Large Eddy Simulation of Transient Flow, Particle Transport, and Entrapment in Slab Mold with Double‐Ruler Electromagnetic Braking

Casting is the final step of steel from liquid to solid state with a decreased steel temperature, where some complex phenomena occur in casting mold, as shown in Figure 1, [1] such as multiphase flow, heat transfer, phase transition, solute redistribution, and so on. During solidification process, some defects of steel semi-product like cracks and macrosegregation can form, which can significantly deteriorate steel mechanical properties. These defects normally are difficult to be completely removed in a subsequent heat treatment process. Therefore, a good control on steel solidification process is of great significance for both steel quality and casting efficiency.Steel casting includes two routes, namely continuous casting and ingot casting. According to statistics from World Steel Association, the global output of crude steel in 2020 is around 1.878 billion tons, over 96.9% of which is produced through continuous casting process. [2] Therefore, continuous casting has become the main process in global steel production. However, ingot casting is still used today to produce, for example, some high-alloyed steel, large size round bloom, and so on, which also plays an important role in production of some steel categories. In past years, steel casting process especially continuous casting has made enormous progress. These are realized by optimizing the submerged entry nozzle (SEN) structure, [3][4][5] casting speed, [6][7][8] argon blowing in nozzle, [9][10][11] electromagnetic braking, [12][13][14] mold electromagnetic stirring (M-EMS), [15][16][17] second-cooling segment electromagnetic stirring (S-EMS), [18][19][20] final electromagnetic stirring (F-EMS), [21][22][23] and so on. To further improve the steel flow field in mold, as early as 1994, Yokoya et al. [24] first proposed the swirling flow nozzle casting technology, which aims to induce a rotational steel flow inside SEN. This rotational flow momentum can change SEN outlet flow pattern to avoid the formation of a jet flow in mold that is commonly observed in the case of the straight nozzle continuous casting. [24] Furthermore, it can also promote a uniform flow on the cross-section of SEN side port. Therefore, the mold flow pattern can be optimized as soon as steel moves into the mold. Plant trials have confirmed that this technology can effectively improve the quality of steel semi-product and alleviate the SEN side-port clogging in continuous casting. [25] In recent years, the swirling flow nozzle casting technology has attracted worldwide attention. A great number of studies have been carried out, as shown in Table 1, and these studies will be comprehensively introduced in Section 2 and 3 in this paper, including different realization technologies, main findings, and metallurgical effects. This aims to promote the understanding of multiphysical phenomena induced by the swirling flow. Also, new technology development and research progress on swirling flow steel casting will be summarized. Swirling Flow Continuous Casting Swirl Blade TechnologyIn 1994, Yoko...

Section: Numerical Models To Simulate Swirling Flowmentioning

confidence: 99%

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confidence: 99%

A Review on Swirling Flow Casting Technology in Steel Production

Xie

Nabeel

Ersson

et al. 2021

“…Argon gas injection (AGI) is widely employed to prevent submerged entry nozzle (SEN) clogging in the slab mold. [1,2] After entering the mold, argon bubbles alter the flow pattern, promote inclusion floating, and improve the melting of mold flux. [1][2][3][4] However, a large amount of argon gas can lead to increased level fluctuations, uneven distribution of mold flux, and even slag entrainment.…”

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confidence: 99%

“…[1,2] After entering the mold, argon bubbles alter the flow pattern, promote inclusion floating, and improve the melting of mold flux. [1][2][3][4] However, a large amount of argon gas can lead to increased level fluctuations, uneven distribution of mold flux, and even slag entrainment. [1,3,5] Moreover, argon bubbles may be captured by the solidified shell and become surface defects.…”

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confidence: 99%

“…[6,7] Fortunately, the aforementioned negative effects can be reduced by suitable operating parameters and electromagnetic technologies to meet quality requirements. [2,3,[8][9][10] Because of these beneficial effects, AGI is used in the bloom mold of Hebei Iron & Steel Group Hansteel Company, [11] Angang Steel Company Limited, [12] Nanjing Iron and Steel Company Limited [13] to improve the castability of alloy steels that are prone to clogging. However, due to the small cross-sectional area of the bloom mold, surface defects from captured bubbles are more serious.…”

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confidence: 99%

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Numerical Simulation for Two‐Phase Flow, Heat Transfer, and Inclusion Transport in Bloom Mold Considering the Effects of Argon Gas Injection and Mold Electromagnetic Stirring

Xuan

Chen

2022

During the continuous casting process, the fluid flow is a critical factor that affects the heat transfer and the inclusion transport, which, in turn, determines the final quality of steel products. Argon gas injection (AGI) is widely employed to prevent submerged entry nozzle (SEN) clogging in the slab mold. [1,2] After entering the mold, argon bubbles alter the flow pattern, promote inclusion floating, and improve the melting of mold flux. [1][2][3][4] However, a large amount of argon gas can lead to increased level fluctuations, uneven distribution of mold flux, and even slag entrainment. [1,3,5] Moreover, argon bubbles may be captured by the solidified shell and become surface defects. [6,7] Fortunately, the aforementioned negative effects can be reduced by suitable operating parameters and electromagnetic technologies to meet quality requirements. [2,3,[8][9][10] Because of these beneficial effects, AGI is used in the bloom mold of Hebei Iron & Steel Group Hansteel Company, [11] Angang Steel Company Limited, [12] Nanjing Iron and Steel Company Limited [13] to improve the castability of alloy steels that are prone to clogging. However, due to the small cross-sectional area of the bloom mold, surface defects from captured bubbles are more serious. [12] As a widely used electromagnetic technology, mold electromagnetic stirring (M-EMS) can enhance molten steel flow, [14] promote superheat dissipation, [15] and improve the equiaxed crystals ratio, [16] more importantly, it can reduce bubbles captured by the solidified shell in the slab mold [17][18][19] and the bloom mold. [12] Despite these advantages of M-EMS, the double action of M-EMS and AGI may cause more level fluctuations, which has been reported in the slab mold [20] but not in the bloom mold. Therefore, to provide theoretical guidance for quality improvement and AGI application, it is essential to investigate the effects of AGI and M-EMS on fluid flow, temperature distribution, and inclusion removal in the bloom mold.Many experimental researches have been performed to investigate the two-phase flow of molten steel and argon gas in the SEN and mold regions using water models [21][22][23][24][25] and liquid metal models. [26][27][28][29] In the water model, it is easy to capture the twophase flow but difficult to consider the effect of the magnetic field because of the low electrical conductivity of water. Although the liquid metal model can apply the magnetic field, the two-phase flow in the mold is hard to visualize. Thus, numerical simulation is widely used to investigate the two-phase flow in the mold. Several studies investigated the effect of AGI on the flow field, [3,7,[30][31][32][33] temperature distribution, [3,30] initial solidification, [3] inclusion removal, [7,31,33] and slag-steel interfacial behavior, [1,4,5,32]

Modeling Asymmetric Flow in the Thin‐Slab Casting Mold Under Electromagnetic Brake

Vakhrushev

Kharicha

Karimi-Sibaki

et al. 2022

Continuous casting (CC) is nowadays the world‐leading technology for steel production. The thin slab casting (TSC) is featured by a slab shape close to the final products and a high casting speed. The quality of the thin slabs strongly depends on the uniformity of the turbulent flow and the superheat distribution, defining the solid shell growth against a funnel‐shaped mold. In most studies, it is commonly assumed that the submerged entry nozzle (SEN) is properly arranged, and the melt inflow is symmetric. However, the misalignment or clogging of the nozzle can lead to an asymmetric flow pattern. Herein, the asymmetry is imposed via a partial SEN clogging: a) a local porous zone inside the nozzle reflects the presence of the clog material; b) the resistance of the clog is varied from low to high values. The solidification during TSC is modeled, including the effects of the turbulent flow. The variation of the flow pattern and the solidified shell thickness are studied for different permeability values of the SEN clogging. These effects are considered with and without the applied electromagnetic brake (EMBr) using an in‐house magnetohydrodynamics (MHD) and solidification solver developed within the open‐source package OpenFOAM.