Ultrasonic wave is a kind of high frequency sound wave whose frequency is above 16kHz. It can speed up the process of oil removal by sending ultrasonic wave into oil removal liquid. The ultrasonic wave can be used in chemical deoiling, electrochemical deoiling, organic solvent deoiling and pickling to greatly improve the efficiency. Oil removal is more effective for products with complex shape, fine holes, blind holes and high requirements for oil removal.

The basic principle of ultrasonic oil removal is that when the ultrasonic wave is launched into the liquid, it will cause the liquid to produce ultrasonic oscillation. When the pressure suddenly decreases, a lot of vacuum and small holes will be formed in the solution. The gas dissolved in the solution will be sucked into the holes and form bubbles, the bubble is crushed and creates a shock wave that can pull oil off the surface of the workpiece.

High temperature and high pressure are also produced at the moment of bubble rupture, which accelerates the internal agitation and flow of the liquid. Ultrasonic is to use the destruction of shock wave on the oil film and cavity phenomenon, high temperature and high pressure caused by intense agitation to strengthen the dissolution, saponification and emulsification, to accelerate the oil removal process. In addition, the acoustic pressure generated by the reflection of ultrasonic waves in the solution also promotes agitation.

Ultrasonic de-oiling is usually used in combination with organic solvent de-oiling, chemical de-oiling, electrochemical de-oiling and low temperature de-oiling. In addition to complying with the process parameters corresponding to the oil method, there are two independent process parameters:

One is the power of the ultrasonic generator, the greater the power of the ultrasonic generator, the better the oil removal effect. It is reported that when the ultrasonic field is over 0.3 W/CM2, tens of thousands of strong collisions will take place between solutions within one second, and the collision pressure is 5 ~ 200 kpa, resulting in very large energy and extremely high liquid acceleration, remove oil quickly.

The second is the way to join the ultrasonic, ultrasonic transducer can be installed directly in the cleaning tank, can also put the transducer in the cleaning tank. The former requires a large ultrasonic power, the latter relatively small power, but to pass the test to put the transducer in the most effective part of the cleaning tank.

The parameters of ultrasonic field strength, frequency and amplitude should be selected reasonably when ultrasonic oil removal is used. The reasonable selection of parameters can inhibit the hydrogen permeation of cathodic electrochemical deoiling and prevent hydrogen embrittlement. In general, small products with complex shapes can be ultrasonic with high frequency and low amplitude, while products with large surface can be ultrasonic with low frequency (15 ~ 30kHz) .

The ultrasonic wave travels in a straight line, and the oil removal effect is best on the surface perpendicular to the direction of ultrasonic wave propagation. In order to improve the deoiling effect of the concave part and the back of the workpiece, it is better to keep rotating or turning the part.