JPS5993872A - Au alloy member for decoration having surface hardened layer - Google Patents

Abstract

PURPOSE:To treat the surface-hardened layer of an Au alloy member for decoration to extremely high hardness by subjecting an Au alloy member having the compsn. contg. >=1 kinds among Cr, Ag and Cu and the balance substantially Au and base texture dispersed therein with proeutectic Cr to a nitriding treatment. CONSTITUTION:An Au alloy member is constituted of a compsn. contg., by wt%, 5-15% Cr, and 3-44% >=1 kinds of Ag and Cu, and contg. further 0.1-3.0 Al according to need and consisting of the balance Au with unavoidable impurities. Said member is requlated to consists of the texture dispersed uniformly with relatively coarse proeutectic Cr (crystallized in the process of solidification) and finely precipitated Cr (formed after the nitriding treatment) in the base. If the surface of the Au alloy member having such compsn. and texture is subjected to a nitriding treatment, more preferably an ion nitriding treatment, the Au alloy member having the surface hardened layer exhibiting extremely high hardness is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an Au alloy member having a surface hardening layer formed by nitriding, which has excellent surface hardness and is particularly suitable for use as ornaments such as rings and necklaces. .

As is well known, gold is the most chemically stable metal among all metals and can maintain a beautiful golden color for a long time.It is also physically extremely flexible, has excellent malleability among all metals, and is easy to work with. Gold and Au are easy to use.
Alloys have been widely used as decorative materials since ancient times.

Pure gold is extremely soft and easily damaged, so Ag
Au alloys such as so-called 18 and 14, which have been given appropriate hardness by adding Cu, etc., are generally used as decorative materials. However, it has the disadvantage of being easily scratched.

However, in recent years, Au alloy rings and necklaces with sharp patterns created by sharp cuts called the diamond cutting method have become popular, but because conventional Au alloys are soft, the edges wear out and the patterns become unclear. This is often a problem, and various attempts have been made to make Au alloys harder in order to overcome these problems.

When wearing an Au alloy as an ornament, in order to prevent scratches on its surface, the hardness of the Au alloy member must be normally I(v
(Vickers hardness): 350 or more, preferably 01.
l-1v: It is said that 500 or more is good (for example, the hardness of a watch dial is approximately) Iv:
500, if an Au alloy with Hv: 500 or more can be made, it will be possible to provide a hard ornamental Au alloy moon phase that will not scratch even this dial glass.

However, at present, even if various Au alloys are heat treated or work hardened, their hardness remains at most Hv: 300, making it difficult to develop Au alloys that meet the above requirements. The current situation is that it has not been successful.

Therefore, the present inventors conducted various studies in order to obtain Au alloy members with excellent surface hardness in the field of decorative phase materials.
-15%, one or two of Ag and Cu:
Contains 3 to 44%, and further contains ht:o, 1 as necessary.
~3.0% total content, with the remainder consisting of Au and unavoidable impurities, as well as relatively coarse primary Cr (crystallized during the solidification process) and fine precipitated Cr (formed after ion nitriding treatment). ) shall have a structure in which they are uniformly dispersed in the substrate,
In this case, primary Cr has Vickers hardness (Hv-):
The precipitated Cr has a Hv of 220, but does not have much effect on strengthening the substrate, while the precipitated Cr has an Hv of 130 (although it is not shown, it is extremely useful for strengthening the substrate, and has such a composition and structure. When the surface of the Au alloy member is subjected to nitriding treatment, preferably ion nitriding treatment, N that diffuses back into the surface mainly reacts with primary Cr to form nitrided Cr. In this case, the precipitated Cr is nitrided. The hardness of the base material part that has become Cr does not increase that much, and only shows Hv: about 150, but the part where primary Cr has become Cr nitride shows a significantly high hardness of Hv: about 350 to 600. As a result, we are waiting for the knowledge that an Au alloy member having an extremely hard surface hardened layer can be obtained.

This invention was made based on the above knowledge, and in weight%, Cr: 5 to 15%, Ag and C.
A composition containing 3 to 44% of one or two types of U, and further containing 0.1 to 3.0% of At as necessary, with the remainder consisting of Au and unavoidable impurities, and the base material. A surface of an Au alloy member having a structure in which primary Cr and precipitated Cr are dispersed, and a surface hardened layer in which Cr nitride, preferably Cr nitride formed by ion nitriding, is dispersed. It is characterized by a decorative Au alloy phase having a hardened layer.

Next, the reason why the composition range of the Au alloy member of the present invention is limited as described above will be explained.

(a) Cr A part of the Cr component crystallizes as relatively coarse primary Cr during solidification as described above, and this primary Cr is converted to nitrided Cr by the nitriding treatment performed in the subsequent process. In addition to increasing the hardness of the component surface and significantly improving wear resistance, some other components are precipitated as fine Cr precipitates through heat treatment, which has the effect of improving the strength of the component base. If the content is less than 5%, the crystallization of primary Cr is insufficient, and it is not possible to improve the surface hardness by nitriding (if primary Cr does not exist, Au does not form various oxides). Therefore, it is impossible to improve the surface hardness of the part by nitriding).On the other hand, if the content exceeds 15, the plastic workability will be poor, and the hardness cannot be improved by nitriding. The content was determined to be 5 to 15% since the content of carbon dioxide also becomes saturated.

(b) Ag and Cu These components have the effect of strengthening the entire circumference of the substrate by solid bathing it, but if the content of 3 is less than 3%, this effect cannot be obtained; on the other hand, if the content exceeds 44% If it is contained, the plastic workability will be inferior, so the total content should be 3 to 44%.
It was determined that

(c) Part of At forms an intermetallic compound with Au, which is uniformly and finely dispersed and precipitated in the substrate, increasing the hardness of the substrate, and the other At, which is dissolved in the substrate, is also dissolved during nitriding. It has the effect of forming AtN in a uniform and finely dispersed form in the hardened surface layer to further improve the surface hardness, so it may be included as necessary especially when even higher hardness is required. If the content exceeds 3.0%, the melting point of the Au alloy member will drop significantly by 7 (below 600°C). Since there is a concern that this member may melt during the ion nitriding process, the content of iyo was determined to be 1 to 3.0%.

The nitriding treatment, particularly the ionization treatment applied to the production of the Au alloy phase of the present invention, is carried out as follows. In other words, the material to be nitrided is placed as a cathode in a sealed container into which a mixed gas of N2 and N2 or NH3 gas is introduced so that the internal pressure is (!: 1,5~1 Torr). A voltage of 100-1500 V is applied between this cathode and a separately sealed anode to generate a glow discharge. As a result, the nitrogen in the atmosphere ionized by the discharge is released. When the ions collide with the object to be treated (@pole), the object to be treated is heated by the high kinetic energy of the ions, and ion nitridation of the surface of the material is achieved.

Next, the Au alloy member having surface hardening tbw of the present invention will be specifically explained according to an example.

Example '1' Using an IC arc, necessary additive metals and electrolytic Au') were melted in a copper water-cooled melting pot to produce an fcAu alloy bath having the respective compositions shown in Table 1: 10
After preparing 2, gold N was cast into a button ingot,
The surface of this ingot is polished to a size of 1 Oan'
1 wnf, and this test piece has 5 To
At f 1. , for those containing 0% or more, temperature = 6υ (10 o'clock filtration at 1°C)
l, and others, by performing ion nitriding treatment at a temperature of 830°C for 5 hours, the present invention A
U alloy members 1 to 17 and conventional Au alloy members 1 to 3 were manufactured, respectively.

Next, the maximum surface hardness of the various members obtained as a result was measured by micro-Vickers before and after the ion nitriding treatment. These measurement results are also shown in Table 1.

From the results shown in Table 1, it can be seen that the Au alloy part I31 of the present invention
- 17, the surface hardness was significantly improved by the nitriding treatment, and among them, the present invention Au composite materials 1 - 17
In contrast, the surface hardness of conventional Au alloy members 1.2 (alloy 18 and alloy 14) was improved even by the nitriding treatment. There is almost no change in hardness, and even in all conventional Au composite materials made of hard Au alloys, there is almost no improvement in hardness.

As mentioned above, the Au@-gold member of the present invention is particularly suitable for Au@-gold members of the present invention.
Due to the nitriding treatment of relatively coarse primary Cr'fc dispersed in the alloy matrix, it has a surface hardened layer of extremely hard dilated Cr, so when used as a decorative member that requires these properties. It exhibits excellent performance over an extremely long period of time.

Applicant: Mitsubishi Metals Corporation Agent Tomi 1) Kazuo and 1 other person

Claims (1)

[Claims] (Composition containing 11Cr: 5 to 15%, one of Ag and Cu or 21N: 3 to 44%, with the remainder consisting of Au and unavoidable impurities (the above type ■%)) , and a decorative Au alloy member having a surface hardened layer in which Cr nitride is dispersed on the surface of an Au alloy member having a structure in which primary crystal Cr and precipitated Cr are dispersed in the base material. f21 Cr: 5-15%, one or two of Ag and Cu = 3-44%, further ht: 0.1
-3.0%, the remainder is Au and unavoidable impurities (1% or more), and the surface of the Au alloy part has a structure in which primary Cr and precipitated Cr are dispersed in the base material. A decorative Au alloy member having a surface hardened layer, the surface hardened layer having Cr nitride dispersed therein.