Advanced Product Solutions

Super-TF
Steel Technology

Durability – even in extreme operating environments – is a critical criterion for steel mill bearings. Reliable, uninterrupted performance of rolling components that endure heavy loads and high heat amid water and scale is critical to realizing and accelerating production capacities.

NSK’s Super-TF (STF) series bearings are designed to deliver outstanding durability in contaminated operating environments. Through advanced material engineering and heat treatment technology, they perform with superior resistance to wear, seizure and heat.

Super-TF bearings provide dramatically longer service life, optimize machine performance, reduce maintenance intervals and deliver total cost-efficiency.

Proven Advantages

As much as 10 times the service life of conventional carburized bearings in contaminated lubrication conditions
More than 5 times the service life of conventional carburized bearings in boundary lubrication conditions
Approximately 4 times the service life of conventional bearing steel at temperatures as high as 160°C
Less than 1/3 the rate of wear compared to conventional bearing steel
As much as 40% improvement in seizure resistance compared to conventional bearing steel
Optimized bearing cost-efficiency, reduced maintenance intervals and increased total productivity

Identification of Failure Mechanisms

Stage 1: Surface Denting

Raceway surface dents occur due to foreign debris contamination          

Stage 2: Crack Formation

Stress concentration around the debris causes dents to develop into cracks

Stage 3: Flaking Development

Cracks propagate under the load of each passing roller and develop into flaking

Development of Super-TF Bearings

Operating Conditions

    Harsh operating conditions: heavy loads, low speeds
   
Foreign debris contamination: fine iron powder   Poor oil film formation: boundary-lubrication
 
Bearing damage: surface originated flaking

Pictured: outer ring raceway surface flaking

Countermeasures

Material composition Containing appropriate levels of chromium and molybdenum for increased hardness
Special heat treatment Optimized dispersion of finer carbide and carbonitride particles
Retained austenite Alleviation of the stress concentration on the contact surface

Super-TF Bearings

Super-TF Performance

Life test result under foreign contamination
(tapered roller bearings)

  Catalog Life
1
  General Carburized Steel
 
  0.2
  Super-TF
2

Life test result under boundary-lubrication (∆=0.3)
(ball-rod rolling contact fatigue test)

  General Carburized Steel
1
  Super-TF
5.5