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Material of bearing
The ferrule and rolling element of bearings repeatedly withstands the high contact pressure and simultaneously carries on the rolling surface which follows sliding.
The keeper contacts with two sides of ferrule and rolling element or has sliding contact with either of them. Meanwhile, it bears pulling force and compressive force. Therefore, the main requirements on material and performance of ferrule, rolling element and separator are as follows:
Performances of materials of ferrule and rolling element should have big rolling fatigue strength, high hardness and high rubbing fastness. Performances of materials of separator should good dimensional stability and big mechanical strength.
Moreover, bearing requires good processability. It also requires good abrasion-resistance, heat resistance and corrosion resistance to be in accordance with different applications.
Materials of ferrule and rolling element
Ferrule and rolling element are often made from high-carbon chromium uranium steel.
Most of the bearing is made from SUJ2 belonging to JIS steel grade. Huge bearing is made from SUJ3.
The chemical constitution of SUJ2, as bearing's material, have been standardized in various countries. For example, AISL52100（American）、DIN100Cr6（West Germany）and BS535A99（England） belong to the same steel.For further abrasion-resistance, chromium steel, chromium molybdenum steel and nickel chromium molybdenum steel are used as bearing material. By carburization, steel gets a case depth from surface to appropriate depth.
Carburization bearings has better abrasion-resistance than bearing using bearing steel as they have appropriate case depth, fine and closely tissue, appropriate surface hardness and centre hardness. Common carburization bearing has steel’s chemical composition. As NSK use vacuum outgas process, the material has high clearness, little oxygen and good quality.
Furthermore, by using appropriate heat treatment, the bearings’rolling fatigue life gets markedly improved. According to special application, we also use maxite with good heat resistance and stainless steel with good corrosion resistance besides the steel variety above.
Materials of separator
Stamped separator is made from low-carbon steel. According to different application, it is also made from brass sheet and corrosion resistant plate. Chasing separator is made from high-strength brass, carbon steel, as well as synthetic resin.
Choose bearings
Outline of choosing bearings
As the market requirements on various mechanical device and apparatus using rolling bearing is becoming stricter, the requirements and performance of bearing also become more diversified. In order to choose right bearing from so many structures and dimensions, choosing appropriate bearing should consider from many aspects.
Choosing bearing often consider the following properties: bearing arrangement which is as set of axes, installation, dismantlement difficulty, allowable space, dimensions and marketability of bearing. According to these properties, you can generally decide the structure of bearing. That's the first step. Next, compare design life of machine using bearing and different endurance strength. Simultaneously, decide the dimensions of bearing. Choosing bearing prefer to consider fatigue life of bearing. Life of grease, wearing and tearing and noise resulting from grease ageing effect also need fully research. In addition, according to different application, it is necessary to choose precision, lash, structure of separator, grease and many other requirements as special designed bearing.But, there are no necessary sequence and rule to choose bearing. And the requirements and performance of bearing should be considered first. The most important item is especially practical.
○requirements and performance of bearing
○using condition and environment condition
○dimensions tissue during installation
○allowable space of bearing
○load amount and direction
○vibration, impact
○speed of rotation, limit speed of bearing
○slope of internal and external ring
○axial direction fixing and bearing fit
○installation and dismantlement difficulty
○noise, torsion
○inflexibility
○Marketability and economy
Decide structure and array of bearing
○setting up a machine and design life
○equivalent dynamic or static load
○speed of rotation
○allowable static loading
○axial load decides (cylinder roller bearing)
Dimensions of bearing
○precision of rotary jars
○high-speed rotation
○torsion fluctuation
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