The principle of ultrasonic degreasing

       Ultrasound is a high-frequency sound wave with a frequency above 16kHz. The ultrasonic wave is emitted into the degreasing fluid to accelerate the degreasing process. This process is called ultrasonic degreasing. The use of ultrasonic waves in chemical degreasing, electrochemical degreasing, organic solvent degreasing and pickling can greatly improve efficiency. For products with complex shapes, fine pores, blind holes and high requirements for degreasing, degreasing is more effective.



The basic principle of ultrasonic degreasing is that when ultrasonic waves are launched into the liquid, the liquid will produce ultrasonic oscillation, the pressure inside the liquid will suddenly decrease at a certain moment, and then the pressure will suddenly increase at the next moment, and so on. When the pressure suddenly decreases, many vacuum and small cavities will be generated in the solution, and the gas dissolved in the solution will be sucked into the cavities to form bubbles; the moment after the small bubbles are formed, due to the increase of pressure, the bubbles are It is crushed and a shock wave is generated, which can make the oil contamination detach from the surface of the workpiece. Instantaneous high temperature and high pressure will also be generated when the bubble bursts, which will accelerate the stirring and flow inside the liquid. Ultrasonic is the use of shock waves to destroy the oil film and the phenomenon of cavitation, and the intense stirring caused by high temperature and high pressure strengthens the dissolution, saponification and emulsification, and accelerates the oil removal process. In addition, the sound pressure generated by the reflection of ultrasonic waves in the solution will also promote the stirring effect.



Ultrasonic degreasing is usually used in combination with organic solvent degreasing, chemical degreasing, electrochemical degreasing, and low temperature degreasing. In addition to complying with the process parameters of the corresponding oil removal 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. According to some information, when the ultrasonic field strength reaches 0.3W/cm2 or more, tens of thousands of strong collisions will occur between solutions within 1s, and the collision pressure is 5~200kPa, which generates very large energy and forms extremely high liquid acceleration. Quickly remove oil stains. The second is the way of adding ultrasonic waves. The ultrasonic transducer can be directly installed on the cleaning tank, or the transducer can be placed in the cleaning tank. Using the former requires large ultrasonic power, while the latter requires relatively small power, but the transducer must be placed in the most effective part of the cleaning tank through experiments.



When using ultrasonic oil removal, parameters such as ultrasonic field strength, frequency and amplitude should be selected reasonably. Reasonable parameter selection can inhibit the hydrogen permeation effect of cathode electrochemical degreasing and prevent hydrogen embrittlement. Generally, small products with complex shapes can use high-frequency and low-amplitude ultrasonic waves; products with larger surfaces can use low-frequency ultrasonic waves (15~30kHz).



Ultrasound propagates in a straight line, and the surface perpendicular to the propagation direction of the ultrasonic has the best degreasing effect. In order to improve the degreasing effect of the recessed parts and the back of the workpiece, it is best to continuously rotate or turn the part.