In the bearing bush or shaft diameter, artificially added solid
lubricant to reduce friction, this bearing is called solid lubrication
bearing.
Solid
lubricated bearings and non-lubricated bearings are inherently
indistinguishable from frictional sliding self-lubricating bearings,
except that in solid-lubricated bearings, the superficial solid material
involved in friction is specifically designed to prevent the two
surfaces from sticking together, reduce the friction factor, and reduce
wear. Into the.
The
use of solid lubricants can save electricity, petroleum products and
non-ferrous metals and prevent lubricants from polluting the
environment. Solid lubricants are suitable for:
1. High temperature, high pressure working environment, such as extrusion, stamping, drawing, pressing and so on.
2. Low speed conditions, such as machine tool rails.
3. Wide temperature range.
4. Under high vacuum conditions, the graphite is inlaid with
components that lubricate the bearings, and lubrication does not destroy
the vacuum.
5. Parts that operate under strong irradiation conditions, the solid lubricant slowly deteriorates under strong irradiation.
6. In case of anti-corrosion, the solid lubricant can not react with
air, solvent, fuel, combustion-supporting copper alloy bushes, etc., and
can work under acid, alkali and other environments.
7. There is a dusty environment.
8. It is necessary to strictly avoid occasions where lubricants
contaminate the product, such as food, textile, paper, medicine,
printing and other equipment.
9. When grease is easily washed away.
10. It is very inconvenient for oil supply.
The friction factor of solid lubrication is usually higher than that
of oil and grease lubrication, and there is no cooling effect and does
not help to discharge the wear debris.
Bearing materials without lubrication
Non-lubricated bearings Bearing materials are mainly polymers, carbon graphite and special ceramics.
1, polymer
Polymers are also called plastics. Plastics used as mechanical engineering materials are called engineering plastics. It is based on synthetic resin as the main component, but also
contains a variety of plasticizers, stabilizers, antioxidants,
antistatic agents, flame retardants, curing agents, reinforcing
materials and fillers of organic polymer materials.
There are many kinds of polymers, and they are divided into thermoplastics and thermosets according to their characteristics.
Thermoplastic
polymers are commonly used are: polyamide, polyacetal, polyethylene,
polytetrafluoroethylene, polypropylene, polyurethane and so on. They
are organic polymer compounds having a linear or branched structure and
can be repeatedly heated to soften and harden by cooling. Thermoplastics can be molded by processes such as injection molding, extrusion molding, blow molding, and calendering.
Thermosetting polymers are commonly used phenolic resin, epoxy resin and so on. They
add a catalyst or curing agent to cure during processing, and once it
is cured, it becomes a solid material that will never melt. Thermosetting polymers can be molded by compression molding, lamination, casting, and the like.
Commonly
used plastic bearings, guide rails, piston rings and other frictional
parts, such as water pump bearings, rolling mill bearings, stern
bearings, etc., in particular, can be made of plastic bearings without
lubrication. Punched
PTFE sheets into lip seals, bushings, piston rings and gaskets.
Successfully applied to belt conveyors, typewriters, sewing machines,
phonograph players, water pumps, textile machinery and agricultural
machinery. .
Polymers
are characterized by light weight, insulation, friction reduction, wear
resistance, self lubrication, corrosion resistance, simple molding
process, and high production efficiency. Compared with metal materials, their tribological properties are
sensitive to environmental temperature and humidity, significant
properties related to viscoelasticity, mechanical strength at the end,
small elastic modulus, and poor lubricating oil adsorption.
2. Graphite material
Ink is a type of non-metallic material composed of carbon. It is one of the three isomers of carbon, belonging to the hexagonal
system. Each layer consists of hexagonal rings, and the layers are
parallel to the layers, showing an orderly overlapping crystal
structure.
Graphite is divided into two types, natural graphite and artificial graphite. Artificial graphite is made of carbonaceous materials that are graphitized at temperatures above 2500°C.
Carbon
graphite generally has good conductivity, heat resistance, abrasion
resistance, self-lubrication, good high temperature stability, strong
chemical corrosion resistance, thermal conductivity higher than that of
polymers, and a small linear expansion coefficient. The
friction coefficient and the wear rate with the chrome-plated surface
are low at atmospheric and room temperature conditions. However, it loses its lubricity when the humidity is low. Coating the wear-resistant coating can increase the abrasion resistance of carbon graphite.
Graphite
not only can be used as a solid lubricant, can be added to resin,
metal, ceramics and other materials, increase the friction reduction of
these materials can also be used directly as a friction material, such
as making paper, wood processing, textiles, food and other avoid oil
sites Bearings, high temperature sliding bearings, seals, piston rings, scrapers, etc.
The “class” symbol of carbon graphite material for mechanical
engineering is represented by M. There are four series: carbon graphite
material, electrochemical graphite material, resin carbon composite
material and metal graphite material.
3. Ceramic materials
Ceramics
are non-metallic materials consisting of inorganic non-metallic natural
minerals or man-made compounds as raw materials, crushed, shaped and
sintered at high temperature, composed of numerous inorganic
non-metallic small crystals and glass phases. Inorganic
non-metallic natural minerals, such as clay, feldspar, quartz, etc.,
are made from traditional ceramics; artificial compounds made from raw
materials are special ceramics. The ceramics used in mechanical engineering are generally special
ceramics made of artificial compounds such as alumina, magnesia,
zirconia, lead oxide, titanium oxide, silicon carbide, boron carbide,
silicon nitride, and boron nitride.
The
properties of ceramics are largely determined by their microstructure,
including the grain size and distribution, the composition and content
of the glass phase, the nature, content, and distribution of the
impurities. The microstructure is determined by the raw materials, composition and manufacturing process. The common characteristics of ceramics are high hardness and
compressive strength, high temperature resistance, wear resistance,
oxidation resistance, corrosion resistance, brittleness, impenetrability
and non-ductility.
Ceramics
is a relatively new non-lubricated bearing pad material, especially SiC
and Si3N4, which have good strength, heat resistance and corrosion
resistance, and have good tribological properties.
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