JPS616180A - Thermal hydrostatic pressure treatment for ceramic - 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 (Industrial Application Field) The present invention densifies a ceramic powder compact by hot isostatic processing (hereinafter referred to as II Process), thereby forming a product with excellent quality and performance. The present invention relates to a method for obtaining a ceramic body, particularly a method in which a hard-to-sinter ceramic powder such as silicon nitride or a molded body thereof is glass-sealed and then subjected to HIP treatment.

I Prior Art) The H-P process compresses the object isotropically using an inert gas as a pressurized medium under high temperature. It is a technique that is becoming widely used and is known as an excellent method for manufacturing sintered bodies, crushing and removing residual pores in cemented carbide, or diffusion bonding metal materials. On the other hand, ceramic molded products, which have recently been in the spotlight as having suitable performance for structural materials, were traditionally made through a complicated manufacturing process, but with the advent of the H4F method, the production The process has been significantly simplified, and at the same time, the properties of the molded products have been greatly improved and their variations have been reduced.

The methods used for sintering HIP'i ceramics can be roughly divided into: (1) Filling and sealing the entire raw material powder or compact into a capsule, performing an appropriate gas sealing process, and then sintering it in the HIP'i P equipment. Using a method of heating and pressurizing, and (2) a suitable sintering method in advance, a sintered body with a density of around 95% of the theoretical density ratio and closed pores is made, and this is then subjected to HIP as it is.
There are two types of processing methods.

Of the above, the latter method not only has the disadvantage of requiring a step of manufacturing a pre-sintered body, but also has the disadvantage that the sintering aid added therein may deteriorate the high-temperature properties of the HIP-treated ceramic molded product. This can be said to be a fatal problem, especially in silicon nitride ceramics, which often require strength under high temperatures.

On the other hand, the former method does not require the step of making the pores closed by preliminary sintering, and therefore the product is not adversely affected by the sintering aid, but on the other hand, it requires pretreatment of forming a seal on the raw material powder or the compact. Therefore, it can be said that the seal forming technology is the key to determining the performance and quality of ceramic molded products.

In general, the seal of the raw material molded body plays the role of preventing gas, which is a pressure medium, from penetrating into the interior during HIP processing, and at the same time serves as a pressure transmission medium that applies static water [E] to the molded body due to the pressure medium gas. Therefore, it is desirable that the material be one that maintains sufficient airtightness under heating and pressure, exhibits appropriate plasticity, and can be easily removed from the molded product in the final stage.

Iron, molybdenum as such sealing materials.

Various metals such as nickel, platinum, tantalum, titanium, etc. are used, but ceramics, especially 17
Glass is a difficult-to-sinter material that requires high-temperature HIF conditions of 00°C to 2000°C, and is one of the best sealing materials for producing molded products with complex shapes. , and it is also advantageous for economic punishment, so its HIP
Research has been carried out on pots for their application as sealing materials in manufacturing processes.

For example, Japanese Patent Application Laid-Open No. 51-100913 discloses a HIP casting method for ceramics such as silicon nitride, in which a ceramic powder preform is embedded in high silica glass powder with a high softening temperature. Furthermore, a so-called glass capsule method is disclosed in which the material is housed in a glass capsule having a relatively low softening temperature, sealed for evacuation, and then subjected to H-P treatment. With this method, pressure is applied when the glass capsule reaches a temperature at which it can be plastically deformed during HIP treatment, and an airtight layer is formed on the outer layer of the 1°, 5 silica glass before the capsule is washed away. When the temperature and pressure are further increased by 4 degrees, complicated and delicate conditions must be set, and there is still a problem in that it is difficult to ensure that the seal is formed. In addition, if the preform has a complicated shape and is large, it is difficult to manufacture and process a glass capsule corresponding to the preform.

Furthermore, Japanese Patent Application Laid-Open No. 54-144413 discloses a method in which a glass porous layer is provided on the surface of a preformed product by immersing a silicon nitride element-equipped molded product in an aqueous suspension of high silica glass powder. 1. A so-called sintered glass method has been proposed in which a glass porous layer is sintered by the high temperature during the HIP treatment and a casing is formed. but,
In this method, drying cracks due to the low strength of the gas porous layer and cracks due to shrinkage of the glass porous layer during sintering are likely to occur, and the formation of a complete gas seal required for I (1F processing is difficult). , is quite difficult.

Furthermore, JP-A No. 52-58714 discloses that a heat-resistant container is filled with a glass powder having a low softening temperature such as Pyrex glass, and a molded body such as ceramics is embedded in the glass powder. The so-called glass bath method is described, in which the temperature is raised while degassing in a high vacuum to form a molded body covered with molten glass, and the entire body is subjected to 1HIP treatment. However, with this method, pie! /t3/7. ■Ka' 77. (Na2OK2Oaz,
o3B. . 3-3in2) or soda glass (Na2
Forming a seal is easy because glass with a low softening temperature, such as Ocao A1403-3in, is used.
1600-200, which is the HIP processing temperature for ceramics.
At a high temperature of 01:, Na2O, K2O, B
The evaporation of components such as 2O3 is significant, and the ceramic molded body is contaminated with these components and its performance deteriorates. In particular, Na2
O+K2O.

'11203, Si3N contaminated with OaO etc.
, Inc., 1=, o -Sin2. at the grain boundary. CaO-Si0
The strength of Si3N and ceramics as high-temperature structural materials is lost as a result of the glass powder layer having a low softening temperature such as No. Furthermore, as shown in the attached drawings and the schematic explanatory diagram of FIG. In addition, if the glass (3) is Pyrex glass, that is, a material with a low softening temperature such as borosilicate glass, the airtight glass layer (4) can be easily formed and the ceramic molding 44 (3) can be completely completed. However, in this case, not only is the above-mentioned contamination caused, but also the molten glass, whose viscosity has significantly decreased in the B1P pressurization process, enters the pores of the molded body and is not sufficiently densified. is not achieved. If glass with a high softening temperature is used to solve the problem 7″L, as shown in Figure 6, although the glass powder layer (2) softens and fuses and shrinks due to IJO heat, the internal molding Since the body (3) does not shrink, cracks (5) may occur in the glass layer (4) due to shrinkage as shown in figure (0), and a complete seal may not be obtained.
This is particularly noticeable in the case of highly softened glass used when high temperatures of 1700°C or higher are required, such as HIP molding of Si3N4, and when silica glass is used, the glass layer (
Even if the thickness is considerably increased to 4), the temperature will reach 11,700℃.
This is unavoidable at seal forming processing temperatures below.

In addition, there is a so-called coating method in which the surface of the raw material powder compact is coated with alumina, etc. by thermal spraying, but the thermal spray coating layer is easy to peel off. This method cannot be used as a sealing method for powder compacts.

(Problems to be solved and attempted by the invention) The present inventors have solved the problem of ceramics HIP +Jt+ +
:E processing, in order to solve the various problems and difficulties of the prior art, (1) [
As a result of repeated research, we have arrived at the present invention.

That is, the object of the present invention is to provide a high-quality ceramic molded body which is densified to a density of at least 99% relative to the theoretical density and has no performance deterioration or damage due to impurity contamination. be. Another lfl objective is to obtain a high-strength and homogeneous structural material with exceptionally excellent high-temperature properties from hard-to-sinter ceramics, especially Si3N4 powder or its pre-sintered body.

Another purpose is to use high silica glass, which has a softening temperature of 1.5 degrees, as a gas sealing material to provide a simple, easy, reliable, and complete seal, even on ceramic molded bodies with complex shapes and large dimensions. The object of the present invention is to provide a series of excellent methods for easily releasing a glass seal from a mold by carrying out HII) treatment without damaging the molded product. Other features will be easily understood from the following description.

(Means for solving the problem) However, in the above +1, a ceramic molded body is embedded in high silica glass powder filled in a heat-resistant mold, and the viscosity of the glass is about 1010 t'Is or more. This is achieved by subjecting the ceramic molded body to hot pressing to form a gas sealing layer around the ceramic molded body, and subjecting the ceramic molded body covered with the gas sealing layer to an expansion isostatic pressure treatment.

The ceramic to which the method of the present invention is applied is Si3N
4, SiO, BN, TiN, Tic, A
t2o3, etc. are heat-resistant ceramics containing at least one of them as a main component, and 813N4 is especially important because of its excellent high-temperature properties and high strength, which has high utility as a raw material for heat-resistant structural materials. It is. Therefore, in describing the present invention in detail below, SiaN4' will be used as a representative example of ceramics.

The above-mentioned ceramic is applied to the method of the present invention as a molded body. Such a molded body is produced, for example, by placing Lamics powder in a soft capsule, such as a rubber-lined plastic capsule, and isotropically compressing it by applying hydraulic pressure from the surrounding area. Static press (cI
It is molded by a conventional molding method such as injection molding, extrusion molding, or a known method called p), and further processed into a desired shape by mechanical grinding or the like as necessary. Further, for the purpose of strengthening the compact, preliminary firing may be performed before sealing.

Particularly in the case of a molded body having a complicated shape, it is preferable to perform primary firing, since chipping may occur in a green molded body. In this case, primary sintering is usually performed at 300°C or less, because sufficient strengthening purposes cannot be achieved at temperatures below 1400°C, and grain growth occurs at temperatures above 2000°C, reducing the strength of the sintered body after HIP.
．． It is preferable to carry out the reaction at a temperature of 400°C to 2000°C without adding any auxiliary agent.

However, at temperatures below 1800°C, it is possible to use N21 atmosphere, but at 1800 to 20°C, it is necessary to use a N2 pressurized atmosphere. Especially S i 3 N. For example, at 1800°C, use N, 5K atmosphere to suppress decomposition.

At 2000°C, it is difficult to create an atmosphere of N230 atm.

Further, a firing time of about 15 to 60 minutes is sufficient, and no matter how long the firing time is, the same holds true.

The density of the primary fired body is 1400 to 485.
Up to 0°C, there is no difference from the produced form, for example, 62°C → 62%, but there is a slight increase at 19°C to 200°C, and it becomes 62% - → 65%. and I″L, the primary firing only produces weak bonds at the contact points of the particles and does not cause shrinkage of the entire molded body, so even though the strength increases, there is almost no change in density.

If the primary firing is performed in this manner, it is easy to handle and does not crumble, making it possible to add more strength and speed up sealing.

Thus, the ceramic molded body in the present invention includes not only the raw molded body molded into the desired shape, but also the molded body that has been subjected to primary firing as described above.

(Detailed Description of the Invention) Specific embodiments of the method of the present invention will be further explained with reference to the accompanying drawings.

FIG. 1 is an explanatory diagram showing the steps of the method of the present invention.

FIG. 2 is a diagram showing the change in viscosity of extrapolated glass with respect to temperature.

FIG. 3 is a schematic diagram showing a preferred embodiment of the method of the invention.

FIS diagram 4 is a diagram showing a program pattern of the HIP pressurization process of the method of the present invention.

In FIG. 1, the ceramic molded bodies (3) of Si3N4 or the like having various shapes as shown in (D) are first prepared by (
As shown in E), it is placed into a heat-resistant mold (6).

At this time, the ceramic molded body (3) is embedded in the high silica glass powder (7) filled in the mold (6).

The mold (6) is made of a hard material, such as black ship, which can sufficiently withstand at least the softening temperature of the high silica glass powder (7) to be filled.

Also, high silica glass includes at least 96% Si by weight.
Typical examples thereof include silica glass consisting essentially of 100% Si02 and Vycor 0 glass having a composition of 96.7% by weight of Si02 and 304% by weight of B20.

Such glass retains Na2O, K2O, and Oak even at the temperatures required for HIP pressure treatment of ceramic molded bodies, that is, at high temperatures of 1,600 to 2,000°C.

There is virtually no evaporation of components such as B2O3, and Si3
No contamination of N4.

As mentioned above, the ceramino cut molded body (3), which is embedded in the high silica glass powder (7) and charged into the heat-resistant mold (6), is then subjected to hot pressing.

In hot pressing, the high silica glass powder (7) is first heated by a heating means such as direct heating or induction heating using a heating element (8) to a temperature at which plastic deformation can occur, and then heated by an appropriate means such as hydraulic pressure. The actuated bracelet (9) applies the upper and lower pressures of the mold (6) to densify the glass powder and form a gas-sealing layer of glass around the ceramic compact.

In order to cause plastic deformation of glass powder, its viscosity [η
] Approximately 1010 boys, approximately 109°5
Must be less than poise.

As shown in Fig. 2, the temperature at which [η]≦1010 voices is approximately 1300c or higher in the case of silica glass,
In the case of Vycor 0 glass, the temperature is about 1150°C or higher.

In addition, the crystallinity of [η) sl O''5 voids is approximately 13JO℃ or higher for the former, and approximately 1250℃ or higher for the latter.
When the value of [η] exceeds approximately 1o10 voids, it is difficult to plastically deform, and it is difficult to form a dense gas sealing layer, which leads to not only the formation of a dense gas sealing layer but also the fact that hydrostatic force does not act on the ceramic molded body (3). The molded body (3) may be damaged. In order to prevent damage, the higher the temperature so that [η] is sufficiently small, the better. 'However, 513N4 causes thermal decomposition when heated to about 1800°C, so if the ceramic is Si3N4, the heating temperature should be about 1800°C or lower. In the case of ceramics that do not undergo thermal decomposition, the temperature may be lower than that, but practically it is preferably about 100°C or lower. Also, care must be taken because if [η] is too small, the molten glass may leak out from the gaps in the mold.

The hot press pressurizes the high silica glass powder (7)d to prevent shrinkage cracks caused by heating and densification, completely covering the circumferential recesses of the ceramic molded body (3) with the densified glass layer,
It plays an important role in completing the gas seal layer. Add [f:
, the breath [E is preferably 1 to 100]. If it is in this range, even if the press pressure is low, [η] is small or -! The densification becomes sufficient if time is spent.

However, if too much time is spent, the glass powder may cause crystallization, so if the temperature is low,
In particular, a press IF with 5 or more views is desirable. There is no particular upper limit to the press pressure, but 100η is sufficient; sudden application of high pressure may damage the ceramic molded body (although primary firing can prevent this to some extent). Therefore, it is undesirable.

The pressurizing operation is continued until the glass powder becomes densified, the shrinkage of the glass layer is completed, and the movement of the Bresler plate (9) stops, which takes about 15 to 30 minutes. The time required for densification, ie, the sintering rate, is also related to the particle size of the glass powder. The finer the particle size, the better the sinterability, that is, the sealing property.The average particle size of the glass powder is preferably about 1 fl or less, and if it is 0.1 mm or less, the sintering speed will be poor.

If a gas sealing layer is formed using Hondobu 1/S according to the method of the present invention, even if the glass has a high softening temperature such as silica glass, it will be possible to compensate for the shrinkage of the glass powder layer by applying pressure. without causing shrinkage cracks in the glass phase.
Sufficient, reliable and complete gas sealing is possible at a temperature of about 1400°C.

1 (E
), the ceramic molded body (3
) and the adsorbed gas on the surface of the silica glass powder (7) are removed, which is desirable. That is, the suction pipe (13) of the casing (B) that airtightly houses the hot press device is connected to a vacuum pump (not shown), and the vacuum chamber (11) is preferably kept in a vacuum state below lo'maHf. It is. In addition to such a vacuum, it is also possible to use an inert gas atmosphere such as nitrogen gas or argon gas. Since the layer may be destroyed, it is necessary to apply a HIP pressure corresponding to the internal pressure in advance, and the operation becomes complicated, so it is not recommended.

In addition, in order to prevent hot-pressed ceramic molded bodies such as A3144 from reacting with the glass layer during the HIP process, BN, or boronite-rich powder, is placed between the gas seal layer and the ceramic molded body. It is highly preferable to intervene. As shown in FIG.
The state (H) in which BN powder 0→ is coated on the surface of 3) to a thickness of about 2 cm or more, preferably about 3 m or more, is embedded in the high silica glass powder (7) e. (,T). The intervening BN powder is also
It acts as a solid secondary medium to transmit more hydrostatic pressure to the ceramic molded body, and in particular, in order to have such an effect on a molded body with a complicated shape, B
It is preferred that the coating thickness of the N powder be approximately 31 IoI+ or more.

If the coating thickness is too small, part of the ceramic molded body may come out due to deformation of the EN layer during hot pressing, come into contact with the glass, and a reaction between the two may occur at the interface, resulting in loss of product value. In addition, in the case of a molded body having a complex shape, a raw molded body that has not been primarily fired may be chipped or damaged due to non-hydrostatic stress components during hot pressing.

As shown in FIG. (
6) and subjected to HIF pressure treatment.

HIP Kada treatment produces a gas-sealed molded body (3),
It is embedded in a heat-resistant support material (16), for example, BN powder, and placed in a heat-resistant crucible 07), for example, a Kurofune crucible. The process is carried out by charging into a known HIP apparatus (G) consisting of a pressure-tight sealed container (A) having a medium gas introduction hole (19).

The heating and pressurizing conditions are set in an appropriate program depending on the physical properties of the glass of the gas seal layer α5), the type of the ceramic molded body (3), and the like.

FIG. 4 shows a specific example of a processing program and pattern for performing HIP Kada treatment on a Si3N4 molded body covered with a gas sealing layer made of silica glass.

In this pattern, when the temperature is raised at low pressure as in the first temperature raising process, it is desirable to apply an initial pressure of at least about I MPa in order to maintain the furnace body during normal HIP charging. Therefore, when performing the HIP treatment on a ceramic molded body to form a glass seal, pressure is applied during the heating and softening process of the glass, so deformation begins at a temperature considerably lower than the softening temperature of the glass. . In this case, differences in deformation speed in each part of the gas seal layer tend to occur, and non-hydrostatic pressure acts on the ceramic molded body, resulting in damage to the ceramic molded body. In order to prevent this, in this case, BN powder 4 is interposed as a secondary royal medium between the ceramic molded body and the gas seal layer, so that the non-hydrostatic force due to the deformation of the gas seal layer acts directly on the ceramic molded body. It is necessary to configure the structure to avoid this.

HIP for ceramics, which is usually the most commonly adopted
The processing conditions are a temperature of about 1600 to 2000°C, preferably 1700 to 1800°C, and an IF force of about 10 MPa or more, preferably 50 MPa or more, and it takes about 2 hours to achieve this treatment condition. , the pressure was increased and the conditions were maintained for about 0.5 to 2 hours to achieve densification, and then the temperature was lowered for about 2 hours.

It goes without saying that these conditions can be varied in various ways depending on the installation of the preheating furnace, the devising the structure of the HIP device, the type of ceramic M, f'J:U molding conditions, etc.

Removal of the glass sealing layer after HXP processing can be done relatively easily, for example, by shot peening using alumina as an abrasive.

” By the two-stage method of the present invention, non-sintering ceramics,
For example, Si and N4 have a density with a theoretical density ratio of at least 99, have no performance deterioration due to contamination of the gas seal layer with glass, and have extremely excellent high-temperature properties f), and have a high strength and homogeneous structure. Becomes a material.

(Refreshing example) Embodiments of the present invention will be described below.

Example 1 Si3N4 powder with an average particle size of 0.5 μm was filled into a disk-shaped rubber capsule without adding a sintering aid, and 500 M
Isostatic pressure molding was performed at a pressure of Pa for 10 minutes.

The obtained preform was cut to 3cP″×45α
A blade-shaped molded body of X5α′ was obtained. This had a density of 63% of theoretical density.

BN powder with an average particle size of μ on the entire surface of the blade-shaped compact f3
It was applied to a thickness of mi. The above-mentioned BNN coated disk-shaped compacts were embedded in silica glass powder having a particle size of 325 mesh or less, and then placed in the black ship type (6) of the hot press machine shown in No. 11A(E). Filled. The inside of the vacuum chamber (11) was heated at lo2mz) (rmeijo 11mo) while removing the gas trapped on the surfaces of the compact, BN powder, and glass powder.The temperature reached approximately >-400°C. By the way, the hydraulic system was activated (7,5) to perform hot pressing with this 1rE force.The press ram stopped after about 25 minutes of application time, so the vacuum chamber (II)
and cooled. The obtained gas seal layer had no cracks at all, was sufficiently dense, and formed a perfectly solid body, and the molded product was 11 times thinner with no damage observed.

, this block was buried in the same BN powder as above and placed in a graphite crucible, and the HI process was performed as shown in Figure 1 (G).
The H: Executed tp7JOIt processing.] It took about 2 hours to lower the pressure and temperature, and then the object to be treated was taken out. The glass seal layer could be easily removed by shot beaning with Lumina tilt abrasive.

The obtained 513N, l sintered body had a density of 99% of the theoretical density, and a bending strength value of 50 at room temperature.

simple The weight was 55 kg at 1200°C.

Example 2 Hot press conditions were as follows: temperature: 1350°C, power:
lO%7. Pressure 1: Time: Approximately 20 minutes.
Same as 1 ('1), pot breath and U Hi p pressure treatment were performed, and high density s1, N4 with similar excellent properties were
In a sintered body? 0.

Example 3 The hot press conditions were: temperature q: l 400'C;
[-t=crab 1O%, added] (2 hours: about 15 minutes, but the same method as in the example]) Hot press and heat Hs
P Pressure treated high-density Si with similar excellent properties
3N.

A sintered body was obtained.

Seven comparative examples 1 The hot pressing conditions were: temperature: 1290°C, ti:.

Hot pressing was carried out in the same manner as in Example 1, except that the glass powder was 10ζ and the processing time was 30 minutes. However, the glass powder was not densified, the sealing properties were poor, and HIF treatment was not possible.

Comparative Example 2 Hot press conditions: temperature: 1350°C, power: zoog
Although a gas sealing layer with good sealing properties was formed when hot pressing was performed in the same manner as in Example 1, except that the pressurization time was 2 minutes, excessive pressure was applied suddenly. The molded article was damaged due to the strain.

Comparative Example 3 A Si, N, molded body was embedded in silica glass powder without applying BN powder, and real press conditions were used at temperature: 140
0°C, pressure crab 200-, and 10 hours.
When hot pressing was performed in the same manner as in Example 1, a gas sealing layer with good sealing properties was formed, but the molded body was damaged due to the rapid application of excessive pressure.

Comparative Example 4 Hot press conditions were wet/i: ] 350°C, 11
: Example 1 except that the force was 0.9-9 and the pressurization time was 45 minutes.
When hot pressing was performed in the same manner as above, the glass crystallized and a good sealing layer could not be obtained.

Example 4 Si3N4 powder with an average particle size of 0.3μ was filled into a polyurethane capsule without adding a sintering aid, and C
IP molding was performed to obtain a molded product having the complex shape (a) shown in FIG. 1 (CD) and weighing 1567. The density of the material was 62% of the theoretical density. BN powder having an average particle size of 1 μm was applied to the entire surface of this compact to a thickness of about 3 fins. The mixture was embedded in a vial of glass powder with a particle size of 200 to 325 mm, and then placed in a graphite mold, which was then placed in a hot press machine as shown in FIG. 1(E).

The inside of the vacuum chamber (11) was reduced to a degree of vacuum of 10-'yunHr to remove the gas adsorbed on the surfaces of the compact, BN powder, and glass powder while processing. The temperature is about 1300
When the temperature reached °C, the hydraulic system was activated and real pressing was performed at a pressure of 10%. 1 during processing? Since the press ram was found to have stopped after approximately 15 minutes, the vacuum chamber (7) was returned to normal pressure and cooled. The obtained gas seal layer had no cracks at all, was sufficiently dense and formed a completely reliable seal, and the complex-shaped molded product was not damaged at all. This gas-sealed molded body was prepared in the same way as in Section 1 < B
It is embedded in N powder and placed in a graphite crucible as shown in Figure 1 (
G) and charged into the HIP apparatus shown in Example 1 above.
The glass sealing layer was removed after HIP treatment under the same conditions as above.

The obtained Si3N sintered body has a theoretical density ratio of 99.4%.
The bending strength value is 52K at room temperature.
94n2.1200℃te50'42f arak.

Example 5 I got food.

Example 6 Hot press conditions were as follows: temperature +1250°C, Ill
Example 4 except that force 3-1 pressurization time: 30 minutes. ! :
Hot press and HJP pressure treatments were carried out under the same conditions to obtain a high density Si3N sintered body with similarly excellent properties.

When hot pressing was performed in the same manner as above, the glass powder was not densified, the sealing performance was poor, and the HIP treatment was defective.

Comparative example 6 A1. .

Seal/Honto Breath conditions: Temperature +1250'C, King Power:
The powder was not densified, had poor sealing properties, and could not be subjected to HIP treatment.

Comparative example 7 Honto breath conditions 'jr, temperature: la o o ℃,
Thousand kana・1OY4. Hot pressing was carried out in the same manner as in Example 4, except that the pressing time was 15 minutes. The value of Lη of the soft glass was small, leakage occurred from the gaps in the graphite mold, and the molding finally failed. Non-hydrostatic IF 1 (nikaka; j
It was damaged.

Comparative Example 8 Hot pressing and HI p 7JO treatment were carried out under the same conditions as in Example 4, except that the thickness of the BN powder applied to the surface of the compact was f 1 m. Due to deformation, the force of one piece of the molded body "ii Lb
As a result, 3i2N20 was generated at the contact area between the glass and Si3N4 due to an interaction reaction, which impaired the product value.

Example 7 Hot pressing was carried out under the same conditions as in Example 1 and Example 4, except that the thickness of the BN powder applied to the surface of the molded body was changed to 2. As a result, in the case of the method described in Example 1, since the shape of the Si3N4 molded body is simple,
Although a good gas seal layer was formed without any abnormalities,
In the case of Example 4, since the shape of the Si3N4 molded body was complicated, the molded body was damaged due to an untimely non-static stress component.

l Example 8 A complete and reliable gas sealing layer was formed when a photoflush was carried out under the same conditions as in Example 4, except that the thickness of the BN powder applied to the surface of the molded product was 5 mm.
By I P [E processing, Si
A 3N4 sintered body was obtained.

Example 9 The molded product of Example 1 was heated to 1800°C prior to forming a seal layer.
, Primary firing was performed for 20 minutes in an N25 uJE atmosphere, and true breath was applied in the same manner as in Comparative Example 2.
A gas sealing layer with good sealing properties was formed, and no breakage as seen in Comparative Example 2 was observed in the molded product, and sealing was extremely quick.

Example 10 The molded body of Example 1 and the molded body with a thickness of 150 mm
Temperature: 1400°C, 11 mocha: 20 min.
When hot pressing was carried out in the same manner as in Example 1 except that the pressure was 0.0 mm and the pressing time was 1 minute, some cracks were observed in the green compact, but after primary firing, no cracks were observed in the compact. I couldn't accept it in any way.

Example 11 Example 4. A molded body of 1150
The primary fired body was fired at 0°C for 25 minutes in an N25 gas atmosphere, and the hot press conditions were wet eroded: 1140°C.
When hot pressing was carried out in the same manner as in Example 4 except that 9m force + lOOη, addition V-i 1 hour = 15 minutes, a part of the raw molded body was partially divided, but - primary No cracks were observed in the fired product.

(Effects of the Invention) As shown in the above-mentioned Examples and Comparative Examples, the method of the present invention can produce various hard-to-sinter ceramic molded bodies represented by Si, Si, and N4. HIP
By skillfully utilizing high silica glass, which exhibits a high softening temperature, and applying specific hot press conditions during molding, a complete and reliable gas sealing layer is formed, resulting in high strength without contaminating the glass. Obtaining a homogeneous material, especially a structural material with excellent high-temperature properties: 1, which can also be made using the conventional glass capsule method and sintered glass method.

Completely eliminates the difficulty of sole formation seen in coating methods, etc., and forms a seal layer, which was previously considered to be extremely difficult, especially for large molded products, complex shaped molded products, etc., in an extremely simple, reliable, and inexpensive manner. Therefore, HI
A homogeneous ceramic molded body having a density substantially the same as the theoretical density, in which densification by P addition is carried out smoothly, reliably, with good refining efficiency and good yield. This greatly contributes to increasing the number of children's uses and expanding the range of applications.

Moreover, if the molded body is first fired for the first time before breath sealing, it will prevent damage to the molded body during breath sealing, and the quick sealing process will be more efficient. Increase value.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the steps of the method of the present invention, and FIG.
FIG. 3 is a diagram showing changes in viscosity of various glasses with respect to temperature, and FIG. 3 is a schematic diagram showing a preferred embodiment of the present invention, and FIG. 4 shows a program pattern for HIP processing of the method of the present invention. -jM, FIG. 5, and FIG. 6 are schematic explanatory diagrams showing the seal forming process by the conventionally known glass bath method. (1) Crucible, (2) Glass powder, (3) Ceramic molded body, (4) Airtight glass layer, (5) Crack i1. (6) Mold, (7) High silica glass powder. (8)・Heating element, (9)・Press ram, (1o
)・-L lid. (11)・Chamber, (+2)・Casing, (13)・Suction pipe, (+4)・BN powder,
(15) Gas seal layer. (16)・Support material, (17) Heat-resistant crucible,
(1sl internal heating element, (19) Pressure gas introduction hole, (20)...proof [F sealed container.

Claims (1)

[Claims] 1. A ceramic molded body is embedded in high silica glass powder filled in a heat-resistant mold, and the viscosity of the glass is about 10^.
hot pressing at a temperature of 1^0 poise or less to form a gas sealing layer around the ceramic molded body;
A method for hot isostatic pressing of ceramics, comprising subjecting the ceramic molded body covered with the gas seal layer to hot isostatic pressing. 2. High silica glass contains at least 96% by weight SiO
The hot isostatic pressure treatment method for ceramics according to claim 1, which comprises two components. 3. The method for hot isostatic pressing of ceramics according to claim 1 or 2, wherein the ceramic molded body is a green molded body obtained by molding ceramic powder by a known molding method. 4. Claim 1, wherein the ceramic molded body is a primary fired body obtained by performing preliminary primary firing on a molded body obtained by molding ceramic powder by a known molding method prior to forming a seal.
A method for hot isostatic pressing of ceramics according to item 1 or 2. 5. Primary firing at 1400℃ under N_2 atmosphere
4. The method of hot isostatic pressing of ceramics according to claim 3, wherein the hot isostatic pressing is carried out at a temperature of ~2000°C for 15 minutes or more. 6. The method for hot isostatic pressing of ceramics according to any one of claims 1 to 4, wherein the ceramic molded body is made of powder containing Si_3N_4 as a main component. 7. The viscosity of glass is approximately 100^9^. Claim 1, wherein hot pressing is performed at a temperature of ^5 poise or less.
The method for hot isostatic pressing of ceramics according to any one of items 1 to 5. 8. A method for hot isostatic pressing of ceramics according to claim 6 or 7, wherein hot pressing is performed at a temperature of about 1800° C. or lower. 9. The hot isostatic pressing method for ceramics according to any one of claims 1 to 8, wherein the hot pressing is performed in a reduced pressure atmosphere. 10. The method for hot isostatic pressing of ceramics according to claim 9, wherein the atmosphere in the reduced pressure state is a vacuum of about 10-1 mmHg or less. 11. The method for hot isostatic pressing of ceramics according to any one of claims 1 to 10, wherein hot pressing is performed at a pressing pressure of 1 to 100 kg/cm^2. 12. The method for hot isostatic pressing of ceramics according to claim 11, wherein the press pressure is 5 kg/cm^2 or more. 13. B between the ceramic molded body and the glass seal layer
A method for hot isostatic pressing of ceramics according to any one of claims 3 to 12, wherein N powder is interposed. 14. A patent claim in which BN powder is interposed between the ceramic molded body and the gas seal layer by applying BN powder to a thickness of about 2 mm or more on the surface of the ceramic molded body before embedding it in the glass powder. A hot isostatic pressing method for ceramics according to Scope 13. 15. The method for hot isostatic pressing of ceramics according to any one of claims 1 to 14, wherein the glass powder has an average particle size of about 1 mm or less. 16. The method for hot isostatic pressing of ceramics according to claim 15, wherein the average particle size is about 0.1 mm or less.