NOT ALL STEEL IS CREATED EQUAL

When it comes to getting the most out of your bearings, steel composition should be the number one concern. Research proves that ultra-clean steel combined with the appropriate heat treatment significantly increases the rolling fatigue life of bearings, which saves you money and time. There are four key characteristics that should be considered when assessing the steel used for bearings and components:

PURITY
During the steel making process, a number of materials can enter and combine with the steel. Contaminants such as silicone, aluminum, and sulphur combine with oxygen and form inclusions. Each type of inclusion affects bearing fatigue differently, but generally results in reduced fatigue life. Vacuum-melt or vacuum-degassing processes can control the amount of non-metallic inclusion in bearing steel and thereby improve quality and fatigue strength

HARDENABILITY
High-quality bearings are heat treated to improve the hardness of the steel and give them greater life. In addition, alloys are added to the steel/carbon mix to ensure that the hardness will be uniform throughout the component. These alloys include chrome, molybdenum, and nickel.

ROLLING CONTACT FATIGUE STRENGTH
Non-metallic inclusions present stress points where micro-cracks can develop. The repeated contact stress of the balls rolling over an inclusion causes additional stress in the steel surrounding the inclusion. The micro-cracks enlarge, weakening the material. Eventually these cracks break out at the surface of the raceway, a process known as spalling, allowing a small piece to crack out.

WEAR RESISTANCE
Although there is no way to stop the process totally, heat treating increases steel's resistance to wear. For bearings, this wear resistance helps to prolong life under adverse conditions. Uniform heat treating ensures good hardness and excellent wear resistance.

NSK researchers are constantly working on improvements that will further extend bearing life in the future. NSK ultra-clean steel is a highly pure vacuum-degassed, high carbon chromium steel containing a minimum of non-metallic inclusions. For more information, contact NSK by calling 1-877-994-6675, email us at info@ca.nsk.com or visit our website www.ca.nsk.com.