Improving ingot homogeneity by modified hot-top pulsed magneto-oscillation

Heavy ingots, especially the ingot of more than 10 t, often contain detrimental heterogeneous defects, such as macrosegregation, shrinkage pipes, and cracks. Hot-top pulsed magneto-oscillation (HPMO) can refine the solidified structure of ingot and improve their homogeneity. However, it may exacerbate the positive segregation at the upper part of the ingot body. Thus, a round table HPMO riser with a feeding part was designed, and the microstructure and macrosegregation of Al–Si alloy ingots solidified with and without HPMO were investigated. The simulation and experimental results indicated that round table HPMO riser could enable fine and uniform solidified structures in the whole ingot body; in the meantime, feeding part allowed the melt with enriched solute to gather in the upper part of the riser until the last solidification stage of ingot. This provides an effective approach for obtaining highly homogenized ingots.