RU2405051C1 - White palladium-based jewel alloy - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed alloy contains the following components in wt %: palladium - 95.0-99.5; cobalt - 0.2-3.0; iridium - 0.05-0.6; silver - 0.1-1.5; iron - 0.05-0.6, copper making the rest.

EFFECT: machine-made high-standard jewels produced by investment casting, for example of chains.

1 tbl, 2 ex

Description

The invention relates to the field of metallurgy of precious metals, in particular to palladium-based alloys used for the manufacture of jewelry, mainly for the manufacture of chains and microcasting of products 990 and 950 samples.

Palladium-based alloys are widely used in jewelry production due to their high consumer qualities, which bring them closer to platinum products. At a relatively low cost, they have a beautiful appearance, corrosion resistance to external factors, good polishability, are well processed.

Highly demanding palladium jewelry products, in particular, products of 990, 950 and 900 samples, have been in greatest demand in the world market recently. At the same time, in Russia until recently, only jewelry palladium alloys no higher than 850 samples were standardized and produced.

In particular, a white color jewelry alloy based on palladium 850 samples is known, containing, wt.%:

Palladium 85.0

Silver 13.0

Nickel 2.0

(Interstate standard GOST 30649-99. "Alloys based on precious metals jewelry. Stamps. Interstate Council for Standardization, Metrology and Certification. Minsk, p. 4, publ. 05/28/99)

The disadvantages of this alloy include: the impossibility of its use in the manufacture of high-grade (900, 950 and 990 samples) jewelry, relatively low casting properties, and a tendency to tarnish under certain environmental conditions. All this complicates its use in the manufacture of jewelry oriented to the world market.

The closest in composition to the claimed is a white colored jewelry alloy based on palladium containing cobalt, iridium and copper in the following ratio of components, wt.%:

Palladium 90.0-95.5

Cobalt 3.0-7.0

Iridium 0.03-0.5

Copper rest

[RF patent No. 2349659, declared. 08.08.2007, reg. Application No. 2007130466/02, publ. 03/20/2009, bull. No. 8, authors: Efimov V.N., Mamonov S.N., Yeltsin S.I., Shulgin D.R.]

This alloy is adopted as a prototype.

The prototype alloy can be used in the manufacture of jewelry of both 900 and 950 samples, it has a beautiful white color with gloss, resembles platinum, is well polished and has relatively high consumer qualities, especially when used for microfusion casting. The main disadvantages of this alloy include:

- the impossibility of its use in the manufacture of products 990 samples;

- insufficient stability of the physicomechanical properties of semi-finished products (rods and wires) obtained from this alloy by plastic deformation methods, which reduces the yield when used for the manufacture of chains by machine method.

The task to which the proposed technical solution is directed is to develop the composition of a white-colored jewelry alloy based on palladium, which allows it to be used in the manufacture of high-quality products up to 990 samples, using methods such as investment casting and plastic deformation in the manufacture of chains, including machine method.

The technical result is achieved by the fact that a white palladium-based jewelry alloy containing cobalt, iridium and copper additionally contains silver and iron in the following ratio of components, wt.%:

Palladium 95.0-99.5 Cobalt 0.2-3.0 Iridium 0.05-0.6 Silver 0.1-1.5 Iron 0.05-0.6 Copper rest

Common to the known and claimed jewelry alloys based on palladium is the presence in the alloy of cobalt, iridium and copper.

The palladium content in the alloy is due to the required fineness for high-grade jewelry (990 samples or 950 samples).

The introduction of silver and iron into the alloy within the stated concentration limits, in combination with palladium, cobalt, iridium and copper, provides the alloy with a beautiful white color, sufficient strength for jewelry, structural stability and physical and mechanical characteristics both along the length of the wire being made and along its cross section, which allows the use of this alloy for the manufacture of chains, including using chain knitting machines.

The inclusion of additional alloying components in the alloy leads to an improvement in its structure, which is formed during crystallization of the melt, subsequent heat treatment and plastic deformation, which increases its technological properties when used for manufacturing chains. Exceeding the silver content of more than 1.5% in the inventive alloy is undesirable, since it leads to an increase in the gas porosity of the alloy and, consequently, to an increase in marriage in the manufacture of jewelry.

A decrease in the silver content in the alloy below 0.1% is undesirable, since it leads to an increase in the “liquidus” temperature and an extension of the crystallization interval of the alloy, deterioration of its casting properties.

The addition of iron to the alloy within the stated limits, along with the addition of iridium, ensures the formation of a homogeneous fine-grained structure and increases the strength characteristics of the alloy.

An increase in the iron content in the alloy above 0.6% is impractical, since it leads to a decrease in the corrosion resistance of products and worsens their appearance.

The copper content in the alloy in the declared amount is optimal, since it reduces the melting point of the alloy, reduces the crystallization interval and, in combination with the stated amounts of the remaining components, provides a jewelry alloy with the required consumer qualities.

Example 1 - (preparation of alloy 990 samples)

The preparation of a white jewelry alloy based on palladium 990 was carried out by direct fusion of pure components, namely: bullion-refined palladium (purity 99.95%); powder-refined iridium (99.95% pure); silver granules (99.95% pure); cobalt in the plates, grade K-0; copper in granules, grade M0; iron powder, grade ПЖВ-1.

In a melting crucible made of zirconium dioxide of the induction vacuum unit UIPV-63-10-0.01 of the RELTEC company, a charge composed of the calculated amount of components was loaded, namely: palladium - 4000.0 g; iridium - 2.9 g; silver - 8.0 g; cobalt - 12.5 g; copper - 5.0 g; iron - 4.5 g.

The installation was evacuated to a residual pressure of 60 Pa and then filled with an inert gas, argon. The mixture was melted in argon medium. After complete melting of the components, the obtained melt was held for 5 minutes and drained into a massive copper mold.

After cooling, an alloy ingot in the form of a squared bar weighing 4028.5 g (or 99.9% of the load) was removed from the mold.

After mechanical cleaning of the surface, the obtained ingot was tested, the sample was subjected to chemical analysis.

Chemical analysis of the sample showed that the resulting palladium-based jewelry alloy contains 99.21% palladium; 0.07% iridium; 0.20% silver; 0.30% cobalt; 0.10% iron, the rest is copper.

The obtained jewelry alloy based on palladium corresponds to the 990th test, has a white color with a tint reminiscent of platinum.

Example 2 - (preparation of alloy 950 samples)

The preparation of a white color jewelry alloy based on palladium 950 was carried out by direct fusion of pure components according to a procedure that does not differ from that described in example 1.

Into a melting crucible made of zirconia of an induction vacuum installation, a charge composed of the calculated amount of components was loaded, namely: palladium (99.95% pure) - 4000.0 g; powder iridium (99.95% purity) - 21.0 g; silver granules (99.95% pure) 42.1 g; cobalt in K-0 grade plates - 79.9 g; copper in M0 grade granules - 42.1 g; iron powder PZHV-1 - 21.0 g.

After melting the mixture in argon and draining the melt, an alloy ingot in the form of a rectangular bar weighing 4197.7 g (or 99.8% of the load) was removed from the copper mold.

Chemical analysis of the sample showed that the obtained palladium-based jewelry alloy contains 95.21% palladium; 0.40% iridium; 1.0% silver; 1.90% cobalt; 0.48% iron, the rest is copper.

Obtained in example 2, a jewelry alloy based on palladium corresponds to 950 samples.

Both alloys obtained in examples 1 and 2 were forged into square bars (15 × 15 mm). A wire intended for the manufacture of jewelry chains was made from rods by rolling and drawing. The manufactured wire was annealed on coils in a muffle furnace at a temperature of 800 ° C for 10 minutes.

Physico-mechanical characteristics of the manufactured wires are given in the table.

From the obtained wire samples on the Sisma chain knitting machine S2 / V (with argon-arc welding of a link), jewelry chains NTs 61-076 were made. Chains stably passed forging and diamond cutting operations

Claims (1)

A white palladium-based jewelry alloy containing cobalt, iridium, copper, characterized in that it additionally contains silver and iron in the following ratio, wt.%:
Palladium 95.0-99.5 Cobalt 0.2-3.0 Iridium 0.05-0.6 Silver 0.1-1.5 Iron 0.05-0.6 Copper rest