JPH059643A - Golden sintered alloy - Google Patents

Abstract

PURPOSE:To produce a satisfactory golden sintered alloy having high strength, high hardness and excellent corrosion resistance by blending specified percentages of Ti, Fe family metals, group VIa elements of the periodic table including Cr and nonmetallic elements. CONSTITUTION:A sintered compact of an alloy consisting of 55-75wt.% Ti, 3-29wt.% Fe family metals (Ni, Fe and Co) and group VIa elements (Cr, Mo and W) of the periodic table including at least Cr and the balance nonmetallic elements (C and N) is prepd. In the alloy, Cr accounts for >=40wt.% of the total amt. of the metallic elements except Ti. In the sintered body, Ti is chiefly in existence as TiN or TiCN and forms a hard phase. A golden sintered alloy having a fine color tone and not causing corrosion and scratch over a long period of time is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gold-colored sintered alloy having a gold color used for decoration, for example.

[0002]

2. Description of the Related Art Conventionally, for example, as a gold-colored material used for decoration, pure gold, alloys thereof, various metals such as brass, or a metal surface plated with gold has been used. All of them have a low hardness, and as a result, they are liable to be scratched or cracked on the surface due to contact with a hard substance.

Therefore, in recent years, in order to solve the above-mentioned disadvantages, a metal-nitride, for example, a gold-colored sintered alloy in which titanium nitride or the like is bonded with a metal such as Ni or Co has come to be used. (See Japanese Patent Publication No. 2-58335, etc.).

By the way, since the above-mentioned gold-colored sintered alloys generally have poor sinterability, in order to improve such sinterability, carbides and carbonitrides of elements of Groups 4a, 5a and 6a of the periodic table are improved. It was necessary to add various additives such as a product and calcinate.

[0005]

However, as the amount of these additives added increases, grain breakage becomes more noticeable during cutting of the sintered body, and voids (holes) in the sintered body also increase. , This reduces strength and hardness,
There was a problem that it was difficult to obtain a mirror surface even after polishing. Furthermore, there has been a problem that, as the amount of the additive increases, for example, the corrosion resistance of humans to sweat and seawater decreases.

[0006]

[Means for Solving the Problems] The inventors of the present invention have conducted various studies to obtain a good gold-colored sintered alloy having high strength and hardness and excellent corrosion resistance, and as a result, various additives as a binding metal have been obtained. It has been found that the above effects can be obtained by limiting the addition amount of the alloy to a predetermined amount and setting the proportion of chromium in the sintered body to a predetermined amount or more.

That is, in the gold-colored sintered alloy of the present invention, titanium is 55 to 75% by weight in total, iron group metal and Group 6a element of the Periodic Table containing at least chromium is 3 to 29% by weight, and the balance is. It is composed of non-metallic elements and the proportion of chromium in metallic elements other than titanium is 40%.
It is to be more than weight%. Here, the iron group metals include Ni and Fe and Co, the Group 6a elements of the periodic table include Cr, Mo, and W, and the nonmetallic elements include carbon and nitrogen.

Further, the reason why Ti is 55 to 75% by weight in the total amount is that if the amount is less than 55% by weight, the color tone of the golden color becomes gradually lighter, and if it exceeds 75% by weight, the sinterability decreases, This is because the strength is reduced. This amount is 60 ~
It is preferably 75% by weight. Incidentally, Ti mainly exists as TiN or TiCN in the sintered body and forms a hard phase.

The reason why the Group 6a element of the Periodic Table containing iron group metal and Cr is 3 to 29% by weight is that if the amount of these elements is less than 3% by weight, sintering tends to be difficult. This is also because the strength of the sintered body decreases. On the other hand, when it is more than 29% by weight, the hardness of the sintered body is remarkably lowered and the corrosion resistance is lowered.
In addition, the periodic table 6a containing an iron group metal such as Ni and Cr
The amount of the group element is preferably 10 to 25% by weight. The iron group metal forms a binder phase in the sintered body, and the element of Group 6a of the periodic table containing Cr forms the hard phase or the binder phase.

The proportion of chromium in the metal elements other than titanium is set to 40% by weight or more. If the proportion is less than 40% by weight, voids are likely to occur in the sintered body, which causes grinding, polishing, etc. This is because shedding occurs remarkably at the time of processing, the strength is lowered, and the corrosion resistance is also lowered. On the other hand, the ratio of Cr to the binder metal in the sintered body is 4
This is because if it is 0% by weight or more, the sinterability is improved and the above problems do not occur. This is due to the addition of Cr
It is considered that the wettability between the hard phase and the binder phase is improved. The balance contains a small amount of unavoidable impurities.

The gold-colored sintered alloy of the present invention is obtained by mixing, as a raw material powder, Ti nitride and carbonitride powder with an iron group metal such as Ni and a metal element of Group 6a of the periodic table containing Cr. Is mixed and pulverized in an organic solvent such as acetone for a predetermined time, and then a predetermined amount of a binder is added thereto, and the mixture is pressure-molded into a desired shape at a predetermined pressure, which is debindered at a predetermined temperature in a non-oxidizing atmosphere, It is obtained by firing at a temperature. For example, the particle size is 0.5 to 3.0 μm
Ti nitride and carbonitride, iron group metal having a grain size of 0.1 to 1.0 μm, Ni and Co, and Cr containing a group 6a element having a grain size of 1.0 to 10.0 μm WC
Powders such as Cr and C ₃ C ₂ are weighed and mixed, and this is mixed and ground in an organic solvent such as acetone for about 68 hours, paraffin is added, and pressure molding is performed at 1.5 ton / cm ² into a desired shape. It is obtained by debinding the molded product at a predetermined temperature in a non-oxidizing atmosphere, and then performing vacuum firing at a predetermined temperature for 1 hour in a vacuum heating furnace. At this time, W and Cr are added as raw material powders as carbides and melted in the binder metal as metal Cr and metal W or solid-dissolved in TiN or TiCN to form Cr ₃ C in the process of firing.
Not present in ₂ . Further, TiN and TiCN are preferably present as crystal particles having a particle size of 10 μm or less.

As a firing method, the degree of vacuum is 10 ^-1 to 10 ^-4.
Firing is performed at a temperature of 1300 to 1800 ° C. under reduced pressure or no pressure in a torr atmosphere or various atmospheres. The firing time is usually 0.5 to 5 hours, depending on the size of the sample. Then, after firing, the surface of the sintered body is mirror-polished with diamond paste or the like, whereby a glossy gold color appears.

The gold-colored sintered alloy thus obtained is
For example, it can be used for decoration of watch cases, watch bands, necklaces, broaches, commemorative medals, buttons, scissors, blades, fishing tackle, and the like.

[0014]

EXAMPLES T having a particle size of 0.5 to 3.0 μm as a raw material powder
iN, TiCN with a particle size of 0.5 to 3.0 μm, particle size of 1.0
~ 10.0 μm Cr ₃ C ₂ , grain size 1.0 to 10.0 μ
m WC, grain size 0.1-1.0 μm Ni, grain size 0.1
.About.1.0 .mu.m Co powders were used, and these were weighed and mixed so that the respective metal amounts of the final sintered body were in the ratios shown in Table 1, and were mixed and pulverized in an organic solvent such as acetone for about 68 hours. After that, paraffin is added in an amount of 4 to 5% by weight, and pressure molding is performed at 1.5 ton / cm ² into a desired shape. The molded product is debindered at a predetermined temperature in a non-oxidizing atmosphere and then heated in a vacuum heating furnace having a vacuum degree of 10 ^-2 torr at a temperature of 1400 to 150.
Vacuum baking was performed at 0 ° C. for 1 hour. The final sintered body thus obtained was analyzed by ICP emission spectroscopy and the results are shown in Table 1.

[0015]

[Table 1]

Then, the sintered body was surface-ground and mirror-polished, after which the color tone, bending strength, Vickers hardness (Hv), porosity and corrosion resistance of the sample were tested. The bending strength was measured according to JIS R1601 three-point bending test method, and the Vickers hardness was measured according to JIS Z2244 test method.
The porosity was according to the Archimedes method. For the corrosion resistance test, artificial sweat (pH 4.7) conforming to the ISO (International Organization for Standardization) standards was used as the corrosive liquid, and the temperature was 4
The lower half of the mirror-polished sample was immersed in artificial sweat kept at 0 ° C. ± 2 ° C. for 24 hours, and the condition of the polished surface of the sample after immersion was observed. The results are shown in Table 2.

[0017]

[Table 2]

In Tables 1 and 2, sample numbers marked with * indicate those outside the scope of the present invention. Regarding the porosity in Table 2, ∘ indicates a highly dense body of less than 3%, Δ indicates a medium to dense body of 3 to 6%, and x indicates a low density of more than 6%. Regarding the results of the corrosion resistance test, the ○ marks show no discoloration and corrosion, and △
The mark indicates discoloration, and the cross indicates discoloration as well as corrosion.

As is clear from Table 2, the gold-colored sintered alloys of Sample Nos. 2, 4 to 7 and 9 not only have excellent corrosion resistance, but also show excellent hardness and strength that do not cause any problems in decorative applications. There is. It is considered that this is because the Cr element forms a solid solution in the binding metal during the firing process. Moreover, it was found that the sinterability of these gold-colored sintered alloys was remarkably improved and the workability of grinding and polishing was good, and that polishing of these resulted in the appearance of an elegant golden mirror surface.

On the other hand, the gold-colored sintered alloy of Sample No. 1 had a high porosity and was poorly sintered. Samples Nos. 8 and 12 were not high-density bodies, and shattering occurred during grinding and polishing, and a good mirror surface could not be obtained. Sample number 3,8,
No. 12 is inferior in corrosion resistance. In Sample Nos. 10 to 13, the hardness was low, and each had a dark golden color or a grayish white color, and neither was suitable as a golden sintered alloy.

[0021]

As described above in detail, according to the present invention, the hardness and the strength are not hindered in use, and
It has excellent corrosion resistance, and due to its remarkable improvement in sinterability, a graceful golden-colored mirror surface easily appears. As a result, as a gold-colored sintered alloy with a beautiful color tone that does not cause corrosion or scratches for a long period of time, for example, watch case, It can be used for decoration of watch bands, necklaces, brooches, commemorative medals, buttons, etc., and for blades, fishing gear, etc.

Claims (1)

Claims: 1. The total amount of titanium is 55 to 75% by weight, the group 6a element of the periodic table containing an iron group metal and at least chromium is 3 to 29% by weight, and the balance is a nonmetallic element. And a ratio of chromium in the metal elements other than titanium to 40% by weight or more.