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Electromagnetic stirring with alternating current during electroslag remelting Hernández-Morales, José Bernardo


The electroslag remelting process combines both a chemical refining ability and a better control on solidification which produces materials of more uniform properties. In spite of the advantages of this process, segregation-prone alloys are still difficult to produce via ESR, particularly when large ingot diameters are involved. In this context the study of externally applied electromagnetic fields is of great interest. An AC operated stirring device was designed and laboratory-scale experiments were conducted. The solidification structures resulting from the stirring as well as the mixing conditions prevailing in the liquid pool were investigated. Also, modelling studies on the electromagnetic body force produced by the stirrer and the resulting thermal field were conducted. The start of stirring results in a clearly defined band in both steady- and unsteady-state regimes. The microstructure was not significantly modified in the center of the ingot but a loss in directionality was found at the mould wall. It seems apparent that the stirred liquid does not penetrate significantly inside the interdendritic region. Mixing studies revealed that the degree of mixing in the pool is enhanced by the stirring. The theoretical calculations show that most of the electromagnetic body force is confined to the magnetic skin depth at the mould wall and the metal-slag interface. Using a previously developed two-dimensional heat transfer model it was not possible to reproduce the experimental pool profiles obtained when stirring was applied.

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