Modeling of Quasi-Four-Phase Flow in Continuous Casting Mold Using Hybrid Eulerian and Lagrangian Approach
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mold is the last part for controlling the cleanliness of liquid steel, and is called the heart of continuous casting equipment. Some operations such as the homogenization of molten steel, gas treatment, mold slag emulsification, non-metallic inclusion removal consist of very complex multi-phase physicochemical reactions and fluid flow. Fluid flow in the continuous casting mold is very important, because it influences many important phenomena which have far-reaching consequences on product quality. These phenomena include the inadequate liquid slag layer coverage and meniscus stagnation due to level fluctuations, the entrainment of mold slag due to meniscus vortex and high surface velocity, the entrapment of argon bubbles and non-metallic inclusions by the solidified shell, and the breakouts due to jet impingement. A schematic of the multi-phase fluid flow inside the mold is shown in Figure 1. Details of the complex phenomena in the continuous casting mold can be found in some previous works.[1–4] Therefore, the control of ZHONGQIU LIU, ZHENBANG SUN, and BAOKUAN LI are with the School of Materials and Metallurgy, Northeastern University, No. 3-11, Wenhua Road, Heping District, Shenyang 110819, China. Contact e-mail: [email protected] Manuscript submitted December 21, 2015. Article published online December 27, 2016. 1248—VOLUME 48B, APRIL 2017
multi-phase fluid flow plays an important role in attaining a better product quality. Mold slag is added periodically to the top surface of the mold. It sinters and melts to form a protective liquid slag layer, which helps to trap inclusions. The liquid slag is drawn into the gap between the solidified shell and mold during oscillation, where it acts as a lubricant and helps to make heat transfer more uniform.[5] So a sufficiently thick slag layer over the surface of the molten steel in the mold is important. When the turbulent flow is strong at the interface of slag and molten steel, time-varying level fluctuations across the mold width may occur and cause some serious surface defects, such as slag entrainment and oxygen and nitrogen pickup, which are detrimental to steel quality. If the slag layer is sufficiently thin, this process exposes an open area of molten steel to the atmosphere, termed the ‘‘exposed slag eye.’’ Furthermore, the slag–metal interface at the periphery of the eye region may break up into slag droplets, often referred to as ‘‘slag emulsification,’’ resulting in undesirable effects like slag entrainment. So the hydrodynamics and the associated transport phenomena of these regions are of great practical significance for the production of clean steel. Recently, the phenomena of level fluctuation[6,7] and mold slag entrapment[8,9] have been the subject of some recent works, but many aspects require further investigation.
METALLURGICAL AND MATERIALS TRANSACTIONS B
Argon gas is usually employed in the continuous casting process to prevent nozzle clogging, encourage mixing, and promote the floating of non-metallic inclusions from the molten steel by changing the flow field.[10–13]
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