Study on Flow Field Control in Continuous Casting Mold by Electromagnetic Field
The mold is the key part of the continuous caster, in which the metallurgical processes are very critical to improvement of slab quality. A lot of researches showed that most of the defects affecting steel quality in the process were closely associated with fluid flow in the mold. With increase of casting speed, both of the flow rate and flux of the flow discharged in the submerged entry nozzle (SEN) increased and the flow of liquid steel was accelerated in the mold, Moreover, the flow stability of liquid steel was deteriorated. Excessive surface velocity could entrain mold flux and cause surface level variations and fluctuations that produced surface defects. Excessive velocity of liquid steel could strengthen scouring action to the initial solidification shell, degraded the uniformity of the shell, increased the depth of the mark and deep penetration of the jet entering the mold and hindered the inclusions and bubbles float upward that produce the inter defects. Accordingly it is extremely important to study and control the flow in the mold. To solve these problems, electromagnetic techniques have been developed and applied to the continuous casting process, such as electromagnetic brake and electromagnetic stirring. In the paper, the flows in mold of the continuous casting slab, billet and two- roll strip with electromagnetic fields have been studied, and the effects of the flows on the quality of steel have been analyzed combined with the questions in the industry.
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Consequently, the intensity of electromagnetic stirring should be determined according to operation parameters in continuous casting, e.g., casting speed, in the industry.For two roll strip casting, the flow in twin roll pool was controlled by imposing static magnetic fields coupled with direct current in the nozzle. The effects of location of magnets and intensity of electric currents on surface fluctuation and flow behaviors near the meniscus have been investigated using mercury, respectively. The experimental results showed that it was beneficial for improvement of the flow at the meniscus and the free surface fluctuation to apply the nozzle electromagnetic brake technology, which would be good for improvement of the conditions of initial solidification and the quality of steel. Additionally, it could provide good conditions for other technologies. When the magnet was placed nearer the outlet of the nozzle, it is beneficial to reduce the free surface fluctuation. The magnetic field coupled with direct current is more effective for suppression of the flow near the meniscus and the free surface fluctuation in twin-roll strip casting caster compared with only imposing a magnetic field.
Tags: neodymium magnets Flow Field Control,Continuous Casting Mold Smco magnets