Macro-physical field of large diameter magnesium alloy billet electromagnetic direct-chill casting: A comparative study

A comprehensive two-dimensional axisymmetric mathematical model that couples transient electromagnetic force with fluid flow, heat transfer, and solidification was established to describe the interaction of multiphysics field during DC casting. The melt flow, heat transfer, and solidification characteristics under differential phase pulse magnetic field and differential phase low-frequency electromagnetic field(DP-PMF and DP-LFEF) were numerically investigated by means of numerical simulation during electromagnetic direct-chill(DC) casting of AZ31 alloy at the same casting conditions. The effects of differential phase electromagnetic fields on Lorentz forces distributions, melt flow, heat transfer, and liquid sump shape were discussed systematically. Based on measured current waveform, the results were compared with those obtained without magnetic field(MF) and under conventional pulse magnetic field(PMF) and low-frequency electromagnetic field(LFEF)under the same conditions. The results show that the application of magnetic fields can significantly change the solidification process of DC casting. Differential phase magnetic fields(DP-LFEF and DP-PMF) can effectively reduce the temperature of the melt in the liquid sump,and the shallower liquid sump depth can be obtained under the differential phase magnetic fields. A large velocity vibration amplitude and a lower temperature are available simultaneously under DP-PMF, resulting in more uniform temperature distribution.