Semi-Finished Products: Rods, Billets and Wires

Abstract

Manufacturing defects occurring in semi-finished products of this type can either be internal or surface defects. Internal defects originate either from ingot defects elongated during rolling or drawing, namely shrinkage cavities and inclusions, mainly in the core ; others are rolling and drawing defects, such as piping, particularly in the case of non-ferrous metals, and cracks in the core, which in cross-section appear flat or star-shaped. Surface defects, e.g. on rods, usually result from drawing defects such as radial incipient cracks or spills which penetrate to the surface at a flat angle. Since all flaws extend in the longitudinal direction, this requires that the axis of the sound beam lies in a cross-sectional plane (Fig. 23.1), either normal or oblique to the surface. Also used are surface waves in the circumferential direction.