Effects of Edge Trimming and Cold Reduction on Edge Quality of Cold-rolled Strip

by Z.H.J. Gu, W.Y.D. Yuen

Publisher - BlueScope Steel Limited, Australia

Category - General Novel

Quality requirements for cold-rolled products include dimensional accuracies (in particular, thickness and width), good flatness, and defect-free strip surface and edges. High expectation on thin gauge and ultra-thin gauge products has imposed increasing challenges to satisfy these quality demands. This paper discusses issues associated with edge trimming at the pickle line and their effects on the edge quality of the cold-rolled strip. Little systematic studies have been conducted on how trimmed edge quality affects the edge crack or serrated edge defect after cold rolling. It has been well accepted, however, that the cut-to-break ratio of trimmed edges is paramount to ensuring quality cold-rolled edges. This is normally controlled by adjusting the gaps and overlaps of the edge trimmer blades, with a 33:67 cut-to-break ratio generally regarded as the optimum. In this paper, we report results from our experimental studies on the mechanism of shearing the strip edge, in particular, the formation of the cut and break regions. In addition, the behaviour of these cut and break regions, and the evolution of the edge cracks, during cold rolling will be discussed. The results from this study indicate that the cut and break regions are not deformed uniformly during rolling and the edge cracks arising from the cut and break regions exhibit different features.

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