Abstract: Scrap containing copper is discriminated from iron scrap after being pulverized by imaging iron scrap using a color TV camera, treating RGB signals processed by each of the points in the image as a color vector, and discriminating scrap containing copper from iron scrap when the saturation value of the color vector is larger than a predetermined value and the hue angle of the color vector lies within a predetermined range.

Abstract: A method of water cooling a hot-rolled steel plate is disclosed. In this method, while a hot-rolled steel plate is being advanced lengthwise, a plurality of nozzles spray cooling water to the steel plate, and thus the plate is cooled to a predetermined temperature at a predetermined cooling rate. Before, while and after the plurality of nozzles carry out water-cooling, temperatures are consistently measured at predetermined temperature measurement points in cross-sectional areas of temperature measurement positions which are arranged lengthwise at predetermined locations of the steel plate. Each time such measurement is performed, degree of deformation of the plate is calculated on the basis of temperature differences between the temperature measurement points. When the calculated degree of deformation is not within an allowable range, corrections are made on the distribution of the water supplied by the plurality of nozzles.