JP2516726B2 - Hot isostatic pressing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to pressure molding and sintering of metal powder, ceramic powder, etc. by simultaneously acting temperature and gas pressure, and densification of precision cast products, ceramic parts, etc. The present invention relates to a hot isostatic pressing method.

[0002]

2. Description of the Related Art A hot isostatic pressing apparatus has already been used for densification of cemented carbide tools, but its application has been improved in recent years as new materials such as ceramics and thermite are developed. The range is expanding. A conventional hot isostatic pressing device will be described with reference to FIGS. 5, 6 and 7.
10 is the main body of the hot isostatic pressurizing apparatus.
When the pressure medium gas is fed under pressure to the high-pressure cylindrical body 2, the upper lid 3 and the lower lid 4 fitted to the upper and lower ends thereof, and the pressure chamber 13 surrounded by these members, they act on the upper and lower lids 3 and 4. It is composed of a high-pressure container composed of a yoke frame 1 for supporting an axial force in the vertical direction, a heating furnace 9 detachably housed in the pressurizing chamber 13, and a pedestal 5.

Reference numeral 6 is a high pressure vessel moving cylinder, 7 is high pressure piping, 8 is power supply wiring to the heating furnace 9, 11 is a gas seal for the upper lid, 12 is a gas seal for the lower lid, and 14 is a processing chamber in the heating furnace 9 ( (See the chain double-dashed line), 15 is a heater (heating device) in the heating furnace 9, 16 is a heat insulating layer of the heating furnace 9, 17 is a casing of the heating furnace 9, and 18 is a heater power supply electrode detachably connected to the heater 15, Reference numeral 28 is a heater power feeding contactor fixed to the heater 15, 30 is a furnace body pedestal portion power feeding contactor provided on the hearth pedestal 21, and the contactor 30 is the contactor 2 described above.
It can be attached to or detached from 8.

Reference numeral 29 is a furnace frame, 19 is a hearth in the heating furnace 9, and 20 is a gas supply / exhaust pipe line connected to the high-pressure gas pipe 7. When the heating furnace 9 is now outside the high-pressure cylinder 2, the object to be processed is placed on the hearth 19 of the processing chamber 14 inside the heating furnace 9, and then the heating furnace 9 is shown by the chain double-dashed line in FIG. Is housed in the high-pressure cylinder 2 by a hoist or the like, and the upper end opening of the high-pressure cylinder 2 is hermetically closed by the upper lid 3,
Next, the high-pressure container including the same high-pressure cylinder 2 is sent into the yoke frame 1 by the high-pressure container moving cylinder 6, and the pressure medium gas is supplied from the pressure intensifier (not shown) to the high-pressure gas pipe 7 and the supply / exhaust pipe line 20. After that, the pressure is fed to the pressure chamber 13 and the processing chamber 14 in the high-pressure cylinder 2 to pressurize these chambers.

On the other hand, electric power is supplied from the power supply wiring 8 to the heater 15 through the heater power supply electrode 18 and the contactors 28 and 30, and the heater 15 generates heat to heat the processing chamber 14 surrounded by the heater 15. When the gas pressure, the temperature, and the temperature of the processing chamber 14 reach a predetermined processing condition, the state is maintained for a certain period of time, during which hot isostatic pressing of the object to be processed is performed. Then, when the hot isostatic pressing process is completed, power supply to the heater 15 via the power supply wiring 8, the heater power supply electrode 18, and the contactors 28 and 30 is stopped, the heating furnace 9 is cooled, and the pressurizing chamber 13 is pressed. And processing room 1
The pressure medium gas of No. 4 is discharged into the atmosphere through the gas supply / exhaust pipe line 20 and the high pressure gas pipe 7, and these chambers 13, 14 are discharged.
Is lowered, then the high-pressure container including the high-pressure cylinder 2 is sent out of the yoke frame 1 by the cylinder 6 for moving the high-pressure container, then the upper lid 3 is removed, and then the heating furnace 9 is placed in the processing chamber 14 together with the object to be processed. It is taken out of the high-pressure cylinder 2 by a hoist or the like.

Reference numeral 40 is a cooling jacket provided on the inner wall of the high-pressure cylinder 2, and by passing cooling water through the cooling jacket 40 during hot isostatic pressing, the high-pressure cylinder 2 is cooled.
Is designed to be cooled.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the conventional hot isostatic pressing apparatus shown in (1), since the object to be processed is mainly a metal material, the processing temperature is around 1250 ° C. (in the case of a cemented carbide (WC type) tool which is not a metal material, Around 1450 ° C.), and in the members constituting the heating furnace 9,
Molybdenum and super heat resistant alloys (Ni-based alloys) are used. These materials start to be oxidized and carbonized and deteriorated at around 500 ° C. However, since the metal material to be treated has the same characteristics as the heating furnace 9, an inert gas (Ar, He, etc.) is used as the pressure medium gas. Is used, and the atmosphere remaining in the pressurizing chamber 13 is discharged by a vacuum pump before the operation to maintain the degree of vacuum at about -10 ^-3 Torr, and then the operation is started. Product quality deterioration and heating furnace 9
Was prevented from deteriorating the constituent members constituting the.

Recently, there has been an increasing demand to improve the quality of non-oxide ceramic materials (silicon nitride, silicon carbide, etc.) by hot isostatic pressing. A hydrostatic pressure treatment device has been developed. In this ultra high temperature type hot isostatic pressurization device, molybdenum,
A heating furnace 9 in which a metal material such as a super heat-resistant alloy is replaced by a high-purity / high-density graphite material is used, but in this case, although it does not have the same oxidation resistance as the metal material, it is a non-oxide ceramic. Sufficient for processing the material.

N ₂ gas is used to treat silicon nitride ceramics, and Ar is used to treat silicon carbide ceramics.
Gas is used respectively. Also, very recently, oxide ceramics [beryllia (BeO), zirconia (ZrO ₂ ), alumina (Al ₂ O ₃ ), magnesia (MgO), mullite (SiO ₂ · Al ₂ O ₃ ), zirconia-alumina, etc. Composite ceramics, perovskite structure (ABO ₃ , eg A; Ba, Pb, Li,
B; oxides having Ti, Zr, Sr, La, Nb, Sn), ferrite (ZnFe ₂ O ₄ , SrO.6Fe _2).
O _3, Mn-Zn ferrite, Ni- ferrite, etc.), spinel _{(Al 2 O 3 · MgO)} , a semiconductor ceramic _{(ZnO, B-Al 2 O} 3, ZrO 2, Sn
O ₂ , ZnO / Bi ₂ O ₃ , VO ₂ , BaO, LaCr
O ₃ etc.)] is subjected to hot isostatic pressing to improve the quality.

In this case, however, if the conventional hot isostatic pressing apparatus is used, the product to be processed will be altered, discolored, cracked, etc., so that the product to be processed is embedded in the raw material powder for processing. Although it is necessary to adopt the hot isostatic pressing method described above, there are many problems. That is,
Various troubles (deterioration, deterioration) that occur when the oxide ceramics are processed by the conventional hot isostatic pressing apparatus
The cause of such discoloration and cracking is that the same treatment is performed in an atmosphere of a reducing gas such as CO, and transition metal oxides (for example, iron, nickel, cobalt, etc.) contained in a trace amount in the ceramic material are reduced. It is considered that a small amount of carbon mixed in the sintered body is evaporated at a high temperature, and as a result, a cavity is formed in the sintered body.

In the case experienced by the applicant, the zirconia ceramic containing _{2 to} 5 mol% Y ₂ O ₃ (Zr
O ₂ ) and a graphite furnace as a heating element are used at 1400 ° C. and 2000 kg / cm ² (A
When the article to be treated was treated under the condition of (r gas), the article to be treated which was white before the treatment turned from dark gray to black. Further, when the article to be treated was held at a temperature of 1000 ° C. or less and baked in the atmosphere for 4 to 10 hours, the original white color was completely returned to the central portion of the article to be treated. This change
It is considered that the carbon that was mixed in the processed product evaporated as carbon dioxide gas, and that the transition metal oxide contained in the processed product returned to the original stable oxide state that was in stoichiometric proportion. To be

[0012] If such a change occurs, mechanical strength such as bending strength and fracture toughness of the sintered body is significantly reduced.
It has become necessary to adopt a hot isostatic pressing method of the embedded powder method in which the product to be processed is embedded in the raw material powder, but with this method, the embedded powder (powder) is being processed in the heating furnace. It tends to scatter in the air and cause equipment trouble. Further, it is difficult to produce a sintered body having a complicated shape such as an impeller or a blade of an engine part, and there is a problem that the processing cost is increased. Applications of the oxide-based ceramics include electronic functional members (magnetic heads, insulators, semiconductors, etc.), structural members (sliding parts, machine element parts, etc.), medical devices (inspectors, scalpels, etc.), OA, office equipment. There is a wide range of applications, such as parts for sensors and other items (sensors, cash register products, artificial jewelry, etc.), but it is necessary to stabilize quality, enhance functionality, and increase strength by hot isostatic pressing. ,
It is necessary to solve the above problems.

The present invention is proposed in view of the above problems, and the object of the present invention is to solve various problems (alteration, alteration,
A hot isostatic pressing method capable of obtaining a sintered body having a complicated shape with high mechanical strength without causing troubles such as discoloration and cracks and equipment troubles) and without causing a rise in processing cost. There is a point to offer.

[0014]

In order to achieve the above object, in the hot isostatic pressing method of the present invention, an oxygen concentration of 100 pp is formed after forming a gas impermeable film on the surface of the article to be treated.
It is characterized in that ceramics of an oxide material is pressurized and heated in an atmosphere of an oxidizing gas of m to 50 Vol%.

[0015]

According to the hot isostatic pressing method of the present invention, after the gas impermeable film is formed on the surface of the article to be treated as described above, the oxide is formed in an atmosphere of an oxidizing gas having an oxygen concentration of 100 ppm to 50 Vol%. Pressurize and heat the ceramics of the system material. In other words, the ceramic of the oxide material is pressurized and heated by the oxidizing gas having the oxygen concentration suitable for preventing the reduction of the sintered body and raising the ignition point of the heating furnace constituent material. It is possible to improve the characteristics and extend the life of the heating furnace constituent materials, and various troubles (alteration, discoloration,
It is possible to obtain a sintered body having a high mechanical strength and a complicated shape without causing troubles such as cracking and equipment troubles and causing a rise in processing cost.

[0016]

EXAMPLE An example of the structure of a heating furnace of a hot isostatic pressing apparatus used for carrying out the hot isostatic pressing method of the present invention will be described below with reference to FIGS. Is a heating furnace of a hot isostatic pressing apparatus suitable for use in an atmosphere of an oxidizing gas. The heating furnace 9 includes a heater 15, an inner layer ceramic shell 23 incorporated so as to surround the heater 15. The inner layer metal shell 24, the outer layer metal shell 26, the inner layer ceramic fiber insulation material 25 filled between the shells 24, 26, the heating furnace casing 17, the heating furnace casing 17 and the outer layer metal shell 26 It is composed of an outer layer ceramic fiber heat insulating material 27 filled in the space, a hearth pedestal 21, power supply contactors 28 and 30 for supplying power to the heater 15, and a hearth 19.

Reference numeral 16 is a heat insulating layer composed of an inner ceramics shell 23 and an inner metal shell 24. The loading and unloading of the heating furnace 9 to and from the high-pressure container is performed by a hoist as shown in FIG. In addition, for loading and unloading the article to be processed into and from the processing chamber 14 formed in the heating furnace 9, the set screw 31 is removed, and the hearth pedestal 21 on which the hearth 19 is placed, the heater 15 and the heat insulating layer 16 are incorporated. It is performed separately from the casing 17.

Further, in the same heating furnace 9, the ceramics shell 23 of the innermost layer which is exposed to the highest temperature during the hot isostatic pressing treatment operation uses the ceramics excellent in heat resistance and oxidation resistance shown in Table 1. In addition, the innermost layer ceramic shell 23 is not only used as a convection prevention shell but also has a heat insulating effect. Therefore, the porosity is 30 to 80% and the thickness is 5 to 20 mm. Quality ceramics, and the same ceramics shell 2
In order to suppress the convection that is going to occur through 3
The inner layer metal shell 24 is fitted on the outer side of the inner layer ceramic shell 23, that is, the inner layer metal shell 24 is assembled so that the gap between both layers is 0 to D / 1000 mm with respect to the outer diameter D of the innermost layer shell. The heat insulating layer 16 is formed integrally.

[0019]

[Table 1] Further, as described above, the inner layer metal shell 24 is fitted into the inner layer ceramics 23 from the outside, and the inner layer ceramics shell 2 is
Even if 3 is damaged, the fragments are prevented from falling off and seriously damaging the heating furnace 9. The heating furnace 1 described above will be described more specifically. In order to satisfy the heat insulation characteristics in the heating furnace 9, the structure and shape of the heating furnace 9 must satisfy the following requirements.

The thickness of the heat insulating layer 16 is made as thin as possible,
While the mouth system of the high-pressure vessel is made small and the shell is formed as an inverted cup-shaped cylindrical system with the upper end closed, the convection generated inside the heating furnace 9 is made of a gas impermeable material as described above. Need to be prevented. That is, the thickness of the heat insulating layer 16 of the heating furnace 9 in the hot isostatic pressing apparatus is about 1/3 to 1/5 of the thickness of the heat insulating layer of a general heating furnace, but Transfer coefficient (kcal / m ² H
Since the value of r.degree. C.) is very high, cooling water is constantly supplied to the cooling jacket 40 provided on the inner surface of the high-pressure cylinder 2 to pressurize the pressurizing chamber 1
The surface of the heating furnace casing 17 is sufficiently cooled to a temperature close to the temperature of the cooling jacket 40 through the high-pressure gas in 3 (in the case of argon gas, the heat transfer coefficient value is usually constant at a high pressure of 2000 kg / cm ² ). It will be several hundred times higher than the pressure).

Therefore, a large temperature difference is generated in the heat insulating layer 16 from the inner side to the outer side, and the inner layer shell 2 close to the heater 15 is formed.
3 and 24 become high temperature, the outer layer shell 26 becomes relatively low temperature, and the inner layer shell 23,
A metal material can be used without requiring heat resistance as high as 24. On the other hand, as described above, the high-pressure gas has a high heat transfer coefficient value in the heating furnace 9 and behaves like water with low viscosity. As described above, in the structure in which the processing chamber is formed only by the cylindrical heat insulator and the heat insulator that closes the upper and lower parts,
The high-pressure gas passes through the clearance of the heat insulator, is heated in the processing chamber, is cooled by the cooling jacket, and vigorous convection occurs in the entire heating furnace, so that the temperature of the processing chamber does not rise at all.

In order to prevent such convection from occurring, in the heating furnace 9 of the hot isostatic pressing apparatus of the present invention, the shell is in the shape of an inverted cup with the upper end closed, and a gas impermeable multilayer structure. The above shape prevents the gas heated in the processing chamber from escaping upward. Also, due to the above-mentioned multilayer structure, that is, between the shell and the shell (for example, between the shell 26 and the shell 24 in FIG. 1 and the shell 2).
6) and the casing 17) are made as narrow as possible, and the portions are filled with the ceramic fiber heat insulating materials 25 and 27 so as to suppress convection generated in the same portions.

Next, the structure of the shell that satisfies the above conditions will be described more specifically. An inverted cup-shaped cylindrical shell with the upper end closed was made of dense alumina, and this was tested by incorporating it into a heating furnace as an inner layer ceramic cell without fitting the inner layer ceramic shell 24, and the thermal stress generated during operation was shown. In addition, due to the thermal shock received during the temperature rising and cooling processes, the shell was damaged at a certain temperature or higher depending on its shape, and there was a limit to its use as a shell.

Further, from this experience, a porous ceramic having a high thermal shock resistance and being hard to be totally damaged even if it is damaged by thermal stress was used for the inner layer ceramics without fitting the inner layer ceramic shell 24. However, since it is porous, it has a low property of suppressing high-pressure gas convection, and not only the temperature of the metal parts such as the outer metal shell and heating furnace casing rises excessively, but also the temperature of the processing chamber does not rise. However, there was a limit to the usable range.

Therefore, it is necessary to add a gas impermeable function to the porous ceramics. In the embodiment, paying attention to the above point, as described above, the cylindrical shell (the inner layer ceramic shell 23) having the closed upper end is made of porous ceramics, and the inner layer metal shell 24 of the same shape is fitted on the outer side thereof. That is, the gap between the two layers is the outer diameter D of the innermost layer shell.
Incorporating them so as to be 0 to D / 1000 mm, they are integrated with each other and have gas impermeability, thereby sufficiently suppressing convection of high-pressure gas and maintaining a high processing temperature. The porous ceramics are completely prevented from being damaged at the same processing temperature.

The inner metal shell 24 may be replaced with a dense ceramic shell made of alumina, zirconia, quartz glass or the like. According to the hot isostatic pressing method of the present invention, after the gas impermeable film is formed on the article to be processed as described above, pressurization and heating are performed in an atmosphere of an oxidizing gas having an oxygen concentration of 100 ppm to 50 Vol%. I have to. The reason for pressurizing and heating under the above conditions is that if the concentration is less than 100 ppm, the oxygen concentration is insufficient and the sintered body is reduced, so that a desired sintered body cannot be obtained, and it exceeds 50 Vol%. Then, the ignition point of the heating furnace component is significantly lowered, and the life of the heating furnace component is shortened. As described above, pressurization and heating are performed in an atmosphere of oxidizing gas having an oxygen concentration of 100 ppm to 50 Vol%. Then, it is possible to prevent the occurrence of the above situation.

The lower the oxygen concentration, the higher the ignition point and the longer the life of the heating furnace constituent members, but preferably 30% or less, more preferably 20% or less. (Specific example 1) Heating furnace 9 (effective size of processing chamber: diameter 100 m
m, length 300 mm), temperature: 1600 ° C., pressure: 2000 kg / cm ² oxidizing gas (1 for Ar gas)
Pressurization and heating were performed in an atmosphere of (oxidizing gas mixed with oxygen of 00 ppm to 10%). At that time, in the inner layer ceramic shell 23 of the heating furnace 9, a thickness of 15 mm,
Porous alumina having a porosity of 60% was used, and the inner metal shell 24 was made of stainless steel having a thickness of 1.0 mm. The temperature of the inner layer metal shell 24 during operation was 850 ° C., and it could be used without problems up to an oxygen concentration of 50%, but local damage was observed at an oxygen concentration exceeding 50%. (Specific example 1 ') Heating furnace 9 (effective dimension to be treated: diameter 100 m
m, length 300 mm) at a temperature of 1600 ° C. and a pressure of 2000 kg / cm ² under an atmosphere of an oxidizing gas (argon gas mixed with 100 ppm to 50% of oxygen in argon gas). Pressure and heating were performed. At that time, among the components constituting the heating furnace 9, the inner layer ceramics 23 was a porous composite material having a thickness of 8 mm and a porosity of 60% (alumina to which 30 to 90 Vol% of quartz glass was added and sintered). Then, a low thermal stress type material having a low coefficient of thermal expansion of quartz glass was used, and the inner layer (metal) shell 24 was made of quartz glass having a thickness of 4 mm. During operation, the temperature of the inner layer (metal) was 1100 ° C. at the maximum, and the oxygen concentration could be used up to 50% without any problem.

The inner layer ceramic shell 23 used in this example (Specific Example 1 ') is porous, has high impact resistance, and has a high fracture stress limit due to thermal stress, but on the other hand, it occurs. In order to keep the thermal stress low, it is effective to reduce the wall thickness. This wall thickness is the thickness of the inner layer (metal) shell 24 fitted to the outer side of the inner layer ceramic shell 23.
Determined by the allowable temperature of.

In the above (Specific Example 1), a stainless steel shell is used for the inner layer (metal) shell 24. However, in order to suppress the oxidation of the shell, it is necessary to keep the temperature between both layers at 850 ° C. or lower. Yes, the thickness of the inner layer ceramics is 15m
m. On the other hand, the silica glass used in the present example (Specific example 1 ') is characterized by low thermal expansion and therefore low thermal stress, but the disadvantage is that devitrification occurs at temperatures above 1300 ° C. The so-called alteration occurs and the coefficient of thermal expansion increases, resulting in high thermal stress and failure of the shell. Therefore, it is necessary to use it at a temperature of 1100 ° C. or lower, but since it can be used at a temperature significantly higher than that of stainless steel, the thickness of the inner layer ceramics 23 can be reduced to about half, that is, 8 mm.

Therefore, the thermal stress level generated in the inner layer ceramics 23 is halved, and the life thereof is dramatically improved as compared with (Specific Example 1). Quartz glass is 1100
At a temperature of not higher than 0 ° C, even if the oxygen concentration was high (up to 50%), almost no deterioration occurred, so that stable treatment became possible. (Specific Example 2) FIGS. 2 and 3 show the heating furnace 9 (effective size of the processing chamber:
Of the diameter of 300 mm and the length of 1000 mm), the heat insulating layer composed of the inner layer ceramic shells 33 and 34 and the inner layer metal shell 32 is shown. In this example (Specific example 2), since the effective size of the processing chamber is large and the inner layer ceramic shell cannot be made in one body, it has a divided structure. When splitting,
As shown in FIG. 3, the side close to the center needs to have a high-height fitting structure.

In the case of the fitting structure shown in FIG. 4, since the low temperature gas layer 37 is located above the high temperature gas layer 38 in the gas layer flowing through the clearance between the fitting portions, the clearance passes through this clearance. As a result, convection easily occurs and the inner-layer metal shell 32 is easily damaged. The reason shown in FIGS. 2 and 3 is to prevent this damage. Using the hot isostatic pressing method of the present invention, the hot isostatic pressing was carried out in an oxidizing gas atmosphere having an oxygen concentration of 100 ppm to 50 Vol%.
The following results were obtained. As described above, the heating furnace 9 having an effective size of 100 mm in diameter and 300 mm in length is used. In the heating furnace 9, the inner layer ceramic shell 23 is made of porous alumina (porosity 60%) having a thickness of 15 mm. The inner metal shell 24 is made of stainless steel (1.0 m
m), high-purity alumina fiber is used for the heat insulating materials 25 and 27, and porous alumina of the same material as the inner layer ceramic shell 24 is used for the carrier of the heater 15.
A platinum-rhodium alloy wire rod was used for the heater element. Oxygen in the pressure medium gas is 100 ppm, 1%, 10
% Argon gas is used, and the final holding temperature (1400
℃) for about 2 hours, and then increase the pressure to 2000
After holding for 1 hour in the state of kg / cm ² , after the completion of the holding, the operation was completed by returning to normal temperature and atmospheric pressure through a process opposite to the temperature raising.

The article to be treated was a zirconia-based pre-sintered body having a gas impermeable film and a theoretical density of 95%, but it was densified (improved to a theoretical density of 99.5%) by the above treatment. In addition, the color of the product to be processed was originally 1% when the gas containing 100 ppm of oxygen was colored gray,
At 0%, there was no discoloration before or after the treatment. Further, the above treatment was carried out to obtain the following sintered body. That is, ceramics (zirconia, alumina, magnesia, yttria, etc.) created by a conventional hot isostatic press
Is a gray or black sintered body that absorbs almost all the light, so that it was not possible to obtain ceramics having colors such as yellow, green, and red, but under the atmosphere of an oxidizing gas as in the present invention. When the hot isostatic pressing process is performed, since the produced sintered body has almost the theoretical density, it becomes possible to transmit and reflect light. For example, a pre-sintered body of raw material powder in which a trace amount of a transition metal oxide such as iron, cobalt, nickel, or a rare earth oxide such as cerium lanthanum is added to ceramics is subjected to hot isostatic pressing under an oxidizing gas atmosphere. Then, it becomes possible to create colorful ceramics.

In this case, the ceramics are polycrystals, which are different from the single-crystal artificial gems, and a sintered body that can be used as an artificial ornament, a gem, etc. was obtained. Further, a sintered body was obtained which can be used for blades such as seals, scissors, cutters and knives, tableware, daily necessities, watch parts and parts for watches, machine tool parts such as drivers, parts for internal combustion engines such as automobiles, etc. The quality and various physical properties of such a sintered body are improved for the following reasons. (1) Among the conventionally known ceramics, the high temperature characteristics of zirconia-yttria or zirconia-magnesia ceramics having particularly high strength and toughness are improved. That is, the above zirconia-ceramic
Even if heated at the above high temperature for a long time, the mechanical strength does not decrease in the atmosphere of the oxidizing gas. This excellent characteristic is that ceramics other than zirconia, such as alumina, alumina-
There are zirconia, etc., and they can be applied. (2) Generally, the sintered body produced by the hot isostatic pressing apparatus has very good mechanical properties, abrasion resistance, and slidability at room temperature, and has a conventional non-oxidizing property. A sintered body prepared in a gas atmosphere is no exception, but when it is used at a high temperature of 500 ° C. or higher, the mechanical strength is greatly reduced and the excellent characteristics of the sintered body are lost. The reason for this is that the carbon contained in the product to be processed evaporates as carbon dioxide gas, and the transition metal oxide contained in the product to be processed is in the original stable oxide state which is stoichiometrically proportional. This is to return. on the other hand,
As described above, when pressurized and heated in an atmosphere of an oxidizing gas having an oxidizing concentration of 100 ppm to 50 Vol%, the oxidizing concentration is sufficient, and the sintered body obtained by the hot isostatic pressing method of the present invention. The above phenomenon does not occur.

The object to be treated in the present invention is not limited to the pre-sintered body on which the gas impermeable film is formed, but a powder compact or an oxide type gas impermeable film is formed. The present invention is also applicable to a powder compact having a gas-impermeable film formed by coating the metal constituting the object, a so-called encapsulated compact, and the like.

[0035]

As described above, the hot isostatic pressing method of the present invention, after forming the gas impermeable film on the surface of the article to be treated,
Ceramics of an oxide-based material are pressed and heated in an atmosphere of an oxidizing gas having an oxygen concentration of 100 ppm to 50 Vol%. That is, since the ceramics of the oxide-based material are pressurized and heated with an oxidizing gas having an oxygen concentration suitable for preventing the reduction of the sintered body and raising the ignition point of the heating furnace constituent material,
It is possible to improve the characteristics of the sintered body and extend the life of the heating furnace constituent materials, and
It is possible to obtain a sintered body having a complicated shape with high mechanical strength without causing troubles such as discoloration and cracks and troubles in the apparatus and without increasing the processing cost.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view showing a configuration example of a hot isostatic pressing apparatus used for carrying out the hot isostatic pressing method of the present invention.

FIG. 2 is a partially longitudinal side view showing another configuration example of the hot isostatic pressing apparatus.

FIG. 3 is a vertical cross-sectional side view showing an enlarged part of the hot isostatic pressing device.

FIG. 4 is a vertical sectional side view showing an example of a flow generated in a clearance between heat insulating layers.

FIG. 5 is a vertical sectional side view showing a conventional hot isostatic pressing apparatus.

FIG. 6 is a side view showing the entire hot isostatic pressurizing apparatus.

FIG. 7 is a front view showing the entire hot isostatic pressurizing apparatus.

[Explanation of symbols]

 9 heating furnace 16 inner heat insulating layer 23 porous ceramic inner layer shell 24 dense material inner layer shell 25, 27 ceramic fiber heat insulating material 26 dense material inner layer shell

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takaki Masaki 1-1-1, Sonoyama, Otsu, Shiga Toray Industries, Ltd. Shiga Plant (56) References JP-A-50-62106 (JP, A) JP-A-SHO 57-126903 (JP, A)

Claims (1)

(57) [Claims] 1. A gas impermeable film is formed on the surface of an article to be treated, and then ceramics of an oxide material is pressurized in an atmosphere of an oxidizing gas having an oxygen concentration of 100 ppm to 50 Vol%,
A hot isostatic pressing method characterized by heating.