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It is generally believed that due to the action of metal soap or thickener, the base oil is brought to the contact surface of friction pair, and the base oil is released by external force on this surface for lubrication. This view only sees that the base oil plays a real role in lubrication, which is only put forward according to the following test results, that is, the lubricating grease prepared by thickening the same base oil with different bowl chemicals has the same friction coefficient.
Another view is that both base oil and thickener can play a lubricating role. This is based on the comparison test results of grease and separate base oil, and the relationship between the lubricating bearing performance of grease and the shear strength of blocker. A more comprehensive view is that the lubricating effect of grease is partly due to the role of base oil, but more importantly, it depends on the lubricating performance of base oil and thickener after the special combination of paste and base oil.Basic Precautions for Grease Storage
1) Thixotropy
The basic characteristic of grease is thixotropy. When an external force is applied, the flow of grease gradually softens and the viscosity decreases, but once it is at rest, the consistency increases (recovers) again after a period of time (very short). This characteristic is called thixotropy. This characteristic of grease determines that it can be lubricated in parts that are not suitable for lubricating oil lubrication, and shows its excellent performance.Basic Precautions for Grease Storage2) Viscosity
Grease is usually expressed by apparent viscosity or similar viscosity. When describing the viscosity of grease, the temperature and shear speed must be indicated. Similar viscosity indexes can be used to control its low-temperature fluidity and pumpability.Basic Precautions for Grease Storage
3) Strength limit
The strength limit of lubricating grease refers to the small shear stress required to cause the sample to start flowing, also known as the ultimate shear stress. The strength limit of grease is a function of temperature. The higher the temperature, the smaller the strength limit of grease. When the temperature decreases, the strength limit of grease becomes larger. Its size depends on the type and content of thickener and has a certain relationship with the process conditions of grease making.Basic Precautions for Grease Storage
4) Low temperature fluidity
One of the important indicators to measure the low-temperature performance of grease is the low-temperature torque, that is, the degree to which the grease blocks the rotation of low-speed flow bearing at low temperature (- 20 ° C). The Low-Temperature Torque of grease is expressed by the average value of starting torque and torque after rotating for 60mm.Basic Precautions for Grease Storage
5) Drop point the low temperature of lubricating grease when it reaches a certain fluidity under specified conditions is called drop point. The dropping point of lubricating grease is helpful to identify the type of lubricating grease and roughly estimate the high service temperature of lubricating grease. Generally speaking, for soap based grease, its service temperature should be 20 ~ 30 ° C lower than the dropping point. The higher the dropping point, the better its heat resistance.Basic Precautions for Grease Storage
