Cutting fluid must meet the four purposes of cooling, lubrication, cleaning, and rust prevention, so start from these four aspects.
1. Cool down
The water content of high water-based cutting fluid is more than 95% in normal use, and the water content is more than 97% during grinding;
2. Lubrication
Water-soluble lubricants (polyvinyl alcohol, glycerin).
3. Cleaning
The use of nonionic surfactants (such as Pingpingjia, Taigu oil) and anionic surfactants (sodium alkyl benzene sulfonate, sodium dodecyl sulfate) in the cutting fluid can significantly reduce the cutting efficiency. The effect of liquid surface tension achieves the purpose of cleaning.
4. Anti-rust
There are many varieties of water-soluble rust inhibitors, which are usually divided into organic rust inhibitors and inorganic rust inhibitors. Generally, sodium molybdate (0.05%) is used instead of sodium nitrite to reduce pollution; it is used in combination with an organic rust inhibitor (boronamine) to achieve a good anti-rust effect.
Cutting fluid maintenance mainly includes the following items:
1 . Ensure smooth flow of liquid circulation routes
Prevent miscellaneous oil and debris, especially food or cloth, from mixing into the liquid supply system, and promptly remove metal shavings, metal powder, mold slime, decomposition products of the cutting fluid itself, and grinding wheel chips from the circulation route to avoid clogging.
2 . Antibacterial
The importance of cutting fluids (especially emulsions) in inhibiting bacterial growth is well known. Regular injection of fungicides and ultra-microfiltration can be used to inhibit the growth of bacteria.
3. Cutting fluid purification
The substances that pollute the cutting fluid are mainly metal powder and fine grit powder, floating oil and free water, microorganisms and reproduction products, especially Mucorales fungi. Slick oil is a breeding ground for anaerobic bacteria. If not removed in time, the cutting fluid will soon become smelly.
4. Adjust density
Use a refractometer to detect the concentration of the cutting fluid every day and adjust it in time. The correct concentration can ensure the stability of the cutting fluid.
The solid powder contained in the cutting fluid originates from the workpiece and cutting tools. This kind of solid not only easily blocks pipelines but also causes the following hazards:
Floating oil refers to oil used in machine tool transmission and hydraulic systems that leaks into the cutting fluid system due to loose sealing of the machine tool. The harm of floating oil is that it causes certain materials in the cutting fluid system to swell and deform, interfere with the emulsification balance of the emulsion, and cause the emulsion to lose its stability. Moreover, floating oil often floats on the surface of the emulsion oil, blocking the contact between the emulsion and the air, causing the emulsion to be hypoxic, allowing anaerobic bacteria to multiply rapidly, and accelerating the spoilage of the emulsion.
After the cutting fluid is contaminated by the above three types of substances, the procedures for removing the contamination separately will be very cumbersome. An ultra-fine filtration method has been developed that can remove solid, liquid and most fungal contaminants. However, ultra-fine filtered cutting fluids are limited to microemulsions or synthetic fluids with low oil content, and their components will not form micelles or other aggregates at low concentrations.
