Cutting fluids are widely used in cutting processes due to their functions of cooling, lubrication, cleaning and rust prevention.
In the use of cutting fluid, there are often problems such as deterioration, odor, corrosion, foam generation, and skin allergies of the operator. Combining our practical experience in work, we will talk about the problems and countermeasures in the use of cutting fluid.
1. The problem of cutting wave deterioration and smell
The cutting fluid contains a lot of bacteria, and the bacteria in the cutting fluid mainly include aerobic bacteria and anaerobes. Aerobic bacteria live in environments with minerals, such as water, concentrated fluid of cutting fluid, and oil leaked from machine tools. Under aerobic conditions, they split into two every 20-30 minutes. The anaerobic bacteria live in an environment without oxygen, split into two per hour, metabolize and 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 become smelly.
(1) Bacteria enter the cutting fluid mainly through the following channels:
*Bacteria invade during the preparation process, such as bacteria in the water used to prepare the cutting fluid.
*Bacteria in the air enter the cutting fluid.
*Transfer between work processes causes cutting fluid infection.
* Bad habits of operators, such as littering.
*The cleanliness of the machine tool and workshop is poor.
(2) Methods of controlling bacterial growth:
*Use high-quality, stable cutting fluid.
*Preparing concentrated liquid with pure water is not only easy to prepare, but also can improve the lubricity of cutting fluid, reduce the amount taken away by chips, and prevent bacterial erosion.
*When using, control the ratio of concentrated liquid in the cutting fluid not to be too low, otherwise it is easy to cause bacteria to grow.
*Because the oil used in the machine tool contains bacteria, it is necessary to minimize the oil leaked from the machine tool into the cutting fluid.
*When the pH of the cutting fluid is between 8.3 and 9.2, it is difficult for bacteria to survive, so new cutting fluid should be added in time to increase the pH.
*Keep the cutting fluid clean and do not make the cutting fluid come in contact with dirt, oil, food, tobacco, etc.
*Fungicides are often used.
* Keep the workshop and machine tools clean.
*If the equipment does not have a filtering device, the oil slick should be regularly skimmed to remove dirt.
2. The corrosion problem of cutting fluid
(1) Causes of corrosion
1) The proportion of concentrated liquid in cutting fluid is low.
2) The pH value of the cutting fluid is too high or too low. For example, when PH>9.2, it has corrosive effect on aluminum. Therefore, the appropriate pH value should be selected according to the metal material.
3) Contact with dissimilar metal materials.
4) Put the work piece on a paper or wooden pad.
5) Stacking parts.
6) The number of bacteria in the cutting fluid exceeds the standard.
7) The humidity of the working environment is too high.
(2) Methods to prevent corrosion
1) Prepare cutting fluid with pure water, and the ratio of cutting fluid should be used according to the recommended value in the cutting fluid manual.
2) If necessary, use anti-rust liquid.
3) Control the number of bacteria and avoid the production of bacteria.
4) Check the humidity, and pay attention to controlling the humidity of the working environment within a proper range.
5) Avoid contamination of cutting fluid.
6) Avoid contact with dissimilar materials, such as aluminum and steel, cast iron (containing magnesium) and copper.