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2023 Vol.  42 No.  6
Published: 2023-12-20
Continuous Casting Technology
Strand Quality
Continuous Casting Equipment
Comprehensive Summarization
Comprehensive Summarization
1 LEI Linlin, CHANG Yunhe, LUO Yanzhao, JI Chenxi, ZHU Jingliang, XIAO Hong, ZHANG Jiaquan
Submerged entry nozzle and its effect on mold flow behavior of slab casting
Slab casting is the primary forming process for various steel plate and sheet production, in which the semi-product slab quality is closely related to the mold metallurgical function supported by submerged entry nozzles(SEN). In the light of the current situation of slab continuous casting and the need for further development, the understanding to the geometry design, practice parameters and material category of SENs has been summarized in the paper based on reference review. It is shown that the adoption of SENs plays an important role in mold metallurgical behavior and the resultant slab quality, but there is no clear quantitative criterion to date for the design and application of SENs during casting production. In view of the frequent variation in castability of steel grades, slab formats and the related casting speed during actual production, the service organization for casting machines and the fluid flow control for SEN outlets by an electromagnetic facility have been discussed, which is supposed to realize an identical ideal mold flow pattern with a given SEN for any changing casting situation.
2023 Vol. 42 (6): 1-16 [Abstract] ( 148 ) [HTML 1KB] [PDF 0KB] ( 181 )
Continuous Casting Technology
17 FANG Ming, ZHANG Zhaohui, LÜ Ming, GUO Hongmin, LIANG Shaopeng, LI Xintao, GAO Qi
Optimization of solidification heat transfer and secondary cooling water distribution process for 170 mm×170 mm billet
In order to solve the problem of uneven distribution of cooling water in the 170 mm×170 mm billet continuous casting machine and reduce the production defects of the billet, a two-dimensional solidification heat transfer model was established to simulate the solidification heat transfer process of the billet and analyze the original secondary cooling. Combined with the target surface temperature setting, metallurgical criteria and high-temperature mechanical properties of steel, the secondary cooling process is optimized, the optimized total water volume of secondary cooling and the relationship between water volume and casting speed are proposed, and the water distribution scheme is simulated and verified. The research results show that after adopting the optimized water distribution model, the water volume in the crystallizer zone is reduced by 3% to 10%, the total water volume in the secondary cooling zone is decreased by 10% to 26%, and the cooling water distribution ratio of the foot roll zone and the secondary cooling zone is reduced. When the casting speed is 3.2 m/min and 3.8 m/min, the billet surface temperature control meets the metallurgical criteria and meets the production requirements of high-efficiency continuous casting secondary cooling water distribution. With the optimized secondary cooling water distribution model, the control accuracy and applicability of the secondary cooling water volume are further improved, and the cooling uniformity of the billet is increased, which has guiding significance for improving the quality of the billet.
2023 Vol. 42 (6): 17-24 [Abstract] ( 100 ) [HTML 0KB] [PDF 0KB] ( 8 )
25 SUN Yuqiu, WANG Min, ZHAO Jiaqi, JIANG Luheng, BAO Yanping
Influence of non-uniform corrosion of refractory material in SEN wall on flow-field of bloom
In order to study the effect of nozzle corrosion on the flow of molten steel in the mold, the mold of 55SiCr spring steel bloom with a cross section of 300 mm×390 mm was used as a prototype, which was studied by physical simulation and numerical simulation. A 1∶1 mold physical simulation experimental device was established, and the effects of casting speed and immersion depth on the mold flow field were obtained. Combined with the anatomical morphology of the nozzle, the corrosion model at the bottom of port of the submerged nozzle was established by Fluent numerical simulation software. The flow field in the mold and the interaction behavior of steel slag interface were simulated by using the combination of k-ε turbulence model and Volume of Fluid model (VOF). The results show that when the casting speed is 0.55 m/min, the average wave height is less than 0.5 mm, and when the immersion depth is 120 mm, the average wave height difference at the measuring point is 0.545 mm. The process parameters suitable for pouring are determined as follows: the casting speed is 0.65 m/min and the immersion depth is 130 mm. Nozzle corrosion will lead to mold bias, stream impact on the wall becomes stronger, velocity uniformity of steel-slag interface becomes worse, local vortex appears, the height difference of steel-slag interface increases from 21 mm to 28 mm, and the liquid surface is exposed.
2023 Vol. 42 (6): 25-35 [Abstract] ( 66 ) [HTML 0KB] [PDF 0KB] ( 10 )
36 ZHAO Bingbing, YUAN Tianxiang, LIU Yanqiang, QIAO Huanshan
Cause analysis and preventive measures of steel leakage in slab continuous casting
In order to study the causes and laws of breakout in slab continuous casting production, the breakout accidents in slab continuous casting production were statistically analyzed. The causes of breakout were analyzed by collecting the breakout slab morphology and production process parameters on site, and the breakout causes were classified and summarized based on the analysis of breakout accidents in recent five years. The results show that the main causes of breakout are poor performance of mold flux, large fluctuation of liquid level, insufficient functional accuracy of caster equipment and improper operation. In addition, molten steel composition, foreign matter involvement and sticking cold steel can also lead to breakout. The causes of breakout were classified and summarized, which provided theoretical guidance for the formulation of breakout prevention measures.
2023 Vol. 42 (6): 36-40 [Abstract] ( 60 ) [HTML 0KB] [PDF 0KB] ( 6 )
41 SHEN Kunrui, WANG Chen, WANG Chao, ZHOU Wenhao, YANG Wenzhi, CHEN Botao, LIU Qing
Effect of casting speed on solidification structure and carbon segregation of 40CrA bloom
The celluar automation finite element(CAFE) model and solidification heat transfer mathematical model were established to improve the problem of carbon segregation in the current continuous casting conditions of 40CrA bloom. And the influence of casting speed change on the solidification structure and microstructure of the bloom was studied. The simulation results show that, when the casting speed is 0.55 m/min, CET(columnar crystal structure to equiaaxial crystal transformation) starts from 69 mm away from the surface of the casting blank and ends at 122 mm away from the surface of the casting blank. When the casting speed is 0.59 m/min, the density of columnar crystal and equiaxed crystal is best. Combined with the industrial test, the results show that when the casting speed increases from 0.55 m/min to 0.59 m/min, the range of carbon segregation index decreases from 0.15 to 0.10, the fluctuation range decreases by 33.3%, the distribution of carbon content is more uniform, and the quality of billet is obviously improved.
2023 Vol. 42 (6): 41-48 [Abstract] ( 44 ) [HTML 0KB] [PDF 0KB] ( 8 )
49 QI Jie, ZHANG Jianghao, LIU Chengjun
Effect of different flux raw material types on physical and chemical properties of CaO-Al2O3 based mold fluxes
In order to explore the influence of flux raw materials on the performance of CaO-Al2O3-based mold flux and provide theoretical guidance for the preparation of industrial slag, the changes of melting temperature, viscosity characteristics and crystallization properties were studied by using different raw material combinations such as 'soda ash + fluorite', 'sodium fluoride + fluorite' and 'single sodium fluoride'. The results show that the melting temperature of slag samples is not significantly different due to the difference of ingredients. Similar viscosity characteristics can be obtained by using 'soda + fluorite' and 'sodium fluoride + fluorite' modes. In the single sodium fluoride mode, the viscosity and breaking temperature increased significantly. When the 'soda ash + fluorite' and 'sodium fluoride + fluorite' modes are used, the completely crystallized phases are LiAlO2 and Ca2SiAl2O7, and the relatively weaker crystallization properties can be obtained by the 'sodium fluoride + fluorite' mode. When a single sodium fluoride is used as the flux raw material, the composition of the slag gradually shifts to the primary crystal zone of the calcium aluminate composite due to volatilization, and a large amount of Ca3Na4Al4O11 precipitated during the cooling process.
2023 Vol. 42 (6): 49-54 [Abstract] ( 64 ) [HTML 0KB] [PDF 0KB] ( 6 )
55 XIA Pengcheng, WU Huajie, AN Hanghang, CAI Shougui, DING Zhentao
Based on numerical simulation to improve 45 steel intermediate crack of continuous casting process optimization
Aiming at the intermediate crack problem of 45 steel billet, the solidification heat transfer and solidification structure model were established by the finite element simulation technology, and the numerical simulation and industrial test were combined to improve the intermediate crack of the billet. The results show that under the conditions of pulling speed of 1.8 m/min, superheat of 30 ℃, specific water of secondary cooling of 0.50 L/kg, and distribution ratio of each foot roll zone and secondary cooling zone 1 to 4 zone of 40%-25%-20%-12%-3%, the middle crack problem of 45 steel billet is obviously improved by industrial tests.
2023 Vol. 42 (6): 55-61 [Abstract] ( 98 ) [HTML 0KB] [PDF 0KB] ( 12 )
62 ZHAO Ru, LONG Qian, WANG Wanlin
Researching thermodynamics and interface characteristics of inclusion formation in ultra low carbon IF steel
The control of deoxidized inclusions in RH refining process of ultra-low carbon IF steel is a key factor affecting the quality of continuous casting slab. In this paper, the properties of inclusions in the actual RH refining and continuous casting process are evaluated, and the equilibrium phase diagram of the Fe-Al-Ti-O component is calculated based on the thermodynamics of Factage software. The interface characteristics between different w(Al)/w(Ti) composition steel liquid and an alumina substrate were measured by improving the horizontal drop method, and the number distribution of inclusions in molten steel for different w(Al)/w(Ti) was counted in the experiment. The results show that there are large clusters of alumina inclusions in actual production, and active elements such as Ti and Mg could adhere to the surface of alumina to form a Mg-Ti-O film. And, the phase diagram calculation results show that the formation of Ti-containing oxide films can be completely inhibited when the Ti content is 0.06% and the Al content is greater than 0.12%. Furthermore, the Al and Ti concentration in molten steel increased from 0.017% and 0.028% to 0.0785% and 0.045%, respectively, and the contact angle between alumina and molten steel increased from 110.93° to 133.73° and decreased to 101.49°, respectively; the purity of molten steel can effectively improve by increasing w(Al)/w(Ti).
2023 Vol. 42 (6): 62-69 [Abstract] ( 64 ) [HTML 0KB] [PDF 0KB] ( 9 )
Strand Quality
70 ZHENG Qian, DENG Anyuan
Simulation on temperature characteristics of casting billet during induction heating process
In order to study the characteristics of temperature field distribution during electromagnetic induction heating process of casting billet. Based on the actual process parameters, an induction heating device for casting billet was designed. The numerical simulation method was used to simulate the induction heating process of casting billet with dimensions of 200 mm×1 800 mm×10 m. According to the simulation results, the influences of frequency, transmission speed, power and energy consumption on the heating effect were analyzed. The simulation results show that it is more advantageous to use the medium frequency 800 Hz to 1 000 Hz in the induction heating process of the casting billet. The influence of conveying speed and power consumption of casting billet is also studied. It is considered that the temperature distribution uniformity of casting billet can be improved by increasing conveying speed and adding insulation measures under the condition of equipment. However, due to the influence of the size of the billet itself, too fast transportation speed will lead to uneven heat and affect the uniformity of temperature distribution of the billet. After the casting billet leaves the induction heater to complete heating, adding insulation measures to insulate and transport the casting billet, increasing the conveying speed to 0.1 m/s can reduce the power consumption and improve the uniformity of the overall temperature distribution of the billet.
2023 Vol. 42 (6): 70-77 [Abstract] ( 59 ) [HTML 0KB] [PDF 0KB] ( 9 )
Continuous Casting Equipment
78 LI Youmei, CHENG Guoguang, MIAO Zhiqi, DAI Weixing, REN Qingxue, SHU Youliang
Structural optimization and dead volume model of six-flow symmetric tundish
In order to optimize the flow field and promote the floating of inclusions, a six-flow T-shaped symmetrical tundish in a steel plant was taken as the object and the combined method of water model and numerical simulation was used to study the flow field characteristics of the tundish, and a dead volume model was established to characterize the flow of molten steel in the tundish, and propose improvement plans in a targeted manner. The results show that the prototype tundish has defects such as short molten steel residence time, inactive edge nozzles, and a dead zone volume fraction of up to 30.9%. There are a large number of “kinetic energy invalid zones” in the pouring process. It is optimized by adjusting the upward angle of the diversion holes of the U-shaped retaining wall. After optimization, the velocity distribution of the molten steel in the tundish is more uniform, the actual average residence time increases by 10.5 s, and the dead zone volume fraction decreases by 13.3%. The “kinetic energy invalid area” of the tundish is greatly reduced, the flow consistency of the nozzle is improved, and the overall mixing effect of the tundish is improved.
2023 Vol. 42 (6): 78-85 [Abstract] ( 44 ) [HTML 0KB] [PDF 0KB] ( 8 )
86 LI Wei, WANG Zixian, HUANG Dajun, ZHANG Chaojie, ZHANG Liqiang
Study on influence of intermediate coating agent on foam slag elimination and refractory service life
In order to investigate the effective control and removal of slag in the continuous casting production process and the influence of the tundish covering agent composition on the erosion and service life of tundish refractories, this study compares the performance of different types of tundish covering agents, optimizes the usage of tundish covering agents, and improves the service life of tundish lining refractories. In this research, field experiments were conducted to compare the chemical composition of the impact zone slag produced after using three different types of covering agents, and analyze their effects on the erosion and service life of tundish refractories. Meanwhile, static crucible slag infiltration tests were performed in the laboratory to improve the magnesia dry mix at the slag line, optimize the impact zone structure of the tundish, and find the best application method for the covering agent to enhance the service life of the tundish lining refractory. The research results show that: The eco-friendly covering agent used in combination has the best performance compared to other types of tundish covering agents. The combined use of eco-friendly covering agents can quickly eliminate the foam slag in the impact zone. The combined use of eco-friendly covering agents can significantly improve the quality of molten steel and reduce heat loss during the casting process; it can also reduce the erosion degree of the tundish lining refractory, thereby prolonging the service life of the tundish and achieving the goal of cost reduction and efficiency enhancement.
2023 Vol. 42 (6): 86-93 [Abstract] ( 50 ) [HTML 0KB] [PDF 0KB] ( 8 )
94 LI Yanzhi, LI Hongbo, SUN Yanhui, GAO Zhenwei
Flow field optimization of three-stream symmetric tundish numerical simulation
In order to further improve the product quality of a steel plant, the volume of its tundish has been expanded and the original flow structure has been changed. In this paper, the side hole of the retaining wall after the expansion of the three-stream tundish has been optimized to reduce the proportion of dead zone in the tundish and increase the utilization efficiency of the tundish. The tundish currently used in the plant has the problems of poor consistency of water inlets between streams and large proportion of dead zones. In this paper, the tundish retaining wall structure is optimized by numerical simulation using the fluent software of Ansys. Although the temperature difference between the flows in the tundish after the improvement of the side hole of the retaining wall is 0.9 ℃ higher than the original one, the proportion of dead zone is reduced from 21.48% to 14.70%, which effectively reduces the proportion of dead zone, improves the consistency between the flows in the tundish, and achieves a better metallurgical effect.
2023 Vol. 42 (6): 94-99 [Abstract] ( 44 ) [HTML 0KB] [PDF 0KB] ( 8 )
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