Surface defects—evolution and behaviour from cast slab to coated strip

Surface defects can evolve in a number of ways during the hot rolling of strip products. Over the past few decades the causes of many defects have been determined and countermeasures introduced, but one issue still remains unresolved. This is sliver, which is usually observed after the galvannealing (GA) process as thin white lines. A proposal is made to determine the likely causes of this defect, using backward material tracking to determine the source location. Material tracking is a recent innovation that relies on FE based models to provide a framework for calculating material movement during hot rolling operations.