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	2022 Vol. 41 No. 3
	Published: 2022-06-18



	Continuous Casting Technology Strand Quality Continuous Casting Equipment Technology Exchange

Continuous Casting Technology

	1	LIU Yan-bin, TANG Hai-yan, WANG Kai-min, MA Yu, SHANG Guang-hao, ZHANG Li-ping, ZHANG Jia-quan
		Effect of submerged entry nozzle structures on liquid surface flow behavior of slab continuous casting mold
		Aiming at the phenomena of mold powder involvement and warping defects in the surface of stainless steel strip products, the correlation between the flow behavior of molten steel in the continuous casting mold and the involved process parameters of submerged entry nozzle was experimentally studied based on the actual production conditions. A water model of geometrical ratio 0.65∶1 was set up based on similarity principle, and the hydrodynamic behavior of mold liquid level under different submerged entry nozzle structures and casting process parameters was evaluated and optimized. The effects of casting speed, nozzle immersion depth, side port upward angle (4°, 8°, 15°) and nozzle port shape (rectangular and inverted trapezoid) on the mold level fluctuation and surface velocity were studied experimentally. The results show that the influence of casting speed and immersion depth on liquid level fluctuation is greater than that of nozzle structure. The increase in casting speed and the decrease in nozzle immersion depth aggravate the fluctuation of liquid level in the mold obviously. With the nozzle upward angle increasing from 4° to 8° and 15°, the flow velocity on the mold surface tends to drop, and the jet flow impact depth decreases, which results in an increasing mold level fluctuation at the meniscus. It has been revealed that the appropriate nozzle structure is an inverted trapezoidal one with upward angle of 8°. At casting speed of 1.10 m/min and nozzle immersion depth of 110-120 mm with the recommended nozzle, its measured wave height of mold liquid level is 1.1-1.2 mm and the average surface velocity is around 0.103 m/s. Meanwhile, the optimized scheme is compared with the original scheme by numerical simulation, showing that the liquid level of the optimized scheme is relatively stable and the probability of the shearing slag entrapment is low.
		2022 Vol. 41 (3): 1-10 [Abstract] ( 140 ) [HTML 1KB] [PDF 5315KB] ( 260 )

	11	GAO Jiang, LIU Qing, LI Quan-hui, SUN Jian-kun, TAO Biao, ZHANG Jiang-shan
		Effect of wall design on fluid flow inside a four-strand T-type tundish
		The design of retaining wall plays an important role in fluid control of T-type tundish. In this paper, the influence of retaining walls with different diversion holes on the mixing of molten steel and the consistency of each outlet in a four-strand tundish of a steelmaking plant were studied by using the experimental method of “stimulus-response” hydraulic simulation. The results show that the ratio of dead zone is at a relatively low level under the prototype tundish, and there is a big difference between the response time of far outlet and near outlet, and the flow pattern of liquid steel will deteriorate with the increase of flow rate. By reducing the diameter of the diversion hole and designing an upward angle of 45°, the optimized scheme produces a large circulation structure inside the tundish and prolongates the response time of the near flow outlet, which brings forth the increase of plug volume from 6.61% to 9.04%. The consistency index of each outflow is reduced from 22.8 to 9.6 by 58%, and the dead zone ratio is slightly reduced, which is conducive to improving the overall metallurgical performance of the tundish.
		2022 Vol. 41 (3): 11-17 [Abstract] ( 104 ) [HTML 1KB] [PDF 2684KB] ( 236 )

	18	LIU Tong-wei, ZHANG Yan-chao, ZHANG Cai-jun, ZHAI Jin-jun
		Study on fluctuation behavior of mold steel slag surface under blowing conditions
		In order to reveal the behavior of the steel-slag interface of the mold under different process conditions, a mold with a section of 1 000 mm×230 mm is numerically simulated by Fluent fluid mechanics software. The effects of different casting speeds (0.9-1.5 m/min), nozzle angle (12°-15°) and argon blowing rate (0-6 L/min) on the speed and wave height of the mold steel-slag interface were analyzed. The simulation results show that when the argon blowing rate 4 L/min, the increase of the casting speed will reduce the disturbance of the steel-slag interface floating on the argon bubble near the submerged entry nozzle, but the wave height near the narrow surface of the mold will increase with the increase of the casting speed. The fluctuation of the interface is aggravated, the fluctuation near the narrow surface is smoothed by the increase of the consumption of the turbulent energy of the steel liquid from the floating argon bubble, the nozzle angle has a greater influence on the steel-slag interface, the nozzle angle is smaller, the floating distance of the argon bubble is shorter, and the wave height and speed are relatively large around the nozzle and near the narrow surface.
		2022 Vol. 41 (3): 18-24 [Abstract] ( 125 ) [HTML 1KB] [PDF 4099KB] ( 264 )

	25	YIN Pan, YUAN Ji-bai, LI Xiu-jie, ZHAO Hong-liang
		Effects of different forms of turbulence inhibitor on tundish metallurgical
		The distribution of steel flow and temperature in steady state was calculated under the condition of four different structure turbulence inhibitor with a six-stream T-shaped symmetrical tundish as the prototype, meanwhile the mixing characteristics of molten steel were analyzed quantitatively by RTD curve in different case. Multi-phase flow modle was adapted during ladle change period to trace slag-steel interface fluctuation in tundish. In order to discuss the effects of different forms of turbulence inhibitor on molten steel flow from different sides. The results show that different structure turbulence inhibitor affect tundish metallurgy variously, each has its advantages and disadvantages in different perspective. The “Ink bottle shape” turbulence inhibitor has the best performance in aspect of refractory material service life and interface fluctuation.
		2022 Vol. 41 (3): 25-31 [Abstract] ( 113 ) [HTML 1KB] [PDF 3476KB] ( 195 )

Strand Quality

	32	XIAO Nian-gen, WANG Xue-lin, ZHONG Hua, DENG Ai-jun, CAO Rui-hong, WANG Hai-chuan
		Experimental study and application of desulfurizer by slag infiltration
		It wanted to study and solve the quality problem of cracks in microalloyed steel due to excessive sulfur content, the composition design of desulfurizer for slag infiltration of ship plate C36-1 was studied by using multi-factor and multi-level orthogonal regression test method, and the composition design model of desulfurizer was established according to the basic laboratory experimental data. The results showed that when the w(CaO)=42%-55% in desulfurizer, the effect on desulfurization rate was more obvious. w(Al₂O₃)<35%, w(CaC₂)=12% is appropriate. After industrial production test, the final determination of the components of desulfurizer was w(CaO)=42%-55%、w(Al₂O₃)=30%-35%、w(CaC₂)=8%-12%、w(CaF₂)=8%-10%. The industrial average desulfurization rate of the desulfurizer reached 80.93%. The new desulfurizer can stably control the sulfur content of ship plate steel to less than 0.010%. The failure rate of slab crack was reduced by 85%. It met the process demand of sulfur control for this kind of steel and increased the economic benefit of the enterprise.
		2022 Vol. 41 (3): 32-38 [Abstract] ( 97 ) [HTML 1KB] [PDF 1424KB] ( 253 )

	39	ZHAN Mei-zhu, WANG Sheng-dong, ZHANG Li-feng, CHEN Wei
		Effect of casting speed on inclusions in continuous casting slab of peritectic tinplate steel
		In order to study the effect of increasing casting speed on inclusions in continuous casting billet of peritectic tinplate, the distribution of inclusions in continuous casting billet of peritectic tinplate at different casting speed was studied by automatic scanning electron microscope.The results show that when the casting speed of peritectic tinplate is increased from 1.3 m/min to 1.4 and 1.5 m/min, the proportion of liquid level fluctuation greater than 3 mm is less than 0.40%. The average number density of inclusions larger than 3 μm at the quarter of the thickness of the continuous casting slab with the 1.4 m/min and 1.5 m/min was 1.15 per mm² and 1.36 per mm². The inclusion average area fraction was 0.001 9% and 0.002 4%, which were lower than the value with a 1.3 m/min casting speed. When the casting speed increased from 1.3 m/min to 1.5 m/min, the mold level was controlled smoothly and the number density and area percentage of the inclusions larger than 10 μm on the surface of the continuous casting slab showed a decreasing trend. Finally, the industrial production of peritectic tinplate with high casting speed and stability is realized.
		2022 Vol. 41 (3): 39-44 [Abstract] ( 109 ) [HTML 1KB] [PDF 2140KB] ( 221 )

	45	GAO Long-yong
		Control measures and formation mechanism about edge-crack of hot-rolling coil of midium carbon steel
		In order to study the formation mechanism of crack defects in the hot rolling of medium carbon steel, the corresponding process control measures were formulated to reduce the down grade rate of cracks in the hot rolling of medium carbon steel. Metallographic observation, SEM analysis were carried out by sampling the defect of hot rolled coil of medium carbon steel, and comparative rolling test was also carried out. The results show that the peak crack at the edge of hot rolling medium carbon steel is caused by the transverse crack at the corner of continuous casting slab, which extends after rolling. The formation of edge lines is caused by the folding of narrow surface to wide surface during rolling process. According to the research results, by adjusting the composition of medium carbon steel, improving the accuracy of caster, optimizing the secondary cooling water distribution, applying chamfering mould and dynamically adjusting the taper of mould, the down grade rate of cracks in medium carbon steel hot rolling coil is reduced to less than 0.10%, with a decrease of 90.59%. The improvement effect is very obvious.
		2022 Vol. 41 (3): 45-50 [Abstract] ( 153 ) [HTML 1KB] [PDF 3045KB] ( 209 )

	51	LIU Liang
		Analysis and control over formation cause of surface longitudinal crack for continuous casting bloom of sulfur bearing steel
		In view of the problem of surface longitudinal crack of sulfur-containing steel in bloom, metallographic and energy spectrum observations were made on the crack defects, and it was found that the longitudinal crack occurred after casting bloom out of mold. Through high temperature thermoplastic test determine the range of precipitation and organization, and analyses the influence of sulfur in steel high temperature thermoplastic and organizational precipitation range, the influence of the identified under 900 ℃ the third brittle interval, the formation of austenite grain boundary proeutectoid ferrite weaken the intensity of grain boundary, the thermal stress and organization stress, mechanical straightening stress under the influence of grain boundary cracking occurs. It is the root cause of longitudinal cracks on the surface of steel containing sulfur. On this basis, the optimization of protective slag, reconstruction of secondary cooling zone, heating of casting slab and heat preservation of pile cooling process were carried out. The results show that the longitudinal cracks on the surface of the bloom containing sulfur steel can be well controlled by increasing the basicity of protective slag, reducing the melting point and viscosity of protective slag, extending the length of secondary cooling zone, standardizing heating and cooling process. The grinding rate of round steel caused by longitudinal cracks was reduced from 20% to less than 5%.
		2022 Vol. 41 (3): 51-55 [Abstract] ( 144 ) [HTML 1KB] [PDF 2202KB] ( 276 )

Continuous Casting Equipment

	56	LI Hua-gang
		Design and application of electromagnetic stirring roll for slab continuous casting machine
		The finite element analysis software is used to design the magnetic circuit structure and application parameters of the slab casting electromagnetic stirring roller. According to the roll chart of the continuous caster, the installation position of the electromagnetic stirring roll of the casting flow and the equiaxed crystal rate under each process parameter are calculated. On the basis of satisfying the installation space, the parameters such as the optimal ampere-turns, magnetic field strength, electromagnetic force, temperature distribution of each component of the stirring roller, and the amount of deformation of the roller sleeve under a certain iron core size are calculated. The simulation results show that the electromagnetic stirring roller installed in the No.1 and No.9 positions of the sector section 1 can obtain an equiaxed crystal rate of 47.6%-61.6%. Under the size of the roller sleeve diameter of 240 mm, combined with the winding space and installation space, the maximum size of the iron core is 127 mm, and the maximum current under this iron core size is 400 A. The calculated temperature distribution of the stirring roller and the deformation of the roller sleeve guide the design of the cooling water volume and the mechanical structure of the project. The experimental results show that the magnetic induction intensity of the numerical simulation is basically consistent with the magnetic field intensity of the actual test. Through the actual operation results, it is found that the designed cooling water volume meets the cooling requirements. When casting 400 series stainless steel slab with a pouring cross-section of 200 mm×1 000 mm, when the drawing speed is 0.9 m/min, the equiaxed crystal rate of the slab is 55%, which is basically consistent with the design value. The simulation results correctly guide the design and application of the electromagnetic stirring roll for slab casting.
		2022 Vol. 41 (3): 56-64 [Abstract] ( 196 ) [HTML 1KB] [PDF 5112KB] ( 267 )

	65	WANG Zhi-zheng, ZHONG Peng, WANG Huan
		Optimization of tundish system for double-flow slab caster
		In order to improve the quality of billet and reduce the surplus of tundish casting, the tundish inner cavity, the structure of tundish cover, the position of continuous temperature measurement, and the control of unsteady tension speed were optimized. Through the production verification in the factory, the average molten steel residual in the tundish of quick change is reduced from 17.5 t to 15.5 t, the average molten steel residual in the tundish of single open stop is reduced from 13.5 t to 12.5 t, and the continuous casting rate is increased by 0.12%. The qualified rate of IF steel with nitrogen increasing less than 0.000 5% in tundish increased from 76.8% to 82.3%. Inclusion defect sealing rate and correction rate decreased 36% and 30%, respectively. The quality of billet is improved effectively and the cost of continuous casting is reduced.
		2022 Vol. 41 (3): 65-70 [Abstract] ( 137 ) [HTML 1KB] [PDF 2719KB] ( 186 )

Technology Exchange

	71	LIU Chang-wei, ZOU Zhuo-ming
		Application of robot automatic mould fluxes adding technology in Ningbo Iron and Steel Works
		The principle of adding mold flux is to add less and frequently, however traditional manually way is hard to meet this requirement. In order to achieve the goal of adding flux less and frequently, uniformly and controllable, Ningbo Iron and Steel Co., Ltd has developed the robot automatic mold flux feeding system through cooperation with professional manufacturers, which has been put into mass production practice, and carried out by various research methods such as experimental method and quantitative analysis method for more than one year. The practice results show that the robot automatic flux adding technology can meet the principle of adding less and frequently. After the application of this technology, the probability of flux slagging can be significantly reduced, and the goal of adding flux uniformly and continuously can be achieved, which is conducive to reducing the risks of bonding, longitudinal cracks and so on.
		2022 Vol. 41 (3): 71-75 [Abstract] ( 244 ) [HTML 1KB] [PDF 3227KB] ( 238 )

	76	ZHOU Gan-shui, ZHANG Hai-yang, NING Shu-guang, SUN Jun, CHEN Yang, XIAO Hai-jian
		Application of online hot width adjustment in four slab casters at FENGNAN
		The technology adopts the performance of hydraulic adjustable wide soft clamping mechanism and hydraulic equipment, high-speed hot wide process (HS-WAM) control model, through the optimization improvement crystallizer launched narrow surface copper plate position calibration and target width adjustment method, production method and the mould taper during high speed hot wide when adjusting process parameters, such as good practice effect is obtained.Before the mold is on-line, when the mechanical clearance is more than 0.5 mm, the taper adjustment accuracy can still be controlled within ±0.2 mm, and the calibration and adjustment time is short. During the coning period of mold, the adjustment accuracy can reach ±0.2 mm, and the average adjustment interval is more than 30 min. S mode can realize high-speed thermal width adjustment operation, The wedge billet is short and the cast billet is of good.
		2022 Vol. 41 (3): 76-82 [Abstract] ( 115 ) [HTML 1KB] [PDF 4290KB] ( 191 )

	83	FU Qiang, HE Ying-li, LIU Zhen-hai
		Research and practice of shortening process time of 120 t top and bottom compound blowing converter
		In order to increase the converter capacity, effectively reduce the cost consumption, and realize the reduction of consumption and increase of efficiency, cost and increase of efficiency, increase of quality and increase of production and increase of efficiency, Beiying steel plant promotes the converter process optimization under the existing equipment and process conditions, by means of increasing the oxygen supply intensity, optimizing the combined blowing process and smelting with less slag, the converter process time and smelting cycle can be shortened by about 5 min/furnace, and some technical indexes have reached the best level in history, the oxygen supply intensity and carbon-oxygen deposition of the combined blowing are close to the advanced level in China.
		2022 Vol. 41 (3): 83-88 [Abstract] ( 118 ) [HTML 1KB] [PDF 1837KB] ( 234 )

	89	XIE Jian-fu, SUI Ya-fei, DENG Zhi-xun, LIANG Yuan-dong, CHEN Fo-wang
		Cause analysis of edge defects of 09CrCuSb hot rolled coil
		In order to solve the problem of edge delamination during slitting and trimming of 09CrCuSb acid resistant steel hot rolled coil, three typical edge defects of 09CrCuSb hot rolled coil, namely edge delamination, side bulge on the edge end and longitudinal crack on the edge end parallel to the rolling direction are studied by metallographic microscope and SEM-EDS analyzer. The results show that the edge delamination defects are actually caused by hot rolled side guide extrusion, and do not occur again after correcting the side guide position. The key to determine the cause of edge delamination defects lies in the inner surface state of delamination defects. The side bulge is due to the edge and corner crack of the slab caused by the accuracy deviation of the continuous caster. The deviation of the arc alignment and roll gap of the continuous caster is controlled within 0.5 mm, and the defect incidence is reduced from 5.4% to less than 0.2%. The side bulge defect is actually the initial form of hot rolling roll edge. The longitudinal crack on the edge end is due to the cluster bubbles on the narrow edge of the continuous casting slab and the strong crack sensitivity of the steel itself. By reducing the argon of the continuous casting stopper and nozzle to 4-6 L/min and controlling the crack sensitive elements according to the standard lower limit, the defect occurrence rate is reduced from 8.7% to 0.45%. It provides a reference for controlling the defects of 09CrCuSb hot rolling coil.
		2022 Vol. 41 (3): 89-96 [Abstract] ( 141 ) [HTML 1KB] [PDF 6711KB] ( 192 )

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