JPH08157989A - Silver-colored sintered compact for ornamental parts - Google Patents

Abstract

PURPOSE: To obtain a silver-colored sintered compact capable of ensuring superior deflective strength, Vickers hardness and fracture toughness and capable of reducing the content of allergenic metals by firing at a low temp. of 1,300-1,600 deg.C. CONSTITUTION: This silver-colored sintered compact contains at least Ti, C and B as principal constituent elements. The amts. of Ti, B and C are 80-95wt.%, 3-12wt.% and 2-8wt.% of the total amt. of the three components, respectively. The Ti exists mainly as a TiC phase 1 and a TiB phase 2 and the content of allergenic metals is <=0.3wt.% of the total amt. of this sintered compact. At least one among V, Zr, Nb, Mo, Hf, Ta and W is preferably allowed to exist by 0.5-15.0 pts.wt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered body for decorative parts, and in particular, it is directly applied to human skin such as bracelets, piercings, earrings, eyeglass frames, exterior parts for watches and rings. The present invention relates to a silver-colored sintered body for decorative parts, which is preferably used for decorative parts that come into contact with.

[0002]

2. Description of the Related Art Conventionally, decorative properties such as exterior parts for watches are rich in corrosion resistance and high in scratch resistance.
Furthermore, it is required that the metallic luster lasts for a long time.
Then, as a material having an optimum metallic luster for such a decorative component, stainless steel or a metal carbide such as W
A sintered alloy in which C or TiC is bonded with a metal such as Ni or Co has been used.

However, although stainless steel is excellent in corrosion resistance, it is easily scratched due to its low hardness. On the other hand, a sintered alloy composed mainly of WC or TiC and combined with a metal element such as Ni or Co is sintered. Although there is no problem with the hardness of the body itself, it has the drawback of low corrosion resistance to human sweat and seawater.

On the other hand, recently, Ti using the characteristics of TiB ₂ , which is a boride of titanium, such as high hardness and corrosion resistance.
A B ₂ system sintered body has been developed and put into practical use (see, for example, Japanese Patent Publication No. 59-18458). This TiB ₂ -based sintered body has a bending strength of about 800 to 1000 MPa and a beakers hardness of about 18 to 24 GPa, showing excellent characteristics.

[0005]

However, in the TiB ₂ system sintered body as described above, 1600 to 2000 ° C.
However, there is a problem that the sinterability is low.

In the TiB ₂ system sintered body described above, N
Since it contained about 1% by weight of a metal binder phase such as i, Co, Cr, when used as a decorative part, there was a possibility that metal allergy might occur depending on the person.

The present invention has excellent characteristics such as high hardness and corrosion resistance which are almost the same as those of the TiB ₂ system sintered body, and 13
An object of the present invention is to provide a silver-colored sintered body for decorative parts, which can be fired at a low temperature of 00 to 1600 ° C. and can reduce the metal content that causes allergy.

[0008]

As a result of intensive studies for solving the above problems, the present inventor found that Ti was used as a raw material.
A material similar to that of the B ₂ system sintered body is used, and T is used as a crystal phase.
By mainly producing iC and TiB phases and setting the content of metal as an allergen source to 0.3% by weight or less, it has almost the same characteristics as the TiB ₂ system sintered body, and has a low temperature of 1300 to 1600 ° C. The present invention has been completed based on the finding that it can be baked in the above-mentioned manner, and further, the occurrence of allergy can be prevented.

That is, the silver-colored sintered body for decorative parts of the present invention is
Silver-colored sintering containing at least titanium, carbon, and boron as main constituent elements, with titanium being 80 to 95% by weight, boron being 3 to 12% by weight, and carbon being 2 to 8% by weight based on three components. In the body, the titanium is mainly Ti
It is present as a C phase and a TiB phase and has a metal content of 0.3% by weight or less in the total amount as an allergen source.

The silver-colored sintered body for decorative parts of the present invention is
A main component 100 having at least titanium, carbon, and boron as main constituent elements, and 80 to 95% by weight of titanium in the total amount, 3 to 12% by weight of boron in the total amount, and 2 to 8% by weight of carbon in the total amount based on three components. With respect to parts by weight, V, Zr, N
A silver-colored sintered body containing at least one selected from b, Mo, Hf, Ta, and W in a proportion of 0.5 to 15.0 parts by weight, in which TiC phase and TiB phase are present. The metal content of the allergic source that is present is 0.3% by weight or less based on the total amount.

Here, the reason why the elements in the sintered body are limited as described above will be explained.

First, the total amount of titanium based on the three components is 80-
The reason why the content is set to 95% by weight is that if the content of titanium is less than 80% by weight, the sinterability is reduced and the strength of the sintered body is also reduced, and if it exceeds 95% by weight, TiC phase and TiB as hard phases are added. This is because the phases cannot coexist and the hardness of the sintered body becomes low. It is desirable that titanium is contained in an amount of 85 to 90% by weight based on the total amount. Part of titanium may be present as a metal in the sintered body. The amount of the metal present is preferably 40% by weight or less, and particularly preferably 30% by weight or less.

The reason why the amount of boron is 3 to 12% by weight in total is that if the amount of boron is less than 3% by weight, TiB as a hard phase does not exist and the hardness becomes low. On the other hand, if the amount exceeds 12% by weight, the diboride TiB ₂
Is increased, and the firing temperature is increased. The amount of boron is preferably 4 to 9% by weight based on the total amount.

The reason why the carbon content is 2 to 8% by weight is that if the carbon content is less than 2% by weight, TiC as a hard phase does not exist and the hardness becomes low. On the other hand, when the content is more than 8% by weight, carbon remains in the sintered body and the sinterability is deteriorated. Carbon is preferably 3 to 6% by weight in the total amount.

With respect to the main components, V, Zr, Nb, M
At least one selected from o, Hf, Ta, and W is 0.
5 to 15.0 parts by weight is preferably present, but V, Zr, Nb, and M are present in this proportion.
By containing at least one selected from o, Hf, Ta, and W, mechanical properties such as transverse rupture strength, Vickers hardness, and fracture toughness can be further improved. Further, the amount is 0.5 to 15.0 parts by weight, when the amount is less than 0.5 parts by weight, the effect of improving the mechanical properties is small and the amount is more than 15.0 parts by weight. In that case, the sinterability tends to decrease, and the strength tends to decrease.
It is desirable that at least one element selected from V, Zr, Nb, Mo, Hf, Ta and W be present in an amount of 2 to 12 parts by weight. Most of these elements are TiB or TiC
It forms a solid solution in the phase and improves the properties.

In the present invention, it is desirable that the content of allergic metal is 0.3% by weight or less. Al, Cr, Mn, and F are allergen sources.
e, Co, Ni, Cu, Zn, Rh, Pd, Cd, S
There are n and Sb. The reason for limiting the content of such a metal as described above is that if it is present in an amount of more than 0.3% by weight, metal allergy is likely to occur. That is, in order to prevent metal allergies, the Danish law, which regulates the elution amount of metals that are allergens to 0.5 μg / cm ² / week or less, is a surface technology (vol4
5, No. 9, P910), and the silver sintered body for decorative parts of the present invention, when the content of the allergen source metal is 0.3% by weight or less, the above-mentioned standard is confirmed. However, if the amount exceeds 0.3% by weight, the elution amount of the metal that is an allergic source may exceed 0.5 μg / cm ² / week. Easy to cause allergies. Therefore, in the present invention, the content of the allergen source metal is set to 0.3% by weight or less. The amount of metal that causes allergies is 0.1% by weight
The following is particularly desirable.

As described above, in order to reduce the content of the metal causing metal allergy to 0.3% by weight or less, the above-mentioned metal should not be used as a raw material for producing the sintered body of the present invention. Needless to say, it is effective to use a high-purity raw material having a small content of the above-mentioned metal in the raw material.

In the present invention, the most desirable composition is 85 to 90% by weight of titanium, 4 to 9% by weight of boron in total, and 3 to 6% by weight of carbon in total of 3 components.
And mainly contains TiC phase and TiB phase, and further contains 2 to 12 parts by weight of at least one element selected from V, Zr, Nb, Mo, Hf, Ta, and W, and contains a metal that becomes an allergic source. The amount is 0.1% by weight or less based on the total amount.

In the sintered body of the present invention, mainly TiC
Phase and TiB phase exist, and metallic titanium, V, Zr, Nb, Mo, Hf, Ta and W may exist in these grain boundaries.

The silver-colored sintered body of the present invention is, for example, a mixture of titanium powder and titanium carbide or boride powder as raw material powder, or V, Zr, Nb, M.
After mixing and crushing an element consisting of o, Hf, Ta and W, or a mixture of one or more kinds of these carbides and borides, a binder is added in a predetermined amount and pressure-formed into a desired shape under a predetermined pressure. Is debindered at a predetermined temperature in a non-oxidizing atmosphere and then baked at a predetermined temperature.

Preferably, for example, the particle size is 0.5 to 3.0.
Titanium carbide and boride having a particle size of 5 to 2
Titanium powder of 50 μm and, if desired, particle size of 1.0 to 1
Powders of elements of 0.0 μm of V, Zr, Nb, Mo, Hf, Ta, W, or their carbides and borides were weighed and mixed, and then mixed and pulverized in an organic solvent such as acetone, Add a binder and shape into the desired shape. Then, the molded body is debindered at a predetermined temperature in a non-oxidizing atmosphere, and then vacuum-baked at a predetermined temperature.

Here, as the boride of titanium, Ti is
Both B ₂ and TiB can be used. When TiB ₂ is used as a raw material, TiB ₂ and metallic Ti
Reacts at 1300 to 1600 ° C to produce TiB.

TiB is preferably present as needle crystals in the sintered body, but it does not have to be needle-shaped.

As the raw material used, it is necessary to set the content of the metal which is an allergen source to 0.3% by weight or less of the total raw material.

As a firing method, the degree of vacuum is 10 ^-1 to 10 ^-5.
Firing is performed at a temperature of 1300 to 1600 ° C. under reduced pressure or no pressure in a torr atmosphere or various atmospheres. Furthermore, in hot isostatic pressing (HIP) under a non-oxidizing atmosphere,
It is desirable to bake at 1200 to 1400 ° C under 100 to 2000 atm. The firing time is usually 0.5 to 5 hours, although it depends 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 silver color appears.

The silver-colored sintered body of the present invention contains 80 to 95% by weight of titanium and 3 to 12% of boron in the sintered body.
The TiC phase and the TiB phase can be present as the crystal phase by adjusting the composition of the raw materials so that the content of carbon is 2 to 8% by weight in the total amount.

In the silver-colored sintered body of the present invention, as long as the composition range of the present invention is satisfied, even if a small amount of impurities, other compounds and metals are contained, there is no effect on the characteristics.

[0028]

In the silver-colored sintered body for decorative parts of the present invention, the TiC phase in the sintered body contributes to imparting a silver color, and the TiB phase improves mechanical properties such as bending strength, Vickers hardness and fracture toughness. Contribute. In the present invention, the sintered body is mainly Ti.
Since it is composed of the C phase and the TiB phase, it has a glossy silver color, and it is possible to obtain excellent bending strength, Vickers hardness, and fracture toughness, and it is possible to perform firing at a low temperature of 1300 to 1600 ° C.

Further, V, Zr, Nb, Mo, Hf, T
By containing a and W, mechanical properties such as strength, hardness and fracture toughness can be further improved.

Furthermore, in the silver-colored sintered body for decorative parts of the present invention, the content of the allergen source metal is 0.3% by weight or less, so that it is possible to reliably prevent the occurrence of allergies. Such a silver-colored sintered body can be used, for example, for decoration of watch cases, watch bands, necklaces, bracelets, scissors, blades, fishing tackles, and other tools and machine parts. You can

[0031]

【Example】

Example 1 TiC and Ti having an average particle size of 1.1 μm as raw material powder
B ₂ and Ti powder having a particle size of 40 μm were used, and these were weighed and mixed in the proportions shown in Table 1, mixed and pulverized in an organic solvent such as acetone for about 68 hours, and added with 6% by weight of paraffin. Press-molded into a desired shape at 2.0 ton / cm ² . The molded product is placed in a non-oxidizing atmosphere at 40
After debinding at 0 ° C., vacuum firing was performed at a temperature shown in Table 1 for 1 hour in a vacuum heating furnace having a vacuum degree of 10 ⁻³ torr. The firing was performed by adjusting the atmosphere so that the composition did not change.

[0032]

[Table 1]

As a result of identifying the crystal phase of the final sintered body thus obtained by X-ray diffraction measurement, it was confirmed that the TiC phase and the TiB phase were mainly present in all the products of the present invention. The final sintered body was analyzed by ICP emission spectroscopy, and the results are shown in Table 1. In addition, the metal content that is a source of allergy was measured by ICP emission spectroscopy. In addition, in Table 1, since only Ni and Fe were confirmed to be present as the metal causing allergies, the contents of Ni and Fe are described.

In Table 1, the presence or absence of metallic titanium is
When the presence of metallic titanium can be confirmed by both X-ray diffraction measurement and SEM structure observation, ◯, when it is not confirmed by X-ray diffraction measurement but can be confirmed by SEM structure observation, Δ, even by X-ray diffraction measurement by SEM The case where it could not be confirmed by tissue observation was marked with x. Figure 1 shows the organization chart by SEM
Shown in In FIG. 1, reference numeral 1 indicates a TiC phase, and 2 indicates a TiB phase.

Then, the sintered body was surface-ground and mirror-polished, and then subjected to bending strength, Vickers hardness (Hv), fracture toughness value, corrosion resistance, and metal elution test to visually check the color of the sintered body. confirmed.

The bending strength was measured according to JIS R1601 three-point bending test method, and the Vickers hardness was measured according to JIS Z2.
244 test method was followed. The fracture toughness value was obtained by the IF method. In the corrosion resistance test, artificial sweat (pH 4.7) conforming to the ISO (International Organization for Standardization) standard was used as a corrosive liquid, and a sample mirror-polished in the artificial sweat kept at a temperature of 37 ° C. ± 2 ° C. was used. After immersion for a week, the condition of the polished surface was observed, and the degree of corrosion was visually observed. The case where the polished surface was not corroded was marked with ◯, and the case where the polished surface was slightly corroded was marked with ∆. In addition, it was confirmed visually that all the samples of the present invention had a glossy silver color. Table 2 shows the results.

[0037]

[Table 2]

From these Tables 1 and 2, in the samples of the present invention, the bending strength is 700 to 1000 MPa, the Vickers hardness is 10.0 to 13.5 GPa, and the fracture toughness value is 5.0 to.
It is 6.8 MPa · m ^1/2 , which shows that the corrosion resistance is good.

Further, in the sample of the present invention, it is found that the content of the metal which is an allergen source is 0.3% by weight or less.
Therefore, the occurrence of metal allergy can be reliably prevented.

Example 2 TiC and Ti having an average particle size of 1.1 μm as raw material powders
B ₂ , Ti powder having a particle size of 40 μm, an element composed of V, Zr, Nb, Mo, Hf, Ta and W having an average particle size of 1.0 μm,
Alternatively, these carbides or borides are used, and these are weighed and mixed so that the respective metal amounts of the final sintered body are in the ratios shown in Table 3, and then mixed and pulverized in an organic solvent such as acetone for about 68 hours, Add 6% by weight of paraffin and add 2.0 ton
/ Cm ² to form a desired shape under pressure. The molded product is debindered at 400 ° C. in a non-oxidizing atmosphere, and then the temperature is set to 1 in a vacuum heating furnace having a vacuum degree of 10 ⁻³ torr.
Vacuum baking was performed at 450 ° C. for 1 hour. Further, hot isostatic pressing (HIP) was performed at 1300 ° C. for 1 hour in an argon atmosphere. The crystal phase and metal elements of the final sintered body thus obtained were analyzed, and the content of metal as an allergen was analyzed in the same manner as in Example 1 above. Table 3 shows the results.

[0041]

[Table 3]

Then, the sintered body was surface-ground and mirror-polished, and thereafter, in the same manner as in Example 1, bending strength, Vickers hardness (Hv), fracture toughness value, corrosion resistance and metal elution test were carried out. Moreover, the color of the sintered body was visually confirmed. As a result of visual observation, it was confirmed that a glossy silver color appeared in the samples of the present invention.

The results are shown in Table 4.

[0044]

[Table 4]

From these Tables 3 and 4, the inclusion of at least one of V, Zr, Nb, Mo, Hf, Ta and W in the sintered body improves the bending strength and Vickers hardness. You can see that It is also found that the content of the metal which is the source of this allergy is 0.3% by weight or less.

[0046]

As described above in detail, according to the silver-colored sintered body for a decorative part of the present invention, it has strength and hardness that do not cause any practical problems, is excellent in chipping resistance and corrosion resistance, and causes allergy. As a silver-colored ornament containing almost no metal component and having a silver-colored mirror surface easily exposed due to improved sinterability, as a silver-colored ornament that does not cause corrosion or scratches for a long period of time, for example, a watch case, a watch band, a necklace. It can be used for bracelets, buttons, etc.

[Brief description of drawings]

FIG. 1 shows a structural chart by SEM.

[Explanation of symbols]

 1 ... TiC phase 2 ... TiB phase

Claims (2)

[Claims] 1. At least titanium, carbon, and boron as main constituent elements, and titanium is 80 to 95 out of the total amount on the basis of three components.
A silver-colored sintered body comprising 3 to 12% by weight of boron, 3 to 12% by weight of boron, and 2 to 8% by weight of carbon, the TiC phase and the TiB phase being present in the sintered body, and a source of allergy. A silver-colored sintered body for decorative parts, characterized in that the total metal content is 0.3% by weight or less. 2. At least titanium, carbon, and boron are the main constituent elements, and titanium is 80 to 95 out of the total amount on the basis of three components.
% By weight, 3-12% by weight of boron in total, and 2-8% by weight of carbon in 100% by weight of the main component.
A silver-colored sintered body containing at least one selected from V, Zr, Nb, Mo, Hf, Ta, and W in a proportion of 0.5 to 15.0 parts by weight, wherein the TiC phase is present in the sintered body. A silver-colored sintered body for decorative parts, characterized in that a TiB phase is present, and a metal content which becomes an allergen source is 0.3% by weight or less in the total amount.