20 December 2025, Volume 44 Issue 6

    

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Comprehensive Summarization
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  Bubble size and distribution: A review on refinement and dispersion in metallurgical processes

  XIAO Qi, WANG Lianyu, LIU Xiaoming, ZHU Fayuan, YANG Bin, WANG Qiang

  Continuous Casting. 2025, 44(6): 1-13. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250202

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  The size and distribution of bubbles play a crucial role in determining the efficiency of metallurgical processes and the quality of the resulting products. A common challenge in current practices is the formation of excessively large and poorly dispersed bubbles, which significantly restrict heat and mass transfer, reaction kinetics, and the removal of inclusions between molten metal and bubbles. This paper systematically reviews recent progress in the refinement and uniform dispersion of bubbles in metallurgical systems. Key techniques such as gas injection parameter control, forced bubble detachment, argon blowing via submerged entry nozzles, dissolved gas flotation, mechanical stirring, and high-shear methods are examined in terms of their underlying mechanisms and practical performance. The fundamental principle of bubble refinement involves enhancing turbulent flow in the liquid phase to facilitate bubble breakup and suppress coalescence. Owing to the limitations of contact-based approaches in high-temperature molten media, non-contact electromagnetic flow control has emerged as a promising alternative. By generating intense liquid turbulence through electromagnetic forces, this method enables effective bubble refinement and homogeneous dispersion, offering considerable potential for improving metal purity and process efficiency in metallurgical operations.
Monographic Study
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  Development on martensite stainless steel product by continuous casting based on precise solidification end reduction

  LAN Peng, ZHANG Liang, SU Dongqi, AN Jie, WANG Cheng, CHEN Deli, CHEN Xiuqiang, TANG Liang

  Continuous Casting. 2025, 44(6): 14-21. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250217

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  The finite difference model for 320 mm×410 mm continuously cast bloom of 1.4418 martensite stainless steel was established based on the equipment condition in a domestic factory, and it was verified by the shell thickness and surface temperature in the plant. The solidification characteristic and mechanical reduction reasonability in continuous casting of 1.4418 martensite stainless steel were discussed numerically, and the most suitable casting speed was found as 0.45 m/min. Two sets of mechanical reduction parameters were designed with total reduction amount of 12 mm and 15 mm, respectively. The industrial test was carried out according to the optimized schemes by numerical modelling, and the successful operation was achieved within the rated power range of withdraw units. The best center quality of the bloom for 1.4418 martensite stainless steel was obtained when the casting speed was 0.45 m/min with the designed reduction amount for No.2—5 withdraw units about 4 mm, 4 mm, 4 mm and 3 mm respectively, and the pass rate for the level A flaw detection was measured to be around 97%, satisfying the requirement of batch production and delivery.
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  Influence of static magnetic field on evolution behavior of non-metallic inclusion in a 00 Ni18Co8Mo5TiAl maraging steel

  WANG Tao, SONG Jintao, CHEN Lian, YUAN Yongbo, TIAN Chen, LIU Xiaoming, CHEN Chao, MU Wangzhong

  Continuous Casting. 2025, 44(6): 22-29. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250207

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  Maraging steel, as a representative ultra-high-strength steel, is highly sensitive to the influence of non-metallic inclusions on its mechanical properties. In this study, 00 Ni18Co8Mo5TiAl steel was selected as the material, and a steady static magnetic field was applied outside the insulated melt to regulate melt flow via the magnetic damping effect and thereby promote the aggregation and removal of inclusions. Systematic investigations on the types, sizes, and number densities of inclusions under different conditions were performed through the industrial sampling and remelting experiments. The obtained results show that the inclusions in industrial samples were mainly TiN and TiS with a small amount of Al₂O₃ and complex inclusions. Among the inclusions, TiN exhibited a number density of approximately 230 mm^-2 with an average size of 0.67 μm, while TiS had a number density of about 220 mm^-2 and an average size of 0.9 μm. Remelting experiments revealed that, compared with samples without magnetic field application, the inclusion number density decreases from 139 mm^-2 to 96 mm^-2, whereas the average size increases from 1.01 μm to 1.57 μm, with a significant reduction in TiS inclusions. Furthermore, Al₂O₃ enrichment on the surface becomes to be more pronounced under the magnetic field application. Mechanism analysis indicates that the static magnetic field suppresses melt convection, stabilizes the gas-liquid interface, and prolongs the interaction time between the melt and the atmosphere, thereby enhancing the removal of Al. Meanwhile, the magnetic damping effect restrains solute diffusion, reduces TiS nucleation, and facilitates the Ostwald ripening process. This leads to a decrease in inclusion number density but an increase in size. Theoretical calculations further indicate that both TiS and Ti₄C₂S₂ can stably precipitate in molten steel; however, when the sulfur content is below 0.002%, the precipitation of TiS is significantly suppressed.
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  Multiphysics prediction of electromagnetic stirring in a slab mold based on mechanistic model and large model

  HUANG Junjie, LU Haibiao, ZHONG Yunbo, REN Zhongming, LI Wei, CHEN Yongbiao, LEI Zuosheng

  Continuous Casting. 2025, 44(6): 30-43. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250219

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  The flow and heat transfer state of molten steel within the slab continuous casting mold is a critical factor determining the quality of the final slab. Utilizing artificial intelligence technology to achieve real-time, precise prediction and intelligent control of this complex multiphysics field is of great significance for improving the quality of high-end steel and promoting the intelligent transformation of the steel industry. To this end, this study first established a mechanistic model of molten steel flow, heat transfer, and solidification under electromagnetic stirring (EMS) in a slab continuous casting mold. Furthermore, a set of flow field evaluation criteria for the mold was proposed—namely, a steel-slag interface slag entrapment-freezing index, a shell uniformity index, and an inclusion removal index—with the aim of optimizing the EMS process. Secondly, based on the dataset of 3D flow and temperature fields generated by the aforementioned model, a large-scale multiphysics prediction model for the mold was developed using a deep neural network (DNN) architecture, enabling rapid prediction of the multiphysics field within the mold. The results show that, compared to traditional numerical simulation results, the prediction errors of the large model for the multiphysics fields, including the flow and temperature fields within the mold, are all within 10%. Meanwhile, the model′s computational speed was significantly increased, with the average computation time to obtain the multiphysics field within the mold being drastically reduced from the original 24 hours to 2 seconds. This research provides key technical support for achieving online optimization and closed-loop control of the EMS process and for the construction of a "Digital Twin" system.
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  Exploration on regulation law of flow field in slab mold by inserting baffle rods

  WANG Ruifeng, XIAO Pengcheng, LI Xiaoyang, ZHAO Chunbao, ZHU Liguang

  Continuous Casting. 2025, 44(6): 44-53. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250155

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  High-speed slab continuous casting can significantly improve production efficiency; however, severe fluctuations in liquid surface flow velocity under high casting speeds are prone to causing slag entrainment defects, and most conventional slab continuous casters are not equipped with electromagnetic braking systems. To explore a low-cost and high-efficiency flow field control method under high casting speeds, this study proposes a new approach: suppressing rapid liquid surface flow by inserting baffle rods. Using a combination of numerical simulation and physical water modeling, a 920 mm×180 mm mold model was established. With the diameter (30, 50, 70 mm) and insertion depth (10, 15 cm) of cylindrical refractory rods as variables, the regulation laws of cylindrical baffle rods on the liquid surface flow velocity and fluctuation in the mold were investigated.The results show that the diameter of the baffle rod plays a dominant role in regulating the mold flow field. Compared with the condition without a baffle rod, the 70 mm baffle rod reduces the overall flow velocity by 19.5%, which is 3.2 times the reduction rate of the 30 mm baffle rod (6.1%). The reduction in liquid surface fluctuation increases from 11% to 39%, a 3.5-fold improvement. The effect of insertion depth on the flow field exhibits a threshold effect: only when the diameter is no less than 50 mm, increasing the insertion depth to 15 cm can additionally reduce the flow velocity by 3.2%-5.4% and the fluctuation by 12.8%. For small-diameter rods (30 mm), increasing the depth has a weak regulatory effect.The optimal parameter combination in this study is a baffle rod with a diameter of 70 mm and an insertion depth of 15 cm. Under this condition, the maximum liquid surface velocity (at point P2) decreases to 0.2 m/s (a cumulative reduction of 17.7%), and the velocity in the central area (at point P4) decreases to 0.115 m/s (a reduction of 22.8%). The fluctuation value in the jet core area (at point P2) decreases to 0.21 cm (a reduction of 40.0%), and the fluctuation in the slag entrainment risk area (P2/P5) stabilizes at 0.21-0.23 cm.
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  Optimization design of electromagnetic stirrer for RH up-snorkel

  ZHANG Pan, WANG Lianyu, XIN Ziheng, LIU Xiaoming, YANG Bin, GU Maoqiang, WANG Qiang

  Continuous Casting. 2025, 44(6): 54-63. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250206

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  The flow behavior of molten steel in the Ruhrstahl-Heraeus (RH) furnace critically influences the efficiency of refining processes, including decarburization and impurity removal. While the widely employed gas-stirring technique effectively enhances molten steel circulation, the associated bubble flow is difficult to control precisely, potentially leading to flow instabilities and uneven energy distribution that limit further gains in refining efficiency. Therefore, in order to optimize the flow behavior within the RH furnace, this paper conducts an optimization simulation of the electromagnetic stirrer in the RH riser. The results show that the inner diameter of the iron core should be minimized to 750 mm to maximize the magnetic field strength; The outer diameter and thickness are optimized to 1 500 mm and 100 mm respectively, at which point the magnetic field performance and material cost are balanced; The stirrer is positioned 125 mm from the top to generate the maximum force. When the coil is 75 mm away from the molten steel, the magnetic field distribution of the iron core is the most uniform, without local magnetic concentration areas, and the magnetic field strength of the molten steel reaches a relatively high level; The simulation determines that 110 turns of coil, a frequency of 5 Hz, and an current below 250 A are the optimal combination, which can generate an average magnetic induction intensity of over 0.04 T and achieve the best matching of electromagnetic force and penetration depth. After coupling the optimized electromagnetic field into the flow field, the circulation flow increases by 6.3%, which proves the optimization effect of the electromagnetic stirrer. This study clearly defines a set of optimal three-phase six-level electromagnetic stirrer parameters for the RH riser when the inner diameter is 650 mm, providing theoretical basis and parameter guidance for its industrial design.
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  Simulation study on optimization of mold electromagnetic stirring for 82B high carbon steel billet

  JING Danyang, WANG Pu, XIA Shuaikang, MA Jianchao, LI Qiang, ZHOU Jian, ZHANG Jiaquan

  Continuous Casting. 2025, 44(6): 64-73. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250224

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  This study utilizes a low-Reynolds number k-ε turbulence model to construct a three-dimensional magnetohydrodynamic coupling numerical model, investigating the impact of electromagnetic stirring (EMS) current intensity and stirrer positioning on the flow, heat transfer, and solidification behavior of molten steel within the continuous casting mold for 140 mm×140 mm billets of 82B steel at a particular steel plant. The results demonstrate that the current intensity is a critical determinant of stirring efficacy; increasing the current intensity leads to a reduction in the depth of the primary steel jet impact, an increase in tangential velocity, and accelerated dissipation of superheat within the mold, resulting in a thinner solidified shell and a scouring effect on the shell due to backflow near the mold, which appears a slow growth zone in shell thickness. Variations in stirrer positioning also alter the flow field characteristics; the lower the position, the more the main flow core descends, and the position and shape of the vortex change accordingly, reducing liquid surface fluctuations, although an excessively high exit tangential velocity may lead to uneven shell growth. For the continuous casting production of high-carbon steel billets at this plant, it is beneficial to appropriately elevate the EMS installation to 515 mm and enhance the stirring current intensity to the rated 600 A. This configuration keeps the liquid surface fluctuations within a controllable range and further promotes rapid dissipation of superheated molten steel, while also ensuring a certain degree of undercooling at the center of the foot rolling area, facilitating early nucleation of molten steel and enhancing the ratio of equiaxed grains, which is advantageous for improving the center segregation of the billet.
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  Study on regulation of steel-slag interface in thin slab mold by electromagnetic brake

  ZHAO Lixin, SHI Jingpei, SUN Ligen, PIAO Zhanlong, ZHANG Caijun

  Continuous Casting. 2025, 44(6): 74-85. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250211

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  To address the issues of flow field turbulence and unstable steel-slag interface in the thin slab continuous casting mold under high casting speed conditions, this study takes the FTSC thin slab mold and full-width single-segment electromagnetic braking (Ruler-EMBr) system of a steel plant as the research objects. A coupled model of Large Eddy Simulation (LES) and Volume of Fluid (VOF) is adopted for numerical simulation, with a focus on analyzing the influence law of different magnetic flux densities on the flow characteristics in the mold when the casting speed is 6.0 m/min. The results show that electromagnetic braking can effectively regulate the flow field in the mold, improve the stability of the steel-slag interface, and prevent the abnormal rise of the steel-slag interface. When the Ruler-EMBr system is applied with a magnetic flux density of 0.23 T, the maximum velocity of the steel-slag interface is controlled within 0.30 m/s, the maximum wave height is limited to 10 mm, the fluctuation range of the interface position is maintained within ±2 mm, and the turbulent kinetic energy of the steel-slag interface is suppressed below 0.045 J/kg. These findings fully verify the flow field regulation effect of the Ruler-EMBr system.
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  Study on regulation mechanism of magnetic field on mold flux for ultra-high speed thin slab continuous casting

  WANG Xianglong, YANG Lidong, XIAO Pengcheng, ZHU Liguang

  Continuous Casting. 2025, 44(6): 86-92. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250177

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  In the context of the global "dual carbon" strategy, ultra-high speed thin slab continuous casting has become a key technology for the green transformation of the iron and steel industry, owing to its significant advantages in energy saving, emission reduction, and product quality. However, high casting speeds (6-8 m/min) lead to issues such as unstable molten steel flow and inadequate lubrication by mold flux, which hinder further development. Although electromagnetic braking (EMBr) technology can suppress molten steel turbulence through applied magnetic fields, its specific effects on mold flux properties remain unclear. This study systematically investigates the evolution of physicochemical properties of ultra-high speed thin slab mold flux under magnetic fields. The results indicate that a mold flux with a basicity (R) of 1.67, viscosity of 0.22 Pa·s, melting point of 1 042 ℃, and a Na₂O-Li₂O-F flux system exhibits excellent process adaptability, meeting the requirements of rapid melting and uniform lubrication at high casting speeds. Under a magnetic field intensity ranging from 0 to 90 mT, the crystallization behavior of the mold flux is significantly influenced: increasing magnetic field strength advances nucleation time, prolongs the crystallization interval, inhibits crystal growth, and increases solidification volume expansion by 23%. Microstructural analysis reveals that the magnetic field promotes preferential growth of the Ca_0.87Mn_0.19Mg_0.94Si₂O₆ phase, increasing its proportion by 5.2%, and induces a transition in the silicate network from a disordered to an ordered structure. Water quenching experiments combined with XRD and Raman spectroscopy confirm that the magnetic field alters solute transport by suppressing melt flow, thereby regulating the solidification shrinkage behavior and microstructure of the mold flux. This study reveals, for the first time, the performance evolution mechanism of ultra-high speed casting mold flux under an electromagnetic field, providing a theoretical basis for developing mold fluxes compatible with EMBr technology and contributing to the industrial application of ultra-high speed continuous casting.
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  Numerical study on bubble refinement via periodically alternating electromagnetic stirring in molten steel

  DONG Xiao, WANG Lianyu, LIU Zeyi, WU Chunkun, ZHAO Qiyan, LIU Xiaoming, YANG Bin, WANG Qiang

  Continuous Casting. 2025, 44(6): 93-105. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250203

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  The size of bubbles directly influences the heat, mass, and momentum transfer processes between the bubbles and molten steel. The complexity of metallurgical processes and the high-temperature environment limit the application of conventional bubble refinement methods, resulting in generally large bubble sizes in molten steel, which severely restricts the production efficiency of metallurgical processes. This study proposes the periodically bidirectional rotating electromagnetic field to induce high-intensity turbulent flow in molten steel periodically, thereby achieving bubble refinement. Using numerical simulation methods, the turbulence intensity of molten steel under electromagnetic fields with different magnetic flux densities was investigated to determine the magnetic flux density suitable for bubble refinement. When the magnetic flux density increased to 240 mT, the turbulent flow of molten steel met the requirements for bubble breakup. The effect of the periodically bidirectional rotating electromagnetic field on the turbulent flow of molten steel was analyzed, and the bubble refinement effectiveness was examined. The proportion of large bubbles larger than 10 mm in the molten steel decreased to 3.09%, a reduction of 27.47% compared to conditions without the electromagnetic field. The number density proportion of bubbles in the 0.5-1 mm diameter range reached 40.03%, and the proportion of bubbles smaller than 5 mm was as high as 92.10%, an increase of 80.25% compared to conditions without the electromagnetic field. The turbulence intensity of molten steel under electromagnetic fields with different rotation periods and the corresponding bubble refinement effects were compared, with the optimal rotation period range identified as 3-5 s.
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  Influence of swirling flow nozzle on flow pattern in slab continuous casting mold based on physical simulation

  HAN Baoying, JIA Kanghui, MU Lixuan

  Continuous Casting. 2025, 44(6): 106-114. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250209

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  To investigate the effect of electromagnetic swirling flow in the nozzle (EMSFN) technology on the molten steel flow behavior in a slab continuous casting mold, a water model system with a geometric scaling ratio of 3∶1 was established based on similarity criteria, using a slab mold (1 450 mm×200 mm) as the prototype. A mechanical swirling rotor was installed inside the submerged entry nozzle to simulate the external field intervention effect of EMSFN. The influence of the nozzle swirling flow on the fluid flow pattern, liquid level fluctuation, and velocity distribution within the mold under different outlet flow rates of water model system was systematically studied. The results show that under conventional casting conditions, the flow field in the mold is asymmetrically distributed, with interfering upward flow occurring in the lower recirculation zone. The liquid level fluctuation intensified with increasing outlet flow rate, exceeding ±2 mm near the nozzle. After applying the nozzle swirling flow, the flow field symmetry was significantly improved. The impingement point of the nozzle outflow on the narrow face shifted upward, effectively dissipating the kinetic energy of the lower flow and suppressing the lower vortex, thereby stabilizing the liquid level fluctuation within ±1 mm. This study confirms that applying nozzle swirling flow enables effective control of the mold flow field, which provides a theoretical basis for the industrial application of EMSFN technology in slab continuous casting.
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  Optimization study on secondary cooling water distribution for high-speed continuous casting of IF steel slab

  LIU Zhongtian, LI Yang, CHENG Changgui, QIN Xufeng, LIU Liang, CHEN Hao, HUANG Xingyu

  Continuous Casting. 2025, 44(6): 115-120. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250210

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  An improper secondary cooling regime in slab continuous casting can lead to issues including slab bulging, slab stalling, mold level fluctuations, and even breakouts resulting from longitudinal cracking or slag entrapment. This paper has focused on the high casting speed continuous casting process of IF steel slabs at a domestic steel plant. A two-dimensional unsteady heat transfer model was developed and calibrated using results from nail shooting experiments. The solidification and heat transfer behavior of IF steel slabs under various water distribution patterns were analyzed, and an optimized cooling strategy was proposed. Calculation results indicate that when the water distribution scheme derived from the on-site thermal tracking model was applied in production trials, the solidification end point predicted by the two-dimensional unsteady model shifted further downstream with increasing casting speed compared to that predicted by the on-site model. This deviation is consistent with the intensified red-hot slab observed in practice, indicating an increased risk of slab bulging. Therefore, to meet both the temperature requirements in the straightening zone and the suitable position for the soft reduction process, it is recommended to increase the water flow in secondary cooling zones 5-8 by a factor of 1.25 while maintaining the original water flow in zones 9-10 when the casting speed is increased.
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  Simulation study on heat transfer and flow in induction-heated tundish under influence of ladle heat dissipation

  LIU Ze, JIANG Tianye, LI Yang, XIONG Qiaoling, GUAN Rui, AI Xingang, ZENG Hongbo

  Continuous Casting. 2025, 44(6): 121-131. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250189

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  Based on a finite element model, the magnetic induction intensity and Joule heat obtained from Maxwell were imported into Fluent as source terms to investigate the flow field and temperature field of molten steel in a five-strand four-channel induction heating tundish under the influence of ladle heat dissipation. The results show that, during the casting process, the temperatures at the three outlets of the tundish without ladle heat dissipation decrease slowly and exhibit a similar trend, with a temperature drop of less than 1 K among the outlets. In contrast, under the influence of ladle heat dissipation, the temperatures at the three outlets differ significantly, with a temperature difference of nearly 20 K between the early and late stages of casting. Although induction heating compensates for the temperature loss of molten steel in the ladle, it does not significantly reduce the temperature variation across different casting periods. The maximum outlet temperature is 11 K lower than the initial casting temperature. When the induction heating power is adjusted during casting, the maximum temperature difference between different time points remains within 2 K, and the temperatures remain relatively consistent across different periods and outlets.
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  Numerical simulation on multi-physical field transport behavior during continuous casting of 55SiCrA spring steel bloom

  YANG Jianhua, CUI Henan, GAO Jianwen, WANG Huisheng, CHEN Jun, WANG Chao, XU Zhida, LIU Qing

  Continuous Casting. 2025, 44(6): 132-144. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250098

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  The production of high-strength and high-toughness spring steel is a key component in the lightweight development trend of the automotive industry. To address the issue of significant macrosegregation control in the continuous casting of 55SiCrA spring steel, this study develops a coupled multi-physics numerical model integrating "flow-heat transfer-electromagnetic field-solute transport" for the actual industrial continuous casting process of 280 mm×280 mm spring steel blooms. The accuracy of the solute field predicted by the model was verified through industrial-scale sampling. Furthermore, the effects of submerged entry nozzle (SEN) structure, casting superheat, and mold electromagnetic stirring (M-EMS) on solute transport during continuous casting were systematically investigated. The results indicate that the SEN structure significantly influences molten steel flow and solute transport behavior. The use of a four-port nozzle reduces the severity of negative segregation under bloom surface and eliminates its asymmetry. Increasing the superheat prolongs solute precipitation and transport at the solidification front, thereby intensifying negative segregation under bloom surface. M-EMS enhances molten steel turbulence and accelerates heat dissipation, which helps mitigate the original negative segregation; however, it also increases the scouring effect at the solidification front, potentially leading to the formation of a secondary negative segregation band within the mushy zone.
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  Research on mechanism of microstructure refinement and toughening of Al-Si alloys based on parameter optimization of traveling wave magnetic field

  GUO Zixia, ZHOU Ye, LIU Siyao, ZHAO Jiyu, MIAO Xincheng, LI Shengli

  Continuous Casting. 2025, 44(6): 145-152. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250054

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  This study investigates the effects of the upward traveling wave magnetic field (TMF) operating at different frequencies on the solidification process, microstructure refinement, and mechanical properties of an Al-7wt.% Si binary alloy. The alloy solidification samples were prepared using an electromagnetic casting device. A magnetic-flow-thermal multi-field coupling model was employed for numerical simulation of the melt solidification process, calculating the forced convection and liquid phase distribution within the Al-7 wt.% Si alloy melt subjected to TMF treatment. The results indicate that under 75 A 12 Hz-TMF, the peak velocity of the flow field within the Al-7 wt.% Si alloy melt reached 0.023 m/s. Under the combined effects of forced convection and Joule heating, the dendrite arm spacing (DAS) of the samples treated at 8 Hz-TMF was refined to 127.8 μm. Meanwhile, the ultimate tensile strength and elongation after fracture increased from 100.8 MPa and 6.9% (natural solidification, NMF) to 113.7 MPa and 8.3%. When the TMF frequency was increased to 12 Hz, the Joule heating generated within the melt gradually increased, leading to a reduction in the temperature gradient during the solidification process, thereby slowing down the solidification rate of the castings, and the refinement effect on the solidification structure decreased, with the average DAS increasing to 140.3 μm, and the mechanical properties consequently degraded. The results demonstrate that the convection induced by TMF and Joule heating are the primary reasons for the refinement of the solidification microstructure and the enhancement of mechanical properties. These findings provide a theoretical basis for the research on improving the quality and mechanical properties of castings through applied electromagnetic field casting technology.
Technology Exchange
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  Research on optimization of continuous casting plugging process for billets and intelligent anti-leakage steel technology

  LI Boyi, ZHONG Wei, CHEN Siyang, LIU Nanlü, YANG Lingzhi

  Continuous Casting. 2025, 44(6): 153-160. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250213

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  The withdrawal-induced leakage of molten steel from the dummy bar head during the start-up phase of billet continuous casting is a major constraint on production continuity and equipment safety. This issue stems from systematic shortcomings in conventional dummy bar practices, including the design of the dummy bar head, cold charge parameters, auxiliary equipment, and monitoring and control mechanisms. In response, this paper introduces an integrated plug-pulling process that combines multi-dimensional innovations in the dummy bar head design, intelligent and precise regulation of cold charge parameters, development of new auxiliary devices, and smart adaptive monitoring and control. Industrial trials confirm that the proposed approach reduces the monthly average number of leakage incidents caused by dummy bar withdrawal from 8 to 2, increases the monthly average mold casting capacity by 32.8%, and decreases the current fluctuation amplitude of the withdrawal-straightening motor by 40%. By enabling intelligent monitoring and adaptive control, the start-up casting process has been transformed from an experience-driven, reactive operation into a data-driven, proactive prevention system. This provides comprehensive technical support for high-efficiency and safe billet continuous casting.
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  Internal quality of GCr15 bearing steel continuous casting billet is improved based on pressing technology

  WANG Haida, CHEN Lie, ZHANG Yanan, ZHANG Guotao, FAN Shiqiang

  Continuous Casting. 2025, 44(6): 161-169. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250215

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  To address center segregation and shrinkage cavities in GCr15 bearing steel continuous casting billets, a steel plant established a solidification heat transfer model for large billets by integrating principles of heat transfer, steel grade characteristics, and the spatial structure of the withdrawal and straightening equipment, employing the finite difference method. Leveraging the accuracy of this model, a final-stage reduction technology was developed and implemented on a seven-stand withdrawal and straightening system with 1 200 mm equal roller spacing, achieving safe and stable production with a total reduction of 22 mm. With this technology, the center carbon segregation index of high-carbon steel billets has been consistently maintained within 0.95-1.05, the proportion of billets with a carbon extreme deviation not exceeding 0.08% has increased to 98.4%, and 99.95% of billets now exhibit center shrinkage cavities of grade 0.5 or lower. This breakthrough enhancement in internal billet quality has enabled the plant to adopt a low compression ratio rolling process for producing large-size bars, which achieve an ultrasonic testing pass rate exceeding 99.95% in accordance with the AA grade of GB/T 4162.
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  Effect of strand electromagnetic stirring position on fluid flow and heat transfer in large-size round billet molten steel

  FEI Yue, XU Changjun, WANG Tao, WANG Yaogong, LIU Ningning, LIU Linfei

  Continuous Casting. 2025, 44(6): 170-178. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250208

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  The effect of stand electromagnetic stirring on the fluid flow and heat transfer behavior of molten steel during continuous casting of ø800 mm round billet was investigated. The results indicate that the stirring position has an important influence on the flow state, flow direction, stirred volume, and cooling rate in the molten steel. Within the strand zone, lowering the stirring position reduces the angle between the radio flow direction of the solidification front from 30° to 0°, while the helical angel of the longitudinal flow trajectory increases from 30° to 55°. The flow tendency toward the core weakened, and the stirring velocity at the solidification front decreased from 0.008 m/s to 0.003 6 m/s. Among them, when the stirrer is located in the upper-middle section of the CET zone, the flow stability of the molten steel is significantly improved. The stirring speed at the solidification front is 0.005 6 m/s, and the effective stirring volume of molten steel is the largest, which is 0.045 3 m³, with a tendency to flow to the core. In terms of heat transfer, the heat loss of molten steel in the stirring zone is faster. When the stirring is in the upper-middle section of the CET zone, it is beneficial to improve the equiaxed crystal rate and accelerate the solidification rate of the billet. Therefore, the stand electromagnetic stirring position in the upper-middle section of the CET zone is the best, which provides an important guiding significance for the optimization of the electromagnetic stirring process.