There are two main types of lubricants used in rolling bearings, which are grease and oil.
There are two types of lubricants used in rolling bearings: (1) Lubricating Grease (commonly known as butter); (2). Lubricating oil (commonly known as engine oil, vehicle oil thin oil).
⑴ lubricating grease lubricating grease is composed of lubricating oil and thickener. Thickener refers to various soaps and waxes, which are dispersed in oil in the form of fiber. These fibers interweave with each other to form a net, and adsorb and fix the oil in the net, so that the oil loses its fluidity and becomes paste. The brand of lubricating grease is determined by the penetration. If the brand is large, the penetration is small; Otherwise, the penetration is large.
Penetration refers to the depth at which the cone falls into the grease under experimental conditions. It is an indicator of the hardness and softness of lubrication. The greater the penetration, the softer the grease and the smaller the consistency; The smaller the penetration, the harder the grease and the greater the consistency. Therefore, the larger the brand of grease, the harder the grease is.
① Advantages and disadvantages of grease
The utility model has the advantages of strong lubrication ability, strong adhesion ability, good sealing performance, small leakage possibility, simplified bearing sealing device, long-term operation without replacement, and extended service life.
The disadvantage is that the internal friction is large, which is not suitable for high-speed running bearings; It is difficult to replace the lubricating grease, so it is necessary to disassemble the relevant parts of the machine before replacement; The grease can not be recycled, so it is not as economical as using lubricating oil.
② Type of grease
There are 4 kinds of lubricating grease suitable for rolling bearings: calcium base grease, synthetic calcium base grease, calcium sodium base grease (bearing grease) and lithium base grease.
Calcium base grease and synthetic calcium base grease have good water resistance and can work in humid environment. The calcium base grease contains 1.5 ~ 3.5% water, which acts as a structural stabilizer in the grease and can ensure that the oil soap is not separated. But the heat resistance is poor. When the bearing temperature is high, the water in the calcium base grease is easy to evaporate and the oil soap is separated, affecting the use.
Calcium base grease is divided into five grades: 1, 2, 3, 4 and 5 according to penetration. Some calcium base grease is also added with 2 ~ 4% molybdenum disulfide.
Synthetic calcium base grease is divided into 2 and 3 grades according to penetration.
Due to the poor heat resistance of calcium base grease and synthetic calcium base grease, the specified temperature shall not be exceeded during use. When adding calcium base grease, in order to prevent the deterioration of calcium base grease, oil gun, scraper or finger should be used to add, and it is strictly prohibited to heat, melt and add.
Calcium base grease separated from oil soap or mixed with water and sundries can be used after treatment by the following methods: heat the grease to 125 ℃ to remove all the water, and filter it with gauze while it is hot to remove impurities. When it is cooled to about 90 ℃, weigh the water according to 2% of the weight of the filtered grease, add the water slowly and stir it, so that the calcium base grease can be recovered to be qualified and put into use.
Sodium base grease is resistant to high temperature and has strong adhesion. It can still be lubricated after melting, and can be reconstituted into grease after cooling. It is mainly used for lubricating parts with high temperature and not in contact with water and humid gas. Sodium base grease is divided into three grades: 2, 3 and 4 according to penetration. The working temperature of sodium base grease, No. 2 and No. 3, shall not exceed 120 ℃; No. 4 shall not exceed 135 ℃. Sodium base grease should not be used for lubricating parts greased with oil nozzle.
Sodium base grease is not resistant to water, and it is easy to emulsify and lose in case of water. For the sodium base grease that has been mixed with water to cause emulsification and deterioration, it can be treated and used by the down speed method: put the deteriorated sodium base grease into a large pot, heat it to about 140 ℃ to remove all the water, then raise the temperature to (180 ~ 200) ℃, let the oil soap mix evenly, and then cool it to 40 ℃, knead it by hand to resume use.
Calcium sodium base grease (bearing grease) has the characteristics of good water resistance of calcium base grease and high temperature resistance of sodium base grease, and its performance is between the two. It should not be used under too low operating temperature. Calcium sodium base grease can be classified into 1 and 2 grades according to penetration.
Lithium grease has good water resistance, heat resistance, mechanical safety, good anti-oxidation stability, and wide temperature range. It is a multi-purpose grease used between - 20 ℃ and 120 ℃. It can replace calcium base grease, sodium base grease and calcium sodium base grease, and is widely used in the lubrication of rolling bearings in automobiles, tractors and various mechanical equipment. Lithium base grease can be divided into four grades: 1, 2, 3 and 4 according to penetration.
In the process of storage and use, if there is a small amount of oil separation due to long storage, the lithium grease can be stirred at room temperature or evenly ground.
More about Marginal Self - Lubricating Bearings:
As a specialized manufacturer of self-lubricating bearings & bushings, Marginal Bearing is devoted to researching and producing new self-lubricating bearing materials.
Self-lubricating bearings, as the name suggests, provide their own lubrication during operation without requiring application of grease or oil lubricants. Due to this, self-lubricating bearings are also referred to as maintenance-free or greaseless bearings as they require no relubrication or grease.
An important distinction to make is that self-lubricating bearings are not bearings that come pre-applied with grease or oil lubricant – these bearings are instead referred to as prelubricated bearings. Prelubricated bearings will require relubrication at some point in their service life.
Self-lubricating bearings work by having lubricant impregnated within the sliding layer of the bearing. This lubricant can either be liquid (oil) or solid (graphite, MoS2, lead) based on the requirements of the application (such as operating temperature). As the bearing operates, the lubricant is released through pores in the sliding layer, lubricating the bearing surface. The lubricant is uniformly dispersed throughout the sliding layer and thus there is no reduction in low friction bearing performance, even if the sliding layer becomes worn. A “running-in” surface is also usually included at the top of the sliding layer to provide low friction bearing performance at start up before the impregnated lubricant reaches the bearing surface.
