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18 February 2025, Volume 44 Issue 1
    

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    Comprehensive Summarization
  • Current status and prospect of CO2 resource utilization technology in steelmaking process
    LI Chenxiao, ZHAO Peng, MENG Xin, SHEN Haojie, ZHANG Yun, FENG Zikang
    Continuous Casting. 2025, 44(1): 1-10. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240077
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    Carbon emissions from the iron and steel industry account for a large proportion of all industries in China, and how to realize carbon emission reduction and CO2 resource utilization in the steelmaking process under the background of "double carbon" has attracted much attention. Taking the resource utilization of CO2 in the iron and steel industry as an entry point, it introduces the current situation of CO2 emission and resource utilization in the iron and steel industry, and focuses on the analysis of the technical status of applying CO2 as reaction gas, stirring gas and protective gas in the steelmaking process. Through thermodynamic calculations, it is concluded that when CO2 oxidizes 0.1 mass% of the metal elements in the iron liquid [M], the comprehensive exothermic heat release is reduced, and it plays a role of controlling the temperature. The analysis of CO2 as a stirring gas shows that CO2 is used in the steelmaking process to reduce carbon emission. As a stirring gas,CO2withthe utilization rate of about 85% can provide twice as much stirring effect as Ar. CO2 can be used as a kind of resource gas gradually applied in the steelmaking process, with energy saving and emission reduction and cost-effective effect, but needs to further clarify the reaction characteristics of CO2 in the high-temperature melting pool and the role of the form, in order to accurately and efficiently realize the resourceful use of CO2.
  • Progress on copper plate crack for funnel mold
    WANG Guobin, ZHANG Hui, YANG Chunzheng, WANG Minglin
    Continuous Casting. 2025, 44(1): 11-19. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240083
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    With the advancements in thin slab direct rolling and efficient continuous casting, the issue of funnel-shaped cracks in copper molds resulting from high-speed casting has become increasingly severe. Researchers had explored the formation mechanism and control of these cracks in thin slab casting by means of theoretical analysis, industrial experiments and numerical simulation methods, aiming to prolong the lifespan of copper molds and reduce production costs. The macroscopic morphology and hazards of funnel-shaped copper mold cracks were elucidated, and the mechanisms of crack formation, including thermal fatigue, creep fatigue, and elemental erosion, were summarized. A comprehensive review of the development of thermal/mechanical analysis models for copper molds was provided, along with an overview of measures for controlling copper mold cracks, new research directions were proposed for the mechanism of copper mold crack formation, thermal/mechanical analysis models, and control strategies.
  • A review of characterization methods for non-metallic inclusions in continuous casting slab
    ZHAO Jingxin, FENG Ting, ZHANG Ying
    Continuous Casting. 2025, 44(1): 20-29. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240085
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    Inclusions in the steel have a significant impact on the performance. It is necessary to detect and analyze non-metallic inclusions to improve the quality and performance of steel products. A comprehensive introduction to the detection and characterization methods for inclusions in the steel was reviewed from three aspects: the characterization of inclusion features, the extraction of inclusions by dissolution, and non-destructive three-dimensional detection of inclusions. Different characterization methods were compared comprehensively from different aspects including size analysis range, advantages and disadvantages. Optical microscope and other methods can directly observe the morphology of inclusions with a wide analysis range, but their magnification is relatively low, making it difficult to distinguish the morphology characteristics of small inclusions. However, scanning electron microscopy and other methods can clearly observe the two-dimensional morphology and the composition of inclusions, but their analysis cost is relatively high. The erosion method can characterize the three-dimensional morphology of inclusions, but its operation is relatively complex and time-consuming. The application of non-destructive characterization methods such as ultrasonic testing can characterize inclusions without damaging the specimen, which is convenient and fast.
    • Monographic Study
  • Prediction method for liquid level fluctuation in continuous casting mold based on GA-RF
    HE Yibo, ZHANG Bingqian, ZHOU Hualun, ZHANG Tao, WANG Liyong, LI Yihong
    Continuous Casting. 2025, 44(1): 30-35. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240084
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    In the critical process of metallurgical production, the continuous casting is closely linked to the quality of the cast slab products. Among various parameters, the liquid level fluctuation in the mold is one of the most crucial during the continuous casting process. Therefore, accurate monitoring of the liquid level fluctuation inside the mold is particularly critical. An artificial intelligence model aimed at real-time accurate prediction of the mold liquid level fluctuations was introduced. The model employs a genetic algorithm (GA) optimized random forest (RF) technique, referred to as the GA-RF model. The model optimizes the parameters of random forest network through genetic algorithm, aiming at finding the optimal parameters of the model and obtaining the model with the best prediction performance. Experimental results demonstrate that the GA-RF predictive model achieves a mean absolute error (MAE) of 0.534 and a mean squared error (MSE) of 0.73, with a high prediction success rate of 96%. Compared with CNN model, BP model and SVM model, it is found that GA-RF model MAE and MSE are superior to other models, confirming the model’s high precision and its ability to meet the stringent requirements of practical production applications. Furthermore, through sensitivity analysis, the influence of different production parameters on the model is also discussed.
  • Numerical simulation of fluid flow, heat transfer and stress behavior of six-strand continuous casting tundish
    XUE Bingrui, ZHENG Shuguo, ZHU Miaoyong
    Continuous Casting. 2025, 44(1): 36-47. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240098
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    A full-structure physical model was established based on a 30-ton six-strand rectangular billet continuous casting tundish in a domestic steel plant, and the fluid-solid-thermal coupling numerical simulation was carried out. The flow field, temperature field and stress distribution behavior in the tundish were studied. Based on the von Mises stress considering the thermal effect, the damage of the refractory was evaluated. A damage model of the turbulence inhibitor-porous baffle integrated flow control element was established, and the flow and heat transfer behaviors in the tundish before and after the damage of the flow control element were compared and analyzed. The results show that the average volume temperature of each fluid domain and solid domain in the six-strand tundish is quite different. The maximum temperature difference between the working layer and the slag layer and the air layer can reach 312 and 578 K, respectively. The stress of the wall surface reaches 40-52 and 52-73 MPa, respectively, which is higher than that of the wall surface in contact with the molten steel(32-40 MPa).In the integrated flow control element, the easily damaged area is mainly three parts: a turbulence suppressor, a retaining wall diversion hole, and the connection between the corner of the porous retaining wall and the side wall as well as the bottom. The stress in these parts reaches 35-52 MPa. After the failure of the integrated flow control element, the response time of No.1 and No.2 outlets decreased by 26 and 17 s respectively, the volume fraction of the piston zone decreased by 25.5%, the volume fraction of the dead zone increased by 9.4%, and the consistency of each flow was obviously weakened. The minimum temperature of molten steel at the outer corner of No.3 outlet decreased by 14 K. The field industrial test shows that the failure morphology of the integrated flow control element obtained by numerical simulation in this paper is in good agreement with the actual failure situation.
  • Numerical simulation of tundish removal of inclusions based on OpenFOAM
    LI Gengyang, WANG Rudong, LIU Jinrui, CUI Heng
    Continuous Casting. 2025, 44(1): 48-55. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240080
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    In the continuous casting process, tundish plays an important role in controlling the number of inclusions and improving the quality of the casting billet. A three-dimensional mathematical model was established by using the open-source computational fluid dynamics software OpenFOAM by numerical simulation, and the effects of particle size, molten steel flow rate and shape of non-metallic inclusions on the removal rate of non-metallic inclusions in tundish were analyzed. The results show that with the decrease of the particle size of the inclusions, the removal rate of non-metallic inclusions gradually decreases. When the flow rate of molten steel is 0.47 m3/min, the removal rate of non-metallic inclusions with a particle size of 200 μm reaches 97.64% and the removal rate of non-metallic inclusions with a particle size of 10 μm is only 1.298%. When the particle size of the inclusions is less than 100 μm, the removal rate increases significantly with the increase of particle size; and when the particle size of inclusions exceeds 100 μm, the increase of particle size has no obvious effect on the removal rate. With the increase of molten steel flow, the removal rate of non-metallic inclusions showed a decreasing trend, and the molten steel flow rate had a greater effect on the removal rate of non-metallic inclusions with particle sizes of 50 μm, 75 μm and 100 μm, but had little effect on the removal rate of non-metallic inclusions at 200 μm, 10 μm and 25 μm. With the decrease of the shape factor, the removal rate of non-metallic inclusions showed a decreasing trend, and the removal effect of spherical non-metallic inclusions (shape factor 1) was the best. And when the equivalent diameter of non-metallic inclusions was less than 100 μm, the influence of shape factor on the removal rate of inclusions gradually decreased with the decrease of the equivalent diameter of non-metallic inclusions.
  • Optimization design of steel ingot mould based on multiphase solidification model
    SONG Yudan, LIU Qin, LIU Shirui, YANG Zhen, GUAN Rui, AI Xingang, LI Shengli
    Continuous Casting. 2025, 44(1): 56-63. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240088
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    At present, ingot casting has obvious advantages in producing special steel, manufacturing large-weight ingots and making small-lot castings. However, steel ingots generally have many internal defects, low yield, and high mold loss. How to optimize the ingot structure has become the fundamental method to improve the internal quality of steel ingots. Based on the multiphase solidification model, it took a 5 t cubic ingot as the research object and focuses on the effects of different feeding efficiency ratios, slow cooling process and strong cooling process on the macro segregation behavior of steel ingots. The results showed that increasing the rising capacity ratio or using the strong cooling process has a significant effect on improving the macroscopic segregation, while the slow cooling process has little effect. For this ingot, increasing the rising capacity ratio to more than 11.5% can restrain the positive segregation of the head above the riser line. It can save the design time of the ingot pattern for the designer and at the same time provide a data reference for the actual production on site.
    • Technology Exchange
  • Analysis of inhomogeneity of solidification and genetic problems of continuous casting slab
    LI Xinyu, WEI Zijian, WANG Qican, WANG Xudong, YAO Man
    Continuous Casting. 2025, 44(1): 64-70. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240071
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    The inhomogeneous heat transfer, solidification, thickness of primary shell, temperature and stress of secondary cooling zone directly affect the surface and internal quality of slab. The temperature field and stress field of the whole process of Q235B slab in a steel plant were simulated by ANSYS Finite Element Software, the surface temperature, equivalent stress, shell inhomogeneity, heredity and crack sensitivity were analyzed. The results show that the non-uniformity of slab solidification thickness in mold is inherited to secondary cooling zone, and the non-uniformity of equivalent stress on slab surface is less inherited, the non-uniformity of surface equivalent stress wasgreatly improved. In the case study, the temperature at the left corner of the inner arc was the lowest (892 ℃), the equivalent stress was the highest (12.2 MPa), and the temperature at the deflection corner was the highest (1 263 ℃), the equivalent stress was the lowest (2.54 MPa). The sensitivity of slab surface crack is 1/4 center > 1/8 center > 1/2 center.The sensitivity index of slab surface crack reaches the maximum value of 0.52 in mold. In the early stage of secondary cooling, the crack sensitivity is increased.And in the late stage of solidification, the shell is thicker, the crack sensitivity is lower and the change range is small.
  • Evaluation of flow field of four-stream tundish and optimization of baffle structure
    HUO Jia, LI Yu, SONG Sicheng, ZHANG Xichao, SUN Yanhui
    Continuous Casting. 2025, 44(1): 71-80. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240074
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    In order to evaluate the influence of baffle wall structure on the flow field, improve the flow behaviour of liquid steel in the middle tundish of a steel plant, select the optimal solution in line with the current production conditions and improve the quality of special steel grades, the guide holes on the basis of the original baffle wall structure were designed and optimized.Orthogonal experiments are designed considering the number of guide holes, mounting height, and inclination angle factors.The flow field of the tundish under the prototype retaining wall structure is evaluated by the water simulation experiment method for conducting range analysis. Thus, considering the influence of various factors under the indexes of dead zone ratio and standard deviation of peak time, the optimal diversion hole structure can be found.Numerical simulation is carried out using Ansys Fluent to simulate the flow and temperature fields of the tundish before and after optimization. The experimental results show that the flow field of the prototype tundish has problems such as poor consistency at the mouth and poor flow characteristics of the internal liquid steel, with a dead zone ratio of 29.26% and a peak time standard deviation of 61.52 s.Under the water model experiment, the optimized tundish dead zone ratio is 27.92%, which is 1.34% higher than that of the prototype tundish.The standard deviation of peak time is 87.27% higher, and the water inlet temperature difference is reduced to 0.2 K.The flow field is very uniform as a whole, and the consistency of the two streams is significantly improved.
  • Analysis of liquid slag performance in high aluminum steel crystallizer
    QI Shi, LI Xiaoyang, ZHAO Chunbao, LIU Zengxun, XIAO Pengcheng, ZHU Liguang
    Continuous Casting. 2025, 44(1): 81-86. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240093
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    During the continuous casting process of producing high aluminum steel, at the liquid level of the crystallizer, there is a strong interface reaction between the Al element in the molten steel and the mold slag, which leads to serious denaturation of the mold slag and directly endangers the quality of the billet and the smooth operation of continuous casting production. The mold slag layer was dynamically sampled during the continuous casting process of high aluminum steel, and analyzed the changes in the composition and physicochemical properties of the slag layer during the continuous casting process. The reaction behavior between steel slag was studied through thermodynamics and kinetics. The results showed that during the pouring process, the Al2O3 content in the slag increased from 1.40% to 24.75%, and the SiO2 content decreased from 32.26% to 17.69%. The average viscosity of the liquid slag increased from 0.38 Pa·s of the original slag to 0.58 Pa·s, and the average melting temperature increased from 1 112 ℃ of the original slag to 1 189 ℃. The trend of changes in the composition of mold slag conforms to the thermodynamic law of steel slag reaction, and the mass transfer behavior of Al2O3 in the liquid slag layer is a limiting link in the interface reaction of steel slag and the degree of liquid slag denaturation.
  • Research and application of intelligent fixed weight system for small billets
    MA Xuzhao, XIE Fei, ZHENG Guoqiang, GUO Jiaxing, WANG Song, HAO Jianmin, WANG Hongwei, ZHANG Liqiang
    Continuous Casting. 2025, 44(1): 87-92. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240070
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    In the steel production process, continuous casting billets are cut according to length; rolled steel is rolled by weight; and the inconsistency of steel rolling implementation standards directly causes fluctuations in the total length of rolled products. These all resulted in the generation of a large number of short length materials and waste materials, which has become an industry pain point that needs to be solved urgently. The basic principles of fixed-weight cutting technology, influencing factors of fixed-weight cutting and related models of continuous casting billet are expounded. The intelligent fixed-weight system is developed to make continuous casting billets cut by weight to realize steel-rolling coupling, which has been successfully applied to Hebei Tangyin Iron and Steel Co., Ltd. The results of the model show that the difference between the theoretical weight and the actual weight is ±0.2%, the fixed weight pass rate reaches more than 90%, the actual weight yield reaches more than 97.5%, and the fixed size rate is stable at more than 99.5%. This greatly improves the negative difference stability and yield level of small bar size products while maintaining high yield, and provides a reference for the development of fixed weight cutting technology for related enterprises.
  • Physical and numerical simulation of four-strand tundish structure optimization
    LI Xin, LI Hao, TAO Chenggang, ZHU Liyan, WANG Xinyao, HE Fei
    Continuous Casting. 2025, 44(1): 93-101. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240072
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    In order to optimize the metallurgical effect of four-strand tundish for extra-large round billet, the flow control devices were explored and optimized through physical simulation experiments firstly, and the influence of U-shaped baffles with different parameters, turbulence inhibitor and dam on flow field was analyzed. The optimal flow control device was selected. And then the flow field, temperature field and concentration field of tundish before and after optimization were simulated and verified by CFD/FLUENT software. Through the physical and numerical simulation, it is found that the flow field and temperature field of optimized tundish are greatly improved. The actual average residence time, stagnation time and peak time of each outlet are extended and the consistency is increased to more than 80%. The proportion of dead zone volume decreases from 32.18% of bare tundish to less than 10%, and the proportion of plug flow volume increases from 9.52% to more than 20%. The maximum temperature difference of tundish decreases from 39.01 K of bare tundish to 16.22 K, and the temperature difference of each outlet decrease from 3.15 K of bare tundish to 0.31 K.
  • Simulation and optimization of characteristic parameters of meniscus in thin slab continuous casting mold
    YU Yao, WANG Shi, LI Jingshe, ZHENG Xutao, MA Ming
    Continuous Casting. 2025, 44(1): 102-110. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240066
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    The flow of liquid steel in continuous casting mold is a complex three-dimensional turbulent flow, which includes many complex phenomena, such as turbulence in the SEN and mold, the movement of bubbles and inclusions, and the influence of multiphase flow and electromagnetic force on liquid steel flow.The fluctuation of the liquid level of the mold is an important reason for the surface quality of the casting slab.In the actual production process, the fluctuation of liquid level generally only detects a single point or a single area, which cannot reflect the overall fluctuation state of the liquid level. However, there is no direct detection method for the flow field, which is generally analyzed and evaluated by a certain proportion of water model. The characteristic parameters (liquid level difference, liquid steel flow rate) at the mold meniscus are evaluated by numerical simulation andnail board test. The results of numerical simulation and nail board test are basically consistent. Numerical simulation results show that the EMBR current changes by 50A, the maximum surface flow rate changes by 0.01-0.02 m/s,while the maximum liquid level difference changes little. When the SEN insertion depth increases by 50 mm, the maximum surface flow rate decreases by 0.03-0.06 m/s, and the maximum liquid level difference decreases by 2 mm. The pulling speed increases by 0.3 m/min, the maximum surface flow rate increases by 0.04 m/s, and the maximum liquid level difference increases by 2 mm.SEN insertion depth and casting speed have great influence on liquid steel flow rate and liquid level difference, while EMBR current has little influence. Under the condition of casting speed 5.2 m/min, EMBR current 175A, SEN insertion depth 170 mm, the slab quality is better.
  • Optimization and application of continuous casting process based on numerical simulation of automobile beam steel slab
    YU Kezai, ZHANG Pan, WANG Guobin, XU Lijun
    Continuous Casting. 2025, 44(1): 111-119. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240089
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    Aiming at the bulging deformation and internal quality defects of 510 L slab of automobile beam steel, a slab solidification heat transfer model was established to study the effects of different casting speeds and specific water flow on the slab solidification process and shell thickness, and the effect of soft reduction process characteristic parameters on the quality defects of slab core before and after process optimization was analyzed. Based on the simulation analysis of solidification heat transfer and production conditions, the specific water flow of secondary cooling was increased from 1.01 L/kg to 1.41 L/kg; the soft reduction position was optimized from three segments to two segments and the reduction amount was adjusted. The results showed that the bulging deformation of the slab is the largest at the entrance of the first segment. After the process optimization, the shell thickness at the entrance of the first segment increases from 39.05 mm to 40.78 mm, and the bulging deformation decreases from 0.69 mm to 0.51 mm. The reduction rates of the 7th and 8th segment increase to 0.94 mm/m and 1.19 mm/m, and the overall internal quality of the slab is significantly improved. The center segregation rating is reduced to C 0.5, and the porosity is 0.5.
  • Practice of quality control process for 460 mm extra thick plate
    ZHOU Guicheng, CHANG Yunhe, WANG Defu
    Continuous Casting. 2025, 44(1): 120-125. https://doi.org/10.13228/j.boyuan.issn1005-4006.20240103
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    Defects such as slab shape, surface cracks, center segregation, and center porosity are key issues limiting the production and development of ultra-thick slab continuous casting. A domestic steel plant has newly built a 460 mm thick slab casting machine. By studying the characteristics of the continuous casting production process for thick slabs and addressing the main defects of thick slabs, a 460 mm thick slab continuous casting production process technology has been developed, including high casting speed, secondary cooling dynamic amplitude cutting control process, high alkalinity and viscosity process of protective slag, low superheat control, and large pressing process at the solidification end of the slab. This has solved the problem of bulging of thick slabs, reduced the occurrence rate of surface cracks on thick slabs, and improved the center looseness and center segregation of thick slabs.
Started in 1982 (Bimonthly)
ISSN 1005-4006　CN 11-3385/TG
Manager: China Association for Science and Technology
Sponsor: The Chinese Society for Metals
CISRI Boyuan Publishing Co., Ltd.
Editor-in-Chief: BAO Yanping
Editor and Publisher: CISRI Boyuan Publishing Co., Ltd.
Domestic Distribution: Beijing Newspapers and Periodicals Distribution Bureau, China Post Group Co., Ltd. (No.82-441)
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