Open Access Conference Proceedings

Surface defects on metals products often have their root cause created during the hot rolling process by oxide scale in cavities and indents becoming embedded from the plastic deformation. The size and aspect ratio of these initial surface features are critical parameters determining whether they will be eliminated or not by the rolling process. The present research investigates the effects of initial defect geometry and the evolution mechanisms in the first hot rolling pass with the substrate being a high-silicon electrical steel. Laboratory hot-rolling experiments were carried out on blocks with open cavities of different geometries machined into the surface. The final geometry of the longitudinal and transversal profiles of the deformed defects were analysed from metallurgical cross-sections. The results were in good agreement with the literature, initial cavity dimensions was found to be crucial to determine whether the defect is eliminated or not after the rolling operation, in this case defects with a depth of 1 mm almost disappeared after the rolling. The results also show that for a given constant initial cavity width, the final defect width shows an inverse relationship with the selected initial depth. It has also been observed that at similar initial depth the wider defects evolve to much shallower surface features. The obtained results indicate that the length of the final defect is only dependent on its initial length along the rolling direction.

Keywords: Hot Rolling, Surface Defect, Electrical steel, Deformation

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