The free surface waves of a molten low-melting point Sn-32%Pb-52%Bi alloy under the imposition of an AC and a static magnetic field were visualized and recorded by use of a laser displacement sensor and a high speed video camera. The Fourier analysis method was used to analyze the oscillation characteristics. The results show that at the center of the free surface,the azimuthal and radial oscillation mode can be found simultaneously owing to AC magnetic field. With increasing coil current intensity,the amplitude and the main frequencies of the oscillations increase,and the azimuthal fluctuation at the center of the free surface is also enhanced. The fluctuation characteristics are closely related to the turbulent flow induced by the alternating electromagnetic force. A series of regular traveling waves can be observed on free surface,and the main frequencies of oscillations at three-phase points decrease owing to superposing AC and static magnetic field. The static magnetic field can remarkably control the unstable swinging behavior of free surface. With increasing static magnetic flux density,the amplitude of oscillations at the center of free surface decreases firstly,and then increases,but the fluctuation amplitude at the triple-phase point always reduces and keeps within 1 mm,and the azimuthal waves at the center of free surface are weakened. Especially at 1.44 T,the radial waves are dominant. The static magnetic flux density should be controlled in an appropriate range to obtain more stable free surface. With compound magnetic field,even if the static magnetic flux density is above 1.0 T,the free surface still vibrates with lower amplitude and dominant frequency.
DENG An-yuan WANG En-gang XU Yong-yi ZHANG Xing-wu HE Ji-cheng
Utilizing ANSYS CFX commercial software and volume fraction of fluid(VOF)model,fluctuation behavior of steel/slag interface was numerically simulated in continuous casting mold with static magnetic field,and the influence of metal jet characteristics on the behavior of steel/slag interface was investigated.The results indicated that the behavior of steel/slag interface is similar at different process parameters,which is closely related to the characteristic of the flow field.The steel/slag interface has an obvious trough characteristic,which can be divided into three zones:frontal valley zone,back valley zone and horizontal zone;as the magnetic flux density increases,the fluctuation of liquid level increases firstly and then decreases,and a reasonable magnetic flux density can make steel/slag interface obtain a relatively flat interface,which can prevent slag from being entrapped into liquid steel.For a thin slab continuous casting process,when the casting speed is 4m/min,a reasonable magnetic flux density is about 0.5T,and the interfacial fluctuation is weaker.No matter the position of magnetic field is horizontal or vertical,for different operating parameters,there is a corresponding reasonable magnetic field position where the steel/slag interface fluctuation can be properly controlled and slag entrapment can be prevented.
