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

Cone penetration, drop point, low temperature similar viscosity and low temperature torque, pressure oil separation and high temperature steel mesh oil separation, grease extended working cone penetration, load capacity, grease oxidation stability test, grease corrosion test, grease Anti-rust test; others include: grease evaporation test, grease water resistance test, grease high temperature bearing life test, etc.

1. The cone penetration of grease

  Under the conditions of specified weight, time and temperature, the depth of the standard cone using its own weight to penetrate the grease sample, the unit is 0.1mm; the cone penetration reflects the degree of hardness and hardness of the grease, which is an important index for the selection of grease for equipment lubrication One;

2. Dropping point of grease

  The dropping point refers to the temperature point at which the grease changes from solid to liquid, in ℃; it is one of the indexes used to reflect the high-temperature performance of the grease, but the dropping point cannot determine the temperature of the grease alone. The difference in antioxidant capacity, the oxidation catalysis of the thickener type to the base oil, and the choice of antioxidant additives are also determinants of 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 of the shear stress of the grease to the shear rate calculated by the Poiseuille equation, in units of 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 necessary to select the low-temperature grease Important indicators 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 1 rpm under low temperature conditions. The measured torque can get two kinds of 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 smaller the torque, the better the low temperature performance of the grease.

4. At normal temperature pressure oil separation of grease and high temperature steel mesh oil pressure separation oil:

  The amount of base oil deposited by the grease at a certain pressure and time at room temperature, in units of w/w%; to reflect the colloidal stability of the grease at room temperature;

  High temperature steel mesh oil separation: under high temperature conditions, how much of its base weight will compress the amount of base oil in the grease, in units of w/w%; used to reflect the colloidal stability of the grease under high temperature conditions;

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

5. Grease extends working cone penetration

  Extended working cone penetration refers to the measured value of the penetration of the grease after 100,000 shears in the working device, the unit is 0.1mm; under normal circumstances, the grease will become thinner after shearing. The difference between its penetration and 60 working cones reflects the shear stability of the grease.

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

6. Four-ball grease 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 fixed cup of the load-bearing ball, and the standard steel balls above are applied with a load through the transmission device and run at the set temperature, speed and load The grease lubrication and extreme pressure performance are determined by the running state of the steel ball.

  Maximum non-seizure load PB: The maximum load at which the steel ball will not seize under lubricated conditions at a certain temperature and speed. The higher the measured value of this index, the better the lubricating performance of the grease.

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

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

7. Grease oxidation

  The ability of lubricating grease to resist the action of air (oxygen) during storage and use and keep its properties from permanent changes is called oxidation stability. As a result of the oxidation of the grease, acidic substances are produced and the metals are corroded. The commonly used oxidation experiment 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 (generally 100 hours), the oxidation of the grease is determined by the corresponding oxygen pressure drop Stability.

8. Anti-corrosion performance of grease

  The corrosion test is an index to check whether the grease is corrosive to the metal. The corrosion resistance of grease is particularly important for protective grease. Determination of grease corrosion performance Common methods are GB/T7326 copper sheet corrosion test method, GB/T0331 grease corrosion test method (T3 copper sheet, 45# steel sheet). They all insert the test metal sheet into the grease, take out the metal sheet after the specified time and temperature, observe the color change of the metal sheet, and compare with the standard color plate to judge the corrosion level or pass or fail of the grease.

9. Anti-rust performance of grease

  The anti-rust performance is used to evaluate the protection of the grease on the bearing in the presence of water or water vapor. It is of great significance for grease used in wet environments. Commonly used methods are GB/T5218 bearing static rust test: put grease into the bearing, and place the bearing in an oven at 52 ℃, relative humidity of 100%, and observe the bearing for corrosion points after 48 hours to judge the grease Anti-rust performance level. In recent years, the Emcor test method, a dynamic rust test commonly used abroad, has been introduced: immerse the bearing half of the grease in distilled water or seawater, run for 8 hours, stop for 16 hours, and observe the rust of the bearing after 7 consecutive days to remove the top grease Anti-rust performance level. This method is more demanding than the static anti-rust test conditions, and evaluates the grease with strict requirements for resistance to water and seawater.