The comparison of ultrasonic effects in different metal melts

The effect of ultrasonic treatment of the melts is mainly ultrasonic streaming and cavitation. In this paper, the ultrasonic streaming in water, aluminum and steel melts was numerically simulated and compared. And the simulated results of streaming in water were validated by experimental results. In the experiment, the ultrasonic booster was immersed vertically into water, the ultrasonic streaming phenomenon was observed by high-speed CCD (Charge-coupled Device) system, then the streaming velocity and streamlines were obtained. The cavitation area and threshold in aluminum and steel melts were compared. The results show that the effective streaming and cavitation area in steel melt is smaller than that in aluminum melt, and far smaller than that in water. A symmetrical vortex forms both in water and aluminum melt by the drive of downward ultrasonic streaming caused by the booster tip. However, in steel melt, a double-vortex structure, including a vortex in the upper part and a vortex with reverse cycling in the lower part appears in the flow field. As a result, inclusions and air bubbles may be trapped in steel melt. The density and viscosity of the fluids are the main factors influencing ultrasonic streaming and cavitation. The results provide references for the application of ultrasonic treatment in metal melts. (C) 2014 Elsevier B.V. All rights reserved.