Cutting fluid is widely used in cutting processing because of its functions of cooling, lubricating, cleaning and rust prevention. When cutting fluid is used, problems such as deterioration, odor, corrosion, foaming and operator skin allergies often arise. Let’s talk about the problems and countermeasures related to the use of cutting fluid based on our practical work experience.
1. The problem of deterioration and smell of cutting waves
The main reason for the deterioration and odor of cutting fluid is that the cutting fluid contains a large number of bacteria. The bacteria contained in the cutting fluid mainly include aerobic bacteria and anaerobic bacteria. Aerobic bacteria live in mineral environments, such as water, cutting fluid concentrates, and oil leaks from machine tools. Under aerobic conditions, they divide in two every 20 to 30 minutes. Anaerobic bacteria live in an oxygen-free environment, divide in half every hour, metabolize and release SO2 which smells like rotten eggs and the cutting fluid turns black. When the number of bacteria in the cutting fluid is greater than 106, the cutting fluid becomes smelly.
(1) Bacteria mainly enter the cutting fluid through the following channels:
1) Bacteria invade during the preparation process, such as bacteria in the water used to prepare the cutting fluid.
2) Bacteria present in the air enter the cutting fluid.
3) Transferring parts between processes causes cutting fluid infection.
4) Bad operator habits, such as throwing trash.
5) The cleanliness of machine tools and workshops is poor.
(2) Methods for controlling bacterial growth
1) Use stable, high-quality cutting fluid.
2) Using pure water to prepare a concentrated solution is not only easy to prepare, but also improves the lubricity of cutting fluid, reduces the amount carried away by chips, and prevents bacterial erosion.
3) When using, it is necessary to control the ratio of concentrated liquid in the cutting fluid so that it is not too low, otherwise it is easy for bacteria to grow.
4) Since the oil used in machine tools contains bacteria, it is necessary to minimize the leakage of machine tool oil mixed with cutting fluid.
5) When the pH value 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 value.
6) Keep the cutting fluid clean and do not allow the cutting fluid to contact dirty oil, food, tobacco and other contaminants.
7) Use fungicides frequently.
8) Keep the workshop and machine tools clean.
9) If the equipment does not have a filtering device, the floating oil should be skimmed off regularly and the dirt removed.
2. The problem of cutting fluid corrosion
1. Causes of corrosion
1) The proportion of concentrated liquid in the cutting fluid is small.
2) The pH value of the cutting fluid is too high or too low. For example, when PH>9.2, aluminum will be corroded. Therefore, the appropriate pH value should be selected according to the metal material.
3) Contact with different metallic materials.
4) Use paper or wood to cushion the piece.
5) Stacking of parts.
6) The number of bacteria in the cutting fluid exceeds the standard.
7) The humidity in the working environment is too high.
2. Methods to prevent and control corrosion
1) Prepare the cutting fluid with pure water, and the proportion of cutting fluid should be used according to the value recommended in the instruction manual of the cutting fluid used.
2) Use anti-rust fluid if necessary.
3) Control the number of bacteria and prevent their appearance.
4) Check the humidity and be sure to control the humidity of the working environment within the appropriate range.
5) Avoid contamination of cutting fluid.
6) Avoid contact with dissimilar materials, such as aluminum and steel, cast iron (containing magnesium) and copper, etc.
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