JPH05285674A - Method for joining titanium or titanium alloy and gold alloy - Google Patents

Abstract

PURPOSE:To provide a joined body having the high strength of titanium or titanium alloy and gold alloy, high corrosion resistance and nice beauty by making combination use of direct diffusion joining and indirect diffusion joining. CONSTITUTION:An insert metal and the gold alloy are inserted into the recessed part of the titanium or titanium alloy and the part where the beauty is required is subjected to the direct diffusion joining and the part where the beauty is not required is subjected to the indirect diffusion joining. The execution of the joining at the temp. below the m.p. of the insert metal and lower by 50 to 400 deg.C than the m.p. of the gold alloy is preferred in terms of the strength and beauty. The use of the gold alloys, such as Ti-Cu-Ni and Ti-Cu-Ni-Zr, having the m.p. lower than the m.p. of the joined body as the inserted metal is more preferred in terms of the strength and corrosion resistance. As a result, the joined body having the high strength and the good corrosion resistance is obtd. without melting the joint surfaces of the titanium or titanium alloy and without impairing the beauty.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining method for joining a gold alloy to titanium or a titanium alloy, and more particularly to a joining method suitable for joining exterior parts for watches or ornaments.

[0002]

2. Description of the Related Art In recent years, titanium or titanium alloys, which have superior characteristics to stainless steel in terms of corrosion resistance, strength, lightness, and biocompatibility, have been used for exterior parts and ornaments for watches. The decoration of gold alloy has been attempted to be joined via a brazing material. In addition, direct diffusion bonding of titanium or titanium alloy and gold alloy or diffusion bonding via an insert metal has been attempted.

[0003]

However, in the case of joining titanium or a titanium alloy through a brazing filler metal of a gold alloy, since the brazing filler metal is heated to a melting temperature, the molten brazing filler metal is heated to titanium or titanium alloy during heating. Reacts violently with the gold alloy to soften or melt the joint interface, causing shape change and discoloration, and spoiling the aesthetics important as an ornament. Further, some brazing materials have a problem in corrosion resistance, and often have strength deterioration or discoloration.

When titanium or a titanium alloy and a gold alloy are directly bonded, the strength is insufficient when the bonding is performed only in the direction in which a load is applied and the bonding area is small. When diffusion bonding is performed through the insert metal, there may be a problem in appearance.

[0005]

In order to solve the above problems, the present invention directly diffuses titanium or a titanium alloy and a gold alloy in a portion where appearance is a problem, and in a portion where appearance is not a problem, Diffusion bonding was performed through the insert metal. The temperature of the diffusion bonding is lower than the melting point of the insert metal and lower than the melting point of the gold alloy by 50 ° C to 400 ° C.

Ti-Cu-Ni as an insert metal,
A gold alloy having a melting point lower than that of Ti-Cu-Ni-Zr or a gold alloy which is a bonded body is used. Further, when the titanium alloy is joined in a state where the crystal grain size is 10 μm or less, the titanium alloy is deformed with a low stress due to the superplastic phenomenon, and the contact area with the gold alloy can be increased.

[0007]

According to the above method, titanium or titanium alloy and gold alloy are joined in a solid state, so that the joining interface is not melted and shape change or discoloration does not occur. Moreover, Ti-Cu-Ni and Ti-Cu-Ni-Z are used as insert metals.
By using r or a gold alloy having a melting point lower than that of the gold alloy that is the bonded body, bonding can be performed even on a bonding surface to which almost no load is applied.

[0008]

EXAMPLES Examples of the present invention will be specifically described below. As an example, three types of titanium alloys, Ti-9.5V-2.5Mo-3Al Ti-4Al-3V-2Mo-2Fe pure titanium (JIS class 2), and Au-15Ag-10Cu diffusion alloy were tried as a gold alloy. It was

FIG. 1 is a schematic sectional view before diffusion, in which a recess is provided in titanium or titanium alloy 1, and an insert metal 3 and a gold alloy 2 are inserted into the recess. In this state, in a vacuum atmosphere, the bonding temperature is 500, 600, 750, 830, 850.
After holding for 5 minutes at ℃, it was cooled and joined. In this case, the coefficient of thermal expansion of the gold alloy is 15 × 10 ⁻⁶ / ° C., and the coefficient of thermal expansion of titanium is 9 × 10 ⁻⁶ / ° C., so the difference in thermal expansion causes the side surface of the concave portion of the titanium or titanium alloy 1 to differ. Then, stress is generated on the side surface of the gold alloy 2 and direct diffusion bonding is performed.

On the other hand, on the bottom surface, although the stress generation due to the difference in thermal expansion is slight, the insert metal (Ti-20C
u-20Ni, Ti-20Cu-20Ni-20Zr,
Au-14.5Ag-14.5Cu-10.7Zn-2
Due to the softening of In), diffusion bonding was also performed on the bottom surface via the insert metal. Diffusion occurs on most of the sides and bottom, and they are joined together.

FIG. 2 is a schematic cross-sectional view in which the diffusion layer is softened. At any joining material at a joining temperature of 850 ° C., the diffusion layer 4 is softened at the interface between titanium or titanium alloy and gold alloy, and the appearance is poor. It is an example that became. That is, this is an example in which the bonding temperature is too high. Insert metal is Ti
In the case of -20Cu-20Ni, no softened part was observed even at 830 ° C., and Ti-20Cu-20Ni-20Zr
In the case of, no softened part was observed at 800 ° C or lower, and Au-1
In the case of 4.5Ag-14.5Cu-10.7Zn-2In, no softened part was observed at 750 ° C or lower. As a result of the corrosion resistance test with artificial sweat and the corrosion resistance test with salt spray, complete corrosion resistance was shown.

FIG. 3 shows an example in which a titanium or titanium alloy and a gold alloy are directly diffusion-bonded only by thermal expansion without using an insert metal in a conventional example. The bonding temperature is 5
It was set to 00 ° C, 600 ° C, 750 ° C, 830 ° C, and 850 ° C. At the joining temperature of 850 ° C., the joining portion softened and the shape changed, but at 830 ° C. or less, the shape did not change. However, since the diffusion bonding portion is only on the side surface and the bottom surface is not bonded, the strength is low and it is not practical.

Next, Ti-9.5V-2.5Mo-3A
In A, the crystal grain size is 10 μm or less
An attempt was made to join u-15Ag-10Cu with the arrangement shown in FIG. Ti-20Cu-20Ni was used for the insert material, and it heated at 725 degreeC. At 725 ° C., fine crystal grains of Ti-9.5V-2.5Mo-3Al cause a superplastic phenomenon and are easily deformed even with a small stress.

Therefore, even if there are large undulations or irregularities on the joint surface, the difference in stress generated by the difference in thermal expansion easily allows Ti-9.5V-2.5Mo-3Al and Au.
The contact surface of -15Ag-10Cu easily contacted and diffusion bonding was performed. As described above, when embedding a gold alloy in titanium or titanium alloy,
Ti-20Cu-20Ni, Ti-20Cu-20Ni
It was found that diffusion bonding is performed through -20Zr and a gold alloy having a melting point lower than that of the gold alloy of the bonded body, and direct bonding is effective in terms of strength, appearance, and corrosion resistance in a portion having a problem in appearance.

FIG. 4 is a cross-sectional view in which a titanium alloy watch case 5 according to the present invention is decorated with a gold alloy 2. Titanium alloy watch case 5 is provided with a recess, insert metal 3 (Ti-20Cu-20Ni) and gold alloy 2 are inserted into the recess, and diffusion bonding is carried out by holding for 5 minutes at a bonding temperature of 750 ° C. in a vacuum atmosphere. It was As a result, the titanium alloy and the gold alloy were directly diffusion-bonded on the side surface and were diffusion-bonded on the bottom surface via Ti-20Cu-20Ni to obtain high strength. The appearance of the watch case was good with no deformation and no discoloration. In addition, complete corrosion resistance was obtained by a corrosion resistance test using artificial sweat and salt spray.

Diffusion bonding of titanium or titanium alloy and gold alloy is largely due to mutual diffusion of titanium and gold at the bonding interface, and the same can be said for titanium alloys and gold alloys other than the examples.

[0017]

As described above, according to the present invention, since the joining surface of titanium or titanium alloy is not melted, it is possible to obtain a joined body having high corrosion resistance without spoiling the appearance.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of the present invention before diffusion.

FIG. 2 is a schematic cross-sectional view in which a diffusion layer is softened.

FIG. 3 is a schematic cross-sectional view of a joined conventional example.

FIG. 4 is a cross-sectional view in which a gold alloy is diffusion-bonded to a titanium alloy watch case according to the present invention.

[Explanation of symbols]

 1 Titanium or titanium alloy 2 Gold alloy 3 Insert metal 4 Diffusion layer 5 Titanium alloy watch case

Claims (3)

[Claims] 1. A step of preparing titanium or a titanium alloy having a concave portion, a step of placing an insert metal on a bottom surface of the concave portion, and a step of finishing on the insert metal so as to contact a side surface of the concave portion. The step of inserting the gold alloy, and the titanium or titanium alloy in which the gold alloy is inserted, lower than the melting point of the insert metal, and 50 ° C.
A method for joining titanium or a titanium alloy and a gold alloy, which comprises the step of cooling in a vacuum atmosphere at a low temperature of 00 ° C. and then cooling. 2. The insert metal is Ti—Cu—Ni.
Alternatively, Ti-Cu-Ni-Zr or a gold alloy having a melting point lower than that of the gold alloy is used, and the method for joining titanium or titanium alloy and the gold alloy according to claim 1. 3. The method of joining titanium or a titanium alloy and a gold alloy according to claim 1, wherein the crystal grain size of the titanium alloy is 10 μm or less.