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	2023 Vol. 42 No. 1
	Published: 2023-02-18



	Continuous Casting Technology Strand Quality Continuous Casting Equipment Technology Exchange

Continuous Casting Technology

	1	LU Hai-biao, ZHANG Hui-qi, ZHONG Yun-bo, REN Wei-li, LEI Zuo-sheng
		Simulation of flow field in a slab continuous casting with in-mold electromagnetic stirring
		Electromagnetic stirring has great effect on the flow field in the mold and the behavior of steel/slag interface, a physical model of slab mold with similarity ratio of 1∶5 and a mathematical model were built to investigate the effect of electromagnetic stirring (EMS) current on the flow field, the freezing index (R_f) and slag entrapment index (R_e) were introduced to evaluate the probability of meniscus freezing and slag entrapment, respectively. The results indicate that the flow field measured by physical model can be using as the validation for mathematical simulation. When EMS is not applied, the flow field within the mold is a classical double-roll structure, the flow velocity at free surface is relatively small, the freezing index and slag entrapment index are 0.52 and 0, respectively. The flow field changes significantly for the case with EMS, a horizonal recirculation flow has generated in the upper part of mold, the flow velocity at free surface increases. With the increase of EMS current, the recirculation flow enhances, the freezing index decreases while the slag entrapment index increases, as the EMS current increases to 700 A, the freezing index and slag entrapment index change to 0.04 and 0.245, respectively. Therefore, considering the slag entrapment index and meniscus freezing index, the optimizing stirring current is 600 A.
		2023 Vol. 42 (1): 1-9 [Abstract] ( 257 ) [HTML 1KB] [PDF 6331KB] ( 592 )

	10	LI Xiang-long, SUN Qun, QU Tian-peng, WANG De-yong
		Effect of electromagnetic stirring on the aggregation and removement of liquid inclusions in continuous casting mold
		The characteristics of high casting speed is high efficiency and low cost, which indicates the future of continuous casting process. In this work, the multiphase flow and inclusion removements in a CSP mold are studied based on the Large Eddy Simulation model and Eulerian-Lagrange approach. Results reveal that the electromagnetic stirring (EMS) significantly intensifies turbulence in a continuous casting mold and remove more inclusions into the liquid slag. What's more, the transverse velocity is enhanced due to EMS and thus the injection of steel is confined with the mold, which significantly reduces the injection depth of liquid steel and beneficial for the floating of inclusions. In addition, due to the fact that horizontal velocity is high, the injection is confined within the electromagnetic stirring zone, which significantly reduces the injection depth of molten steel, promoting floating of inclusions. In addition, because the flow field is intensified under the effect of EMS, the slag-metal interface fluctuates more frequently, so more slag drops are involved into the steel. So the EMS has double-sided effects: Although it may enhance the removing rate of inclusions, it may also run the risk of slag entrapment into the steel. This model has a certain guiding significance to control the production of high drawing speed continuous casting slab.
		2023 Vol. 42 (1): 10-17 [Abstract] ( 138 ) [HTML 1KB] [PDF 6178KB] ( 223 )

	18	ZHANG Xiao-wei, BAI Xiao-lu, SHI Lei, KANG Xin-lei, ZHANG Chao-jie, ZHANG Li-qiang
		Numerical simulation of solidification temperature field of SWRH72B-S wire steel continuous casting billet
		In order to develop the solidification heat transfer model suitable for No. 6 continuous casting caster, the relevant parameters were modified by the actual production data, and the accuracy was verified by the analysis and research of the white band, liquid core width and surface temperature of the casting billet in the air cooling section of low carbon wire steel casting billet.The casting speed, superheat and specific water were calculated and analyzed, and the influence degree of them on the surface temperature of the billet and the position of the end of the liquid core was obtained. The results show that the internal quality of billet can be improved by using the solidification heat transfer model in line with the specific continuous caster and using the model to discuss the production process.
		2023 Vol. 42 (1): 18-23 [Abstract] ( 143 ) [HTML 1KB] [PDF 2653KB] ( 350 )

	24	ZUO Xiao-tan, ZHAO Li, ZHANG Ya-bing, ZHANG Xu-bin, WANG Qiang-qiang
		Effect of gas curtain in tundish on flow field and inclusions removal
		To eliminate the adverse effect resulting from inclusions formed during the continuous casting of high-Ti steel, this study considered the influence of gas adsorption on inclusions, built the numerical model of the flow field and inclusions motion and removal within tundish, and discussed the influence of gas curtain and its location on the flow and inclusion removal. The main results show that as particles with small sizes had good following ability driven by molten steel, and low buoyancy, the removal rate of particles in the 1-10 μm range was almost zero under traditional tundish. After applying the gas curtain with 5 L/min gas flow rate, the removal rates for both Al₂O₃ and TiN were enhanced obviously, 21.7%-34.6% for Al₂O₃ particles and 22.7%-33.14% for TiN particles in the range of 1-10 μm. When the gas curtain was located between the turbulence inhibitor and the up-dam, the flow speed of steel circulation became larger, to increase the probability of inclusion collision with bubbles. Thus, the probability of inclusions being captured by bubble increased, which was more conducive to inclusion removal. The current study can provide theoretical guidance for inclusion removal in the continuous casting of high-Ti steel.
		2023 Vol. 42 (1): 24-30 [Abstract] ( 117 ) [HTML 1KB] [PDF 4807KB] ( 196 )

	31	JIANG Tao, XIAO Hong, LIU Yong, JIANG Xiao-qi
		Influence of billet physical properties on temperature field during induction heating
		In order to study the influence of physical properties of billets on the temperature field during induction heating, a coupled finite element model of electromagnetic and heat transfer of moving billets was established, and the influence of a specific physical quantity on the temperature field of billets was studied by single factor analysis method. Then, the influence of the two billets with different physical properties on the temperature field is compared and analyzed. The results show that the influence of relative permeability on cross section temperature is mainly caused by the larger induced current and the shallower yield depth. Under the influence of relative permeability and thermal conductivity, the temperature difference between carbon steel core and surface decreases slightly, while that between stainless steel core and surface increases slightly. In addition, combined with the actual heating process, when multiple physical properties change with temperature, the conductivity and specific heat capacity of carbon steel attenuate the effect of the relative permeability on the rapid rise of surface temperature during heating. The final test data show that the theoretical calculation results are 2.44%-6.97% higher than the actual heating results while the trend of temperature rising is consistent.
		2023 Vol. 42 (1): 31-40 [Abstract] ( 142 ) [HTML 1KB] [PDF 8636KB] ( 172 )

Strand Quality

	41	YANG Qi-jun, YANG Geng-chao, LIU Jian, WANG Xu-ji, ZHAO Yang
		Mechanism and prevention of internal crack generation of 52CrMoV4 continuous casting slab for spring flat steel
		The quality of continuous casting slab is directly related to the subsequent rolling process and the quality of medium and heavy plates. In this paper, the causes of the internal crack of 52CrMoV4 continuous casting slab for spring flat steel were analyzed by means of macrostructure inspection, microstructure observation and composition analysis. The results showed that the central segregation of Cr, Mn and Mo in the continuous casting slab caused martensitic transformation and large tensile stress during the cooling process, which was the main reason for the central crack of the 52CrMoV4 continuous casting slab. After increasing the purity of molten steel, reducing the pouring temperature and casting speed, increasing the electromagnetic stirring force as well as increasing the mass fraction of N during smelting, the crack defects in the center of the 52CrMoV4 steel slab were eliminated and the quality of the center of the slab was effectively improved. As a result, the quality of the center in the hot-rolled spring flat steel was good and fully met the requirements of customers.
		2023 Vol. 42 (1): 41-46 [Abstract] ( 126 ) [HTML 1KB] [PDF 1992KB] ( 391 )

	47	FAN Bin, LIU Li, ZHANG Shi-yu, LIU Ning-ning, LIU Xiao-ming, WANG Qiang
		Gear steel 20CrMnTiH hardenability/macro segregation control
		Aiming at the large fluctuation of 20CrMnTiH hardenability of ø500 mm section recently, by changing the parameters such as pulling speed, mold electromagnetic stirring, and secondary cooling specific water, the low magnification structure, carbon segregation amount and hardenability before and after changing parameters were compared and analyzed. The results show that when the changed production parameters are used for production, the equiaxed crystal rate decreases slightly, the macro-segregation and hardenability fluctuations decrease significantly, and the product quality improves significantly. In the adjustment and comparison of production parameters, the macro-segregation and hardenability fluctuations under the electromagnetic stirring parameters of the 150 A and 1.5 Hz molds are significantly better than those under the electromagnetic stirring parameters of the 200 A and 1.5 Hz molds. Therefore, the pulling speed is 0.35 m/min, and the water volume of each section in the secondary cooling zone is 40 L/min, 21 L/min, and 13 L/min, 0.134 L/kg specific water volume of the secondary cooling zone, 150 A、1.5 Hz electromagnetic stirring in the crystallizer and 100 A、7 Hz electric stirring at the end, the high hardenability / macro segregation fluctuation of 20CrMnTiH gear steel is improved.
		2023 Vol. 42 (1): 47-54 [Abstract] ( 138 ) [HTML 1KB] [PDF 3082KB] ( 320 )

	55	LI Jie, ZHANG Kun, LI Qiang, ZHANG Kang-hui, HUANG Zhu-ping
		Analysis and optimization of quality defects of HRB400 ribbed steel bar
		Aiming at the problems of rhomboidity and crack of HRB400 continuous casting billet, it was found that quality defects of billet were mainly related to mould vibration parameters, secondary cooling system, foot roll and other factors by tracking and investigating. The rhomboidity rate of billet reduced from 1.5% to 0.1%, the rate of corner crack decreased from 3.2% to 0.6%, the proportion of intermediate crack lower than grade 0.5 increased from 8.3% to 92.6%, and the proportion of central crack lower than grade 0.5 increased from 85.0% to 100% by increasing the stroke of mould from 7.5 mm to 8.5 mm, reducing the cooling water volume of mould from 2 300 L/min to 2 100 L/min, increasing the specific water volume of secondary cooling zone from 1.30 L/kg to 1.56 L/kg, installing the mould foot roll and water baffle, regularly maintaining the nozzle, arc alignment and other measures. The billet quality is significantly improved, the rolling process runs smoothly, and the performance of finished product meet requirements.
		2023 Vol. 42 (1): 55-60 [Abstract] ( 131 ) [HTML 1KB] [PDF 2761KB] ( 416 )

	61	LIN Peng, ZHANG Hong-cai, ZUO Hui, XU Zheng-zhou, ZHAI Wan-li
		Analysis and improvement of surface defects of peritectic steel 15CrMoG billet
		Facing the quality problems of surface sag and longitudinal crack of steel leakage of 200 mm×200 mm continuous casting billet of peritectic steel 15CrMoG, the surface sag and breakout defects of casting billet are analyzed by surface inspection and test comparison. The result indicates that surface sag and longitudinal crack of steel leakage are caused by the uneven heat transfer between the crystallizer copper tube and the slag and the low intensity of secondary cooling. By changing the crystallizer copper tube taper from 0.72%/m to 1.10%/m and the basicity of slag from 0.72 to 1.05 and the viscosity from 0.44 Pa·s to 0.74 Pa·s and the melting temperature from 1 170 ℃ to 1 191 ℃ and the secondary cooling ratio water quantity from 0.30 L/kg to 0.45 L/kg,it improves the cooling heat transfer of the crystallizer and the cooling effect of the secondary cooling section and the cooling uniformity of casting billet. The result shows the defects of casting billet have been effective controlled.
		2023 Vol. 42 (1): 61-65 [Abstract] ( 140 ) [HTML 1KB] [PDF 2339KB] ( 219 )

	66	LIN Hong-liang, SHANG Xiu-ling, SHI Bin-qing
		Precipitation characteristics of the carbides for Mn13 high manganese steel slab during cooling
		After Mn13 steel was produced by continuous casting process in some enterprise, a large number of layered cracks along the central plane appeared after hot rolling, and the cracking ratio was much higher than that of die cast billet. Initial testing results have confirmed that such issue was related to coarse carbide precipitation in the center of the billets. Therefore, it is necessary to focus on the carbide precipitation characteristics of Mn13 steel continuous casting billet during solidification and cooling. In this work, the precipitation behavior of carbides was investigated through Thermo-calc thermodynamic calculation and laboratory heat-treatment simulation. The calculation results show that under the condition of thermodynamic equilibrium, carbides begin to precipitate at 847 ℃, and all carbides precipitate at 557 ℃. The results of microstructure observation show that no visible carbides precipitate from the matrix above 650 ℃. When the temperature is cooled to 550 ℃, the carbide begins to precipitate obviously. The temperature range of 400-550 ℃ is a sensitive temperature range for carbide precipitation, therefore the continuous casting billet should be subjected to rapid cooling to avoid carbide precipitation in this temperature range. In addition, the process practice shows that the adoption of reasonable continuous casting processes (such as proper molten steel superheat, electromagnetic stirring and dynamic soft reduction processes) can also help to improve the central segregation of Mn13 steel billets and reduce the tendency of carbide precipitation in the core during the solidification process of billets.
		2023 Vol. 42 (1): 66-73 [Abstract] ( 128 ) [HTML 1KB] [PDF 3269KB] ( 273 )

	74	NIU Shuai, DENG Wei, WANG De-jiong, HU Zhi-yong, WANG Kai-min, WANG Yu-hang, TANG Hai-yan
		Effect of unsteady casting condition on cleanliness of tire cord steel
		In order to have a sound grasp of the cleanliness level of tire cord steel billet produced in a steel plant under unsteady continuously casting condition, and provide the basis for determining reasonable head and tail billet length and the product classification management during industrial production, the cleanliness difference of the billet cast under unsteady and steady casting conditions was analyzed and the slag-steel interface behavior during tundish filling was studied by using water model method in the present study. The reason for the billet cleanliness difference under the two casting conditions was explained. The results show that: The cleanliness of the tire cord steel billet under the unsteady casting condition is obviously lower than that under the steady casting condition. The T.O and N is 1.76 and 1.23 times higher than that under the steady casting condition. The micro-inclusion and macro-inclusion amount of the unsteady and steady casting condition are 52.89 mm^-2 and 26.1 mm^-2, and 11.49 mg/10 kg steel and 4.36 mg/10 kg steel, respectively. Exposure of molten steel, secondary oxidation and slag entrapment during tundish filling process were found to be some reasons that lead to poor cleanliness of the billets under unsteady casting condition.
		2023 Vol. 42 (1): 74-81 [Abstract] ( 129 ) [HTML 1KB] [PDF 6182KB] ( 190 )

Continuous Casting Equipment

	82	ZHANG Jian-jun, WANG Zi-chao, LIU Qing, DOU Kun
		Influence of SEN configuration on initial solidification in CSP thin slab
		A three-dimensional mathematical model has been developed for the coupled analysis of fluid flow, heat transfer and solidification in Compact Strip Production(CSP) continuous casting mold by using finite element method. Effects of casting speed and Submerged Entry Nozzle (SEN) area proportion on flow pattern of free surface, temperature distribution on slab surface and the growth of solidifying shell were investigated. The results shows that the level fluctuation of molten steel surface decreases from±10.5 mm to ±4.5 mm with casting speed decreasing from 6 m/min to 4 m/min, and the solidified shell thickness at mold exit increases from 7.1 mm to 9.5 mm. When SEN area proportion increases from 1.56 to 2.00, the level fluctuation decreases from ±9.1 mm to ±7.1 mm, and the shell thickness at mold exit reduces by 0.4 mm.
		2023 Vol. 42 (1): 82-88 [Abstract] ( 110 ) [HTML 1KB] [PDF 3612KB] ( 412 )

	89	LIU Yu-hang, SONG Jing-ling, ZHU Qing-gui, LI Heng-hua, NIU Liang, YANG Shu-feng
		Structural optimization of tundish for 30 t symmetrical four-flow small round billet
		In order to optimize the 30 t symmetrical four-strand small round billet tundish in a steel plant, the tundish currently used in the steel plant is used as a prototype, on the basis of similarity principle, the internal flow control device of the tundish is optimized by water model simulation, and RTD curve of the tundish under different conditions is measured, and then calculate the peak time, dead zone ratio and other indicators of molten steel in the tundish. The results show that the metallurgical effect of the prototype tundish is not good. According to the optimization scheme, when two holes are opened on each side of the deflector, the optimal scheme is scheme 3. At this time, the proportion of the dead zone of the tundish is 10.96%. When opening a single hole, the preferred plan is scheme 18. At this time, the proportion of dead zone in the tundish is 8.74%. However, when the smelting of this tundish is completed, the amount of steel left in the tundish is large, and the economic cost is high. On the whole, it is the best to use the double-hole optimal solution.
		2023 Vol. 42 (1): 89-96 [Abstract] ( 104 ) [HTML 1KB] [PDF 4094KB] ( 395 )

	97	ZHOU Chen-yang, HUANG Jun, ZHANG Ya-zhu, WANG Shu-hao, ZHANG Heng
		Study on the optimization simulation of submerged entry nozzle in mold during bloom continuous casting
		In order to study the influence of different immersion nozzle types on the flow field in mold, taking the nozzle optimization of mold as the starting point, two methods of physical simulation and numerical simulation were used to carry out the optimization of different nozzle of 280 mm×380 mm large slab mold. In this study, a 1∶1 mold water simulation test device was firstly constructed to simulate continuous casting flow under different submerged entry nozzle. The mold cross section flow field under different nozzle was measured by PIV. Then, Fluent software was used to further study the influence of parameters such as the opening angle, opening number and installation angle on the flow field and liquid level fluctuation in the mold. Physical simulation and numerical simulation show that when the opening angle is upward, the fluctuation range is more than 5 mm; When the opening angle is horizontal, the impact velocity of narrow surface is too large, reaching 0.35 m/s. The liquid level velocity of four-hole nozzle is 0.22 m/s compared with that of double-hole nozzle, which is lower than the critical velocity value of slag coiling. When the nozzle installation angle is changed to diagonal, the flow in the corner of the internal flow field is strengthened and the flow in the whole flow field is more stable.
		2023 Vol. 42 (1): 97-105 [Abstract] ( 151 ) [HTML 1KB] [PDF 8743KB] ( 200 )

Technology Exchange

	106	ZENG Li, LIU Hang, MEI Ning, LIU Yan-qiang, XIAO Hua-sheng, YANG Chun-bao
		Cause analysis and improvement of poor sealing between slide surface of tundish
		In order to solve the problems of secondary oxidation of liquid steel and steel spilt between plates caused by poor sealing between tundish plates in the production process of continuous casting machine, the influence of quick change mechanism oil cylinder, mechanism slideway, mechanism spring pressure, water mouth baking and water mouth plate surface on sealing effect was analyzed by field tracking system.The results show that the lax sealing between plates is mainly related to the equipment accuracy of the quick change mechanism, the surface quality of the nozzle plate and the baking process operation. By monitoring the slide and spring pressure of the quick change mechanism, optimizing the baking system of the upper nozzle and submerged nozzle, standardizing the flatness of the plate surface, applying graphite emulsion on the plate surface, and implementing fine operation, the sealing performance between tundish plates is greatly improved in the process of continuous casting production, the qualified rate of argon pressure of inter plate seal was increased from 75% to 98%, and the occurrence rate of mold liquid level fluctuation over ±3 mm caused by inter plate suction decreased from 3.0% to less than 0.1%, the steel growth rate between plates is reduced from 1.5% to less than 0.01%.
		2023 Vol. 42 (1): 106-111 [Abstract] ( 140 ) [HTML 1KB] [PDF 2999KB] ( 435 )

	112	LIU Chang-wei, LIU Yong-jun, YUAN Chun-an, CHEN Chao, FU Jun
		Automation transformation and optimization of the assembly and disassembly system of the ladle slide plate oil cylinder
		Aiming at the manual assembly and disassembly station of the slide oil cylinder of the continuous casting machine in the steelmaking plant, a system equipment for robots to replace the manual operation is developed. Combined with the actual environment of the site, through the cooperation of robots, vision systems and related fixtures, the overall scheme of the system is explained, the design principles and structures of related fixtures are expounded, and the robot system is simulated. The automatic installation of the oil cylinder has laid the foundation, and at the same time provides a technical reference for the promotion of the wide application of robot technology. The equipment uses robots to replace labor, which frees the labor from high-intensity work and reduces the corresponding safety risks, making some contributions to the safe production and intelligent manufacturing of the steelmaking plant.
		2023 Vol. 42 (1): 112-117 [Abstract] ( 157 ) [HTML 1KB] [PDF 2808KB] ( 345 )

	118	NING Ying-yi
		Practice and process research of Q235B on beam blank caster
		In order to provide high quality casting billet for section steel and reduce the occurrence of quality defects such as web crack and center loose, the technological conditions in the production process of Q235B were studied, and the mechanism of web crack and center loose of casting billet was mastered. By controlling the composition and purity of molten steel, optimizing the mold cooling and secondary cooling process, optimizing the slag protection process and the water outlet insertion depth, the casting billet can achieve uniform cooling during the solidification process, reduce the surface temperature drop of the casting billet, effectively eliminate the web cracks on the surface of the casting billet, and control the center porosity level of the casting billet below 1.0.
		2023 Vol. 42 (1): 118-123 [Abstract] ( 127 ) [HTML 1KB] [PDF 1484KB] ( 357 )

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