Tundish Open Eye Formation in Inert Gas-Shrouded Tundishes: A Macroscopic Model from First Principles
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OPEN eye (exposed slag eye) formation in an inert gas-shrouded tundish is a result of aspiration of Argon gas into liquid bath. When liquid steel from ladle is poured into a tundish via ladle slide gate, a region of negative pressure develops which can easily draw in air from atmosphere, and subsequently result in reoxidation of steel. The usual practice in plants is to flood this region with an inert gas such as Argon so that air entrainment is prevented. However, Argon gas itself can be aspirated into the ladle shroud. The flow of Argon bubbles in liquid steel results in the formation of a two-phase gas–liquid plume. The plume rises from bottom to top surface of tundish because of buoyancy. The radial component of the flow becomes stronger as the plume rises. The slag layer sitting on top of steel is pushed radially outwards by upward-bound plume. A part of the liquid steel now gets exposed to the external atmosphere which makes it a region for potential reoxidation. This region is somewhat circular in shape and is known as the tundish open eye. Gases such as oxygen and nitrogen present in air have high affinity to react with dissolved elements in steel like Al, Mn, Ti, etc. to form harmful inclusions. The primary inclusions formed are Al2O3 during open eye formation in tundish.[1] Complex inclusions such as Al2O3-TiOx[2] or MnAl2O4[3] can also form when Al2O3 reacts with components such as TiO2, Ti2O3, or MnO present in SAIKAT CHATTERJEE, Ph.D. Student, and KINNOR CHATTOPADHYAY, Assistant Professor, are with the Process Metallurgy and Modelling Group, Department of Materials Science & Engineering, Faculty of Applied Science & Engineering, University of Toronto, Wallberg Building, 184 College Street, Suite 140, Toronto, ON, M5S 3E4, Canada. Contact e-mail: [email protected] Manuscript submitted December 22, 2015. Article published online July 29, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
slag or refractories. These inclusions generally have dendritic or cluster-like shapes, which allows them to easily get attached to the walls of the nozzles and clog them. Slag entrainment is another unwanted outcome since this can also result in clogging of nozzles. Clogging of nozzles such as SENs retards the rate of productivity and may also lead to breakouts. Moreover, lifetime of SENs is affected immensely due to clogging, making it necessary to replace them at prenatal stages. This usually turns out to be a costly affair and a reason of concern for the steelmaking and casting community. As a result, it is absolutely essential that we investigate this problem thoroughly in order to minimize its harmful aspects. A lot of researchers have studied slag/ open eye formation in ladles; however, only a handful of articles are present on open eye formation in tundishes.[4,5] Apart from numerical modeling, few researchers have analyzed the open eye area in ladles from fundamental principles of ladle hydrodynamics[6] or fluid mechanics.[7,8] The present work also aims to investigate the formation of open eyes in t
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