What does the "extreme pressure" of grease mean?
December 31, 2020
Extreme pressure is the ability of the lubricating film to bear load without being squeezed out of the friction surface, resulting in a lack of lubrication on the friction surface.
Lubricating oil can not be analyzed by viscosity as a friction reducing performance, especially with boundary lubrication conditions, and under impact load or high temperature and high pressure load, tribochemical reaction with the surface metal to form a reactive extreme pressure film. It is mainly caused by the tribochemical reaction of the strong polarity or strong oxidation of the additives in the oil with the metal to form a tough extreme pressure film. The extreme pressure of oil products can be measured by the four-ball method, more often by the Timken machine test method: the test ring is installed on a fixed spindle and rotates at a speed of 800r/min. Apply a load to the grinding block, test the oil for about 3L, and circulate it to the contact surface of the ring block. The maximum load value without scratches is called the OK value. For example, the OK value of extreme pressure lithium grease is 156N (Nine), or 351b (lb).
The collective name of extreme pressure grease: Extreme pressure grease refers to a grease made by adding extreme pressure additives containing sulfur, phosphorus, chlorine and other active elements or other types of extreme pressure additives to ordinary grease. It has relatively high load carrying capacity and can It is suitable for the lubrication of mechanical equipment under high load conditions.
