Effects of AC magnetic field on solidification structure of continuously cast hollow billet

To verify the effect on the solidification structure by a travelling magnetic field (TMF) and a rotating magnetic field (RMF) imposed in the inner mould of large diameter hollow billet continuous casting machine, a low melting Sn–3⋅5Pb alloy was used to substitute high alloy steel for static simulation experiments. The results show that the TMF and RMF imposed in the inner mould cannot only refine the grain and improve the solidification structure of hollow billet, but also reduce the operation space required in an industrial process for large diameter hollow billet production and that the TMF is better than the RMF to facilitate the transition from columnar to equiaxed structure. In addition, the AC magnetic field (TMF or RMF) imposed in the inner mould is beneficial to improve the inner surface quality of the large diameter hollow billet.