Method for assessing the surface quality of copper cathodes
One of the criteria for the quality of high-purity copper, which makes it possible to evaluate its mechanical properties and, accordingly, its suitability for use by consumers, is the spiral elongation number which, in accordance with the requirements of the European Standard EN 12893, must be at least 400 mm. In order to stabilize spiral elongation number at the required level, an estimate is made of its distribution along the cathode web. Experimentally obtained results, processed using mathematical statistics methods, showed significant discrepancies between the spiral elongation values in the central and other parts of the cathode (upper, lower, side), which indicates an uneven distribution of the spiral elongation number along the cathode web. It was found that in order to form a representative analytical sample under cathode copper cathode production of the Polar Division of MMC «Norilsk Nickel», cathode testing should be performed using methods that include all areas of the cathode web, including edges and ears. To determine the dependence of the spiral elongation number on the surface quality of copper cathodes, a special technique has been developed, based on the detection of the most frequently encountered defects in the surface of the cathode web, which is assigned a certain numerical value in accordance with the ranking results. The proposed scoring system for the quality of cathodes in appearance allowed us to establish for the first time that stabilization of the spiral elongation number at a level of at least 400 mm is possible if the defectiveness of the cathode surface does not exceed 17 points per bath. The technique has found practical application for assessing the surface quality of copper cathodes under current production conditions.