The transformation of defects in continuous-cast semifinished products into surface defects on rolled products

Abstract

The rolling of steel transforms certain defects formed during the steelmaking operation into other, outwardly similar defects (such as blowholes, longitudinal cracks, and folds). Like steelmaking defects, the defects formed during rolling cannot always be unambiguously evaluated by visual inspection and distinguished from the flaws formed during production of the steel. For example, it is sometimes difficult to distinguish laps from rolled-in cracks or to distinguish rolled-in scabs from folds. Accurate classification of surface defects on rolled products according to their causes and the stage of the production process in which they were formed is essential to improving product quality and reducing the cost of producing steel and rolled products, since it makes it possible to promptly make corrections to the process. The degree of accuracy with which the origin of a given defect is determined depends on the degree of perfection and reliability of the inspection methods and equipment used, as well as on the system implemented to monitor the production process.