Effect of Reversing Rotational Magnetic Field on Grain Size Refinement

In order to achieve a high quality aluminum ingot, fine grains are required. The electromagnetic stirring process is known as one of the processes that promotes grain size refinement in aluminum alloys. In this study, a reversing Rotational Magnetic Field (reversing RMF) that reverses the rotation direction of the electromagnetic field at regular intervals was applied to molten aluminum in the cylindrical container of a round billet for DC casting. The molten aluminum underwent a clockwise and counter-clockwise flow by applying a reversing RMF. When the periodic time of the reversing RMF is long, the grain size of the billet was finer than that of the mono-directional rotational flow. On the other hand, the grain size of the billet center was not fine when the periodic time of the reversing RMF was short. The flow field was calculated by a CFD simulation for comparison with the experimental results. It was found that the development of the flow field affected the grain size refinement.