| In steel continuous casting process, the stability of metal free surface in mold directly relate to the casting surface quality. But in electromagnetic continuous casting process, the free surface fluctuation due to alternating magnetic force is inevitable. Therefore it is important to find the method to control surface fluctuation in order to remarkably improve the quality of casting. After reviewing some effects of magnetic field on the behavior of liquid metal free surface, the meniscus deformation and fluctuation with alternating magnetic field and compound magnetic field is investigated.The low melting point alloy Ga-In-Sn was used to simulate molten steel in the experiment. The method of small coil and CT3 Tesla meter were used to measure the magnetic flux density of alternating magnetic and the static magnetic field respectively. The meniscus deformation is observed by a high-speed camera under different parameters, such as the relative position of liquid metal, the coil current intensity, the shape of molten pool and magnetic field frequency. By using a laser displacement sensor, the free surface fluctuation is measured.The results show that the metal free surface was shaped into convex meniscus under high-frequency magnetic field, and the free surface keeps fluctuating all the time. With alternating current increasing, the meniscus height is increased and the fluctuation is more violent. While the initial metal level is located in the coil center along coil height, the meniscus deformation is larger and the metal free surface fluctuation is also more violently. In square cross section molten pool, the meniscus deformation is become boss shape, but free surface fluctuation is more violent with increase of static magnetic flux density. With low frequency magnetic field, reticulate fluctuation is appeared on metal free surface. With increase of low-frequency coil current, the reticulate fluctuation gradually transforms to strip fluctuation. Smaller of the magnetic field frequency is, the more violent of the surface fluctuation is. The stretch phenomenon is observed due to superposing high static magnetic field and alternating magnetic field, and regular layer waves appear on free surface. The meniscus deformation is non-homogeneous. Static magnetic field can effectively damp free surface fluctuation due to high frequency magnetic field. There exists an optimum static magnetic flux density for stable free surface. In this study, the optimum current for static magnetic field is about 1500A. But static magnetic field can't effectively damp free surface fluctuation due to low frequency magnetic field. In low frequency magnetic field, the metal free surface fluctuation becomes more intense if superpose static magnetic field simultaneously. |
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