RU2514898C1 - Assay 585 gold-based alloy of red colour - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed gold-based alloy comprises the following components in wt %: gold - 58.5-59.0, silver - 7.5-8.5, ruthenium - 0.4-0.5, copper making the rest.

EFFECT: better mechanical properties, expanded applications in jewellery.

2 tbl, 5 dwg

Description

The present invention relates to the field of metallurgy of gold-based alloys for the manufacture of jewelry. The alloy has a saturated color of "Russian red" gold, has an increased complex of mechanical properties and a fine-grained structure.

Known alloy based on gold (AS No. 1585364, IPC С22С 5/02. Alloy based on gold / Kondakov E.N. All-Union Scientific Research and Design Institute of the Jewelry Industry of the Leningrad Production Association "Russian Gems", publ. 08/15/90, bull. No. 30), containing, wt.%: Gold 58,0-59,0; silver 9.0-11.5; manganese 2.0-3.5; additionally contains zinc 3.0-4.0; copper is the rest. This alloy has high mechanical properties, namely, increased ductility in the cast state, however, when using it to produce cast billets by continuous casting, unevenness in length occurs, since the alloying elements that make up the alloy do not provide a fine-grained structure from beginning to end long ingot. This leads to a difference in the mechanical properties and structure of the metal during subsequent operations of metal forming (high-quality rolling and drawing), which leads to breaks during wire drawing and marriage in the manufacture of jewelry chains on chain knitting machines.

Closest to the invention is an alloy based on red gold of 585 samples (RF Patent No. 2391425, C22C 5/02, 02/18/2009), containing, wt.%: 58.0-58.6 gold, 4.0-6, 0 silver, 1.0-2.9 zinc, 0.01-0.4 ruthenium, the rest is copper.

This alloy is adopted as a prototype. The prototype alloy in the claimed range of component concentrations provides an increase in the level of mechanical properties and their uniform distribution along the length of the ingot. However, it does not fully meet the requirements for the structure of deformed semi-finished products, which are obtained with the toughening of their processing modes. An example is the production of thin-section wire for jewelry production, where the coarse-grained structure of semi-finished products can lead to breaks (marriage) when drawing with the use of increased drawing coefficients.

The main objective of the invention is to create a new alloy based on red gold 585, having a high level of consumer and mechanical properties due to the formation of a fine-grained structure of semi-finished products, their uniform distribution along the length of the workpiece, expanding the scope of the alloy in jewelry manufacturing.

To solve this problem, the proposed alloy based on gold, containing silver and copper, additionally contains ruthenium in the following ratio of components, wt.%:

gold - 58.5-59.0;

silver - 7.5-8.5;

ruthenium - 0.4-0.5;

copper is the rest.

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

Common to the known and claimed alloys based on gold 585 samples is the presence in the alloy silver, ruthenium and copper. The difference from the prototype alloy is to increase the mass fraction of silver and ruthenium in the alloy while reducing the copper content.

Copper provides increased tear resistance and the necessary red color.

Silver in the range of 7.5-8.5 wt.% Increases the ductility of the alloy, softness, ductility and its corrosion resistance during casting.

Ruthenium is a modifying additive that allows you to get a fine-grained structure, while increasing the ductility of the alloy and is the alignment of properties along the length of the cast billet. When the ruthenium content is within the claimed limits, a dispersed structure of dendritic cells is observed over the entire cross-section of the ingot and the modification effect is increased, which provides more crystallization centers and, as a result, a fine-grained structure. At a Ru content of <0.4%, this effect decreases in proportion to the mass fraction of the modifier in the alloy, and at a Ru content of> 0.5% due to a decrease in its solubility in gold, fragments of insoluble ruthenium are observed in the structure of semi-finished products, and the modification effect is reduced.

The inventive alloy, therefore, in comparison with the known alloys has a more uniform fine-grained structure and an increased level of mechanical properties and has higher technological properties, which allows it to be used in the manufacture of jewelry by casting and metal forming methods.

The alloy was obtained as follows. Silver and zinc were fused in a protective atmosphere (argon), then 80% of the calculated amount of copper and granulation of the melt were introduced into water. The remaining amount of copper with the modifier was fused similarly and subjected to granulation. This was followed by direct fusion of the calculated amount of gold and ligatures in a protective atmosphere, continuous casting.

To study the mechanical properties of the alloy, samples were analyzed in a cast and deformed state. Tensile strength was determined on deformed samples using a tensile testing machine LFM 20 kN. The structure of the alloy samples at all stages of the heat and mechanical processing was analyzed using metallographic research methods, and the hardness was measured using a Vickers DM8 digital microhardness tester.

For comparison, table 1, 2 shows the compositions of the claimed and known alloys and physico-mechanical properties of the samples.

Table 1 The compositions of the claimed and known alloys No. Alloy The chemical composition of the alloy, the mass fraction of the component,% Ai Ag Cu Zn Ru one Famous 58.5 5,0 33.5 2.9 0.1 2 The claimed 58.5 8.5 32.6 □ 0.4 3 The claimed 58.5 7.5 33.5 □ 0.5

table 2 Properties of the claimed and known alloys No. Alloy Microhardness HV, kg / mm ² Temporary tear resistance, MPa one Famous 197 920 2 The claimed 181 980 3 The claimed 170 950

Figures 1 and 2 show the cast metal structures of the known and claimed alloys, respectively. The inventive alloy in comparison with the known, due to the optimal combination of components in the alloy in the specified quantitative ratio, has a finer and more uniform structure and a high level of mechanical properties. For comparison, Figure 5 shows the structure of the metal in the molten state with a Ru content of 0.6%. It can be seen that in the structure of the alloy modified with Ru> 0.5%, coarse inclusions of insoluble ruthenium in the metal volume were revealed, which negatively affects the properties and quality of the obtained semi-finished products and products from them. This is due to the fact that ruthenium did not have time to dissolve during the preparation of the alloy, since it dissolves to a limited extent not only in the solid, but also in the liquid state. To exclude the formation of such inclusions, there is a restriction on the content of ruthenium in the composition of the 585 gold alloy, the mass fraction of which should not exceed 0.5%.

Figures 3 and 4 show the structure of the inventive alloy in a deformed state obtained in the process of high-quality rolling and drawing with varying degrees of deformation. It can be seen that the deformation of the metal (Fig. 3) with a degree of 41% (high-quality rolling) does not significantly change the cast structure of the claimed alloys (Fig. 2), only a slight curvature of the dendritic crystals of the alloy is observed. An increase in the degree of deformation to 99% (drawing) leads to elongation of the crystals in the direction of deformation and the formation of a fibrous structure (Fig. 4). At the same time, a fine-grained structure is observed over the entire cross section of the deformed workpiece, regardless of the place of sampling.

The concentration of ruthenium in the stated limit provides an increase in strength characteristics with a slight decrease in the microhardness of the alloy (table 2). Deformed semi-finished products of the inventive alloy in comparison with the known one possess not only a more uniform fine-grained structure along the entire length, but also are characterized by an increased level of strength properties, which positively affects the quality of finished jewelry products and confirms the effectiveness of ruthenium modification in the range 0.4-0.5 %

The proposed alloy has the entire range of consumer and technological properties for the manufacture of jewelry by casting and pressure treatment methods, provides a fine-grained structure, an increased level of mechanical properties and their distribution along the length of cast and deformed semi-finished products, which significantly expands the scope of the new alloy.

Thus, the use of the inventive alloy in comparison with the known allows not only to increase the technological properties of the alloy and use it in the manufacture of jewelry by casting and metal forming, but also to reduce the grain size in semi-finished products, which makes it possible to apply processing modes using increased degrees deformation.

Claims (1)

An alloy based on gold of red color 585, containing copper, silver, characterized in that it additionally contains ruthenium in the following ratio of components, wt.%:
gold - 58.5-59.0;
silver - 7.5-8.5;
ruthenium - 0.4-0.5;
copper is the rest.

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