Study of the deoxidation of steel with aluminum wire injection in a gas-stirred ladle
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I. INTRODUCTION
DEOXIDATION of steel using aluminum wire injection and further removal of inclusions plays a crucial role in ladle metallurgy, especially with the growing demand for cleaner and cleaner steels. There is ongoing interest in understanding the dynamics of inclusions in liquid steel. Deoxidation of steel using aluminum involves three basic consecutive steps: (1) formation of critical nuclei of the deoxidation product, namely, alumina, (2) a progress of deoxidation resulting in the growth of the reaction products, and (3) their separation from the melt. The formation rate of critical nuclei depends on the extent of supersaturation. Further, the growth rate of oxide inclusions is controlled by mass transfer. As the alumina particles are formed, they interact with the bulk flow and local eddy flow of the steel melt and are subject to collision, agglomeration, growth, and flotation. Various models have been developed based on various coarsening and separation mechanisms such as the Stokes collision, turbulent collision, floating separation, etc.[1,2] Recently, Tozawa et al.[3] have derived an equation for the floating velocity of cluster-shaped alumina inclusions which uses fractal theory for quantification of the size and density of alumina clusters. In order to gain a better understanding of deoxidation phenomena, there is the need to develop a comprehensive model that could involve fluid flow, deoxidation kinetics, and removal of deoxidation products. Along these lines, a research program has been initiated at the Division of Metallurgy, Royal Institute of Technology (Stockholm). As the first step toward a comprehensive K. BESKOW, Graduate Student, L. JONSSON, Professor, and DU SICHEN, Associate Professor, are with the Department of Materials Science and Engineering, Division of Metallurgy, Royal Institute of Technology, SE-100 44 Stockholm, Sweden. N.N. VISWANATHAN, Associate Professor, is with the Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology—Bombay, Mumbai - 400 076, India. Manuscript submitted May 2, 2000. METALLURGICAL AND MATERIALS TRANSACTIONS B
model, the present work involves simulation of the concentration profiles of oxygen and aluminum during deoxidation by aluminum wire injection in a two-dimensional (2-D) gasstirred ladle. II. MODEL FORMULATION The gas-stirred ladle represents a two-phase turbulent recirculating pattern. The mathematical model used in the present study is based on a two-phase model.[4] The gas and liquid phase are considered to be two different interpenetrating and interacting fields. The phases interact with each other at the finite interface areas. The exchanges between phases were represented through source terms in the conservation equations. The following principal assumptions have been made. (1) The gas-stirred ladle is axially symmetric; hence, the governing equations can be written in 2-D cylindrical coordinates. (2) The system is isothermal. (3) The gas bubble size is constant throughout the domain. (4) The free sur
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