Cutting fluid is widely used in the field of metal processing, which mainly plays the role of lubrication, rust prevention, cleaning and cooling.






Chemical synthetic cutting fluid is a new type of water-based cutting fluid, which is composed of various additives, with stable performance, long service cycle, low pollution and other advantages, is the direction of cutting fluid research in 2013.






Its drawback is that it is easy to foam in the use process, which directly affects its lubrication and cooling effect, and the general cutting fluid defoamer can not meet the requirements.






Therefore, we have made a theoretical discussion on the formation of cutting fluid foam and the principle of defoaming, a variety of cutting fluid defoaming agent to do experimental research, using the orthogonal experiment to compound the compound cutting fluid defoaming agent, to solve the water-based cutting fluid defoaming, foam suppression problems.










01


Foaming cause analysis







"Foam" is a heterogeneous system in which insoluble gas enters the liquid under the action of external forces and is isolated by the liquid, that is, a body system in which the gas is dispersed in the liquid.






The formation of foam is directly related to the surface tension of the liquid. The chemical synthetic cutting fluid was prepared into a series of aqueous solutions with different concentrations, and the surface tension of the aqueous solutions with different concentrations was measured.






Through a series of experiments, it can be seen that adding cutting fluid can significantly reduce the surface tension of water. When the concentration reaches I.50h, the surface tension is reduced to the lowest.






That is, CM(binary value is I.5%. It can be seen from the characteristics of the curve that the cutting fluid is similar to a surface active agent, when the cutting fluid concentration reaches (:61(2), a large number of surface active substances are gathered on the surface of the aqueous solution, forming a single molecular film, so that the system surface tension is minimized.






The active substance has a biparental structure, one end hydrophilic, one end lipophilic, easy to form foam. The actual use of cutting fluid, the preparation of a concentration greater than CM(two values, there is a sufficient number of table active substances in the solution, when the cutting fluid is recycled in the metal processing process, contact with a large number of air, will form bubbles, the surface active substances in the cutting fluid in the gas-liquid interface orientation to form an adsorption film, so that the foam is stable. With the cutting process, some solid particles are also easy to adsorb on the surface of the foam, forming a three-phase foam, making the foam more stable.






Therefore, the main reason for the formation of the cutting fluid foam is that the active substance is actively adsorbed in the gas-liquid boundary to form a stable absorption film.














02


Principles of defoamer









The bubbles in the cutting fluid must be redistributed through the bubbles to reduce the thickness of the adsorption film in order to naturally defoaming. The redistribution of bubbles is mainly caused by different additional pressures, when the cutting fluid produces bubbles of varying sizes, the small bubble "rate radius is a large bubble for It, the additional pressure 2,r>2(r), when the two bubbles contact, the gas through the boundary from the small bubble to the big bubble diffusion, so that the small bubble becomes smaller, the big bubble becomes large and burst. Thin adsorption film thickness by drainage and evaporation, when the formation of bubbles in the cutting fluid, the liquid is concave and the additional pressure points to the center of curvature, this force causes the liquid to move causing the membrane wall to thin, so that the bubble rupture.






The natural defoaming time is long and cannot meet the requirements, but according to the above principle, we can purposefully add the corresponding material to make it defoaming quickly.






When the foam is produced, a substance with lower surface tension can be added to make it quickly penetrate into the liquid film between the foam, and the liquid with low tension due to the surface automatically flows to the liquid with high surface tension, causing the bubble stress imbalance to achieve the purpose of defoaming.






The addition of a substance with a value between 14 and 13 can capture the hydrophobic end of the surfactant, make it spread quickly, inhibit the formation of elastic film and prevent the formation of bubbles, so as to achieve the purpose of defoaming and suppressing bubbles.