Magnetic Field, Flow Field and Inclusion Collision Growth in a Continuous Caster with EMBR

Abstract

A three-dimension mathematical model has been developed to describe the magnetic field, fluid flow and inclusion transport in a continuous caster with electromagnetic brake (EMBR). According to the model, all the governing equations can be expressed as a general differential equation, so a general numerical method was developed to solve these equations. The numerical results agree well with the experimental result. In the continuous caster, the inclusion distributions have 'M' shape under the nozzle and 'W' shape at the exit, which come from the centrifugal effect and the collision and aggregation among inclusions. The three-dimensional static magnetic field can effectively damp local flows and affect the inclusion transport in a continuous caster. If EMBR is installed under the nozzle, it can promote the inclusion removal and the inclusion 'M' distribution disappears. IntroductionThe flow pattern of molten steel in the continuous casting mold is of great interest because of its influence on many important phenomena related to product quality, such as entrapment of inclusions and bubbles on the solidified shell, and entrainment of mold slag at the slag-metal interface. These foreign phases will cause various defects in the slabs. The problems were addressed by the ABB and Kawasaki Steel corporations in the early 1980s. The first generation EMBR [1][2][3][4][5] consists of two braking areas, each covering the steel flowing out of one nozzle port. It was developed to act directly on the molten steel discharged from the immersion nozzle and to reduce its flow velocity. Afterwards, the second-generation EMBR [6][7][8][9][10][11], known as EMBR Ruler, was developed. Its innovative feature is that the two magnetic poles at the same side of the mold in the first generation EMBR were combined into one larger pole that substantially covers the entire width of the slab. Later, the third generation EMBR [7,[11][12][13], called the FC Mold, was made up of two sets of the second generation EMBR Ruler. The FC Mold creates two equally strong static magnetic fields, one field at the meniscus level to control the surface stream, and another field at the lower part of the mold to control the stream directed downwards. In all, three generations of EMBR are the division or combination of the second generation EMBR.The transport of inclusions depends obviously on the fluid flow. Therefore, great modeling efforts were made to study the fluid flow in the mold. And recently, some metallurgists also investigated the influence of fluid flow on inclusion transport. For the numerical simulation of EMBR, the researchers always assumed that the magnetic field caused by EMBR could be simplified as a uniform distribution [4] Chem. Eng. Technol. 2007, 30, No. 12, 1650-1658 [5] or a one-dimensional distribution [6,7,12,13], and solved a Poisson equation for the electric potential to get the distribution of the electric potential in the mold. For the numerical simulation of the inclusion behavior, most of these publications investigate the incl...

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