Bearing Performance and Materials
Because the rings and rolling elements of a rolling bearing repeatedly endure high contact pressure and rolling contact, while the bearing cage endures tensile or compressive forces and sliding contact, certain requirements are placed on the material properties of each part of the bearing.
The bearing rings and rolling elements require high rolling fatigue strength, high hardness, and good friction resistance. The bearing cage material requires high mechanical strength and good stability. In addition, bearing materials must have good machinability, and for bearings used in special environments or applications, good high-temperature resistance, impact resistance, and corrosion resistance are also required.
High-carbon chromium bearing steel is typically used for bearing rings and rolling elements. Most bearings use SUJ2 steel from the JIS standard, while large bearings use SUJ3.
Besides the above steel grades, high-speed steel with excellent heat resistance and stainless steel with good corrosion resistance may also be used depending on the application.
Low-carbon steel is generally used for stamped bearing cages. However, depending on the application, brass or stainless steel may also be used. The materials used for manufacturing the bearing cage include high-strength brass, carbon steel, and synthetic resins.
Bearing Lubrication
Bearing lubrication methods are divided into grease lubrication and oil lubrication. To ensure the bearing performs optimally, a lubrication method suitable for the operating conditions and purpose must be selected. From a lubrication performance perspective, lubricating oil is superior to lubricating grease. Grease, relatively speaking, simplifies the structure surrounding the bearing. The choice between lubricating oil and grease should be based on the actual situation.
(1) Reduce friction and wear. Prevent metal-to-metal contact at the contact points of the bearing’s rings, rolling elements, and cage to reduce friction and wear.
(2) Extend fatigue life. The rolling fatigue life of a bearing is extended during rotation if the rolling contact surfaces are well lubricated. Conversely, low oil viscosity and poor lubricating oil film thickness shorten the life.
(3) Dissipate frictional heat and cool. Circulating oil supply methods can use oil to dissipate heat generated by friction or heat transferred from the outside, thus cooling the bearing. This prevents overheating and aging of the lubricating oil itself.
(4) It prevents foreign objects from entering the bearing or prevents rust and corrosion.
