What is the reason for the crystallization of cutting fluid?
May 25, 2023
The lubricating effect of metal cutting fluid (cutting fluid for short) in the cutting process can reduce the friction between the front tool face and the chip, and between the rear tool face and the machined surface, forming a partial lubricating film, thus reducing the cutting force, friction and power consumption, reducing the surface temperature and tool wear of the friction part between the tool and the workpiece blank, and improving the cutting performance of the workpiece material. During the grinding process, after adding grinding fluid, the grinding fluid infiltrates into the lubrication film between the grinding wheel, the workpiece, and the grinding debris, reducing the friction between the interfaces, preventing the wear of the cutting edge of the grinding particles and the adhesion of the chips, thereby reducing the grinding force and friction heat, improving the durability of the grinding wheel and the surface quality of the workpiece. The problem of cutting fluid crystallization often occurs in cutting fluids of synthetic systems. Generally, it is formed by excessive addition of inorganic solids, which are in a free state and accumulate during long-term storage and transportation.
Synthetic cutting fluid is made by adding and mixing chemical raw materials, and a certain amount of solid raw materials are often added, especially some crystal 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 their solubility also changes with the fluctuation of temperature. Once the temperature changes in the saturated state of water, the problem of cutting fluid crystallization may occur at any time. In the saturated state, it will also aggregate with the bumps during transportation, resulting in cutting fluid crystallization, which is sodium nitrite. 1、 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. Due to unclear crystal state, it is also impossible to analyze which substance it is 2、 The sensitivity of cutting fluid to hard water can cause discomfort between some cutting fluids and water with higher hardness, mainly reflected in the turbidity of the solution over time and a significant decrease in functionality. After drying, the substance may become crystalline. 3、 Some substances in the cutting fluid are unstable and may decompose or recrystallize under the influence of short-term high temperatures after contact with the processed metal. Another situation is that the raw materials in the cutting fluid undergo a chemical reaction, such as when caustic soda and boric acid are mixed together, a water insoluble substance is produced, which then accumulates at the bottom of the cutting fluid barrel, forming crystalline precipitation.
