JPH06192811A - Black precious metal alloy and method for producing the same - Google Patents

Abstract

(57) [Summary] [Structure] A black noble metal alloy obtained by heat-treating a noble metal alloy containing 10 to 75% by weight of a rare earth element in a hydrogen atmosphere at a temperature of 200 ° C or higher. [Effects] According to the present invention, it is possible to obtain a noble metal alloy exhibiting a black color, which has heretofore been unavailable. Also,
According to the present invention, since blackening progresses not only on the surface but also inside, a robust blackened product can be obtained. Further, in the present invention, black Au powder can be obtained and can be used as a forming raw material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black precious metal alloy and a method for producing the same. The black alloy of the present invention is particularly useful as a decorative material.

[0002]

2. Description of the Related Art Various noble metal colored alloys have been proposed in order to impart a variety of color tones to precious metal ornaments. As a colored alloy of such precious metals, A called a carat gold alloy
The u-Ag-Cu alloy and the Au-Ag-Cu-Zn alloy are typical. Its color tone is centered on yellow,
Adds copper to give a reddish tint, and adds silver to impart a greenish tint.
There is also known a decorative alloy having a purple color obtained by adding Ni, Co or the like to an Au-Al intermetallic compound and sintering the mixture by a powder metallurgy method (Japanese Patent Laid-Open No. 62-240729). However, no black precious metal alloy is known.

In addition, as a method of imparting a color tone other than the original color to the noble metal, a method of coating the surface of the noble metal with the other metal, a method of coating the surface of the other metal with the noble metal, and an alloy containing a specific metal are used. A method of performing a chemical treatment to form a colored surface layer is also known. Among them, the method of coating does not give a black color. As a method of chemically treating the alloy to blacken its surface, an alloy containing Au as a main component and containing at least one of Cr, Cu and Fe in an amount of 15 to 40% by weight is used as a raw material, and nitrosulfurization is performed. A method of forming a surface layer of a nitride or sulfide of Cr, Cu or Fe by the method (Japanese Patent Laid-Open No. 62-60856) is known, but since the thickness of the black layer is limited, the workability is improved. There is a problem with the durability of coloring. It is also necessary to remove bath components from the resulting blackened product. For this reason, there has been a demand for a precious metal alloy that retains the quality and features of a precious metal and exhibits a black color with excellent workability and durability.

[0004]

[Knowledge to Solve the Problem] In the process of studying the characteristics of the alloy of a noble metal and a rare earth element, the present inventors surprisingly applied a hydrogenation treatment to a noble metal alloy containing a rare earth element in a specific range of amount. Then, it was found that an alloy having a black color was obtained, and based on this finding, the present invention for solving the above problems was completed. It is considered that this blackening of the noble metal alloy is caused by hydrogenation of the rare earth element contained in the alloy.

[0005]

The present invention provides a black noble metal alloy obtained by heat-treating a noble metal alloy containing 10 to 75% by weight of a rare earth element in a hydrogen atmosphere at a temperature of 200 ° C. or higher.

Further, according to the present invention, the rare earth element is added in the range of 10 to 75.
A noble metal alloy containing 100% by weight is used under a hydrogen atmosphere for 200
Provided is a method for producing a black precious metal alloy, which comprises heating at a temperature of ℃ or higher.

The kind of rare earth element used in the present invention is not particularly limited. A plurality of rare earth elements may be used in combination. The content of rare earth is 10 to 75% by weight. With the increase of the rare earth content, the original color of the metal changes to silver gray or black, and the rare earth element content becomes black in the range of 10 wt% or more. In addition, the rate of hydrogenation increases as the rare earth element content increases. Blackening may occur even if it exceeds 75% by weight, but the meaning as a precious metal material is lost. For the purpose of a black alloy, the rare earth content is 10% by weight or more, preferably 60% by weight or less.

The noble metal elements used in the present invention are Au, A
g and platinum group elements. These may be used alone or as an alloy.

The blackening of the present invention is carried out by melting a noble metal and a predetermined amount of a rare earth element to form an alloy, and heat-treating the alloy in a stream containing hydrogen gas at a temperature of 200 ° C. or higher. The raw material metal can be dissolved according to a conventional method. Such methods include arc melting, plasma melting, vacuum melting, electron beam melting and the like. The conditions for dissolution may be any as long as they do not hinder the subsequent hydrogen introduction. The heat treatment time and the hydrogen gas concentration in introducing hydrogen are related to each other. These conditions are
It can be appropriately selected in consideration of the conditions such as the treatment temperature and the reactor. The treatment temperature is 200 ° C. or higher, preferably 300 to 500 ° C. When the temperature is low, the reaction takes a long time, and when the temperature is high, the reaction is rapid, which makes it difficult to control the reaction. If the other conditions are the same, the blackening proceeds to the inside as the processing time increases. When a powdered alloy is used as a raw material alloy and blackening is promoted, a black Au powder can be finally obtained.

[0010]

According to the present invention, it is possible to obtain a noble metal alloy exhibiting a black color which has heretofore been unavailable. Further, according to the present invention, since blackening progresses not only on the surface but also inside, a robust blackened product can be obtained.
Furthermore, in the present invention, black Au powder can be obtained and can be used as a forming raw material.

[0011]

[Detailed Disclosure of the Invention]

Example 1 25 g of Tb and 25 g of Au were melted in an arc melting furnace under an inert gas atmosphere to form a 50 wt% Tb-Au alloy. After cooling, this is molded into a test piece,
Hydrogenation was carried out under a temperature condition of 0 ° C. for 3 hours in a 100% hydrogen gas stream. The obtained test piece had a black color. Using the same test piece, hydrogenation was performed at different times, the test piece was cut, and the cross section was observed. As a result, it was observed that blackening progressed inward as time passed.

Examples 2 to 6 and Comparative Example Alloys having the compositions shown in Table 1 were melted in an arc melting furnace and subjected to hydrogen treatment under the processing conditions shown in the table. Except for the comparative example, a deep black alloy was obtained.

[0013]

[Table 1]

Claims (2)

[Claims] 1. A black noble metal alloy obtained by heat-treating a noble metal alloy containing 10 to 75% by weight of a rare earth element in a hydrogen atmosphere at a temperature of 200 ° C. or higher. 2. A method for producing a black noble metal alloy, which comprises heat-treating a noble metal alloy containing 10 to 75% by weight of a rare earth element in a hydrogen atmosphere at a temperature of 200 ° C. or higher.