The effect of a uniform direct current magnetic field on the stability of a stratified liquid flux/molten steel system

Abstract

In continuous slab casting, the instability of the interface between the liquid flux and molten steel is very important, as it is related to the entrapment of liquid flux into molten steel. The entrapment of liquid flux springs up when the velocity under the meniscus exceeds the critical velocity.[1] This situation is the same as the Kelvin-Helmholtz instability, which is the instability of the interface between two fluids with relative motion. However, few studies of the continuous casting process have related the Kelvin-Helmholtz instability to the entrapment of the liquid flux, and there has been little focus on this instability in metallurgical processes. In addition, the effect of direct current (DC) magnetic field on the Kelvin-Helmholtz instability has not been reported in metallurgical processes. Many researches in other parts for the effect of the DC magnetic field have assumed that the conductivity of fluid is infinite. However, real conducting fluids in metallurgical processes such as molten steel have finite conductivity, and especially, the liquid flux has a very small conductivity compared with molten steel. In this study, the Kelvin-Helmholtz instability of a stratified liquid flux-molten steel system and the effect of DC magnetic field on the instability of the interface between liquid flux and molten steel are studied assuming the conductivity of liquid flux is zero. The results show that when the instability does not occur, the DC magnetic field dampens the fluctuation of the interface between flux and molten steel more than the case with no magnetic field. However, when the instability occurs, the DC magnetic field could not dampen the fluctuation. In addition, the DC magnetic field expands the range of wave numbers of the instability.