The role of lubrication Reducing friction is one of the main purposes of lubricating oil, but in addition to reducing friction, lubricating oil has other functions, such as lubricating oil film can prevent rust and prevent metal from being corroded. Lubricating oil can also play a cleaning role. The impurities inside the equipment are like the toxins in our body, which are removed from the oil through the filter element. Cooling effect: friction between metals generates heat, and lubricating oil flows through the metal surface to take away heat. Three states of lubrication There are three states of lubrication: full film lubrication, boundary lubrication, and mixed lubrication. They are in three different states, but all rely on lubricating oil to lubricate and resist wear. Full-film lubrication Full film lubrication is divided into two types – hydrodynamic lubrication and elastohydrodynamic lubrication. Hydrodynamic lubrication refers to: two sliding friction surfaces that move relative to each other, and a layer of fluid lubricating film generated by means of relative speed completely separates the two friction surfaces to avoid dry friction and wear caused by their direct contact. Elastohydrodynamic lubrication is similar to hydrodynamic lubrication, and the contact surfaces are separated by a layer of fluid lubricating film. The difference is that the relative motion between the contact surfaces is rolling, and the pressure of the formed full-film lubricating film is greater than that of hydrodynamic Lubrication, resulting in a thinner lubricating separation film than in hydrodynamic lubrication. Even for metals with high processing precision, the surface is not flat and smooth. Under the microscope, we can see that the metal surface is actually pitted, and the burrs are protrusions that we can already detect with the naked eye, while those higher metals under the microscope Raised parts are peaks that are hard to see with the naked eye but are important for lubrication. In order to achieve full film lubrication, the thickness of the lubricating film must exceed the height of these peaks, completely separate them, and avoid peak contact between the two contact surfaces. It can realize full-film lubrication, which is the best lubrication state, and can realize the most effective protection for the mechanical contact surface. Boundary lubrication Although full film lubrication is ideal, a complete lubricating film may not be formed in some cases, such as frequent machine start and stop, impact load, speed, and load factors are not enough to form full film lubrication, etc. These conditions will cause boundary lubrication . It is good to be able to form a complete lubricating film, but when the conditions are not enough, a complete lubricating film cannot be formed or the lubricating oil film becomes thinner (at high temperature), the critical point before the transition from liquid friction to dry friction (direct contact between friction surfaces) occurs The state is boundary lubrication. Therefore, in combination with the structure and use of machinery, some equipment requires the use of extreme-pressure lubricants, which contain extreme-pressure additives (EP: extreme-pressure additives) or anti-wear agents (AW: anti-wear additives). To achieve full film lubrication, these additives play a role in protecting the mechanical surface when boundary lubrication occurs. These additives can be adsorbed on the metal surface to form a protective layer to avoid metal wear. When boundary lubrication occurs, it’s all about extreme pressure additives to protect metal surfaces. Compared with full-film lubrication, the friction of the lubricant film generated during boundary lubrication is greater, and the heat generated is also more, but complete dry friction is avoided. Mixed lubrication The mixed lubrication state refers to the situation where full-film lubrication and boundary lubrication are mixed. As we mentioned earlier, if the peak point of the metal surface is higher than the lubricating oil film, it will contact each other. In mixed lubrication, although most of the area is under full-film lubrication, when these peaks come into contact, localized boundary lubrication occurs.  

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