Wear Resistant Alloys for Plate Mills

"Weld reclamations of steel rollers have shown to be of equal performance to the rollers clad from new with a considerable cost advantage.
All future requirements to be steel sleeves with Weldclad 8 overlay."
Lackenby light plate mill

Wear Resistance in Plate Mills
Many of the operating parameters in plate mills are similar to those found in hot strip mills. Specifically, operating temperatures are high meaning only heat resistant alloys are appropriate. Otherwise there will be failures, like loss of hardness. In addition, a consequence of high operating temperatures is an abundance of cooling water, which provides ideal conditions for corrosive processes to quickly become established. And, reducing heavy sections such as plate means working

loads are substantial, meaning the effects of wear can be significant and rapid.

Wear Costs on Quality and Downtime
For example, plate mill managers in the US and Asia were increasingly reporting very high wear rates of work rolls in the hot leveller. Rollers were being withdrawn from service after less than 250,000 tonnes of through put. In addition, the work rolls were marking or printing onto the product.

Initial investigations by Corewire's technical staff identified two causes of the marking effect. Firstly, the very high pressures excreted by the backup rolls were leaving edge marks on the work roll. The work roll was deforming around the sharp edge of the backup roll. Additionally, the operating environment of the work rolls was leading to the nucleation of micro-cracks in the rolls surface. Very fine particles of oxide, scale and dust were then becoming mechanically trapped in the cracks. Over time more scale and debris would preferentially adhere to these areas and become compacted into a hard mass, which would print onto the plate product.

 

Corewire recommended using Weldclad 8 on both the work rolls and the backup rolls. However, the heat treatment of the backup rolls was manipulated to leave them approximately 5HRc softer than the work rolls, thus avoiding the edge making effect. The excellent thermal fatigue resistance of Weldclad 8 also meant an end to the marking issues, by preventing the nucleation of micro cracks in the first place. Weldclad 8 increased the service life of these rolls to over 1 million tonnes of steel through put, not only reducing the cost of repairs, but also significantly reducing the plate mills down time and therefore the costs associated with lost productivity.

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