Control of Macrosegregation Behavior by Applying Final Electromagnetic Stirring for Continuously Cast High Carbon Steel Billet

Xiao, Changfa; Zhang, Jiongming; Luo, Yanzhao; Wei, Xinlei; Wu, Lian; Wang, Shun-xi

doi:10.1016/s1006-706x(13)60190-9

Cited by 30 publications

(18 citation statements)

References 7 publications

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“…Currently, many actions have been taken to improve the internal quality of casting billets, such as electromagnetic stirring (EMS) [17][18][19][20][21][22][23], soft reduction, etc. Most of the actions taken are to enlarge the equiaxed zone and dismiss the shrinkage so that the segregation could be inhibited effectively [24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Effect of Solidifying Structure on Centerline Segregation of S50C Steel Produced by Compact Strip Production

Liu

Cheng

et al. 2021

Coatings

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Medium-high carbon steels having a high quality are widely used in China. It is advantageous to produce high value-added hot-rolled plates with the crystal refined and chemical composition homogenized in the casting slabs. However, element segregation occurs easily during high-medium carbon steels’ production. Generally, the centerline segregation is improved by enlarging the equiaxed zone with low-superheat casting and electromagnetic stirring (EMS). Studies were conducted on centerline segregation of S50C steel slabs with a thickness of 52 mm produced by the compact strip production (CSP) process in China without EMS equipped. By sampling along the width at different position, the secondary dendrite arm spacing (SDAS) was measured after etching and picture processing, based on which the cooling rate was calculated. It was found that the cooling rate increased from the center to the surfaces of the slabs ranging in 1~20 K/s, 10 times faster than that of a conventional process. The faster cooling rate led to a refined solidifying structure and columnar dendrite through the center of the slabs. The SDAS tended to increase from surfaces to the center, ranging only 32~120 μm smaller than that of a conventional process in 100~300 μm, indicating a finer solidifying structure by the CSP process. Results by EPMA indicated that elements C, Si, and Mn distribute in dispersed spots, increasing towards the center, and the centerline segregation changed in a narrow range: for C mainly in 1.0~1.1, Si in 0.98~1.08, Mn in 0.96~1.02, respectively, meaning a more chemical homogenization than that of thick slabs. Elements’ segregation originated from solute redistribution between solid and liquid. According to thermodynamic calculation, δ region of S50C is so narrow that the solute redistribution mainly occurred between γ-Fe and liquid during solidification. As the equilibrium partition coefficient of element C was the smallest, it was easy for C to be rejected to the residual liquid in the inter-dendritic space, leading to obvious segregation, relatively. Besides, as a result of high-cooling intensity, the solidifying structure became so fine that the Fourier number increased and the volume of the residual liquid decreased, making centerline segregation alleviated effectively both in volume and degree. Although bulging was observed during the industrial experiment, the centerline segregation was still inhibited obviously as the refining solidifying structure with permeability ranged only in 0.1~2.3 μm2 from the surfaces to centerline, which showed a good resistance on the residual flow towards the centerline.

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Section: Introductionmentioning

confidence: 99%

Effect of Solidifying Structure on Centerline Segregation of S50C Steel Produced by Compact Strip Production

Liu

Cheng

et al. 2021

Coatings

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“…Today, it is difficult to expect an answer on the basis of a theoretical model only, and, therefore, experimental tests are still very relevant, both on a laboratory scale and an industrial scale. The published information [4][5][6][7][8][9] concerning the positive influence of electromagnetic stirrers on the reduction of carbon segregation in the continuous steel casting process shows that the mentioned direction of actions is very promising.…”

Section: Introductionmentioning

confidence: 99%

Method of Verification of Carbon Segregation Ratio Determined with Experimental Methods

Falkus

Miłkowska-Piszczek

Krajewski

et al. 2020

Metals

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The problem of macrosegregation of alloying elements occurring during cast strand solidification in the continuous casting process is still valid; it is the subject of numerous experiments and theoretical considerations. A large percentage of this research is dedicated to carbon segregation, which, for understandable reasons, is vital for the production of high-carbon steels. The background knowledge on the mechanism of segregation occurrence indicates that it is a very complex effect, and a broad range of factors influencing the continuous casting process need to be considered. Therefore, it is difficult to translate information (provided by complex models of metal flow through a diphase area at the solidification interface of a cast strand) into practical engineering recommendations to reduce the macrosegregation effect. The presented study shows the latest research related to the carbon macrosegregation effect for selected high-carbon steel grades cast with a continuous caster. Problems related to the recording of the effect concerned have been pointed out. The second part of the paper presents the influence of selected casting parameters on carbon macrosegregation intensity when casting 160 × 160 billets with a six-strand caster. In this case, the main subject of the research was the influence of the casting speed on macrosegregation intensity. In the following step, an attempt was made to find the relationship between the cast strand structure and the distribution of carbon content on its cross-section. The ultimate objective of the presented study was to find an answer to the question on the technological capabilities of restricting the segregation effect.

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“…However, secondary cooling and F-EMS are conventionally treated as two independent technologies without considering their interaction, and their parameters are generally optimized separately [2][3][4]. In the conventional model, secondary cooling water flows are determined by steel grade and size of billet and optimized as functions of casting speed for a specific caster.…”

Section: Introductionmentioning

confidence: 99%

“…According to the changing situation, if stirring parameters remain unchanged, obviously the F-EMS cannot play a proper role to keep the stability of solidification or even cause side effects. However, to keep the stability of the liquid core just by adjusting the secondary cooling water flows, that may lead to excessive temperature deviations from the target value and cause cracks and other quality problems [2]. Otherwise, if stirring parameters change according to the size area of the liquid core at F-EMS position without adjusting the water flows, as the liquid core is too big or too small, FEMS also cannot achieve its proper role.…”

Section: Introductionmentioning

confidence: 99%

Coordinated Optimal Control of Secondary Cooling and Final Electromagnetic Stirring for Continuous Casting Billets

Yang

et al. 2020

Journal of Control Science and Engineering

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Secondary cooling and final electromagnetic stirring (F-EMS) are both key technologies for continuous casting. These parameters are usually optimized and controlled separately which caused internal quality fluctuations in unsteady conditions. In this paper, a coordinated optimal control strategy based on a multiobjective particle swarm optimization (MOPSO) algorithm is proposed for the parameter optimization of secondary cooling and F-EMS, which is solved based on multiobjective particle swarm optimization (MOPSO) algorithm. The solidification and heat transfer model are developed for the computation of billet temperature and the solidification, and the adaptive grid method is used to improve the diversity and robustness of optimal solutions. The secondary cooling water and F-EMS’ stirring current are dynamically controlled based on the optimization results. The results of field trials showed that the maximum carbon segregation and other quality indexes of billets can be improved significantly.

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Control of Macrosegregation Behavior by Applying Final Electromagnetic Stirring for Continuously Cast High Carbon Steel Billet

Cited by 30 publications

References 7 publications

Effect of Solidifying Structure on Centerline Segregation of S50C Steel Produced by Compact Strip Production

Effect of Solidifying Structure on Centerline Segregation of S50C Steel Produced by Compact Strip Production

Method of Verification of Carbon Segregation Ratio Determined with Experimental Methods

Coordinated Optimal Control of Secondary Cooling and Final Electromagnetic Stirring for Continuous Casting Billets

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