JPH08157990A - Silver-colored sintered compact and its production - Google Patents

Abstract

PURPOSE: To produce a silver-colored sintered compact capable of ensuring superior deflective strength, Vickers hardness and fracture toughness 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. In this sintered compact, a TiC phase 1 and a TiB phase 2 exist and a part of the TiB phase is preferably acicular crystals. A group IVa, Va or VIa element of the Periodic Table other than Ti is allowed to exist in this sintered compact by 0.5-20.0 pts.wt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a silver-colored sintered body used for decorative parts, tools, sliding members, industrial blades, stamps, eyeglass frames, tableware, shoe pins, sports equipment such as golf clubs, and the like. And a method of manufacturing the same, particularly, fishing tackle parts, exterior parts for watches, tie pins,
As a decorative member for bracelets, earrings, earrings, etc., it has excellent strength, hardness, chipping resistance and corrosion resistance.
The present invention also relates to a silver-colored sintered body having excellent decorativeness and a method for manufacturing the same.

[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 part, a sintered alloy in which a carbide of stainless steel or a metal, for example, WC 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.
B ₂ type sintered bodies have been developed and put into practical use (for example, JP-A-58-27975 and JP-A-61-27026).
No. 5, JP-A-5-294739). These TiB ₂ system sintered bodies have a bending strength of 800 to 1000.
MPa, Vickers hardness is 18 to 24 GPa, and fracture toughness value is 4 to 7 MPa · m ^1/2 , which shows excellent corrosion resistance.

[0005]

However, the TiB ₂ system sintered body as described above has a problem that it is necessary to sinter at a high temperature of 1600 to 2000 ° C. and the sinterability is low.

The silver-colored sintered body of 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 can be sintered at a low temperature of 1300 to 1600 ° C. It is an object to provide a body and a method for producing the body.

[0007]

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 primarily forming the iC and TiB phases,
It has almost the same characteristics as the TiB ₂ system sintered body,
The present inventors have found that they can be fired at a low temperature of 1300 to 1600 ° C, and have reached the present invention. Further, they have found that the presence of at least a part of titanium boride as acicular crystals can improve the toughness of the sintered body, and have reached the present invention.

That is, the silver-colored sintered body of the present invention contains at least titanium, carbon and boron as main constituent elements, and based on the three components, titanium is 80 to 95% by weight in the total amount, and boron is 3 to 12% by weight in the total amount. A silver-colored sintered body containing carbon in an amount of 2 to 8% by weight, the TiC phase and the TiB in the sintered body
There are phases. Here, it is desirable that a part of the TiB phase is a needle crystal.

Further, the silver-colored sintered body of the present invention is, for example,
It is obtained by molding a mixture of titanium powder, titanium carbide powder and titanium boride powder into a predetermined shape, and calcining the mixture in a non-oxidizing atmosphere at 1300 to 1600 ° C.

Here, the reason why the amount of elements is limited as described above will be explained.

First, the reason why the total amount of titanium is 80 to 95% by weight is that when the amount of titanium is less than 80% by weight, the sinterability is lowered and the strength of the sintered body is lowered. If it exceeds, the TiC phase and T as a hard phase
This is because the iB phase 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 present as metal is 40% by weight
The following is desirable, and particularly 30 wt% or less is desirable.

The amount of boron is set to 3 to 12% by weight in the total amount because 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 does not exist as a hard phase and the hardness is lowered. 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.

In the silver-colored sintered body of the present invention, the TiC phase and the TiB phase are present in the sintered body.
It is desirable that a part of the iB phase is acicular crystals. This is because the toughness of the sintered body can be significantly improved by making a part of the TiB particles into needle crystals.

The acicular crystals mean that they also include columns having a large diameter, and the TiB particles preferably have an aspect ratio (major axis / minor axis) of 1.5 to 10 and a minor axis of 0.
The thickness is preferably 5 to 20 μm. This is because the effect of improving the toughness is enhanced by making the TiB particles the size as described above, and if the TiB particles exceed the above range, the density of the sintered body tends to be low and the densification tends not to occur. . TiB particles are particles having anisotropy and are considered to be acicular crystals.

Further, the needle-like crystal of TiB may be present in a part of the TiB phase. The abundance of needle crystals is
20% or more of the B particles is desirable for improving the toughness. All of the TiB phase may be needle crystals.

Further, the silver-colored sintered body of the present invention contains at least titanium, carbon and boron as main constituent elements, and based on three components, titanium is 80 to 95% by weight in the total amount, and boron is 3 to 12% by weight in the total amount. 100 parts by weight of the main component of carbon, which is 2 to 8% by weight, is included in the periodic table 4a, 5a, 6
A silver-colored sintered body in which a group a element (excluding Ti) is present in a proportion of 0.5 to 20.0 parts by weight, wherein Ti is contained in the sintered body.
The C phase and the TiB phase are present. It is desirable that a part of the TiB phase is acicular crystals.

The reasons for limiting the amounts of titanium, carbon and boron are as described above. The elements of groups 4a, 5a, and 6a of the periodic table (excluding Ti) were allowed to exist with respect to the main component composed of titanium, boron, and carbon because the elements of groups 4a, 5a, and 6a of the periodic table were present. This is because the inclusion of the element can further improve mechanical properties such as transverse rupture strength, Vickers hardness, and fracture toughness. Further, the amount is 0.5 to 20.0 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 20.0 parts by weight. This is because in this case, the sinterability is lowered and the strength is lowered. Periodic Table 4a, 5
It is desirable that the a and 6a group elements are present in an amount of 2 to 16 parts by weight. Most of these Group 4a, 5a, and 6a elements of the periodic table are dissolved in the TiB phase or the TiC phase to improve the characteristics.

The most desirable composition is titanium in an amount of 85 to 90% by weight, boron in an amount of 4 to 9% by weight, carbon in an amount of 3 to 6% by weight, and TiC phase and TiB phase are mainly present. 2 to 16 parts by weight of elements of groups 4a, 5a and 6a (excluding Ti) of the periodic table are further contained with respect to 100 parts by weight of the main components composed of these.

It is desirable that a part of the TiB phase is a needle crystal.

The TiC phase and the TiB phase are mainly present in the sintered body, and metallic titanium and elements of Groups 4a, 5a and 6a of the periodic table may be present in the grain boundaries of these. . In addition, the periodic table 4
The a, 5a, and 6a group elements may be in solid solution.

Zr, H are the elements of Group 4a of the periodic table.
f, and elements of Group 5a of the periodic table are V, Nb,
There is Ta, and as elements of Group 6a of the Periodic Table, Cr, M
There are o and W. Mo, Ta, and W are the most desirable additives. Furthermore, when the silver-colored sintered body of the present invention is used as a decorative component, the elements of Groups 4a, 5a and 6a of the periodic table are preferably V, Zr, Nb, Mo, Hf, Ta and W. In addition, in order to prevent allergies, metal impurities (A
1, Cr, Mn, Fe, Co, Ni, Cu, Zn, R
h, Pd, Cd, Sn, Sb) content is 0.3% by weight
The following is desirable.

The silver-colored sintered body of the present invention is, for example, a mixture of titanium powder, titanium carbide powder, and titanium boride powder as raw material powder, or a mixture thereof with a group 4a, 5a, or 6a element of the periodic table. , Or a mixture of one or more of these carbides and borides is mixed and ground,
It is obtained by adding a predetermined amount of a binder, press-molding it into a desired shape at a predetermined pressure, and firing this at a predetermined temperature in a non-oxidizing atmosphere.

Suitably, 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
Metals of elements of groups 4a, 5a and 6a of the periodic table of 0.0 μm or their carbides, nitrides and boride powders are weighed and mixed, and this is mixed and ground in an organic solvent such as acetone, and then an organic binder is added. In addition, it is formed into a 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 in a vacuum heating furnace.

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.

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. Metals of Group 4a, 5a, 6a group elements or their carbides,
When a nitride or boride is added, it is 100 to 20 in hot isostatic pressing (HIP) in a non-oxidizing atmosphere.
It is desirable to bake at 1200 to 1400 ° C. under 00 atm. The firing time is usually 0.5, although it depends on the size of the sample.
~ 5 hours. Then, after firing, the surface of the sintered body is mirror-polished with diamond paste or the like, whereby a glossy silver color appears.

In the silver-colored sintered body of the present invention, as long as the composition range of the present invention is satisfied, a small amount of impurities, other compounds, and metals will not affect the characteristics.

[0028]

In the silver-colored sintered body of the present invention, the TiC phase in the sintered body contributes to imparting a silver color, and the TiB phase contributes to improvement in mechanical properties such as bending strength, Vickers hardness and fracture toughness.

In the present invention, the sintered body is mainly T
Since it is composed of iC phase and TiB phase, it has a glossy silver color, and it is possible to obtain excellent bending strength, Vickers hardness, and fracture toughness, as well as 1300 to 1600 ° C.
Can be fired at low temperature.

Further, the fracture toughness is further improved by the existence of a part of the TiB phase as needle crystals. Also,
By including elements of Groups 4a, 5a and 6a of the periodic table, mechanical properties such as bending strength, Vickers hardness and fracture toughness can be further improved.

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. Can be used.

[0032]

【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 was debindered at a predetermined temperature in a non-oxidizing atmosphere, and then vacuum-baked at a temperature of 1450 ° C. 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.

[0033]

[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 TiC phase and 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 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. In addition, by observing the structure by SEM, T
The average value of the aspect ratio of the iB particles was obtained.

Then, the sintered body was surface-ground and mirror-polished, and then the bending strength, Vickers hardness (Hv), fracture toughness value and corrosion resistance were tested, and the color of the sintered body was visually confirmed. The bending strength is measured according to JIS R1601 three-point bending test method, and the Vickers hardness is measured according to JIS Z2.
244 test method was followed. The fracture toughness value was obtained by the IF method.

The corrosion resistance test is performed by ISO (International Organization for Standardization)
Using artificial sweat (pH 4.7) conforming to the standard as a corrosive liquid, the lower half of the mirror-polished sample was immersed in artificial sweat maintained at a temperature of 37 ° C ± 2 ° C for 24 hours, and the sample after immersion It was performed by observing the state of the polished surface. 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 visually confirmed that a glossy silver color appeared in all the samples. Table 2 shows the results.

[0038]

[Table 2]

From these Tables 1 and 2, the samples of the present invention have a flexural strength of 700 to 1000 MPa, a Vickers hardness of 10.0 to 13.5 GPa and a fracture toughness value of 5.
It is 0 to 6.8 MPa · m ^1/2 , which shows that the corrosion resistance is good.

Example 2 TiC and Ti having an average particle size of 1.1 μm as raw material powders
B2, Ti powder having a particle size of 40 μm, elements of Groups 4a, 5a and 6a of the periodic table having an average particle size of 1.0 μm, or their carbides or borides are used. The mixture is weighed and mixed in a ratio of 3 and mixed and pulverized in an organic solvent such as acetone for about 68 hours, 6% by weight of paraffin is added, and the mixture is pressure-molded into a desired shape at 2.0 ton / cm ² . The molded product is debindered at 400 ° C. in a non-oxidizing atmosphere, and then the vacuum degree is 10 ^−3.
Vacuum firing was performed for 1 hour at a temperature of 1450 ° C. in a vacuum heating furnace of torr. Furthermore, 1 in an argon atmosphere
Hot isostatic pressing (HIP) was performed under the conditions of 300 ° C. for 1 hour. The analysis of the crystal phase and the metal element of the final sintered body thus obtained, and the measurement of the aspect ratio were performed in the same manner as in Example 1 above. Table 3 shows the results.

[0041]

[Table 3]

Then, the sintered body was subjected to surface grinding and mirror polishing, and thereafter, the aspect ratio, bending strength, Vickers hardness (Hv), fracture toughness value and corrosion resistance were tested in the same manner as in Example 1 above. 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 all the samples. The results are shown in Table 4.

[0043]

[Table 4]

From these Tables 3 and 4, it is found that the addition of the elements of Groups 4a, 5a and 6a of the Periodic Table to the sintered body improves the bending strength and Vickers hardness in particular. I understand.

[0045]

As described in detail above, according to the silver-colored sintered body of the present invention, it has strength and hardness that do not cause any problems in practical use, is excellent in chipping resistance and corrosion resistance, and has improved sinterability. The silver-colored mirror surface can be easily revealed by this, and as a silver-colored accessory 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 ornaments such as bracelets and buttons, putters, fishing tackle, and blades. The silver-colored sintered body of the present invention can also be used for sliding members other than ornaments, tableware, sports equipment and the like.

[Brief description of drawings]

FIG. 1 shows a structural chart by SEM.

[Explanation of symbols]

 1 ... TiC phase 2 ... TiB phase

Claims (5)

[Claims] 1. 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.
% Of boron, 3-12% by weight of boron in total, and 2-8% by weight of carbon in total, characterized in that a TiC phase and a TiB phase are present in the sintered body. A silver-colored sintered body. 2. The silver-colored sintered body according to claim 1, wherein a part of the TiB phase is a needle crystal. 3. 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.
% Of boron, 3 to 12% by weight of total amount, and 2 to 8% by weight of carbon in total of 100 parts by weight of main components, elements of Groups 4a, 5a, and 6a of the periodic table (excluding Ti) are added. 0.
A silver-colored sintered body which is present in an amount of 5 to 20.0 parts by weight, wherein a TiC phase and a TiB phase are present in the sintered body. 4. The silver-colored sintered body according to claim 3, wherein a part of the TiB phase is acicular crystals. 5. A mixture of titanium powder, titanium carbide powder, and titanium boride powder is molded into a predetermined shape, and this is molded in a non-oxidizing atmosphere at 1300 to 160.
A method for producing a silver-colored sintered body, which comprises firing at 0 ° C.