Cooling lubricants are used in machine tools for machining or forming. Atomization on rotating tools or vaporization on hot surfaces results in vapors and mist. Cooling lubricants such as oil or emulsion are used to cool and lubricate as well as to transport away the chips during milling, turning, drilling and grinding. The use of cooling lubricants is highly advantageous but there is one key drawback: High tool speeds and temperatures disperse the cooling lubricant into fine particles in the air. According to DGUV 109-003, these particles must not exceed specific occupational limit values as they can lead to dangerous lung exposure levels. Cooling lubricant mist may also be easily flammable, so further safety measures come into effect.
Non-water-miscible cooling lubricant usually consist of mineral oils, however poly-alpha-olefins or other oils are also used. Depending on the application, additives are added to the cooling lubricants. Non-water-miscible cooling lubricants offer several advantages compared to water-miscible cooling lubricants:
Water-miscible cooling lubricants are divided into two types of emulsions and solutions and used where the priority is cooling. They consist of over 90% water and therefore largely share its physical properties.
Emulsions consist of oil, water, emulsifiers and additional additives. They are characterized by the following advantages:
In contrast to emulsions, solutions are free from mineral oils and normally consist of polymers or salts mixed with water: