Correlation between the loading of work-rolls, banding and rolled-in scale

During operation work-rolls in hot-strip rolling mills are subjected to high thermomechanical loads. These loads lead to a phenomenon called banding - a surface deterioration of the roll in the first stands of the finishing-train being responsible for rolled-in scale at the surface of the strip. To correlate the work-roll's loads with the appearance and amount of rolled-in scale, an equivalent load parameter (ELP) is proposed. The ELP is derived by studying the physical background of banding. Since low-cycle-fatigue is identified as governing mechanism of banding (initiation and growth of cracks), the ELP has to be proportional to the rolling-pressure, the contact time between the hot strip and the roll in the roll-gap and, hence, also the strip length. By analyzing the vast body of data of an industrial rolling mill, a correlation is confirmed between the ELP and the rolled-in scale as detected by a surface control system. This work aims at the development of a prediction tool for rolled-in scale serving to optimize rolling schedules.