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28 October 2026, Volume 43 Issue 5
    

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    Overview
  • ZHANG Xiangjun, LU Yong, CHEN Zhiqiang, ZHU Fengquan, XU Yong, YANG Yong, SHEN Xinjun
    Abstract ( )   Knowledge map   Save
    In finishing collection area of hot-rolled bar, both non-standard length bar which is shorter than standard-length bar and defective hot-rolled bars must be removed. The development status and history of rejection technology of hot-rolled bars in China was sorted out in this article. The existing technologies, from traditionally manual rejection to AI-based automatic rejection technologies, were systematically classified, compared and analyzed according to their characteristics of specific structural form, characteristics of different technical scheme and installation location. The future development direction of rejection technology in China was prospected, based on the current development level of rejection technology and its related technology.
  • AI+Steel Rolling
  • LIU Zhaoyu, WEN Changfei
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    Ti-microalloyed steels are widely used due to their significant cost-effectiveness and excellent mechanical properties. However, variations in chemical composition during the production process lead to significant fluctuations in the mechanical properties of the final product, which not only affect the final product quality but also limit the full realization of the material′s potential. Therefore, Based on industrial big data, this paper employs various machine learning algorithms to establish prediction models for the mechanical properties of hot-rolled Ti-microalloyed steel. The optimal model suitable for the current production line was selected, and an intelligent optimization method for the hot-rolling process was developed specifically for the 510L steel grade, enabling rapid optimization of hot-rolling process parameters, The results show that the Random Forest model is best suited for the current production line.For yield strength and tensile strength, the random forest moolel achieved accuracy rates of 92.5% and 96.63%, respectively, within an absolute error range of ±30 MPa.For elongation, the random forest model achieved an accuracy rate 94% within an absolute error range of ±3%. Through process optimization, the fluctuation range of the yield strength of 510L steel plates was reduced from 66 MPa to 42 MPa, the fluctuation range of tensile strength was reduced from 59 MPa to 40 MPa, and the fluctuation range of elongation was reduced from 11.5% to 6%.
  • XUAN Ruifei, XU Tingfeng, ZHANG Dazheng, FENG Zhiqiang, WANG Xingyu, LI Weijuan
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    Traditional steel products development relies heavily on trial-and-error methods, which suffer from long cycles, high costs, and difficulties in accurately correlating chemical composition with performance. To improve efficiency and reduce costs, this study constructs an integrated model of XGBoost and LightGBMbase on production data of a steel mill to perform multi-target regression predictions for the yield strength, tensile strength, and total elongation at maximum force of HRB400E hot-rolled ribbed bars. The results indicate that the LightGBM model outperforms the others, achieving coefficients of determination (R2) of 0.953 66, 0.980 15, and 0.946 74 for yield strength, tensile strength, and total elongation at maximum force, respectively, on the test set. To further enhance model interpretability, derivative features generated by a physical metallurgical model were incorporated into the LightGBM model. On the test set, the coefficients of determination (R2) for the three properties reached 0.965 03, 0.985 52, and 0.956 30, respectively. The MAE decreased by 12.54%, 13.25%, and 6.39%, while the RMSE was reduced by 13.13%, 14.58%, and 9.39%, respectively. This data-mechanism integrated driving combines high accuracy and interpretability, providing an efficient and reliable solution for intelligent steel manufacturing.
  • ZHU Furong, ZHANG Tian, ZHANG Bowen, YAN Gehua, WANG Bingxing, TIAN Yong
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    Controlling the final cooling temperature of medium and heavy steel plates after rolling is a core technology for improving product quality and production efficiency; the accurate prediction and regulation of the final cooling temperature hit rate has attracted widespread attention from both academia and industry. In recent years, algorithms such as Random Forests, RNNs and LightGBM have demonstrated outstanding performance in predicting post-rolling cooling temperatures for hot-rolled steel materials, owing to their excellent non-linear mapping capabilities. However, when the LightGBM model employs the leaf with the highest gain as the split point in its leaf-wise growth strategy, this may result in single-point greedy selection, causing the model to become trapped in a local optimum and overlook other potential high-gain regions. This paper proposes a method based on the average gain across multiple leaves to optimise the splitting and growth mechanism of the model′s leaf nodes. When selecting splitting nodes, the improved algorithm not only considers the leaf with the current maximum gain but also comprehensively takes into account other potential high-gain leaves. This avoids the model becoming unstable or overfitting due to local optima caused by noise in the gain of a single leaf. Experiments utilised 16 input features, including C and Si content, as well as steel plate length, thickness and final rolling temperature, with final cooling temperature as the output feature. The results indicate that, compared with other models, the improved LightGBM algorithm achieved a 30% in training efficiency whilst maintaining model accuracy and stability, The absolute error for 95% of the predicted samples can be controlled within ±10 ℃, making the model suitable for the online prediction of final cooling temperature in the post-rolling cooling process of hot-rolled steel plates.
  • ZHOU Jianxin, LI Zhongze, HOU Zichuan, HAO Yingjie
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    To tackle diverse defect categories and low detection accuracy of micro-defects on steel plate surfaces, this paper proposes YOLO-OME, a surface defect detection model based on YOLOv11n. An ODC_C3k2 module is designed to replace the original C3k2 module, reducing computational redundancy and boosting detection accuracy for small objects. A hybrid local channel attention mechanism is introduced to improve the C2SPA module, enhancing detection performance under complex backgrounds and network feature representation. An efficient up-convolution block (EUCB) replaces the Upsample operation to cut computational complexity, preserve feature map details, and improve model performance and efficiency. Shape-IoU is adopted to substitute the original loss function for higher detection accuracy. Experiments show that the proposed algorithm achieves a 2.3% mAP50improvement on the NEU-DET dataset and delivers promising performance for steel plate surface defect detection.
  • Advanced Steel Materials
  • SUN Zhexu, GAO Yuhan, LI Ziyu, PENG Tiankun, JIANG Jiale, LI Yunjie
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    300M steel has gradually become the mainstream steel used for aircraft landing gears nowadays due to its low alloy content and excellent mechanical properties. However, with the development of the times, it has become a major challenge to develop steel for aircraft landing gears that can simultaneously achieve higher strength and better toughness. Therefore, based on the composition of 300M steel, the 2.4 GPa grade ultra-high-strength experimental steel was designed by using the method of "Mn+microalloying", and the study examined how the austenitizing temperature influences the microstructure and mechanical properties of the experimental steel. As the austenitizing temperature continuously increases, the fine banded and equiaxed original austenite grains transform into coarse equiaxed structures. When austenitizing at 780 ℃, the width of the banded grains is approximately 5.1 μm and the length is about 12 μm, while the width of the equiaxed grains is approximately 3 μm and the length is about 4 μm. When the austenitizing temperature rises to 850 ℃, most of the original austenite exists in the form of banded grains, with a grain size of approximately 16.7 μm in width and 40 μm in length. The content of retained austenite at room temperature decreases from 23.96% (780 ℃ austenitizing)to 18.88%(800 ℃ austenitizing) and then increases to 20.37%(850 ℃ austenitizing). The dislocation density of the experimental steel decreases from 7.2×1015 m-2 (780 ℃ austenitizing) to 6.8×1015 m-2 (800 ℃ austenitizing) and then further drops to 6.4×1015 m-2(850 ℃ austenitizing).The specimen austenitized at 800 ℃ exhibits the best comprehensive mechanical properties, with an impact toughness of 26.7 J/cm2, a yield strength of 2 009 MPa, a tensile strength of 2 375 MPa, a uniform elongation of 7.6%, and an elongation after fracture of 15.3%.This study provides a route for lightweight landing-gear steel design,and helps promote the technical iteration and engineering implementation of aeronautical ultra-high-strength steels.
  • YAO Xianning, DONG Futao, QIAN Xinyi, LIU Yi, ZHANG Shan, DAI Xin, HU Baojia, CHEN Jun, TIAN Yaqiang, XU Wanqiang
    Abstract ( )   Knowledge map   Save
    Three different controlled cooling processes were used to produce X65 pipeline steel in an experimental hot rolling line. By combining tensile, impact, electrochemical hydrogen charging and other performance tests, as well as microstructure characterization analysis such as OM and SEM, the effect of the controlled cooling process on microstructure and properties of the pipeline steel was investigated, especially for the low-temperature impact toughness and hydrogen embrittlement susceptibility. The results show that with the increase of the cooling rate after hot rolling, the microstructure of X65 pipeline steel undergoes a change from polygonal ferrite to sub-polygonal ferrite, and then acicular ferrite. The effect of fine-grain strengthening is obvious, but the plasticity is reduced. Impact toughness is significantly affected by the controlled cooling process. Using medium cooling rate (laminar cooling at a rate about 20 ℃/s), the pipeline steel has the best impact toughness; when the cooling rate is relatively higher (laminar cooling at a rate about 50 ℃/s), the impact energy of the pipeline steel decreases significantly. The pipeline steel of all three cooling processes undergoes the ductile-brittle transition within the temperature range of -55 ℃ to -80 ℃. After 72 h hydrogen charging, the impact energy of the pipeline steel has decreased to varying degrees, but the fracture characteristics remained ductile. Among the pipeline steels, those cooled at a laminar flow rate of about 50 ℃/s exhibit the lowest loss rate in toughness after hydrogen charging. This is mainly because acicular ferrite has a lower hydrogen-induced crack sensitivity.
  • WANG Chaoyi, ZHANG Ning, LI Wenbin, LI Sen, LI Jiaan
    Abstract ( )   Knowledge map   Save
    To study the microstructure and low-temperature toughness of 500 MPa grade high-strength marine equipment steel, a low-carbon and low-alloy system chemical composition design was adopted. A 38 mm thickness high-strength marine equipment steel was prepared by the thermo-mechanical control process(TMCP). The microstructure morphology, strength and low-temperature impact toughness of the material were analyzed. The characteristic values of the crack-tip open displacement (CTOD) of the material in a low-temperature environment of -20 ℃ were further tested. It was found that the microstructure of the test steel was mainly polygonal ferrite (PF)+ granular bainite (GB). The final yield strength of the steel plate was greater than 520 MPa, with good strength uniformity. The low-temperature impact toughness met the requirements of E-grade marine engineering steel, and the maximum characteristic value δm of CTOD in a -20 ℃ low-temperature environment was approximately 2.0 mm. Electron backscatter diffraction(EBSD) analysis indicates that the proportion of large-angle grain boundaries (>15°) in the material's microstructure is approximately 43.2%. The results of the oscillographic impact test show that as the temperature drops, the crack formation work of the material changes little, while the crack propagation work decreases significantly. At low temperatures, the stress field intensity at the crack tip is higher than the cleavage fracture strength between grains, causing the microstructure to lose its ability to resist crack propagation. This is one of the main reasons for the decline in the low-temperature toughness of materials.
  • ZHENG Simin, TIAN Baoqian, WU Hao, JIA Pan, SUN Jie, PENG Wen
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    Hot-rolled dual-phase steel, with its excellent comprehensive properties, well meets the urgent demands of the automotive industry for lightweighting and safety. Post-coiling cooling serves as a critical manufacturing procedure for hot-rolled dual-phase steel, which governs the morphology and fraction of microstructures and is therefore essential for the property control of final dual-phase steel products. At present, air cooling is commonly adopted for coiled steel after hot rolling. Nevertheless, this technique suffers from drawbacks including uncontrollable cooling rates, low precision in phase fraction adjustment and unstable mechanical properties, making it difficult to satisfy the industrial production requirements of hot-rolled dual-phase steel. Accordingly, a slow-cooling process is proposed for the typical 590DP steel grade in this work, and the evolution rules of temperature and phase transformation during coil cooling are investigated. Firstly, a temperature-phase transformation coupled model for coil cooling is established via the UMAT subroutine in Abaqus to reveal the coupling mechanism between temperature variation and phase transformation. Secondly, on-site temperature measurements obtained using a thermal imager are adopted to validate the numerical model. Finally, the effects of air cooling and slow cooling on coil temperature distribution and microstructure evolution are compared and analyzed. The results demonstrate that the latent heat released during phase transformation imposes a remarkable influence on the temperature field of the cooling coil. Neglecting the phase-change latent heat will lead to a maximum calculation error of 144.32 ℃. Moreover, the slow-cooling strategy substantially improves the uniformity of temperature and phase distribution within the coil. Compared with conventional air cooling, the maximum core-surface temperature difference of the strip decreases by 56.72% under slow cooling, and the maximum deviation in the volume fractions of ferrite and martensite between the core and surface regions drops by 37.50% upon cooling completion.
  • SHI Yipu, LI Huaying, CHEN Qi, HUANG Fang, QIAO Jinchao, SONG Yaohui
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    To realize the production of high-performance electromagnetic pure iron, it is essential to reasonably match the cold-rolling reduction ratio and intermediate annealing temperature for the collaborative optimization of process parameters. In this paper, 0.3 mm thickness sheets of electromagnetic pure iron were prepared by a double-cold-rolling process. By means of optical microscopy (OM), X-ray diffraction (XRD) and square-loop magnetic property measurements, the evolution of microstructure and texture for intermediate-annealed sheets, secondary-cold-rolled sheets and final-annealed sheets was investigated under different intermediate annealing temperatures (850, 900, 950, 1 000, 1 050 ℃). The results demonstrate that the intermediate annealing temperature exerts a significant influence on the microstructure uniformity and grain size of final-annealed sheets. As the intermediate annealing temperature increases, the average grain size firstly increases and then tends to stabilize, reaching a peak value of 93.2 μm for the final sheet intermediate-annealed at 900 ℃. The intermediate annealing temperature also remarkably affects the texture-evolution behavior of final-annealed sheets. With increasing intermediate annealing temperature, the Goss texture in final-annealed sheets is first strengthened and then disappears, while the intensity of γ-fiber texture increases first and then decreases. The maximum intensity of Goss texture is obtained for the final sheet subjected to intermediate annealing at 950 ℃. The secondary-cold-rolled sheets possess the largest number of shear bands, which provide abundant nucleation sites for the formation of α-texture and Goss texture during the final annealing process, and thus are beneficial to optimizing the texture evolution of the final sheets.
  • Research and Development
  • YU Qing, GAO Qing, LIU Wei, TIAN Yong
    Steel Rolling. 2026, 43(5): 93-102. https://doi.org/10.13228/j.boyuan.issn1003-9996.20260511
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    In this study, a Nb-Ti microalloyed steel with high ferritic content was successfully prepared by a novel reciprocating austenitizing process. The study on microstructure evolution, quasi-static tensile properties, dynamic Charpy impact toughness and fracture behavior of the experimental steels were deeply investigated. The plate was compared to a plate prepared by conventional thermo-mechanical processing. The results manifests that the new technology effectively regulates the grain size of austenite grain and optimizes the distribution of the driving force behind phase transitions, thereby facilitating the development of a ferrite microstructure in S2 steel. The strength grade of the newly developed S2 steel is comparable to that of plates prepared using the traditional thermomechanical control process. However, the total elongation has been improved, with a room-temperature yield strength of 490 MPa and an elongation of 21.6%. More importantly, the steel exhibits excellent low-temperature toughness, with an impact absorption energy of 134.3 J at -60 ℃. This value is 6.5 times higher than that of the plate prepared using the traditional thermomechanical control process under the same conditions. The synergistic effects of a high content of soft polygonal ferrite phase, grain refinement, low fault density, and a high proportion of high-angle grain boundaries collectively enhance the mechanical properties of the steel.
  • WANG Yisong, LI Bingya, MAO Xiaoyu, JIANG Yu′nan, ZHANG Hongliang, WANG Siqiao, ZHOU Xiaoguang
    Steel Rolling. 2026, 43(5): 103-109. https://doi.org/10.13228/j.boyuan.issn1003-9996.20260512
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    In order to establish a flow stress model of low-carbon Al containing steel under the deformation conditions of austenite+ferrite two-phase zone, a series of experiments were designed to analyze the influence factors of the flow stress of the experimental steel in the two-phase zone deformation, and a flow stress model of the experimental steel under the deformation conditions in two-phase zone was established. The main research results are as follows:ferrite transformation temperature of experimental steel are between 680-810 ℃, When the deformation processes are the same, as the volume fraction of ferrite transformation before deformation increases, the flow stress in the two-phase zone deformation gradually decreases. The Zhou Jihua-Guan Kezhi model was used to accurately predict the flow stress in the austenite zone deformation of experimental steel, but it is not applicable to predict the flow stress in the austenite+ferrite two-phase zone deformation. Taking into account deformation parameters, ferrite volume fraction before deformation, and flow stress in austenite, high-precision prediction of flow stress in the austenite+ferrite two-phase zone deformation of experimental steel was carried out based on support vector machine(SVM) algorithm. The model correlation coefficient R2 is 0.974 39, and the root mean square error(RMSE) is 3.993 12 MPa. The research results are of great significance for the accurate prediction and setting of rolling force under deformation conditions in the two-phase zone of low-carbon Al containing steel.
  • WANG Hemu, GAO Qing, YANG Yan, ZHANG Yongwei, PENG Fei, ZHANG Kaiming, YUAN Wuhua
    Steel Rolling. 2026, 43(5): 110-116. https://doi.org/10.13228/j.boyuan.issn1003-9996.20260513
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    To effectively eliminate banded structures in Q345R(R-HIC) hydrogen-resistant steel, this study investigated the elemental segregation behavior during the hot rolling process of Q345R(R-HIC) steel using a Gleeble 3800 thermal simulation testing machine, optical microscopy (OM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The microstructural characteristics of the banded structure formation process in the hot-rolled strip after air cooling were analyzed. Based on these results, the effects of finishing rolling temperature and cooling rate after rolling on the banded structure were further investigated. The results show that Mn and Si segregation always exists during the rolling process of Q345R(R-HIC) steel, with Mn segregation being dominant. The spacing between segregation bands gradually decreases during the hot rolling process. During air cooling after rolling, ferrite transformation preferentially occurs in Mn-depleted regions, where ferrite rapidly grows and connects into bands. In contrast, Mn-rich regions transform into ferrite only during further cooling, with a lower ferrite fraction and a greater tendency to form continuous pearlite bands. With increasing finishing rolling temperature, the ferrite grain size gradually increases, while the severity of banded structures decreases. When the cooling rate after rolling is below 5 ℃/s, the microstructure of Q345R(R-HIC) steel mainly consists of ferrite and pearlite. When the cooling rate is equal to or higher than 5 ℃/s, the microstructure is dominated by bainite and martensite. With increasing cooling rate after rolling, the banded structure is significantly reduced. The optimal cooling rate after rolling is determined to be 2-5 ℃/s.
  • GUO Shudong, CHENG Hexin, MA Yanming, JIANG Lianyun, QIAO Fuzhen
    Steel Rolling. 2026, 43(5): 117-126. https://doi.org/10.13228/j.boyuan.issn1003-9996.20260514
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    The post-rolling interlayer thickness ratio of metal composite plates is a critical parameter affecting their quality and performance. Therefore, predicting the post-rolling interlayer thickness ratio by analyzing rolling process parameters, and adjusting the parameters to achieve ideal interlayer thickness control, are core technical means to improve the quality of composite plate products.Based on the upper-bound method theory, this study mathematically analyzes the asynchronous rolling bonding process of three-layer metal sheets with the same diameter but different speeds. It breaks through the rigid-plastic assumption of the inlet cross-section in the traditional deformation zone and establishes an inlet shape function that is more consistent with actual rolling conditions. The velocity field in the deformation zone is fitted by elliptic functions, and the contact boundary conditions are described by quadratic functions. A strain rate field model and a power calculation model for the rolling bonding deformation zone are developed. Combined with the genetic algorithm in the MATLAB optimization toolbox for global optimization of the total power functional, a mathematical model for predicting the post-rolling interlayer thickness of dissimilar metal composite plates is established.A finite element model for rolling NM400/Q345/NM400 (wear-resistant steel/carbon steel/wear-resistant steel) composite plates is developed based on ANSYS, and rolling experiments of 5052/AZ31B/5052 (Al/Mg/Al) composite plates are carried out under laboratory conditions. The results show that the maximum relative errors between the model calculations and the finite element simulation and experimental results are 13.6% and 10%, respectively, verifying the reliability of the model. The model can not only predict the interlayer thickness of composite plates but also obtain the influence laws of different rolling parameters on the interlayer thickness, thereby positively regulating and optimizing the rolling process parameters.
  • YANG Xiaowei, YANG Zhaoquan, ZHANG Yu, MA Han
    Steel Rolling. 2026, 43(5): 127-134. https://doi.org/10.13228/j.boyuan.issn1003-9996.20260515
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    The weight of new energy vehicles were increased over 20% compared to traditional fuel vehicles, and the design stress of suspension springs in their shock absorption systems has increased from 1 200 MPa to 1 300 MPa, the development and application of various high-strength automotive suspension spring steels have become a hot topic. Continues cooling and isothermal phase transformation process behavior of the super-cooled austenite 55SiCrV test steel were studied by Gleeble simulation, the effect of cooling rate and isothermal temperature on transformed microstructure were studied systematically. The microstructure and mechanical property of 55SiCrV、55SiCr hot rolling wire rod and heat treated steel wire were comparative studied by SEM and EBSD. The results indicated that the sorbite structure of 55SiCrV wire rod was finer than 55SiCr significantly and exhibited superior strength and plasticity; the microstructure of wire steel was mainly composed of tempered troostite, which showed tensile strength Rm above 2 110 MPa, reduction of area Z above 43%. The higher proportion of large angle grain boundaries and retained austenite were acquired with the indication of V, and both the strength and plasticity were enhanced synergistic, which was satisfied the performance requirement of 2 100 MPa grade suspension spring steel. This work provides theory basis for mass production of 2 100 MPa grade 55SiCrV suspension spring steel wire rods.
  • lnnovation and Interflowing
  • ZHOU Xikang, SONG Zejin, LI Biling
    Steel Rolling. 2026, 43(5): 135-139. https://doi.org/10.13228/j.boyuan.issn1003-9996.20260516
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    With the advancement of near-net-shape short-process hot rolling strip technology, coupled with the continuous market demand for high value-added steel grades such as advanced high-strength steel and non-oriented silicon steel, the varieties and dimensions of hot-rolled products substituting cold-rolled counterparts have become increasingly diversified and extreme. Conventional finishing lines can no longer meet the requirements for high product quality and high production throughput. This article provides an in-depth exposition of the core finishing processes for high value-added hot rolled thin wide strip. It comprehensively details the process layouts of various finishing lines, including skin pass and leveling line, skin pass and trimming line, trimming and tension-leveling line, trimming and skin pass and tension-leveling line. These finishing lines are arranged after thin strip casting-rolling line, thin slab casting and rolling line, and conventional hot rolled silicon steel line. Furthermore, it proposes finishing process solutions and configuration recommendations for high value-added strip product, such as advanced high strength steel and hot rolled non-oriented silicon steel etc. This serves as a comprehensive reference for steel enterprise users and process designers in the selection and design of relevant finishing line equipment.
  • WANG Junping, HAN Shudong, DONG Jianjun, WANG Tong, ZHANG Dingkun, LIU Guoliang
    Steel Rolling. 2026, 43(5): 140-145. https://doi.org/10.13228/j.boyuan.issn1003-9996.20260517
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    The 45 steel plates are conventionally produced by controlled rolling process. To reduce production costs, this paper adopts multi-pass continuous hot rolling process to produce 45 steel plates with thickness specifications of 12、25、30、45 mm. The microstructure and mechanical properties of these plates were tested and analyzed. The results show that the 45 steel plates produced by multi-pass continuous hot rolling have a microstructure of granular pearlite + reticular ferrite; the grain size of the 12-30 mm thickness plates averages 8-8.5 levels, and the grain size of the 45 mm thickness plate averages 7-7.5 levels. The grain size difference is small at 1/4 thickness and 1/2 thickness of the plate, and the overall distribution of the microstructure is uniform, without obvious mixed crystal phenomenon. According to the A method in the GB/T 10561—2023 standard for non-metallic inclusions detection, there are A-type (fine phase), C-type (coarse phase), and D-type (coarse phase) inclusions, with ratings of 0.5-1.0 levels. The minimum tensile strength value of the 45 steel plate is 639 MPa, exceeding the standard by 6.5%. The elongation margin of the 12-30 mm thickness plates is sufficient, with the smallest value exceeding the standard by 30.0%, and the elongation of the 45 mm plate is slightly lower, but exceeding the standard by 17.9%. The multi-pass continuous hot rolling process can relatively increase the rolling machine's output (multi-pass continuous hot rolling process rolls 11-12 pieces per hour; controlled rolling process rolls 9-10 pieces per hour) for plates with thickness specifications of 45 mm and below. For 45 steel with higher carbon content, using the controlled rolling low-temperature large reduction process will increase the risk of local cracking on the plate surface due to uneven deformation, reduce the yield rate, and increase energy consumption; while the multi-pass continuous hot rolling process reduces the reduction in each pass, promotes the uniformity of plastic deformation, ensures the plate shape, and refines the microstructure grains to improve the plate performance.
  • WANG Zhicong, XING Ruifang
    Steel Rolling. 2026, 43(5): 146-149. https://doi.org/10.13228/j.boyuan.issn1003-9996.20260518
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    Aiming at the technical requirements of 13MnNiMoR extra-heavy plates for pressure-bearing equipment in terms of strength, low-temperature toughness and high-temperature performance, this paper investigates the effects of two process routes, namely normalized rolling + accelerated cooling control + tempering (process A) and off-line normalizing + accelerated cooling control + tempering (process B), on the microstructure and properties of the plates. Through chemical composition design, the synergistic ratio of key alloying elements including C, Mn, Ni, Mo, Nb and V is optimized. By comprehensively adopting advanced manufacturing technologies such as continuous casting with dynamic soft reduction, differential temperature rolling, on-line quenching and off-line normalizing, 13MnNiMoR extra-heavy plates with thickness ranging from 80 mm to 140 mm are successfully fabricated. The research results show that the plates manufactured by both processes meet the standard requirements ofReL≥450 MPa,Rm≥610 MPa, and the KV2≥80 J of the plate thickness core at -20 ℃. After simulated post-weld heat treatment (PWHT) at 620 ℃ and holding 12 h, the yield strength attenuation rate of the plates is controlled within 6%, and the Z-direction reduction of area remains above 45%. High-temperature tensile tests reveal that the yield strength of the plates ranges from 390 MPa to 450 MPa under 400 ℃ service condition, which is remarkably higher than the relevant standard technical indicators. Each of the two manufacturing processes has its own merits and can be selected according to service conditions. Process A features lower cost, shorter production cycle and faster delivery, showing superior performance in mass production compared with process B. In contrast, process B delivers plates with more stable performance, finer grain size, slightly higher strength and better impact toughness, yet accompanied by a slightly longer production cycle. The four-dimensional regulation system established in this study provides reliable theoretical support for the efficient and low-cost industrial production of extra-heavy plates for pressure-bearing equipment.
  • MA Kai, XING Wei, WANG Zhongxuan, LINGHU Kezhi, XIAO Pengcheng, YANG Yang
    Steel Rolling. 2026, 43(5): 150-156. https://doi.org/10.13228/j.boyuan.issn1003-9996.20260519
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    To reduce the wear of backup rolls for the finishing mill in the 2 050 mm production line of Tangsteel HBIS Group, and increase its rolling kilometers and rolling tonnage, the chamfer and radius of backup rolls for F1-F4 stands were optimized in this paper. Based on the 3D finite element modeling, theinter-roll pressure between backup roll and work roll, strip stress, strip surface crown and roll gap shape were calculated for 10 working conditions with different roll shifting positions and bending forces for 1 400 mm-width strip steel. The results show that under identical working conditions, both the inter-roll pressure and strip stress decrease after backup roll profile optimization, while the strip crown control range and roll gap shape remain nearly unchanged. With the strip crown control range and roll gap shape maintained, the inter-roll pressure and strip edge stress are effectively alleviated after backup roll profile optimization. Under the same service load, the edge wear of the backup roll decreases from 0.15 mm to 0.07 mm, achieving remarkable improvement in edge wear performance. For F2-F4 stands, the rolling kilometers of backup rolls increase from 1 286 km, 1 328 km and 1 707 km to 1 994 km, 2 263 km and 3 018 km respectively during service.
  • SUN Yi, WANG Qingyun
    Steel Rolling. 2026, 43(5): 157-162. https://doi.org/10.13228/j.boyuan.issn1003-9996.20260520
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    In order to obtain hot forming heavy-duty autombile frame steel with excellent comprehensive performance, a pilot-scale production was carried out according to the set chemical composition and rolling process. Different heat treatment processes were applied to the transverse and longitudinal beams made of hot-rolled frame steel plates to explore the influence of different heat treatment processes on the microstructure and properties of the hot-formed frame steel. The microstructure of the hot-rolled heavy-duty automobile frame steel was banded ferrite + pearlite. Comparative tests were conducted using different heat treatment processes, bending tests, and different welding methods. However, problems such as shallow surface corrosion of the finished product, weld formation cracking, and low impact values were found. Therefore, the chemical composition and production process of the hot-formed heavy-duty truck frame steel were optimized. On the basis of the test chemical composition, the Si mass fraction was adjusted from 0.60% to 0.20%, and the Nb mass fraction was adjusted from 0.025% to 0.040%, while the content of other elements remained unchanged; the target temperature of the heating furnace was adjusted from 1 250 ℃ to 1 220 ℃, and the heating time was adjusted from 170 min to 150 min to reduce the over-oxidation of the cast billet in the heating furnace and improve the shallow corrosion problem on the surface of the steel plate; a heat treatment process of austenitizing at 900 ℃ for 30 min, water mist cooling to 250-350 ℃ and holding for 30 min, and laser welding process were adopted. A new generation of hot-formed heavy-duty automobile frame steel was successfully developed. This fram beam steel achieves an additional weight reduction of 12% compared with conventional high-strength beam steel. This study provides a reference for the development of similar products.
  • WU Junwei
    Steel Rolling. 2026, 43(5): 163-170. https://doi.org/10.13228/j.boyuan.issn1003-9996.20260521
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    To address the problems of a distinct demarcation line on the strip surface and significant color differences on both sides caused by the restart of a skin-pass mill after an unplanned shutdown during the production of Al-Si coated hot-stamping steel, this study systematically investigates the influence mechanism of the skin-passing process on coating surface morphology and elemental diffusion behavior. Through scanning electron microscopy, energy-dispersive spectroscopy, roughness testing, microhardness analysis, and neutral salt spray tests, the results show that skin passing (with a rolling force of 4 kN/mm) eliminates the aluminium flower defects on the cold strip surface, increasing the roughness Ra from 1.337 μm to 2.47 μm (an increase of 84.7%) and raising the peak count RPc by 48.8%. After hot stamping at 930 ℃, the higher surface roughness leads to intensified oxidation and a thicker oxide film, which induces a blue-light interference effect; meanwhile, skin passing effectively destroys the original high-density dendritic structure, thereby avoiding the non-uniform melting during hot stamping and significantly reducing the density of the network structure on the coating surface. The synergistic effect of the differences in surface micro-morphology and oxide film thickness is the fundamental reason for the colour difference between skin-passed and non-skin-passed strip strips in both the cold and hot-stamped states. Furthermore, skin-passing-induced coating densification and enhanced interfacial metallurgical bonding accelerate the interdiffusion of Fe, Al, and Si elements, increasing the diffusion layer thickness by 14.3% and promoting the formation of a gradient dual-layer intermetallic compound (FexAlySiz) structure in the skin-passed strip, whereas the non-skin-passed strip exhibits only a single layer. Skin passing also increases the microhardness of the substrate by 5.5%, but the martensite hardness tends to be consistent after hot stamping. Salt spray test results show that the skin-passed strips exhibit slightly improved corrosion resistance due to the thicker and more protective oxide film. The findings of this study provide a theoretical basis for optimising the production process of Al-Si coated hot-stamping steel, eliminating colour difference defects, and enhancing service performance.