As early as 1950, Eisenreich [5] compared vacuum ultrasonic degassing with vacuum degassing, degassing with chlorine lancing, and sonic and ultrasonic degassing. He pointed out the potential of ultrasonic processing but also mentioned related practical difficulties. Sergeev [6] noted that despite the high potential of ultrasonic degassing, there is a challenge in transferring sufficient ultrasonic power to a large mass of liquid metal.