JPS5888180A - Treated matter containing structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an object storage structure, and more specifically to a seal in a hot isostatic pressing process for ceramics using a pressurized gas, in which low softening point glass is melted and the glass is used as a sealing material for molding ceramics to be treated. The present invention relates to a processing object storage and combination structure with improved properties.

The hot isostatic pressing (hereinafter abbreviated as HIP) process that uses glass as a sealing material allows for irregular shapes, and can be HUPed even at high temperatures that cannot be used with copper, steel, etc., which are normally used as encapsulants. It has been attempted to be applied to the densification treatment of ceramics, which has recently been developed as a high-temperature strength structural material, and the glass capsule method (Bf!
6-2" No. 31) and a method of embedding a molded body in glass powder (see Japanese Patent Laid-Open No. 55-89405).

In each of these methods, a carbon crucible such as a graphite crucible is usually used, and the glass is melted in the crucible to surround the molded object to be processed. However, the sintering temperature of ceramic powder is relatively low. Higher H compared to conventional metal powder molding
When processing ceramics such as silicon nitride and silicon carbide using glass with a low softening point, since a high temperature is required for the process, both the glass encapsulation method and the glass powder embedding method are the same. In this way, the ceramic molded body to be treated is immersed in the glass bath. However, the specific gravity of a ceramic molded body is 1.8 to 2 until it reaches high density.
．． 12/m3 and specific gravity of glass 2.2-2, 397m”
If the glass is smaller and the glass is melted as described above, the molded body will float up from the installation location, become more likely to move, and come into contact with the carbon crucible.

In this case, since the crucible has air permeability to allow the pressurized gas to pass through, when the object to be processed comes into contact with the carbon crucible,
The gas used as the Hxp treatment pressure medium enters through the contact area, resulting in incomplete hepato-kidney sealing and HI
The purpose of P cannot be fully achieved. This also induces a reaction between a trace amount of acid accumulation contained in the pressure medium gas and the ceramic. Furthermore, it has been considered to attach BN powder as a mold release agent to the inside of the carbon crucible, but even with this method, it is difficult to solidify the glass after treatment and then take it out from the carbon crucible.

However, even though it has the above-mentioned disadvantages, glass with a low softening point has many advantages such as ease of handling and low price, and its use is industrially advantageous. It is equally desirable to improve the

The present invention, in response to the demands of the times, provides a processing object storage structure having an improved sealing structure that can more effectively achieve sealing with low softening point glass by overcoming the above-mentioned drawbacks. The purpose is to provide

The feature of the present invention that achieves such an object is that in the crucible for storing the processed material loaded into the H-P apparatus, the processed material and the glass sealing material surrounding the processed material are stored, and the The object and the glass sealing material are further wrapped in a flexible and non-porous graphite foil or sheet, and a weight is placed on the top surface of the sheet so as to be freely movable. .

Hereinafter, specific embodiments of the present invention will be further described in detail based on examples shown in the accompanying drawings.

The figure shows an example of the object storage structure of the present invention, and shows a V% crucible (1
), the object to be processed (2) is placed between the glass plates (31 (3) above and below it).
1' and an intermediate glass powder granule (4).
) and glass (31(3)'(4)), there is an air-impermeable material that surrounds the entire surface of the object to be treated (2) and glass (31(31'(4)) and forms the essential part of the present invention. , and a flexible graphite foil or sheet (51) is provided on the top surface of the graphite foil or sheet (51).
) is mounted so as to be freely movable.

Among these, the crucible (1) has air permeability to allow pressure medium gases such as Ar and N1 to permeate during HIP, and a carbon crucible is usually used.

On the other hand, the object to be treated (2) includes all materials to be subjected to HIP treatment, such as metal or ceramic powder, but the HIP method, which uses glass as a sealing material, is suitable for high-temperature treatment and is suitable for H-P treatment of ceramics. For this reason, ceramic materials are particularly effective, and ceramics containing silicon nitride, silicon carbide, or boron carbide as a main component, especially ceramics containing silicon nitride as a main component, are the most preferred and are the materials to be used in the present invention. It is the mainstream of processed materials. The object to be treated (2) is usually not a powder, but is formed into a preformed body containing or not containing a known sintering aid, or a presintered body obtained by presintering the same.

The glass used for the seal can be any glass normally used for H-P treatment, such as silica glass, biful glass, or Pyrex glass. Pyrex glass is generally chosen as the most practical because of its ease of removal. In the figure, this sealing glass is composed of the upper and lower glass plates (31 (31') and the intermediate glass powder (4), but it is not installed separately or in combination with the glass powder (4). It may be used alone, or it may be encapsulated in a glass capsule. However, the arrangement shown in the figure is the most suitable in terms of the assembly arrangement within the crucible, even though the form may vary. Note that the glass is condition,
In addition to the granular shape, various shapes can be used.

Next, the graphite foil or sheet (5) which forms the main part of the present invention
The surrounding area prevents the intrusion of pressurized gas from passing through the crucible (11), which has air permeability, and also accurately transmits the isotropic compressive force during H3P to the workpiece (2). It is particularly useful in the J (IP) process, which utilizes a medium gas, and must be non-porous and flexible to cope with compressive deformation.Moreover, during the H/P process, if it is melted, it will not function as described above. Naturally, it is required to be insoluble during H-P treatment.

Note that materials that satisfy this function are not limited to graphite, but also foils and sheets made of high-melting point metals such as molybdenum.
All of them are disadvantageous in terms of cost, but graphite foil or sheet-like products known by the trade name Graphoil are also useful. In particular, this graphite foil or sheet f5] also has a role as a mold release material, and after treatment, the glass solidified thereon can be easily taken out from the crucible.

Furthermore, in the above-mentioned configuration, the air impermeability of graphite7. A weight (6) is placed on the upper surface of the object to be processed (2) and the seal glass f31 f31' (4) surrounded by a foil or sheet (5). It is designed to suppress the floating of the object to be processed (2) that floats up when glass is melted, and if it is made of a high-temperature material and is heavy enough to suppress the floating of the object to be processed, which has a specific gravity smaller than that of glass. For example, silicon nitride, tungsten, molybdenum, etc. may be used. This weight (6) needs to move freely in the direction along the inner wall surface of the crucible to accommodate deformation during processing, and a load is applied to the object to be processed and the graphite sheet or foil on the top surface of the glass. That's how it is.

In the figure, (7) indicates B sprayed or applied inside the crucible.
The mold release agent layer is made of N powder, and although it is not particularly essential, it goes without saying that, together with the mold release effect of the graphite foil or sheet, it facilitates removal after processing.

The object storage structure of the present invention has the structure as described above, and is mainly used for H-process P processing using gases such as Ar, N, etc. as the pressure medium, and is installed in the H-process P furnace in this form. However, in the H-process P treatment, the temperature is raised first, and then the temperature is increased because the gas remaining in the object to be treated is not trapped, and the pressure is applied after the glass seal is completed. , it is common to reach a predetermined temperature, then increase the pressure and further increase the temperature. Therefore, when Pyrex glass is used as the glass, it softens and melts when the temperature exceeds 1200°C, and the workpiece that has not yet been densified floats to the surface due to its light specific gravity, pushing up the non-porous graphite foil or sheet above. A part of the material to be treated floats up from the glass bath.

However, at this time, since the weight (6) is present above, this floating can be suppressed and the intrusion of gas, which is a pressure medium, can be prevented, and a complete sealing state can be maintained.

Note that the gas released from the object to be treated [at the initial stage of H-P, the glass seal is not yet completed, so the gas flows out through the gaps between the glasses.

After the glass is melted, the Pyrex glass has the function of dissolving the gas, so it is dissolved into the glass, and the object to be processed can achieve high density under the required HIF temperature and pressure. After the treatment, the gas dissolved in the glass is vaporized again, making the glass foamy and making it easier to remove the glass.

Thus, the structure of the present invention not only prevents pressure medium gas from entering the workpiece by surrounding the workpiece with an air-impermeable graphite foil or sheet and placing a weight on top, but also prevents pressure medium gas from entering the workpiece. Even if the object to be treated tends to float up during the process, which is a problem in the P process, it can be pressed down with a weight and the seal can be made perfect, combined with its non-porous property.

Moreover, the graphite foil or sheet in the present invention has flexibility and does not inhibit the densification of the processed material in any way, and also has an effect as a mold release agent, so that it can easily remove glass solidified from a carbon crucible. It is also extremely effective in removing
This method is highly effective in producing high-density ceramic sintered bodies based on the basic principle of H-P processing, which states that gas as a pressure medium must not be allowed to enter the workpiece. .

Examples of the present invention will be further described below.

(Example) Si with purity 99%, α phase 70%, average grain size line 1 μm,
N.Pour the powder into a silicone rubber tube and close the stopper.5
Perform isostatic pressing at a pressure of 0005a to obtain a relative density of 58%.
A preformed body (approximately 18wφ×30■t) was prepared.

This preformed body was buried in a graphite crucible whose inner surface was coated with 1 kBN, and the entire surface was surrounded by graphite foil in a ratio state. A weight was placed on it and it was loaded into the H-P equipment. After heating the inside of the H-P equipment to 300° C. and evacuating it to about 1 Q Torr, 15 tons of N2 gas was injected, exhaust operation was performed twice, and 30 tons of N and gas were injected. As is 1
After heating up to 200℃ to soften and melt the glass, N2
While replenishing gas, the temperature was further increased to l'750℃, 20
HIP processing was performed for about 2 hours using one 00 machine.

The molded body taken out from the HIP device was entirely covered with dark glass, but when the graphite foil and glass were removed, the Si and N4 surfaces were clean with no trace of pressure gas intrusion. And its relative density is 98
．． It was 5%.

[Brief explanation of the drawing]

The figure is a schematic cross-sectional view showing one example of a processing object storage structure according to the present invention. (1)... Crucible, (2)... Processing object. (31 (31'... Glass plate, (4)... Glass powder granule. (5)... Graphite foil or sheet), (61... Weight. (7)... BN release material. Molding agent layer.

Claims (1)

[Scope of Claims] / A structure comprising a ceramic molded body to be treated by hot isostatic pressing in a crucible having air permeability, wherein the molded body to be treated is The entire surface is surrounded by a flexible non-porous graphite foil or sheet together with the sealing material glass, and a weight is placed on the top surface of the non-porous graphite foil or sheet. A processing object storage structure characterized by: 2. The processed material storage structure according to claim 1, wherein the crucible having air permeability is a carbon crucible. 3. The object storage structure according to claim 1 or 2, wherein the ceramic molded object to be treated is a molded object containing silicon nitride as a main component. j The storage of the processed object according to claim 1, 2 or 3, in which the entire surface of the molded object is surrounded by upper and lower glass plates and glass powder filled between them. Structure. The object storage structure according to claim 1 or 4, wherein the S glass is Pyrex glass.