JPH08196916A - Manufacture of honeycomb body by diffusion bonding - Google Patents

Abstract

PURPOSE: To use in a severe environment and manufacture simply a honeycomb body of high strength of a bonding section by applying flux to the honeycomb body composed of a flat plate and a corrugated plate of heat-resistant metal and then coating them with molten aluminum. CONSTITUTION: When a honeycomb body 1 composed by laminating a flat plate 2 with a corrugated plate 3 of heat-resistant is manufactured, first, flux 5 is applied to the flat plate 2 and the corrugated plate 3 and the honeycomb body 1 is formed, or the flux 5 is applied after forming the honeycomb body 1. Then molten aluminum is applied for coating to the honeycomb body 1 with the flux 5 on its surface. Successively the honeycomb body 1 is heated in the non-oxidizing atmosphere to diffusion bond the honeycomb body 1. In other words, an alloy layers 6 are formed on the surfaces of the flat plate 2 and the corrugated plate 3, and the above-said top layers are covered with aluminum layers 7. Then, aluminum on the surface of the honeycomb layer 1 is diffused inside a metal plate, and a bonding section (a) of the flat plate 2 with the corrugated plate 3 is diffusion bonded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method by diffusion bonding of a honeycomb body which constitutes a metal carrier carrying a catalyst for purifying exhaust gas.

[0002]

2. Description of the Related Art Since a metal carrier has advantages such as excellent temperature rising characteristics and impact resistance as compared with a ceramic carrier, it has been widely used in recent years as a carrier for an exhaust gas purifying catalyst for automobiles and the like. Generally, a metal carrier has a honeycomb structure, and is manufactured by inserting a honeycomb body in which flat plates and corrugated plates made of heat-resistant metal are alternately stacked into a cylindrical outer cylinder.

Conventionally, in a honeycomb body forming a metal carrier, a flat plate and a corrugated plate have been joined by a brazing material. However, it is not only technically difficult to accurately supply the brazing material to the necessary parts in the required amount, but also after the joining, the brazing material diffuses, which lowers the high temperature strength and oxidation resistance of the metal carrier. There was a problem.

On the other hand, a method of joining a flat plate and a corrugated plate by diffusion joining without using a brazing material has been developed. In this method, it is necessary to apply a high surface pressure to the contact surface between the flat plate and the corrugated plate in order to increase the bonding strength of the bonded portion, and the honeycomb body after winding is squeezed, or the flat plate and the corrugated plate are wound by the side clamp winding method. It was necessary to combine means such as winding up and the heat treatment. However, it is difficult to apply the effect of the drawing to the inside of the honeycomb body in the radial direction, and moreover, sufficient bonding strength cannot be obtained due to the deformation of the corrugated sheet, and the side clamp winding method requires a special honeycomb winding device. However, it was difficult to control various conditions such as winding load and heating conditions, and stable bonding strength could not be obtained.
Moreover, when the honeycomb body is strongly squeezed or wound with a high winding load, the metal plate is deformed or cut in some cases when the foil is a thin foil (thickness less than 30 μm) or a low strength foil, There is also a problem that thin foils and low strength foils cannot be used for this diffusion bonding.

In addition, a method of manufacturing a metal carrier by diffusion bonding after applying ultrafine powder of Ni or Al to the bonding portion in order to increase the strength of the bonding portion between the flat plate and the corrugated plate has been recently proposed. (Japanese Patent Laid-Open No. 5-131147).

[0006]

However, in the method described in the above-mentioned JP-A-5-131147, although the strength of the joint is improved to some extent, the area of the contact is small, so that the joint strength is still sufficient. However, when such a metal carrier is mounted in an exhaust system of an automobile or the like, the joint may be broken by being exposed to a severe temperature change, vibration, and a high temperature gas flow velocity. In addition, the above-mentioned conventional method requires a complicated operation of applying ultrafine powder to a specific portion, and has a drawback that productivity is inferior.

The present invention has been made in order to solve the above problems in the prior art, and in a severe environment of an exhaust system of an automobile or the like without requiring a special winding device for a honeycomb body. It is an object of the present invention to provide a method for more easily manufacturing a honeycomb body in which the joining portion between the flat plate and the corrugated plate, which can sufficiently withstand use, has extremely high strength.

[0008]

That is, a method for manufacturing a honeycomb body by diffusion bonding according to the present invention is a method for manufacturing a honeycomb body in which a flat plate of a heat-resistant metal and a corrugated plate are superposed on each other. After applying the flux to the corrugated sheet and then forming the honeycomb body, or after forming the honeycomb body and then applying the flux and coating the molten aluminum on the honeycomb body having the flux on the surface thereof, the above-mentioned honeycomb body is non-oxidizing. It is characterized in that the honeycomb body is diffusion-bonded by heating in an atmosphere (hereinafter, also referred to as a production method A).

According to the present invention, a honeycomb body formed by stacking a heat-resistant metal flat plate and a corrugated plate on top of each other is heated in an atmosphere of a substance capable of combining with iron to form a low melting point substance, thereby forming the honeycomb body. Diffusion bonding method for manufacturing a honeycomb body by diffusion bonding (hereinafter also referred to as manufacturing method B)
Regarding In a preferred embodiment of the above production method B, the pressure is reduced and cooled after the heat treatment.

The corrugated sheet and the flat sheet used in the present invention are made of a heat-resistant metal or a heat-resistant iron-based metal, and a conventional metal carrier such as a metal foil of stainless steel is used. In the production method B of the present invention, a heat resistant iron-based metal containing aluminum is usually used. On the other hand, in the production method A, although it may contain aluminum or may not contain aluminum, stainless steel containing no aluminum is preferable in terms of workability and cost.

The thickness and material of the corrugated plate and the flat plate may be appropriately selected, and both may be the same or different from each other. Note that when corrugated sheets and flat sheets with different surface roughness are selected, that is, metal foil with low surface roughness is used for the corrugated sheet, metal foil with high surface roughness is used for the flat sheet, or surface roughness is used for the corrugated sheet. When using a metal foil with a high thickness or a metal foil with a low surface roughness on a flat plate, even if wound with the same load, the contact area between the flat plate and the corrugated plate is small, so high surface pressure occurs and diffusion is promoted. It is possible to stably manufacture a metal carrier having high bonding strength.

In the present invention, the corrugated plate and the flat plate may be heat-treated after rolling, but at least one of the corrugated plate and the flat plate is not subjected to post-rolling heat treatment. It is preferable to use one.
Although many lattice defects are generated in the metal foil after rolling, by using it without heat treatment,
Since diffusion easily progresses through the lattice defects, it is possible to stably manufacture a honeycomb body having high bonding strength.

The size and shape of the honeycomb body formed by stacking the flat plate and the corrugated plate are not particularly limited. For example, the flat plate and the corrugated plate may be stacked alternately in layers, or the flat plate and the corrugated plate may be stacked. It may be overlapped and wound in a spiral shape to form a tubular shape.

Next, each step of the manufacturing method A of the present invention will be described. The flux may be applied to the surfaces of the flat plate and the corrugated plate before being formed into the honeycomb body, during forming, or after forming, and as the flux that can be used in the present invention, K ₂ ZrF ₆ , KAlF ₄ , K ₃ AlF is used. ₆ or a mixture thereof and the like. The method for applying the flux is usually a method in which a slurry prepared by dispersing the above substance or a mixture thereof in an organic solvent such as acetone or alcohol is applied mechanically or manually to flat plates and corrugated plates, preferably in a thin uniform manner, or It is carried out by immersing a flat plate and a corrugated plate or a honeycomb body in the flux slurry and then evaporating the organic solvent.

The honeycomb body formed of the flat plate and the corrugated plate coated with the flux in the above process or the honeycomb body coated with the flux, that is, the honeycomb body having the flux on its surface is coated with molten aluminum. This molten aluminum coating is
For example, immersing the honeycomb body in molten aluminum,
Alternatively, it is performed by pouring molten aluminum into the honeycomb body. When aluminum coating is performed by dipping here, when molten aluminum is supplied into the honeycomb by suction, more uniform and stable coating is possible, and as a result, a honeycomb body having a uniform bonding strength is obtained. Further, after coating, before the molten aluminum solidifies, by sending high pressure air to the honeycomb body,
Since the clogging of the honeycomb body is eliminated, this
It is possible to obtain a honeycomb body having a more uniform bonding strength.

The aluminum coated honeycomb body is then heated in a non-oxidizing atmosphere for diffusional fusion. In the present invention, the non-oxidizing atmosphere is a vacuum (eg;
A pressure of 10 ^-4 mmHg or less), an inert gas (eg, argon gas, nitrogen gas, etc.), or a reducing gas (eg, hydrogen gas, ammonia gas, etc.), preferably an inert gas and a reducing gas It is gas. The heating is carried out at a temperature and for a time sufficient for diffusing the aluminum on the surface into the metal plate. Preferably below the melting point of aluminum first,
For example, after the treatment at about 400 to about 600 ° C. for about 1 to about 10 minutes, the treatment is performed at the melting point of aluminum or higher, for example, about 1000 to about 1300 ° C. for about 1 to about 10 minutes. The honeycomb body after the heat treatment is allowed to cool or is forcibly cooled.

In the manufacturing method B of the present invention, the honeycomb body is heated in an atmosphere of a substance capable of forming a low melting point substance by combining with iron in the metal foil forming the honeycomb body. The substance forming the atmosphere in this method means a substance capable of combining with iron to form a low melting point substance which is a liquid at the heat treatment temperature, and examples thereof include hydrogen chloride (HCl) gas. By this heating, a reaction occurs between iron atoms (Fe) in the metal foil and the atmosphere substance, and a liquid phase made of a low melting point substance is formed in the vicinity of the joint such as a gap between the flat plate and the corrugated plate, and the liquid phase is formed. Diffusion proceeds through the layers, and the honeycomb bodies are diffusion-bonded.
For example, when hydrogen chloride gas is used, ferrous chloride (FeCl ₂ ) is generated in the vicinity of the joint due to the reaction between iron and hydrogen chloride.
Is formed, and diffusion proceeds through the liquid phase, and the honeycomb bodies are diffusion-bonded. The heat treatment in the production method B is usually about 1000 to about 1300 ° C. for about 30 to
It takes about 90 minutes. After the above heating, the honeycomb body may be allowed to cool, but by cooling by depressurizing the inside of the heating furnace to atmospheric pressure or less, the liquid phase is decomposed, the joint is densified, and the joint strength is higher. Is obtained. When hydrogen chloride gas is used as the atmosphere, the reduction reaction of ferrous chloride to iron proceeds, the joint is densified, and higher joint strength is obtained.

The metal carrier generally comprises a honeycomb body housed in an outer cylinder made of heat-resistant metal. In the present invention, the honeycomb body treated according to the above-mentioned manufacturing method A or B is inserted into the outer cylinder to mechanically. Alternatively, the honeycomb body may be integrated by brazing or the like, or the honeycomb body before treatment may be inserted into the outer cylinder and integrated, and then treated according to the above-mentioned manufacturing method A or B. In the latter case, it goes without saying that the honeycomb body and the outer cylinder are joined together by diffusion bonding.

[0019]

In the production method A of the present invention, the flux applied before the aluminum coating is melted and decomposed by the heat of the molten aluminum to promote the reaction between the aluminum and the honeycomb body, so that the aluminum penetrates inside the honeycomb body. In addition, the heating in a non-oxidizing atmosphere gas suppresses the evaporation of aluminum and promotes the diffusion of aluminum into the metal plate, so the flat plate and corrugated plate are joined together with a large contact area. A honeycomb body having sufficiently high bonding strength can be obtained.

Further, in the manufacturing method B of the present invention, the heating is carried out in a specific atmosphere that reacts with the metal plate forming the honeycomb body, so that the gap between the flat plate and the corrugated plate is separated from the metal plate and the atmosphere. Since the honeycomb body is filled with the liquid phase of the reaction product and diffusion bonding of the honeycomb body is promoted, the flat plate and the corrugated plate are bonded with a large contact area, and a honeycomb body having a sufficiently high bonding strength is obtained.

[0021]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples. Example 1 Step 1 A flat plate made of stainless steel (thickness: 50 μm, 20 Cr steel) and a corrugated plate are overlapped and spirally wound to manufacture a cylindrical honeycomb body. K ₂ ZrF as flux
After the honeycomb body was immersed in a slurry in which ₆ powders were dispersed in acetone, it was taken out, the solvent (acetone) was evaporated, and the flux (K ₂ ZrF ₆ ) Is applied thinly and uniformly. Step 2 The honeycomb body after applying the flux is then immersed in molten aluminum at 750 ° C. for 10 seconds. Step 3 Next, the honeycomb body coated with molten aluminum is heated in a vacuum furnace under a pressure of 10 ⁻⁴ mmHg at 550 ° C. for 5 minutes and at 1200 ° C. for 5 minutes, and then cooled.

FIGS. 2 to 4 are views schematically showing the state after the operations of the above steps 1 to 3 are completed. In all of the drawings, the joint portion a (see FIG. 1) between the flat plate and the corrugated plate is shown. The cross section is shown. First, as shown in FIG. 2, after step 1, the flux 5 is thinly and uniformly applied to the surfaces of the flat plate 2 and the corrugated plate 3. Next, in step 2, the flux 5 is melted and decomposed by the heat of the molten aluminum, and this reacts with the Cr passivation film on the surfaces of the flat plate 2 and the corrugated plate 3, activating the surface of the metal plate, and the aluminum and the metal. The plate surface reacts, and as shown in FIG. 3, an alloy layer 6 is formed on the surfaces of the flat plate 2 and the corrugated plate 3, and the upper layer thereof is covered with the aluminum layer 7. Next, in step 3, by heating the aluminum-coated honeycomb body, aluminum on the surface of the honeycomb body is diffused into the inside of the metal plate, and the joint portion a between the flat plate 2 and the corrugated plate 3 is diffused as shown in FIG. To be joined. Here, since the area of the joint portion a is larger than that of the conventional diffusion joint, the strength of the joint portion is very high.

In step 2, the honeycomb body taken out of the molten aluminum may be exposed to a high-pressure air stream to remove excess aluminum, whereby clogging of the honeycomb is prevented and a uniform aluminum coating is applied. A layer is obtained. Also, the molten aluminum coating in step 2 can be performed uniformly and stably by using a suction means. This is, for example, as shown in FIG. 5, a holder 10 connected to a pump 11 in a molten aluminum 9 in a container 8.
It may be performed by immersing the honeycomb body 1 attached to the above and then sucking it with the pump 11.

Example 2 A flat plate made of stainless steel (thickness: 50 μm, 20Cr-5Al steel) and a corrugated plate were superposed on each other and spirally wound to produce a cylindrical honeycomb body. Next, the honeycomb body was heated at 1200 ° C. for 1 hour in a heating furnace filled with a hydrogen chloride gas atmosphere.
After heating for an hour, allow to cool. As a result of the above operation, as shown in FIG. 6, a reaction between the surfaces of the flat plate 2 and the corrugated plate 3 and hydrogen chloride gas occurs (Fe + 2HCl → FeCl ₂ +
H ₂ ) and ferrous chloride (Fe) in the gap between the flat plate 2 and the corrugated plate 3.
Cl ₂ ), a liquid phase 12 is formed, diffusion progresses through the liquid phase 12, and diffusion bonding of the honeycomb body is promoted. As shown in FIG. Is obtained.

Example 3 The cooling after heating in the operation of Example 2 was replaced with standing cooling,
The heating furnace is decompressed to (10 ⁻³ mmHg). This allows the following reaction between the flat plate 2 and the corrugated plate 3: FeCl ₂ +
H ₂ → Fe + 2HCl progresses, the liquid phase 12 is decomposed, the joint a is densified, and the joint strength becomes higher.

Test Example A metal carrier (see FIG. 1) obtained by housing the honeycomb bodies 1 obtained in Examples 1 to 3 in an outer cylinder 4 made of stainless steel was sliced into 10 mm widths, and their horizontal planes were the upper and lower surfaces. As a result, it is placed on a doughnut-shaped die, pressed from above the metal carrier with a punch having a diameter of 15 mm, and the joint strength is calculated from the load required to punch the center of the metal carrier according to the following formula: S = P / n · t [wherein S = bonding strength (kgf / mm), P = load (k
gf), n = number of contact points between flat plate and corrugated plate (n = 2 in this test)
4), t = thickness in the cutting direction (mm, t = 1 in this test)
0)]

For comparison, a stainless steel flat plate similar to that used in Example 2 and a corrugated plate made of the same material were coated with 70
% Ni-20Si-based ultrafine powder (particle size 0.2 to 1 mm)
Was laminated with a corrugated sheet coated on both sides and wound, and then a metal carrier having a honeycomb body obtained by diffusion bonding by heating in a vacuum furnace was manufactured. I went. The results of the comparison test of the metal carrier and the control in Example 1 and the comparison test of the metal carrier and the control in Examples 2 and 3 are shown in FIGS. 8 and 9, respectively.
Shown in According to this, the bonding strength of the metal carrier (Example 1) obtained according to the production method A of the present invention was improved about 1.5 times as compared with the conventional one, and the metal carrier obtained according to the production method B of the present invention (implemented It is clear that Examples 2 and 3) show a bond strength equal to or better than the conventional one.

The above-mentioned test example shows that the honeycomb body obtained according to the method of the present invention has a high bonding strength. This is as shown in FIG. This is mainly because the area A of the joint between the corrugated plate 2 and the corrugated sheet 3 is larger than the area A ′ of the joint in the conventional case (b). It is to be noted that FIG. 10 schematically shows, at the same reduction ratio, the bonded portion of the honeycomb body obtained by the manufacturing method A of the present invention and the conventional method using the metal foil having the same thickness and the same material. .

[0029]

As described in detail above, in the method for manufacturing a honeycomb body by diffusion bonding according to the present invention, in both the manufacturing method A and the manufacturing method B, the area of the bonded portion between the flat plate and the corrugated plate in the honeycomb body after the diffusion bonding is large. Is large and the strength of the bonded portion is extremely high, so that a honeycomb body having sufficiently improved durability can be obtained. Since the method of the present invention does not require high surface pressure to be applied to the above-mentioned joint during diffusion bonding, it does not require a special winding device or the like, and further, a thin foil having a thickness of 30 μm or less or a low thickness. The strength foil can be the material of the honeycomb body.

Further, in the production method A of the present invention, aluminum required for heat resistance is coated and diffused in the treatment step, so that as the material of the honeycomb body, a conventional aluminum compounded stainless steel which is inferior in workability and is very expensive is used. Thus, aluminum-free stainless steel can be used, and a honeycomb body can be manufactured with high workability and low cost. Further, in this manufacturing method A, even if a honeycomb body is manufactured from a heat-resistant metal having the same composition, the amount of aluminum can be appropriately adjusted in the aluminum coating step, so that the metal carrier having the same heat resistance as the required heat resistance can be adjusted. It can be manufactured using a metal. Moreover, in the production method A of the present invention, by supplying flux to the honeycomb body before aluminum coating, aluminum coating is possible even for a honeycomb body having a high cell density (fine mesh). The method can also be applied to a honeycomb body having a high cell density, which is often used for actual automobiles.

Further, in the production method B of the present invention, since diffusion bonding is promoted in a specific atmosphere, the atmosphere of a conventional heating furnace is simply changed to obtain a simpler operation.
A honeycomb body having sufficiently high bonding strength can be obtained. Further, in this manufacturing method B, since the diffusion bonding is completed at a lower temperature and in a shorter time than the conventional diffusion bonding, the heating furnace can be simplified and the heat treatment cost can be reduced. further,
By applying suction in the cooling step in the manufacturing method B of the present invention, the bonding strength can be further increased.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of a metal carrier in which a honeycomb body manufactured by the method of the present invention is inserted.

FIG. 2 is an explanatory view showing a state of the honeycomb body after the step 1 in Example 1 of the present invention.

FIG. 3 is an explanatory view showing the state of the honeycomb body after the step 2 in Example 1 of the present invention.

FIG. 4 is an explanatory view showing the state of the honeycomb body after the step 3 in Example 1 of the present invention.

FIG. 5 is an explanatory diagram showing a modification of the operation of step 2 in Example 1 of the present invention.

FIG. 6 is an explanatory view showing the state of the honeycomb body during the operation of Example 2 of the present invention.

FIG. 7 is an explanatory view showing the state of the honeycomb body after the operation of Example 2 of the present invention.

FIG. 8 is a graph showing the bonding strength of the honeycomb body obtained in Example 1 of the present invention and the conventional honeycomb body.

FIG. 9 is a graph showing the bonding strength of the honeycomb bodies obtained in Examples 2 and 3 of the present invention and the conventional honeycomb bodies.

FIG. 10 is an explanatory view showing the areas of the bonded portions of the honeycomb body (a) obtained according to the present invention and the conventional honeycomb body (b) in comparison.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Honeycomb body 2 Flat plate 3 Corrugated plate 4 Outer cylinder 5 Flux 6 Alloy layer 7 Aluminum layer 12 Liquid phase a Joint part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Tanaka 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (2)

[Claims] 1. A method for manufacturing a honeycomb body, which comprises stacking a heat-resistant metal flat plate and a corrugated plate, wherein the flat plate and the corrugated plate are coated with a flux to form a honeycomb body, or the honeycomb body is formed. After the formation of the above, a flux is applied, the molten aluminum is coated on the honeycomb body having the flux on its surface, and then the honeycomb body is heated in a non-oxidizing atmosphere to diffusion-bond the honeycomb body. A method for manufacturing a honeycomb body by bonding. 2. A honeycomb body formed by stacking a heat-resistant metal flat plate and a corrugated plate on top of each other is heated in an atmosphere made of a substance capable of combining with iron to form a low-melting-point substance, thereby diffusion-bonding the honeycomb body. A method for manufacturing a honeycomb body by diffusion bonding, which comprises: