Lubricants are subject to various influences:
- mechanical influences (pressure and shear stresses at the lubrication point)
- thermal influences (heat supply or removal)
- chemical interactions with other substances (blow-by gases, nitration by fuels, friction partners, seals ...) and the environment (e.g. air, water, humidity)
- Lubricant aging
The following classification differentiates according to the physical state of the lubricant:
- liquid lubricants ( lubricating oils and cooling lubricants )
- Lubricating greases
- Solid lubricants ( e.g. graphite , ceramic powder , soft metals )
- gaseous lubricants (e.g. air )
Solid lubricants are usually mixed with grease to form a paste to allow them to adhere. They are often used as assembly paste and hot screw compounds to prevent contact corrosion from sticking to fasteners .
Important physical characteristics of lubricants include: a .:
- Aniline point (AP)
- Dropping point
- Pour point , pour point
- Flash point , fire point , ignition point
- Neutralizing power
Motor oil is very well known. It reduces the friction in reciprocating piston engines , at the same time ensures a better seal between the piston and cylinder and often takes on extensive cooling tasks. Some vehicles are therefore equipped with additional oil coolers .
A hygienically perfect industrial processing of food requires all parts of machines that come into contact with food to be lubricated with physiologically compatible lubricants, e.g. B. natural fats and oils with approval from the US Food and Drug Administration (FDA) or the Department of Agriculture. This requirement is contained in the International Food Standard (IFS) and the British Retail Consortium (BRC).
In metalworking, cutting oils and cooling lubricants (in the form of emulsions ) are used in machining production processes. Cooling lubricants are often used as a lubricant concentrate in a 3–10% emulsion with water, which is repeatedly fed into the machining process via circulating pumps.
In the sheet metal forming forming lubricants are used as oil-based forming oils with different additive packages. Ester oil-based forming oils with high-performance or EP additives are also used, which are used for more demanding forming tasks. In the area of simpler forming of large-area parts, volatile solvent-based lubricants are also often used, which evaporate when parts are further processed. As an alternative to solvent-based lubricants, there are bio-polymer lubricants, which are mineral oil-free solutions based on biogenic polymers. These are equipped with corrosion protection and water-soluble additives for the requirements of sheet metal forming. With these lubricants, as with the volatilizing lubricants, the parts no longer need to be washed, since after the forming process, almost only the corrosion protection remains on the component.
- Wilfried J. Bartz (Ed.): Rapidly biodegradable lubricants and working fluids. Expert Verlag, Böblingen 1993, ISBN 3-8169-0810-1 .
- Uwe J. Möller, Jamil Nassar: Lubricants in operation. Volume 2, Springer Verlag, Berlin / Heidelberg 2002, ISBN 3-540-41909-8 .
- Biogenic lubricants
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