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NSK'High-performance Bearings Maximise Uptime
NSK has worked with leading global steel makers to develop a package of high-performance bearings, matching specific application requirements to provide extended uptime and reduced maintenance costs, despite operating conditions of extreme heat, water ingress, and lubricant contaminated with water and scale.
One of the key factors in the enhanced performance of NSK's bearing range is the development of new materials technology: in particular, Super-TF steel.In comparison with bearings made of ordinary carburised steel, Super-TF bearings offer up to 10 times the life with contaminated lubrication and up to twice the life where the lubricant is clean.Where the problem is related to insufficient lubrication, the life of Super TF bearings is still impressive at around 5.5 times that of ordinary carburised steel.
In addition to extending service life under conditions of boundary or contaminated lubrication, Super TF bearings also offer increased resistance to wear and seizure as a result of the dispersion of large number of fine carbides and nitrides in the bearing material.
In comparative tests with bearings made of conventional materials, such as SUJ2 steel, the Super TF material structure has shown less than one third the rate of wear and a 40 percent increase in seizure resistance.Super-TF is proving its pedigree in products such as NSK's unique Extra Capacity Sealed Clean Roll Neck Bearings, a new design that delivers up to 34 percent extra load capacity and longer life (up to 2.7 times longer) under severe lubrication conditions.The Roll Neck Bearings are designed for supporting rolls in the rolling mills of steelworks.They are required to achieve longer life while experiencing the adverse conditions of high loading, extreme shock loads, and the problem water and scale ingress, which because of its effect on lubricating conditions, probably affects bearing life the most.
Complementing Super-TF for use in continuous casting machines and rolling mills, is Water Tough WTF, a newly patented bearing material that achieves approximately three times the service life of conventional bearing materials in water contaminated operating environments such as steel mills.WTF is the result of NSK's research into roll neck bearings for use in steel mills.
The operating conditions of these bearings are particularly tough; water-infiltrated lubrication and the ingress of foreign particles, such as scale, which can cause flaking of the rolling contact surfaces of the bearings, reducing their service life and often resulting in premature failure.Water-Tough WTF addresses these problems.A new super clean bearing steel that benefits from tightly controlled levels of surface retained austenite, it ensures that bearing fatigue life is improved under debris-contaminated lubrication.
WTF, the super clean material achieves a life approximately three times longer than that of bearings made from conventional case-hardened steel.In addition to Super-TF and Water-Tough, NSK has used materials technology to develop a longer life spherical roller bearing for use in the guide rolls of continuous casting machines.
These operate under some the most severe conditions imaginable: heavy load, ultra-low speed rolling (only a few rotations per minute), and an environment of water and dust contamination.The new Super Wear-Resistant (SWR) Bearing has more than twice the life compared to conventional (SUJ2) bearing types.
In field tests the SWR bearing has proven to be superior not only in wear resistance, but also in surface originated flaking life characteristics and core toughness.The field tests were carried out on continuous casting lines in co-operation with several major steelworks.The results of these evaluations showed that SWR bearings provided 2 or 3 times more life when compared to conventional bearings.As a result, SWR Bearings are set to make a real contribution to the extension of maintenance cycles on continuous casting machines, and to promote greater efficiency of production through the superior characteristics of flaking resistance and ultimate fracture resistance.Further underlining the scale of NSK's wide ranging product developments for steel makers is the HPS series of spherical roller bearings.
These bearings are used in conveyors and in table rollers, where a new design helps them to achieve twice the running life compared to conventional bearings of the same size, and a maximum limiting running speed that has been improved by up to 20 percent.The HPS Series provides users with significant benefits by reducing maintenance costs, energy costs, and enabling downscaling of product design.Compared with other types of bearings, spherical roller bearings (SRB) have a high load capacity and self-aligning feature that allows for some misalignment of the axis of rotation.Key to the self-aligning performance of SRB is the spherical profile of the bearing rollers acting in the bearing inner and outer ring raceways.
However, under rotation these geometrical forms interact to produce slippage at the contact surface points between the raceways and rollers.
With its HPS design, NSK has clarified for the first time in the world the mechanism that causes slippage and creates high friction on the surface, leading eventually to damage due to surface fatigue.
NSK further verified, by theoretical analysis and bench testing, that the friction can be reduced by controlling the motion of rotating rollers; and that a special surface treatment of the outer ring is effective in achieving this.
Based upon these findings, NSK developed mass-production technology and bearings, which can minimise slippage to prolong running life by more than twice that of conventional products.
NSK has detailed its innovative bearing products for the steel industry in a publication.
Running to 40 pages the free booklet provides a wealth of information regarding the choice of bearings for plant and equipment used in steelmaking processes.
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| GE380DW bearing | 380 | 520 | 190 |
| GE360DW bearing | 360 | 480 | 160 |