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15 February 2026, Volume 61 Issue 2
    

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    Technical Reviews
  • Review on intelligent recognition of blast furnace gas flow distribution through multimodal data fusion
    HE Zhijun, WEN Shanshan, ZHANG Mengke, ZHANG Junhong, ZHAN Wenlong, GAO Lihua
    Iron and Steel. 2026, 61(2): 1-18. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250456
    Abstract ( ) Download PDF ( ) XML Related Articles File   Knowledge map   Save
    The carbon emissions from the steel industry represent one of the most challenging issues in industrial emission reduction, with the blast furnace （BF）-based integrated process serving as a critical component for energy conservation and emission reduction. Under the dual constraints of the "carbon peak" and "carbon neutrality" strategic objectives and the global climate governance framework, the technological innovation of low-carbon BF smelting has become the core driver for green transformation in the steel industry. Gas flow distribution, as a key control variable for achieving low-carbon emissions in the BF, is difficult to measure directly due to the inherent opaque and enclosed nature of the BF interior. Intelligent gas flow distribution recognition technology enables high-precision quantitative control of gas flow patterns within the BF, which holds strategic significance for achieving carbon reduction targets in BF operations. Based on an investigation of the formation mechanisms, control factors, and quantitative standards of BF gas flow, this paper systematically reviews the cutting-edge advancements in intelligent recognition algorithms, dynamic prediction models, and multimodal fusion modeling techniques for gas flow distribution. Furthermore, it explores the pathways and trends of intelligent control by integrating practical BF regulation strategies （including top and bottom adjustments）. Current intelligent recognition technologies for BF gas flow distribution have made significant progress at multiple levels, including technological development, algorithm innovation, model construction, and practical implementation. These advancements provide solid theoretical foundations and practical guidance for steel enterprises to achieve precise identification and optimized control of BF gas flow, thereby facilitating the efficient and low-carbon development of BF ironmaking. In order to further promote the progress of low-carbon ironmaking technology, intelligent recognition of BF gas flow distribution can further promote, the development and application of novel monitoring data, enhanced integration of multiple innovative technologies, correlation analysis of diverse data sources, and deeper convergence between metallurgical principles and operational practices.
  • Research progress on environmental impacts of iron tailings and prevention strategies
    YANG Aimin, BAI Yunjie, LIU Weixing, WU Mingyu, LÜ Jian
    Iron and Steel. 2026, 61(2): 19-32. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250492
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    The large-scale stockpiling and improper disposal of iron tailings have become a key issue restricting the sustainable development of the global mining industry. Their long-term open-air storage not only occupies a large amount of land resources, but also leads to the diffusion of heavy metal elements into the environment through leaching, wind erosion and other pathways, causing cross-media and cross-regional complex pollution and triggering a series of severe ecological problems such as water eutrophication, soil degradation and loss of biodiversity, posing multi-level and multi-scale environmental risks to ecosystem health and human living environment.Typical iron tailings ponds in many parts of the world are taken as the research object and the pollution characteristics and environmental behavior of iron tailings are systematically analyzed. Firstly, it comprehensively reviews the pollution mechanisms of iron tailings on surrounding water bodies, atmosphere, soil and ecosystems, revealing the migration and transformation laws of heavy metals and their ecotoxicological effects. On this basis, the research progress of current iron tailings pollution prevention and ecological restoration strategies are deeply explored, mainly including the following aspects. In terms of source control, it achieves the reduction of pollutant generation and resource recycling by optimizing the beneficiation process and developing green mining technologies. In terms of resource utilization, it focuses on the high-value utilization of iron tailings in the fields of building materials, ceramic preparation, and soil conditioners. In terms of end-of-pipe remediation, the system summarizes a physico-chemical-biological combined restoration technology, including substrate improvement-vegetation reconstruction-microbial synergy as a set of human-assisted ecological restoration measures. Based on the systematic review of pollution mechanism and prevention strategies of iron tailings, it proposes innovative concepts such as intelligent responsive restoration materials and integrated system of graded utilization and restoration, providing technical routes with both scientific value and application potential for promoting mine environmental management and iron tailings pollution control.
  • Research progress on formation mechanism of reversed austenite in maraging steels and its influence on properties
    GAO Qiuzhi, LU Yuhan, MA Qingshuang, PEI Chenghao, YAN Han, LI Huijun, BAI Jing
    Iron and Steel. 2026, 61(2): 33-55. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250578
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    Traditional maraging steels are widely used in aerospace, high-end equipment and other fields due to their excellent strength and processability. However, traditional maraging steels suffer from insufficient plasticity and toughness due to the unfavorable morphology and distribution of internal precipitates. To address this limitation, formation mechanism, regulation paths of reversed austenite in maraging steels and its influence laws on material properties are reviewed systematically. Research shows that key alloying elements such as Ni, Co, Mo, and Ti significantly affect the nucleation and stability of reversed austenite through segregation and enrichment, promotion of precipitate formation, and other ways. Processes including solution-aging, additive manufacturing, and rolling can achieve precise regulation of volume fraction and morphology of reversed austenite by controlling temperature, stress, and element diffusion behavior. The multiphase structure formed by reversed austenite and martensitic matrix can realize the synergistic optimization of strength and toughness through the transformation-induced plasticity （TRIP） effect, and its volume fraction and distribution state show a clear quantitative correlation with the tensile strength, hardness, and plasticity of the material. By integrating thermodynamic and kinetic analyses, a complete correlation system of "alloying elements-precipitates-processes-reversed austenite-properties" is established, providing theoretical support for the composition design and process optimization of maraging steels. Meanwhile, it prospects the application potential in the fields of additive manufacturing of complex components, development of low-cost alloys, and materials serving in extreme environments, laying a foundation for the research and development as well as engineering application of high-performance maraging steels.
    • Raw Material and Ironmaking
  • Effect of key process parameters on properties and graphitization degree of iron coke
    ZHANG Shuhui, ZHANG Jingyi, WU Xiaozhang, LIU Ran, LAN Chenchen, WU Shuoxuan
    Iron and Steel. 2026, 61(2): 56-69. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250431
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    The development of raw materials suitable to be used in hydrogen-rich blast furnace is a key link to promoting industrialization of hydrogen-rich blast furnace smelting technology. Compared with ordinary coke, iron coke with high reactivity can reduce the temperature in the thermal reserve zone, promote the development of indirect reduction, and reduce CO2 emissions of the blast furnace. In particular, iron coke used in hydrogen-rich blast furnace can accelerate metallic iron carburization and play a protective role in coke. Based on this, the preparation of iron coke was studied under laboratory conditions.The effects of key parameters, including the proportion of iron concentrate powder, carbonization temperature and time, on the properties and graphitization degree of iron coke were explored in order to provide theoretical support for the development of low-carbon attribute iron coke. The results indicate that the compressive strength of iron coke increases and then decreases with increasing the proportion of iron concentrate powder. Correspondingly, the iron coke reactivity（ICRI） increases while the iron coke post-reaction strength （ICSR） decreases. The compressive strength of iron coke are more than 3 000 N with iron concentrates in 7%-10%, while ICSR are lower than 50% with iron concentrates beyond 7%. The compressive strength of iron coke rises when the carbonization temperature is increased in 900-1 100 ℃,and descends with continually increasing the temperature to 1 200 ℃. The ICRI ascents and ICSR declines with the increase of carbonization temperature in 900-1 200 ℃.The compressive strength is more than 3 000 N as the temperature exceeds 1 000 ℃.The compressive strength, ICRI and ICSR at 1 000 ℃ are 3 125 N, 33.89% and 50.13% respectively, 3 450 N,34.15%,48.89% at 1 100 ℃. The compressive strength first increases significantly and then decreases slightly with extending the carbonization time within 1.0-2.5 h, ICRI first decreases and then increases slightly with the increase of carbonization time. Taking into account the compressive strength and high temperature metallurgical properties of iron coke comprehensively, the appropriate proportion of iron concentrate for preparing iron coke is 7%, the carbonization temperature is 1 000 ℃, and the carbonization time is 2.0 h. The three factors above affect the disordered structure and graphitization degree of iron coke. When the proportion of iron concentrate powder increases from 0 to 15%, the graphitization degree decreases from 53.05% to 43.18% and the ratio of characteristic peak area increases from 3.19 to 4.04. The increase of both the carbonization temperature and time promotes the graphitization process of iron coke. The compressive strength and high-temperature metallurgical properties of iron coke are synergistically affected by many factors such as the microstructure of iron coke, porosity, metallic iron content and graphitization degree.
  • Effect of pellet reduction swelling on burden movement in shaft furnace by DEM simulation
    ZHONG Yu, ZHENG Jun, LUO Dongcai, YOU Yang, YANG Lin, NI Jun, XU Jian, LÜ Xuewei
    Iron and Steel. 2026, 61(2): 70-77. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250422
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    Compared with the traditional blast furnace, the direct reduction shaft furnace boasts distinct advantages such as a short process flow, low energy consumption, and low carbon emissions, thus showing broad prospects against the background of the "dual carbon" goals. In this study, a scaled-down simulation model with a ratio of 1：5 was established based on a domestically developed hydrogen-based shaft furnace independently designed by an enterprise. Key input parameters like particle flow velocity in the model were determined in accordance with the Froude number, aiming to investigate the influence of the reduction swelling behavior of pellet ores inside the gas-based shaft furnace on particle flow. This research is intended to provide a theoretical basis for optimizing shaft furnace operation, suppressing abnormal swelling, and improving reduction efficiency. By analyzing the changes in particle flow pattern, velocity distribution, contact force chain, and void fraction distribution, the influence mechanism of pellet reduction swelling on the particle movement behavior inside the furnace was revealed. The results indicate that the reduction swelling of pellets does not alter the overall "V" shape flow pattern, but significantly enhances the aggregation effect of particles in the central region, and this enhancement becomes more pronounced with the increase in swelling rate. Under the condition of similar flow velocities, the particle movement exhibits a distinct vertical stratification characteristic, with the flow velocity in the bottom cone region showing a particularly prominent increase. Contact force analysis demonstrates that the stress distribution inside the furnace is extremely uneven under the pellet swelling condition, and high stress concentration occurs in the conical region, which is likely to aggravate equipment wear. The void fraction decreases along the height direction of the bed; under the working conditions where the pellet swelling rates are 6% and 12%, the average voidage at the bottom decrease to 35% and 37%, respectively, which may affect the gas flow resistance and the uniformity of reducing gas distribution. This study clarifies the key influence of pellet reduction swelling on the movement characteristics of pellets and provides guidance for the process optimization and design of shaft furnaces.
  • Developing composite binders and optimizing fabrication process for cold-bonded pellets
    CHEN Nengge, ZHOU Jianghong, LIU Wensheng, WANG Hui, LONG Hongming, WANG Yifan
    Iron and Steel. 2026, 61(2): 78-88. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250441
    Abstract ( ) Download PDF ( ) XML Related Articles File   Knowledge map   Save
    With the ongoing advancement of low-carbon transition in the iron and steel industry, the development of novel green iron-containing burden materials has become an important strategy for energy conservation and carbon emission reduction in ironmaking processes. Cold-bonded pellets have attracted considerable interest owing to their avoidance of high-temperature roasting and low energy consumption. However, their industrial deployment remains limited by insufficient cold strength and high-temperature performance. This study focuses on overcoming the key technical challenge of enhancing the cold strength of cold-bonded pellets, while high-temperature behavior will be examined in future work. Using sinter return fines and iron concentrate as raw materials, this research systematically investigates the influence of molding parameters on the properties of cold-bonded pellets. A composite binder system was developed, primarily consisting of inorganic binder I4 with the addition of organic binder O5 and additives A5 and A6. The synergistic mechanisms among these components were elucidated. The effect of the drying regimen on binder curing and pellet mechanical properties was also studied. Results indicate that under the optimum processing conditions, which include a raw material moisture content of 7%, a molding pressure of 60 MPa, and pellet dimensions of 32 mm×20 mm×15 mm, the cold strength of pellets prepared with 4% inorganic binder I4 reached 1 055 N/P. The introduction of a composite binder system containing O5, A5, and A6 significantly enhanced the strength, raising it to 2 629.5 N/P. Additionally, optimal pellet performance was obtained after drying at 100 ℃ for 3 h. Mechanistic studies show that suitable moisture enhances liquid bridging and improves particle packing. Appropriate molding pressure reduces porosity and promotes particle interlocking. Increased pellet size expands inter-particle contact area and improves binder distribution, leading to enhanced mechanical properties. Cross-linking between organic binder O5 and inorganic binder I4 improves the network structure, while additives A5 and A6 further strengthen the pellets by increasing the reactivity of binder I4. A well-designed drying protocol facilitates uniform binder curing and controlled moisture release, thereby enhancing pellet integrity. Comparisons of softening and melting behavior revealed that the cold-bonded pellets possess a broader softening interval, lower maximum pressure difference, and superior gas permeability compared to acid pellets. This study offers valuable insights for advancing the industrial application of cold-bonded pellet technology and provides a novel technical approach and theoretical foundation for developing high-performance green ironmaking burden materials.
  • Fractional-order heat transfer characteristics and prediction of blast furnace cooling staves
    ZHANG Qunwei, XING Hongwei, LIANG Qiqi, YANG Aimin, LI Jie, HAN Yang
    Iron and Steel. 2026, 61(2): 89-99. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250455
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    To address the problem that traditional integer-order models exhibit prediction deviations due to non-local thermal memory and transient multi-scale coupling characteristics in the heat transfer process of blast furnace cooling staves, the research aims to construct an accurate heat transfer analysis and dynamic prediction model, providing theoretical and methodological support for the intelligent regulation of cooling systems. The research establishes an unsteady heat transfer model based on the Caputo fractional derivative, which is solved using a Grünwald-Letnikov discretization scheme modified by the short-memory effect to characterize the thermal memory properties of refractory materials. A physics-informed neural network （PINN） architecture embedded with fractional-order operators is designed, combined with receding horizon optimization and transfer learning strategies, to achieve efficient inversion of time-varying thermal conductivity, heat source terms, and fractional-order parameters, as well as dynamic prediction of temperature fields. Through molecular dynamics and phase-field multi-scale simulations, the microscopic effects of Al2O3-SiO2 lattices and microcrack networks on heat conduction are analyzed. A health early warning framework for cooling staves is established based on the mapping relationship between fractional-order parameters and microstructures. The results show that the model converges stably; when the optimal fractional-order α=0.8, the global temperature prediction root mean square error （RMSE） reaches 0.99 ℃, which is significantly better than that of the integer-order model, and the temperature field simulation is consistent with actual working conditions. Multi-scale simulations reveal that the power-law relaxation characteristics of Al2O3-SiO2 lattices and the non-local thermal diffusion induced by microcrack networks are consistent with the characteristics of the fractional-order model. The established health early warning framework can realize quantitative classification of risk levels. The research confirms the advantages of the fractional-order-PINN model in characterizing heat transfer in blast furnace cooling staves, providing a high-precision tool for the intelligent operation and maintenance of blast furnace cooling systems, and promoting the interdisciplinary application of fractional-order theory and deep learning in industrial heat transfer fields.
    • Steelmaking
  • Effectiveness evaluation model of oxide metallurgy for non-metallic inclusions in steel
    YUAN Xinghu, WANG Guocheng, CAO Lei, MENG Jinsong
    Iron and Steel. 2026, 61(2): 100-111. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250504
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    Oxide metallurgy technology demonstrates remarkable effectiveness in refining material microstructures.This strengthening mechanism is closely related to the interface characteristics between non-metallic inclusions and the matrix. Based on the two-dimensional mismatch theory and interface nucleation theory, a theoretical model was established to systematically evaluate the effectiveness of non-metallic inclusions in oxide metallurgy, and performed calculation verification with typical TiN inclusions as an example. First, the lattice matching of TiN with ferrite and austenite was calculated by the two-dimensional mismatch theory. The results show that the mismatch of TiN（100）/BCC-Fe（100） and TiN（110）/BCC-Fe（110） is 4.61%, indicating that TiN can serve as a potential substrate for ferrite nucleation. In contrast, the mismatch between TiN and austenite is large, making it difficult to form a stable interface structure. Subsequently, based on the surface convergence test, 5-layer BCC-Fe, 7-layer FCC-Fe and 9-layer TiN surface structures were selected to establish the interface structures. First-principles calculations of interface energies reveal that the adhesion work of TiN/FCC-Fe interfaces is negative, confirming that TiN cannot serve as a nucleation core for austenite. Instead, it hinders austenite grain growth and acts as a pinning mechanism. TiN/BCC-Fe interfaces exhibit positive adhesion work, indicating that TiN can effectively induce ferrite nucleation. Notably, the interface energy of TiN/BCC-Fe is significantly lower than that of TiN/FCC-Fe. This thermodynamic advantage provides a theoretical basis for the nucleation of ferrite within austenite. In the TiN/BCC-Fe system, the TiN（100）/BCC-Fe（100）-N interface has the larger adhesion work and the lowest interface energy, demonstrating the strongest stability. The electronic structure analysis reveals that Fe—N ionic bonds are formed at the interfaces of TiN（100）/BCC-Fe（100）-N, TiN（110）/BCC-Fe（110）-Ti and TiN（110）/BCC-Fe（110）-N. The study results provide a new theoretical perspective for understanding the inclusion-induced phase transformation mechanism in oxide metallurgy.
  • Industrial investigation and application on process of Ca increase by ferrosilicon alloy in CAS refining process
    WEN Han, ZHOU Haichen, JIA Liubing, LUO Yanzhao, HUANG Caide, ZHAO Changliang
    Iron and Steel. 2026, 61(2): 112-122. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250599
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    To address the challenges associated with conventional Ca treatment during CAS （composition adjustment by sealed argon bubbling） refining, such as low Ca yield, secondary oxidation of molten steel, long treatment period, and high production costs, and meantime to achieve the goal of reducing Ca treatment, a process that eliminated the need for traditional Ca treatment through Ca increase by ferrosilicon alloy was developed. Industrial trials were conducted on the high-silicon weathering steel SPAH （steel plate for atmospheric corrosion resistance-high strength）to investigate the influence of different Ca increase methods on molten steel cleanliness, inclusion evolution, and continuous casting castability during CAS refining process, and the mechanism of melting and inclusion generation of ferrosilicon was analyzed. The results indicate that during Ca treatment process, the average composition of inclusions in the tundish is 75.5%Al2O3-10.8%CaO-13.7%CaS. In contrast, for Ca increase by ferrosilicon alloy, the average inclusion composition in the tundish is 84.3%Al2O3-5.2%CaO-10.5%CaS. The types of inclusions on the hot rolling sheet under the two processes are similar, predominantly consisting of Al2O3-CaO-CaS. The number densities of inclusions lager than 5 μm are 1.19 mm- and 0.99 mm- for the Ca treatment process and Ca increase by ferrosilicon alloy, respectively. No large-sized inclusions are generated by adding ferrosilicon to the molten steel. Compared with traditional Ca treatment, the number density, average diameter, maximum diameter of inclusions as well as the molten steel cleanliness under the Ca increase by ferrosilicon alloy show less significant difference. The gradual release of residual Ca from the ferrosilicon prevents explosive oxidation, increasing the Ca yield from 12.5% to 45.1%. Furthermore, combining alloying and Ca addition into a single step by this process shortens the CAS refining period from 30 min to 22 min, and the fluctuation of stopper rod position and mold liquid level in continuous casting process is stable, so that the nozzle is continuously cast for more than 440 min without replacing. The Ca increase by ferrosilicon alloy can effectively replace the traditional Ca treatment, which provides both theoretical foundation and industrial solution for reducing Ca usage in aluminum-killed steels.
  • Research status and future prospects of CO2 application mechanisms in steelmaking-continuous casting
    ZHANG Yanchao, YANG Yaoqi, GUO Zhaofeng, LI Chenxiao, ZHANG Caijun, LÜ Xiaofang
    Iron and Steel. 2026, 61(2): 123-139. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250589
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    To address the steel industry's emission reduction pressure under global "carbon neutrality" goals, CO2 resource utilization in the steelmaking-continuous casting process has become a key low-carbon pathway. CO2's application mechanisms as a reaction medium, stirring gas, coolant and protective atmosphere are systematically explored, focuses on its industrial effects in converter blowing, electric arc furnace steelmaking, secondary refining and continuous casting, including covering dust/temperature control, energy/nitrogen reduction, inclusion removal and billet quality improvement. However, it yet notes three bottlenecks for its large-scale, high-quality promotion, namely unclear reaction kinetics and mass transfer under multiphase/multi-field coupling （mechanism）, poor economy due to high capture and equipment transformation costs （economy）, and severe equipment lifespan/safety impacts from CO2's corrosion on furnace linings and transportation systems （material）. To achieve this, it is proposed that future efforts require coordinated breakthroughs across three dimensions, that are basic research, technological development, and industrial application. By integrating in-situ observation and digital twin technologies, a full-process reaction kinetics database is established. Efforts focus on developing low-cost hydrogen injection technology, targeting less than 150 yuan/t, as well as combined utilization technologies for carbon dioxide, green hydrogen, and renewable energy, alongside durable corrosion-resistant materials. This ultimately advances the transition from single-point demonstration to full-process integration, establishes a standardized system and economic model, and delivers replicable, scalable integrated technical solutions for the green and low-carbon transformation of the steel industry.
    • Metal Forming
  • Model on coupling of roll wear-fatigue and equivalent conversion of rolling kilometers
    WANG Wenqi, CUI Xiaohui, ZHANG Jiantao, LIU Lulu, BAI Zhenhua
    Iron and Steel. 2026, 61(2): 140-149. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250483
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    The twenty-high rolling mill production line of a certain steel plant adopts a small batch, multi steel type and multi specification production mode. This production mode significantly complicates the on-site assessment of roll operating conditions. Coupled with the strict requirement for roll profile control accuracy in high-precision rolling mills, the on-site design of roll-related processes such as roll change cycles and roll grinding consumption lacks sufficient theoretical support and has to rely on previous production experience. As a result, the production cost caused by roll consumption remains relatively high while production efficiency is unsatisfactory. To solve the above problems, the equipment and process characteristics of the twenty-high rolling mill in the steel plant were fully considered. First,the structural characteristics of the twenty-high rolling mill rolling system were analyzed. The applicability of commonly used roll wear models and roll fatigue crack propagation models in engineering was discussed, and some key parameters in the models were regressed and calculated. A wear and fatigue calculation model suitable for on-site twenty-high rolling mills was proposed. Furthermore, in response to the current situation of independently considering roll wear and roll fatigue, a study was conducted on the coupling method of roll wear and roll fatigue. Finally, to address the issue that traditional rolling kilometers were difficult to guide roll change in small-batch and multi-specification rolling, the concept of equivalent rolling kilometers was introduced. The damage degree was defined by integrating the roll profile damage caused by roll wear and the damage induced by fatigue cracks. With the comprehensive damage degree used as a bridge for converting rolling kilometers between different loads, a set of equivalent rolling kilometers algorithms for the twenty-high rolling mill was developed. These algorithms can convert the roll rolling kilometers under different working conditions into those under the target working condition. When applied on-site, this technology can evaluate the roll status under different operating conditions using equivalent rolling kilometers, helping to enhance on-site understanding of roll conditions and optimize roll change timing. On the one hand, this approach helps reduce roll consumption and production costs. On the other hand, by accurately determining roll change timing, it can reduce production preparation time and thus improve production efficiency.
    • Materials
  • Effect of tempering temperature on microstructure and properties of Ti-Mo-V microalloyed steel
    FU Zhixiang, YANG Gengwei, HAN Ruyang, XU Yaowen, XU Deming, YANG Tingkai
    Iron and Steel. 2026, 61(2): 150-159. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250609
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    Under the backdrop of the "dual carbon" goal, developing lightweight steel materials that combine high strength with excellent ductility and toughness is a key focus for the automotive industry. A combined process route of "low-temperature coiling + tempering" was employed to tailor the precipitation behavior of microalloying second phases. The effects of tempering temperature on the microstructural evolution, precipitation behavior, and mechanical properties of Ti-Mo-V microalloyed steels were systematically studied.Results indicate that after tempering at 600,650,700,720 ℃, the microstructure of the experimental steel remains ferrite and granular bainite. Ferrite grain size shows no significant change, while granular bainite gradually decomposes. During tempering, a large number of V-enrich （Ti, Mo, V）C particles precipitate in the matrix, with their average size and volume fraction increasing from 4.93 nm and 0.205% at 600 ℃ to 8.73 nm and 0.517% at 720 ℃. Theoretical analysis indicates that elevated temperatures reduce interfacial energy between （Ti, Mo, V）C and ferrite matrix and enhance microalloying element diffusion rates, shortening the precipitation nucleation period of （Ti, Mo, V）C by approximately 3 orders of magnitude. However, this also accelerates （Ti, Mo, V）C coarsening, increasing its coarsening rate from 0.088 nm3/s1/3 at 600 ℃ to 0.681 nm3/s1/3 at 720 ℃, thereby diminishing the strengthening effect. At a tempering temperature of 700 ℃, the experimental steel achieves peak microhardness of 333HV and maximum precipitation strengthening of 287 MPa, representing a 72 MPa improvement over the hot-rolled condition. This provides theoretical guidance for controlling the microstructure and properties of Ti-Mo-V microalloyed ultra-high-strength steels.
  • Effects of V-N microalloying on microstructure and properties of high-strength shipbuilding steel
    FENG Zhiqiang, LI Boyong, ZHANG Dazheng, YAN Ling, XU Tingfeng
    Iron and Steel. 2026, 61(2): 160-171. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250526
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    V-N microalloying is an important approach for enhancing the mechanical properties of non-quenched and tempered shipbuilding steel plates. This study systematically characterized the microstructures of different microalloyed tested steels using OM（optical microscope）、SEM（scanning electron microscope）、TEM（transmission electron microscope） and EBSD（electron backscatter diffraction）, and evaluated their mechanical properties using a universal tensile testing machine and a metal Charpy V-notch pendulum impact tester. The results indicate that V-N microalloying effectively refines the grain size, reducing the average grain diameter to below 10 μm. Specifically, the grain size of the V-N tested steel is 9.1 μm, while the V-N-Ti tested steel exhibited the most significant refinement at 8 μm. More importantly, V-N microalloying promotes the formation of intragranular acicular ferrite and increases the proportion of high-angle grain boundaries, with the V-N tested steel achieving the highest proportion at 77% while the V-N-Ti tested steel reaches 63.4% . Additionally, finely dispersed V（C,N） and （Ti,V）（C,N） precipitates are formed. After V-N microalloying, the strength and plasticity of the tested steels are significantly improved. The strength of the V-N-Ti tested steel is further enhanced compared with the V-N steel but its plasticity decreases. Under low-temperature impact testing at -60 ℃, the impact absorbed energy and crack propagation energy of the V-N microalloyed steels increase markedly. The fracture mode shifts from the brittle fracture dominated by quasi-cleavage in the 0V-0Ti tested steel to microvoid coalescence ductile fracture with numerous equiaxed dimples in the V-N tested steel. However, due to the reduced proportion of high-angle grain boundaries and coarsening of precipitates, the low-temperature toughness of the V-N-Ti tested steel deteriorated to some extent compared with the V-N steel. V-N microalloying achieves a comprehensive improvement in the strength and toughness of shipbuilding steel through a synergistic mechanism of "grain refinement+acicular ferrite regulation+nano-precipitation". While the addition of Ti enhances precipitation strengthening but also imposes constraints on toughness. The V-N steel achieves the optimal balance of strength, plasticity and low-temperature toughness.
  • Low-temperature impact fracture failure mechanism of Q490DRL2 pressure vessel steel plate
    SUN Haoyuan, QU Wei, SUN Weihua, REN Huiping, LIU Peng, LI Guobao, SHI Chengbin, KONG Ya
    Iron and Steel. 2026, 61(2): 172-183. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250510
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    To address the issue of substandard low-temperature impact toughness at the 1/2 thickness position in Q490DRL2 pressure vessel steel, this study investigates the fracture failure mechanism under low-temperature impact loading, providing theoretical insights for improving the low-temperature impact performance of pressure vessel steels. Oscillatory impact testing was conducted to measure the impact energy and force-displacement curves of the steel at both the 1/4 and 1/2 thickness positions at -50 ℃. Field-emission scanning electron microscopy （FESEM） and electron backscatter diffraction （EBSD） were employed to analyze the fracture morphology, inclusion characteristics, microstructure, and grain size distribution. Additionally, physicochemical phase analysis and small-angle X-ray scattering （SAXS） were utilized to quantitatively assess the composition and particle size distribution of precipitates. Finite element method （FEM） simulations were performed to analyze the stress field distribution around inclusions during impact. The results indicate that the microstructure at both the 1/4 and 1/2 thickness positions consists of tempered sorbite, with average grain sizes of 5.35 μm and 4.36 μm, respectively, and dislocation densities of 7.22×108 m-2 and 7.88×108 m-2, respectively. The primary precipitates in the steel are M3C （alloy cementite） and MC （Nb, Ti, V-based） carbides, with no significant differences in alloy element content or particle size distribution observed between the two thickness regions. Further analysis reveals that the primary cause of the unsatisfactory low-temperature impact toughness at the 1/2 thickness position is the presence of a higher density of silicon-rich, triangular-shaped inclusions. Under impact loading, when crack propagation encounters these inclusions, significant stress concentration occurs in their vicinity, leading to rapid fracture failure of the steel.
  • Effect of heat input on microstructure and properties of coarse-grain heat affected zone in duplex stainless steel
    ZHAO Lidong, ZANG Ximin, WANG Dihe, PANG Qihang, LI Weijuan, XU Mei
    Iron and Steel. 2026, 61(2): 184-194. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250564
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    Against the backdrop of growing demand for high-efficiency welding technologies in large-scale manufacturing, economical S32101 duplex stainless steel has demonstrated significant potential in heavy equipment manufacturing due to its excellent performance. However, the challenge of achieving desirable strength-toughness balance in the welded joint caused by high welding heat input remains a key constraint on its application. In order to systematically reveal the effect of heat input on the microstructure and properties of coarse grain heat affected zone （CGHAZ） of economical S32101 duplex stainless steel, the microstructure evolution, strengthening and toughening mechanism of CGHAZ in economical S32101 duplex stainless steel under different heat input were analyzed by means of thermal simulation test machine, electron backscatter diffraction （EBSD） and transmission electron microscopy （TEM）. The results show that the microstructure of CGHAZ in economical S32101 duplex stainless steel consists of austenite （γ-Fe）, ferrite （α-Fe）, and Cr2N precipitates. The austenite phase exhibits three morphologies, that is grain boundary austenite （GBA）, Widmanstätten austenite （WA）, and intragranular austenite （IGA）. As the heat input increases from 20 kJ/cm to 100 kJ/cm, the proportion of austenite phase shows an increasing trend, and its average grain size gradually increases. At heat input of 100 kJ/cm, the ratio of ferrite to austenite in the CGHAZ microstructure approaches balanced state of nearly 1∶1. The increase in austenite content promotes higher proportion of nitrogen atoms in solid solution, effectively suppressing the precipitation of Cr2N. The CGHAZ of economic S32101 duplex stainless steel exhibits the best comprehensive mechanical properties at heat input of 100 kJ/cm, with product of strength and elongation of 19.63 GPa·%, yield ratio of 0.76, and low-temperature impact energy of 48 J. The strengthening mechanism of CGHAZ arises from the synergistic effects of grain refinement strengthening, dislocation strengthening, and second-phase strengthening, while the toughening mechanism is influenced by the combined effects of second-phase morphology, austenite morphology, and austenite grain size.
  • Comparison of microstructure and corrosion behavior among Zn-0.2%Al, Zn-6%Al-3%Mg, and Zn-19%Al-6%Mg
    LI Zhao, LI Yuanpeng, JIANG Sheming, ZHANG Jie, QIAO Degao
    Iron and Steel. 2026, 61(2): 195-204. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250565
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    In recent years, the development of coating alloys has become increasingly diversified, with new types such as zinc, aluminum-zinc, and zinc-aluminum-magnesium coatings emerging successively. The current research indicates that the co-addition of magnesium and aluminum in zinc-based coatings can significantly enhance their corrosion resistance. Magnesium can compensate for the limitations of aluminum in protecting cut edges, while also improving coating hardness and wear resistance. Its application potential still requires further in-depth exploration. GI （Zn-0.2%Al）, Zn-6%Al-3%Mg, and Zn-19%Al-6%Mg （mass fraction） were prepared by hot-dip coating simulator. These coatings were systematically analyzed using methods such as X-ray diffraction （XRD）, scanning electron microscopy equipped with energy-dispersive spectroscopy （SEM-EDS）, microhardness testing, salt spray testing, and electrochemical corrosion testing to examine their surface morphology, cross-sectional microstructure, microhardness, and corrosion behavior. Pandat simulation results reveal that in the Zn-Al-Mg ternary system, the distance between coating composition point and ternary eutectic point directly determines its melting point, the farther the distance, the higher the melting point. Microstructural analysis shows that as the aluminum and magnesium content increases, the coating grains refine, and the zinc-rich phase decreases, effectively hindering dislocation movement and thereby improving hardness and strength of coating. Among them, the average microhardness of Zn-19%Al-6%Mg coating is 260.077HV, approximately twice that of Zn-6%Al-3%Mg and four times that of the GI pure zinc coating. Electrochemical corrosion test results indicate that the corrosion current density of Zn-19%Al-6%Mg coating is 915 μA/cm2, lower than that of Zn-6%Al-3%Mg （1 570 μA） and GI coating （1 940 μA）, demonstrating the best corrosion resistance. The improved corrosion resistance of this coating is mainly attributed to the formation of stable Mg6Al2 （OH）16CO3·4H2O corrosion product on the surface. The higher Mg2+ mass fraction effectively delays the formation of Zn6Al2（OH）16CO3·4H2O, enhancing the stability of the rust layer.
  • Formation of intragranular ferrite in weld heat-affected zone and its influence on microstructure
    CAO Shengli, ZHANG Caijun, ZHANG Qingjun, WU Shujing, LI Kuo
    Iron and Steel. 2026, 61(2): 205-215. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250500
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    The formation of intragranular ferrite during the welding process can improve the microstructure of the weld heat-affected zone（HAZ） and enhance its low-temperature impact toughness. This study employed high-temperature laser scanning confocal microscopy to conduct in-situ observations of the formation of intragranular ferrite and its behavior in partitioning austenite grains. Focused ion beam（FIB） was utilized for site-specific preparation of micro-interface samples between inclusions and between inclusions and ferrite. Transmission electron microscopy was employed for micro-interface analysis to elucidate the nucleation mechanism induced by TiN from the perspective of mismatch. The existence of a manganese-depleted zone was in-situ demonstrated using instruments such as nanoindentation. Finally, electron backscatter diffraction（EBSD） was used to analyze the crystallographic information of intragranular ferrite. The research findings are as follows. Intragranular ferrite nucleates and grows near inclusions to form acicular-like ferrite, and ceases growth upon encountering pre-existing ferrite or austenite grain boundaries. Intragranular ferrite can partition austenite grains and optimize the microstructure of the weld heat-affected zone. The composite inclusions in this steel induce intragranular ferrite through two mechanisms. The mismatch between the （210） plane of TiN and the （210） plane of ferrite is 4.76%, which indicates a coherent relationship that effectively promotes nucleation. The hardness of the intragranular ferrite lath induced by MnS is significantly lower on the inclusion-adjacent side than on the side far from inclusions, indirectly confirming the existence of a manganese-depleted zone from the perspective of hardness variation. The dislocation density of primary intragranular ferrite is significantly higher than that of secondary intragranular ferrite, suggesting that the formation of secondary ferrite is stress-induced nucleation. Intragranular ferrite laths induced by the same inclusion and those induced by other inclusions are separated by high-angle grain boundaries.
  • Investigation of primary phases in Ce-containing heat-resistant steel electroslag remelting ingots
    RAN Gang, YAN Qingzhi, ZHANG Xiaoxin
    Iron and Steel. 2026, 61(2): 216-230. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250487
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    Strong carbide-forming elements （e.g., Nb, Ti） in ferrite/martensite （F/M） heat-resistant steels tend to form coarse primary phases during the solidification of molten steel, which significantly impairs the steels' creep and fatigue properties. Therefore, modulating the composition and size of these primary phases is crucial for enhancing the mechanical properties of such steels. Numerous studies have confirmed that both electroslag remelting （ESR） and rare earth modification are well-established methods for regulating the primary phase in steel. There is a lock of relevant research on the effect of the combined oution of the two on the primary phases of liquaation in F/M heat-resistant steel. This study investigates the precipitation behavior of secondary phases in Ce-containing 10Cr1Si F/M steel following electroslag remelting （ESR）. Scanning electron microscopy （SEM） and ASPEX automated SEM were employed to conduct statistical analysis on the primary phases in the ESR ingot of this steel. The results reveal three dominant precipitates across different positions of the ingot （i.e., top, bottom, center, and edge）,namely black spherical rare earth oxide CeAlO3, polygonal nitride TiN, and acicular/striated carbide NbC. Their maximum number densities are （29.1±6.14）×1010,（1.42±0.29）×1010,（2.15±0.99）×1010/m3, respectively. Among these precipitates, NbC exhibits the largest size （about 3 μm）, whereas TiN and the rare earth oxide （CeAlO3） have comparable sizes of approximately 2.0 μm, and 1.5 μm, respectively. Furthermore, the primary phases exhibit diverse structural configurations, including bilayer structures （TiN-NbC, CeAlO3-Al2O3）, three-layer structures （CeAlO3-Al2O3- NbC）, and four-layer structures （CeAlO3-Al2O3-TiN-NbC）. Thermodynamic calculations and misfit theory were applied to clarify the formation mechanism of these multi-layered structures.Owing to the slag-metal reaction and element segregation during solidification, CeAlO3, Al2O3, TiN, and NbC are sequentially formed in the molten steel. The interfacial relationships among these precipitated phases exhibit a certain degree of matching, and heterogeneous nucleation occurs between the primary phases, thereby promoting the formation of various core-shell structures. This study provides an experimental foundation for understanding and regulating secondary phases in rare earth-containing heat-resistant steels.
    • Environmental Protection and Energy
  • Carbon footprint analysis and carbon reduction path research of automotive hot-dip galvanized sheet
    WANG Qian, LIANG Chuanzhi, WEI Guangsheng, XIE Rongyuan, LI Menglong
    Iron and Steel. 2026, 61(2): 231-245. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250468
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    Under the guidance of the "3060" dual-carbon goals, downstream automotive customers have clearly put forward requirements for carbon footprint disclosure of steel products. To accurately quantify the carbon emission level of automotive steel products, this paper took the life cycle assessment （LCA） method as the core, constructed a carbon footprint assessment model for automotive hot-dip galvanized sheets, conducted full-process quantitative accounting, and analyzed the characteristics of carbon emission contribution and carbon reduction potential. The accounting results show that the carbon footprint of producing 1 kg of hot-dip galvanized sheets is 2.508 kg CO2. From the perspective of life cycle stages, the production link accounts for the highest proportion of carbon emissions, reaching 60%, the upstream raw material mining and energy production link ranks second, accounting for 38%, the transportation link accounts for the lowest proportion, only 2%. From the perspective of production processes, the key carbon-emitting processes and their proportions are as follows, blast furnace process （26%）, sintering process （22%）, hot rolling process （14%）, steelmaking process （11%）, and galvanizing process （9%）. To further explore the carbon reduction paths of each production process unit, this paper took the intermediate products from the above five key processes as the objects of carbon footprint evaluation, and deeply analyzed their carbon footprint composition and carbon reduction potential space. Taking the existing process route of hot-dip galvanizing as the baseline scenario, carbon reduction scenario analysis was carried out focusing on "increasing the pellet ratio before ironmaking" and "improving the scrap steel ratio in steelmaking". The results show that when the full-process scrap steel ratio is increased to 50% （process limit value）, the carbon footprint of long-process automotive steel sheets can be reduced by 40% compared with the baseline value. If external purchase of green electricity is used in this scenario, the carbon footprint can be further reduced by 5%.
  • Difference of Ca extraction characteristics of steel slag in various acidic solutions
    MEI Xiaohui, XU Taixu, ZHAO Qing, SUN Ye, HUANG Yan, LIU Chengjun
    Iron and Steel. 2026, 61(2): 246-256. https://doi.org/10.13228/j.boyuan.issn0449-749x.20250453
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    Steel slag is a complex heterogeneous material composed of multiple components and coexisting mineral phases. The low efficiency of selective Ca extraction severely restricts the large-scale application of steel slag in CO2 mineralization technology. Basic oxygen furnace （BOF） slag from a steel plant was selected as the research material. Leaching experiments were carried out in three representative solutions, HCl （a strong acid）, CH3COOH （a weak acid）, and NH4Cl （a salt with acidic cations）. The leaching behaviors of major elements （Ca, Mg, Fe, and Si） in BOF slag were systematically analyzed. Furthermore, the mineral phase transformations and morphological evolution of BOF slag before and after leaching were investigated using X-ray diffraction （XRD） and scanning electron microscopy （SEM）. This analysis aimed to establish a structure-activity relationship among the solution environment, mineral dissolution, and elemental release. The results show that Ca in BOF slag mainly exists in tricalcium silicate （Ca3SiO5）, dicalcium ferrite （Ca2Fe2O5）, and free calcium oxide （CaO） phases. The major components （Ca, Mg, Fe, and Si） in BOF slag exhibit a high leaching yield （>90%） in HCl solution, while NH4Cl solution shows excellent selective Ca leaching performance for BOF slag, with a Ca2+ leaching yield of 54%. The Ca2+ leaching yield of BOF slag is determined by both the solution environment and the type of Ca-bearing mineral phase. In HCl （strong acid） solution, the Ca-bearing mineral phases in BOF slag undergoes significant dissolution, in contrast, in CH3COOH and NH4Cl solutions, Ca3SiO5 and CaO show high solubility, while Ca2Fe2O5 exhibit leaching inertness. Additionally, the solubility of Ca-bearing phases in BOF slag is associated with their crystal structures, Ca3SiO5 is composed of [SiO4]4- tetrahedral monomers, which are easily soluble in the tested solution environments, whereas Ca2Fe2O5 crystals have high Fe—O bond energy and complex anionic chain structures, making it difficult to decompose the Ca2Fe2O5 mineral phase under weak acid and ammonium salt conditions. Future research should focus on the targeted regulation of molten slag mineral phases to enrich calcium components predominantly in the forms of CaO and Ca3SiO5. This approach will be conducive to improving the efficiency of selective Ca extraction from steel slag.
Started in 1954 (Monthly)
ISSN 0449-749X　CN 11-2118/TF
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