Classification of different greases
(1) Calcium-based grease. It is made of calcium soap thickened with medium viscosity petroleum lubricating oil produced by the reaction of natural fat or synthetic fatty acid with calcium hydroxide.
The dropping point is between 75 and 100 ° C, and its service temperature cannot exceed 60 ° C. If this temperature is exceeded, the grease will become soft and even structural damage cannot be guaranteed.
It has good water resistance, and is not easy to emulsify and deteriorate in water. It is suitable for lubrication of various mechanical parts in wet environments or in contact with water.
It has a short fiber structure, good shear stability and thixotropic stability, so it has good lubricating properties and protective properties.
(2) Sodium-based grease is made of natural or synthetic fatty acid sodium soap thickened medium viscosity petroleum lubricating oil.
It has a long fiber structure and good stringiness, and can be used on rolling or sliding bearings with high vibration and high temperature. Especially suitable for the lubrication of low-speed, high-load machinery. Because of its higher dropping point, it can work at 80% or higher for a longer period of time.
Sodium-based grease can absorb water vapor and delay the penetration of water vapor to the metal surface. Therefore it has a certain degree of protection.
(3) Calcium and sodium base grease. Has the characteristics of calcium-based and sodium-based grease.
It has the water resistance of calcium-based grease and the temperature resistance of sodium-based grease. The dropping point is about 120 ℃, and the use temperature range is 90 ～ 100 ℃.
It has good mechanical safety and pump delivery, and can be used on rolling bearings under less humid conditions.
The most commonly used are bearing grease and calender grease, which can be used to lubricate medium-load motors, blowers, chassis, hubs and other parts of rolling bearings.
(4) Lithium grease. It is made of natural fatty acid (stearic acid or 12-hydroxystearic acid) lithium soap thickened petroleum lubricating oil or synthetic lubricating oil. Made of synthetic fatty acid lithium soap thickened petroleum lubricating oil, called synthetic lithium base grease.
Because lithium-based greases have many excellent properties, they are widely used for bearing lubrication of aircraft, automobiles, machine tools and various mechanical equipment. The dropping point is higher than 180 ℃, and it can be used in a long-term environment around 120 ℃. It has good mechanical stability, chemical stability and low temperature, and can be used on high-speed mechanical bearings. It has excellent water resistance and can be used on mechanical parts that are wet and in contact with water. Lithium soap has strong thickening ability. After adding extreme pressure, anti-rust and other additives to the grease, it is made into multi-effect long-life grease, which has a wide range of uses.
(5) Compound calcium-based grease. The compound calcium soap made of fatty acid calcium soap and low molecular acid calcium salt is made of thickened medium viscosity petroleum lubricating oil or synthetic lubricating oil. Good temperature resistance, the drop point of grease is higher than 180 ℃, and the operating temperature can be around 150 ℃.
Has good water resistance, mechanical stability and colloidal stability. It has good extreme pressure and is suitable for lubrication of mechanical bearings at higher temperatures and loads. The surface of compound calcium-based grease is easy to absorb water and harden, which affects its performance.
(6) Composite aluminum-based grease. It is a compound aluminum soap thickened with behenstic acid and low-molecular organic acids (such as benzoic acid) to thicken petroleum lubricants with different viscosities. The inherently good various characteristics are suitable for the lubrication of various motors, transportation, iron and steel enterprises and other various industrial machinery and equipment. Only short fiber structure, good mechanical stability and pumpability. Because of its liquidity. Suitable for centralized lubrication system. It has good water resistance and can be used for mechanical lubrication in the presence of moisture or water.
(7) Complex lithium grease. It is composed of two or more compounds of fatty acid lithium soap and low molecular acid lithium salt (such as azelaic acid, sebacic acid, salicylic acid and borate, etc.). It is made of thickened petroleum lubricating oil with different viscosities and is widely used for lubrication of roller table bearings in steel mills, automobile wheel bearings, heavy machinery, various high-friction bearings, and gears, turbines, and worms. It has high dropping point and high temperature resistance; the fiber structure of composite soap has high strength, good mechanical stability under high temperature conditions and long service life; it has good anti-water shower characteristics and is suitable for working machinery in humid environment Lubrication, such as steel rolling machinery.
(8) Complex calcium sulfonate grease, a new type of grease with high metal content, first developed by the United States SOLTEX company, has strong corrosion resistance, extreme pressure wear resistance and long service life, complex calcium sulfonate grease It can achieve the effect of lithium-based grease without adding additives, and is one of the best lubricating grease varieties with promising future.
2) Inorganic grease
There are two types of bentonite grease and silicone grease. Surface modified silicone thickened methyl silicone oil grease can be used for electrical insulation and vacuum sealing. Bentonite grease is made of organic or bentonite thickened petroleum or synthetic lubricating oil with different viscosity after being treated with surfactant (such as dimethyl octadecyl benzyl ammonium chloride or amino amide such as bentone 434). It has the following characteristics for the lubrication of automobile chassis, wheel bearings and high-temperature bearings.
Bentonite grease has no dropping point, its temperature resistance depends on the high-temperature performance of the surfactant and base oil, and its low-temperature performance depends on the type of base oil selected. The amount of thickener also has an effect on the low temperature performance of the grease.
It has good colloidal stability. The mechanical stability of the grease varies with the type of active agent.
Corrosion resistance to metal surfaces is slightly worse. Therefore, anti-rust agents should be added to the grease to improve this performance.
3) Organic grease
Various organic compounds thickened petroleum lubricating oil or synthetic lubricating oil, each with different characteristics, these greases are mostly used for special purposes. Such as Yin Dan Shi Lin, phthalocyanine thickened synthetic lubricating oil made of high temperature grease can be used in 200 ~ 250 ℃ working conditions; fluorine-containing thickening punishment such as polytetrafluoroethylene thickened fluorocarbon compound or perfluoroether Lubricating grease, which can withstand strong oxidative punishment, as a lubrication of special components. Another example is polyurea grease that can be used for bearing lubrication under anti-radiation conditions.
Polyurea grease is made of thickened petroleum lubricating oil or synthetic lubricating oil with polyurea thickener. It has good high temperature resistance, and the viscosity of the fat does not change much within a wide temperature range of 25 ～ 225 ℃. It does not contain metal ions, which eliminates the catalytic effect of metals on the oil at high temperature, so the oxidation stability is good; the urea base grease is at 149 ℃,
Under the condition of 10.000r / min, the operating life of the bearing exceeds 4000 hours. Polyurea grease has developed rapidly in the past ten years-a wide range of products, used for the lubrication of high-wash parts in the steel industry, for the lubrication of the food industry and power, electronics industry, and long-life sealed bearings.
Selection of construction machinery grease
In the environment of strong chemical medium, synthetic oil grease with chemical resistance such as fluorocarbon grease should be selected.
(5) The selected grease should be compatible with the grease supply method of the friction pair
For centralized grease supply, select 00 to 1 grease; for parts that are regularly filled with grease guns, grease cups, etc., select 1 to 3 grease; for parts that are not used for long-term use without grease replacement, Use No. 2 or No. 3 grease.
(6) The selected grease should be compatible with the working state of the friction pair
For example, when the vibration is large, use a grease with high viscosity, good adhesion and shock absorption, such as a high-viscosity cycloalkyl or mixed soap-based compound soap-based grease.
(7) The selected grease should be suitable for its purpose of use
The grease used for lubrication must be selected according to the type, working condition, working state, environmental conditions and grease supply method of the friction pair; for the grease used for protection, the metal should be effectively protected from corrosion, such as protection For the parts in contact with sea water, aluminum-based grease with strong adhesion and high water resistance should be selected; for general protection, grease made of solid hydrocarbon thickened high-viscosity base oil can be used. For sealing grease, attention should be paid to its resistance to the solvent of the sealed medium.
(8) The selected lubricating grease should try to ensure the variety of reduced grease and improve economic efficiency.
In the case of meeting the requirements, try to use lithium grease, complex soap grease, polyurea grease and other multi-purpose universal grease. In this way, the variety of grease is reduced, the management of grease is simplified, and the cost of grease consumption and maintenance costs can be reduced due to the long service life of multi-effect grease.
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