JPH05311311A - Gold-colored sintered alloy - Google Patents

Abstract

PURPOSE:To produce a gold-colored sintered allot excellent in hardness, strength, corrosion resistance and sintering characteristics and having elegant gold color by preparing a sintered alloy having a specific composition where respective contents of carbon and chromium are specified. CONSTITUTION:This alloy is a sintered alloy having a composition consisting of, by weight, 55-70% titanium, 10-30% of iron group metals (Ni, Fe, Co, etc.) and the group VIa elements (Mo, W, etc.) of the periodic table including at least chromium, and the balance carbon and nitrogen. In this composition, the percentage of carbon in the total quantity is regulated to <=0.7wt.%, and also the percentage of chromium in the metallic elements excluding titanium is regulated to >=35wt.%. By this method, the lightness index L* in the L*a*b* color specification system specified by JIS Z 8730 is regulated to >=10 and also the chromaticness index a* and b* are regulated to <=+0.4 and >=+8.0, respectively, and the gold-colored sintered alloy excellent in chipping resistance, easy of sharp edge working, and having a clear and superior gold color tone can be obtained. This alloy can be used for a watchcase, etc.

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, pure gold, alloys thereof, various metals such as brass, or metal plated with gold on the metal surface has been used as a gold-colored material used for decoration. , All of them have low hardness, which easily causes scratches on the surface due to contact with a hard substance,
Alternatively, there is a defect that cracks or the like occur. Further, in order to prevent scratches on these surfaces, various metals and the like are coated with a golden hard coating, but these also have the drawback of peeling due to the weak film strength of the heterogeneous layer.

Therefore, in recent years, in order to solve the above-mentioned drawbacks, 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. ing. (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, there has been a problem that the color tone is remarkably changed from the original golden color of the sintered body by the addition of these various additives. In particular, in the addition of carbides and carbonitrides of elements of groups 4a, 5a and 6a of the Periodic Table, which are good for improving the sinterability, the color tone of the sintered body changes to red copper and is clear and good. There is a problem that a golden color cannot be obtained.

[0006] Further, as the amount of these additives added increases, shedding becomes more noticeable during grinding of the sintered body, and
There are also problems that voids (holes) in the sintered body are increased, which lowers the strength and hardness, and makes it difficult to obtain a mirror surface even after polishing.

Further, there has been a problem that, as the amount of the additive increases, for example, the corrosion resistance of human beings to sweat and seawater is lowered.

Further, these sintered bodies are inferior in chipping resistance, are susceptible to shedding or the like during decoration processing, and have a problem in that sharp edge processing is difficult.

[0009]

Means for Solving the Problems The inventors of the present invention have a sharp and good golden color tone, high strength and hardness, excellent corrosion resistance, excellent chipping resistance, and sharp edge processing. In order to obtain a good gold-colored sintered alloy that can be easily carried out, as a result of various studies, the ratio of carbon in the total amount was kept below a certain level, and the ratio of chromium in the sintered body was above a predetermined amount. By limiting the color difference of the sintered body to a predetermined value, it was found that the above effects can be obtained.

That is, in the gold-colored sintered alloy of the present invention, titanium is 55 to 70% by weight in the total amount, the iron group metal and the periodic table No. 6 are used.
A sintered alloy composed of an a-group element in an amount of 10 to 30% by weight and the balance of carbon and nitrogen, the carbon content in the entire amount being 0.7% by weight or less, and chromium in metal elements other than titanium. The proportion of which is 35% by weight or more,
Also, the lightness index L * ≧ 10 and the chromaticness index a in the L * a * b * color system specified in JISZ8730.
* ≦ + 0.4 and b * ≧ + 8.0. The iron group metals include Ni, Fe, and Co, the Group 6a elements of the periodic table include Cr, Mo, and W, and the nonmetallic elements include nitrogen and carbon.

And, the total amount of titanium is 55 to 70% by weight.
The reason is that if it is less than 55% by weight, the golden color tone becomes light, and if it exceeds 70% by weight, the sinterability is lowered and the strength is lowered. This amount is preferably 60 to 68% by weight. In addition, titanium in the sintered body,
It exists mainly as TiN or TiCN and forms a hard phase.

Further, the iron group metal and the Group 6a element of the periodic table are set to 10 to 30% by weight based on the total amount because if these amounts are less than 10% by weight, sintering tends to be difficult. This is because the strength of the sintered body decreases. On the other hand, if the amount is more than 30% by weight, the hardness of the sintered body is significantly reduced and the corrosion resistance is reduced.

The amount of iron group metal and Group 6a element of the periodic table is preferably 12 to 23% by weight. This iron group metal forms a binder phase in the sintered body, and
Group a elements form a hard phase or a bonded phase. Further, specifically, it is desirable that the iron group metal is present in an amount of 5 to 18% by weight and the Group 6a element of the periodic table is present in an amount of 3 to 12% by weight.

Further, the ratio of carbon in the total amount is 0.7
The reason why the amount is less than or equal to 0.7% by weight is that if the amount exceeds 0.7% by weight, the chromaticness index a * >> + 0.4, b * <+
It becomes 8.0, and in terms of color tone, the original golden color becomes reddish, and as the carbon ratio increases, it changes from red copper color to grayish brown. In particular, the chromaticness index a * is changed by changing the carbon ratio. Therefore, in order to maintain a clear and good golden color tone, the proportion of carbon in the total amount needs to be 0.7% by weight or less. In particular, the proportion of carbon in the total amount is preferably 0.5% by weight or less. In order to reduce the amount of carbon in the sintered body to 0.7% by weight or less, the addition of carbide in the raw material powder may be minimized, and when the addition of carbide is large, oxides such as TiO ₂ may be added. May be added to disperse the carbon in the carbide during firing.

The proportion of chromium in the metal elements other than titanium is set to 35% by weight or more. When it is less than 35% by weight, the sinterability is lowered and voids are easily generated in the sintered body. This is because during the processing such as grinding and polishing, graining becomes remarkable, the strength is lowered, and the corrosion resistance is also lowered. Also, the proportion of chromium is 35% by weight.
If it is less than L, the lightness index L in the L * a * b * color system is
It tends to be low. On the other hand, if the ratio of chromium to the binding metal in the sintered body is 35% by weight or more, the sinterability is improved and the above problems do not occur. This is considered to be because the addition of Cr improves the wettability between the hard phase and the binder phase. 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, titanium nitride and carbonitride powders with an iron group metal and a Group 6a element of the periodic table in an organic solvent such as acetone. After mixing and pulverizing for a predetermined time, a predetermined amount of a binder is added, and the mixture is molded into a desired shape by press molding, injection molding, extrusion molding or the like, and the binder is debindered at a temperature of 250 to 500 ° C. in a non-oxidizing atmosphere and then predetermined. It is obtained by firing at a temperature.

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, although it depends on the size of the sample. After firing, the surface of the sintered body is mirror-polished with a diamond paste or the like, whereby a glossy, clear and good gold color appears.

For example, titanium nitride and carbonitride having a particle diameter of 0.5 to 3.0 μm and an iron group metal having a particle diameter of 0.
1 to 1.0 μm of Ni or Co and Cr (Cr ₃ C ₂ ) having a grain size of 1.0 to 10.0 μm as a Group 6a element of the periodic table
, Mo (Mo ₂ C) and other powders are weighed and mixed, and this is mixed and ground in an organic solvent such as acetone for about 48 to 72 hours,
The desired shape is formed by press molding. The molded product is debindered at a predetermined temperature in a non-oxidizing atmosphere, and then vacuum fired at a predetermined temperature in a vacuum heating furnace for 0.5.
It is obtained by carrying out ~ 2.0 hours. Further, TiN and TiCN are preferably present as crystal particles having a particle size of 8 μm or less in the sintered body.

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

[0020]

[Example] TiN having a particle size of 2 μm as a raw material powder, a particle size of 2
μm TiCN, grain size 3 μm Cr, grain size 4 μm M
o, Ni powder having a particle size of 1 μm, Co powder having a particle size of 1 μm were used, and these powders were weighed and mixed so that the metal content of the final sintered body would be the ratio shown in Table 1, and this was mixed in an organic solvent such as acetone After mixing and pulverizing for about 68 hours, paraffin is added in an amount of 4 to 5% by weight, and pressure-molded to a desired shape at 1.5 ton / cm ² .
Molded product in a non-oxidizing atmosphere at a temperature of 300 ° C
After debindering at 1, vacuum firing was performed at 1450 ° C. for 1 hour in a vacuum heating furnace having a vacuum degree of 10 ⁻² torr. The composition analysis of the final sintered body thus obtained was carried out by ICP
The results are shown in Table 1.

[0021]

[Table 1]

Then, the sintered body was surface-ground and mirror-polished, and thereafter, the color tone, bending strength, Vickers hardness (Hv), chipping resistance and corrosion resistance of the sample were tested. The flexural strength was measured according to JIS R1601 three-point bending test method, the Vickers hardness was measured according to JIS Z2244 test method, and the corrosion resistance test was carried out using artificial sweat (pH 4.7) in accordance with ISO (International Organization for Standardization) standards. It was performed by immersing the lower half of the mirror-polished sample for 24 hours in artificial sweat used as a corrosive liquid and kept at a temperature of 40 ° C. ± 2 ° C., and observing the condition of the polished surface of the sample after the immersion.
Further, as a quantitative evaluation method of color tone, an L * a * b * optical color difference meter (manufactured by Minolta), that is, a high-performance color difference meter of 45 ° ring illumination vertical light receiving system (corresponding to JIS Z8722)
Was measured and evaluated. The chipping resistance was evaluated by the maximum chipping width when creep grinding was performed on the mirror-polished sample. The results are shown in Tables 2 and 3.

[0023]

[Table 2]

[0024]

[Table 3]

In Table 1, Table 2 and Table 3, the sample numbers marked with * indicate those outside the scope of the present invention. Regarding the results of the corrosion resistance test, the mark "○" shows no discoloration and corrosion, the mark "Δ" shows discoloration, and the mark "X" shows discoloration and corrosion. Regarding the chipping resistance, ◯ marks are good for sharp edge processing, Δ marks are not suitable for sharp edge processing because chipping of 1 to 5 μm width occurs in places, and × marks are large with 5 μm width or more. Shows that chipping is too frequent for sharp edge processing.

From Table 1, Table 2, and Table 3, the samples within the scope of the claims of the present invention are very excellent in bending strength, Vickers hardness, corrosion resistance, and chipping resistance, and have an elegant golden color. It turns out that it has.

[0027]

As described in detail above, according to the present invention, it has hardness and strength that do not cause any trouble in use, has excellent corrosion resistance, and has a graceful and clear golden color due to the remarkable improvement in sinterability. Mirror surface can be easily appeared, and sharp edge processing required for manufacturing can be easily performed. As a result, as a golden-colored sintered alloy with a beautiful color tone that does not cause corrosion or scratches for a long period of time, for example, a watch case or a watch. Band, necklace, brooch, pendant, commemorative medal,
It can be used for decorations such as buttons, fishing gear, scissors, blades, stamps, etc.

Claims (1)

[Claims] 1. A firing bond constituted by 55 to 70% by weight of titanium in total, 10 to 30% by weight of iron group metal and at least chromium in Group 6a of the periodic table, and the balance being carbon and nitrogen. Gold, wherein the proportion of carbon in the total amount is 0.7% by weight or less, the proportion of chromium in the metal elements other than titanium is 35% by weight or more, and J
Lightness index L * ≧ 10 and chromaticness index a * ≦ + in the L * a * b * color system specified in ISZ8730.
0.4, b * ≧ + 8.0, a gold-colored sintered alloy.