JPS61111976A - Ceramic turbine rotor and manufacture - 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 (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 bonded using a bonding material such as ceramic paste. The present invention relates to a ceramic turbine rotor that is integrally joined without intervening, 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 and are less susceptible to oxidative corrosion and creep deformation, so research into using them as engine parts has been active in recent years. is being carried out. 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 automotive turbocharger rotors, gas turbine rotors, etc. is attracting attention as

Since such a turbine rotor has blades with a complicated three-dimensional shape,
For example, it is nearly impossible to finish a rod-shaped or square-shaped material such as a dense silicon nitride or silicon carbide sintered body into a desired shape by grinding, and it is also impossible to finish it in a single molding operation. It is extremely difficult to obtain a molded body with such a complicated shape, and the different performance requirements such as strength for each part of the rotor make manufacturing using such a method difficult.

For this reason, traditionally, 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 joined together.
Methods of forming a single product have been studied. For example, Japanese Patent Application Laid-open No. 57-88201, which was previously filed by the applicant of the present application.
The publication describes a method for manufacturing a rotor in which a wing section made of a ceramic molded body and a wing support section made of a ceramic molded body are fitted via ceramic paste and joined together by sintering, and the rotor On the line connecting the intersection between the shaft and the plane formed by the back surface of the blade and the curved surface formed by the center line between the blades relative to the rotor's central axis, the distance from the intersection to the joint surface is d, and this joint is When the distance from the surface to the curved surface is d2, d≧d2, and the manufacturing method is such that both molded bodies are joined into an integral structure by pressureless sintering so that the wing support portion is not exposed on the front surface of the wing portion. It has been revealed.

That is, in a radial type turbine rotor as shown in FIG. 2, a complex-shaped blade portion 4 having a plurality of blades 2 is formed by, for example, injection molding, while a rod-shaped blade support portion 6 is formed. For example, by molding with a mold press, the wing part 4
a joint surface 8 forming a truncated conical curved concave surface provided on;
A truncated cone-shaped curved convex joining surface 10 formed at the tip of the wing support part 6 is applied with ceramic paste and fitted together, and the molded body on the rear side is pressureless sintered to join them together. Manufactured by:

In addition, in this 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 wing section 4
and the curved surface 14 formed by the center line between the blades 2.2 with respect to the central axis S of the rotor, the distance from the intersection Q to the joint surface 8.10: dl, and the curved surface from the joint surfaces 8 and 10. 14 has a relationship of d≧d2, and the tip of the wing support portion 6 is configured so as not to be exposed to the front surface 16 of the wing portion 4.

In this way, the ceramic molded bodies of the wing part 4 and the wing support part 6 can be designed separately according to the characteristics required for them, and since they have the relationship d, ≧d2, 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 to the front surface 16 of the wing part 4,
When joining them, it is possible to press them together with a large amount of pressure, resulting in good bonding strength, and since the joint is not exposed, even if sudden thermal shock is applied, the effect on the joint is alleviated. In addition, corrosion due to high temperature gas is prevented.

(Problems) However, even with such an excellent manufacturing method as previously proposed, there remains a problem that remains to be solved. Both joint surfaces8.
(a) In the manufactured ceramic turbine rotor, since the joint is made using ceramic paste interposed between (b) The thickness of the paste applied to the bonding surfaces 8 and 10 becomes uneven, which tends to reduce the bonding strength; and (c)
(d) Joint surface 8. It is necessary to moisten the ceramic molded bodies of the wing portion 4 and the wing support portion 6 during joining, and therefore, it is necessary to pre-calcinate the molded bodies to give strength to the molded bodies; (d) Joint surface 8. l
To remove the binder of the paste applied to O,
There were problems such as the need for calcination before firing.

Here, the main object of the present invention is to eliminate all of the above-mentioned drawbacks found in the conventional joining method of ceramic molded bodies, and to join the ceramic molded bodies by using a gap ring at the joint portion. The goal is to prevent defects. Another object of the present invention is to eliminate the bonding layer made of ceramic paste, increase the reactivity between ceramics, and increase the bonding strength. Furthermore, another different 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 accompany the use of paste, and to improve the performance of ceramics and turbine rotors. The aim is to shorten the manufacturing process.

(Solution Means) In order to achieve this object, a ceramic turbine rotor according to the present invention includes a rotor in which an integrally molded wing portion and a wing support portion made of a ceramic molded body are integrally joined by sintering. and, as described above, the distances d, d2 have the relationship d1≧d2, and the wing support portion is not exposed on the front surface of the wing portion, and the connection between the wing portion and the wing support portion is It is characterized by having no bonding material on the surface.

Moreover, such a ceramic turbine rotor can be suitably manufactured by the following manufacturing method according to the present invention.

That is, in the method of manufacturing a rotor in which a wing part made of a ceramic molded body and a wing support part made of a ceramic molded body are fitted, isostatically pressurized, and then joined together by sintering, the porosity of each is 39. The ceramic molded bodies constituting the wing portion and the wing support portion are respectively prepared so that the difference in isostatic pressure shrinkage rate is 0.5 to 55% and 0.5% or less, and Distance: d, as in
, d.

After the wing part and the wing support part are consolidated by isostatic pressure without using ceramic paste so that d, ≧d2 and the wing support part is not exposed on the front surface of the wing part Both molded bodies are joined into an integral structure by pressureless sintering.

In short, in the method of the present invention, by controlling the porosity and shrinkage rate of the wing section and the wing support section made of ceramic molded bodies and applying isostatic pressure to them, the ceramic molded bodies are The joining operation can be significantly simplified since the joining can be realized without intervening the joining paste as in the past on the joining surface, and the presence of the joining paste on the joining surface can significantly simplify the joining operation. The conventional operations such as calcination before joining, preparation of paste, and calcination before firing are no longer necessary, and the presence of the joining paste on the joint surface can reduce the joining strength. Problems such as the occurrence of defects due to air entrainment can also 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 them. 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 porosity [
= (true specific gravity - bulk specific gravity) X100/true specific gravity] is 39.5 ~
55%, more preferably within the range of 45-50%,
Moreover, the isostatic pressure compression shrinkage rate under those same conditions [=
(Dimensions before isostatic static pressure - dimensions after isostatic static pressure) x
100/dimensions before isostatic static pressure application] difference is 0.5% or less,
The content is 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 the porosity and isostatic pressure shrinkage rate of the ceramic molded bodies to be joined within a predetermined range, it is possible to simply It has become possible to effectively join and integrate them only by applying isostatic pressure, and when combining ceramic molded bodies with porosity and shrinkage rate differences outside of this range, isostatic pressure according to the present invention is required. It becomes difficult to effectively join them by 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 the occurrence of cranks, etc. during firing. It is preferable that it be formed as follows.

The shrinkage rate of each ceramic molded body is determined by determining the isostatic pressure shrinkage rate and firing shrinkage rate of each molded body and fired body under the same conditions. 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, the ceramic molded body that provides such a predetermined porosity and isostatic pressure shrinkage rate difference is formed into a shape that can provide the desired ceramic turbine rotor by combining them, but the form of the combination is It will be selected as appropriate. For example, in the radial type turbine rotor as shown in FIG. 2, the blade portion 4 and the blade support portion 6 are each separately provided with the above-mentioned void ratio, as shown in FIG. 1(a). It is prepared so that it satisfies the following and has 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, other molding methods may also be employed. Furthermore, even if the wing support section 6 obtained by other molding methods (die press molding, etc.) is combined with the wing section 4 made of an injection molded body, as long as the above-mentioned porosity and shrinkage rate difference are satisfied. , it is possible to effectively join these molded bodies. Furthermore, the ceramic molded body used in the present invention may contain a small amount of the binder used during the molding operation, or it may be one from which such binder has been removed after molding, or a ceramic molded body that has strength added to the molded body. Even if it has been calcined for the purpose of making it more durable, it is equally acceptable.

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 joint surfaces, in other words, a shape that allows them to be brought into close contact without forming a gap. be. For example, in the illustrated turbine rotor, as shown in FIG. It has a concave surface and a curved convex surface. Although it is desirable that the joining surfaces (8, 10) of such a ceramic molded body be formed into a truncated conical shape as illustrated, it is also possible to adopt other fitting structures.

In addition, both ceramic molded bodies, whose joint surfaces have been processed into a shape that essentially blends into each other, can be brought into contact with their joint surfaces without intervening any number of ceramic pastes as in the past. In order to further apply isostatic pressure to the fitted bodies, the entire surface of the fitted bodies is made of an elastic material such as latex rubber, as shown in FIG. 1(b). body 18
It will be covered with.

Next, while the fitted body is covered with the elastic body 18, the entire body is pressurized by a normal isostatic pressurization method, thereby consolidating 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 mating surfaces (joining surfaces) to form an integral body. An operation to join the parts is performed. In short, by applying this isostatic static 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. 1(b), As a result, the wing portions 4 and the wing support portions 6, which are ceramic molded bodies, are subjected to pressure from all directions, effectively pressurizing them.
While being compressed and densified, the wing section 4 and the wing support section 6 are effectively brought into close contact with each other at their joint 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 the joint surfaces 8 and 10 at the same time as they are compressed, as described above, the respective ceramic molded bodies, i.e. It is necessary to regulate the porosity of the wing section 4 and the wing support section 6 as well as the difference in isostatic pressure shrinkage ratio between them, and only by such regulation can it be possible to use the bonding paste for the first time. without doing,
This made it possible to join ceramic molded bodies.

Note that this isostatic pressure pressurization operation for integrating ceramic molded bodies by compression and crimping can be performed according to normal procedures, and the pressure at that time depends on the respective ceramic moldings. The pressure is appropriately selected so that the body can be effectively compressed and the joint surfaces of the ceramic molded bodies can be crimped and bonded to form an effective integral structure, but in terms of -C, it is about l ton / cJ. As mentioned above, preferably a pressure of about 2 ton/cnf or more is employed. The reason for this is that the isostatic pressure shrinkage rate of each ceramic molded body to be joined is 1.5.
This is because it is preferable for bonding and integration to be at least 2.5%, preferably at least 2.5%.

In addition, in the case of a molded body bonded product in which both ceramic molded bodies are integrally bonded by this isostatic pressure pressurization method, there is no bonding paste at the bonding interface, and each molding Since the materials that make up the body are integrally joined, there are problems caused by the bonding paste itself, such as a decrease in bonding strength due to uneven coating thickness and defects caused by air entrainment. , they are not equally triggered.

The thus obtained integral molded body bonded product is then heated and sintered under normal pressure in accordance with a conventional method to form a strong ceramic turbine rotor of the desired shape.

In other words, each of the ceramic molded body parts that make up the integral bonded product obtained by isostatic pressure pressurization is simultaneously pressureless sintered into one piece, so that no cranks or the like occur at the bonded part. As shown in FIG. 1(c), a radial turbine rotor of the desired shape is completed.

The wall thickness at the joint between the wing part 4 and the wing support part 6 is such that the distance d shown in FIG. Front side 1 of wing section 4
It is set not to expose from 6 onwards, and as a result,
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 in detail above based on the drawings, the present invention should not be construed to be equally restrictive by these descriptions. The ceramic turbine rotor may have a shape other than the above, and it is also possible to employ a manufacturing method other than the manufacturing method according to the present invention.

(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 without using a bonding material such as ceramic paste as in the past. Because 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 their bonding strength is improved. This effectively suppresses the occurrence of defects such as poor bonding due to air contained in the bonding material or non-uniformity in the coating thickness of the bonding material.

In addition, since no ceramic paste is used in its production, operations such as calcination of the ceramic molded body before joining, preparation of the paste, and calcination of the molded body before firing are required when using such a paste. This made it possible to advantageously shorten the air time required for manufacturing (joining operation) the intended ceramic turbine rotor, thereby lowering manufacturing costs and improving productivity.

(Examples) Next, in order to clarify the present invention more specifically, Examples according to the present invention are shown in Table 1. Among the examples in Table 1, (a)+, (b), (g).

(h) will be explained. In addition, in the description of the examples, a plurality of rotor blades and a plurality of shafts are manufactured, but
This is to confirm the characteristics as necessary in carrying out the present invention. It should be noted that the present invention can be implemented in various embodiments in addition to the detailed description of the present invention described above and the examples shown in Table 1, and as long as it does not depart from the spirit of the present invention, it will be understood by those skilled in the art. It should be understood that any of the various embodiments that can be implemented based on knowledge are within the scope of the present invention.

Example 1 5t3N mixture for pressureless sintering in which 2 parts by weight of 5r0, 3 parts by weight of Mg0, and 3 parts by weight of CeO were added as sintering aids to 100 parts by weight of Si, N, powder with an average particle size of 1 μm. was prepared. 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 portion 4 after firing was 50 mm.

Then, when three bodies were sampled from the plurality of molded bodies (4) obtained and the density of the molded bodies was determined, it was found to be 2.1
It was 6g/cc. Next, the remaining molded body 4)
400 at a heating rate of 3°C/hr in an electric furnace.
Degreasing was carried out by heating to 0.degree. C. and further holding at that temperature for 5 hours.

Several pieces were sampled from the plurality of molded bodies (4) after this degreasing, and the density, porosity, and 2.5 ton/c of the molded bodies were determined.
The n1 isostatic static pressure shrinkage rate and density were determined. Molded object (4)
The porosity was 47.1%. The results are shown in Table 1 (
Shown in a).

On the other hand, using the Si, N, and mixture for pressureless sintering prepared above, 100
Isostatically compressed with a rubber press at a pressure of 0 kg/ad,
A plurality of shaft molded bodies were obtained. Several pieces were sampled from the plurality of molded bodies obtained, and the density, porosity, and contraction rate under isostatic static pressure of 2.5 ton/crA,
The density was 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 isostatic pressure shrinkage ratio between the wing section 4 and the wing support section 6 is 0.
It was 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 joint surfaces 8.10 of the plurality of blade parts 4 and the plurality of blade support parts 6 obtained in this way are smoothed by lathe processing so that they are substantially mutually connected so that d, ≧d2. After processing the wing parts 4 and wing support parts 6 into a shape that fits well, the wing parts 4 and the wing support parts 6 are fitted together, and the entire fitted body is hermetically covered with latex rubber. By applying isostatic pressure by performing a rubber press at a pressure of
A plurality of joined molded bodies were obtained by joining them together.

When observing the obtained plurality of joined molded bodies, it was found that
No cranks were found anywhere in these joined molded bodies.
The wing portion 4 and the wing support portion 6 were firmly joined and integrated. In addition, several pieces were sampled from these bonded products, and the isostatic 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 Table 1 (a)
, shown in (b).

Next, the plurality of joined molded bodies obtained in this way were fired at 1720° C. under normal pressure in a nitrogen atmosphere for 30 minutes, and then precisely finished using a lathe to obtain the shape shown in FIG. 1(c). Several radial 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 joint interface between the blade portion 4 and the blade support portion 6. Furthermore, the blade section of the rotor (4
) and the density of the shaft portion (6) were measured. The results are shown in (a) and (b) in Table 1.

Comparative Example Using Si3N4 powder with an average particle size of 1 μm, the same procedure as in Example 1 was carried out, and as shown in (g) in Table 1, the density was 1.
A plurality of wing portions 4 having a weight of 76 g/cc, a porosity of 47.1%, and an isostatic pressure shrinkage rate of 3.2% were manufactured.

On the other hand, using the 5jsN4 mixture for pressureless sintering of the example,
1 so that the porosity of the obtained molded body is 47.1%.
Isostatic pressing was performed using a rubber press at a pressure of 300 kg/cog to obtain a plurality of shaft portion forming bodies corresponding to the blade support portion 6.

Several of these molded bodies were sampled in the same manner as in Example 1 and their properties were measured, and the results shown in (h) in Table 1 were obtained. The difference in shrinkage rate under isostatic pressure 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.

Then, the plurality of wing parts 4 and wing support parts 6 obtained in this way are
After smoothing the joint surfaces 8 and 10 using a lathe, they are fitted together, the whole is covered with latex rubber, and a rubber press is performed at a pressure of 2.5 tons/crA to form the wing section. 4 and the wing support part 6 were joined to obtain a plurality of integrated molded body joined products.

When the obtained joined molded product was observed, a crank was 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. .

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1(a), 1(b) and 1(c) are cross-sectional explanatory views showing one of the steps of the method of the present invention for manufacturing a ceramic turbine rotor, respectively. FIG. 2 is a sectional view showing an example of a conventional ceramic turbine rotor. 2 blades 4: wing section 6: wing support section 8.10: joint surface 12: plane 14: curved surface 16: front surface of wing section S2 rotor central axis Q: intersection point

Claims (8)

[Claims] (1) A rotor in which an integrally molded wing section and a wing support section made of a ceramic molded body are integrally joined by sintering, and the intersection of the central axis of the rotor and a plane formed by the back surface of the wing section. On the line connecting the center line between the blades of the wing and the curved surface formed with respect to the central axis of the rotor, the distance from the intersection point to the joint surface is d_1, and the distance from the joint surface to the curved surface is d_2. A ceramic turbine rotor having an integral structure, wherein d_1≧d_2, and having no bonding material on the bonding surface, and in which the blade support portion is not exposed at the front surface of the blade portion. (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) A method for manufacturing a rotor in which a wing section made of a ceramic molded body and a wing support section made of a ceramic molded body are fitted together, subjected to isostatic pressure, and then joined together by sintering, in which each air gap is Prepare the ceramic molded bodies constituting the wing portion and the wing support portion, respectively, so that the contraction rate is 39.5 to 55% and the difference in isostatic pressure shrinkage rate is 0.5% or less, Then, on a line connecting the intersection of the central axis of the wing support section and the plane formed by the back surface of the wing section and the curved surface formed by the center line between the blades of the wing section with respect to the central axis of the wing support section. , the distance from the intersection to the joint surface is d_
1. When the distance from the joint surface to the curved surface is d_2,
After the wing section and the wing support section are consolidated by isostatic pressurization without using ceramic paste, so that d_1≧d_2 and the wing support section is not exposed on the front surface of the wing section, A method for manufacturing a ceramic turbine rotor, which is characterized by joining both molded bodies into an integral structure by pressure sintering. (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 shrinkage rate under isostatic pressure of the ceramic molded body is 0.3% or less.