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2022 Vol. 41 No. 4
Published: 2022-08-18
Continuous Casting Technology
Strand Quality
Technology Exchange
Comprehensive Summarization
1
ZHONG Hong-gang, GUO Qiing-tao
Preface
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Comprehensive Summarization
2
PAN Dong, GUO Qing-tao, YU Fu-zhi, XIAO Yu-bao, LI Yu-ting, ZHANG Kai-lun
Research and application progress of electromagnetic induction heating technology in tundish
Tundish is an important connection point of steelmaking process from intermittent operation to continuous operation. It plays a very important role in promoting the diversion and purification of liquid steel, reducing the macro segregation of slab, improving the equiaxed grain rate and slab quality. With the continuous improvement of the requirements for the quality of continuous casting slab and the cleanliness of molten steel, new tundish metallurgical technologies emerge one after another. Among them, electromagnetic induction heating in tundish has the functions of high-efficiency and stable tundish temperature stability and inclusion removal, which is conducive to low superheat constant temperature casting of molten steel and has been gradually used. The application, research status and future development trend of this technology are discussed in detail.
2022 Vol. 41 (4): 2-7 [
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WU Chun-lei, LIU Xiao-ming, LI De-wei, ZHU Xiao-wei, ZHAO Li-jia, WANG Qiang
Study and development on electromagnetic nozzle swirling flow technology in continuous casting
As a novel flow-control technology in the mold, the application of electromagnetic swirling flow in the nozzle (EMSFN) has gradually attracted concern from iron and steel enterprises. Based on the research of the EMSFN technology in recent years, the influence of EMSFN technology on the flow field and temperature distribution in the mold, the optional EMSFN device structure and the metallurgical effect in the industrial application are summarized and analyzed. The effect of EMSFN technology on the quality of continuous casting billet is equivalent to that by using the mold electromagnetic stirring (M-EMS). When the EMSFN technology is applied together with the M-EMS, the solidification structure of the square and round billet can be significantly refined and the macrosegregation can be alleviated. The iron and steel enterprise can select the EMSFN devices with different structures and the optimized nozzle according to the actual site conditions, to meet the quality requirements of continuous casting products in different steel grades.
2022 Vol. 41 (4): 8-15 [
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PENG Jian-fei, ZENG Jie, WANG Wan-lin, CHEN Bo-tao, YANG Wen-zhi
Present situation and prospect of permanent magnet stirring during billet continuous casting
Electromagnetic stirring has become an important technique to improve billet quality in continuous casting process. Compared with the traditional three-phase AC electromagnetic stirring (EMS), the permanent magnet stirring (PMS) based on sintered NdFeB material has the advantages of higher magnetic induction intensity, lower power consumption and simpler structure. The technical characteristics of electromagnetic stirring and permanent magnet stirring are compared and the present application situation of mold and final permanent magnet stirring during billet continuous casting is introduced. It was reported that the mold permanent magnet stirring can effectively improve the surface and internal quality of the billet, reduce the hole defects on the surface, and improve the central porosity and central carbon segregation of the billet. In addition, permanent magnet stirring was applied in the final solidification position of high carbon steel continuous casting rectangular billet. It was found that the center carbon segregation index of the billet decreases obviously with the increase of the rotating speed of PMS, and the energy consumption of PMS per ton of steel was only about 15% of that of traditional EMS.
2022 Vol. 41 (4): 16-20 [
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BAI Qing-wei, XING Shu-qing, CHEN Zhong-yi, LIU Yong-zhen, MA Yong-lin
Research progress of semi-continuous casting of aluminum alloy under pulsed electromagnetic field
The mechanical effect, thermal effect and magnetic potential energy induced by pulse electromagnetic field can significantly improve the microstructure and properties of aluminum alloy semicontinous casting. Meanwhile, pulse electromagnetic casting technology in green production, intelligent control and other aspects closely meet the national strategic requirements of “low-carbon metallurgy”. The research results of pulsed electromagnetic field in casting grain refinement, microstructure evolution and precipitate refinement were reviewed. The coupling mechanism between the properties of pulsed electromagnetic field and phase transformation of materials was analyzed, and a preliminary conception of controlling solidification and precipitation of phase transformation microstructure by pulsed electromagnetic field is put forward to meet the quality requirements of high quality aluminum alloy microstructure. The pulsed electromagnetic field technology of melt surface based on theory and its industrial practice in multi-gauge semi-continuous casting are introduced,such as 7XXX(
φ
203)、6XXX(
φ
380)、Al-Si(
φ
120). Pulsed electromagnetic field is expected to play a greater role in many metallurgical processes such as casting and thermal care in the future.
2022 Vol. 41 (4): 21-26 [
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Continuous Casting Technology
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DUAN Peng-fei, YANG Bin, DENG An-yuan, XU Xiu-jie, WANG En-gang
Steel flow characteristics and structure optimization for slab electromagnetic induction heating tundish
The use of electromagnetic induction heating technology on the tundish can effectively compensate for the temperature drop of the molten steel, realize constant temperature and low temperature pouring. In order to make the electromagnetic induction heating tundish technology suitable for continuous slab casting, a mathematical model for the double-strand slab induction heating tundish was established, and the influence of the induction heating technology on the flow and temperature characteristics in the double-strand slab tundish was studied. The effects of dam structure and channel angle on temperature field and flow behavior of molten steel were investigated. The results show that the channel induction heating technology cannot be directly applied to double-strand slab casting, and it is necessary to optimize the tundish structure. Electromagnetic induction heating can significantly increase the temperature of molten steel in the distribution room of the tundish, but a short-circuit flow will occur. Retaining walls and dam structures are very effective in reducing short-circuit flow and uniformizing the molten steel temperature. When the distance between the dam and the nozzle is 0.5 m, the flow state of the molten steel is the best, and the temperature distribution of molten steel is relatively uniform. From the point of view of the flow behavior of molten steel, adjusting channel expansion angle is not suitable for the double-strand slab induction heating tundish. Through a reasonable heating power mode, the pouring temperature fluctuation can be controlled within 5 K.
2022 Vol. 41 (4): 27-35 [
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36
WANG Zhao-hui, LUO Sen, WANG Wei-ling, ZHU Miao-yong
Multi-physical transport in billet mold of cord steel 82B with electromagnetic stirring
Transport phenomenon of momentum, heat, and solute are very complicated during solidification process of continuously casting billet with mold electromagnetic stirring (MEMS). So, mold electromagnetic stirring has great influence on the billet quality. In order to study the effect of MEMS on complicated transfer phenomenon and understand interactions between them during billet solidification process, a 3D multi-physical fields coupling model for continuous casting process with MEMS was established. Solidification process of cord steel 82B billet in mold with MEMS was simulated with this model. The model was validated by comparison between simulated and measured results. Numerical results show that, as MEMS current increase, flow intensity in mold become stronger, vertical flow velocity at billet center near the exit of mold first decrease, then turn round, and increase continuously. Heat transfer of billet, subcutaneous negative segregation of 82B billet, and solute enrichment in melt pool of 82B billet during continuous casting process are all promoted with increasing mold electromagnetic stirring current. As electromagnetic stirring current is 280 A, maximum tangential velocity of liquid steel along X-axis in cross sections at MEMS center is 0.23 m/s, and minimum mass fraction of carbon at negative zone and mass fraction of carbon in liquid pool at billet center are 0.706% and 0.872% respectively in the cross section 1.5 m away from meniscus
2022 Vol. 41 (4): 36-42 [
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WU Jun-xia, LI Zhuang, MA Dan-zhu, JIAN Wei-wei
Research on freestanding adjustable combination electromagnetic brake
In order to effectively control the molten steel flow and complex multiphase flow behavior in the high casting speed slab mold, a new type of freestanding adjustable combination electromagnetic brake (FAC-EMBr) was introduced. The electromagnetic field characteristics in FAC-EMBr mold and the flow control behaviors of the new type of magnetic field were studied by numerical simulation. The numerical simulation results showed that the uniformly distributed magnetic fields were formed in the upward and downward backflow region and meniscus region of the mold by applying FAC-EMBr, and then the molten steel flow in the three key regions were controlled. Combined action of the horizontal and vertical magnetic poles can significantly reduce the impact strength of the jet on the narrow face of the mold, and reduce the molten steel velocity of upward and downward backflow. Compared with the case without electromagnetic brake and the case with EMBr ruler, the wave height of the meniscus with FAC-EMBr is reduced to 14.5 mm. Even at a high casting speed (2.2 m/min), an effective flow control effect can be obtained with the aplication of FAC-EMBr.
2022 Vol. 41 (4): 43-49 [
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Strand Quality
50
HE Jian-guo, DENG An-yuan, XU Xiu-jie, WANG En-gang
Effect of electromagnetic stirring position on liquid steel flow and liquid level fluctuation in continuous casting mold for wide-thick slab
To reasonably control the flow of liquid steel and the fluctuation of liquid level in the mold of wide-thick slab and improve the quality of slab. The flow and level fluctuation behavior of molten steel in a 2 200 mm×250 mm continuous casting mold was studied by numerical simulation. The effects of electromagnetic stirring position on the flow and liquid level fluctuation were investigated. The results show that the electromagnetic stirring can enhance the flow of molten steel in the upper reflux area, which is beneficial to uniform composition and temperature of molten steel. The electromagnetic stirring can increase the speed of the molten steel near the nozzle by about 0.04 m/s, and fully enhance the stirring of the molten steel near the nozzle. With the stirring position moving upward, the horizontal swirl flow generated by the electromagnetic stirring can enhance the speed of the downward flow, as a result the position of the lower vortex center in the molten pool moves up. The electromagnetic force promotes the horizontal flow of molten steel, which deflects the upward flow and weakens the speed of the upward flow which can reduce the impact of upward flow on the liquid level and the fluctuation of the liquid level. Raising the position of the electromagnetic stirrer is helpful to control the fluctuation of the liquid level. When the center position of the electromagnetic stirrer is
Y
=-0.1 m, the liquid level fluctuation can be reduced from 7.5 mm to less than 3 mm, which can reduce the occurrence of slag entrainment, and the flow field still maintains a good symmetry.
2022 Vol. 41 (4): 50-58 [
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ZHA Quan-chao, DENG Qi-gen, ZHANG Ya-bing, YANG Ren-qiang, LI Hai
PMO improves the central quality of
φ
300 mm round billet of low carbon steel
Pulsed magneto oscillation (PMO) technology was introduced into the continuous caster in Wuhu Xinxing to improve the central quality of
φ
300 mm round billet. The effects of PMO parameters and casting speed of continuous caster on the quality of low carbon 20 steel round billet are explored. The results show that the radial carbon distribution of 20 steel billet can be significantly reduced by using appropriate PMO parameters. The carbon range is 50% lower than that of the billet without PMO treating, and the effect is stable. Moreover, when the casting speed of the continuous caster was increased from 0.75 m/min to 0.85 m/min, the quality of billet without PMO treatment became unqualified, and the carbon range reached to 0.12%. Whereas the billets treated with PMO still maintained high central quality, carbon content range was 0.03%, and the production efficiency was increased by 13.3%.
2022 Vol. 41 (4): 59-65 [
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LI Hui-cheng, YANG Pu, LIU Hai-ning, XU Zhi-shuai, DOU Nai-yuan, LI Li-juan
Application of PMO-EMS combined control to improve the homogenization of casting billet
Pulsed magneto-oscillation(PMO) is an original homogenizing technology to refine the solidification structure and improve the homogenization of billets by promoting nucleation and forming grain rain. The production and application practice show that this technology has a significant effect on improving equiaxed grain ratio and reducing macrosegregation index of billets. In this study, an optimal combination of PMO and EMS was used to promote nucleation and form the “grain rain” effect and the stirring effect of EMS. The “grain rain” formed by PMO was dispersed evenly in the center of the billet, eliminating the eccentricity of equiaxed grain zone, thus greatly improving and stabilizingthe symmetry of solidification structureand homogenization effect of a billet and its stability. The results show that the application of PMO-EMS combined processcan significantly improve the homogenization of billets, and the central carbon of bearing steel GCr15 and gear steel 20CrMnTi can be controlled within 1.04 and 1.05, respectively.
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Technology Exchange
72
LUO Yan-zhao, HE Wen-yuan, WANG Shao-jun, ZHOU Hai-chen, JI Chen-xi, LI Hai-bo
Application of fluid control mold on low carbon steels at 2.05 m/min high speed slab continuous casting
The high-speed slab continuous casting has attracted more and more attention because of its advantages of reducing equipment investment, increasing production and efficiency and reducing material consumption. In order to solve the problem of matching the casting cycle and refining cycle of low carbon steel and further improve the production efficiency. Some steel plant has carried out the research on the high-speed continuous casting process technology of optimizing the electromagnetic braking parameters of the mold. After applying the magnetic field, with the increase of the upper coil current from Type A to Type C, the surface velocity of molten steel in the mold is reduced from 0.35 m/s to 0.21 m/s, the electromagnetic braking can significantly reduce the surface velocity at high casting speed. With the increase of argon blowing flow from 12 L/min to 20 L/min, the surface velocity of molten steel increases. With the increase of nozzle immersion depth, the flow field shape in the mold does not change significantly. The inclusion index at 2.05 m/min is significantly lower than that at 1.8 m/min.
2022 Vol. 41 (4): 72-77 [
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MA Zhi-min, WANG Jia-hui, FANG Qing, XIAO Hong, YI Bing, ZHANG Hua
Physical simulation on optimization of baffles in an induction heating tundish
The continuous casting process of special steel has strict requirements for the uniformity and cleanliness of liquid steel in the tundish equipped with channel induction heating technology. In this paper, aiming at the four-strand two-channel induction heating tundish of a steel plant in China, the flow field and Residence Time Distribution(RTD) curves in the tundish under the schemes of prototype (without a baffle), V-type baffle and trumpet-type baffle were investigated and compared by the water model experiments to obtain the optimum designation of baffle and diversion hole for the tundish. The research results showed that the tundish applying the trumpet-type baffle appears great advantages over the V-type baffle in terms of more average residence time and less volume fraction of dead zone. The optimum scheme is case A2, in which two diversion holes are applied on each wall of the trumpet-type baffle. The average residence time is 707.7 s, and the dead zone volume fraction is 11.86%. Compared to the cases of the prototype (without a baffle), the V-type baffle equipped with four diversion holes (Case B1 and Case B2) and two diversion holes (Case C1 and Case C2) on each wall, the average residence time under the Case A2 is prolonged by 223.4 s, 122.1 s, 117.2 s, 85.3 s, 68.4 s, and the dead zone volume fraction is reduced by 18.28%, 15.24%, 14.59%, 10.64%, 8.52%, respectively.
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