classification of cutting fluids, cutting fluids are divided into two categories according to the chemical composition of oil products: water-insoluble (oil-based) fluids and water-soluble (water-based) fluids. Water-based cutting fluids can be divided into emulsion, semi-synthetic cutting fluids and synthetic cutting fluids. Composition of emulsion: mineral oil 5-8%, fatty acid -3%, emulsifier 15-25%, antirust agent -5%, preservative < 2%, defoamer < 1% Semi-synthetic: mineral oil -3%, fatty acid 5-3%, extreme pressure agent -2% and surfactant -5. Compared with oil-based cutting fluid, water-based cutting fluid has relatively poor lubrication performance and good cooling effect. Slow cutting requires strong lubricity of cutting fluid. Generally speaking, cutting oil is used when the cutting speed is lower than 3m/min. Cutting oil containing extreme pressure additives is effective when the cutting speed does not exceed 6m/min, regardless of the cutting process of any material. In high-speed cutting, due to the high calorific value and poor heat transfer effect of oil-based cutting fluid, the temperature in the cutting area will be too high, which will lead to smoke and fire in the cutting oil, and because the workpiece temperature is too high, it will cause thermal deformation and affect the machining accuracy of the workpiece, so water-based cutting fluid is often used. Emulsions combine the lubricity and rust resistance of oil with the excellent coolability of water, and at the same time have good lubricity and coolability, so they are very effective for high-speed and low-pressure metal cutting with a lot of heat generation. Compared with oil-based cutting fluid, emulsion has the advantages of great heat dissipation, cleanability, economy brought by dilution with water, and is beneficial to the health and safety of operators, which makes them happy to use it. In fact, emulsion can be used for almost all light and medium-load cutting and most heavy-load machining except materials that are particularly difficult to machine. Emulsion can also be used for all grinding except complex grinding such as thread grinding and groove pitting. The disadvantage of emulsion is that it is easy to breed bacteria and molds, and the effective components in emulsion are decomposed chemically to stink and deteriorate. Therefore, organic fungicides with low toxicity should generally be added. The advantages of chemically synthesized cutting fluid are economy, fast heat dissipation, strong cleanability, excellent workpiece visibility, easy control of machining size, and stronger stability and anti-corruption ability than emulsion. Poor lubricity will cause adhesion and wear of moving parts of machine tools. Moreover, viscous residues left by chemical synthesis will affect the movement of machine parts and rust the overlapping surfaces of these parts. 3. Generally, water-based cutting fluid should be selected under the following circumstances: for places where oil-based cutting fluid has potential fire hazards; High-speed and large feed cutting make the cutting area exceed the occasions of high temperature, intense smoke and fire danger. When water-based cutting fluid is required to be used in consideration of the process before and after. It is hoped to reduce the pollution and dirt around the machine tool caused by oil splashing, oil mist and diffusion, so as to keep the operating environment clean. Considering the price, for some cutting processes in which the surface quality of machinable materials is not high, the general water-based cutting fluid can meet the use requirements and greatly reduce the cutting fluid cost. When the tool's durability accounts for a large proportion of cutting economy (such as expensive tools, difficulty in sharpening tools, long auxiliary time for loading and unloading, etc.); The machine tool has high precision, and water is absolutely not allowed to be mixed (to avoid corrosion); The lubrication system and cooling system of machine tools are easy to collude with each other, and the waste liquid treatment equipment and conditions are not available. Oil-based cutting fluid should be considered. It should be a cutting fluid with water as the heating medium. Water-based cutting fluid is a cutting fluid in which the oil agent is diluted with a large amount of water, usually containing 5% to 2% of the oil agent, and its dosage accounts for about 95% of all cutting fluids. Water-based cutting fluids are generally divided into emulsion (Soluble Oil), microemulsion and chemical aqueous solution. The latter two are called semi-synthesis and total synthesis in the market.