Basic knowledge of ceramic bearings

Basic knowledge of ceramic bearings

As an important mechanical basic part, ceramic bearings are in the world of new materials. Because of their excellent performance, high temperature resistance. Super strength, which are unmatch by metal bearings. In the past ten years, it has been widely use in various fields of national. Economy and people’s livelihood.

First, the main characteristics of ceramic bearings

Ceramic ball bearings are develope for adjustment, heavy load, low temperature and non-lubrication. Conditions in harsh environments in the defense industry, and are a perfect combination of new materials. New processes and new structures. Converting it into civilian technology. Ceramic ball bearings can completely cover all application fields of current precision. medium-speed and above all-steel bearings.
The inner diameter and outer diameter of ceramic bearings are the standard sizes of P4, P5 and P6 grades of steel bearings formulate by the state. Due to the characteristics of low thermal expansion coefficient. Low heat transfer performance and small elasticity measurement of ceramic materials. Attention should be pay to installation and coordination.
In harsh working environments such as high speed, high temperature, low temperature, large temperature difference, vacuum, insulation, and non-magnetic conductivity, high-performance ceramic bearings are ideal bearings to replace all-steel bearings currently use. Small, stable performance, long life, corrosion resistance, not afra of pollution, wear resistance, resistance to instantaneous oil shortage lubrication ability and high reliability and excellent performance indicators, ceramic bearings can be use in machinery, chemical industry, television, vacuum, low temperature engineering, aerospace, Aviation and other fields have broad prospects for development.

This project is develop for high-speed, heavy-load, low-temperature, non-lubricate working conditions in harsh environments in the defense industry. It has high technical content and is a perfect combination of new materials, new processes and new structures.

Its working temperature is -200 ℃ to +800 ℃, the load is as high as 3000Mpa, and the dn value is close to 1.8 million mm. Within r/min, it can be convert into civilian technology, which can be widely use in civilian high-speed machine tools, low-temperature engineering, high-temperature engineering, chemical industry and other industries.
In all application fields, the performance-price ratio is much better than that of all-steel bearings, and the service life can be increase by more than 3 times compared with the bearings currently used, which saves a lot of downtime and maintenance time, reduces the scrap rate, and reduces the inventory of bearing spare parts. In addition, due to the high technical content , it is impossible to counterfeit, and the risk of investment recovery is small.

Second, the advantages of ceramic bearings

First, because ceramics are almost not afraid of corrosion, ceramic rolling bearings are suitable for operation in harsh conditions full of corrosive media.
Second, because the density of the ceramic rolling ball is lower than that of steel and the weight is much lighter, the centrifugal effect of the outer ring during rotation can be reduce by 40%, thereby greatly extending the service life.
Third, ceramics are less affected by thermal expansion and contraction than steel, so when the bearing clearance is constant, the bearing can be allow to work in an environment where the temperature difference changes more drastically.
Fourth, because the elastic modulus of ceramics is higher than that of steel, it is not easy to deform when subjected to force, so it is beneficial to improve the working speed and achieve higher precision.

3. Main uses of ceramic bearings

Ceramic bearings have the characteristics of high temperature resistance, cold resistance, wear resistance, corrosion resistance, anti-magnetic and electrical insulation, oil-free self-lubrication, and high speed.
It can be use in extremely harsh environments and special working conditions, and can be widely used in aviation, aerospace, marine, petroleum, chemical, automotive, electronic equipment, metallurgy, electric power, textiles, pumps, medical equipment, scientific research and defense and military fields. High-tech products for new material applications.
The rings and rolling elements of ceramic bearings are make of all-ceramic materials, including zirconium oxide (ZrO2), silicon nitride (Si3N4), and silicon carbide (Sic). The retainer is make of polytetrafluoroethylene, nylon 66, polyetherimide, zirconia, silicon nitride, stainless steel or special aviation aluminum, thereby expanding the application surface of ceramic bearings.

4. Application fields of ceramic bearings

Medical equipment, cryogenic engineering, optical instruments, high-speed machine tools, high-speed motors, printing machinery, food processing machinery.
In the fields of aerospace, navigation, nuclear industry, petroleum, chemical industry, light textile industry, machinery, metallurgy, electric power, food, locomotive, subway, high-speed machine tools and scientific research, defense and military technology, etc. Working under special working conditions such as explosive, strong corrosion, vacuum, electrical insulation, non-magnetic, dry friction, etc., the indispensable substitute role of ceramic bearings is gradually being recognize by people.
With the continuous progress of processing technology and the increasing level of craftsmanship, the cost of ceramic bearings has continued to decline. It has been applay in a small range of high, precise and cutting-edge fields from the past, and has been gradually extended to various industrial fields of the national economy. The market price of products It is also gradually approaching practicality and reaching a level acceptable to users. The wave of large-scale application of ceramic bearings has come!

5. Ceramic bearings are classifiy by use

(1) High-speed bearings
It has the advantages of cold resistance, small force elasticity, high pressure resistance, poor thermal conductivity, light weight, and small friction coefficient.
(2) High temperature bearing
The material itself has a high temperature resistance of 1200 ° C, and is self-lubricating, and the use temperature is between 100 ° C and 800 ° C without expansion caused by temperature difference. It can be use in high temperature equipment such as furnaces, plastics and steels.

(3) Corrosion-resistant bearings

The material itself has the characteristics of corrosion resistance and can be use in strong acid, strong alkali, inorganic, organic salt, seawater and other fields, such as: electroplating equipment, electronic equipment, chemical machinery, shipbuilding, medical equipment, etc.

(4) Antimagnetic bearing

Because there is no magnetism and no dust absorption, it can reduce the bearing peeling off in advance and the noise. Can be use in demagnetization equipment. Precision instruments and other fields.
(5) Electrically insulated bearings
Due to its high electrical resistance, it can avoid arc damage to the bearing and can be use in various electrical equipment requiring insulation.

(6) Vacuum bearing

Due to the unique oil-free self-lubricating properties of ceramic materials, it can overcome the problem that ordinary bearings cannot achieve lubrication in an ultra-high vacuum environment.
Note: For the above five types of bearings, the same set of bearings can be use in high temperature, high speed, acid-base, magnetic field, non-insulation, but due to different material properties (please refer to the rare earth ceramic material performance table), when customers choose products, Choose the most suitable ceramic bearing material according to your application.

6. Ceramic bearings are classifie by material

(1) Zirconia full ceramic bearing
All-ceramic bearings have the characteristics of anti-magnetic and electrical insulation, wear resistance and corrosion resistance, oil-free self-lubrication, high temperature resistance and high cold resistance, and can be use in extremely harsh environments and special working conditions.
The ferrule and rolling element are make of zirconia (ZrO2) ceramic material, and the cage is make of polytetrafluoroethylene (PTFE) as a standard configuration. Generally, glass fiber reinforced nylon 66 (RPA66-25), special engineering plastics (PEEK, PI), stainless steel (AISISUS316), brass (Cu), etc.
(2) Silicon nitride full ceramic bearing
Silicon nitride full-ceramic bearing rings and rolling elements are make of silicon nitride (Si3N4) ceramic material, and the cage is made of polytetrafluoroethylene (PTFE) as a standard configuration. Generally, RPA66-25, PEEK, PI, and phenolic clamps can also be use. Fabric bakelite pipes, etc.
Compared with ZrO2 materials, all-ceramic bearings made of SiN4 can be used for higher speed and load capacity, as well as for higher ambient temperature. At the same time, it can provide precision ceramic bearings for high-speed, high-precision and high-rigidity spindles, and the highest manufacturing accuracy is P4 to UP.

(3) Full complement ball full ceramic bearing

The full-complement ball type full-ceramic bearing has a ball-adding notch on one side. Due to the design of the cage-free structure, more ceramic balls can be load than the standard structure bearing, thereby improving its load capacity and avoiding the limitation of cage materials. , can achieve the effect of corrosion resistance and temperature resistance of ceramic cage type all-ceramic bearings.
This series of bearings is not suitable for high rotation speed, and the notched surface should be install at the end that does not bear the axial load during installation.

(4) Hybrid ceramic ball bearings

Ceramic balls, especially silicon nitride balls, have the characteristics of low density, high hardness, low friction coefficient, wear resistance, self-lubrication and good rigidity, and are especially suitable for rolling elements (inner and outer rings) of high-speed, high-precision and long-life hybrid ceramic ball bearings. for metal).
Generally, the inner and outer rings are make of bearing steel (GCr15) or stainless steel (AISI440C), and the ceramic balls can be make of ZrO2, Si3N4, or SiC materials.

7. Ceramic bearings are classifie by technical grade

(1) Deep groove ball bearings
(Technical grades: P4, P5, P6, P0) Deep groove ball bearings, the most representative rolling bearings, are widely used and can withstand radial loads and bidirectional axial loads. It is suitable for high-speed rotation and occasions requiring low noise and low vibration, or high temperature, high cold, corrosion, magnetic field, non-insulation and other fields where steel bearings cannot be use.
(2) Self-aligning ball bearings
The outer raceway of the self-aligning ball bearing is spherical and self-aligning, which can compensate for errors caused by misalignment and shaft deflection. It is use to produce the misalignment between the shaft and the casing or the shaft deflection part and the alignment part required for high temperature, low cold, corrosion, magnetic field non-insulation, etc. Note: The inclination cannot exceed 3 degrees.
(Technical grades are: P4, P5, P6, P0) Angular contact bearings are suitable for high-speed and high-precision rotation, and their accuracy is not affected by high temperature, magnetic fields, and water, and can withstand combined loads.
The standard contact angles are 15°, 30° and 40°. The larger the contact angle, the greater the axial load capacity. The smaller the contact angle, the bearing can bear radial load and unidirectional axial load. Usually installed in pairs. Please pay attention when purchasing.
(4) One-way thrust ball bearing
One-way thrust ball bearings are compose of a washer-shaped ferrule with ball rolling raceways and a cage assembled with balls. It can bear axial load, but cannot bear radial load.