Through different tests, different technical indicators of lubricating grease can be determined. These technical indicators can predict the actual working performance of lubricating grease to a certain extent. Therefore, these technical indicators have also become an important reference for the selection of lubricating grease.

Penetration, dropping point, low temperature similar viscosity and low temperature torque, pressure oil separation and high temperature stencil oil separation, grease extended work penetration, load carrying capacity, grease oxidation stability test, grease corrosion test, grease Others include: grease evaporation test, grease anti-water spray test, grease high temperature bearing life test, etc.

1. Cone penetration of grease

  Under the conditions of specified weight, time and temperature, the depth of the standard cone penetrating the grease sample by its own weight, the unit is 0.1mm; the cone penetration reflects the degree of softness and hardness of the grease, which is one of the important indicators for the selection of grease for equipment lubrication. one;

2. Dropping point of grease

  Dropping point refers to the temperature point at which grease changes from solid state to liquid state, in °C; it is one of the indicators used to reflect the high temperature performance of grease, but dropping point cannot determine the service temperature of grease alone. Differences in antioxidant capacity, oxidative catalysis of base oil by thickener type, and selection of antioxidant additives are also factors that determine the temperature at which the grease is used.

3. Low temperature similar viscosity and low temperature torque of grease

Low temperature similar viscosity:

  It is the ratio between the shear stress of the grease and the shear rate calculated by the Poiseuille equation, in poise or Pa s (1 poise = 0.1 Pa s); it is used to reflect the low temperature flow performance of the grease, and it is the key to select the low temperature grease. An important index for reference; at the same temperature, the smaller the viscosity value, the better the low temperature performance.

Low temperature torque:

  Low temperature torque refers to the torque required to block the outer ring of the bearing when the standard open 204 ball bearing filled with grease rotates at 1rpm under low temperature conditions. The measured torque can be obtained in two types: starting torque and rotating torque. The unit is g·cm; it is used to reflect the working ability of the grease at low temperature. Similarly, the lower the torque, the better the low temperature performance of the grease.

4. The normal temperature pressure oil separation of lubricating grease and the high temperature steel mesh oil separation pressure oil separation:

  The amount of base oil precipitated by the grease under a certain pressure and time at room temperature, in w/w%; it is used to reflect the colloidal stability of the grease at room temperature;

  High temperature steel mesh oil separation: under high temperature conditions, how much the base oil in the grease is pressed out by its own weight, in w/w%; it is used to reflect the colloidal stability performance of the grease under high temperature conditions;

Studies have shown that the poor stability of the grease colloid can lead to the loss of oil separation during the operation of the grease, thereby affecting the operating life of the bearing.

5. Grease prolongs the penetration of the work

  Extended working penetration refers to the measured value of the penetration of the grease after 100,000 shears in the working machine, the unit is 0.1mm; under normal circumstances, the grease will be thinned by shearing. The difference between it and 60 working penetrations reflects the shear stability of the grease.

Studies have shown that the loss of grease with poor shear stability in high-speed and long-term running bearings is serious, which will affect the service life of the grease.

6. Grease four-ball test

Four-ball test principle:

  The three standard steel balls under the test head are fixed as load-bearing parts, and the grease is filled in the load-bearing ball fixing cup, and the upper standard steel balls are loaded through the transmission device, and run under the set temperature, speed and load , The performance of grease lubrication and extreme pressure is determined by the running state of the steel ball.

  Maximum non-seize load PB: Under a certain temperature and rotation speed, the maximum load that the steel ball does not seize in the lubricated state, the higher the measured value of this index, the better the lubricating performance of the grease.

  Sintering load PD: The load is gradually increased at a certain temperature and rotation speed. When the upper steel ball and the lower steel ball are sintered at high temperature due to excessive load, the load that the equipment has to stop running is the sintering load. The higher the sintering load, the higher the sintering load. The better the extreme pressure lubrication performance of the grease.

  Wear track d: Under a certain temperature, speed, load and operating time, the diameter of the wear scar on the surface of the load-bearing steel ball due to friction is the wear track. The smaller the wear track, the better the anti-wear ability and lubricity of the grease.

7. Oxidation of grease

  The ability of a grease to resist the action of air (oxygen) during storage and use without permanent changes in its properties is called oxidation stability. The result of grease oxidation leads to the production of acidic substances that corrode metals. The commonly used oxidation test method is the aerobic bomb method, namely SH/T0325. It is to put a certain amount of grease into an oxygen bomb filled with oxygen pressure and undergo oxidation at a temperature of 99 ° C. After a specified time (usually 100 hours), the oxidation of the grease is determined by the corresponding oxygen pressure drop. stability.

8. Grease anti-corrosion performance

  The corrosion test is an indicator to check whether the grease corrodes the metal. The anti-corrosion properties of the grease are particularly important for protective greases. The commonly used methods for determining the corrosion performance of grease are GB/T7326 copper sheet corrosion test method and GB/T0331 grease corrosion test method (T3 copper sheet, 45# steel sheet). They all insert the test metal piece into the grease, take out the metal piece after the specified time and temperature, observe the change of the color of the metal piece, and compare it with the standard color plate to judge the corrosion level of the grease or whether it is qualified or not.

9. Anti-rust performance of grease

  Anti-rust performance is used to evaluate the protection of grease to bearings in the presence of water or water vapor. Important for greases used in wet environments. The commonly used method is GB/T5218 bearing static anti-rust test: put the grease into the bearing, put the bearing in an oven at 52 ° C and a relative humidity of 100%, and observe whether the bearing has corrosion points after 48 hours to judge the grease. rust resistance performance level. In recent years, the dynamic anti-rust test commonly used abroad has been introduced, namely the Emcor test method: immerse half of the bearing in distilled water or seawater after being greased, run for 8 hours, stop for 16 hours, and observe the rust condition of the bearing after 7 consecutive days to remove the top grease. rust resistance performance level. This method is more severe than the static anti-rust test conditions, and is used to evaluate greases with strict requirements against water and seawater.