Numerical Simulations of Inclusion Behavior in Gas-Stirred Ladles
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rocess, a huge number of nonmetallic inclusions is generated in metallurgical reactor, and have a detrimental effect on the quality of steel especially when coagulated large-size inclusions remain in steel products. Therefore, the inclusion removal is one of the main objectives, and the size of inclusion in molten steel is desired to be smaller year by year for the steelmaking industry. For the small inclusions with very low flotation velocity, it is difficult to remove them from the system only by their own buoyancy, while gas injection is an effective way to improve the removal and is commonly practiced in the secondary metallurgy processes and continuous casting,
WENTAO LOU, Ph.D. Candidate, and MIAOYONG ZHU, Professor, are with the School of Materials and Metallurgy, Northeastern University, Shenyang 110819, People’s Republic of China. Contact e-mail: [email protected] Manuscript submitted November 15, 2012. METALLURGICAL AND MATERIALS TRANSACTIONS B
such as ladle argon gas treatment, RH vacuum treatment, and the gas injection in the submerged entry nozzle (SEN) of continuous-casting mold. Therefore, to remove and control inclusions in molten steel, it is necessary to reveal clearly the fundamental behavior of inclusions in the gas-stirred systems. Currently, many models have been proposed to describe the inclusion behavior in liquid steel, which can be classified into static population balance model (PBM)[1–7] and dynamic computation fluid dynamics (CFD)-based models[8–22] depending on whether the fluid flow was considered for inclusion transport. In the static PBM model, inclusions were divided into several groups according to their sizes, and the Smoluchowski equations were applied to describe size distribution of inclusions. Multiple mechanisms for inclusion growth due to turbulent shear collision, Brownian collision, and Stokes collision, and for inclusion removal due to wall adhesion, bubble-inclusion buoyancy collision and Stokes flotation were considered in this approach,[4–6] and the inclusion homogeneous nucleation and Ostwald ripening were also taken into account
by some researchers.[7] This model was computationally more economical; however, the spatial distribution of inclusions was assumed to be uniform without considering the inclusions transport by fluid flow. Furthermore, the effect of the local turbulence flow in metallurgical reactors on the inclusions growth and removal was ignored either. For the dynamic CFD-based models,[8–22] the inclusions transport carried by fluid flow and their spatial distribution were described, and the CFD-based model was also divided into three approaches, namely inclusion trajectory model,[8–13] characteristic parameters conservation model,[14–16] and CFD–PBM coupled model.[17–22] In the inclusion trajectory model, the inclusion phase was treated as individual particles, and their trajectories were described by integrating the force balance on particle under a Lagrangian reference frame. In this approach, the exact movement of single inclusion in the fluid flow, including th
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