With the rapid development of industrial technology, the requirements for bearings are also getting higher and higher, which are embodied in: structural requirements for miniaturization, size
The demand for precision, speed requires high speed, temperature requires high temperature, high vacuum, anti-corrosion and other more severe working conditions are also increasingly
increase. Some properties of bearings made of steel materials have been unsatisfactory. A large number of tests have proved that precision bearings work in high-speed environments.
(The speed is above 4 × 104r/min), the ball is the weakest part in the bearing, about 60% ~ 70% of the high speed bearing failure is due to
Steel balls are caused by varying degrees of fatigue damage. . In order to improve the performance of high-speed bearings to improve their fatigue life, the application of structural ceramics to make spheres or other bearing zeros
Piece, can significantly improve the performance and life of high-speed bearings, where silicon nitride or silicon nitride-based ceramics are the most suitable for the manufacture of bearings and their parts
Think of the material and achieved good results
1.1 High speed operation performance
For general bearings, when the DN value is above 2. 5 × 106, the centrifugal force of the rolling elements will increase sharply with the increase of the rotational speed.
Large, the sliding friction of the rolling contact surface of the bearing is increased, and the life of the bearing is shortened. Experimental results have confirmed: low density
Silicon nitride ceramics, bearing a steel shaft with a high life expectancy of 3 to 6 times, while the centrifugal force of the rolling element is greatly reduced due to rolling
The high-speed slip caused by the centrifugal force of the moving body is also greatly reduced, so that the inertial force of the rolling element and the cage assembly is remarkably reduced.
1.2 High temperature performance
Temperature changes have a large impact on the rolling fatigue life of the bearing. M50 steel bearings are usually used as heat resistant materials.
The rated life at 250 °C is about one tenth of that at normal temperature. For ceramic bearings, ceramic materials have excellent high temperature properties.
It has good rolling fatigue strength under high temperature conditions. The test results show that Si3N4 remains quite high at 1000 °C.
Bending strength, so ceramic bearings have better contact stress and longer fatigue life
Ceramic bearings can be divided into all-ceramic bearings and hybrid ceramic bearings. All ceramic bearings mean that the bearings are all made of ceramic materials.
Hybrid ceramic bearings mean that part of the bearing is made of ceramic material and the rest is made of bearing steel. Hybrid ceramic bearings can be divided
There are three types: (1) the rolling elements are ceramic materials and the rest are bearings made of bearing steel; (2) the rolling elements and the outer ring are ceramics and the rest are bearings
Steel bearings; (3) The rolling elements and inner rings are ceramic materials and the other are bearing steel bearings. The so-called hybrid ceramic bearing is meant to roll
The moving body is ceramic and the inner outer ring is the bearing of the bearing steel.
3 Application of hybrid ceramic bearings
Since the 1960s, the application of ceramic bearings has been rapid, and Norton Company has applied silicon nitride ceramics to the hydraulic pumps of the space shuttle.
Bearings, which increase their speed by 50% to 100%; SKF's ceramic bearings supplied to the US aerospace industry are already high at 800 °C
Use under warm conditions. Japan NSK, KOYO, NTK 3 major companies are competing to develop ceramic bearings, currently NSK company has made ceramic bearings
It is a standardized series of products, mainly used on the main shaft. Japan's Ishikawajima Heavy Industries uses ceramic bearings for aircraft engines. Germany
Silicon nitride bearings manufactured by KGM have been used in special media such as high temperature, water, acid and alkali, as well as chemical and printing equipment. Enter 90
In the era, ceramic bearings have been successfully applied in ultra-high-speed machining technology, and the international spindle speed of machine tools has generally reached
More than 10000r/min, and some even reached 100000r/min. This is the main form of the spindle system using the electric spindle, and its support
The use of silicon nitride ceramic bearings, and mainly the rolling bearing is a hybrid bearing of silicon nitride. This kind of bearing has become low temperature rise, high speed, high hardness,
Long-life new generation high-speed bearings, foreign ultra-high-speed grinding machines use ceramic bearings for spindle support
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