Corruption of the cutting fluid will affect the equipment, working environment and personal health, and may also affect the life of the new fluid. The necessary scientific management of water-soluble cutting fluids seems a little troublesome on the surface, but due to proper management and prolonging the service life, it will save man-hours, costs and pollution to the environment.
About the corruption and deterioration of cutting fluid (also the main reason for changing the working fluid) 1. Causes of corruption and deterioration: The deterioration of water-soluble cutting fluid is the result of the rapid reproduction of microorganisms under suitable conditions, resulting in biochemical changes in the cutting fluid. Microorganisms that cause spoilage are fungi, actinomycetes, bacteria and yeast. The bacteria are numerous and widely distributed, and can be found in the atmosphere, soil, rivers, and natural objects. The following representative fouling bacteria are often found in corrupt cutting fluids:
A) P. aeruginosa is a representative strain of fish meat spoilage, and is also one of the main strains of cutting fluid spoilage. B) Sulfate-reducing bacteria, another main strain of cutting fluid that stinks, reproduces under anaerobic conditions and exists under iron filings and scale. It can reduce sulfate, generate hydrogen sulfide, and release odor; hydrogen sulfide corrodes iron to generate iron sulfide, making the cutting fluid gray-brown and black. This is the main reason why the cutting fluid should be circulated frequently, ventilated, supplemented with oxygen, removed from oil slicks, and removed rust and scale when cleaning the fluid tank. C) Yeast, Bacillus subtilis, Crescent spore bacteria produce strong enzymes, which make the cutting fluid sticky, pH value drops, and corruption. D) Penicillium is a representative bacteria for food and industrial material deterioration. E) coliforms can corrode aluminum foil and many industrial materials. 2. Conditions for the rapid reproduction of microorganisms A) Sufficient nutrient source Water-soluble cutting fluid provides sufficient organic matter (carbohydrate, mineral oil, fatty acid, fatty alcohol, etc.), minerals and trace elements, nitrogen-containing compounds (organic amine nitrate) and sulfur, phosphorus, etc. for microbial reproduction , Chlorine substances (extreme pressure agent EP). B) Oxygenophilic bacteria (sulfur bacteria, iron bacteria) - odorless anaerobes (sulfate-reducing bacteria) - malodorous facultative anaerobes (sulfate-reducing bacteria) - light odor C) temperature is higher. Bacteria should multiply at 30~37℃; mold should breed at 20~30℃. D) PH value is not alkaline enough. Bacteria are suitable for reproduction at pH 6.0~8.5; molds are suitable for reproduction at pH 4.5~6.5. When the pH is greater than 9, the probability of bacteria and mold reproduction is the lowest. 3. Phenomenon of water-soluble cutting fluid after corruption and deterioration A slight rancid smell is produced, "Monday phenomenon"; The working fluid becomes gray-brown or red; PH value and rust resistance drop suddenly and sharply; ; Decrease in processing performance; Produce odor and pollute the environment.
4. Anti-corrosion management of cutting fluid 1) Choose clean water sources: tap water and groundwater. If necessary, sterilize and adjust the water for the preparation of the water. The hardness of the water for preparation is 100~300PPM. 2) When replacing the new fluid, it is very important to thoroughly clean the fluid tank, pipeline, and machining area of the machine tool. Corruption in a few days. 3) Management of cutting fluid in use: maintain the specified concentration, and replenish new fluid in time after the cutting fluid is consumed. Keep it clean to prevent the entry of foreign objects and dust. Remove oil slicks and chips in time. Circulate the cutting fluid for at least 1~2 hours every day, especially on holidays. 4) Always test the pH value. When the pH value is lower than 8, add stock solution, fungicide and pH value adjuster according to the site conditions for adjustment; when the pH value is greater than 8.2, add stock solution for adjustment. (The reference value of PH value of water-soluble cutting fluid) 8 — 8.5 — 9.3 — 10. When the pH value is greater than 9, bacteria and molds multiply slowly, so the international standard dilution PH=9 and stock solution PH=10 are the upper limit standards. According to the workload and season, formulate the replacement cycle, do not wait for corruption before replacing.
