JPS62138370A - Method of joining ceramic bodies - 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 [Field of Industrial Application] The present invention relates to a joining method suitable for obtaining ceramic bodies having complex shapes with high precision.

[Conventional technology]

Compared to metals, ceramics have superior high-temperature strength, wear resistance, and chemical corrosion resistance. Research and development is being carried out. Its uses are wide-ranging, including high-temperature structural materials such as refractories and heat exchangers.

From heat-resistant materials such as gas burners to automobile engine parts.

Many things are being researched, ranging from precision mechanical parts such as gas turbine parts.

Incidentally, when ceramics are used as engine parts, they generally have complex shapes such as rotors, stators, cylinders, pistons, valve bodies, etc., and require strict dimensional accuracy as high-precision mechanical parts.

When manufacturing these complex-shaped parts from ceramics, it is extremely difficult to obtain high precision by integral molding during the molding process, so it is necessary to create separate molded parts at the design stage to minimize stress on the joints. It is said that the best method is to separate the parts and then join them together.

As bonding methods for this purpose, methods using various inclusions such as metal brazing agents and oxide adhesives, and methods using a solid phase reaction by dobresses have been proposed.

However, in methods using various bonding agents such as metal brazing agents and oxide adhesives, the bonding strength at high temperatures is insufficient compared to the base material. Furthermore, when bonding is performed under normal pressure, when a liquid phase is interposed in the bonded area, air bubbles are drawn in and cause U-weave defects, and it is difficult to obtain a uniform No.F bonding structure. Unreliable.

Furthermore, a bonding method that utilizes a solid phase reaction using uniform hot pressing requires pressurization at high temperatures, which increases the cost of equipment and imposes restrictions on the equipment.

[Problems to be Solved by the Invention] The problems to be solved by the present invention are to eliminate the conventional drawbacks of obtaining a ceramic molded body having a complicated shape, and to The purpose is to obtain a joint having the same strength as the material, and to provide a highly reliable ceramic body with a complex shape.

[Means for solving problems]

The present invention uses ceramic bodies with air permeability above a certain level as objects to be joined, and a sheet-shaped green molded body made of ceramic powder and binder of the same type as the ceramic bodies to be joined is interposed between the joining surfaces, and then they are pressed together. Under crimping pressure, binder solvent is applied to the sheet-like green molded body using a capillary through open holes in the body to be bonded to soften it and completely fill the bonding gap, and then undergoes a drying and firing process to chemically bind the solvent. Get a bond. It is something.

Ceramics forming the objects to be joined in the present invention include non-oxide ceramics such as nitrides such as silicon nitride and aluminum nitride, carbides such as silicon carbide and boron carbide;
Oxide-based ceramics such as alumina, zirconia, and mullite can be optionally used.

The objects to be bonded have an air permeability that meets British Standards (BS Part IA) in order to allow the capillaries to penetrate the solvent in the binder that forms the sheet-like green molded object described below.
: 10-6ml by 19665ect 5)
-cm/cM-sec It is necessary to have an air permeability of H20cm or more.

As objects to be joined having such air permeability, a pre-fired ceramic body or a molded object in the process of reacting and changing into ceramics can be obtained as a bonding object; It can be used suitably. Particularly, the objects to be joined during the reaction have high strength, can withstand the load caused by machining, are easy to cut, etc., and can be processed with excellent dimensional accuracy.

As the sheet-like green molded body interposed at the joint surface, use a ceramic having the same composition as the base material constituting the joined body, or a substance that becomes ceramic with the same composition as the base material by subsequent heating or reaction. You can also do it. Substances that can be turned into ceramics include inorganic substances such as hydroxides and salts, metals such as aluminum and silicon that react with nitrogen or carbon monoxide, etc. to form nitrides or carbides, and those that are heated together with organic substances. Materials that can be turned into ceramics by treatment can be used. However, hydroxides, salts, etc. are not suitable because they generate gas during the reaction and the volume changes significantly before and after the reaction.

In addition, binders are solid at room temperature and soluble in specific solvents, and do not maintain their properties as a binder even if the solvent is scattered by heating or vacuum drying when the binder is made into a solution. Use something that won't damage it. The solvent used is one that does not have any physical or chemical effects such as volume change, weight change, chemical change, etc. on the objects to be joined. Such binder and solvent combinations include PVA and water.

Examples include phenol resin and ethanol, acrylic resin and acetone, organosilicon polymer compound and xylene, polyester resin and acetone, PVA and ethanol, etc.

The green, which is a combination of the above ceramic or ceramic material powder, binder, and solvent, to be interposed on the joint surface is in the form of a sheet with a thickness that is uniform and sufficiently filled in the joint gap, and has a thickness of about 0.5 to 10 mm. The thickness shall be .

This green sheet is subjected to surface grinding at the joint portion of a pre-fired ceramic body having the above-mentioned air permeability or a molded body which is in the process of reacting and turning into ceramics, and the sheet-like green molded body is interposed and pressure bonded. Next, this green sheet is interposed between the joining surfaces of the materials to be joined and pressure is applied.

Pressurization is preferably carried out in a vacuum in a direction perpendicular to the bonding surfaces, using the objects to be bonded as a medium. When the bonding is carried out in a vacuum, there is no generation of structural defects due to the inclusion of air bubbles at the bonding interface, and a ceramic bonded body with extremely high reliability can be obtained.

By this, in the middle of Ha Indah? The container dissolves the binder in the sheet-like green molded body through the continuous open holes in the object to be joined by capillaries, softens the sheet-like green molded body, and deforms and fills the sheet-like green molded body while turning it into a slip-like shape, thereby forming a sheet-like green molded body. The ceramic powder or substance that becomes ceramic through heating or reaction is brought into contact with each other and the bonding surfaces of the objects to be bonded, and a bonding interface is formed by bonding with the binder in the sheet-shaped green molded body in the gap between the bonding surfaces of the bonded bodies. .

However, the pressure applied in this process should not compress and destroy the sheet-like green molded product in the areas where the solvent has not penetrated, and must not discontinuously break the sheet-like green molded product that has been softened by the penetration of the solvent at the joint interface. The pressure needs to be within a range that satisfies the following conditions: that the sheet-like green molded product, which has been softened by penetration of the solvent, can be continuously deformed in the joint interface.

The air permeability of the object to be joined is 10' m 1-cm/ci-
If secH is 20 cm or less, there are very few open holes in the object to be joined, so the penetration of the solvent into the object is not observed, and the solvent cannot be supplied to the sheet-like green molded object, making it impossible to join. becomes.

As a result of the experiment, the permeation rate of the solvent into the objects to be bonded was determined as follows:
It decreases significantly below H20C1fi. Therefore, the air permeability of the object to be bonded should be at least 10' ml-cm/cI.
+! -5ec H20cm or more, preferably 10J5m
ll ・Cm/cA ・sea H must be 20cm or more.

In addition, when firing a bonded body with the above-mentioned green molded body interposed at the bonded interface, the shrinkage rate of the green molded body is It is desirable to make it as small as possible, and good results can be obtained by setting it to about 5% or less. Further, for the same reason, it is desirable that the thickness of the bonded interface obtained by softening and deforming the sheet-like green molded product is approximately 0.11 mm or less. Thereby, it is possible to obtain a ceramic bonded body with excellent dimensional accuracy of the bonded portion.

Since the sheet-like green molded body uses the same type of starting material as the object to be joined or the same type of starting material that will become the same type of ceramic, the bonded interface has the same chemical composition and chemical bond as the base material and material, and is continuous and uniform. It has a texture. Therefore, drying,
The ceramic bonded body after firing has extremely excellent dimensional accuracy.

Therefore, according to the present invention, it is possible to obtain a ceramic bonded body having extremely excellent dimensional accuracy and a physically and chemically continuous structure, and furthermore, the present invention can easily bond ceramics having complex shapes.

(Example) Example 1 A green molded body made of the ceramic powder and binder shown in Table 1 was pre-fired to obtain a ceramic pre-fired body having the air permeability shown in the table.

Table 1 Using the obtained ceramic calcined bodies as objects to be joined, test pieces of 4 (bm
m) was polished using a grinder, and this polished surface was used as the bonding surface.

A green molded sheet of 50 cranes x 15 mm x l fins with the compounding composition shown in Table 2 was interposed between the joint surfaces of two processed objects of the same type to be joined, and the pressure shown in the table was applied to each in a vacuum of -750 mmHg. At the same time, the various solvents shown in the table were permeated into the sheet-like green formed body through the continuous holes in the body to be bonded, and the green body was softened and deformed to obtain a bonded body.

Table 2 After drying the resulting bonded products, they were fired under the firing conditions shown in Table 3 to obtain ceramic bonded products. Secondary electron images of the joints of the various ceramic joints obtained were observed using a scanning electron microscope in a cross section perpendicular to the joint surface. No distinction was observed, and the entire ceramic bonded body had a continuous and uniform structure.

Furthermore, a test piece for measuring bending strength of 50 mm x 5 mm x 5 mm was cut out with the joint surface as the center, and subjected to a room temperature bending test. The results and the bending strength of the base material are shown in the same table. From the same table, it can be seen that the strength and reliability of the joint are on the same level as the base material.

Table 3 Comparative Example 1 In the bonding of Example 1, the solvent was permeated into the sheet-like green molded body under no pressure, and the other conditions were the same as in Example 1. Under these conditions, no softening deformation of the sheet-like green molded body was observed, and it was impossible to join.

Example 2 In the bonding process of Example 1, the sheet-like green molded body was softened and deformed by penetration of a solvent and pressurization in the air, and other conditions were the same as in Example 1 to obtain various ceramic bonded bodies. Table 4 shows the room temperature bending strength of the joint of the obtained ceramic joint.

As is clear from Table 4, when the bonding was performed in the atmosphere, the reliability of the bonded portion was slightly inferior to that in Example 1, in which the bonding was performed in a vacuum.

Table 4 1μ Example 3 A green molded body made of 90% by weight of silicon powder with a particle size of 44μ or less and 10% by weight of an organosilicon polymer compound was calcined at 800°C in a nitrogen atmosphere to give an air permeability of 4×IQ- 5m
l! A silicon pre-fired body of -C11l/Cut-5ec H20 was obtained. 4Qm@X40 from the obtained silicon calcined body
Test pieces measuring 1011 mm x 10 mm were cut out, and their joint surfaces (40 iris x 10 mm) were polished using a grinder, and this polished surface was used as the joint surface. A sheet-like green molded body of 50 mm x 15 mm x l + u consisting of 80% by weight of silicon powder with a particle size of 44μ or less and 20% by weight of an organic silicon polymer compound was interposed between the bonding surfaces of the two processed objects to be bonded. , 3k under vacuum of -700mmHg
g/cII! While applying pressure of As a result, a silicon nitride ceramic bonded body was obtained. Secondary electron image observation of the resulting joint between the silicon nitride ceramic and the bonded body using a scanning electron microscope from a cross section perpendicular to the joint surface revealed that there was no distinction between the base material and the joint interface at the joint. It was not recognized and had a continuous homogeneous structure.

Furthermore, a specimen measuring 50 sn x 5 mm x 5 m was cut out for bending strength measurement centering on the joint surface, and a bending test was performed at room temperature. As a result, the bending strength was 35 kg/n2. Weibull coefficient is 2
It was 5. The bending strength of the silicon nitride ceramic base material is 36 kg/Ryu 2. The Weibull coefficient was 30, and the strength and reliability of the joint were equivalent to that of the base metal.

Comparative Example 2 In Example 3, the green molded body was pre-fired at 1300°C in a nitrogen atmosphere, and the air permeability was 5X10-7ml-c.
Preliminary firing of m/cnt-see H20 was obtained. Joining was performed under the same conditions as in Example 3 except that the obtained fired bodies were used as objects to be joined. Under these conditions, no penetration of the solvent into the objects to be joined was observed. Therefore, it was not possible to penetrate the solvent into the sheet-like molded bodies, and it was impossible to join them.

Example 4 Instead of the green fired body shown in Example 3, 4
Example 3 Using a green molded body made of 95% by weight of silicon powder with a particle size of 4 μ or less and 5% by weight of polyester resin
Calcination was performed under the same conditions as above to obtain a silicon calcined body, and further 4
A sheet-shaped green molded body made of 90% by weight of silicon powder with a particle size of 4 μ or less and 10% by weight of polyester resin, and acetone used as a solvent to penetrate into the sheet-shaped green molded body, other conditions being the same as in Example 3. A silicon nitride ceramic bonded body was obtained. The structure of the obtained joint has a continuous uniform structure, and the bending strength of the joint is 28 kg / m
@2°Weibull coefficient was 12. Since the bending strength and Weibull coefficient of the base material were each 30 kg/II2, the joint had the same strength and reliability as the base material. A method for obtaining a joint of the same quality as a ceramic base material without affecting the rotor without special equipment.

This method is suitable for obtaining precision mechanical parts with high dimensional accuracy, such as stakes, cylinders, and piston 3-valve bodies.

Claims (1)

[Claims] 1. Has continuous ventilation holes and has an air permeability of 10^-^6ml.
A sheet-like green molded body made of a ceramic powder of the same type as the molded body or a substance that turns the same type of ceramic into a ceramic and a binder is interposed between the bonding surfaces of a ceramic molded body of cm/cm^2・secH_2Ocm or more, and bonded. Next, under pressure, the solvent of the binder in the sheet-like green molded body was supplied to the sheet-like green molded body through the open holes in the object to be joined, and the sheet-like green molded body was softened and filled into the bonding gap. A method for joining ceramic bodies, which is characterized by further drying and firing.