Grease is a lubricant consisting of base oil, thickener and additive. Common lubricating grease of bearing include calcium base grease, sodium base grease, calcium sodium base grease, lithium base grease, aluminum base grease and molybdenum disulfide grease. The amount of grease in the bearing should be reduced to 1/3 at high speed. Too much grease will increase the working temperature of the bearing. When choosing lubricating grease, the working temperature, bearing load and speed are considered.
As the viscosity of grease is closely related to temperature, the viscosity of ball bearing grease should generally not be lower than 13 mm 2/s, and the viscosity of roller bearing grease should not be lower than 20 mm 2/s. When choosing the grease, the drop point, needle penetration and low temperature performance of the grease should be considered. General bearing working temperature should be lower than drop point grease 10 ~ 20 ℃. Elected to use synthetic grease, its working temperature should be lower than the dropping point temperature 20 ~ 30 ℃. The selection principle of grease at specific temperature has the following three points.
(1) working temperature in 50 ~ 70 ℃, in synthetic lubricants such as double fat or silicone oil grease thickened.
(2) working temperature at 70 ℃ in the low speed shaft, using sodium base grease, medium speed when choose aluminium base grease, high-speed use lithium grease or special grease.
(3) working temperature within 15 ℃, can choose high viscosity mineral oil thickening of grease, also can use silicone oil thickening of lithium grease.
2. The higher the bearing load, the higher the viscosity of the grease should be, that is, the type of grease with small needle penetration should be selected to ensure the effective formation of lubricating oil film between contact surfaces. As the bearing load decreases, the viscosity of the grease should also decrease.
The higher the speed of the bearing, the greater the frictional heating caused by the motion of the sleeve, rolling body and retaining frame, so that the d * n values of different bearing types (d is the inner diameter of the rolling bearing, unit mm); N is the bearing speed, and the unit r/min is limited to a certain range.For deep groove ball bearing, aligning ball bearing and angular contact ball bearing, it is 160,000. The cylindrical roller bearing is 120,000; The taper roller bearing is 100 000 000; The core roller bearing is 80 000; Thrust ball bearing is 40 000.
Due to the special needs of bearing using occasions, still should choose according to different the other performance of grease, such as in damp or water more, under the conditions of calcium base grease because of not easy to dissolve in water should be the preferred object, sodium based fat soluble in water should be less in the dry and water under the environmental conditions of use.