The effect of a uniform direct current magnetic field on the stability of a stratified liquid flux/molten steel system
- PDF / 291,482 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 66 Downloads / 242 Views
NTRODUCTION
IN continuous slab casting, the direct current (DC) magnetic field has been used widely for the purpose of reducing nonmetallic inclusions and the entrapment of liquid flux into molten steel. The entrapment of liquid flux occurs when the velocity under the meniscus exceeds the critical velocity. This entrapment is related to the instability of the interface between the liquid flux and molten steel, so called, the Kelvin–Helmholtz instability.[2] So, the study of the instability of the interface between a nonconducting fluid and a conducting fluid is important for the optimal application of the DC magnetic field to the continuous slab caster. The Kelvin–Helmholtz instability is the instability due to interfacial friction, which arises when the two stratified fluids have relative motion. When the velocity difference between the two stratified fluid exceeds a certain critical velocity, which is the function of the density difference between two fluids, interface tension and wave number, etc., an instability of the interface develops. The Kelvin– Helmholtz instability and the effect of the DC magnetic field on the instability have been studied theoretically by many researchers.[2–5] According to their results, the DC magnetic field suppresses the instability of the interface between two stratified conducting fluids as strongly as surface tension and increases the critical velocity for the instability of the interface. In spite of their remarkable analyses, their limitation is the assumption of an infinite magnetic Reynolds
PIL-RYUNG CHA, Graduate Student, and JONG-KYU YOON, Professor, are with the School of Materials Science and Engineering, Seoul National University, Seoul 151-742, Korea. Manuscript submitted January 14, 1999. METALLURGICAL AND MATERIALS TRANSACTIONS B
number which comes from the infinite conductivity. Therefore, it could not hold in real conducting materials such as molten steel with a finite conductivity. In this study, the effect of the DC magnetic field on the Kelvin–Helmholtz instability of the interface between liquid flux and molten steel was analyzed with the finite conductivity including the effect of interface tension. The results of this study show that the parallel DC magnetic field damped the fluctuation of the interface when the instability of the interface did not occur and that the DC magnetic field could not suppress the instability of the interface once the instability had developed. These results are very different from the results of the previously mentioned researchers, which reported that the DC magnetic field remarkably suppresses the instability of the interface when the instability occurs, and then the instability eventually disappears. This difference is due to the assumption that the conductivity of the fluids is infinite, that is, magnetic Reynolds number is infinite. II. STABILITY ANALYSIS The Kelvin–Helmholtz instability arises when the two stratified fluids have relative motion. The initial stationary state whose stability we wish to examine is that of incom
Data Loading...
