JPH0229633B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a ceramic turbine rotor and a method for manufacturing the same, and in particular, an integrally molded wing section and a wing support section made of a ceramic molded body are integrally joined without using a joining material such as ceramic paste. The present invention relates to a ceramic turbine rotor and a method for manufacturing the same. (Prior art) Silicon ceramics such as silicon nitride, silicon carbide, and sialon are more stable at high temperatures than metals.
Because it is resistant to oxidative corrosion and creep deformation,
In recent years, research into using it as engine parts has been actively conducted. In particular, radial turbine rotors made of these ceramic materials are lighter than metal rotors, can raise the operating temperature of the engine, and have excellent thermal efficiency, so they are used as turbocharger rotors for automobiles or gas turbines. It is attracting attention as a rotor, etc. Since such a turbine rotor has a blade portion having a complicated three-dimensional shape, it is difficult to use a simple sintered body such as a rod-like or square shape made of dense silicon nitride or silicon carbide sintered body. It goes without saying that it is nearly impossible to finish a shaped material into a desired shape by grinding, but it is also nearly impossible to finish a shaped material into a desired shape with just one forming operation.
It is extremely difficult to obtain a molded body with such a complicated shape, and the different performances such as strength required outside the rotor make manufacturing using such a method difficult. For this reason, conventionally, the ceramic molded product that provides the final product, the turbine rotor, is divided into a complex-shaped blade part and a rod-shaped blade support part, which are then molded and then joined together to form a single product. methods are being considered. For example, in Japanese Patent Application Laid-Open No. 57-88201, which was previously filed by the applicant of the present application, a wing portion made of a ceramic molded body and a wing support portion made of a ceramic molded body are fitted together via a ceramic paste, and then sintered. A method of manufacturing a rotor that is integrally joined by a line that connects the intersection of the central axis of the rotor and the plane formed by the back surface of the blade and the curved surface that the center line between the blades forms with respect to the central axis of the rotor. , the distance from the intersection to the joint surface is
d ₁ , and the distance from this joint surface to the curved surface is
When d ₂ , a manufacturing method has been disclosed in which both molded bodies are joined into an integral structure by pressureless sintering so that d ₁ ≧d ₂ and the blade support portion is not exposed on the front surface of the blade portion. That is, in the case of a radial turbine rotor as shown in FIG. 2, a complex-shaped blade portion 4 having a plurality of blades 2 is formed, for example, by injection molding, while a rod-shaped blade support portion 6 is formed. For example, by molding with a mold press, a joining surface 8 forming a truncated conical curved concave surface provided on the wing section 4 and a truncated conical curved convex surface formed at the tip of the wing support section 6 are formed. The joint surfaces 10 are manufactured by applying ceramic paste thereon and fitting them together, and then sintering both molded bodies under pressure to join them together. In addition, in such a joined state, the intersection point Q between the central axis S of the rotor and the plane 12 formed by the back surface of the blade section 4 and the center line between the blades 2 and 2 are relative to the central axis S of the rotor. On the line _connecting the curved _surface 14 _{created by} and is configured such that the tip of the wing support section 6 is not exposed to the front surface 16 of the wing section 4. In this way, the ceramic molded bodies of the wing section 4 and the wing support section 6 can be designed separately according to the characteristics required for them, and also, where the relationship of d ₁ ≧ d ₂ is satisfied. Therefore, the thickness of the blade support portion 6 at the joint portion is large, resulting in higher mechanical strength and sufficient resistance to high-speed rotation of the rotor. Furthermore, since the tip of the wing support part 6 is not exposed on the front surface 16 of the wing part 4, when joining them, it is possible to press them together with a large pressure, and good joint strength is obtained, and the joint part is Since it is not exposed, the effect on the joint is alleviated even if it is subjected to sudden thermal shock.
In addition, corrosion due to high temperature gas is prevented. (Problems) However, even with the excellent manufacturing method proposed above, there are still problems to be solved. That is, the wing section 4 and the wing support section 6
and are joined by the ceramic paste interposed between both joint surfaces 8 and 10. Therefore, in the manufactured ceramic turbine rotor, (a) (b) The thickness of the paste applied to the bonding surfaces 8 and 10 becomes uneven, which tends to reduce the bonding strength. In its manufacture, (c) it is necessary to moisten the ceramic molded bodies of the wing section 4 and the wing support part 6 during joining, and therefore it is necessary to pre-calcinate them to give strength to the molded bodies; (d) In order to remove the binder of the paste applied to the joint surfaces 8 and 10, it is necessary to perform calcination before firing. Here, the main purpose of the present invention is to solve all of the above-mentioned drawbacks found in conventional joining methods for ceramic molded bodies.
Another purpose is to prevent bonding defects due to voids in the bonded portions of these ceramic molded bodies. Also,
Another object of the present invention is to eliminate the bonding layer of ceramic paste, increase the mutual reactivity of the ceramics, and increase the bonding strength. Furthermore, another object of the present invention is to eliminate the need for operations such as calcination before bonding, preparation of paste, and calcination before firing, which are associated with the use of paste, and to produce ceramics and turbine rotors. The aim is to shorten the manufacturing process. (Solution Means) In order to achieve such an object, in the ceramic turbine rotor according to the present invention, the blade portion and the blade support portion, which are integrally formed from a ceramic molded body, are integrally joined and sintered. and the distances as mentioned above: d ₁ , d ₂ and d ₁
≧d ₂ , and the wing support portion is not exposed on the front surface of the wing portion, the density of the wing portion and the wing support portion are substantially the same, and the wing portion and the wing support portion are It is characterized by having no bonding material on the bonding surface. Moreover, such a ceramic turbine rotor can be suitably manufactured by the following manufacturing method according to the present invention. That is, after fitting the wing part made of the ceramic molded body and the wing support part made of the ceramic molded body, and compressing them by isostatic isostatic pressure to join the two molded bodies into a substantially closely integrated structure, In the manufacturing method of the sintered rotor, each porosity is
The ceramic molded bodies constituting the wing section and the wing support section were each prepared so that the difference in isostatic pressure shrinkage rate was 39.5 to 55% and 0.5% or less, and the ceramic molded bodies were prepared as described above. Distance: d ₁ , d ₂ is d ₁ ≧
In order to maintain the relationship of d ₂ and to prevent the wing support from being exposed on the front surface of the wing, the wing and the wing support are isostatically pressurized without using the ceramic paste, so that both molded bodies are substantially compressed. After bonding them into a closely integrated structure, they are fired under normal pressure. In short, in the method of the present invention, by controlling the porosity and shrinkage rate of the wing portion and the wing support portion made of ceramic molded bodies and applying isostatic pressure to them, the ceramic molded bodies are Since these can be joined without intervening the conventional joining paste on the joining surface, the joining operation can be significantly simplified, and the presence of the joining paste on the joining surface can significantly simplify the joining operation. , the conventionally required operations such as calcination before bonding, preparation of paste, and calcination before firing are no longer necessary, and furthermore, the presence of bonding paste on the bonding surface reduces the bonding strength. Problems such as the occurrence of defects due to air entrainment can now be effectively resolved. By the way, the ceramic material of the ceramic molded body constituting the wing section and the wing support section in the present invention includes silicon nitride, silicon carbide, sialon, or substances produced by firing. The ceramic molded body is selected as appropriate depending on the characteristics required for the ceramic body, and the ceramic molded body is first molded according to a known molding method such as an injection molding method. The plurality of ceramic molded bodies formed in this way all have a porosity [= (true specific gravity - bulk specific gravity) x 100/true specific gravity].
Within the range of 39.5 to 55%, more preferably 45 to 50%, and under the same conditions, isostatic pressure shrinkage [= (dimension before isostatic pressure - isostatic The molding is performed so that the difference in the dimensions (dimensions after hydrostatic pressurization) x 100/dimensions before isostatic hydrostatic pressurization is 0.5% or less, preferably 0.3% or less. Further, the vicinity of the joint is selected as a preferred site for dimensional measurement of the molded body. In this way, by controlling the difference in porosity and isostatic pressure shrinkage rate of the ceramic molded bodies to be bonded within a predetermined range, there is no need for a bonding paste as in the past. It has become possible to effectively join and integrate them simply by applying isostatic hydrostatic pressure, and in the case of a combination of ceramic molded bodies having a difference in porosity or shrinkage rate outside of this range, the present invention is effective. Therefore, it is difficult to effectively join them by isostatic isostatic pressure. In addition, the ceramic molded bodies constituting the wing parts and the wing support parts generally have a difference in firing shrinkage of about 3% or less in order to enable their integral firing and to avoid cracks during firing. It is preferable that it be formed as follows. Note that the shrinkage rates of each of these ceramic molded bodies are determined in advance by each molded body under the same conditions.
It is determined by determining the isostatic pressure shrinkage rate and firing shrinkage rate of each fired body. The shrinkage rate of each product after bonding is affected by the molded products that are bonded to each other, and varies somewhat from the shrinkage rate of a single product, but the variation is generally within the range specified by the present invention, Therefore, the present invention is not substantially affected even if the shrinkage rate is used as a standard. In addition, a ceramic molded body that provides such a predetermined porosity and isostatic pressure shrinkage rate difference,
It is said that the desired ceramic turbine rotor can be formed by combining them.
The combination form will be selected as appropriate.
For example, in the case of a radial turbine rotor as shown in FIG. 2, as shown in FIG. Moreover, they are prepared to have a predetermined difference in shrinkage rate. Note that although it is generally desirable that the wing portion 4 having a complicated shape be formed by injection molding, it is also possible to employ other molding methods. Further, even if the wing part 4 made of an injection molded body is combined with the wing support part 6 obtained by other molding methods (die press molding, etc.), the above-mentioned porosity and shrinkage rate difference will be satisfied. It is possible to effectively join these molded bodies insofar as possible. Furthermore, the ceramic molded body used in the present invention may contain a small amount of the binder used during the molding operation, or may contain a small amount of binder from which such binder is removed after molding, or it may contain a small amount of the binder used during the molding operation, or it may be one in which such a binder is removed after molding, or a ceramic molded body that has strength imparted to the molded body. There is no problem with it even if it has been calcined for the purpose of making it. The wing portion and the wing support portion made of the ceramic molded body formed in this way are processed into a shape that substantially fits each other at their joining surfaces, in other words, a shape that allows them to be brought into close contact without forming any gaps. be. For example, in the case of an exemplary turbine rotor, as shown in FIG.
are respectively corresponding curved concave surfaces and curved convex surfaces as described above. Note that the joint surfaces 8 and 10 of such a ceramic molded body
is desirably formed into a truncated conical shape as illustrated, but other fitting structures may also be employed. In addition, the two ceramic molded bodies processed into a shape in which the joint portions are substantially compatible with each other allow their joint surfaces to abut without any intervening ceramic paste as in the past. In order to further apply isostatic pressure to the mated bodies, the entire surface of the mated bodies is covered with an elastic material 18 such as latex rubber, as shown in FIG. 1b. It will be covered with. Next, while the fitted body is covered with the elastic body 18, the entire body is processed by a normal isostatic pressure pressurization method, thereby compressing the fitted body. In other words, the molded body itself is densified by isostatic compression using isostatic pressure, and both of the fitted ceramic molded bodies are tightly and crimped at their fitting surfaces (joining surfaces). ,
An operation for integrally joining is performed. In short, by applying this isostatic hydrostatic pressure, the fitted body of the blade part 4 and the blade support part 6 of the turbine rotor, which are airtightly surrounded by the elastic body 18, as shown in FIG. As a result, the wing section 4 and the wing support section 6, which are ceramic molded bodies, are effectively pressurized and compressed to become densified, and at the same time, the wing section 4 and the wing support section 6 are subjected to pressure from all directions. Support part 6
are effectively brought into close contact with each other at their joining surfaces 8 and 10 and become integrated.
In order to integrate the wing part 4 and the wing support part 6 by pressing and bonding them at their joint surfaces 8 and 10 at the same time as they are compressed, as described above, the respective ceramic molded bodies, i.e. Wing part 4
It is necessary to regulate the porosity of each of the blade supporting portions 6 and the isostatic pressure shrinkage ratio between them, and only by such regulation can the bonding paste be used for the first time. This made it possible to join ceramic molded bodies without any problems. In addition, compression of such a ceramic molded body,
The isostatic pressurization operation for integration by crimping can be carried out according to normal procedures, and the pressure at that time is such that the respective ceramic molded bodies are effectively compressed and The pressure at which the joint surfaces of these ceramic molded bodies are crimped and bonded to form an effective integral structure is selected as appropriate, but generally it is about 1 ton/cm ² or more, preferably about 2 ton/cm ² or more. pressure will be adopted. The reason for this is that the isostatic pressure shrinkage rate of each ceramic molded body to be joined is
This is because a content of 1.5% or more, preferably 2.5% or more is preferable for bonding and integration. In addition, in the case of a molded body bonded product in which both ceramic molded bodies are integrally bonded by this isostatic hydrostatic pressing method, there is no bonding paste at the bonding interface, and each Since the materials that make up the molded body are integrally joined, there are problems caused by the joining paste itself, such as a decrease in joint strength due to uneven coating thickness and defects caused by air entrainment. However, nothing is triggered. The thus obtained integral molded joint is then heated and sintered under normal pressure according to a conventional method to form a strong ceramic turbine rotor in the desired shape. . In other words, the parts of the ceramic molded body constituting the integral bonded product obtained by isostatic isostatic pressing are simultaneously sintered together under atmospheric pressure, which prevents cracks from occurring in the bonded parts. As shown in FIG. 1c, a radial turbine rotor with the desired shape is completed. In the ceramic turbine rotor obtained by pressureless sintering in this way, the densities of the blade portion and the blade support portion are substantially the same, so that the blade portion and the blade support portion have substantially the same density. Since there is no residual stress at the bonding interface with the other parts and the stress is uniform, it exhibits excellent performance against thermal stress and mechanical stress. The wall thickness at the joint between the wing part 4 and _the wing support part 6 is determined by the distance _{d 1} and d ₂ shown in FIG.
The following relationship is satisfied, and the tip of the wing support section 6 is connected to the wing section 4.
As described above, the blade support part 6 is set so as not to be exposed from the front surface 16 of the blade support part 6, and as described above, various advantages can be obtained, such as the mechanical strength of the wing support part 6 and the joint strength between the two parts being increased. Although the ceramic turbine rotor and the manufacturing method thereof according to the present invention have been described above in detail based on the drawings, the present invention should not be construed in any way limited by these descriptions, and for example,
The shape of the ceramic turbine rotor of the present invention may be any shape other than those described above, and it is also possible to employ manufacturing methods other than the manufacturing method according to the present invention described above. (Effects of the Invention) As described above, according to the ceramic turbine rotor of the present invention, the blade portion and the blade support portion made of the ceramic molded body can be bonded together without using a bonding material such as ceramic paste as in the past. Since the structure is integrally bonded without a bonding layer such as ceramic paste, the mutual reactivity of the ceramics in each molded body is effectively increased, and the bonding strength between them is improved. This effectively suppresses the occurrence of defects such as poor bonding due to air contained in the bonding material or uneven coating thickness of the bonding material. Moreover, since there is no difference in density between the wing section and the wing support section, there is no residual stress at the bonding interface and the stress is uniform, resulting in excellent performance against thermal stress and mechanical stress. In addition, since no ceramic paste is used in its production, operations such as calcination of ceramic molded bodies before joining, preparation of the paste, and calcination of the molded bodies before firing are required when using such pastes. This made it possible to advantageously shorten the manufacturing process (joining operation) of the desired ceramic turbine rotor, thereby lowering its manufacturing cost and improving its productivity. (Examples) Next, in order to clarify the present invention more specifically, Examples according to the present invention are shown in Table 1. 1st
Among the examples in the table, (a), (b), (g), and (h) will be explained. Further, in the description of the examples, a plurality of rotor blade portions and a plurality of shaft portions are each manufactured, but this is for the purpose of confirming the characteristics as necessary in accordance with the implementation of the present invention. It should be noted that the present invention can be implemented in various embodiments in addition to the above-mentioned specific explanation of the present invention and the examples shown in Table 1, and those skilled in the art will be able to understand the present invention without departing from the spirit of the present invention. It should be understood that any of the various embodiments that can be implemented based on the knowledge of the present invention falls within the scope of the present invention. Example 1 For 100 parts by weight of Si ₃ N ₄ powder with an average particle size of 1 μm,
A Si ₃ N ₄ mixture for pressureless sintering was prepared by adding parts by weight of SrO2, MgO3, and 3 parts by weight of _CeO2 as sintering aids. Then, 15% by weight of polyethylene wax and 2% by weight of stearic acid were added to a portion of the prepared mixture, and the mixture was heated and kneaded to prepare a ceramic raw material for injection molding. Next, in order to obtain the blades 4 of a ceramic turbine rotor as shown in FIG. 1, the ceramic raw material was injection molded to produce a plurality of desired blades 4. The mold used in this injection molding operation was of a size capable of producing a radial turbine rotor in which the maximum diameter of the blade section 4 after firing was 50 mm. Then, the obtained plural molded bodies 4 to 3
When the density of the molded product was determined by sampling the molded product, it was found to be 2.16 g/cc. Next, the remaining molded body 4 was heated at a heating rate of 3°C/hr in an electric furnace.
Degreasing was carried out by heating to 400° C. and further holding at that temperature for 5 hours. Several pieces are sampled from the plurality of molded bodies 4 after this degreasing,
The density, porosity, 2.5 ton/cm ² isostatic isostatic pressure shrinkage rate, and density of the molded body were determined. The porosity of the molded body 4 was 47.1%. The results are shown in (a) in Table 1. On the other hand, using the Si ₃ N ₄ mixture for pressureless sintering prepared above, the porosity of the compact was adjusted to 48.3%.
It was isotropically compressed using a rubber press at a pressure of 1000 Kg/cm ² to obtain a plurality of shaft molded bodies. Several pieces were sampled from the plurality of molded bodies obtained, and the density, porosity, 2.5 ton/cm ² isostatic isostatic pressure shrinkage rate, and density of the molded bodies were determined. The results are shown in (b) in Table 1. The porosity of the molded body was 48.3%. As shown in Table 1, the difference in shrinkage rate under isostatic pressure between the wing section 4 and the wing support section 6 was 0.1%. Then, using the remaining molded body, the tip thereof was lathe-processed into a truncated conical shape having a curved surface, thereby creating the wing support portion 6 shown in FIG. 1. The thus obtained joint surfaces 8 and 10 of the plurality of wing parts 4 and the plurality of wing support parts 6 are smoothed by lathe processing so that d ₁ ≧ d ₂ is substantially satisfied. After shaping them into shapes that fit each other, the wing parts 4 and the wing support parts 6 were fitted together, and the entire fitted body was hermetically covered with latex rubber. Then, a rubber press was applied at a pressure of 2.5 tons/cm ² . By applying isostatic hydrostatic pressure, a plurality of bonded molded bodies were obtained in which the wing portions 4 and the wing support portions 6 were integrally joined at their abutment joint surfaces 8 and 10. When we observed the obtained plurality of joined molded bodies, no cracks were observed in any of these joined molded bodies, and the wing part 4 and the wing support part 6 were firmly joined and integrated. It was hot. In addition, several pieces were sampled from these bonded products, and the isostatic hydrostatic pressure shrinkage rate and density of each of the molded bodies of the wing portion 4 and the wing support portion 6 were determined. The results are shown in (a) and (b) in Table 1. Next, the plurality of joined molded bodies obtained in this way are fired at 1720° C. for 30 minutes under normal pressure in a nitrogen atmosphere, and then precisely finished using a lathe to obtain the radial shape shown in FIG. 1c. Several type ceramic turbine rotors were obtained. When several pieces of the obtained turbine rotor were sampled and cut, no foreign phase was observed at the interface between the blade portion 4 and the blade support portion 6. Furthermore, the densities of the blade portion 4 and shaft portion 6 of the cut rotor were measured. The results,
Shown in (a) and (b) in Table 1. Comparative Example Using Si ₃ N ₃ powder with an average particle size of 1 μm, Example 1
Similarly, as shown in (g) in Table 1, the density is
A plurality of wing portions 4 having a porosity of 1.76 g/cc, a porosity of 47.1%, and an isostatic pressure shrinkage rate of 3.2% were produced. On the other hand, the Si ₃ N ₄ mixture for pressureless sintering of the example was isotropically compressed with a rubber press at a pressure of 1300 Kg/cm ² so that the porosity of the obtained molded body was 47.1%. A plurality of shaft forming bodies corresponding to the wing support portion 6 were obtained. Several of these molded bodies were sampled in the same manner as in Example 1, and their properties were measured.
The results shown in (h) were obtained. The difference in isostatic pressure shrinkage ratio between the wing section 4 and the wing support section 6 was 0.7%. Then, using a lathe, the tip of the molded body was processed into a curved truncated conical shape to produce the desired wing support portion 6. After smoothing the joint surfaces 8 and 10 of the plurality of wing parts 4 and the wing support part 6 obtained in this way using a lathe, they were fitted together, and the whole was covered with latex rubber. By performing a rubber press under a pressure of /cm ² , the wing portion 4 and the wing support portion 6 were joined to obtain a plurality of integrally joined molded bodies. When observing the obtained joined molded product, we found that
Cracks were observed from the joint between the wing section 4 and the wing support section 6 to between the blades 2, 2 of the wing section 4, and it was found that it was not suitable for subsequent use.

【table】

【table】 [Brief explanation of drawings]

Figures 1a, b and 1c are cross-sectional illustrations each showing one of the steps of the inventive method for manufacturing a ceramic turbine rotor. FIG. 2 is a sectional view showing an example of a conventional ceramic turbine rotor. 2: blade, 4: wing section, 6: wing support section, 8,
10: Joint surface, 12: Plane, 14: Curved surface, 16:
Front surface of wing, S: Center axis of rotor, Q: Intersection, d ₁ :
Distance from the intersection to the joint surface, _d2 : Distance from the joint surface to the curved surface.

Claims (1)

[Scope of Claims] 1. A rotor in which an integrally molded wing portion made of a ceramic molded body and a wing support portion are integrally joined and sintered, wherein the central axis of the rotor and the back surface of the wing portion constitute On the line that connects the _intersection with the plane of When the distance between is d ₂ , d ₁ ≧ d ₂ , there is no bonding material on the bonding surface, the densities of the wing part and the wing support part are substantially the same, and the wing support part is the same as the wing part. A one-piece ceramic turbine rotor that is not exposed at the front. 2. The rotor according to claim 1, wherein the ceramic molded body is made of silicon nitride, silicon carbide, or sialon. 3. The rotor according to claim 1 or 2, wherein the wing portion is formed of an injection molded ceramic body. 4 The wing section made of a ceramic molded body and the wing support part made of a ceramic molded body are fitted together and compacted by isostatic isostatic pressure to join both molded bodies into a substantially closely integrated structure, and then sintered. This is a method for manufacturing rotors that
% and the difference in isostatic pressure shrinkage rate is 0.5%
The ceramic molded bodies constituting the wing section and the wing support section are each prepared as follows, and the intersection of the central axis of the wing support section and the plane formed by the back surface of the wing section is connected to the wing section. On the line connecting the center line between the blades of the blade support section and the curved surface formed with respect to the central axis of the wing support section, the distance from the intersection point to the joint surface is _d1 , and the distance from the joint surface to the curved surface is _d2 . When d ₁ ≧ d ₂ and the wing support portion is not exposed on the front surface of the wing portion, the wing portion and the wing support portion are
A method for manufacturing a ceramic turbine rotor, which is characterized in that both molded bodies are joined into a substantially closely integrated structure by isostatic pressure without using a ceramic paste, and then fired under normal pressure. 5. The manufacturing method according to claim 4, wherein the ceramic molded body is made of silicon nitride, silicon carbide, or sialon. 6. The manufacturing method according to claim 4 or 5, wherein the wing portion is formed of an injection molded ceramic body. 7. The manufacturing method according to any one of claims 4 to 6, wherein the ceramic molded bodies constituting the wing portion and the wing support portion each have a porosity of 45% to 50%. 8. The manufacturing method according to any one of claims 4 to 7, wherein the difference in isostatic pressure shrinkage rate of the ceramic molded body is 0.3% or less.