Abstract: This article discusses the differences in the use of lubricating grease and lubricating oil, the principles for selecting lubricating grease, and introduces the scope of application of common lubricating grease in agricultural machinery. To improve the lubrication quality of agricultural machinery and reduce the occurrence of malfunctions.

The operation of agricultural machinery cannot be separated from the participation of lubricants. Improper use of lubricants can cause early wear and even scrap of mechanical parts. The lubricants on agricultural machinery mainly include lubricating oil, gear oil, and grease. According to the different working characteristics of each friction pair on the machine, the corresponding lubrication method and materials are selected. Lubricating grease is an ideal lubricating material for friction pairs with high load-bearing capacity and inconvenient oil tank installation, such as wheel hub bearings in tractor chassis. According to statistics, there are nearly 40 parts of a tractor chassis that require lubrication with grease. Therefore, lubricating grease plays an important role in the lubrication of agricultural machinery.

1 Characteristics of lubricating grease in use

1.1 Strong pressure resistance

Lubricating grease is composed of base oil, thickener, and additives. Disperse different thickeners into liquid lubricating oil to form a stable solid and semi-solid lubricant. The adhesion on metal surfaces is stronger than that of lubricating oil. Different lubricating grease thickeners have their own characteristics. Some lubricating greases are not afraid of water, some are not afraid of moisture, and some have good heat resistance and can adapt to very low working temperatures. To meet the needs of work, different additives are used in different parts to form a strong lubricating film that can withstand high pressure. Calcium based grease Z used in agricultural machinery is not afraid of water, and most parts of the chassis that come into direct contact with water use calcium based grease; File based lubricating grease has good temperature resistance and is commonly used in agricultural machinery; Graphite calcium based grease with added graphite has extremely strong pressure resistance, which is required for steel plate springs in construction machinery.

1.2 Good buffering performance

Tractors and other agricultural machinery need to travel on various complex field roads, and when the direction of movement and load size change, they generate significant impact or vibration. Lubricating grease at the main pin of the steering knuckle, thrust bearing, wheel 9 bearing, and transmission shaft plays a buffering role and can reduce mechanical vibration.

1.3 No loss

Lubricating grease for certain key parts of agricultural machinery should be able to be applied to vertical surfaces, and under the centrifugal force of high-speed rotation, it should not be lost at a certain high temperature, and should maintain sufficient thickness to ensure reliable lubrication, such as wheel hub bearings and transmission shafts. Generally, file based lubricating grease has this function.

1.4 Good sealing and protection

Lubricating grease not only provides lubrication, but also serves a sealing function to prevent the invasion of moisture, dust, impurities, and corrosive substances, keeping the friction surface clean and free from corrosion.

1.5 Good salary and warmth

The hardness of good lubricating grease does not change significantly with temperature, while the hardness of calcium based grease and composite calcium based grease is not greatly affected by temperature changes. This is the main characteristic that distinguishes good lubricating grease from lubricating oil.

1.6 Water resistance

Tractors and other agricultural machinery can operate normally as long as they are not submerged in water through the exhaust pipe. The lubricating grease at the chassis and water contact parts should not be afraid of water. Calcium based grease is based on water as the skeleton, and is usually added to parts of the chassis that are prone to direct contact with water.

2 Principles for selecting lubricating grease

2.1 Working temperature

The higher the working temperature, the shorter the service life of the lubricating grease. Generally, when the temperature of a bearing increases by 10-15 ℃, the lifespan of the lubricating grease decreases by about half. So, for friction parts with high working temperatures, it is necessary to choose lubricating grease with good oxidation stability, low thermal evaporation loss, high drip point, and low oil separation; For friction parts with lower working temperatures, it is necessary to choose lubricating grease with good low-temperature starting performance and relatively low Hertz.

2.2 Movement speed

Bearings are usually represented by the speed factor "DN" to indicate the speed at which the grease is suitable. Among them, D represents the inner diameter of the bearing (mm), and N represents the bearing speed (r/min).

2.3 Load bearing capacity

For high-power tractors, lubricating grease with higher viscosity should be used. If choosing lubricating grease with extreme pressure additives, disulfide keys, or graphite.

2.4 Environmental conditions

Mainly considering factors such as humidity, dust, and corrosiveness of lubrication parts, special performance lubricating grease should be selected for special environments.

3 Scope of application of common lubricating greases

3.1 Calcium based lubricating grease

Because it contains about 18% white ash, it is called calcium based grease. The colors of calcium based grease include light yellow and dark brown. It uses water as a binder and contains 0.5% to 3% moisture. The main characteristic of Z is that it is insoluble in water and suitable for working in areas that frequently come into contact with water or moisture. The working temperature does not exceed 40-60 ℃ and the speed is below 1500r/min. Such as the transverse and straight tie rods of the car steering system, the main pin of the steering knuckle, and the outer ring part of the gear rack type steering gear; The ball joints of the upper and lower control arms of the driving system are parts that are prone to low load, low speed, low operating temperature, and water contact.

3.2 Calcium sodium based lubricating grease

The color is yellow and dark brown, made by mixing calcium soap and sodium soap (caustic soda) in a ratio of 3.4-4:1. The performance is between calcium based grease and sodium based grease, with better water resistance than sodium based grease (sodium based grease is sensitive to water and moisture). It has stability in damp and low moisture conditions, but is not suitable for parts in direct contact with water. The drop point is 140 ℃, and the working temperature of the friction part should not exceed 100 ℃. The disadvantage is poor performance (hardening) under low temperature conditions. The normal operating temperature of the engine coolant is 80-90 ℃. The temperature at the water pump shaft of the engine is below 80 ℃, and the working environment is humid without moisture. Therefore, calcium sodium based grease is often used at the water pump shaft of the engine.

3.3 Composite calcium based grease

It is made from a medium viscosity mineral oil thickened with 12 calcium acetate complex of high fatty acid calcium soap as a thickener. It does not use water as a blending agent, so it avoids the disadvantages of not being resistant to high temperatures, high speeds, and poor stability of the body and colloids. Composite calcium based grease has a high drop point, is not afraid of high-speed rotation, and has good body stability and colloidal stability. Suitable for lubricating high load components under high temperature and humid conditions, such as automotive wheel bearings.

3.4 General file base lubricating grease

Universal Kenji lubricating grease uses fatty acid file soap and high-grade fatty acid potassium soap as thickeners, with a color similar to calcium based lubricating grease. It is made by thickening the lubricating oil with fatty acid file soap, adding active ingredients such as chlorine, phosphorus, and sulfides, and adding anti-wear additives, anti-oxidation and anti rust additives. It can generate a covering layer between metal surfaces under heavy pressure conditions, which not only bears the load but also prevents friction welding of metal parts. It has good mechanical stability, colloid stability, rust prevention, oxidation stability, and water resistance, and is suitable for lubricating various friction parts such as car wheel bearings, water pumps, generators, etc. at working temperatures of -30~120 ℃. This grease is widely recommended for domestic and imported vehicles.

3.5 Extreme Pressure Composite File Base Lubricating Grease

Good water resistance, heat resistance, rust prevention, mechanical stability, and extreme pressure resistance, suitable for high temperature and high load mechanical equipment operating at temperatures ranging from -20 to 160 ℃.

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2025 August 3rd Week FK Product Recommendation:

Pillow Block:

A pillow block bearing (or plummer block) is a mounting used to support a rotating shaft with the use of bearings and various accessories. The assembly consists of a mounting block which houses a bearing. The block is mounted to a foundation, and a shaft is inserted, allowing the inner part of the bearing/shaft to rotate. The inside of the bearing is typically 0.025 millimetres (0.001 in) larger diameter than the shaft to ensure a tight fit. Set screws, locking collars, or set collars are commonly used to secure the shaft. Housing material for a pillow block is typically made of cast iron or cast steel.

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