Surface Quality Improvement of Continuously Cast Metals by Imposing Intermittent High Frequency Magnetic Field and Synchronizing the Field with Mold Oscillation.

Abstract

In order to improve the surface quality of continuously cast steel, two new casting processes imposing a magnetic field are developed. One is the imposition of an intermittent high frequency magnetic field from the outside of a mold and the other is a synchronizing imposition of the intermittent high frequency magnetic field with mold oscillation. To distinguish the characteristics of the processes, the meniscus dynamic behavior was investigated in molten gallium as simulator of molten steel and the meniscus deformation was numerically analyzed. The surface quality was examined in the cast tin used as simulator of steel. The imposition of the high frequency magnetic field reduces the effect of mold oscillation on dynamic pressure in a flux channel between molten metal and a mold and suppresses the deformation on meniscus shape. The intermittent high frequency magnetic field suppresses the surface wave motion generated by mold oscillation. When the timing of the magnetic field imposition is synchronized with the period including the lowest position in the stroke of mold oscillation, the better surface quality is obtained than that synchronized with the period including the highest position. The amount of electric current required to get the same surface quality decreases in the order of the imposition of continuous high frequency magnetic field, the imposition of intermittent high frequency magnetic field and the synchronizing imposition.