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INVENTION
Patent of the Russian Federation RU2082816
METHOD OF RECOVERY COLOR OF OXIDIZED ARTICLES FROM GOLD ALLOYS,
CONTAINING COPPER
Applicant's name: Larets Limited Liability Partnership
The name of the inventor:
The name of the patent holder: Limited Liability Partnership "Larets"
Address for correspondence: Voroshilov VA; Beltyukov AG; Nikitenko A.V .; Bryukhanov S.B.
Date of commencement of the patent: 1994.12.14
The invention relates to metallurgy and can be used in the jewelry industry in the processing of castings and finished articles containing copper, the surface layers of which are excessively enriched in gold and silver as a result of the action of an oxidizing environment. According to the first variant, the process is carried out in the following sequence of operations: removal of copper oxide from the surface of the article and subsequent thermodiffusion treatment in a copper-neutral medium at a temperature above the AB- type ordering temperature until color standards are achieved. In the second variant, thermal diffusion treatment is carried out at the same temperatures, but in a reducing medium with respect to copper.
DESCRIPTION OF THE INVENTION
The invention relates to metallurgy and can be used in the jewelry industry, namely, in the processing of castings, blanks of products from gold alloys containing copper, the surface layers of which are excessively enriched in gold and silver in an oxidizing medium (casting cooling, recrystallization annealing, soldering, .P.).
The closest way to the proposed method is the method of restoring the color of oxidized products from gold alloys containing copper ( Gurova LA Artistic casting from precious metals, M. 1988, p.161 ).
The method consists in removing copper oxide from the oxidized surface with a weak solution of sulfuric acid (bleach), and then enriched with gold and silver, the surface layer is removed by directive technology by electrochemical etching.
To the disadvantages of the method can be attributed large losses of precious metal.
The object of the invention is to reduce the cost of products from gold alloys containing copper.
The technical result is the elimination of losses of precious metals.
The result of the first embodiment of the invention is achieved in that in the method for restoring the color of oxidized articles of gold alloys containing copper consisting in removing copper oxide formed on the surface of the articles as a result of heat exposure to them in an oxidizing environment, the products are then thermally diffused in a neutral For copper medium at a temperature higher than the AB-type ordering temperature, control the color of the products, and when the color indices are reached, the thermal diffusion processing is stopped.
The technical result in the second embodiment of the invention is achieved in that, according to the method for restoring the color of oxidized articles of copper-containing gold alloys, the articles are subjected to thermal diffusion treatment in a copper-reducing environment at a temperature above the AB- type ordering temperature, The normative indices of the color, the thermal diffusion processing is terminated.
According to a first variant of the proposed method for restoring the color of oxidized articles of gold alloys containing copper formed as a result of thermal action in an oxidizing environment, the copper oxide film is removed by placing the articles in a weak solution of sulfuric acid for 1 3 min. As a result, the surface of the products is cleaned and acquires a greenish-gray hue due to the increased concentration of gold and silver in the surface layers of products. The articles are then placed in a medium neutral for copper, heated to a temperature higher than the AB-type ordering temperature. In this case, under the influence of temperature, thermal diffusion of copper from the deep layers of products to the surface of products occurs, and gold and silver in the opposite direction. As a result, the color of the products gradually changes in the direction of restoring its normative parameters for the given alloy. The color is monitored visually or by a septrophotometer. After the color reaches the standard values, the thermal diffusion processing of the products is stopped.
According to a second variant of the proposed method for reducing the color of oxidized articles of copper-containing gold alloys , the articles are placed in a reducing medium with respect to copper, heated to a temperature above the AB-type ordering temperature. At the same time, under the influence of temperature and reducing medium, copper is recovered from copper oxide, and then the thermal diffusion of the reduced copper into copper-depleted layers of products. As a result, the color of the products gradually changes in the direction of restoring its normative parameters for the given alloy. The color is monitored visually or spectrophotometer. After the color reaches the normative parameters, the thermal diffusion processing of the products is stopped.
In both variants, it is possible to use a Solo conveyor furnace to create the necessary environment and temperature conditions. In this case, dissociated ammonia can be used as a medium, reducing copper from copper oxide. Color control is carried out at the exit from the furnace, which causes a cyclic realization of the method. In this case, each cycle includes a sequence of thermal action operations in the copper reducing medium, rapid cooling, and then color control. The number of cycles depends on the temperature in the oven, the dimensions of the products, the speed of the conveyor belt. When the color of products reaches the normative parameters, the cycles for these products are terminated.
To carry out continuous color control visually or a spectrophotometer, a non-standard construction is used, where the products are stationary during the thermal action. The immobility of products during heat exposure is especially important for color control by spectrophotometer by comparison with a reference product. In this case, the color control is carried out through a special window made of quartz glass, and the thermal chamber itself is sealed for the duration of the heat treatment. A copper-reducing medium can be provided similarly to Solo furnaces or other means, for example, by inserting a carburettor into the chamber. The carburetor is known to contain barium carbonate (20-25%) , calcium carbonate (3.5-5 %) and charcoal (rest) (GOST 2407-64) . When heated, the carburettor generates atomic carbon, which binds oxygen, located in a thermal chamber. In addition, atomic carbon restores copper from copper oxide. The total time of heat treatment varies from 3 to 12 15 min and is determined by the achievement of the color of the products of the standard indices. The optimum heat treatment temperature is 600 - 750 ° C. However, other temperature values are possible, but not lower than the ordering temperature of type AB , which, for example, for the alloy of sample 585 is 450 ° C. For different alloys, this temperature has a different value: its magnitude is significantly affected by the silver content, the more silver, the lower the ordering temperature. The presence of this lower temperature boundary for thermal diffusion treatment is due to the fact that when the structure of the alloy is ordered in type AB, the alloy becomes brittle, and its plasticity decreases several times in comparison with the disordered state.
The use of the proposed method in the jewelry industry will make it possible to eliminate losses of gold and silver in the process of restoring the color of products lost by them as a result of thermal action on them in an oxidizing environment.
CLAIM
A method for recovering the color of oxidized products from gold alloys containing copper, comprising removing the copper oxide formed on the surface of the articles as a result of the thermal action on them in an oxidizing environment, characterized in that the products are then thermally diffused in a copper-neutral medium at a temperature above the temperature Ordering by type AB , control the color of the products, and when the standard color indices are reached, the thermal diffusion processing is terminated.
A method for restoring the color of oxidized articles of gold-containing alloys containing copper, characterized in that the article is subjected to thermal diffusion treatment in a reducing medium with respect to copper at a temperature above the AB- type ordering temperature, controlling the color of the products, and when the color standards are reached, the thermal diffusion processing is terminated.
print version
Date of publication 11/21/2006
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