 |
|
Social and
Environmental Report |
|
|
News Release |
|
|
|
News Release
October 22,2001
NSK Ltd.
Public Relations Department
| |
Development of Long Life Bearings for Continuous Caster Guide Rolls |
| NSK has succeeded in developing a longer life bearing for continuous caster guide rolls. This new bearing, called the Super Wear-Resistant (SWR™) Bearing, has more than twice the bearing life compared to a conventional one. |
 |
Background:
Continuous casting machines pour steel directly from the furnace into a slab, billet, or bloom directly from its molten form. There are anywhere from 500 to 1,000 bearings being used in each machine. These bearings operate under the most sever conditions consisting of a heavy load, ultra-low speed rolling (only a few rotations per minute), and an environment of water and dust contamination. There are several types of bearings that are used in such facilities, with spherical roller bearings being the most commonly used type. Because of these severe conditions, uneven wear occurs on the outer ring raceway of the bearing due to differential slip, which is phenomenon peculiar to this bearing type that results in the development of cracks and flaking. In some cases, the production line comes to a complete stop as a result of bearing failure due to an outer ring fracture caused by flaking damage. Because of this, no steel mill can afford to extend maintenance cycles for inspections, and spend valuable time and money to replace or repair bearings.
In recent years, there has been a higher demand for the development of long life bearings for casters. Maintenance of a continuous casting machine can cost as much as a few hundred million yen, ofwhich 30% is bearing related. Clearly, long life bearings can have a significant impact on the bottom line.
Features:
- NSK is first in the world to successfully generate a fine vanadium carbonitride precipitation in steel. This was achieved through alloying and carbonitriding technology, which we have been researching for many years. Vanadium carbonitride enjoys extremely refined and hard properties. Thus NSK has achieved excellent wear resistance, long flaking life, and longer bearing life by combining both of NSK's original long-life technology (TF technology) and carbonitriding technology.
- NSK has improved core toughness dramatically. Our newly developed casehardening-type material helps prevent outer ring fractures, which could result in an accident, compared with conventionally through hardened steel.
- NSK applied this newly developed steel only to the outer ring, which has been the main source of bearing damage resulting from wear. We intentionally avoided application of this material to the inner ring and roller. The use of different materials for the two parts that come into contact with each other is a key strategy in the effectiveness of SWR™ Bearings.
Results:
We obtained good results with in-house bench testing. We then undertook evaluation using actual machines in continuous casting lines with the cooperation of several steelworks. Results showed that the testbearings had improved bearing life by more than 2 or 3 times over conventional bearings. We are confident that our SWRTM Bearing can contribute to the extension of maintenance cycles and promote greater efficiency of production through the excellent characteristics of flaking resistance and ultimate fracture resistance.
There are over five thousand continuous casting lines located throughout the world. The total bearing demand is estimated at around eight billion yen a year. Thanks to the excellent characteristics NSK's SWRTM Bearing, we anticipate sales worth four billion yen after five years compared to the current amount of one billion yen.
|
|
