What is the reason for the crystallization of cutting fluid?
July 26, 2022
The lubricating effect of metal cutting fluid (referred to as cutting fluid) in the cutting process can reduce the friction between the rake face and the chip, the flank face and the machined surface, and form part of the lubricating film, thereby reducing the cutting force, friction and Power consumption, reduce the surface temperature and tool wear of the friction part between the tool and the workpiece blank, and improve the cutting performance of the workpiece material. In the grinding process, after adding the grinding fluid, the grinding fluid penetrates into the grinding wheel abrasive particle-workpiece and abrasive particle-abrasive debris to form a lubricating film, which reduces the friction between the interfaces and prevents the abrasive particles from wearing and sticking to the cutting edge. chips, thereby reducing grinding force and frictional heat, improving the durability of the grinding wheel and the surface quality of the workpiece. The crystallization problem of cutting fluid mostly occurs in the cutting fluid of synthetic system. Generally, it is formed by excessive addition of inorganic solids, in a free state, and aggregation during long-term storage and transportation.
Synthetic cutting fluid is more or less made by adding and mixing chemical raw materials, in which a certain amount of solid raw materials are often added, especially some crystalline raw materials, such as: sodium carbonate, sodium hydroxide, sodium nitrite, sodium tripolyphosphate, EDTA, boric acid , borax, thiourea, phosphorus pentoxide, sodium silicate, benzotriazole, citric acid, etc. These raw materials have a certain solubility, and the solubility will also change with the fluctuation of temperature. In the saturated state of water, once the temperature changes, the problem of cutting fluid crystallization may occur at any time. In the saturated state, cutting fluid crystallization will also occur due to the accumulation of bumps during transportation, which is sodium nitrite. First, the precipitation of salts in the cutting fluid is basically caused by the high concentration of the cutting fluid used or the high content of a certain salt additive in the cutting fluid. Since the state of the crystals is not clear, it is impossible to analyze what is a substance. , Second, the sensitivity of cutting fluid to hard water. Some cutting fluids will not adapt to water with higher hardness, which is mainly reflected in the turbidity of the solution after a long time, and the function is obviously reduced. After drying, the substance may crystallize. Third, some substances in the cutting fluid are unstable. After contacting the processed metal, they will decompose or recrystallize under the influence of a short-term high temperature. Another situation is that the raw materials in the cutting fluid undergo a chemical reaction. For example, when caustic soda and boric acid are mixed together, a water-insoluble substance will be produced, and then this substance will accumulate at the bottom of the cutting fluid bucket to form crystalline precipitation.
