There are three main types of plain bearings: polymers, carbon graphite and special ceramics.
polymer
Polymers are also known as plastics, and plastics are called engineering plastics as mechanical engineering materials. It is mainly composed of synthetic resin and contains various plasticizers, stabilizers, antioxidants, antistatic agents, flame retardants, curing agents, reinforcing materials and organic polymer materials. There are many kinds of polymers, which are divided into thermoplastic and thermosetting.
The thermoplastic polymer mainly includes polyamide, polyacetal, polyethylene, polytetrafluoroethylene, polypropylene, polyurethane, etc., which are organic polymer compounds having a linear or branched structure, which can be repeatedly heated, softened and hardened. Thermoplastics can be formed by injection molding, extrusion, blow molding and rolling.
The thermosetting polymer mainly includes a phenol resin, an epoxy resin, and the like. A catalyst or curing agent is added to cure it. Once it is cured, it becomes a solid substance that does not melt. The thermosetting polymer may be composed of pressure, layer, casting, and the like.
Used in the manufacture of bearings, guides, piston rings and other frictional components, such as pump bearings, roll bearings, tail bearings, etc., especially in the manufacture of non-lubricated bearings from plastic. Ptfe plates are stamped into lip seals, bearings, piston rings and washers, and are successfully used in belt conveyors, typewriters, sewing machines, turntables, pumps, textile machinery and agricultural machinery.
The polymer has the characteristics of light, insulation, anti-friction, abrasion resistance, self-lubrication, corrosion resistance, simple molding process and high production efficiency. Compared with metallic materials, their tribological properties are sensitive to ambient temperature and humidity, and are related to viscoelastic properties. At the end of mechanical strength, the elastic modulus is small and the adsorption performance to lubricating oil is poor.
Carbon graphite material
Graphite is a type of non-metallic material composed of carbon. It is one of the three isomers of carbon. It belongs to the hexagonal crystal system and consists of a hexagonal hexagonal ring parallel to the plane and has an ordered overlapping crystal structure. Graphite is classified into natural graphite and artificial graphite. Artificial graphite is graphitized by a carbonaceous material at a temperature above 2500 °C.
Carbon graphite has the advantages of electrical conductivity, heat resistance, wear resistance, self-lubricity, high temperature stability, high temperature resistance, high thermal conductivity and low linear expansion coefficient. The chrome-plated surface has a low coefficient of friction and wear at atmospheric and room temperature. But when the humidity is very low, it will lose lubrication. A wear resistant coating can improve the wear resistance of carbon graphite.
Graphite can be added not only as a solid lubricant, resin, metal, ceramics and other materials to increase the friction of the material, but also directly to the friction material, such as paper, wood processing, textile, food and other places to avoid oily bearings, high temperature Sliding bearings, seals, piston rings, blades, etc. The "class" of mechanical engineering uses carbon graphite material M, which has four series: carbon graphite, artificial graphite material, resin-carbon composite material and metal graphite material.
Ceramic material
Ceramic is a natural inorganic non-metallic mineral or synthetic compound, which is produced by pulverization, forming and high-temperature sintering, as well as a large number of inorganic non-metallic small crystals and glass phases. Traditional ceramics are made from inorganic non-metallic natural minerals such as clay, feldspar and quartz. Special ceramics are made from synthetic raw materials. Generally used mechanical engineering: alumina, magnesia, zirconia ceramics, lead oxide, titanium oxide, silicon carbide, silicon carbide, silicon carbide, boron nitride, boron nitride, boron boride and other synthetic materials. The properties of ceramics are mainly determined by their microstructure, including grain size and distribution, composition and content of the glass phase, properties, content and distribution of impurities. The microstructure is determined by the raw materials, ingredients and manufacturing process. The common characteristics of ceramics are high hardness and compressive strength, high temperature resistance, wear resistance, oxidation resistance, corrosion resistance, brittleness, impact resistance and no ductility.
Ceramic is a relatively new bearing material for non-lubricated bearings, especially SiC and Si3N4, which have good strength, heat resistance and corrosion resistance, and good tribological properties.
