There has been some success in continuing efforts to increase the service lifetimes of the guide rolls in hot-roll-slitter machines in the steel industry. In these machines, hardened knives are used to slice sheets of steel from large steel coils. The sheets are up to 0.375 in. (9.525 mm) thick and have various lengths and widths. A steel coil to be cut is positioned in a hot-roll-slitter machine by use of four guide rolls (two on each side) that spin as the steel passes between them on the way to the knives. The guide rolls are thus subjected to harsh grating and scraping conditions as well as high-pressure rubbing and friction as the coil is unwound to be sliced. Consequently, deep grooves are quickly worn into the guide rolls, making it necessary to replace the guide rolls and thereby causing several hours of down time.
Guide rolls of modified design were constructed in an initial effort to increase the longevity and usefulness of the guide rolls and to reduce slitter-machine down time for changing of guide rolls. Each such guide roll included a shaft fabricated from 4140 steel, plus a sleeve that was machined, then pressed onto the shaft. A collar was added to key the sleeve in place. Then, to make the sleeve more resistant to wear, an abrasive-resistant material (PS-212) about 0.015 in. (0.38 mm) thick was plasma-sprayed onto the sleeve. In tests, the average life span of these rolls was found to be more than double that of rolls of the original, unmodified design. However, a new failure mode occurred; the coatings eventually became detached from the sleeves.
In a second modified design (see figure), each roll was equipped with a shell sleeve made from a more wear-resistant tool steel (D-2), which was machined and then heat-treated for longer wear life. In tests on slitter machines, the life spans of rolls of this second modified design were found to be increased by factors of at least four to five. In addition, the time needed to change the sleeves was reduced greatly, and the reduction in cost of changing sleeves (in comparison with changing entire rolls) was found to be substantial. Therefore, until a more-compatible coating can be found and proven advantageous in tests, rolls of the heat-treated shell-sleeve design are in use on the affected slitter machines, saving time and money.
This work was done by Richard Soltis and William Waters of Omni Corp. and Darryl Bruck of Diversity Manufacturing Co. for Lewis Research Center. No further documentation is available.
Inquiries concerning rights for the commercial use of this invention should be addressed to
NASA Lewis Research Center
Commercial Technology Office
Attn: Tech Brief Patent Status
Mail Stop 7 - 3
21000 Brookpark Road
Refer to LEW-16534.