JPH0362668B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an adhesive for ceramic members and a bonding method using the adhesive, and particularly to a ceramic member suitable for partially bonding a large member to another member. The present invention relates to an adhesive for use with the adhesive and a bonding method using the same.

[Prior Art] In recent years, ceramic members such as silicon carbide, silicon nitride, sialon, aluminum oxide, and zirconium oxide have been known to have excellent mechanical strength at high temperatures, heat resistance, and thermal shock resistance. Since then, it has been attracting a lot of attention. There are many uses for these ceramics, such as gas turbine rotors and combustors, diesel engine cylinders, and other high-temperature machine parts, but all of them have strict requirements for shape and dimensional accuracy, so they must be molded as one piece from the beginning. This is often difficult.

For this purpose, the partial products are glued together,
It is necessary to finish products with complex shapes, and it is desired to develop a method for firmly joining ceramics together or ceramics and other members such as metals.

Conventionally, ceramic members have generally been joined by a so-called hot press joining method in which an adhesive is interposed between the ceramic members and pressure is applied at high temperature, or a joining method using an inorganic adhesive.

[Problems to be Solved by the Invention] The hot press joining method described above is not suitable for joining dissimilar members with different coefficients of thermal expansion because it is difficult to bond members with complex irregular shapes and requires high temperature heating. .

In addition, multiple types of inorganic adhesives are being developed, and various types are manufactured and marketed in Japan. However, many of these inorganic adhesives are usually based on silica, alumina, or zirconia, and although they are heat resistant, they have the disadvantage of being weak against forces that would cause the adhesive surface to peel off. be.

In addition, in the above conventional joining method, when heating the joining portion during joining, it is necessary to insert the entire member to be joined into a heating device such as a furnace and heat the entire member. Therefore, it is not suitable for joining large members, and the thermal energy required for joining must be large.

Brazing is a bonding method that has higher bonding strength than such inorganic adhesives. By the way, the conditions for brazing ceramics are that the objects to be bonded are wetted by the brazing material and that the material to be bonded and the brazing material are tightly bonded. Ceramics generally have poor affinity for molten materials (so-called wettability),
Furthermore, because of its low reactivity with various substances, it is not always possible to obtain sufficient brazing strength. Furthermore, as a matter of course, the heat resistance of the joint is limited by the heat resistance of the brazing filler metal, and at temperatures higher than the upper limit temperature of the brazing filler metal, the bonding strength becomes extremely low.

[Means for Solving the Problems] In order to solve the above problems, the adhesive for ceramic members of the present invention contains an inorganic adhesive containing 1 to 60 parts by weight per 100 parts by weight of the inorganic adhesive. It is mixed with part by weight of graphite powder.

Therefore, the method for joining ceramic members of the present invention comprises mixing an inorganic adhesive with 1 to 60 parts by weight of graphite powder per 100 parts by weight of the inorganic adhesive between the members to be joined. The two members are brought into contact with each other with the adhesive for ceramic members of the present invention interposed therebetween, and after drying, the joined portion is heated by high frequency induction heating to join the two members.

The present invention will be explained in detail below.

The adhesive for ceramic members of the present invention is added to an inorganic adhesive in an amount of 1% by weight per 100 parts by weight of the inorganic adhesive.
~60 parts by weight of graphite powder is mixed in.

The inorganic adhesive may be one that can be cured by heating to obtain adhesive strength, and various conventionally used inorganic adhesives, such as inorganic binders such as alkali silicates and phosphates, and binders may be used. A curing agent and a filler can be used to accelerate the curing of the curing agent.

Specifically, the following adhesives may be mentioned.

Alkaline silicate adhesive Alkaline silicate adhesive is used as a binder.
Potassium silicate, lithium silicate, sodium silicate commonly known as water glass, etc. are used, and among them, sodium silicate is used most often.

Silica sol adhesive Silica sol adhesive uses silica sol as a binder. This silica sol is a polymeric silicic acid colloidal solution using water as a dispersion medium, and the colloidal particles have a very fine size of 10 to 100 mμ, and are usually stabilized with cations such as Na ions.

Phosphate-based adhesives Phosphate-based adhesives use various metal phosphates such as aluminum phosphate and magnesium phosphate as binders.

Halide-based adhesives Consists of halides, alumina, silica, rare earth elements, etc. The halides include:
Metal halides and the like are used.

In the present invention, the graphite powder to be mixed into these inorganic adhesives may be either natural or synthetic, and its average particle size is 10 to 500 μm, particularly
A thickness of about 50 to 300 μm is preferable. The average particle size is
If the thickness is less than 10 μm, the efficiency of high-frequency induction heating is low.
Furthermore, if the average particle size exceeds 500 μm, large pores are formed when the graphite is oxidized and volatilized by heating, resulting in a decrease in adhesive strength.

By mixing graphite powder into an inorganic adhesive, high-frequency induction heating becomes possible, and heating converts graphite into oxides (carbon monoxide or carbon dioxide).
It evaporates and the joint becomes porous. This improves thermal shock resistance and is particularly advantageous for joining members having different expansion coefficients.

1 to 60 parts of graphite powder per 100 parts by weight of inorganic adhesive
It is suitable to incorporate it in a proportion of 5 to 30 parts by weight, preferably 5 to 30 parts by weight. If the amount of graphite powder mixed in is too large, the adhesive strength will decrease, and if it is too small, the efficiency of high frequency induction heating will decrease.

The adhesive for ceramic members of the present invention may further contain metal powder in addition to graphite powder.

In this case, the metal powder to be mixed preferably has an average particle size of about 10 to 500 μm, particularly about 50 to 300 μm. When the average particle size is less than 10 μm, the efficiency of high-frequency induction heating is low. Furthermore, if the average particle size exceeds 500 μm, foreign matter will be mixed into the adhesive layer, resulting in a decrease in adhesive strength.

Preferably, the metal is one that can be easily induction heated by high frequency, specifically Al, Si, Fe, Co, Cr, etc., and metals of the same type as the elements contained in the inorganic adhesive used, for example, In the case of phosphate adhesives made of aluminum phosphate, as metal powder.
In the case of an alkaline silicate adhesive made of sodium silicate, it is preferable to use Si powder as the metal powder instead of Al powder.

By mixing metal powder into an inorganic adhesive, high-frequency induction heating becomes possible, and the metal is oxidized during heating to become a metal oxide, making the bonded part dense and giving the bonding layer high strength.

The adhesive for ceramic members of the present invention can be heated by induction using high frequency waves, and since it is based on an inorganic adhesive, it has extremely high adhesive strength even at high temperatures.

Next, a method of bonding ceramic members according to the present invention using such an adhesive for ceramic members will be described.

The method of the present invention can also be used for joining ceramic members together.
Alternatively, it is applicable to joining ceramic members and non-ceramic members, but is particularly suitable for joining ceramic members together. In that case, however, the ceramics may be of the same type or may be of different types.

In the method of the present invention, there are no particular limitations on the type or shape of the ceramic members to be joined. The non-ceramic members to be joined include various metals and alloy members.

In the present invention, the aforementioned adhesive for ceramic members is interposed between the members to be joined, and after drying the adhesive, only the joint portion is heated by high frequency induction heating.

The amount of adhesive interposed between the members to be joined varies depending on the heating conditions, the type of the members to be joined, the type of adhesive, etc. Generally, when the adhesive layer is a porous layer, that is, when a relatively large amount of graphite powder is mixed into the adhesive, it is preferable to use a relatively large amount of graphite powder.

The high-frequency induction heating method may be a commonly employed method, and is performed in the atmosphere by setting a high-frequency induction coil or the like. The higher the frequency of the high frequency, the more advantageous it is because high frequency induction heating can be performed even when the particle size of the graphite powder mixed in the adhesive is small, but if the frequency is too high, it is not economical. The frequency of the high frequency is preferably in the range of 400 to 500 KHz.

During high-frequency induction heating, it is preferable to pressurize the members to be joined and apply pressure to the adhesive layer. When graphite powder and metal powder are mixed in the adhesive, it is extremely preferable because the adhesive layer becomes relatively dense and strong when pressed. It is effective to apply pressure within a range smaller than the strength of the members to be joined, and to apply pressure particularly during heating.

The heating temperature varies depending on the type of adhesive. In the case of alkaline silicate adhesives, the temperature is 200 to 300℃ because low temperature baking is possible, but in the case of silica sol adhesives it is around 500℃, and in the case of phosphate adhesives it is 300 to 300℃. 600°C, or 1000-1200°C in the case of halide adhesives.

The graphite powder in the adhesive turns into carbon dioxide or carbon monoxide through the above heating step. In this case, there is no problem even if the graphite remains in the adhesive layer as it is after heating without being oxidized. Furthermore, when metal powder is further contained, this metal powder becomes a metal oxide by the heating process.

[Function] By mixing graphite powder into the inorganic adhesive, it becomes possible to perform high frequency induction heating.
As a result, the formed adhesive layer becomes porous and has excellent thermal shock resistance. Further, when metal powder is further mixed, the adhesive layer becomes relatively dense and its strength is improved.

When bonding is performed using high-frequency induction heating, the heating temperature can be easily controlled. [Examples] The present invention will be explained in more detail below using Examples and Comparative Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example 1 By the method of the present invention, alumina ceramics of 15 mmφ×3 mmt and steel of the same shape were bonded.

An adhesive consisting of an alumina phosphate adhesive mixed uniformly with artificial graphite particles (volume ratio 15%) with an average particle size of 80 μm was placed between the alumina ceramics and the steel, and the adhesive was inserted into a 400 KHz high frequency coil. After preheating to about 200°C, heating at 700°C for 30 minutes, and then slowly cooling. As a result, both test pieces were well bonded.

When the bonded test piece was held at 400℃ and then placed in ice water to cool it rapidly, the bonded part cracked (peeled).
It was found that the bonded portion had excellent thermal shock resistance.

Comparative Example 1 Using a test piece with the same shape and the same material as in Example 1, using an alumina phosphate adhesive that does not contain any graphite particles as the adhesive, the entire test piece was heated in a furnace to bond it. I did it.

When the bonded test piece was kept at 200℃ and then placed in ice water to cool it rapidly, the joint part cracked (peeled).
did not occur. However, the test piece was heated to 300°C.
When the adhesive was held at a temperature and then rapidly cooled in the same manner, the adhesive part peeled off.

[Effects] As detailed above, according to the adhesive for ceramic members and the bonding method of the present invention, high-frequency induction heating in the atmosphere can be employed. Therefore, heating can be performed without charging the entire member to be welded into a furnace as in the conventional method, and the work is extremely easy. In addition, since there is no need to expose the entire part to be joined to high temperatures,
The influence of thermal stress on the members to be joined can be reduced.

According to the method for joining ceramic members using the adhesive for ceramic members of the present invention, the heating temperature can be easily controlled, and ceramic members can be joined with extremely simple operations.

The invention is therefore particularly advantageous for joining other parts to large ceramic parts in the field.

Claims (1)

[Scope of Claims] 1. An adhesive for ceramic members, which is prepared by mixing 1 to 60 parts by weight of graphite powder with respect to 100 parts by weight of the inorganic adhesive for bonding ceramic members. 2. In a method of bonding ceramic members together or a ceramic member and a non-ceramic member using an adhesive, between the two members, 1 to 60 parts by weight of an inorganic adhesive is added to 100 parts by weight of the inorganic adhesive. A method for joining ceramic members, characterized in that both members are brought into contact with an adhesive mixed with graphite powder interposed therebetween, and the joined parts are joined by high-frequency induction heating to heat the joined parts. 3. The method for joining ceramic members according to claim 2, wherein the members are pressed together in the joining direction when heating the joining portion.