Cutting fluid deteriorates and stinks? Corrosive? Have you paid attention to these details?
December 05, 2022
Cutting fluid is widely used in cutting process due to its cooling, lubrication, cleaning, rust prevention and other functions. Cutting fluid often shows deterioration, odor, corrosion and other problems in use. Do you know how to solve and avoid them?
Main reason for the deterioration and odor of cutting fluid
The main reason for the deterioration and odor of cutting fluid is that the cutting fluid contains a large number of bacteria, and the bacteria in the cutting fluid mainly include aerobic bacteria and hydrogen anaerobic bacteria. The aerobic bacteria live in the environment with minerals, such as water, concentrated solution of cutting fluid and oil leaked from the machine tool. Under aerobic conditions, they split into two every 20~30mn. Anaerobic bacteria exist in an oxygen free environment, split and metabolize every hour to release So2, smell of rotten eggs, and the cutting fluid turns black. When the bacteria in the cutting fluid is greater than 106, the cutting fluid will smell.
Bacteria enter the cutting fluid mainly through the following channels: 1. There is bacteria invasion in the preparation process, such as bacteria in the water used to prepare cutting fluid; 2. Bacteria in the air enter the cutting fluid; 3. Infection of cutting fluid caused by transfer of workpiece between processes; 4. Bad habits of operators, such as littering dirty things; 5. The cleanliness of machine tool and workshop is poor.
Methods for controlling bacterial growth 1. Use high-quality and stable cutting fluid; 2. The concentrated solution prepared with pure water is not only easy to prepare, but also can improve the lubricity of the cutting fluid, reduce the amount taken away by the chips, and prevent bacterial corrosion; 4. During use, the ratio of concentrated liquid in cutting fluid shall not be too low, or bacteria may grow easily; 5. As the oil used in the machine tool contains bacteria, the oil leaked from the machine tool shall be minimized to mix with the cutting fluid; 6. When the pH value of cutting fluid is 8.3~9.2, it is difficult for bacteria to survive, so new cutting fluid should be added in time to increase the pH value; 7. Keep the cutting fluid clean, and do not make the cutting fluid contact with dirty oil, food, tobacco and other contaminants; 8. Frequent use of fungicides; 9. Keep the workshop and machine tool clean; 10. If the equipment does not have a filtering device, the floating oil and dirt shall be removed regularly.
Corrosion of cutting fluid Causes of corrosion 1. The proportion of concentrated liquid in cutting fluid is low; 2. The pH value of cutting fluid is too high or too low. For example, when PH>92, it is corrosive to aluminum, so the appropriate pH value should be selected according to the metal material; 3. Contact of dissimilar metal materials; 4. Place the workpiece with paper or wood; 5. Parts stacking; 6. The number of bacteria in cutting fluid exceeds the standard; 7. The humidity of the working environment is too high.
Methods to prevent corrosion 1. Prepare cutting fluid with pure water, and the proportion of cutting fluid shall be in accordance with the recommended value in the instruction manual of the cutting fluid used; 2. If necessary, use antirust liquid; 3. Control the number of bacteria and avoid the production of bacteria; 4. Check the humidity, and pay attention to control the humidity of the working environment within the appropriate range; 5. Avoid the cutting fluid from being polluted; 6. Avoid contact with dissimilar materials, such as aluminum and steel, cast iron (containing magnesium) and copper.
