JPH1017904A - Energized sintering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an energized sintering method, by which the damage to a forming die is prevented and the forming die can be repeatedly be used for long time and the producing cost can be reduced. SOLUTION: This method charges powdery material M into the forming die 1 and compacted with a punch 2 to make a green compact, and the energized sintering is executed by impressing the voltage to the green compact through the punch 2 to obtain the sintered compact. In such a case, a sleeve 3 composed of a carbonaceous material is fitted to at least the surface contacting with the powdery material in the inner surface of the formed die and a plate 4 composed of the carbonaceous material is arranged on the end surface contacting with the powdery material M of the punch 2 to execute the formation of the green compact and the energized sintering of the green compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric sintering method, and more particularly to an electric sintering method capable of reducing the consumption of a molding die.

[0002]

2. Description of the Related Art Electric current sintering is an amorphous material in which the sintering characteristics such as ceramic composite materials including whiskers and fiber reinforced metal materials (FRM) and the high-temperature sintering characteristics are easily impaired. It has been attracting attention as a material that enables low-temperature sintering of electronic materials and electronic materials, and that can produce a functionally graded material having continuously changing properties in a short time and at low cost.

As shown in FIG. 7, the electric sintering is performed by inserting a molding die 1 into a sintering furnace (not shown) provided in a vacuum vessel (not shown). Punch 2
And the powder material M is charged into the forming die 1, and a load P is applied to the punch 2, for example, 100 to 700 kg / c.
This is performed by adding m ² , compressing the powder material M from above and below, and applying a voltage to the powder material M through the punch 1.

In electric current sintering, a forming die composed of a forming die and a punch plays an important role. However, since sintering is performed at a high temperature and a high pressure, the conventional structure shown in FIG. However, this is a cause of increasing the manufacturing cost of the sintered body quickly. That is, the forming die is made of carbon material, cemented carbide, etc., and the punch is also made of carbon material, cemented carbide, etc., especially when the forming die is made of carbon material. There is a problem that reaction or powder material of the raw material cuts into the pores of the mold made of carbon material, thereby speeding up the consumption of the mold, and in some cases, damaging the mold and making it impossible to use repeatedly. I have.

As a countermeasure, a heat-resistant sheet is formed by kneading a heat-resistant material powder with an adhesive such as a resin, and the heat-resistant sheet is attached to a sintering mold.
There has been proposed a method of protecting a mold by sintering to prevent adhesion and welding of a sintered body to the mold. (JP-A-60-33882)

However, in this method, the heat resistance of an adhesive such as a resin used is at most 400 to 500 ° C.
Therefore, sufficient protection cannot be given to the mold. That is, decomposition, gasification and carbonization occur at a temperature higher than this temperature, and softening at a transition temperature or higher even at a temperature lower than this temperature,
Flow occurs, and therefore, at a temperature of 1000 ° C. or higher, which is a temperature required for sintering ceramics and cemented carbide, the powder is softened in the heat-resistant sheet, and the adhesive component having fluidity tends to sinter. There are problems such as penetration into the body, carbonization and remaining in the sintered body, and gasification at a high temperature to generate bubbles in the sintered body.

At the same time, the adhesive component easily welds to the mold and is carbonized at a high temperature, so that it becomes a cohesive substance after sintering and cannot be separated from the mold, thus protecting the mold. Has the disadvantage that it has the opposite effect. Some adhesives decompose at high temperatures to generate gas, and the generated decomposed gas easily diffuses into the compact or sintered body and is adsorbed on the particle surface. Also, there is a problem that the sintering reaction is significantly inhibited.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems in electric power sintering, and has as its object to prevent sintering of raw material powders.
Electricity sintering that reduces the consumption of the forming die composed of the forming die and the punch, prevents damage, enables the forming die to be used repeatedly for a long time, and reduces the manufacturing cost of the sintered body It is to provide a method.

[0009]

According to the present invention, there is provided an electric current sintering method according to the present invention, in which a powdery material is charged into a molding die, compressed by a punch to form a green compact. A method of obtaining a sintered body by applying a voltage to the green compact through a punch to obtain a sintered body by applying a voltage through a punch, wherein a sleeve made of a carbon material is fitted on at least a surface of the molding die in contact with the powder material, and the punch is formed. The present invention is characterized in that a plate made of a carbon material is disposed on the front end surface in contact with the powder material, and the green compact is formed and the green compact is electrically sintered.

In addition, it is required that the sintered body be taken out of the forming die together with the sleeve and the plate after sintering, and that the sleeve and the plate made of a carbon material have a thickness of 0.5 to 5 mm. Features.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as shown in FIGS. 1 to 3, a sleeve 3 made of a carbon material such as graphite is fitted on the inner surface of a forming die 1. FIG. A plate 4 made of a carbon material is also provided on the tip surfaces of the punches (upper punch and lower punch) 2 and 2 that are in contact with the powder material M to be charged into the molding die 1. The compacting and sintering of the green compact are performed in a space surrounded by the sleeve 3 and the plate 4 made of a carbon material. FIG. 2 shows a forming die for obtaining a cylindrical sintered body, and FIG. 3 shows a forming die for manufacturing a rectangular cylindrical sintered body.

With this molding die configuration, the powder material M does not directly contact the molding die composed of the molding die 1 and the punches 2 and 2 during compression and sintering, so that the powder material M reacts with the molding die, Alternatively, wear and damage of the mold due to troubles such as the powder material M digging into the micropores of the mold can be avoided, and after sintering, the sintered body is removed from the sleeve 3 and the plate 4.
In addition, if the molding die is removed from the molding die 1, the molding die can be used repeatedly for a long period of time. In order to remove the sintered body from the mold, the sleeve 3 is preferably detachable from the molding die 1, and the plate 4 is preferably detachable from the punches 2, 2.

The sleeve made of carbon material is not necessarily the one shown in FIG.
As shown in (1), it is not necessary to fit the entire inner surface of the molding die 1, and the effect can be achieved if the inner surface of the molding die 1 is fitted at least on the surface in contact with the powder material M. FIG. 4 shows another embodiment of the sleeve fitting in the present invention, and FIGS.
3 shows an example of the arrangement of the sleeve 3 in the case of A, 1B, 1C, and 1D. 4 to 6, the sleeve 3 is fitted into a concave portion 5 formed on the inner surface of the forming die 1. Reference numeral 6 denotes a holder for the split die 1.

In the sintering operation, for example, when a molding die shown in FIG. 4 is used, the lower punch 2 is set inside a molding die 1 placed in a sintering furnace in a vacuum vessel.
A plate 4 is placed on the tip end surface of the mold, a sleeve 3 is fitted on the inner surface of the forming die 1, a predetermined amount of powder material M is charged, the plate 4 is placed, and the upper punch 2 is set, and a vacuum container is set. Is sealed, and the inside of the sintering furnace is evacuated by a vacuum pump, and an inert atmosphere gas is filled in the vacuum vessel as necessary.

Next, the punches 2 and 2 are operated to compress the powder material M in the forming die 1 with a compressive force P (for example, 100 to 700).
While pressing and compressing at a pressure of kg / cm ² ), a voltage is applied to the compact compacted at a high density through a punch, and the compact is heated to, for example, 1000 to 2000 ° C. to perform sintering.
After sintering, the sintered body is pulled out above the forming die, the sleeve 3 and the plates 4, 4 are removed, and the sintered body is taken out.

In the present invention, the sleeve and the plate made of the carbon material are arranged on the contact surface of the forming die with the powder material which is most susceptible to damage and the tip surface of the punch which comes into contact with the powder material. Since the compression molding and electric sintering of the powder material are performed in the space surrounded by the sleeve and the plate, the molding die and punch do not come into direct contact with the powder material, resulting from the reaction with the powder material. The resulting mold damage can be avoided. Therefore, by replacing only the sleeve and the plate for each sintering operation, the mold can be used repeatedly for a long period of time, and the number of times of replacing the mold can be reduced, so that the manufacturing cost can be reduced.

[0017] The sleeve and plate made of carbon material are used in consideration of cost and handling in addition to protection of the mold.
It is preferably formed to a thickness of 0.5 to 5 mm.
The selection is made according to the size of the sintered body to be manufactured, the type of the raw material powder, and the like. If the thickness is less than 0.5 mm, it is difficult to completely avoid damage due to welding, and if it exceeds 5 mm, it is disadvantageous in terms of cost, which is not preferable. Since the size of the sintered body can be changed by changing the thickness of the sleeve and the plate, it is also possible to reduce the types of forming dies prepared according to the size.

[0018]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 Using a mold shown in FIG. 4, an outer diameter of 45 mm, an inner diameter (diameter of a material charging portion) of 20 mm, a depth of a concave portion of 1 mm, and a length of 40 m
m and a cemented carbide (WC-C
o), a sleeve and a plate (both having a thickness of 2 mm) made of a carbon material are disposed on the inner surface of the forming die and the tip surface of the punch, and stainless steel (SUS304) powder and zirconia (ZrO ₂ ) Powder is mixed 3: 1 and charged into the material charging section of the forming die.
Compression molding with a pressure of 0 kg / cm ² ,
A current of 00 A was applied to raise the temperature to 1200 ° C.
By holding it for 0 seconds, it is electrically sintered and has a diameter of 20 mm.
A composite sintered body having a height of 10 mm was obtained.

After sintering, the sintered body was pulled out together with the sleeve and the plate above the forming die, and the sleeve and the plate were removed to take out the sintered body. A new sleeve and plate were placed again, and electric sintering was performed in the same manner. The same sintering operation was repeated 100 times, but no damage was caused on the inner surface of the forming die and the tip surface of the punch. , And could be used repeatedly.

Comparative Example 1 Without disposing a sleeve and a plate in a mold,
A forming die made of a carbon material having an outer diameter of 45 mm, an inner diameter of 20 mm and a length of 40 mm was combined with a punch made of a cemented carbide (WC-Co), and the same raw material powder as in Example 1 was charged into the forming die. Sintering was carried out under the same conditions as in Example 1 and the diameter was 2
A composite sintered body of 0 mm and a height of 10 mm was obtained. When the same sintering operation was repeated 10 times, damage of about 1 mm in depth due to biting of the raw material powder was found on the inner surface of the forming die, and it was necessary to replace the forming die.

[0021]

As described above, according to the present invention, without affecting the raw material powder, damage to the molding die composed of the molding die and the punch is prevented, and the molding die can be used repeatedly for a long period of time. Becomes Therefore, the number of times the mold is replaced is reduced, so that the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of an arrangement of a mold according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1 when the sintered body is cylindrical.

FIG. 3 is a cross-sectional view taken along line AA of FIG. 1 when the sintered body has a rectangular cylindrical shape.

FIG. 4 is a sectional view showing another embodiment of the arrangement of the molding dies in the present invention.

FIG. 5 is a sectional view showing still another embodiment of the arrangement of the molds according to the present invention.

FIG. 6 is a sectional view taken along line BB of FIG. 5;

FIG. 7 is a cross-sectional view showing an arrangement of a conventional molding die.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding die 2 Punch 3 Sleeve 4 Plate 5 Concave part 6 Split molding die holder M Powder material

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideo Ando One of 594 Akahira, Akabira-shi, Hokkaido Sumitomo Stone Coal Mining Co., Ltd. Hokkaido Technical Research Institute (72) Inventor Shigeru Matsui 3--20 Nishishinbashi, Minato-ku, Tokyo No. 4 Sumitomo Stone Coal Mining Co., Ltd.

Claims (3)

[Claims] 1. A powder material is charged into a molding die, compressed by a punch to form a green compact, and a voltage is applied to the green compact through a punch to sinter the current to form a sintered body. In the obtaining method, a sleeve made of a carbon material is fitted on at least a surface of the molding die which is in contact with the powder material, and a plate made of the carbon material is arranged on a tip surface of the punch which is in contact with the powder material, and a green compact is formed. A discharge plasma sintering method characterized by performing molding and sintering of a green compact. 2. The method according to claim 1, wherein after sintering, the sintered body is taken out of the forming die together with the sleeve and the plate. 3. The electric current sintering method according to claim 1, wherein the sleeve and the plate made of a carbon material have a thickness of 0.5 to 5 mm.