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[Up Knowledge] Characteristics and Application of Common Bearing Materials

2020-04-28 14:23

Bearing alloys, bronze, aluminum-based alloys, zinc-based alloys, etc. are all used as metal materials. Among them, the bearing alloy, also known as white alloy, is mainly lead, tin, antimony or other metal alloy, it can be in heavy load, high speed, etc., the strength is small. The reason is because of its characteristics, good wear resistance, high plasticity, good running performance, good thermal conductivity, good glue resistance and good adsorption with oil. However, because it is more expensive, it must be poured on the bearing bush of bronze, steel strip or cast iron to form a thinner coating.

(1) bearing alloy (known as babb alloy or white alloy)

The bearing alloy is an alloy of tin, lead, antimony and copper. It uses tin or lead as a matrix and contains hard grains of antimony tin (Sb-Sn) and copper tin (Cu-Sn). Hard grains play an anti-wear role, while the soft matrix increases the plasticity of the material. The elastic modulus and elastic limit of the bearing alloy are very low. Among all bearing materials, it has the best embedding and friction compliance, is easy to run in with the journal, and is not easy to bite and stick with the journal. However, the strength of the bearing alloy is very low, and the bearing bush cannot be made separately. It can only be attached to the bronze, steel or cast iron bearing bush for bearing lining. Bearing alloy is suitable for heavy load, medium and high speed occasions, the price is more expensive.

(2) Copper alloy

The copper alloy has higher strength, better friction reduction and wear resistance. Bronze performs better than brass and is the most commonly used material. Bronze has tin bronze, lead bronze and aluminum bronze, etc., of which tin bronze has the best friction reduction and is widely used. However, tin bronze has higher hardness than bearing alloy, poor running-in and embedding, and is suitable for heavy load and medium speed occasions. Lead bronze has strong anti-adhesion ability and is suitable for high-speed and heavy-duty bearings. Aluminum bronze has high strength and hardness, poor anti-adhesion ability, and is suitable for low-speed and heavy-duty bearings.

(3) Aluminum base alloy

Aluminum-based bearing alloys have good corrosion resistance and high fatigue strength, and good friction properties. These qualities enable aluminum-based alloys to replace more expensive bearing alloys and bronzes in some areas. Aluminum-based alloy can be made into single metal parts (such as bushings, bearings, etc.), can also be made into bimetal parts, bimetal bearing with aluminum-based alloy for the bearing lining, with steel as the backing. Kan

(4) Gray cast iron and wear-resistant cast iron

Ordinary gray iron or wear-resistant gray cast iron with nickel, chromium, titanium and other alloy components, or ductile iron, can be used as bearing materials. After the flake or spherical graphite in this kind of material is covered on the surface of the material, it can form a layer of graphite layer with lubrication effect, so it has certain friction reduction and wear resistance. In addition, graphite can adsorb hydrocarbons, which helps to improve the boundary lubrication performance, so when gray cast iron is used as bearing material, lubricating oil should be added. Due to the brittleness of cast iron and poor running-in, it is only suitable for light load, low speed and no impact load.


Non-metallic materials


 

The most widely used non-metallic materials are various plastics (polymer materials), such as phenolic resin, nylon, polytetrafluoroethylene, etc. The characteristics of the polymer are: it does not react with many chemical substances, and its corrosion resistance is particularly strong; it has a certain self-lubricating property, can work under non-lubricating conditions, and has a certain lubricating ability under high temperature conditions; it has good embeddability; It is better to reduce friction and wear resistance.

SelectPolymerWhen making a bearing material, we must pay attention to the following problems: Since the thermal conductivity of the polymer is only a few percent of that of steel, the dissipation of frictional heat must be considered, which strictly limits the working speed and pressure value of the polymer bearing. Because the linear expansion coefficient of polymer is much larger than that of steel, the clearance between polymer bearing and steel journal should be larger than that of metal bearing. In addition, the strength and yield limit of the polymer material is low, so the load can be limited during assembly and operation. And because the polymer material will creep at room temperature, it is not suitable for making bearings with strict clearance requirements.

carbon-graphiteIt can be used as a bearing material in a bad environment, in which the more graphite content, the softer the material and the smaller the friction coefficient. The carbon-graphite material may be added with a metal, polytetrafluoroethylene or molybdenum disulfide component, or may be impregnated with a liquid lubricant. Carbon-graphite bearings are self-lubricating, and their self-lubricating and friction-reducing properties depend on the amount of water vapor adsorbed. Carbon-graphite has an affinity for lubricants containing hydrocarbons, and the addition of lubricants helps to improve their boundary lubrication properties. In addition, it can also be used as a water-lubricated bearing material.

RubberMainly used for water as a lubricant and the environment is dirty.

WoodWith a porous structure, fillers can be used to improve its performance. Filling polymers can improve the dimensional stability of wood and reduce the amount of moisture absorption, and improve the strength. Bearings made of wood can work in very dusty conditions.


porous metalMaterial


 

This is a bearing material made by pressing and sintering different metal powders. The material is porous in structure, with pores accounting for about 10% to 35% by volume. Before use, the bearing bush is immersed in hot oil for several hours to fill the pores with lubricating oil. Therefore, bearings made of this material are usually called oily bearings.

It is self-lubricating. When working, due to the suction effect of the journal rotation and the expansion of the oil when the bearing heats up, the oil enters the friction surface for lubrication; when not working, the oil is sucked back into the bearing due to capillary action. For a long time, it can still work well even without lubricating oil. If oil is supplied regularly, the use effect is better. However, due to its small toughness, it is suitable for smooth no impact load and low speed. Porous iron and porous bronze are commonly used. Porous iron is often used to make mill bushings, machine tool oil pump bushings, internal combustion engine camshaft bushings, etc.

ManyHole bronze is commonly used to make the bearings of record players, electric fans, textile machinery and automobile generators.Our country has specialized in manufacturing oil bearing factory, need according to the design manual selection.

Powder metallurgy material is a porous metal is a powder material, it has a porous structure, if it is immersed in lubricating oil, so that the micropores are filled with lubricating oil, into an oil bearing, with self-lubricating properties. The toughness of porous metal materials is small, only suitable for smooth no impact load and medium and small speed.

From: bearing industry magazine, if there is infringement please contact delete.