What Materials Are Generally Used For Pump Bearings?
Metallic material
Metal materials Commonly used plain bearing metal materials are bearing alloy (also known as Babbitt or white alloy), wear-resistant cast iron, copper base and aluminum base alloys.
1, bearing alloy
Bearing alloy (also known as babbitt or white alloy) the main alloy composition is tin, lead, antimony, copper. Antimony, copper, used to improve the strength and hardness of the alloy. According to the standard, babbitt alloy can be divided into tin base alloy and lead base alloy two kinds. The strength and hardness of lead-based alloys are lower than that of tin-based alloys, and the corrosion resistance is also poor. Therefore, when using babbitt alloy, tin-based alloy is usually selected, and its commonly used grades are ZSnSb11Cu6, ZSnSb8Cu4 and so on. Although the performance of lead-based alloy is not good, but because it is more economical, it is still selected to use under the required working conditions, and its commonly used grades are ZPbSb16Sn16Cu2 and so on. However, the melting point of the bearing alloy elements is mostly low, so it is suitable for working conditions below 150 ° C.
2, copper base alloy
Copper-based alloys have higher thermal conductivity and better wear resistance than steel. And the copper base alloy has good workability and lubricity, its inner wall can be finished and contact with the smooth surface of the shaft. Copper base alloys used as sliding bearing materials are mainly: brass with copper and antimony as the main components; Bronze with copper and tin as the main components; And copper-lead alloy (also known as lead bronze). Copper base alloy has high strength, good thermal conductivity and wear resistance, and allows higher operating temperature than babbitt alloy, but the compliance, embeddedness and frictional compatibility are not as good as Babbitt alloy. Commonly used tin bronze containing tin and phosphorus, suitable for bearings with medium speed and heavy load or under impact load; Tin bronze containing tin, zinc, lead, suitable for medium speed and medium load bearing.
Non-metallic material
1. Polytetrafluoroethylene
It has good self-lubricating properties and high thermal stability. Its friction factor is small, non-absorbent, non-sticky, non-combustible, can be used under the conditions of -180~250℃. But there are also shortcomings such as large linear expansion coefficient, poor dimensional stability and poor thermal conductivity. In order to improve its performance, it can be filled with metal particles, fibers, graphite and inorganic substances.
2. Graphite
It is a good self-lubricating material, and because of its easy processing, and the more smooth the grinding, it is the material of choice for bearings. However, its mechanical properties are poor, impact resistance and load bearing capacity is poor, and it is only suitable for light load occasions. In order to improve its mechanical properties, some fusible metals with good wear resistance are commonly impregnated. The commonly used impregnating materials are babbitt alloy, copper alloy and antimony alloy. The allowable operating temperature of impregnated babbitt alloy graphite bearing is 120~180℃, the allowable operating temperature of impregnated copper alloy graphite bearing is 300℃, and the allowable operating temperature of impregnated antimony alloy graphite bearing is up to 500℃.
3. Rubber
It is an elastomer polymer with good elasticity and vibration absorption. However, its thermal conductivity is poor, processing is difficult, the allowable use temperature is below 65 ° C, and the circulating water is constantly lubricated and cooled, so it is rarely used.
4. Cemented carbide
It has high hardness, wear resistance, good strength and toughness, heat resistance, corrosion resistance and other series of benign properties, therefore, the sliding bearing processed with it has high precision, smooth operation, high hardness, good strength, durable, but expensive.
5. Silicon carbide
It is a new type of synthetic inorganic non-metallic material. The hardness is lower than diamond, with good chemical corrosion resistance, wear resistance, high temperature resistance and high mechanical strength, good self-lubrication performance, high temperature creep resistance, small friction factor, high thermal conductivity, low coefficient of thermal expansion, can be widely used in petroleum, metallurgy, chemical industry, machinery, aerospace and nuclear energy and other fields, commonly used as friction pair materials for sliding bearings and mechanical seals. A large number of experiments have shown that silicon carbide is an excellent material in friction pairs at present, especially in non-pressure sintered SiC and hot press sintered SiC.
