Three elements considered for bearing grease
Different greases have big differences in physical and mechanical properties and adaptable temperature. Different brands of bearings have different choices of grease. Therefore, when choosing a cross cylindrical roller bearing grease, you need to consider the working temperature, load and speed. Three factors.
1. Choose according to working temperature. Because the viscosity of grease is closely related to temperature, the viscosity of grease should not be less than 13mm2/s for ball bearings and 20mm2/s for roller bearings. In the specific selection of grease, the dropping point, penetration and low temperature performance of the grease should be considered. Generally, the operating temperature of the bearing must be 10-20°C lower than the dripping point of the grease. When using synthetic grease, its working temperature should be 20-30℃ lower than the dropping point temperature. The selection principle of grease at a specific temperature has the following three points: (1) When the working temperature is 50 to 70 ℃, the grease thickened with synthetic lubricating oil such as double grease or silicone oil is mostly used. (2) Sodium-based grease is mostly used in low-speed spindles with operating temperature within 70°C; aluminum-based grease is used at medium speed; lithium-based grease or special grease is used at high speed. (3) When the working temperature is less than 15℃, high-viscosity mineral oil thickened grease can be used, or silicone oil thickened lithium-based grease can be used.
2. Choose according to load. The greater the load of the cross roller bearing, the higher the viscosity of the grease should be, that is, the type of grease with a small penetration is selected to ensure that the lubricating oil film is effectively formed between the contact surfaces under the load. As the load of the cross roller bearing decreases, the viscosity of the selected grease should also decrease.
3. Choose according to working speed. Because the higher the speed of the bearing, the greater the frictional heating caused by the movement of the ring, rolling element and the cage, the dn value of different bearing types (d is the inner diameter of the rolling bearing in mm; n is the bearing speed in r/min Indicates the speed of the bearing) within a certain range, for deep groove ball bearings, self-aligning ball bearings and angular contact ball bearings, it is 160,000; cylindrical roller bearings are 120,000; tapered roller bearings are 100,000; spherical roller bearings Is 80,000; thrust ball bearing is 40,000.
When we choose grease, we should first clarify the purpose of using grease. According to the main role played by grease, grease can be roughly divided into three categories: anti-friction, protection, and sealing. Therefore, it is necessary to determine which part the grease plays the main role according to the part of the grease lubrication. Use grease that meets the requirements. As anti-friction grease, the main consideration should be the range of resistance to high and low temperature, the limit of resistance to speed, and the size of load. As a protective grease, you should focus on the metal you are in contact with, and whether the contacting medium is water vapor or chemical gas. In terms of the performance of the grease, you should focus on the indicators of metal protection, such as oxidation resistance, water resistance, etc. Aspect performance.