RU2405050C1 - Jewel alloy based on 585-standard gold - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: 585-standard gold-based alloy contains the following components in wt %: %: gold - 58.5-59.0; silver - 4.0-6.0; zinc -1.0-3.0; indium - 0.01-0.5; chromium -0.01-0.05, copper making the rest. Proposed alloy features the colour of "red Russian gold".

EFFECT: possibility to use proposed alloy for machine production of chains with high yield.

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Description

The invention relates to the field of metallurgy and relates to compositions of alloys based on gold, which can be used for jewelry production.

In a number of countries, including Russia, jewelry alloys of 585 red gold are widely used in jewelry. Copper gives a specific red tint to these alloys.

There are a lot of jewelry alloys based on gold 585, which are mainly used for the manufacture of various jewelry. These alloys have a good luster, beautiful color, affordable and contain, in addition to gold, copper, silver, and in some cases also zinc, nickel, palladium, [see E. Brepol. Theory and practice of jewelry. Ed. 3rd Per. with him. L., "Engineering", 1977. - 384 p. (p. 49-51)].

A variety of alloys is caused, inter alia, by a variety of different technological methods used in practice for the manufacture of various jewelry (the manufacture of wire and chain knitting, micro casting, stamping, etc.). The most sophisticated technologies that place high demands on the quality of gold alloys of 585 samples include the so-called "Continuous casting" - pulling the rod out of the melt in the crucible through the bottom mold and using the resulting rod in the manufacture of chains. Increased demands on the structure of the alloy and the stability of its properties are also imposed by machine technology for manufacturing chains of complex weaving (for example, chains of the "snake" type). The stable operation of chain-knitting machines requires high chemical uniformity associated with the constancy of the mechanical characteristics of the launched wire along the entire length, which, in turn, can only be achieved using a homogeneous gold alloy.

Attempts to use a known alloy containing, wt.%: 58.5-59.0 gold, 2.7-3.3 silver, 0.9-1.3 zinc, the rest is copper [RF Patent No. 2121010, C22C 5 / 02 stated 07/30/97, publ. 10/27/98], in the manufacture of chains caused a number of problems. The resulting jewelry had an insufficiently saturated color cast. During continuous casting, the rods were characterized by high chemical heterogeneity both in their length and in cross section. The above disadvantages led to a decrease in yield.

The closest in composition to the claimed alloy is a jewelry alloy based on gold 585 samples containing silver, zinc, indium and copper in the following ratio of components,% wt .:

gold - 58.5-59.0

silver - 4.0-30.0

zinc - 1.0-3.0

indium - 1.5-3.0

copper - the rest

[RF patent No. 2170280, C1, C22C 5/02, application. 12/29/1999, reg. Application No. 99127176/02, publ. 07/10/2001 Authors: Timofeev NI, Syutkina VI, Golikova NN, Ermakov AV].

This alloy is adopted as a prototype.

The prototype alloy allows (in the claimed range of component concentrations) to obtain jewelry of various color shades, including the so-called "Russian red" gold. The alloy is well polished and has relatively high consumer qualities.

The main disadvantages of this alloy include:

- the presence of dendritic segregation in the continuous casting of the alloy;

- insufficient constancy of physico-mechanical properties along the length of the wire made from the rod, which reduces the yield of products during machine chaining of chains of complex weaving;

- surface roughness in the manufacture of chains.

The task to which the proposed technical solution is directed is to develop a composition of a jewelry alloy based on gold of 585 specimen, which allows using it for the manufacture of machine chains of complex weaving with high yield, including using continuous casting technology.

The technical result is achieved by the fact that a jewelry alloy based on gold 585, containing silver, zinc, indium, copper, additionally contains chromium in the following ratio of components, wt.%:

gold - 58.5-59.0

silver - 4.0-6.0;

zinc - 1.0-3.0;

indium - 0.01-0.5;

chromium - 0.01-0.05;

copper is the rest.

Common to the known and claimed jewelry alloys based on gold 585 is the presence of silver, zinc, indium and copper in the alloy.

The gold content in the alloy is due to the requirement of providing fineness, i.e. in the manufacture of jewelry from an alloy, the latter must comply with the standard 585 test (GOST 30649-99).

The difference from the prototype alloy is the additional introduction of chromium into the inventive alloy while reducing the indium content.

The introduction of an alloy of refractory chromium into the alloy while reducing the indium content in the stated concentration limits causes a noticeable modifying effect. The latter consists in the emergence of a large number of crystallization centers — solid phase nuclei in the melt under continuous casting conditions. The formation of the fine-crystalline structure of the alloy ensures the stability of the physicomechanical properties of the semi-finished products obtained in the continuous casting process for the manufacture of wire, and, as a result, an increase in the yield of products in the machine manufacturing of jewelry chains made of “red gold”, including chains of complex weaving (type “ snake "). The formation of the fine-crystalline structure of the alloy during its crystallization leads to an increase in the surface quality of the manufactured jewelry and reduces the cost of their finishing.

The concentrations of chromium and indium in the alloy within the stated limits were established empirically and are optimal, since they improve the quality of semi-finished products obtained by continuous casting and subsequent processing, do not cause a significant increase in the temperature range of crystallization of the alloy, provide strength characteristics with a slight increase in microhardness of the alloy ( up to 1450-1500 MPa from 1350-1400 MPa for the prototype alloy), allow you to get the desired color of the jewelry with a smooth shiny surface.

An increase in the content of chromium and indium over the declared limits is impractical, since it leads to an excessive increase in the hardness of the jewelry alloy, increases the temperature range of its crystallization and reduces consumer value.

An example of alloy preparation.

Obtaining a jewelry alloy based on 585 gold was carried out by fusion of components in three stages.

At the first stage, direct alloying of base components resulted in a copper-chromium alloy.

For this purpose, pressed copper-chrome glazing beads and copper granules were loaded into the graphite crucible of the NEUTEC 515 induction foundry (USA).

The installation was closed with a lid and the displacement method filled the working area with inert gas - argon. The mixture was melted in argon medium. After complete melting of the components, the melt was periodically mixed for 10 seconds with an exposure between periods of 2 minutes. The total melting time is 10 minutes, followed by the discharge of the melt in the granulation mode into water.

The obtained granules of the ligature were dried, tested and sent a sample for chemical analysis.

Chemical analysis of the sample indicated that the resulting ligature contains 1.58% chromium, the rest is copper.

The resulting ligature in the form of granules was later used at the last (third) stage to obtain a jewelry alloy based on 585 gold.

At the second stage, they got another necessary ligature - a copper-zinc alloy. For this, 50.0 g of granulated zinc of the ChDA grade was loaded into a graphite crucible, 50.0 g of granulated copper was added, a coating flux — crushed fused drill — was poured onto the surface, and the crucible was placed in a chamber electric furnace. The furnace was closed with a lid, the smelting chamber was filled with inert gas, argon, and turned on for warm-up. The mixture was melted in argon medium. After a 10-minute exposure of the melt at a temperature of 950 ° C, the crucible was removed from the furnace and cooled. A copper-zinc alloy ingot weighing 91.0 g was removed from the crucible and cut into pieces of 10-15 g each. A sample of the alloy was analyzed by a chemical method. The alloy contains 45.0% zinc, the rest is copper.

The resulting alloy was then used in the third stage — in the manufacture of a jewelry alloy based on 585 gold.

To do this, 20.0 g of copper-chromium ligature, 50.0 g of granular refined silver, 30.0 g of copper-zinc alloy (containing 45.0% zinc) were loaded into the graphite crucible of the NEUTEC 515 induction foundry (USA) , the rest is copper), 315.0 g of granulated copper, 1.0 g of indium grade ХЧ and 586.0 g of granulated gold of the grade ЗлАГ-1.

The installation was closed with a lid and the displacement method filled the working area with inert gas - argon. The mixture was melted in argon medium. After complete melting of the components, the melt was periodically mixed for 10 seconds with an exposure between periods of 2 minutes. The total melting time of 10 minutes, followed by the discharge of the melt in the granulation mode in water.

The obtained granules of the gold alloy were dried and weighed. The mass of the obtained alloy was 1000.0 g. The alloy was tested and the sample was sent for chemical analysis.

Chemical analysis of the sample showed that the obtained gold-based jewelry alloy contains, wt.%: 58.58 gold, 1.30 zinc, 4.98 silver, 0.10 indium, 0.03 chromium, and copper - the rest.

The density of the alloy (13.1 g / cm ³ at 20 ° C) and the microhardness of the alloy were measured in the annealed state (HV5 = 140 kgf / mm ² ) and in the cured (HV5 = 270 kgf / mm ² ).

The obtained gold-based jewelry alloy corresponds to the 585th test, has a saturated color of “Russian red” gold and has been successfully used in the manufacture of jewelry chains using machine knitting methods, including “snake” chains.

Claims (1)

Jewelry alloy based on test gold 585 containing silver, zinc, indium, copper, characterized in that it additionally contains chromium in the following ratio of components, wt.%:
gold 58.5-59.0 silver 4.0-6.0 zinc 1.0-3.0 indium 0.01-0.5 chromium 0.01-0.05 copper rest