On the basis of conventional hot top casting, low frequency electromagnetic field is applied during conventional hot top casting process. Effects of low frequency electromagnetic field on cold fold, macrostructure, microstructure and sump shape have been studied. The experimental results show that with the application of the low frequency electromagnetic filed, the as cast structure has been refined, the depth of cold fold is decreased, the upstream conduction distance becomes long, and the sump becomes shallow. The reasons for the low frequency electromagnetic field refining the structure of the ingot, making the upstream conduction distance long and the sump shallow were summarised.
