1) Soap based lubricating grease accounts for about 90% of the production of lubricating grease. The most widely used. The most commonly used lubricating greases include calcium based, sodium based, lithium based calcium sodium based, and composite calcium based. Composite aluminum based and composite lithium based lubricants also account for a certain proportion, and these two types of grease have promising development prospects.
(1) Calcium based lubricating grease. It is made from calcium soap thickened medium viscosity petroleum lubricating oil generated by the reaction of natural fats or synthetic fatty acids with calcium hydroxide. The drip point should be between 75-100 ℃, and its operating temperature should not exceed 60 ℃. If it exceeds this temperature, the lubricating grease will become soft or even structurally damaged, and lubrication cannot be guaranteed. Has good water resistance, is not easily emulsified or deteriorated when in contact with water, and is suitable for lubrication of various mechanical components in humid environments or in contact with water. It has a relatively short fiber structure, good shear stability and thixotropic stability, therefore it has good lubrication and protection properties.
(2) Sodium based grease is made from natural or synthetic fatty acid sodium soap thickened medium viscosity petroleum lubricating oil. It has a long fiber structure and good drawing properties, and can be used in rolling or sliding bearings with high vibration and temperature. Especially suitable for lubrication of low-speed and high load machinery. Due to its high drop point, it can work for a longer period of time at 80% or above this temperature. Sodium based grease can absorb water vapor, delaying its penetration into metal surfaces. Therefore, it has a certain degree of protection.
(3) Calcium sodium based lubricating grease. It has the characteristics of calcium based and sodium based lubricants. It has the water resistance of calcium based lipids and the temperature resistance of sodium based lipids, with a drop point of around 120 ℃ and a usage temperature range of 90-100 ℃. It has good mechanical safety and pumping performance, and can be used on rolling bearings under less humid conditions. The most commonly used are bearing grease and rolling mill grease, which can be used to lubricate rolling bearings in medium load motors, blowers, automotive chassis, wheel hubs, and other parts.
(4) Lithium based lubricating grease. It is made by thickening petroleum lubricating oil or synthetic lubricating oil with natural fatty acids (stearic acid or 12 hydroxystearic acid) lithium soap. Synthetic lithium based grease is made by thickening petroleum lubricating oil with synthetic fatty acid lithium soap. Due to its various excellent properties, lithium based grease is widely used for bearing lubrication in aircraft, automobiles, machine tools, and various mechanical equipment. Droppoint above 180 ℃, can be used for a long time in an environment around 120 ℃. It has good mechanical stability, chemical stability, and low-temperature performance, and can be used on high-speed mechanical bearings. It has excellent water resistance and can be used on mechanical components that are damp and in contact with water. Lithium soap has strong thickening ability. After adding extreme pressure, rust prevention and other additives to lubricating grease, it is made into a multi effect long-life lubricating grease with a wide range of applications.
(5) Composite calcium based grease. Made by thickening medium viscosity petroleum lubricating oil or synthetic lubricating oil with composite calcium soap made of fatty acid calcium soap and low molecular weight calcium salt. Good temperature resistance, with a drop point of lubricating grease above 180 ℃, and a usage temperature of around 150 ℃. Has good water resistance, mechanical stability, and colloidal stability. It has good extreme pressure and is suitable for lubricating mechanical bearings at high temperatures and high loads. The surface of composite calcium based grease is prone to water absorption and hardening, which affects its performance.
(6) Composite aluminum based grease. It is made by thickening different viscosity petroleum lubricating oils with a composite aluminum soap of stearic acid and low molecular weight organic acids (such as benzoic acid). Inherent good characteristics, suitable for lubrication of various motors, transportation, steel enterprises, and other industrial machinery and equipment. Only short fiber structure, good mechanical stability and pumpability. Because of its good liquidity. Suitable for centralized lubrication systems. Has good water resistance and can be used for mechanical lubrication in damp or water environments.
(7) Composite lithium based grease. It is co crystallized from two or more compounds of fatty acid lithium soap and low molecular weight lithium salts (such as azelaic acid, sebacic acid, salicylic acid, borate, etc.). Made from thickened petroleum lubricants of different viscosities, widely used in roller bearings in front of steel mills, automotive wheel bearings, heavy machinery, various high friction and anti-wear bearings, as well as lubrication for gears, turbines, worm gears, etc. Has high drop point and high temperature resistance; The fiber structure of composite soap has high strength, good mechanical stability under high temperature conditions, and a long service life; Has good water resistance and is suitable for lubrication of working machinery in humid environments, such as steel rolling machinery.
2) Inorganic lubricating grease
There are mainly two types of lubricating grease: bentonite lubricating grease and silicone lubricating grease. Lubricating grease made from surface modified silicone thickened methyl silicone oil can be used for electrical insulation and vacuum sealing. Bentonite lubricating grease is made by thickening petroleum lubricating oil or synthetic lubricating oil with different viscosities of organic bentonite treated with surfactants such as dimethyl octadecylbenzyl ammonium chloride or amino amide. It is suitable for lubricating automotive chassis, wheel bearings, and high-temperature bearings. It has the following characteristics. Bentonite lubricating grease has no dripping points, and its temperature resistance depends on the high temperature performance of surfactants and base oils, while its low temperature performance depends on the type of base oil selected. The amount of thickener also has an impact on the low-temperature performance of fats. It has good colloidal stability, and the mechanical stability of lubricating grease varies with the type of surfactant used. The corrosion resistance of metal surfaces is slightly poor. Therefore, rust inhibitors should be added to the lubricating grease to improve this performance.
3) Organic lubricants are various organic compounds that thicken petroleum lubricants or synthetic lubricants, each with different characteristics. Most of these lubricants are used for special purposes. High temperature lubricating grease made from thickened synthetic lubricating oils such as Yin Dan Shi Lin and phthalocyanine can be used in working conditions of 200-250 ℃; Lubricating grease made of fluorinated thickening agents such as polytetrafluoroethylene thickened fluorocarbon compounds or perfluoroethers can withstand strong oxidation and serve as a lubricant for special components. For example, polyurea grease can be used for bearing lubrication under radiation resistant conditions. Polyurea lubricating grease is made by thickening petroleum lubricating oil or synthetic lubricating oil with polyurea thickener. It has good high temperature resistance and the viscosity of the grease does not change much within a wide temperature range of 25-225 ℃. Moreover, because the thickener molecules do not contain metal ions, the catalytic effect of metals on the lubricating oil at high temperatures is eliminated, resulting in good oxidation stability; Under the conditions of 149 ℃ and 10.000R/min, the bearing operating life of urea based grease exceeds 4000 hours. Polyurea grease is a widely used product that has rapidly developed in the past decade. It is used for lubrication of high washing parts in the steel industry, as well as for lubrication of food, power, electronics industries, and long-life sealed bearings. The selection of lubricating grease for construction machinery should use synthetic oil lubricating grease that is resistant to chemical media, such as fluorocarbon lubricating grease, in a strong chemical medium environment.
(5) The selected lubricating grease should be compatible with the grease supply method of the friction pair. When it belongs to centralized grease supply, lubricating grease numbered 00 to 1 should be selected; For parts that are regularly filled with grease guns, grease cups, etc., lubricating grease of grades 1-3 should be selected; For parts that are used for a long time without changing the grease, No.2 or No.3 lubricating grease should be selected.
(6) The selected lubricating grease should be suitable for the working state of the friction pair. For example, when there is a large vibration, a grease with high viscosity, good adhesion and vibration reduction properties should be used, such as a composite soap based grease thickened with high viscosity cyclic or mixed base lubricating oil.
(7) The selected lubricating grease should be suitable for its intended use. The specific selection of lubricating grease should be based on the type, working condition, working state, environmental conditions, and grease supply method of the friction pair; For protective grease, it should be able to effectively protect metals from corrosion, such as protecting parts that come into contact with seawater. Aluminum based grease with strong adhesion and water resistance should be selected; Generally, protective grease can be made from solid hydrocarbon thickened high viscosity base oil. For sealing grease, attention should be paid to its resistance to the solvent of the sealed medium.
(8) The selected lubricating grease should minimize the variety of grease and improve economic efficiency as much as possible. When meeting the requirements, try to use multi effect universal lubricating grease such as lithium based grease, composite soap based grease, polyurea grease, etc. In this way, the variety of fats is reduced, the management of fats is simplified, and the long service life of multi effect fats can reduce the cost of using fats and repair costs.