NTN's New Automotive “FA Tapered Roller Bearings” Allow Bearing Sectional Areas 60% of Conventional Bearings

NTN Corporation has developed the world's first specialized heat treatment (FA treatment*) to produce ultra-fine austenite grains less than half the size found in conventional bearing steels, utilizing the inherent increase in the fatigue strength of steel as the grains become smaller. Using this proprietary FA treatment, NTN has developed the “FA tapered roller bearings” which allow bearing sectional areas only 60% that of conventional bearings. Such a reduction in package size can be especially useful in today's compact cars.

As automobile transmissions become more compact, the demand for smaller transmission bearings is growing. But the limited fatigue strength of conventional carburized steel has restricted the ability to meet market demands for more compact tapered roller bearings.

NTN's “FA tapered roller bearings” apply the FA treatment to bearing steel while simultaneously increasing precision and optimizing the bearing inner race specifications to improve the anti-seizing capacity of the flange section, which has typically been the major problem for downsized bearings. With this new technology, the newer, lighter bearing sectional area and weight can both be reduced to 60% the level for conventional bearings under the same conditions.

NTN plans to develop the “FA tapered roller bearings” into a series of high-performance tapered roller bearings.

Features

For equivalent service life, ability to withstand shock, and anti-seizing capacity of conventional bearings, the new bearing sectional area and weight can both be reduced to 60% of current levels, resulting in lighter, more compact bearings.

Applications

Automobile transmissions, gear boxes, wheel bearings, transfer cases, etc.

Conventional bearing	FA tapered roller bearing

NTN's FA Treatment (Fine Austenite Strengthening Treatment)

• NTN has developed the world's first specialized heat treatment (FA treatment) that can produce ultra-fine austenite grains less than half the conventional size (average grain diameter under 5 µm) in bearing steel, making use of steel's inherent increase in fatigue strength as grain size becomes smaller.
• This FA treatment technology applies secondary induction hardening at low temperatures to the bearing's carbo-nitrided structure, increasing the service life of these new bearings to four times that of conventional bearings.
• The rolling fatigue service life of bearings made with FA treated material is greatly improved over standard bearings using conventional bearing steel, even under harsh conditions with contaminated lubricants.
• The FA treatment also improves the fracture strength of bearings by 20% and reduces physical changes in bearing dimensions to only 60% of the value for conventional bearings, providing improved gap adjustment, fit, etc.
• Previously, requirements for longer service life in bearing applications were met by developing materials with more additive elements. However, this approach has proven costly and resulted in difficulties in processing and global procurement for so many different specifications. The main advantage of FA treatment is that it solves all these problems, thus making it possible to deploy globally these high-performance bearings with longer service life using bearing steels that are readily available around the world.

The prior austenite grain boundaries
Conventional bearing	FA tapered bearing