JP2006225707A - Noble metal alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noble metal alloy which is used for ornaments such as a finger-ring and a brooch and tableware such as a spoon and a plate, and whose color tone is not changed, even when it is brought into contact with sweat, sulfide or the like for a long period of time, and in which, even when it is discolored, the discoloration is not conspicuous, and which has satisfactory workability as well. <P>SOLUTION: The noble metal alloy comprises, by mass, 10 to 75% Pd, 20.8 to 75% Au, and the balance Ag. According to this, the noble metal alloy in which, by the addition of Pd and Au to Ag, a silver color tone with a tinge of black is obtained, and, by the addition of Pd, excellent corrosion resistance can be obtained, thus the discoloration of Ag can be effectively suppressed, and, even when it is discolored to black, the discoloration is not conspicuous, and, by the addition of Au, excellent workability is imparted can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a noble metal alloy used for decorative items such as rings, brooches and necklaces, and tableware such as spoons and dishes.

  Conventionally, a silver alloy having a composition mainly composed of silver is widely known as a noble metal alloy used for decorations, tableware and the like. However, silver alloys are discolored easily when they come into contact with sweat, etc. during their use, or they react with trace amounts of sulfides in the air to form silver sulfide and discolor black. was there.

  Patent Document 1 below discloses an alloy containing 70 to 85% by weight of silver, 5 to 20% by weight of gold, 5 to 20% by weight of palladium, and 2 to 8% of copper as a silver alloy for preventing oxidation and sulfurization. A silver alloy characterized by comprising:

Further, Patent Document 2 below discloses an Ag—Pd—Au noble metal alloy material for jewelry including Pd 20 to 70 wt%, Au 0.1 to 20 wt%, and the balance Ag.
Japanese Patent Laid-Open No. 2001-20024 Japanese Patent Laid-Open No. 60-9844

  By the way, the color of the silver alloy can be changed not only by the original silver color but also by the component to be contained. For example, the color can be changed to light yellow or pink. However, the silver alloy exhibiting a relatively bright color tone as described above has a problem that when the color changes to black due to oxidation or sulfuration, the color change is easily noticeable.

  Moreover, although the silver alloy of the said patent document 1 is provided with oxidation resistance and sulfidation resistance, it cannot be said that it is enough, and it is difficult to prevent discoloration completely. Further, since the silver alloy contains copper in the silver fabric, for example, when a ring or the like is cast, copper is likely to be deposited on the surface of silver, and the color tone tends to be reddish or yellowish. From this point, it is difficult to say that the silver alloy of Patent Document 1 can completely prevent discoloration.

  Furthermore, the noble metal alloy material of Patent Document 2 has a problem in workability because it contains a relatively large amount of Pd but has a small content of Au.

  Therefore, the object of the present invention is that the color tone does not change even when contacted with sweat or sulfide for a long time, and even if the color changes, the color change will not be noticeable, and the workability is also good. It is to provide a noble metal alloy.

  In order to achieve the above object, the noble metal alloy of the present invention is characterized by comprising Pd: 10 to 75% by mass, Au: 20.8 to 75% by mass, and the balance: Ag.

  According to the noble metal alloy of the present invention, by adding Pd and Au to Ag, it is possible to obtain a blackish silver color tone with a slightly black hue of Pt, and more excellent by the addition of Pd. Therefore, even when used in contact with sweat for a long time, such as a ring or a necklace, discoloration of Ag can be effectively suppressed. Even if it changes to black, the precious metal alloy has a blackish silver tone, so the discoloration will not be noticeable, and the product value as a decorative item or tableware will be reduced without deteriorating the aesthetics. To prevent. If Au is not added, it is not preferable because the color tone becomes strong yellow. Moreover, since 20.8 to 75% by mass of Au having good ductility is added to the noble metal alloy of the present invention, superior workability can be obtained as compared with the noble metal alloy material of Patent Document 2. .

  Further, when it is necessary to braze, for example, a member for decoration, etc. using the noble metal alloy of the present invention, Au brazing can be used, thereby preventing discoloration from the brazed portion. It becomes possible. In the case where Ag wax is used, the color changes from that portion, which causes a problem.

  Furthermore, since the noble metal alloy of the present invention does not use any Ni or the like, which contributes to metal allergy, there is no possibility of adversely affecting the human body.

  Moreover, it is preferable that the noble metal alloy of this invention is used for a decorative article or tableware. That is, as described above, the noble metal alloy of the present invention effectively suppresses discoloration and does not stand out even when discolored, so it can be suitably used for decorative items worn directly on the skin such as rings and necklaces, Similarly, it can be suitably used for silver tableware in which discoloration due to food components becomes a problem.

  According to the noble metal alloy of the present invention, by adding Pd and Au to Ag in a specific composition range, a blackish silver color tone is obtained, and by adding Pd, excellent corrosion resistance is obtained. Even when the color changes to black, the color change does not become conspicuous, and excellent workability can be obtained by adding Au.

  The noble metal alloy of the present invention is obtained by adding Pd and Au to Ag. For example, in addition to decorative items such as rings, necklaces, earrings, earrings, bracelets, brooches, tie pins, cufflinks, and belt buckles, It is used for tableware such as spoons and dishes.

  As the composition of the noble metal alloy, Pd is 10 to 75% by mass, preferably 20 to 54% by mass, Au is 20.8 to 75% by mass, preferably 20.8 to 41.7% by mass. The balance is made of Ag. However, it does not prevent the remainder from containing inevitable impurities. By setting it as such a composition, the noble metal alloy of this invention can be made into the blackish silver color tone of the hue which made Pt black a little.

  In the composition of the noble metal alloy, when Pd is less than 10% by mass, the corrosion resistance is poor, and therefore, discoloration is likely to occur, and when it exceeds 70% by mass, workability and castability are deteriorated. Similarly, if Au is less than 20.8% by mass, the workability is deteriorated, and if it exceeds 75% by mass, the color tone becomes yellowish and the color tone is not blackish, so discoloration is conspicuous. This is not preferable because the manufacturing cost increases.

  The noble metal alloy of the present invention can have a blackish silver color tone by adding Pd and Au to Ag in the above composition range as in the above composition. Since corrosiveness is obtained, discoloration of Ag can be effectively suppressed. Even if the discoloration is black due to corrosion or the like, the noble metal alloy has a blackish silver color tone, so the discoloration is conspicuous. This prevents loss of product value as a decorative item or tableware without impairing the beauty. Furthermore, since 20.8 to 75% by mass of Au is added, superior workability can be obtained as compared with the above-mentioned noble metal alloy material.

  For casting of the noble metal alloy of the present invention, a molten metal melted in a crucible is poured into a mold using, for example, a plaster type or phosphoric acid type mold made by the lost wax method. A general method such as casting can be employed. The noble metal alloy thus cast and molded into a predetermined shape according to the purpose of use is polished and commercialized as a decorative article or tableware as described above.

Examples 1-3
After blending Ag, Au, and Pd in the proportions shown in Table 1, casting and polishing were performed according to a conventional method to produce rings of Examples 1 to 3.

Comparative Example 1
A ring of Comparative Example 1 was produced under the same conditions as in the Examples except that Au, Pd, and Pt were blended in the proportions shown in Table 1.

Comparative Example 2
A ring of Comparative Example 2 was produced under the same conditions as in the Example except that Au, Pd, and Pt were blended in the proportions shown in Table 1.

Comparative Example 3
A ring of Comparative Example 3 was produced under the same conditions as in the Example except that Au and Pt were blended in the proportions shown in Table 1.

Comparative Example 4
A ring of Comparative Example 4 was produced under the same conditions as in the Examples except that Ag and Pd were blended in the proportions shown in Table 1.

Comparative Example 5
A ring of Comparative Example 5 was produced under the same conditions as in the Example except that Ag, Au, Pd, and Cu were blended at the ratio shown in Table 1.

Test Example For the rings of Examples 1 to 3 and Comparative Examples 1 to 5, a visual color tone confirmation test and a color change test using artificial sweat were performed. The results are summarized in Table 1.

In addition, the discoloration test by artificial sweat was performed by immersing it in artificially synthesized sweat used for testing for 10 hours in the watch and precious metal industries to check for corrosion.

  From the results in Table 1, it can be seen that in Examples 1 to 3, it has a blackish silver color tone and no discoloration is observed, and it is suitable as a noble metal alloy used for decorations, tableware and the like. Understandable.

  In the case of Comparative Examples 1 and 2, although it exhibits a blackish silver color tone, since it contains Pt, the manufacturing cost increases. In addition, although the comparative example 3 does not discolor, since the main component is Pt, a manufacturing cost also increases in this case. Moreover, in the case of the comparative example 4, since it changed color a little and was also a silver color tone, the discoloration was conspicuous. Furthermore, in the case of the comparative example 5, since the color tone becomes yellowish silver, the texture is inferior and the color is slightly changed.

  The present invention does not change its color tone even when it is in contact with sweat, sulfides, etc. for a long time, and even if it changes color, the color change will not be noticeable and should be used as a noble metal alloy with good workability. Can do.

Claims (2)

  A noble metal alloy comprising Pd: 10 to 75 mass%, Au: 20.8 to 75 mass%, and the balance: Ag. The noble metal alloy according to claim 1, which is used for decoration or tableware.