Types of coolant lubricants
Based on the DIN 51385 standard, coolant lubricants may be subdivided into the main groups of non-water-miscible and water-miscible coolant lubricants, with the water-miscible types being subdivided again into emulsifiable and water-soluble coolant lubricants.
The non-water-miscible coolant lubricants are supplied as ready-to-use products; the water-miscible ones are usually available as a concentrate. Prior to use, the concentrate is diluted with water to form a water-mixed coolant lubricant. Coolant lubricant emulsions are generated from emulsifiable coolant lubricants; coolant lubricant solutions are generated from the water-soluble ones.
Water-miscible coolant lubricants
Water-miscible coolant lubricants may be subdivided into emulsions and solutions. They are primarily used when a good cooling effect is more important than a good lubricating effect. They consist of more than 90 % water and largely have the same physical properties.
Emulsions
Emulsions consist of oil, water, emulsifiers and other additives. The task of the emulsifiers is to disperse the oil in the water, so that after mixing with water a stable oil-in-water emulsion is generated.
Due to their good cooling effect and their low procurement price, coolant lubricant emulsions are widespread in industry.
One drawback compared to non-water-miscible coolant lubricants is their bad resistance to microorganisms. Fungal and bacterial attack, etc. impair the corrosion-protection behaviour of the emulsions and the hygienic boundary conditions for the operating personnel diminish considerably. Furthermore, attack by microorganisms causes the emulsion to lose stability, which can lead to operational disruptions.
Solutions
In contrast to emulsions, solutions are free of mineral oils. The concentrate usually consists of polymers or salts. As the concentrate is molecularly dissolved in water, no emulsifiers are required for even distribution of the concentrate. To increase performance, additives may be used in the solutions. Solutions are characterized among other things by their good cooling properties. As no emulsifiers are used, foam problems are less likely to occur during use and the resistance to microorganisms is better than with emulsions.
Drawbacks include the bad lubricating properties of the solutions as well as the tendency of the solutions to wash off lubricants and to have an adhering effect.
Additives
The properties of coolant lubricants may be changed considerably through the use of additives. The goal is to strengthen the positive properties of the coolant lubricant, minimize the negative properties and thus to generate the desired functional characteristics. Depending on the intended use of the coolant lubricant, the amount and type of additives may be varied. The various types of additives may be roughly subdivided into the following groups according to their function:
- Additives which change the physical properties of the coolant lubricant
- Additives which change the chemical properties of the coolant lubricant
- Tribologically effective additives which change the friction conditions
Coolant lubricants in use
We have made additional items available for the use of coolant lubricants when grinding parts (workpieces): Coolant lubricant supply, grinding burn, errors during grinding, grinding wheels, CNC grinding machines, coolant lubricant filtration systems
Source: Klocke, F.; König, W.: Fertigungsverfahren 1 (2008); Klocke, F.; König, W.: Fertigungsverfahren 2 (2005); Denkena, B.; Tönshoff, H. K.: Spanen (2011); Hipler, F.: Chemie gegen Reibung und Verschleiß (2003); Richtlinie VDI 3397, Blatt 1 (2007)
