Method for detecting surface and subsurface flaws in rolled products

摘要

A method for detecting surface and subsurface flaws in rolled products in which an indicator coating is applied to the surface of a rolled product, whereupon the coated surface is heated with high-frequency currents. The high-frequency heating produces a temperature gradient between good and defective portions of the blank, which is sufficient to bring about a thermochemical transformation of the indicator coating over the defective areas, accompanied by a change in the color of the coating in those areas. Dark spots on the light coating indicate the locations of surface and subsurface flaws. The sharp images of flaws are visible over a long period of time on the surface of the rolled product, which makes it possible to dispense with the marking of flaws. The defective areas thus identified are chipped.