3D Modeling of the Aggregation of Oxide Inclusions in a Liquid Steel Ladle: Two Numerical Approaches

Abstract

The reduction of the weight of high performance materials together with the improvement of mechanical properties and the increase of the recycling of used metal are new challenges which emphasize the importance of metal cleanliness. Ladle treatment of specialty steels has long been described as the secondary metallurgical process mainly responsible for the non-metallic inclusion derived from the deoxidation process. The treatment is accomplished by blowing argon through one or more porous plugs for the purposes of desulfurization, minor composition adjustments, and inclusion removal. Gas injection is applied on routine basis to achieve both the stirring of the liquid bath (thermal and chemical homogenization) and the entrapment of the inclusions by the bubbles (flotation). Furthermore, the turbulence produced in bubble swarms enhances the probability of inclusion collisions and makes aggregation the first mechanism for particle removal. The physical processes involved in gas stirred ladles are numerous and complex owing to the three dimensional and multiphase (metal-gas and inclusions) nature of the reactor. Despite these difficulties, the population balance equations (PBEs) can be implemented in CFD code [1,2] and combined CFD-PBM (computational fluid dynamicspopulation balance method) models are investigated for steel ladle processes [3,4] and produce very promising results in terms of inclusion removal efficiency. Current research focused on the mathematical formulation of the system and an approach, the quadrature method of moments (QMOM), has been formulated and applied. [5] A natural alternative of the QMOM is the classes method (CM) in which the particle size distribution (PSD) is represented through a finite number of inclusion classes. [6] Very few authors [7][8][9][10] implemented these two techniques in CFD code with the aim of discussing their relative advantages and disadvantages. It should be noted that all of the simulation were performed for a 2D (or more recently 3D) gas-bubble or liquid-liquid reactor and comparison applied to ladle treatment is nonexistent in literature. Therefore the main focus of this work is to simulate the behavior of non-metallic inclusions in an industrial gasThe ladle treatment of liquid steel is mainly responsible for the steel cleanliness, since it generates as well as eliminates most of the oxide inclusions. Today, the combination of computational fluid dynamics and population balance modeling makes the numerical simulation of this complex threephase reactor possible. First, the comprehensive three-dimensional turbulent multiphase flow model is developed to study the behavior of argon bubbles in liquid steel based on the geometry and operating conditions corresponding to the real industrial process. This simulation is validated by comparing the calculated mixing time with the experimental value predicted from ladle sampling. Then, the balanced equation for a population of oxide inclusions with aggregation mechanism is coupled with the hydrodynamic modeling. To obtain ...

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Numerical Modelling of Inclusion Behaviour in a Gas-stirred Ladle

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