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Welded Repair of Section Mill Rolls |
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The Cost of Wear in Section Mills
A characteristic of primary and secondary section-mill rolls is that different passes of the roll will wear at different rates. Replacing an entire roll with new because of severe local wear is an extremely inefficient practice.
Repairing by welding has been shown to extend the useful life of section mill rolls; has resulted in better shape control through a reduction in wear rates; and in one instance reduced the maintenance costs by £230,000. |
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The multi-functional nature of section mill rolls means they generally exhibit uneven wear patterns. The rolling effort, either by number of passes or by reduction, is concentrated in certain passes, which consequently loose their shape faster. Therefore, entire rolls would often be scraped despite the |
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majority of the roll’s profile being able to continue for further campaigns. At a cost of several hundred thousand pounds sterling per roll this represented a substantial drain of any plant manager’s budget.
Welded Repairs - Versatility of process
The great advantages of using welding materials, and specifically Weldclad welding materials, to repair section mill rolls are the versatility of the process, and the variability of the consumables.
Not only can areas of localised wear be swiftly and simply repaired, but also specific material properties can be chosen depending on the requirements |
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of a particular pass, for example better wear resistance can be selected for particularly heavy wear passes.
Welded Repairs - Reducing Wear Rates
At the CORUS (formally British Steel) plant in Scunthorpe the use of Weldclad 4 on primary bloom mill rolls has resulted in extended rolling campaigns as the rate of wear was significantly reduced. Longer campaigns meant fewer roll changes were required significantly enhancing productivity. Additionally, the superior surface properties of Weldclad 4 meant that the dressing requirement when the roll was removed from service reduced by 50%, from 20mm to 10mm.
The enhanced surface properties also lead to better shape control of the product, as the tendency of the pass to form a rhomboid profile was reduced; and also lead to a reduction in the requirement to dress or scarf the product. Indeed, over the two-year period during which Weldclad 4 was being trailed the plant saw annual cost savings approximating to £230,000.
A whole variety of section mill rolls can and have been weld repaired using Weldclad branded consumables, and the following represent the increases in service life produced by Weldclad materials when compared with new roll lives:
Primary mill Rolls: 4:1
Secondary Rolls: 2:1
Piling Rolls: 2:1
Heavy Section Rolls: 3:1
Rail Section Rolls: 3:1 |
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