Process and control today | NSK Super-TF spherical roller bearings provide long life in contaminated environments


Unplanned bearing failures in production-critical machinery and equipment can be extremely costly in parts, labor and downtime, negatively impacting profitability. This problem is compounded in contaminated environments, such as those prevalent in steel manufacturing, which is why an increasing number of steel mills are turning to the benefits offered by Super-TF spherical roller bearings. long life from NSK. Manufactured from a specially developed proprietary material, these bearings are capable of significantly increasing service life and uptime.

NSK Super-Tough (Super-TF) bearing steel is a proprietary material that is not only ideal for very high load applications, but also has a proven ability to reduce surface-based lubricant spalling contaminated.

Bearings in the steel industry often have to operate in conditions where metal particles or debris can easily contaminate the lubrication. These contaminants create dents on the running surfaces of bearings, where the concentrated stress around these dents eventually causes cracking and spalling of the surface.

NSK research has shown that a high level of residual austenite is an extremely effective means of reducing stress concentration around surface bumps and extending service life. TF technology in general is a unique heat treatment process to optimize the level of austenite retained in bearing materials. However, austenite itself has a soft microstructure, so to meet the need for greater hardness with a higher level of retained austenite, NSK developed a technique to reduce the diameter of carbide and carbonitride particles. compared to those present in standard case hardened bearings.

The resulting Super-TF bearing steel, with its special chemical composition and special heat treatment process, offers an impressive service life. In 2017, the DNV GL test house certified that when Super-TF material is used, it is possible to improve the basic dynamic load rating of roller bearings by 23%. This increase equates to an effective doubling of life over standard steel bearings.

Among those able to support the claimed benefits is a steel manufacturer who experienced bearing failures (24040 spherical roller bearings) on his cold rolling mill every 3-4 months. NSK engineers analyzed failed bearings and grease samples as part of its AIP value-added program, finding that highly contaminated rolling mill operating conditions were to blame for unexpected bearing failures, costly unscheduled downtime and reduced production rates.

NSK’s team of experts recommended the adoption of Super-TF spherical roller bearings to combat debris contamination in the lubricant. After a four-month trial run, the mill returned the bearings to NSK’s laboratory for inspection. An X-ray fatigue analysis revealed a remaining life of 29-50 months due to the superior wear resistance of the Super-TF bearings.

For some years now, the steel mill has replaced bearings in its rolling mill only once a year during scheduled maintenance, resulting in significant savings on replacement bearings, downtime and maintenance costs. maintenance.

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