Cylindrical roller bearings for continuous casting machines

NUB cylindrical roller bearings are designed specifically for highly demanding steel industry applications, particularly the non-driven side of strand guide rolls, such as those found in the straightening section of continuous casting machines.

NUB roller bearings offer users many benefits. For instance, the bearings not only have the ability to handle thermal expansion of the shaft, but can accommodate misalignments of the strand guide rolls as large as 12 angular minutes. Importantly - and unlike competitor bearings for continuous casting machine applications - these two attributes of NUB series bearings function in unison. To explain further, as the inner ring offsets the outer ring under thermal expansion, it does so without compromising the bearing's misalignment compensation capabilities. Self-alignment is facilitated through a proprietary internal design with special profiling on the rings and rollers.

In the continuous casting process, one strand has multiple sections, each of which can comprise various segments. Once the cast slab has left the mould it proceeds through sections that include the bender and the bow, before passing via a straightener section to the horizontal withdrawal section, after which it is cut to length and left to cool. A single strand can have between 10 to 17 segments, distributed among the various sections.

With hundreds of bearings located on a typical strand, not to mention that some continuous casting shops run two parallel strands, the bearings are process critical. However, such bearings have to endure demanding operating conditions, not least high levels of mechanical stress, as well as liquid and mist cooling water. In addition, the very low speeds (less than 10 rpm) of the roller table drives can be problematic for traditional spherical roller bearings as their design imposes very tough lubrication requirements.

In contrast to conventional roller bearings, pure rolling friction occurs in NUB bearings thanks to predominant line contact in the raceway. Friction is therefore lower and wear is reduced. Straightforward installation is another benefit, whereby snap rings are deployed to prevent accidental disassembly during mounting/dismounting and handling.

Compared with the previous generation series, NSK's NUB bearings are able to treble service life, even when faced with the demanding environmental conditions of strand guide rolls. For this reason, the bearings help facilitate cost-effective, continuous and highly-productive steel manufacturing with reduced cost of ownership.

The new flyer for NUB series cylindrical roller bearings is available online at www.nsk-literature.com/en/nub-series.

For further information about NSK's products for continuous casting machines, please consult the NSK Europe website.