Numerical Simulation of Slag Eye Formation and Slag Entrapment in a Bottom-Blown Argon-Stirred Ladle
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TO achieve a uniform distribution of alloy elements and temperature in liquid steel, to remove inclusions and to improve the rates of refining reactions, argon gas stirring has been widely used in the steelmaking refining process. Bubbles are formed after argon gas is ejected at high-speed at the exit of the nozzle. Then, the bubbles entrain the surrounding liquid steel and rise upward and form a turbulent bubble plume. Therefore, the time for homogenizing the chemical composition of alloy elements and temperature is shortened. Meanwhile, the bubbles will trap inclusions around themselves and bring them to the slag during their floating process. In high gas flow rate conditions, the bubbles will break up the slag layer forming a slag eye and cause strong fluctuations between the slag and the steel interface, which promotes the
WEI LIU, HAIYAN TANG, SHUFENG YANG, MINGHUI WANG, JINGSHE LI, and QING LIU are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China. Contact e-mail: [email protected] JIANHUI LIU is with the Central Iron and Steel Research Institute, Beijing 100081, China. Manuscript submitted April 21, 2016.
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chemical reaction between the liquid steel and the top synthetic reducing slag. The main purpose of the refining process is to completely deoxidize and desulfurize liquid steel. A strong interaction between slag and steel is needed to promote the efficiency of desulfurization, but when the slag eye is too large, oxygen would be absorbed from the atmosphere into the liquid steel. At the same time, slag entrapment behavior possibly occurs under large gas flow rate. Therefore, fully understanding the formation of the slag eye and the interaction behavior between slag and steel under different gas flow rates is important. The phenomenon of slag eye formation has been the subject of some works in recent decades. Many studies have been conducted by cold physical models[1–6] and numerical simulations[7–15] in order to investigate the flow characteristics and slag layer behavior in the gas-stirred ladle. Cold model experiments using mercury and silicon oil as the metal and slag, respectively, and plant experiments were carried out in the study of Yonezawa and Schwerdtfeger.[1] The eye geometry was measured with a video technique, and dimensionless correlations were established for the time average of the open area and the time fraction for the existence of an open or a closed spout. The dimensionless correlations were further developed and improved by Subagyo[2] and Mazumdar et al.[3] In the work of Krishnapisharody and Irons,[4,5] eye sizes were measured
in room-temperature modeling over a wide range of conditions, and a mechanistic model for eye size was developed. Intensive experiments were carried out on the generation of open-eyes based on an on-line monitor system in the research of Valentin et al.[6] It was found that typical open-eyes came into existence and that the shape and size were in
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