JPS6011276A - Manufacture of ceramic sintered body - 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 Field of Application) The present invention relates to a method for manufacturing a ceramic sintered body, and relates to a method for manufacturing a ceramic sintered body, for example, for manufacturing a ceramic sintered body that has a complex shape and some The present invention relates to a method for manufacturing a ceramic sintered body suitable for manufacturing a ceramic sintered body having a thick portion.

(Prior Art) Conventionally, as a method for manufacturing a ceramic sintered body, there is a method that goes through the steps shown in FIG. 1, for example. In this method, ceramic powder is mixed with an organic binder and then pelletized into granules, then injection molded in the same manner as resin injection molding to produce a molded body, and then the organic binder is heated from the molded body in the degreasing process. A ceramic sintered body is obtained by removing the ceramic material, followed by a sintering process, and then performing appropriate finishing processing. This method of manufacturing ceramic sintered bodies using injection molding is particularly promising as a method suitable for manufacturing parts that have complex shapes and are mass-produced, such as automobile parts. There are various problems in the molding and degreasing processes, which limit the shape and thickness of ceramic sintered bodies that can be manufactured.

In other words, when attempting to mold parts with complex shapes and thick parts by injection molding, shrinkage due to solidification shrinkage, poor welding due to temperature drop and insufficient pressure transmission, etc. occur, and the molding process is not defect-free and healthy. The problem is that it is difficult to obtain a molded product, and even if a defect-free molded product can be obtained by considering the molding method, molding conditions, organic binder, etc. in the molding process, it is difficult to obtain a molded product without removing the organic binder in the next degreasing process. Since chemical and physical changes (for example, volatilization/decomposition, melting, crosslinking reactions, etc.) tend to occur, it is difficult to obtain a healthy degreased product.

For this reason, we investigated ceramic compositions for injection molding that can be degreased even for thick-walled parts (for example,
5616, Japanese Patent Publication No. 55-23097, etc.) and improvements in the degreasing process (e.g., Japanese Patent Publication No. 57-17468, etc.)
However, there remains the problem that there is a limit to the wall thickness that can be degreased.

Therefore, for example, in the case of a turbine rotor 3 consisting of a blade section 1 and a shaft section 2 as shown in FIG. 2, the turbine rotor 3 is divided into the blade section 1 and shaft section 2 as shown in FIG. According to the process, the ceramic powder and the organic binder are mixed and then granulated by pelletizing, and then the wing part 1 and the shaft part 2 are separately injection molded, and the organic binder in the obtained molded body is degreased and removed. It has also been considered to combine and fit the image moldings, cover them with rubber, then bond them together by hydrostatic pressure, and then sinter and finish as appropriate.

According to this method, since the same injection molding material is used for the wing part 1 and the shaft part 2, the density after degreasing and the density change during isostatic pressurization are shown in Figure 4 (Fig. 4). (For example, the case where the amount of organic binder is 45% by volume is shown.) As a result, cracks due to differences in shrinkage ratio do not occur, and even if the turbine rotor has a somewhat thick wall, there will be no defects. A healthy sintered body can be obtained.

However, when injection molding is used, good molding cannot be achieved unless 40 to 50% by volume of organic binder is added to the ceramic powder. In addition to the problem that the possible wall thickness limit is small and it is difficult to degrease the shaft part in particular, there is also the problem that defects and residual stress may occur due to solidification shrinkage and thermal gradients during injection molding. was.

Therefore, it is conceivable to form the particularly thick part of the sintered body, that is, the shaft part 2 in the example of FIG. The wing part 1 was molded by injection molding (the amount of organic binder in the molded product was 45% by volume), and the shaft part 2 was molded by isostatic pressure molding (the amount of organic binder in the molded product was 45% by volume). is 10% by volume, molding pressure is 1,
5 ton 7cm2), as shown in Figure 5,
In particular, there is a problem that cracks may occur due to the difference in shrinkage rate because the density after degreasing and in addition, the density change during isostatic pressure bonding after fitting the two is different. was. Therefore, in the conventional case, a ceramic molded Φ degreased body formed by injection molding and a ceramic molded / degreased body molded by ordinary isostatic pressure molding are combined and bonded, and then fired to create a defect-free ceramic body. Attempts to obtain sintered bodies were difficult.

(Purpose of the Invention) This invention was made by focusing on these conventional problems. It is possible to bond and integrate ceramic molded and degreased bodies molded using the isostatic pressure molding method, which uses at least the amount of binder that can be molded and has a low risk of degreasing defects, without any problems using hydrostatic pressure. It is an object of the present invention to provide a method capable of producing a ceramic sintered body having excellent strength and dimensional accuracy after firing, and having a complex and thick portion not seen in the past.

(Structure of the Invention) A method for producing a ceramic sintered body according to the present invention is to combine a molded/degreased ceramic body molded by injection molding and a molded/degreased ceramic body molded by isostatic pressure molding by laminating, fitting, etc. When combining and bonding and sintering to obtain a ceramic sintered body, the ceramic molded and sintered body formed by injection molding and the ceramic molded and sintered body formed by isostatic pressing are each For example, the amount and type of organic binder, molding pressure, molding temperature, etc. may be adjusted so that the densities of the ceramic molded/sintered bodies after degreasing are similar to each other, or the density can be increased by isostatic pressing after degreasing the molded bodies. is adjusted, and then both molded and degreased ceramic bodies are combined by lamination, fitting, etc., and then both molded and degreased ceramic bodies are bonded by isostatic pressure, and then sintered. It is something to do.

FIG. 6 is a process diagram for manufacturing a ceramic sintered body showing one embodiment of the present invention, and will be described below according to the process diagram.

Note that although a turbine rotor that combines a blade portion and a shaft portion will be described as an example, it is natural that the present invention is not limited to such parts.

First, when molding the wing parts, in order to give the ceramic powder enough fluidity to enable injection molding, organic binder powder (e.g. 40 to 50% by volume) is mixed, granulated by pelletizing, and then injection molded. A molded body is obtained by molding. Next, this molded body is gradually heated in an appropriate atmosphere at a temperature increase rate that does not cause cracks or blisters in the molded body, and the organic binder is removed by volatile decomposition to obtain a degreased body.

On the other hand, when molding moving parts, an organic binder (e.g. 20 to 40% by volume) is mixed to give the ceramic powder enough bonding properties to enable pressure molding, and the powder is pulverized and sized (e.g. 500 gm or less). ) and then fill it into a rubber mold.
A molded body is obtained by hydrostatic pressing. At this time, the density after degreasing, more preferably, the density change during isostatic pressure bonding is close to the density of the degreased body of the wing portion and the density change during hydrostatic pressure bonding (for example, within 5%). ), adjust the type and amount of organic binder, hydrostatic pressure, and temperature during pressurization. Next, the obtained molded body is gradually heated in an appropriate atmosphere at a temperature increase rate that does not cause cracks or blisters in the molded body, and the organic binder is removed by volatile decomposition to obtain a degreased body.

Next, after the molded and degreased body of the wing part and the molded and degreased body of the shaft part are fitted and combined (see Figure 2), the entire surface is covered with a film having elasticity and airtightness such as rubber. , compressed and bonded by hydrostatic pressure. At this time, prior to fitting the wing part and the shaft part, the fitting part of the molded body or degreased body of the shaft part (the molded body is shown as an example in FIG. 6) is processed, and when the combination fitting is performed, the fitting part is processed. Increasing the adhesion has the effect of suppressing the occurrence of cracks during hydrostatic pressure bonding, but if the precision of the fitting part can be ensured by controlling the precision of the rubber mold and the filling rate, such a fit will be prevented. It is also possible to omit processing of the joint.

Next, a ceramic sintered body is created by firing and sintering the above-described hydrostatically pressurized bonded body in an appropriate atmosphere and temperature, and a ceramic turbine rotor is obtained by appropriately finishing the combined body.

FIG. 7 is a process diagram for manufacturing a ceramic sintered body showing another embodiment of the present invention, and the following description will be made according to this process diagram.

First, an appropriate amount of a sintering aid and an organic solvent are added to ceramic powder, followed by sufficient wet mixing and pulverization, followed by drying and loosening to obtain a homogeneous mixed powder.

Next, when molding the wing portion, an organic binder is mixed and kneaded with the mixed powder, and the mixture is injection molded to obtain a molded body. Next, this molded body is heated to perform degreasing to remove the organic binder, and then the density of the degreased body is adjusted by hydrostatic pressurization to obtain a molded and degreased body of the wing portion.

On the other hand, when forming the shaft part, an organic binder and a lubricant are added to the mixed powder as necessary, and the slurry is granulated using a spray dryer or the like to form powder, and then isostatic pressure molding is performed. to obtain a molded body. Next, this molded body is processed and degreased by heating to remove the organic binder, and then the density of the degreased body is adjusted again by isostatic pressure to obtain a shaped skewer degreased body of the shaft portion.

In the density adjustment using the above-mentioned hydrostatic pressurization, the density of the wing molded and degreased body is ±5% of the density of the shaft molded and degreased body.
The approximation should be within the range. Next, the wing and shaft molded and degreased bodies are fitted together, covered with an airtight membrane such as rubber, and then joined and integrated using hydrostatic pressure to increase the density of at least the remolded and degreased body. A ceramic sintered body is manufactured by firing and sintering in an appropriate atmosphere and temperature, and a ceramic turbine rotor is obtained by applying appropriate finishing processing.

In addition, after adjusting the density of the molded and degreased body of the wing part and the shaft part by applying hydrostatic pressure, the fitting hole of the wing part and the fitting part of the shaft part are processed by matching the actual parts. It is possible to further improve integration by fitting the wing portion and the shaft portion.

(Example 1) 96.0 parts by weight of β-5iC powder with an average particle size of 0.3 pLm, 0.1 part by weight of metal B powder with an average particle size of 0.2 pLm, and 4.0 parts by weight of liquid phenolic resin (resol). Part (Si
(sufficient to provide about 2.0% by weight carbon) in ethanol for about 24 hours by ball milling. Next, this mixture was dried in a spray dryer, and 100 parts by weight of the obtained dry powder, 8 parts by weight of plasticized polystyrene resin, 5 parts by weight of low-molecular polyethylene resin, and 3.6 parts by weight of ester wax were added. , 5 parts by weight of dibutyl phthalate, and 1.5 parts by weight of fatty acid ester were kneaded in a stirring-type heating kneader, and then heated at 150°C in a Banbury-type kneader.
The mixture was kneaded for about 1 hour.

Subsequently, the obtained kneaded body was cooled and crushed into about 3
The pellets were pelletized to a size of about mm and used as a feedstock for injection molding. The amount of organic binder in the crosstalk body is 48% by volume.
It is.

Next, when injection molding the wing part, a plunger type molding device was used, the heating cylinder temperature was 180°C, the mold temperature was 45°C,
Injection pressure 1 ton/cm2. Pressurization.

The molded wing part 11 having the shape shown in FIG. 8 was obtained by injection molding for 2 minutes. The wing molded body 11 is designed so that the outer diameter of the wing after sintering is 120 mm, and as shown in the figure, the outer diameter d of the wing is 143 mm and the small diameter d2 is 143 mm.
= 24 mm, and has a fitting hole 12 with a large diameter d3 = 57 mm,
In addition, the maximum wall thickness of the hub portion is set to t1 = 14 mm to make it thinner so that it can be easily degreased after molding.

Next, the obtained wing molded body 11 was heated to 450° C. at a temperature increase rate of 2.5° C./hr in a nitrogen atmosphere.

Subsequently, the heating rate was increased to 7.5°C/hr to 900°C.
It was heated to 900°C, held at 900°C for 2 hours to perform degreasing, and cooled to obtain a molded and degreased wing part. Here, 20 wing molded bodies were manufactured and degreased under the above conditions, but no defects were observed in any of them after degreasing.

On the other hand, when producing the shaft molded body, powder from the same batch as the dry powder used for molding the wing parts was used, and 100 parts by weight of this dry powder, 3.7 parts by weight of low molecular weight polyethylene, and oxidized Add 3 parts by weight of microcrystalline wax, 3 parts by weight of oxidized paraffin wax, 2.7 parts by weight of ester wax, 3.7 parts by weight of diethyl phthalate, and 1.1 parts by weight of fatty acid ester, and use the same method as for the wing part. The organic powder content of the kneaded body obtained here was 35% by volume. Next, this kneaded body was pulverized using a Henschel type granulator while cooling with dry ice.
The material was passed through a sieve of 0.00 gm and used as a raw material for isostatic pressing.

Next, after filling the above raw material into a rubber mold while applying vibration, the filled body was placed in an oven maintained at 60°C for 1 hour.
Hold for a while, then immediately cover with a thin rubber bag and use 2 to
The molded shaft portion 13 having the shape shown in FIG. 9 was obtained by isostatic pressing at a pressure of n70 m2. During this molding,
By adjusting the dimensions of the rubber mold and the filling rate of the crosstalk body, the diameter d4 = 24 + nm, d5 = 57mm, d6
= +0.2 to +1.0mm of target dimension of 30+nm
within the range. Next, the obtained molded body is subjected to lathe processing using a carbide cutting tool, and
After finishing to the dimensions shown in , it was heated in a nitrogen atmosphere to 450° C. at a temperature increase rate of 5° C./hr. Subsequently, the temperature increase rate was increased to 15°C/hr, and the temperature was increased to 900°C.
After degreasing by holding for 2 hours, a molded and degreased shaft body was obtained. Here, 20 shaft molded bodies were manufactured and degreased under the above conditions, but no defects were observed in any of them after degreasing.

Next, we investigated the density after degreasing and the density change during hydrostatic pressurization of the molded and degreased body of the wing part and the molded and defatted shaft part obtained by the above process, and found that ± It was found that they were very close to each other within 5%.

Subsequently, the shaft molded body 11 is inserted into the fitting hole 12 of the wing molded body 11.
After inserting and rubbing them together, they were covered with a thin rubber bag, and then hydrostatic pressure of 2 tons/0 m2 was applied to integrate the two. This pressure pressurizes the image molded object by 1
0 set, no defects such as cracks were observed in the molded product after integration.

Next, the ten integrally molded bodies obtained above were placed in a graphite resistance heating type vacuum furnace.

Heating to 1500°C at a temperature increase rate of 100'O/hr,
1500'C! After being held for 4 hours, the temperature was raised to 2100°C at a heating rate of 300°C/hr, held at 2100°C for about 2 hours, and then cooled in a furnace to obtain a sintered body. No defects such as cracks were observed in the obtained turbine rotor sintered body.

(Comparative Example 1) Using the same raw materials as those used for injection molding of the wing portion in Example 1, injection molding was performed under the same conditions to produce a total of 10 shaft molded bodies 13 shown in FIG. 9. Next, the obtained shaft molded body 13 was heated in a nitrogen atmosphere to 450°C at a temperature increase rate of 2.5°C/hr to perform degreasing. Next, when the degreased bodies were examined after cooling, defects such as cracks were observed in all of them, and it was found that there was a limit to the wall thickness that could be degreased.

(Comparative Example 2) A kneaded body in which 48% by volume of an organic binder having the same composition as the raw material used for molding the shaft portion in Example 1 was added to the dry powder was prepared in the same manner as in Example 1, and a comparative example Injection molding and degreasing of the shaft portion were performed under the same conditions as in Example 1. Next, when the obtained degreased bodies were examined, defects such as cracks were found in all of them, and it was not possible to obtain a sound degreased body.

(Comparative Example 3) An organic binder having the same composition as the raw material used for molding the shaft portion in Example 1 was added to the dry powder in an amount of 19% by volume, and the kneaded body was granulated using a Henschel type granulator. Similarly, it was passed through a 500 JLm sieve to obtain a raw material for isostatic pressing. Next, using this raw material, a shaft molded body shown in FIG. 9 was molded under the same conditions as in Example 1, followed by processing and degreasing. Degreased body 15 obtained here
Since no defects such as cracks were observed in the pieces, they were fitted in combination with 10 molded and degreased wing parts molded in the same manner as in Example 1, and hydrostatic pressure was applied in the same manner as in Example 1. When pressure bonding was performed, cracks had occurred in all 10 pieces.

Then, we investigated the density after degreasing of the remaining five shaft molded and degreased bodies and the density change during hydrostatic pressurization, and the results are shown in Figure 11. It was found that the density and density change during hydrostatic pressurization were different.

(Comparative Example 4) Dry powder used in Example 1 (granule size 80 pLm
The following) was filled into the rubber mold used in Example 1 as it was, and when 10 shaft molded bodies were molded under a hydrostatic pressure of 2 Oton/0 m2, cracks had occurred in 8 of the 10 molded bodies. Next, the two pieces that did not develop cracks were processed and combined with two wing molded and degreased bodies produced in the same manner as in Example 1, fitted together, and bonded using hydrostatic pressure. ,2
Cracks occurred in both. In addition, cracks had occurred8.
When we investigated the density change of the molded and degreased shaft parts during hydrostatic pressurization, we obtained the results shown in Figure 12, which showed that the densities of the molded and defatted shaft parts and the molded and degreased wing parts were significantly different. there were.

(Comparative Example 5) In Comparative Example 4, the molding pressure of the shaft molded body was reduced to 0.
, when molded at a pressure of 5 tons/am2,
Cracks occurred in 7 out of 10 pieces. Next, when an attempt was made to process the three pieces in which no cracks had occurred to the dimensions of the shaft shown in FIG. 9, the molded bodies were damaged by the pressure applied during chuck. In addition, when we investigated the density change of the molded and degreased body of the shaft part during hydrostatic pressurization, we found that it matched the density change of the molded and degreased body of the wing part within ±5%, as shown in Figure 13. was. As described above, the density change of the degreased body during isostatic pressing can be changed by the molding pressure of the molded body, but in this case, the molding pressure of the shaft molded body was too low, which was not preferable.

(Example 2) This example is an example of manufacturing an axial flow type turbine rotor.

That is, 90 parts by weight of Si3N4 powder with an average particle size of 0.6 μm and 10 parts by weight of Y2O3 powder with an average particle size of 0.4 μm were mixed in ethanol for 100 hours using an alumina pot and pole. This mixture was dried in a vacuum stirring dryer.

Next, 100 parts by weight of the obtained dry powder, 8 parts by weight of polypropylene resin, 5 parts by weight of ethylene vinyl acetate, 1.8 parts by weight of oxidized microcrystalline wax, and 1.5 parts by weight of stearic acid were mixed in a stirring mold. After kneading with a heating kneader, the mixture was kneaded with a Banbury mixer at 130° C. for about 1 hour. Next, the obtained kneaded body was cooled and pelletized into pellets having a size of about 3 mm using a pulverizer to be used as a raw material for injection molding. At this time, the amount of organic binder in the kneaded body was 46% by volume.

Next, for injection molding, a screw-type molding device was used, the heating cylinder temperature was 160°C, the mold temperature was 35°C, the injection pressure was 1 ton 7cm2. No. 14 under the condition of pressurization time of 2 minutes.
A blade portion 21 of an axial turbine rotor 20 having the shape shown in the figure was molded. This wing portion 21 has a large outer diameter of 155 mm after sintering.
It is designed so that the diameter d7 = 154mm
, dB = 122 mm, and the maximum wall thickness of the hub portion is 12 = approximately 13 mm, which is designed to be thin to facilitate degreasing after molding. Next, the obtained molded body was heated to 450°C in the air at a heating rate of 2.5°C/hr, held at 450°C for 2 hours to degrease, and then cooled to mold and mold the wing section. A defatted body was obtained. A total of 20 molded bodies were made and each was degreased, but no defects were observed in any of them.

On the other hand, when forming the shaft part, 100 parts by weight of dry powder from the same batch as the wing part, 2 parts by weight of paraffin wax, 1.7 parts by weight of oxidized paraffin wax, and 1.7 parts by weight of oxidized microcrystalline wax were used. , 1.5 parts by weight of ester wax, 2 parts by weight of dibutyl phthalate, and 0.6 parts by weight of stearic acid were added, kneaded using a Henschel type granulator, and then crushed and granulated. At this time,
The amount of organic binder in the kneaded body was 20% by volume. Then, the obtained mixed wire body was passed through a 500 gm sieve to be used as a raw material for isostatic pressing.

Next, the kneaded body of 5'00 gm or less was filled into a rubber mold while being vibrated, and the filled body was kept in an oven kept at 45°C for 2 hours, and then immediately covered with a thin rubber bag. , 14th with hydrostatic pressurization of 5 ton/Cm2
A disc φ shaft molded body 23 having the shape shown in the figure was molded.

At this time, by adjusting the dimensions of the rubber mold and the filling rate of the kneaded body, the dimensions of the disk/shaft molded body 23 can be adjusted to the first
+0, 2~l of the dimensions shown in Figure 4 (d9=33mm)
, within 0mm. Subsequently, the obtained molded body was finished to the dimensions shown in Fig. 14 using a carbide tool, and then heated at 2.5°O/hr up to 450°C in an air atmosphere.
The sample was heated at a heating rate of 450° C. for 5 hours for degreasing, and then cooled to obtain a degreased body. At this time, a total of 20 molded bodies were prepared and degreased, but no defects were observed in any of them.

Next, we investigated the density of the molded degreased body of the wing portion 21 and the molded degreased body of the shaft portion 23 after degreasing and the change in density when hydrostatic pressure was applied, and as shown in FIG. 15, ±5% They were almost in agreement within the same range.

The molded and degreased body of the wing portion 21 and the molded and degreased body of the shaft portion 23 obtained in this way were rubbed together at the fitting portions and fitted together, and then covered with a thin rubber bag and packed at 2 ton/cm.
Pressure bonding was performed using a hydrostatic pressure of 2. At this time, 1 in total
When hydrostatic pressure bonding was performed for the 0 set, no defects such as cracks were observed in any of them.

Next, a total of 10 shafted turbine rotors obtained were placed in a graphite resistance heating atmosphere furnace and heated to 1700°C at a temperature increase rate of 100°C/hr while flowing nitrogen gas. After holding for 2 hours, the mixture was cooled in a furnace to obtain a ceramic sintered body. No defects such as cracks were observed in the sintered body obtained here, and a ceramic turbine rotor was obtained by finishing.

(Comparative Example 6) Using the same raw material as that used for injection molding of the wing portion 21 in Example 2, ten disk/shaft portions 23 shown in FIG. 14 were molded by injection molding.

Next, the obtained molded body was heated to 450° C. at a heating rate of 2.5° C./hr in the air to degrease it, and then cooled. Next, when the obtained shaft part molded and degreased body was examined, 1
Defects such as cracks were observed in all of the discs, and it was not possible to obtain molded and degreased discs and shaft parts that were free of defects by injection molding.

(Comparative Example 7) A kneaded body in which 46% by volume of an organic binder having the same composition as the raw material used for forming the shaft portion 23 in Example 2 was added to the dry powder was mixed with the same stirring type heating kneader as in Example 2 and Banbury. It was produced using a mold kneader, and 10 disc/shaft parts 23 were molded by injection molding under the same conditions as in Comparative Example 6, and then degreased. However, in this case as well, the degreased bodies obtained were all found to have defects such as cracks, making it impossible to manufacture disks and shafts by injection molding.

(Example 3) S having an average particle size of 1.5 pm and consisting of 90% or more α phase
A as a pressureless sintering aid to 85 parts by weight of i3N4 powder
A mixed powder was prepared by adding 10 parts by weight of JljzO3 powder and 5 parts by weight of Y2O3 powder, and performing sufficient wet mixing and pulverization in a ball mill.

When molding the wing section, 15 parts by weight of polyethylene resin as an organic binder and 10 parts by weight of microcrystalline wax were added to 100 parts by weight of the mixed powder, and dibutyl phthalate 5 main part was heated and kneaded as a lubricant. Thereafter, it was injection molded into the shape of the wing section 11 shown in FIG. Next, the organic binder was removed by heating and degreasing the molded product, and then a rubber coating was applied to the molded product, and the density was adjusted by hydrostatic pressing at a pressure of 2 tons 7 cm 2 .

On the other hand, when molding the moving part, 10 parts by weight of methyl cellulose as a binder was added to 100 parts by weight of the mixed powder.
0.1 part by weight of zinc stearate was added as a lubricant to form a slurry, which was then granulated using a spray granulator. Next, the obtained granulated powder was molded into the shape of a shaft by isostatic pressing of 0.5 tons and 7 cm2, and one end of the obtained molded body was processed into a conical shape to form the shaft shown in FIG. Part 13 was molded.

Next, the obtained molded body was heated and degreased to remove the binder and the like, and then a rubber coating was applied to the molded body, and the density was adjusted by applying a pressure of 3 tb.

Subsequently, the fitting hole 12 of the molded/degreased body of the wing portion 11 and the conical taper part of the molded/degreased body of the shaft portion 13 are processed by matching the actual parts, and then the two are fitted and assembled. , after applying a rubber coating to this combination, 4 ton/am
A turbine rotor made of atmospheric pressure sintered silicon nitride is made by applying hydrostatic pressure at a pressure of 2 to combine and then heating and sintering it at 1700°C for 1 hour in a nitrogen atmosphere and under normal pressure. Obtained.

(Examples 4 to 13. Comparative Examples 8 and 9) In Example 3, the densities of the molded and degreased body of the wing portion and the molded and degreased body of the shaft portion were adjusted by isostatic pressure. In this case, the pressure applied during hydrostatic pressurization was changed or partially omitted. In addition, for comparison, samples in which density adjustment by isostatic pressure was not performed or density adjustment was performed excessively were also conducted. The results are shown in Table 1.
Shown below.

As shown in Table 1, particularly good results are obtained when the density of the wing molded body is the same as the density of the shaft molded body or when it is within ±5% of the density of the shaft molded body. I was able to do that.

Next, test pieces with a height of 4 mm+, a width of 10 mm, and a length of 25 mm were cut out from the sintered bodies of Example 6.10 and Comparative Example 8, and subjected to a bending test by three-point bending at room temperature and 1000'O. went. Note that this test was conducted at a loading rate of 0, 5 mm/min, and 7. Performed with a 20mm pan, each strength value is the average value of 5 trees at room temperature, 1ooo'0
In the case of , the average value of the three trees was used for evaluation.

The results are shown in Table 2. However, in Table 2 (tun 5f
As shown in Table 2, the theoretical sintered density of 3N4(7) was 3.32 g/cm3, and as shown in Table 2, Example 6. The bending strength at room temperature and 1000"C!, which is the most problematic in lO, is compared with Comparative Example 8.
It becomes higher than ψ.

As explained above, according to the present invention, a ceramic molded/degreased body molded by injection molding and a ceramic molded degreased body molded by isostatic pressing are combined and bonded, and then sintered. When obtaining a ceramic sintered body, the density of each ceramic molded and degreased body after degreasing, and more preferably the isostatic pressure bonding after combining both ceramic molded and degreased bodies. The density changes were adjusted so that they were similar to each other, and then both molded and degreased ceramic bodies were combined, and then both molded and degreased ceramic bodies were combined using hydrostatic pressure, and then sintered. (1) Compared to injection molding, which requires the addition of 40 to 50 volume % of an organic binder, molded products formed by isostatic pressing, which can be molded with 20 to 40 volume % of an organic binder, require a degreasing process. Since the amount of organic binder to be removed is much smaller, the wall thickness limit that can be degreased becomes larger even when the same organic binder is used. When manufacturing,
By molding complex-shaped parts by injection molding and molding thick-walled parts by isostatic pressing, it is possible to take advantage of the respective advantages of injection molding and isostatic pressing. (2) When the packing density of the ceramic powder in the compact is the same (2. A hydrostatically pressed compact with a small amount of organic binder has more pores from the beginning,
Since the pores function effectively as escape routes for volatile decomposition gas during degreasing, it is possible to effectively suppress the occurrence of degreasing defects such as explosions, especially in thick-walled parts. Unlike the injection molding method, it does not involve solidification from a molten material, so there are no blood vessels or residual stress caused by solidification shrinkage or thermal gradients, and from this point of view, the probability of degreasing defects is greatly reduced. It is possible to incorporate each feature into the ceramic sintered body, such as molding the parts where degreasing defects are less likely to occur by injection molding, and molding the parts where degreasing defects are more likely to occur by isostatic pressing. 4) In the isostatic pressing method, it is possible to select an organic binder that emphasizes degreasing properties rather than moldability.

This method has a number of excellent advantages such as the following, and has a significantly superior effect in that it is possible to obtain a large ceramic sintered body having a complicated and thick portion compared to the conventional method.

[Brief explanation of the drawing]

Figure 1 is a manufacturing process diagram showing an example of manufacturing a conventional ceramic sintered body, Figure 2 is a partial sectional view of a turbine rotor, and Figure 3 is a manufacturing process diagram showing another example of manufacturing a conventional ceramic sintered body. , Figure 4 is a graph showing the change in bulk density of each molded body when the wing part and moving part are molded by injection molding, and Figure 5 is a graph showing the change in bulk density of each molded body when the wing part is molded by injection molding and the shaft part is isostatically pressurized. A graph showing the change in bulk density of each conventional molded body when molded by molding, FIG. 6 is a manufacturing process diagram showing the manufacturing process of a ceramic sintered body in an embodiment of the present invention, and FIG. 8 and 9 are longitudinal cross-sections of a blade molded body and a shaft molded body, respectively, of a turbine rotor manufactured in an example of the present invention. The top view, front view, FIGS. 10, 11, 12, and 13 show the results of each molded product when the wing portion is molded by injection molding and the shaft portion is molded by isostatic pressure molding. Example 1. Comparative example 3. Comparative example 4. A graph showing changes in bulk density in Comparative Example 5,
FIG. 14 is a longitudinal cross-sectional view of an axial flow turbine rotor manufactured in an example of the present invention, and FIG.
It is a graph which shows the change of the bulk density of a shaft part). DESCRIPTION OF SYMBOLS 11... Blade part of a turbine rotor, 13... Shaft part of a turbine rotor, 20... Axial flow turbine rotor, 21...
...A blade portion of an axial flow turbine rotor, 23...A disk/shaft portion of an axial flow turbine rotor. Fig. 14 H Fig. 15 Tawara Sugiji Kae Toto (Tsu/C pi)

Claims (1)

[Claims] (1) Ceramic molding made by body 4 molding・11
(When a fat body and a ceramic molded/degreased body formed by isostatic pressure molding are combined and bonded and then sintered to obtain a ceramic sintered body, the ceramic molded φ degreased body formed by injection molding and , a ceramic molded Φ degreased body formed by isostatic pressure molding is conditioned so that the densities of each ceramic molded and degreased body approximate each other, and then both ceramic molded and degreased bodies are combined. A method for manufacturing a ceramic sintered body, which involves bonding both molded and degreased ceramic bodies using hydrostatic pressure and then sintering them.