JPH06145703A - Ti-ag alloy parts - Google Patents

Abstract

PURPOSE:To easily produce Ti and Ti alloy precision parts with a complicated shape in which oxidation and carbonization in an injection molding process can be prevented and excellent in characteristics by coating the surface of Ti powder with Ag. CONSTITUTION:The surface of Ti or Ti alloy powder is coated with Ag, which is kneaded with resin material into a compound, and compacting and sintering in vacuum are executed to obtain a Ti-Ag alloy sintered body contg. 2 to 10wt.% Ag. The Ti-Ag alloy sintered body obtd. by incorporating the same alloy with <=1wt.% of at least one kind among bismuth, tellurium, selenium and lead is subjected to cutting, grinding or polishing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ti-Ag type alloy part manufactured by a metal powder injection molding method.

[0002]

2. Description of the Related Art In the manufacturing method of precision parts centering on cutting work from plate material and round bar obtained by arc melting, there is a problem in mass production of precision parts due to severe wear of tools due to built-up blades. As described in JP-A-21823, a metal was added as a third element in order to impart free-cutting property.

In recent years, a metal powder injection molding method (hereinafter referred to as MIM) has attracted attention as a new method for manufacturing metal parts, and practical application is progressing mainly for stainless steel materials. Since Ti or Ti alloy is light, strong, and has excellent corrosion resistance, it has been put to practical use for precision parts such as watches, glasses, and cameras based on the cutting process described above. Parts manufactured by the MIM method are required to manufacture complicated shapes.

However, since an oxide film is easily formed on the Ti powder surface, the sinterability is poor. In addition, since the oxide remains in the sintered body and the mechanical strength required for parts deteriorates, it is possible to produce such Ti or Ti by devising the binder as described in JP-A-03-183666. I was trying to get a Ti alloy part.

[0005]

However, the arc-melting material centered on the cutting work according to the above-mentioned conventional technique is one or more multi-component alloys of aluminum, manganese, iron, etc. as the second element, and is limited to special applications. Therefore, there are few practical examples of precision parts, and it is the current situation that they are produced with difficult processing. In the MIM method, Ti and Ti alloys, which have a strong bonding force with oxygen and carbon, can be used in the kneading, molding, and degreasing processes even if the mixing ratio of the binder resin material is changed or the atmosphere during sintering is strictly controlled. Inevitable to oxidation or carbonization. Furthermore, even if the atmosphere of these steps is controlled, the contamination by oxygen, carbon, and water contained in the binder is inevitable. Moreover, it is impossible by the MIM method to eliminate the binder containing the resin component as the main component.

Also, Ti or Ti thus contaminated
The sintered body of the alloy powder was very brittle, and a local battery was formed between the contaminated portion and the non-contaminated portion, which was likely to cause corrosion such as pitting corrosion and could not be used at all in practice.

As described above, conventional arc melting, MI
Both methods M have problems.

The present invention solves such a problem, and achieves high density, high accuracy, and high precision which cannot be obtained by the ordinary MIM method.
It is intended to provide a precision component made of a Ti alloy having high corrosion resistance.

[0009]

In order to solve the above problems, the entire surface of Ti or Ti alloy powder is coated with Ag by a wet or dry film forming method, and this is used as a raw material powder. For parts requiring cutting because of high precision, one type of bismuth, tellurium, selenium, and lead is used as the third element.
Add as alloy powder or simple substance powder. It is characterized in that the above raw material powder is kneaded with a resin material (binder), injection-molded and sintered to obtain a Ti-Ag alloy part.

[0010]

According to the present invention, T which is very active and easily oxidized
Before kneading the i or Ti alloy powder, the Ag film was
The surface of the i powder is coated to a thickness of 0.3 micrometer or less, and then compounded with a resin material. Also, the atmosphere in the sintering process is accurately controlled, and the concentration of oxygen, carbon, etc. is made extremely low. As a result, in the MIM process, it is possible to prevent oxidation or carbonization of Ti or Ti alloy powder due to the atmosphere and contamination from contact substances, and obtain a sintered product of Ti alloy of high density, high precision and high strength. Become.

If the thickness of the Ag coating is less than 0.05 micrometer, it is difficult to apply a uniform coating to the surface of the Ti powder, so that oxygen / carbon will invade and a Ti alloy with a low oxygen content / low carbon content will be formed. Sintered bodies cannot be manufactured. The 0.05 micron meter Ag coating corresponds to 2 weight percent. On the other hand, if the thickness exceeds 0.3 micrometer, the Ti α phase alone becomes difficult and the brittleness of the material increases, so that chipping and chipping occur at the corners of precision parts and the effect of the present invention cannot be obtained. An Ag coating 0.3 micron meter corresponds to 10 weight percent.

Further, the surface of the sintered product obtained from the MIM sintered body becomes matte. In general, precision parts are often required to have high surface roughness to a mirror surface and high precision locally. Therefore,
Although it is lighter than the material produced by arc melting, it requires machining such as cutting, grinding, and polishing. In order to improve this workability, it is beneficial to add bismuth tellurium selenium and lead, which contribute to the improvement of machinability due to the grain boundary reaction, to the Ti-Ag raw material. The control of the amount added depends on the degree of cutting.
The increase or decrease (0-1 weight percent) of this third element additive is determined. However, since the addition amount and the brittleness are in a proportional relationship, the upper limit is preferably 1% by weight. MIM
In the method, since the shape may be subjected to shape correction (sizing) to the sintered body, brittleness of the material is an important characteristic. In addition, the characteristics common to precision parts such as watches, camera and glasses are light weight and corrosion resistance, but the watch case has scratch resistance as
Some of them are unique to the elasticity of spectacle frames, so it is necessary to take appropriate measures.

It is desirable that the raw material powder has an average particle size of 30 μm or less applicable to the MIM method.
(See No. 02-54733) The powder may be produced by any manufacturing method such as hydrodehydrogenation powder and gas atomized powder, but in order to improve the spring property, the smaller the oxygen content of the powder, the better the result. Was obtained.

As the organic binder, known binders such as thermoplastic resins and wax conventionally used in the MIM method can be used.

[0015]

EXAMPLES The present invention will be described in detail below based on examples.

Example 1 Ti containing 0.2 or 0.5 weight percent oxygen with an average particle size of 30 microns.
The surface of the powder was coated with Ag by the electroless plating method. Ti
When electroless plating is applied to the powder, it is not possible to coat the plating film with good adhesion because the oxygen in the atmosphere is adsorbed on the surface of the Ti powder to form a passive film even if the plating is performed directly. . Therefore, it is necessary to selectively deposit the electroless plating film on the Ti powder by activating the surface of the Ti powder.

First, after dipping in dilute sulfuric acid having a concentration of 5 (volume)% for 5 minutes, washing with pure water is performed for 5 minutes. Next, it is immersed in a sensitizing solution having the composition shown in Table 1 for 10 minutes at room temperature,
Then, pure water cleaning is performed for 5 minutes. Further, it was dipped in the activating liquid shown in Table 1 for 10 minutes at room temperature and then dipped in still water for 5 minutes to remove excess activator.

[0018]

[Table 1]

After activating the surface of the Ti powder under the above conditions, electroless plating was carried out at room temperature with the composition shown in Table 1. It is desirable to stir the Ti powder during plating so that it does not precipitate and to add necessary chemicals so as to keep the component concentration and PH of the electroless plating solution constant. By changing the plating time from 3 minutes to 60 minutes, the thickness of the plating film can be adjusted in the range of 0.05 to 0.3 micrometer.
Formed on the powder surface. Next, Ti with these Ag coatings
The powder is kneaded with an organic binder composed of a thermoplastic resin, wax, and a plasticizer by a pressure kneader, and the temperature at this time is preferably in the range of room temperature (20 degrees Celsius) to 120 degrees Celsius. This is because if the temperature is higher than this, the binder may be carbonized, and if the temperature is lower than this, the viscosity of the binder becomes large and the kneading becomes difficult. The compounding ratio of the binder is about 10% by weight, and the MIM compound prepared in this manner is used in an injection molding machine at a cylinder temperature of 150 ° C. in an inert gas atmosphere, a watch case, a band, a spectacle frame, and machinability. A bending strength test piece (55 × 10 × 3 mm) was molded.

Degreasing was carried out by raising the temperature to 450 ° C. in nitrogen for 48 hours, followed by sintering in vacuum at 1200 ° C. for 2 hours.

As a comparison material, a Ti powder (average particle size 30 μm) without plating and Ag powder (average particle size 25 μm) were mixed and kneaded, molded, degreased and sintered to prepare a test piece. did.

(Embodiment 2) Tellurium powder (average particle diameter: 30 micrometer) was mixed with the powder obtained by coating the Ti powder described in Embodiment 1 with an Ag thin film to a thickness of 0.1 micrometer. To prepare a test piece.

The bending strength test, hardness, and machinability of the above sintered body were measured in comparison with conventional products. The results are shown in Table 2. For machinability, use a carbide tool to cut at a cutting speed of 20
m / min, depth of cut 0.5 mm, feed 0.15 mm / rev (same conditions as Japanese Patent Publication No. 55-21823). It shows that he has good sex. The results are shown in Table 2, and the bending strength of the sintered body of this example is improved as compared with the comparative material.
In particular, since the mixed powder (Sample D) was moloi, the problems of elasticity of the spectacle frame and occurrence of chipping during grinding of the watch case were solved and the range of practical use was reached.

[0024]

[Table 2]

The spectacle frame is required to have some bendability and appropriate elasticity in order to fit each customer at the time of purchasing the spectacles, but the sample A having a small oxygen content is superior to the sample B in this embodiment. This proves that the above properties depend on the oxygen content of the Ti powder. Further, the composition (Ag: 10% by weight or less) that is unified into the α phase and the solution treatment (850 ° C. for 2 hours or more after sintering) are effective for improving the characteristics.

In the case of a watch, a slight grinding is required in order to make the matte surface of the sintered body mirror-finished and to make the corners and the ridges sharp, but the chipping or chipping that occurs at this time is required. The prevention of brittleness is also effective in improving the brittleness. Furthermore,
Although the diversification of design is an important issue for the watch case as a manufacturer, when the sintered body obtained by the common mold can be partially cut, the machinability of the sample C In terms of color tone, it is possible to flexibly cope with the white tone of the α phase alone to the blackish metallic color containing some intermetallic compounds and the characteristics unique to the MIM method. Further, in a watch case, improvement in scratch resistance during carrying is also a factor that enhances commercial value. Therefore, as a measure to increase the hardness, the sintered body or the watch case after polishing is subjected to the age hardening treatment (450 ° C. for 2 hours) after the solution treatment described above and the surface of Ti is modified (special (Kaisho 51-33732) and (Bulletin of Faculty of Engineering, Ehime University Vo
l. 12, No3, Page 405-416.1992)
It becomes possible to make it super hard.

In the first embodiment, the Ti powder is coated with Ag. However, a Ti-Ag alloy gas atomized powder may be used. Similarly, the tellurium powder of the second embodiment may be a Ti-Ag-Te alloy powder. Is.

As described above, according to the present invention, it is possible to easily realize alloy parts having unique characteristics that match the needs.

[0029]

As described above, the Ti or T of the present invention is used.
The i-alloy powder is coated with an Ag thin film to prevent oxidation and carbonization during the MIM manufacturing process to obtain alloy parts with good functional characteristics, and to improve the machinability by bismuth, tellurium, selenium, and lead, which makes it complicated. In addition to providing Ti-Ag alloy parts such as shaped watches, glasses, and camera units at low cost,
Since i or Ti alloy powder can be stored for a long period of time, it also has an effect of facilitating powder management during mass production.

Front page continued (72) Inventor Tadaaki Gomachi 3-3-5 Yamato, Suwa City, Nagano Seiko Epson Corporation (72) Inventor Shinichi Yotsuya 3-3-5 Yamato, Suwa City, Nagano Prefecture Seiko Epson Corporation Within

Claims (4)

[Claims] 1. The surface of Ti or Ti alloy powder is coated with Ag by a wet or dry film forming method, the powder is compounded with a resin material, compounded by injection molding, and sintered to obtain 2 parts by weight of Ag. A Ti-Ag based alloy part characterized by containing not less than 10 cents and not more than 10 percent by weight. 2. A surface of Ti or Ti alloy powder is coated with Ag by a wet or dry film formation method, and the powder is coated with at least one of bismuth, tellurium, selenium and lead by 0.0.
By adding 5 to 1.0 weight percent, compounding the powder with a resin material, injection molding, and sintering,
A Ti-Ag based alloy part characterized by containing Ag in an amount of 2% by weight or more and 10% by weight or less. 3. The Ti-Ag according to claim 1, wherein the Ti powder has an oxygen content of 0.2% by weight or less.
System alloy parts. 4. The Ti-A according to claim 1, wherein the alloy parts are exterior parts for watches and eyeglass frame parts.
g-based alloy parts.