Sliding bearing materials for water pumps are mainly divided into two categories: metal materials and non-metallic materials.
Metallic materials
Commonly used sliding bearing metal materials include bearing alloy (also called babbitt alloy or white alloy), wear-resistant cast iron, copper base and aluminum base alloy.
1. Bearing alloy
Bearing alloy (also called babbitt alloy or white alloy) mainly consists of tin, lead, antimony and copper. Antimony and copper are used to improve the strength and hardness of alloys. According to the standard, babbitt alloy can be divided into tin based alloy and lead based alloy. The strength and hardness of lead based alloys are lower than those of tin based alloys, and the corrosion resistance is also poor. Therefore, tin based alloys are usually used when babbitt alloys are used, and their commonly used brands are ZSnSb11Cu6, ZSnSb8Cu4, etc. Although the performance of lead based alloy is not as good as that of tin based alloy, it is relatively economical, so it is still used under the conditions that meet the requirements. Its common brands are ZPbSb16Sn16Cu2, etc. However, the melting point of bearing alloy elements is mostly low, so it is suitable for working conditions below 150 ℃.
2. Copper base alloy
Copper based alloys have higher thermal conductivity and better wear resistance than steel. The copper base alloy has good machinability and lubricity, and its inner wall can be fine machined to contact with the smooth surface of the shaft. Copper base alloys used as sliding bearing materials mainly include: brass with copper and antimony as main components; Bronze mainly composed of copper and tin; And copper lead alloy (also known as lead bronze). Copper base alloy has high strength, good thermal conductivity and wear resistance. Its allowable working temperature is higher than that of babbitt alloy, but its compliance, embeddedness and friction compatibility are not as good as that of 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 and lead is suitable for medium speed and medium load bearings.
Non metallic materials
3. Polytetrafluoroethylene
It has good self-lubricating performance and high thermal stability. Its friction coefficient is small, non absorbent, non sticky, non combustible, and can be used at - 180~250 ℃. But there are also some shortcomings, such as large coefficient of linear expansion, poor dimensional stability, and poor thermal conductivity. In order to improve its performance, metal particles, fibers, graphite and inorganic materials can be used for filling and strengthening.
4. Graphite
It is a good self-lubricating material, and because it is easy to process and the more polished it is, the more smooth it is, so it is the material of choice for bearings. But its mechanical properties, impact resistance and load bearing capacity are 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 usually impregnated. The commonly used impregnating materials are babbitt alloy, copper alloy and antimony alloy. The allowable service temperature of graphite bearing impregnated with babbitt alloy is 120~180 ℃, the allowable service temperature of graphite bearing impregnated with copper alloy is 300 ℃, and the allowable working temperature of graphite bearing impregnated with antimony alloy can reach 500 ℃.
5. Rubber
It is a polymer with elastomer, with good elasticity and vibration absorption. However, its thermal conductivity is poor, processing is difficult, the allowable use temperature is below 65 ℃, and it needs circulating water to continuously lubricate and cool, so it is rarely used.
6. Hard alloy
It has a series of good properties such as high hardness, wear resistance, good strength and toughness, heat resistance and corrosion resistance. Therefore, the sliding bearing processed with it has high precision, stable operation, high hardness, good strength and durability, but it is expensive.
7. Silicon carbide
It is a new type of synthetic inorganic non-metallic material. The hardness is inferior to diamond. It has good chemical corrosion resistance, wear resistance, high temperature resistance, high mechanical strength, good self-lubricating performance, high temperature creep resistance, small friction coefficient, high thermal conductivity, low thermal expansion coefficient, etc. It can be widely used in petroleum, metallurgy, chemical industry, machinery, aerospace, nuclear energy and other fields, and is commonly used as friction pair material for sliding bearings and mechanical seals. A lot of tests show that silicon carbide is an excellent material in friction pairs at present, especially pressureless sintered SiC and hot pressed sintered SiC.
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