This paper describes the results of the research on refined gold bullions surface upgrading. Gold in bullions by weight 11 000 - 13 300 g is the saleable product of refineries. The surface of gold bullions should be without stains and slag inclusions and meets with GOST and trading requirements. The bullions covered with a mat surface film are periodically obtained during cathode metal remelting. The presence of such a film has no negative effect on the quality of the obtained products and alloys. Blasting of crystallised gold speculum with benzo- and air mixture in casting molds followed by a surface cleanup gives the bullion a commercial type. However, stains and a film reappear while re-melting these bullions into small measuring bullions. On the one hand, the problem of a film on gold bullion seems to be insignificant in total refining circuit. But it should be taken into consideration that this gold bullion is the product of collective work of geologists, ore concentration specialists and metallurgists. And if after the acquisition of these gold bullions by foreign companies, the 12 kg bullions are re-melted into small measuring bullions for their accumulative selling to consumers and if a dark film appears on the surface of each measuring bullion, in this case the profitable sale is impossible. As a result, all the obtained lot of gold is returned, penalties are paid and the work of gold-mining industry specialists is discredited. It was found that, since molten refined gold contacts with the walls of a graphite crucible and casting molds, microimpurities of gold, silicium and other elements passing into the melt can be possible also through these elements liquation of covering of gold surface as a film. It mainly consists of iron with insignificant amount of silicium, aluminium, magnesium, calcium and potassium. It was showed that a large number of iron inclusions from 1 to 300 μm can be found at the top part of some refined gold bullions at the depth of 150 μm.
展开▼
