Effect of Ladle Changeover Condition on Transient Three-Phase Flow in a Five-Strand Bloom Casting Tundish
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l known that the flow behavior in a bloom casting tundish is very important for the quality of the bloom and that many defects in the steel products are induced by entrapment of slag and reoxidation of steel in the tundish.[1,2] There are two stages in tundish metallurgy: the steady-state operation and the transient casting operation. A large number of papers published during the last decade, even recently, have focused on modeling the residence time distribution (RTD), multiphase flow, nonmetallic inclusion
HUA ZHANG, QING FANG, CHAO LIU, YI WANG, and HONGWEI NI are with the State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, No. 947, Heping Avenue, Qingshan District, Wuhan, 430081, P.R. China and also with the Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology. Contact e-mails: [email protected], [email protected] RONGHUA LUO is with the Valin Xiangtan Iron and Steel Co., Ltd., Xiangtan, 411101, P.R. China. Manuscript submitted November 8, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS B
behavior, and heat loss, among others, during the steady-state operation period of tundish metallurgy, predominantly by homogeneous turbulent flow models.[3–6] Transient-state operations in a tundish, such as the start-up, ladle changeover, and end of sequence processes,[7] are the main determining factors affecting the stability and purity of the molten steel injected into the mold. Comparatively, the two- and three-phase modeling of the transient casting process has been less thorough and relatively rare. Modeling the transient multiphase turbulent flow behavior in the tundish is a relatively difficult task with complicated metallurgical behaviors and needs large calculation resources, especially for the ladle changeover process. Fernandez Oro et al.[8] and Jha et al.[9,10] paid attention to the variation in steel intermixed concentration with the filling time and under different casting conditions, while the liquid level fluctuation and the steel–slag–gas three-phase behaviors were ignored. Takahashi et al.[11] investigated the velocity field during ladle changeover and proposed a rule to predict the floating condition of nonmetallic inclusions. Lin et al.[12–14] investigated the steel flow, heat loss, and removal behavior of nonmetallic inclusions in a 2-strand
tundish in the steady and transient states and analyzed the effects of the operations of sudden stopping, ladle changeover, and sudden closing of one strand on the cleanliness of molten steel. However, the behaviors of level fluctuations and slag entrapment, which also significantly affect the cleaning of liquid steel during these operations, were ignored. Despite the importance of transient operations to steel quality, few studies dealing with the tundish filling process during ladle changeover consider the effect of the large increase in the injection velocity on level fluctuations, the change in steel level, and slag and air entrapment during ladle c
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