20 June 2025, Volume 44 Issue 3

    

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MonographicStudy
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  Impact stress distribution behavior of tundish dam

  ZHAO Chaofa, LI Yang, CHENG Changgui, QIN Xufeng, JIANG Zilong, HUANG Xingyu

  Continuous Casting. 2025, 44(3): 1-10. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240220

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  To address the significant erosion observed in the tundish dam with jet hole, a 65 t billet tundish from a domestic steel plant is researched. It employs numerical simulation to examine the distribution of impact stress on the upstream surface of the dam. The findings clarify the factors affecting the impact stress on tundish dam. Results indicate that the impact stress along the upper edge of the upstream surface is negative. Additionally, a specific impact stress exists at the lower section of the central axis, with peak stress recorded around the jet hole. The peak impact stress on the dam’s upstream surface exhibits a positive correlation with increasing casting speed. Variations in the distance between the weir and long nozzle show minimal effects on the peak impact stress, yet significantly alter the stress distribution around the jet hole. The impact stress distribution shows non-uniform characteristics at 1 400 mm, but demonstrates significantly improved uniformity at 1 800 mm.
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  Thermal simulation of growth of austenite grains in surface layer of microalloyed steel slab

  CHEN Xiang, WANG Yingchun, XIANG Junliang, YUAN Huazhi, ZHONG Honggang, ZHAI Qijie

  Continuous Casting. 2025, 44(3): 11-19. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240207

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  Abnormal large austenite grains are considered a significant cause of transverse cracks in continuous cast billets. Thermal simulation methods combined with in-situ liquid quenching experiments are employed to investigate the growth process of surface austenite grains in nine types of microalloyed steel during the bending-type continuous casting process. Results show that at the straightening starting point, where corner transverse crack defects are likely to occur, the size of abnormally coarse austenite grains increases with rising austenite start growth temperature T_γ, exhibiting an extremum near the peritectic point. As the absolute difference |ΔT| between T_γ and the precipitation temperature of TiN increases monotonically, it indicates that the austenite start growth temperature and the TiN precipitation temperature are key factors influencing abnormal austenite growth. High-temperature tensile tests demonstrate that steels with higher austenite start growth temperatures and larger |ΔT| show greater crack sensitivity, which is consistent with the pattern of abnormal austenite growth.
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  Quality defect prediction of continuous casting billet based on multi-task learning

  LIU Yan, SUN Menglei, CHEN Songlu, YANG Siqi, ZHANG Xiaofeng, GONG Jinpeng

  Continuous Casting. 2025, 44(3): 20-28. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240120

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  In the steel continuous casting process, center porosity and shrinkage cavity are two common quality defects that can significantly affect product performance. Accurately predicting these defects is essential, as it not only avoids destructive testing but also supports technicians in adjusting process parameters, thereby ensuring the smooth progression of subsequent rolling operations. However, due to the nonlinear dynamics, strong coupling characteristics, and multiple external disturbances inherent in the continuous casting process, predicting center porosity and shrinkage cavity levels remains highly challenging. Existing approaches typically rely on single-task learning, which limits their ability to predict multiple defects simultaneously. This constraint not only reduces prediction efficiency but also often results in suboptimal accuracy that fails to meet production requirements. To overcome these limitations, this study proposes a novel defect prediction method based on a multi-task learning framework, which integrates multi-task learning with the TabNet deep learning model designed for tabular data. This approach enables simultaneous prediction of both center porosity and shrinkage cavity levels by leveraging the intrinsic relationship between the two defects, thereby improving both efficiency and predictive accuracy. Extensive experiments using real-world production data from a steel plant demonstrate that the proposed method achieves outstanding performance in industrial defect prediction, with prediction accuracies of 100% for center porosity and 99.9% for shrinkage cavity, and a 53.47% reduction in inference time, fully validating the effectiveness and practical value of the proposed multi-task learning strategy.
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  Reliability analysis of ladle turret bearing considering bolt pretightening force

  GUO Yuanyuan, YIN Xiaochun, DING huaiping, WENG Panpan

  Continuous Casting. 2025, 44(3): 29-36. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240215

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  Rotary bearing is an important structural component in the ladle turret of continuous casting equipment, and its safety is very important in the production process. Therefore, the reliability of rotary bearing is analyzed by three dimensional (3D) finite element analysis method. To this end, the 3D finite element analysis model of the whole ladle turret is established by using HyperMesh software and ANSYS software, in which the flange connection system between the rotary bearing and the upper and lower cylinder is modeled in detail by solid elements, and the pretightening force of the bolt in the flange connection system is considered by the pretension elements. The consideration of bolt pretightening force makes the simulation of rotary bearing to be more close to the actual circumstances. Given that abnormal wear of the rotary bearing caused by the offset load, the stress state and deformation state of the rotary bearing and bolt and the contact status of the contact surface in the rotary bearing and flange are studied under the limit single-arm loading condition based on the static finite element analysis, which can provide theoretical basis for the wear analysis and safety evaluation of the rotary bearing of ladle turret.
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  Influence of long nozzle parameters on unsteady pouring process oftundish with water model

  LI Xilu, LIU Peng, YANG Jun, YAO Yuchao, LIU Zhongqiu

  Continuous Casting. 2025, 44(3): 37-45. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240216

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  As an important operation procedure in continuous casting process, tundish casting can be divided into two stages: steady casting and unsteady casting. Although the unsteady casting process is short, the pollution caused by the process is often the most serious. In order to reduce the pollution of molten steel during the unsteady and steady casting process and improve the quality of liquid steel, the parameters in tundish were optimized better, and a second-flow tundish water model with geometric similarity ratio of 1∶4 was established. The tracer experiment, residence time distribution (RTD) experiment and three-phase cold water model experiment were carried out respectively. The effects of insertion depth and filling flow rate on the flow pattern, mixing characteristics and the evolution of slag-steel interface were analyzed. Experimental results from steady casting tests demonstrate that both the average residence time and dead zone volume fraction decrease with increasing flow rate at the long nozzle. Additionally, increasing the insertion depth of the long nozzle extends the average residence time of liquid steel from 226 to 246 s. In the unsteady casting test, it is found that the slag layer will appear in the filling process, that is, the slag eye will appear around the long water outlet, and the slag eye will not disappear immediately after the filling of the stable stage. The increase of the filling flow rate and the insertion depth of the long water outlet will lead to the increase of the area of the slag eye and the increase of the appearance time of the slag eye in the re-stability stage. When the insertion depth of the long water outlet is 90 mm, the charging flow rate increased from 2.18 to 3.30 m³/h, the maximum slag hole area increased from 1 871 to 19 001 mm², and the existence time of the re-stable slag hole also increased from 41 to 232 s. Considering the overall performance during the pouring stage, a long nozzle insertion depth of 90 mm demonstrates optimal performance.
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  Interface behavior of TiC with different mold fluxes for high Ti-bearing stainless steel

  YU Binqi, CHEN Zhuo, ZHANG Jiajing, LI Xiting, MA Jianchao, LI Qiang

  Continuous Casting. 2025, 44(3): 46-52. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240203

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  Ti-bearing steel in continuous casting process exists serious problems such as nozzle clogging and steel slag reaction. The interface behavior of mold flux with different basicity on TiC substrates were investigated by the sessile drop method, which can provide a theoretical basis for optimizing the composition of the mold flux for Ti-bearing steel. Firstly, the evolution law of wetting behavior with temperature in the contact process between mold flux and TiC was analyzed. As the increase of the basicity of mold flux, the wettability between mold flux and TiC substrate gradually decreased, and the contact angle was CS slag(CaO-SiO₂, 19.8°)>CSA slag(CaO-SiO₂-Al₂O₃, 20.9°)>CA slag(CaO-Al₂O₃, 31.5°). The results show that there is no interfacial reaction behavior between the mold flux and the TiC, but there is a mass transfer process between the two interfacial phases. The basicity of mold flux is an important factor affecting the mass transfer process between mold flux and TiC interface, and the increase of basicity can inhibit the mass transfer process. The SEM-EDS analysis results show that the interaction layer between CS slag and TiC inclusion is the thickest, about 30-80 μm, and the absorption capacity of CS slag to TiC inclusion is the strongest. On the contrary, the interaction layer between CA slag and TiC inclusion is the thinnest, about 30-50 μm, and the absorption capacity of CA slag to TiC inclusion is the worst.
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  Analysis and simulation optimization of dynamic operation process of steelmaking section interface

  DAI Yuxiang, ZENG Jiaqing, LIN Lu, HE Qing, CUI Huaizhou

  Continuous Casting. 2025, 44(3): 53-66. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240195

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  The production and scheduling of iron and steel enterprises constitute a complex system problem, involving multi-objective, multi-constraint dynamic control. Optimizing this process requires not only enhancing the functional efficiency of individual metallurgical processes to accelerate production rhythms but also ensuring coordination and flexible control between interconnected processes. The production time parameters of steelmaking and continuous casting process in a 200 t production line of a factory were analyzed. A simulation model was established with the help of Anylogic software, and the simulation parameters were set according to the actual situation. The changes of the shelf time and the process time of the entire steelmaking interval were studied when the production cycle of the process changed. The large fluctuation of steel grade transfer time is caused by the inconsistency of the whole process rhythm and the conflict of production capacity before and after the process. The production rhythm before and after the process does not match, and the shortening of the processing time of a single process will lead to the increase of the transfer time between the processes, and will not shorten the total time of the entire process. Based on the simulation results, the target of 35 min production for each process is proposed. Through process optimization and system matching, the total processing time was significantly reduced. For SPHC steel, the average runtime of the RH straight-up route (from KR to the end of continuous casting) was reduced to 149.2 min, marking a 47 min (24.0%) decrease compared to pre-optimization levels. The average running time of SPHC steel LF straight up path from KR to the end of continuous casting is 164.4 min, which is 18.8 min (10.3%) lower than before.
TechnologyExchange
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  Infrared image recognition-based casting slab surface temperature monitoring and secondary cooling water leakage alarm system

  DING Changjiang, ZHANG Cheng, WANG Guocai, YIN Ping, GAO Zhenbo, WU Haibin, ZHANG Lewen, LI Zimu

  Continuous Casting. 2025, 44(3): 67-71. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240237

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  In the continuous casting process, numerous factors influence product quality, among which the temperature control of steel billets is particularly critical. Excessively high temperatures can cause surface oxidation of billets, leading to resource waste, while excessively low temperatures can reduce billet plasticity. The secondary cooling zone regulates strand temperature in continuous casting via water spray systems, with spray intensity being the dominant control parameter for surface temperature. Malfunctions in the cooling water system, improper operation by on-site personnel, or delayed maintenance can sometimes affect the spray volume of the secondary cooling nozzles, leading to water leakage. Such leakage leads to excessive water accumulation in localized regions of the strand, inducing severe localized cooling that generates thermal stresses sufficient to cause cracking defects. This paper employs infrared imaging, utilizing machine vision and a water leakage detection algorithm to separate foreground objects from the background in video streams, enabling precise identification of water leakage in spray equipment. Experimental results demonstrate that this method effectively detects leakage areas in secondary cooling nozzles, achieving a 100% alarm accuracy rate during testing, thereby providing technical support for subsequent maintenance.
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  Effect of rare earth Ce on solidification structure and inclusion of 20MnTiB cold heading steel

  ZHANG Yingjia, MAO Wangwang, YU Yanchong, ZHANG Leru, YAN Wei

  Continuous Casting. 2025, 44(3): 72-79. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240239

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  The effects of rare earth Ce on the solidification structure and inclusion of 20MnTiB steel were investigated in the actual production process of domestic steel plant, taking 160 mm×160 mm 20MnTiB low-alloy cold heading steel continuous casting billet as the research object. The results show that the addition of 0.0027% Ce significantly refines the low-fold solidified tissue of 20MnTiB continuous casting billet, and the percentage of its central equiaxed zone increases from 16.8% to 20.8%. The addition of Ce reduces the solidification super-cooling degree, and provides more nucleation sites for solidification, and enlarges the percentage of the equiaxed zone of the solidified tissue. The results of SEM-EDS show that Ce modifies inclusions and the lattice mismatch between Ce and nucleation phases, and the results indicate that Ce modifies inclusions to refine the solidified tissue of the steel. EDS results show that the addition of Ce modifies the irregularly shaped Al₂O₃-CaO-MgO-CaS liquid composite inclusions into spherical CeAlO₃-CaO-MgO-CaS composite inclusions. After two-dimensional mismatch degree theoretical calculations, it can be seen that CeAlO₃ can be used as a heterogeneous nucleation core to refine the solidification structure during the solidification process of 20MnTiB steel.
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  Fluid flow control in tundish for super large round bloom casting

  BAI Yun, FENG Wenwen, CHEN Xiqing, XIAO Hong, WANG Pu, ZHANG Jiaquan

  Continuous Casting. 2025, 44(3): 80-90. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240131

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  The fluid flow and temperature of molten steel in tundish play a key role in its metallurgical performance, in which the difference between each strand will be magnified due to increasing strand spacing for the production of large-sized casting formats. A three-strand asymmetric tundish used for producing super large section round blooms with diameters over 1 200 mm in a steel plant was focused on. Aiming at the poor consistency of each strand caused by the large strand spacing, the flow behavior, temperature distribution and inclusion removal behavior of molten steel in the tundish with different retaining wall structures and dam combinations were studied by physical and numerical simulation. The results show that the short-circuit flow at out 2 of the prototype tundish can be effectively improved by setting U-shaped retaining walls and dams near strands No.1 and No.3 as compared with the prototype structure, and the ratio of dead zone can be reduced by 15.84%, and the standard deviation of mean residence time can be reduced by 107.1 s, and the maximum temperature difference can be decreased to 0.5 K, and the consistency of each strand can be improved significantly, and the average removal rate of inclusions increased by 10.86%. Thus, the optimized structure proposed in this study effectively enhances the steady-state metallurgical behavior of the asymmetric three-strand tundish utilized in continuous casting of super large cross-section round blooms, thereby improving its overall metallurgical
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  Distribution and mechanism of TiN inclusions in hot formed steel castings

  LI Yanjie, LI Zhe, CHENG Cuihua, ZHANG Dayong, JIA Ning, LI Hongbin, ZHANG Yan

  Continuous Casting. 2025, 44(3): 91-98. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240167

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  Ti microalloyed hot formed steel continuous casting slab was studied as the research object. The morphology of large-sized TiN in the slab samples was observed through SEM,EDS,OM,and other methods. It was found that there were TiN inclusions in the slab samples at the scale of tens of micrometers,which were different from the conventional rectangular block structure, exhibited strip, dendritic, irregular block shaped morphology. For the first time,Aspex was used to conduct microscopic scanning statistical analysis on different positions in the thickness direction of hot-formed steel slab. It was found that the distribution of large-sized TiN inclusions has obvious regularity,and the surface density and size of TiN from the slab surface to the solidification center show an increasing trend. By using the phase method to confirm the original austenite grain boundaries,it was found that TiN inclusions precipitated both at the original austenite grain boundaries and within the grains,and their morphology and particle size showed no obvious regularity. At the same time,based on the TiN activity product and related action coefficients, more accurate thermodynamic calculations were conducted on the dynamic activity product of solid-liquid two-phase solidification front,confirming that TiN inclusions in hot-formed slab precipitate in the two-phase zone,and elaborating on the relevant reason of TiN inclusion distribution law in detail.
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  Influencing factors and prevention measures of slab continuous casting bonded steel leakage

  WANG Rongrong, WANG Min, NIAN Baoguo, YANG Hao, GAO Yu, ZHAO Jianqi

  Continuous Casting. 2025, 44(3): 99-107. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240163

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  Continuous casting is one of the most critical processes in steelmaking. The occurrence of breakouts during continuous casting is influenced by multiple factors, with sticker-type breakouts being the most prevalent, accounting for approximately 70% of all breakout incidents. Breakout accidents in continuous casting can lead to molten steel leakage, posing severe safety hazards such as scalding, fires, and even explosions. These incidents may result in casualties and significant property damage. In view of the above difficulties, the factors influencing the bonded steel leakage of continuous casting from the process parameters of continuous casting production are systematically sorted out and the influence of slab size, casting speed, cooling water and heat flow on the bonded steel leakage of slabs are analyzed. The analysis of bonding in slabs with different widths (1 350, 1 500 and 1 550 mm) shows that the average heat flow fluctuates most significantly in the 1 550 mm thickness slab, and as the slab width increases, the fluctuation in average heat flow becomes more pronounced, leading to a higher likelihood of slab bonding. And for slabs with large wide surface sizes, a reasonable drawing speed should be selected during production to avoid the occurrence of bonding accidents. Finally, preventive measures are proposed to avoid bonded steel leakage, addressing process parameters, personnel operations, and management systems. These recommendations provide theoretical and technical support for the safe production of continuous casting.
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  Construction and quality optimization practice of secondary cooling model for high-speed small square billet continuous casting

  ZHANG Gengyu, LIU Qiang, KONG Yiwen, HAN Zhiwei

  Continuous Casting. 2025, 44(3): 108-113. https://doi.org/10.13228/j.boyuan.issn1005-4006.20250058

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  For the continuous casting of high-speed small square billets, a solidification heat transfer model was constructed. A dual-mode water spray control algorithm based on the target surface temperature and effective casting speed was proposed, and front-end and back-end applications with a B/S architecture were developed using JAVA and VUE. This model was applied to the production of HRB400 steel grade on a 170 mm × 170 mm square billet continuous caster for practical verification. After application, the low magnification quality of the billets was significantly improved. The proportion of central segregation better than grade 1.5 increased by 3.5%, and the proportion of central porosity better than grade 1.0 increased by 1.2%.
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  Analysis and application of mold oscillation for high-speed continuous casting of conventional low carbon steel slab

  GUO Yintao, JIA Lihui

  Continuous Casting. 2025, 44(3): 114-122. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240211

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  High speed continuous casting is the main driving force for the continuous development of contemporary casting technology, and it is also an effective way to improve the efficiency of steelmaking production lines and achieve cost reduction and benefit improvement. Insufficient lubrication of the shell inside the mold is one of the main obstacles hindering the further increasement of casting speed. To achieve the ideal oscillation effect, the influence of amplitude, oscillation frequency and deflection rate on the process effect of mold oscillation, such as the demolding and healing of the primary shell in the mold, the frictional stress applied to the primary shell, mold slag consumption, and the vibration impact, was conducted by theoretical calculation. A non-sinusoidal oscillation parameter with lower vibration impact was designed for resolving the main contradiction of insufficient lubrication for low carbon steel at high casting speed. The non-sinusoidal oscillation parameter has lower oscillation frequency, higher amplitude, and a deflection rate of 0.2. It was shown that the oscillation parameter increased mold slag consumption by about 15%, although the oscillation mark depth was deepened by 70 μm. The oscillation parameter can significantly improve the lubrication effect. By using the non-sinusoidal oscillation parameter, the casting speed of conventional continuous casting slab is successfully increased to 1.8 m/min for low-carbon steel, and the occurrence rate of slag entrapment was controlled below 0.5%.
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  Formation of off-corner depression of SPA-H in high speed thin slab caster

  YANG Guoming, WU Zhihui

  Continuous Casting. 2025, 44(3): 123-128. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240228

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  Production of SPA-H by thin slab casting and direct rolling can achieve high-speed, low-cost, high-precision and stable characteristics, and has more market advantages compared with conventional products. In practice, it is easy to have a temperature sharp drop in the Mold Expert at the wide side near the corner during high speed continuous casting process of SPA-H with Ti. And the corresponding location of the slab shows irregular longitudinal depression, which causes great interference to the production and quality stability control. The heat transfer data study of mold experts, the mineral phase and composition analysis of the slag rim and the tundish powder composition analysis during casting, and the inclusion analysis of the LF slag sample were done. The result shows that when the thermocouple temperature drops suddenly, the corresponding location of the slab will appear irregular longitudinal depression. In general, the second and the third rows thermocouple temperature vary, and the first row is relatively stable. The Ti-containing inclusion enrichment in the mold powder slag rim and tundish powder can be found. And different Ti treatment methods in LF shows significant difference in occurrence rate of the longitudinal depression. The formation of the off-corner longitudinal depression of SPA-H is deduced and the improvement measures are put forward.