<p class="MsoNormal" style="text-align: justify">After being tapped from a basic oxygen furnace or electric arc furnace, the liquid steel must be refined at a ladle treatment station as part of alloying and quality improvement. In the ladle, the steel can be stirred using electromagnetic techniques, argon injection, or a combination of both methods. This work discusses the observed differences in stirring characteristics between these different approaches.&nbsp; Simulations of gas-stirring using a single plug, stirring using upwards electromagnetic stirring (EMS), downwards EMS, and the combination of electromagnetic stirring and single bottom plug with various plug positions in relation to the active EMS unit. The approach found in this work uses the computational fluid dynamics solver ANSYS Fluent to the simulate the multiphase flow field using a combined Eulerian and Lagrangian approaches. The design of the refining ladle is a simplified form on an industry ladle that uses electromagnetic stirring during refining operations, with the model augmented for simulation of the gas-stirring and combined EM-gas stirring simulations.&nbsp; Magnetic field data from an industry stirring unit was provided to the authors by an external party.&nbsp; To improve simulation stability and computational speed, the Lorentz forces of the magnetic field data are imported directly into the simulation via User Defined Function and applied as a momentum source term onto the liquid steel. The transient simulation is performed in two stages: the flow field simulation from resting state to quasi-steady, and the mixing study state.&nbsp; During the flow field simulation, the Volume of Fluid (VOF) approach is used for modeling of the three fluid phases (argon, steel, and slag).&nbsp; This is combined with the Discrete Phase Method (DPM) for modeling of the argon gas particles via bottom-plug injection.&nbsp; The flow field is monitored for quasi-steady state, upon which the momentum calculation is disabled and the secondary mixing study begins.&nbsp; The mixing study uses a tracer species to determine how long is required until homogeneity is reached.&nbsp; The other outputs of the model under consideration are the general flow field patterns, opening of the slag layer to expose the steel to air (“slag eye formation”), and wall shear stresses that may contribute to refractory erosion. Inclusion removal modeling is also performed using the quasi-steady state results and conversion to Eulerian multiphase modeling with Population Balance Method used for inclusion distribution.&nbsp; It was found that under standard stirring conditions, EMS has a faster mixing time than EM-Gas and gas-only, though both EMS and EM-gas see much larger wall shear stresses.</p>

Effects of Combined Electromagnetic and Bottom-Plug Stirring in a Steel Refining Ladle

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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