Method for detecting faults on the surface and close to the surface in a rolled product

摘要

The method consists in an indicator coating being applied to the product (1), followed by heating of the surface thereof by means of high-frequency currents. The high-frequency heating causes a temperature gradient between the faulty and fault-free sections of the product (1), which is sufficiently large to produce a thermochemical conversion of the indicator coating accompanied by a change of its colour at the faulty points. The dark traces on the light background of the coating localise the faults on the surface and close to the surface of the product (1). The high-contrast image of the faults on the surface of the product (1) is retained for a considerable time, so that it is not necessary to employ fault-marking instruments. Information concerning the faults can be utilised to clean faulty sections of the surface of the product. <IMAGE>