional and wide-ranging direction. In addition, by analyzing the characteristics and technical advantages of wet processing technology and pyrometallurgical processing technologies, including oxidation, reduction, and reconstruction methods, for separating iron from the RO phase of steel slag, the bottlenecks encountered by different processes in practical application were introduced, and provided an outlook on the future iron extraction technology from steel slag in response to the existing problems. The result will provide references for the resource utilization of steel slag and iron extraction from the RO phase.
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  Strength optimization of carbon-containing hot-pressing briquettes prepared by stainless steel dust and chromite

  YANG Shuo, LI Yixuan, YANG Yue, LIU Peijun, YAN Ruijun, SONG Wei

  Iron and Steel. 2026, 61(4): 221-232. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250626

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  Stainless steel dust is generated as a secondary solid waste during conventional steelmaking processes. It contains valuable metal components such as iron, chromium, and nickel, and is characterized by fine particle size and complex chemical composition, making it prone to causing environmental pollution. Chromite is recognized as an important and scarce natural resource, containing valuable metal elements including iron and chromium. Traditional smelting processes for chromite are faced with triple challenges of high pollution, high energy consumption, and high cost. In this study, stainless steel dust and chromite ore were utilized as raw materials to prepare carbon-containing hot-pressing briquettes through hot-pressing technology, aiming to provide high-quality feedstock for efficient reduction processes such as the rotary hearth furnace and achieve effective recovery of metal components including iron, chromium, and nickel. This approach was designed not only to enhance the smelting efficiency of chromite and reduce dependence on the import of primary ores, but also to mitigate environmental threats caused by solid waste accumulation, thereby aligning with the requirements of solid waste resource utilization and green metallurgy. This paper systematically investigated the effects of key process parameters including raw material ratio, hot-pressing briquetting temperature, hot-pressing briquetting holding time, and hot-pressing briquetting pressure on the compressive strength of carbon-containing hot-pressing briquettes made from stainless steel dust and chromite. It also revealed the mechanisms by which these conditions influence the compressive strength of the carbon-containing hot-pressing briquettes. Through experimental optimization, the optimal preparation parameters were determined, providing a feasible technical solution for the resource recovery of stainless steel dust and chromite. The experimental results show that the optimal formulation for preparing carbon-containing hot-pressing briquettes from stainless steel dust and chromite ore is determined as a 60% to 40% ratio between the two, with an external addition of 27.97% coke coal. The optimal processing parameters are identified as a forming temperature of 250 ℃, a forming pressure of 35 MPa, and a holding time of 2 min. Under these conditions, the compressive strength of the carbon-containing hot-pressing briquette reaches 756.7 N, which meets the strength requirement for charging into a rotary hearth furnace. This work provides a theoretical basis and a novel approach for the synergistic utilization of iron-bearing resources.
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  Occurrence characteristics and performance analysis of elements in hot smoldering steel slag with different particle sizes

  LI Duanle, MENG Xiang, WU Xiaohuan, WU Jiawei, LIAO Shucong, WANG Kun

  Iron and Steel. 2026, 61(4): 233-241. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250673

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  After steel plants crush steel slag and separate iron from it, they usually conduct simple screening according to particle size. However, the occurrence characteristics of the main elements in the screened steel slag are unclear, and the impact of screening on steel slag performance is also unclear. This leads to a low utilization rate of steel slag, making it difficult for the downstream building materials industry to utilize it. To address this problem, this study took hot smoldering steel slag as the research object. Steel slag was classified by particle size, the occurrence characteristics of elements such as calcium, magnesium, and iron were analyzed, and the basic properties of steel slag were systematically evaluated. This work is intended to assist in optimizing the steel slag pretreatment process, and establish the performance evaluation method, quality control indicators, and application scheme for steel slag. The results show that there is a strong correlation between steel slag activity and chemical composition. Magnesium, aluminum, and silicon in steel slag are mainly enriched in fine particles （0-5 mm）, while calcium and iron are concentrated in coarser particles （>5 mm）. The early-age activity of steel slag powder is related to the high-alkalinity substances MgO and Al₂O₃ in the system,and the long-term strength development mainly depends on cementitious active minerals such as C₃S, C₂S, and C₂F in steel slag particles, which has a linear correlation with the alkalinity coefficient. The hydration activity, particle effect of steel slag, and its inhibition on cement hydration jointly determine the microstructure of the hardened paste, which in turn affects its macro strength. When the specific surface area is 420-470 m²/kg, the activity of hot smoldering steel slag is optimally exerted. The expansion of hot smoldering steel slag powder is a long-term continuous process. This study proposes a process route for improving steel slag stability, which can reduce cracking problems and soundness hazards caused by the late expansion of f-CaO, f-MgO, and periclase. This research provides a scientific basis and guidance for steel enterprises to effectively manage and realize the resource utilization of steel slag.