JPS5834401B2 - Carbon sintering method - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in the method of sintering carbon raw material powder.

Sintering of carbon (graphite) can be performed using natural graphite-based coke that uses natural graphite as an aggregate, anthracite-based coke that uses coal such as anthracite and coking coal, coal-based coke, petroleum coke, coal pitch coke, etc. Various types of coke, such as oil coke based on carbon black, pitch coke based, and soot based based on carbon black, are used, and if necessary, binders such as coal tar, coal tar pitch, and resin are mixed. .

In the normal sintering method, after a long period of primary sintering at about 1000°C or less, the temperature is further raised to perform a long period of secondary sintering, which requires a long time and complicated processes and treatments. Ru.

Since the pitch of the binder has a large volatile content, it contains many air bubbles in the sintered body, resulting in a low sintered density and low mechanical strength such as bending strength.

The present invention was proposed in view of these drawbacks, and involves processing the raw material powder by applying electricity in a reduced pressure atmosphere during sintering to cause a glow discharge between the powders, and then heating and pressurizing the powder after the processing. It is characterized by being sintered.

A discharge sintering method in which electric current is passed between powders to generate a discharge is conventionally known, but this is performed at atmospheric pressure, or in some cases in a pressurized atmosphere.

The discharge in this case is an arc or spark discharge, and the discharge tends to be concentrated at - points, making it difficult to uniformly treat the entire sintered powder in a short time.

In this regard, the present invention allows discharge under reduced pressure, that is, glow discharge, so that the discharge path is expanded and the discharge treatment of the entire powder becomes extremely easy.

By performing glow discharge with the discharge path sufficiently expanded by controlling the pressure reduction and performing powder treatment, the discharge purification and activation process between the powders can be performed uniformly and efficiently. The generated volatile matter is easily removed from the sintered powder layer by the vacuum evacuation process, and the powders come into close contact with each other in a pure state. Therefore, sintering is caused by the diffusion bonding of these activated powders. It is possible to bond strongly with high density and increase mechanical strength.

The present invention will be explained below with reference to an embodiment of the drawings.

In FIG. 1, reference numeral 1 denotes a breathable mold, which is inserted into a vacuum evacuation container 2.

3 is a vacuum pump, and 4 and 5 are pressurizing punches inserted from the top and bottom of the mold 1. The punches 4 and 5 also serve as electrodes to connect a power source 6.

Reference numeral 7 denotes carbon powder as a sintering raw material filled between the punches 4 and 5 in the mold 1.

The mold 1 is made of an air-permeable, heat-resistant material such as a composite of fiber carbon, and is made of a porous material that allows the inside of the mold 1 to be easily evacuated by evacuation from a vacuum pump 3 in an evacuation container 2 .

The pressure reduction is usually 1 in consideration of the dispersibility of the glow discharge to be generated.
Exhaust is controlled to about ~50'l'orr.

The internally filled sintered powder 7 passes through the mold 1 by evacuation from the pump 3, and is controlled during the required depressurization, and is then energized from the power supply 6 through the upper and lower punches 4, 5 to be discharged, and the discharge is uniformly distributed throughout the powder. A glow discharge that spreads occurs.

The discharge current of the glow discharge is small, and this is controlled by the energizing source 6 to generate a stable glow discharge.

Due to the discharge, the surface of the powder 7 is subjected to discharge impact, and gases and impurities adhering to the surface are decomposed and evaporated, easily decomposed and scattered, and the surface is purified and activated.

At the same time, when a binder is added, its volatile content is easily decomposed and scattered, and the fixed carbon content is controlled to remain.

The decomposition and scattering of volatile matter is carried out through the mold 1, but since the mold 1 is breathable and the exhaust pressure is reduced by the pump 3, the decomposed and scattered substances easily pass through the vent holes of the mold. evacuated and therefore the discharge treatment effect is carried out easily and rapidly.

In this way, the powder 7 is activated, the impurities are decomposed, volatilized and removed, and when sufficient processing has been performed, the punches 4 and 5 are driven to pressurize and the power supplied by the current source 6 is increased. The glow discharge treatment improves the sinterability, and enhances the diffusion bonding effect due to electric field diffusion and thermal diffusion, making it possible to complete good sintering.

The processing time for the discharge is controlled by vacuum control at 1 to 50 Torr to perform glow discharge with good dispersion, so that the entire filled powder can be uniformly processed in a short time of usually about 1 to 60 seconds, and the sinterability is improved. Because the sintering effect is enhanced,
It was confirmed that the sintering time could be reduced to about 1/3 compared to that without any treatment in the same sintering process.

The crushed sintered powder can be sintered without the need for a binder.
For this reason, it was possible to significantly increase the density.

Fig. 2 shows an example of extrusion processing, where 8 is an extrusion die that also serves as a guide part, and a partially porous member 81.
2 and is configured to be air permeable, and is installed in a vacuum container 2.

Reference numeral 9 denotes a punch that fits into the die 8. Internal sintered powder 7 is extruded by the Calorie pressure of this punch 9, and a power source 6 is connected between the die 8 and the punch 9 to supply electricity.

By extrusion molding using this die, the sintered powder 7 can be treated with glow discharge under reduced pressure, and extrusion molding can be performed with improved sintering properties, and the finished product can be sintered with high density and high strength. Can be sintered.

As described above, in the present invention, carbon raw material powder is placed in an air-permeable mold, evacuated, and energized under reduced pressure to generate glow discharge with good dispersion. The process is stable, has a good dissipation effect for decomposed gas, etc., can be processed quickly and efficiently, and can significantly improve sinterability. By sintering this treated powder, sintering can be done in a short time. The resulting sintered body has high density and high strength.

To explain an example, 100 mesh powder of raw coke is filled into an air permeable carbon mold, and the mold is heated to 3 to 5 T in a vacuum container.
The sintered powder in the mold was treated by applying electricity from the punch while the pressure was reduced to about 0.05 to generate a glow discharge.

This discharge treatment is carried out for about 25 seconds and becomes 100 to 9/c111.
Pressure was applied.

After this treatment, the density of the sintered body was approximately 2.3 g/crA when sintering was carried out by heating at an electrical current of about 3.4 WH/9 and applying a pressure of 450 to 9/d. The compressive strength is approximately 2.
It was 1 ton/-.

For comparison, the maximum density of the sintered body obtained by the conventional method was about 2.1 g/c11t, and the compressive strength was about 1 ton/d. It has been found that a dense sintered body can be obtained.

Note that sintering is not limited to electrical sintering, and furnace heating sintering may of course be used as desired.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of a song. 1 is a mold, 2 is a vacuum container, 3 is a vacuum pump, 4.5 is a punch, 6 is a power source, 7 is a sintered powder, 8 is a die, and 9 is a punch.

Claims (1)

[Claims] 1. Filling raw carbon powder into an aeration mold or die,
The surrounding atmosphere of the mold or die is reduced in pressure, and a residue or an induced current is passed directly to the packed powder in the mold or die to cause glow discharge between the powders, and the treatment is performed by this glow discharge. A method for sintering carbon, which is characterized in that the carbon is sintered by applying pressure and heating after being sintered. 2. The carbon sintering method according to claim 1, wherein the atmospheric pressure is reduced to 1 to 50 Torr.