The standard materials for ball and
roller bearings are usually ANSI 52100 or equivalent “ball bearing
steel” or case carburized steels. Industrial demands for special
bearings to meet abnormal service requirements spur the continual
search for new and improved bearing materials.
High temperatures, corrosive
atmospheres, massive size, marginal lubrication, complex design, and
space and weight limitations are typical abnormal requirements.
Conventional bearing steels are often
inadequate when these problems are present. Sustained high operating
temperatures reduce hardness, wear resistance, yield strength, and,
therefore, bearing life. Conventional bearing steels also lack
resistance to the oxidation that takes place at elevated
temperatures.
Materials such as 440-C stainless or
corrosion-resistant coated steels may be required for severely
adverse environments. For extremely high speeds and high
temperatures, special alloy steels and materials such as metallic
carbides and ceramics are used.
The combination of bearing size,
complexity of design, and space and weight limitations can be a
governing factor in the selection of bearing material. For example, a
large-diameter, thin-section bearing with integral gear teeth and
bolt holes would require a material that could be selectively
hardened.
Monel and beryllium copper are not as
hardenable as bearing steels and are nonmagnetic and resist saltwater
corrosion. These qualities make them excellent materials for marine
applications.
Although low-carbon steels are the most
popular, a variety of other materials is also used for bearing cages.
Molded nylon, synthetic resin-impregnated fabrics, and bronze/brass
are popular in the normal temperature ranges.
High-performance polymers, carbon
steel, certain stainless steels, and iron-silicon bronze are used for
higher temperatures.
No comments:
Post a Comment