DE3826607A1 - Use of an improved palladium/white gold alloy for the manufacture of jewellery - Google Patents

Abstract

Published without abstract.

Description

The invention relates to the use of a gallium containing palladium-white gold alloy for decorative purposes. Palladium-containing white gold alloys are characterized by good Ductility, good color, good corrosion resistance and good Skin compatibility.

The disadvantage is the low hardness and associated bad Polishing, poor mechanical stability and reinforced Wear. In addition, the high melting range in jewelry casting disadvantageous.

By partial or complete replacement of palladium by Nickel hardness and strength are significantly increased. Indeed These nickel-white gold alloys tend to embrittle and a bad color.

Due to the nickel content of the alloy can be at appropriate sen sensitized persons may experience nickel allergy. especially because of the latter property is increasingly trying nickel to replace containing white gold.

By adding gallium to palladium white gold alloys nickel-free white gold alloys with good mechanical properties obtained both the usual palladium white gold and can also replace the nickel white gold and always improved egg show characteristics.

The gallium contents can vary depending on the required properties Range can be varied up to 5%.

Alloys with high gallium content are no longer deformable.  

For conventional gold alloys is preferably a gallium content used from 0.5 to 1.5%. For example, the following Legie recommended:

Gold | 75% palladium 19% copper 5% gallium 1%

The alloy can be white in the same way as ordinary palladium gold melted and processed.

The melting interval is (in comparison in a Ga-free Alloy):

Gallium causes a lowering of the melting interval. In Table 1, the mechanical values are as an example given alloy after various pretreatment listed. (Comparatively, again, the corresponding values of the gal liumfrei alloy indicated). The gallium-containing alloy be sits especially in the cast state and annealed a significantly hö here hardness than the comparative alloy, what its use for Making jewelry much easier.

Fig. 1 shows the dependence of the hardness on the degree of deformation (hardening curve) for the gallium-containing alloy and the comparative alloy. The hardening curves run parallel. That is, both alloys have the same (favorable) deformation behavior and differ only in the desired manner by the initial hardness (hardness in annealed condition). Fig. 2 shows typical recrystallization curves for alloys with 1%, 0.5% and 0% (comparison) gallium. Gallium increases the recrystallization temperature by about 100 to 150 ° C. This must be taken into account when processing the alloy. Depending on the desired hardness, a soft annealing temperature between 600 and 700 ° C is recommended. Alloys with 0.5 and 1% gallium give a similar recrystallization behavior, they differ only in the final hardness. Figures 3 to 6 show the structure of the alloy with 1% gallium and the gallium-free alloy in comparison. Gallium leads to nested, very fine-grained precipitates in the cast state ( Fig. 3). By stronger deformation and subsequent recrystallization annealing, the distribution of the second phase becomes more loosened ( Figure 5).

These excretions are obvious for the increase of Hardness and grain refinement are responsible, as well they improve the polishability and machinability with span lead off the proceedings.

As mentioned earlier, the properties of gallium can be understood containing white gold alloys by variation of the remaining Legie to a certain extent.

Fig. 7 shows the influence of the copper content on the hardness of 18 ct white gold with 1% gallium (condition annealed 700 ° C, 1h).

Table 1

Claims (5)

1. Use of a gold alloy as a jewelry alloy next to Contains gold (as the main constituent) and palladium, gallium. 2. In addition to the alloying elements according to claim 1, the Legie tion other ingredients such. Copper, silver and Zinc. 3. The alloys according to claim 1 and 2 are characterized characterized in that on nickel as a hardness increasing component can be waived. 4. The gallium content of the alloys according to claim 1 to 3 be usually less than 5%, preferably 0.5 to 1.5%. For an 18-carat white gold alloy, the following alloy is recommended as an example:
75% gold, 19% palladium, 5% copper, 1% gallium. 5. The alloys according to claims 1 to 4 are characterized characterized in that the gallium content is the strength and hardness of alloys (especially in soft annealed condition) increased.