JP4666791B2 - CONNECTED BODY AND METHOD FOR PRODUCING THE SAME - Google Patents

Description

【００４９】
本発明の試料Ｎｏ．２〜７、９〜１８、２１〜２６及び２８〜３０は、２０〜１８０μｍの厚みの接合部が設けられ、嵌合接合により２００ＭＰａ以上の高い引抜き強度を示した。
【００５０】
一方、比ｄ／Ｗが０．０４に満たない本発明の範囲外の試料Ｎｏ．１は、嵌合力が加わらないため引張り強度が１１０ＭＰａと低かった。また、比ｄ／Ｗが０．４を越えるに本発明の範囲外の試料Ｎｏ．８は、引抜き強度が１５０ＭＰａと低かった。
【００５１】
また、スラリーの収縮率が成形体の収縮率より大きい本発明の範囲外の試料Ｎｏ．１９は、嵌合力が加わらないため引抜き強度が１００ＭＰａと低かった。
【００５２】
さらに、接合部が１０μｍと薄い本発明の範囲外の試料Ｎｏ．２０は、嵌合の効果が不十分なため、引抜き強度が１２０ＭＰａと低かった。また、接合部が２５０μｍと厚い本発明の範囲外の試料Ｎｏ．２７は、引抜き強度が８０ＭＰａと低かった。
【００５３】
【発明の効果】
本発明の接合体は、接合部の収縮率を成形体の収縮率よりも小さくするとともに、その厚みを制御することによって、接合部に嵌合による圧縮力を発生せしめ、高い接合強度を実現することができる。
【図面の簡単な説明】
【図１】本発明の接合体を焼成前に形成した接合成形体の概略断面図を示すものである。
【図２】本発明の接合体の構造を示す断面図である。
【図３】本発明の複雑形状の接合体の接合状態を示す断面図である。
【図４】本発明の接合体の製造方法を用いて作製したセラミックノズルを示す斜視図である。
【符号の説明】
１、２・・・成形体
３・・・ペースト
５・・・接合成形体
１１、１２・・・焼結体
１３・・・接合部
１５・・・接合体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a joined body and a manufacturing method thereof, and more particularly to a joined body having a large size and / or complicated shape and high reliability at a high temperature and a manufacturing method thereof, and automotive parts such as a piston pin and an engine valve. And parts for heat engines such as gas turbine engine parts.
[0002]
[Prior art]
Conventionally, silicon nitride-based sintered bodies known as engineering ceramics have excellent heat resistance, thermal shock resistance, wear resistance, and oxidation resistance, so that they are particularly useful as parts for heat engines such as gas turbines and turbo rotors. Application is underway.
[0003]
Since silicon nitride is a difficult-to-sinter material, in order to improve the sinterability, a molded body in which rare earth element oxides such as Y ₂ O ₃ or aluminum oxide is added as a sintering aid to silicon nitride powder. It is known to obtain a sintered body that is fired under pressure and is composed of an amorphous grain boundary phase mainly composed of a silicon nitride crystal phase and composed of rare earth elements, silicon, aluminum, oxygen, and nitrogen.
[0004]
However, in order to produce a large and complex ceramic sintered body, a large machine tool is required to process the molded body, and complicated and complicated processing is required. Sometimes it is too complicated and difficult to process. It may become.
[0005]
Therefore, in order to obtain large and complex ceramics, a technique called bonding is used. For example, in Japanese Patent Application Laid-Open No. 5-270933, ceramic products are divided into several parts, sintered bodies having shapes of the respective parts are produced, slurry is applied to the joining surfaces, and joined by solid-phase joining by heat treatment. It has been proposed to form a body.
[0006]
Further, in order to improve the strength of the joint, joining by fitting is proposed in Japanese Patent Laid-Open No. 9-263455. In this method, the wing part degreased body molded by injection molding and the shaft part degreased body molded by isostatic pressing are fitted together to be joined.
[0007]
[Problems to be solved by the invention]
However, in the structure described in JP-A-5-270932, since the binder is glassy, the oxidation characteristics and strength characteristics at high temperatures deteriorate, so that heat engines such as automobile parts and gas turbine engine parts are used. There was a problem that it could not be used as a part for a car.
[0008]
In addition, when joining a plurality of sintered bodies with complex shapes, when stress is applied from the outside so that pressure is uniformly applied to the joints, weak parts are lost or cracks occur. In the case of joining, there is a problem that it is difficult to apply pressure.
[0009]
On the other hand, in the method described in JP-A-9-263455, although there is an effect of increasing the pulling strength by fitting, there is a limit to the shape that can be adapted, for example, a solid shape product such as a rotor is possible. There is a problem that it is not suitable for ring-shaped joining. Moreover, since a molded object was produced using two types of molding methods, it caused an increase in cost.
[0010]
Accordingly, an object of the present invention is to provide a bonded body that maintains high strength at a high temperature and has high reliability, and a manufacturing method for manufacturing the bonded body in a simple process.
[0011]
[Means for Solving the Problems]
The joined body of the present invention is based on the knowledge that by providing a joining layer having a composition with a small shrinkage ratio between molded bodies, stress due to a fitting force based on a shrinkage difference can be applied, and the joining force can be improved. Is. Since this bonding layer can use a ceramic having the same composition as the molded body, even when the bonding depth is relatively small compared to the bonding width, it can have high strength from room temperature to high temperature, In addition, since only the slurry is applied to the joint, the shape of the molded body is not affected.
[0012]
That is, a first silicon nitride member having a recess on the surface, a second silicon nitride member fitted in the recess, and 20 provided between the first and second silicon nitride members. A ratio d / W of the depth d of the recess to the maximum diameter W of the recess is 0.04 to 0.4, and the bonding strength is 200 MPa or more in terms of pullout strength. It is characterized by this.
[0013]
Accordingly, a highly reliable bonded body having a high strength even at a high temperature even in a complicated shape can be realized, and a ceramic component optimal for a heat engine can be provided. In addition, even when the depth of the bonded portion is relatively shallow, the bonding force is high and a highly reliable bonded body can be obtained.
[0014]
In particular, it is preferable that the amount of sintering aid contained in the joint is smaller than the amount of sintering aid contained in the silicon nitride member. Since the amount of sintering aid in the joint is smaller than that of the silicon nitride member, the firing shrinkage rate of the joint during firing can be made smaller than the firing shrinkage rate of the silicon nitride member. As a result, the compressive stress as described above is applied to the joint. It works as a fitting force, and it is possible to realize a higher pulling strength.
[0015]
In addition, the method for producing a joined body of the present invention includes a step of producing at least two molded bodies 1 and 2 with a mixed powder containing silicon nitride and a sintering aid, and a firing shrinkage smaller than the firing shrinkage ratio of the molded body. A step of producing a ceramic paste having a rate, a step of forming a recess on the surface of the molded body 1 such that a ratio d / W of the depth d to the maximum diameter W is 0.04 to 0.4, Applying the ceramic paste to at least one joint surface of the molded body 1 or the molded body 2 and fitting the molded body 2 in the recess to produce a bonded molded body; and And a step of obtaining a joined body by firing. By this method, even in a complex part, a compressive stress can be generated in the joint portion by a simple method, and a high joining force can be obtained.
[0016]
In particular, it is preferable that the paste contains silicon powder, and the content of the silicon powder is larger than the content of silicon powder contained in the plurality of molded bodies. Thereby, a joining layer with a small shrinkage rate can be obtained easily.
[0017]
Furthermore, it is preferable that the content of the sintering aid in the paste is smaller than the content of the sintering aid in the plurality of molded bodies. Thereby, a joining layer with a small shrinkage rate can be obtained more easily.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The joined body of the present invention is a joined body in which a plurality of silicon nitride sintered bodies are joined at a fitting portion. For example, as shown in FIG. Then, the paste 3 is applied or filled into the concave recess of the molded body 1, and the molded body 2 is inserted into the recess to form the bonded molded body 5. And this is baked and the joined body 15 which provided the junction part 13 between the some sintered compacts 11 and 12 as shown in FIG. 2 can be produced.
[0019]
When forming the joint portion 13, it is important that the shrinkage rate of the powder in the paste 3 is smaller than the shrinkage rate of the compacts 1 and 2. The compressive stress of the fitting is generated, and the joining can be strengthened.
[0020]
Here, when the maximum diameter of the joint is W and the depth of the joint is d, it is important that the ratio d / W of the depth d to the maximum diameter W is 0.04 to 0.4. 0.06-0.3, Furthermore, 0.08-0.2 are preferable. When the ratio d / W is less than 0.04, the fitting force is not sufficiently generated. Particularly, when the maximum diameter W is 30 mm or less, the depth is 1.2 mm or less, and has a high joining force and high reliability. This is because the joined body cannot be realized. Further, if the ratio d / W exceeds 0.4, handling becomes difficult, and bubbles are easily taken in at the time of joining, resulting in problems such as strength deterioration and sample breakage.
[0021]
Moreover, it is important that the thickness of the joint portion 13 is 20 to 200 μm. That is, if it is less than 20 μm, the joining force generated by the fitting is insufficient, and if it exceeds 200 μm, the stress applied to the sintered bodies 11 and 12 becomes high, and there is a possibility that a defect occurs in the joint 13. And in order to obtain higher joining strength, it is preferable to set it as the thickness of 40-150 micrometers especially 60-100 micrometers especially.
[0022]
And according to this invention, it is important that the drawing strength of the joined body 15 is 200 Mpa or more, and it becomes possible to adapt as structural components, such as an engine component and a gas turbine engine component. Further, in order to further increase the mechanical reliability, it is particularly preferably 250 MPa or more, more preferably 300 MPa or more.
[0023]
Further, the present invention has a complicated shape, for example, a structure in which a pair of members 21a and 21b made of a silicon nitride sintered body sandwich a plurality of columns 22 made of a silicon nitride sintered body, as shown in FIG. Therefore, it can be suitably used for joining in a shape in which the column 22 and at least one of the pair of members 21a and 21b are joined. That is, it is difficult to integrally form these shapes, and manufacturing by cutting is costly. In conventional joining, since sintered bodies are joined together, the accuracy is low due to deformation during firing. On the other hand, in the present invention, such a complex-shaped joined body can be realized with high accuracy and high strength by a simple and low-cost process.
[0024]
In particular, the support column 22 is fitted into the recess 24 formed in the members 21a and 21b, and the bonding layer 23 is provided inside the recess. And by setting the thickness of a junction part to 20-200 micrometers and ratio d / W to 0.04-0.4, drawing strength can be made 200 Mpa or more, and a reliable joining body is realizable.
[0025]
The joined body of the present invention configured as described above can generate a fitting force in a joined portion by a simple method even in a complicated part, particularly a ring shape, and can obtain a high joining force.
[0026]
Next, a method for producing the joined body of the present invention will be described.
[0027]
First, a molded body is produced. That is, a mixed powder containing silicon nitride and a sintering aid is produced, and a molded body is produced using the mixed powder by various known forming methods such as a press method, a CIP method, a casting method and the like. It is important that the joints of these molded bodies have a recess for fitting to at least one of a combination of a ring and a cylinder, a ring and a ring, or the like.
[0028]
Also create a paste. That is, a solvent is added to a mixed powder containing silicon nitride and a sintering aid to obtain a paste. Use of di-n-butyl phthalate (DBP), di-octyl phthalate (DOP), higher alcohols, hydrocarbons, etc. with high melting point as the organic solvent prevents evaporation of the solvent, and joining by slurry solidification during joining It is preferable in order to prevent defects.
[0029]
And it is important that the shrinkage rate of the mixed powder of the paste is smaller than the shrinkage rate of the mixed powder of the compact. The difference in shrinkage between the powder in the paste and the molded body is preferably 5% or more, particularly preferably 10% or more, and more preferably 12% or less. Specifically, depending on the shrinkage rate of the molded body, It is preferable to set the shrinkage ratio of the powder to 15% or less, particularly 10% or less, and further 8% or less in order to generate a fitting force at the joint and increase the joint strength.
[0030]
In order to generate such a fitting force, the composition in the paste may be similar to the composition of the molded body, but is preferably different. For example, by making the silicon content in the paste larger than the silicon content in the molded body, the shrinkage rate of the molded body can be made larger than the shrinkage rate of the paste, and the fitting portion is inserted into the recess. The molded body is clamped by the molded body having the recesses, and a compressive stress is generated to improve the pull-out strength.
[0031]
Moreover, it is possible to make the composition substantially the same as that of the sintered body after nitriding and firing, and by selecting a desired composition, it is possible to realize a bonded body with higher strength and higher reliability at a higher temperature. .
[0032]
Also, by making the content of the sintering aid in the paste smaller than the content of the sintering aid in the molded body, the same effect as when the silicon content is changed can be obtained, and high drawing Strength can be realized.
[0033]
Further, by reducing the amount of solvent, the shrinkage rate can be suppressed by increasing the powder concentration of the joining slurry, and the same effect as described above can be obtained.
[0034]
By fitting using such a method, the pulling strength is increased by generating a fitting force, and there is also an effect of improving the joining strength by increasing the area of the joining portion, and these two effects are combined. A bonded body having high temperature, high strength and high reliability can be obtained.
[0035]
The shrinkage ratio of the mixed powder of the paste indicates the shrinkage ratio measured from the dimensions before and after firing when the paste having a specific shape is dried and fired. Specifically, the paste is applied to a container or the like. And dried to obtain a molded body, and the shrinkage rate is measured.
[0036]
The bonded body is degreased as desired, and then fired in an inert atmosphere of 1700 to 1900 ° C, preferably 1750 to 1850 ° C. In order to improve the sinterability of the molded body and the bonding layer, a temperature of 1700 ° C. or higher is necessary, and in order to suppress decomposition of the sintering aid, it is important that the temperature is 1900 ° C. or lower.
[0037]
Moreover, the manufacturing method of the conjugate | zygote of this invention can be applied suitably for manufacture of the member which has a complicated shape. For example, the ceramic nozzle shown in FIG. 4 has a structure in which a pair of ring-shaped members 31a and 31b are sandwiched from above and below a plurality of vanes 32, and the ring-shaped members 31a and individual vanes 32 are joined to each other according to the present invention. In addition, the ring-shaped member 31b is similarly bonded to the individual vanes 32 to form the bonding portions 33, respectively.
[0038]
That is, the ring-shaped members 31a and 31b are provided with recesses, and the vanes 32 coated with paste are inserted into both ends thereof. After the whole is assembled, a pressure of 5 MPa or less is applied between the upper and lower ring-shaped members 31a and 31b. The ceramic nozzle can be manufactured by pressure bonding and firing.
[0039]
Here, the shrinkage rate of the slurry is smaller than the shrinkage rate of the molded body of the ring-shaped members 31a and 31b, and a fitting force is generated by sintering, so that the ring-shaped members 31a and 31b and the vane 32 are firmly joined. By setting the ratio d / W of the joined body to 0.04 to 0.4 and the thickness of the joined portion to 20 to 200 μm at the bottom and side surfaces of the recess, a pulling strength of 200 MPa or more can be realized.
[0040]
Conventionally, after the sintered body was produced, it was fired again for bonding. However, in the present invention, simultaneous firing is possible, and thus large-sized and complex-shaped parts can be created by a single firing. And a joined body having high strength and high reliability can be obtained by a simple method.
[0041]
【Example】
BET 10 m ² / g, α ratio 90% silicon nitride powder, purity 99.9% of the total amount of 90% by weight, purity 99.9%, average particle size 5 μm of Y ₂ O ₃ , Yb ₂ O ₃ , Nd ₂ O ₃ and Er ₂ O ₃ were added at a ratio of 10% by weight, and mixed for 24 hours using IPA as a solvent. The mixed slurry was dried, and 10% of the total amount of paraffin wax was added to the obtained mixed powder to adjust the particle size.
[0042]
Using this mixed powder, a molded cube having a length of 30 mm, a width of 30 mm, and a length of 30 mm was produced by a die press. And the hole of diameter 10.5mm and the depth shown in Table 1 was produced on one surface.
[0043]
Separately, a cylindrical shaped body having a diameter of 30 mm and a length of 30 mm was produced, and a cylindrical shaped body having a diameter of 10 mm and a length of 30 mm was obtained by processing.
[0044]
Moreover, the paste was produced. That is, silicon nitride powder used for producing the above-mentioned molded body, Y ₂ O _{3 having} a purity of 99.9% and an average particle diameter of 5 μm, Si powder having a purity of 99.9% and an average particle diameter of 5 μm, and DBP as a solvent (Dibutyl phthalate) was mixed at a ratio shown in Table 1 to prepare a paste for bonding.
[0045]
After this paste was applied to the bottom and the wall surface of the hole of the molded cube, the cylindrical molded body was inserted, dried and degreased, and fired under the firing conditions shown in Table 1. The cube part of the obtained joined body was fixed, the groove part was given to the cylindrical part, the breaking load was measured by pulling using that part, and it calculated as a drawing strength.
[0046]
In addition, the shrinkage rate of the paste was measured by measuring the shrinkage rate from the dimensions before and after firing by filling only the paste in a separate container and drying it, firing it under the same firing conditions as the joined body. Further, the shrinkage rate of the molded body was 20%.
[0047]
Furthermore, the bonding surface was observed with an optical microscope photograph, and the thickness of the bonding layer was measured. The results are shown in Table 1.
[0048]
[Table 1]

[0049]
Sample No. of the present invention. 2-7, 9-18, 21-26, and 28-30 were provided with 20-180-micrometer-thick junction parts, and showed high pulling strength of 200 MPa or more by fitting joining.
[0050]
On the other hand, the sample No. in which the ratio d / W is not less than 0.04 is outside the scope of the present invention. No. 1 had a low tensile strength of 110 MPa because no fitting force was applied. In addition, when the ratio d / W exceeds 0.4, the sample No. In No. 8, the drawing strength was as low as 150 MPa.
[0051]
In addition, sample Nos. Out of the scope of the present invention have a slurry shrinkage ratio larger than that of the molded body. No. 19 had a pulling strength as low as 100 MPa because no fitting force was applied.
[0052]
Furthermore, the sample No. 5 outside the scope of the present invention has a thin junction of 10 μm. No. 20 had a pull-out strength as low as 120 MPa because the fitting effect was insufficient. In addition, the sample No. 4 outside the scope of the present invention was thick with a junction of 250 μm. In No. 27, the drawing strength was as low as 80 MPa.
[0053]
【The invention's effect】
In the joined body of the present invention, the shrinkage rate of the joint portion is made smaller than the shrinkage rate of the molded body, and the thickness is controlled to generate a compressive force due to fitting in the joined portion, thereby realizing high joint strength. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a bonded molded body formed by firing the bonded body of the present invention before firing.
FIG. 2 is a cross-sectional view showing the structure of the joined body of the present invention.
FIG. 3 is a cross-sectional view showing a joined state of a complex shaped joined body of the present invention.
FIG. 4 is a perspective view showing a ceramic nozzle produced by using the method for producing a joined body according to the present invention.
[Explanation of symbols]
1, 2 ... Molded body 3 ... Paste 5 ... Bonded molded body 11, 12 ... Sintered body 13 ... Joint 15 ... Joint body

Claims (5)

A first silicon nitride member having a recess on the surface, a second silicon nitride member fitted into the recess, and 20 to 200 μm provided between the first and second silicon nitride members. The ratio d / W of the depth d of the recess to the maximum diameter W of the recess is 0.04 to 0.4, and the bonding strength is 200 MPa or more in terms of pullout strength. Characteristic joined body. 2. The joined body according to claim 1, wherein the amount of the sintering aid contained in the joint is less than the amount of the sintering aid contained in the silicon nitride member. A step of producing at least two shaped bodies 1 and 2 with a mixed powder containing silicon nitride and a sintering aid, a step of producing a ceramic paste having a firing shrinkage ratio smaller than the firing shrinkage rate of the shaped body, A step of forming a recess on the surface of the molded body 1 such that a ratio d / W of the depth d to the maximum diameter W is 0.04 to 0.4, and a recess of the molded body 1 or of the molded body 2 The method comprises a step of applying the ceramic paste to at least one joint surface, fitting the molded body 2 in the concave portion to produce a joint molded body, and a step of firing the joint molded body to obtain a joined body. The manufacturing method of the joined body characterized by these. The method for producing a joined body according to claim 3, wherein the paste contains silicon powder, and the content of the silicon powder is larger than the content of silicon powder contained in the plurality of molded bodies. The method for producing a joined body according to claim 3 or 4, wherein the content of the sintering aid in the paste is smaller than the content of the sintering aid in the plurality of molded bodies.

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