JPH03296437A - Manufacture of substrate for metal catalyst support - Google Patents

Abstract

PURPOSE:To join a honeycomb body and to achieve cost reduction and high function of a catalyst converter by shrinkage fitting a honeycomb body made of a stainless steel foil coated with Al or an Al alloy with an outer cylinder and then heating it under certain conditions. CONSTITUTION:A honeycomb body 2 made of a stainless steel foil coated with Al or an Al alloy is shrinkage fitted with an outer cylinder 1. After that, the resulting body is heated at 800-1100 deg.C for 1 minute to 100 hours to bind the joint parts of the honeycomb body. Joining of the honeycomb body is carried out easily like this and high oxidation-resistance is provided to the honeycomb body and high adhesion strength between a gamma-Al2O3 coating layer and the honeycomb body is obtained. As a result, cost reduction and high function of a catalyst converter are achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a substrate for a metal catalyst carrier used in a catalytic converter for purifying exhaust gas. Specifically, the present invention relates to a method for producing a substrate for a catalyst carrier, which is used for bringing a gas or liquid into contact with a catalyst and causing a catalytic reaction between components in the fluid and the catalyst.

A specific example of the catalyst carrier is a catalyst controller used for purifying exhaust gas from automobiles and the like.

[Prior art and its problems]

Conventionally, catalytic converters have been made using porous γ-, which is a honeycomb-shaped ceramic base impregnated with a metal catalyst such as Pt-Rh.
Afl, 0. Coatings have been used. However, this ceramic honeycomb has drawbacks such as being susceptible to thermal shock and mechanical vibration and having high ventilation resistance. For this reason.

Recently, metal substrates have been used instead of ceramic honeycombs. Generally, the metal base is made by stacking flat or corrugated metal foil plates with a thickness of about 50 μm and winding them into a roll, or by laminating them to form a honeycomb body, which is then attached to the outer cylinder. Manufactured by.

Catalytic converters are exposed to high-temperature exhaust gas, are subjected to repeated heating and cooling, and undergo mechanical vibrations. A strong bond between the flat plate and the corrugated plate is required.

In recent years, a method of using high Al-containing stainless steel foil as a metal substrate has been disclosed from the viewpoint of oxidation resistance.

However, high Al-containing stainless steel has poor rolling properties and is expensive, and heat treatment is used to utilize the Al in the steel.
1203 film is formed, but this film tends to be insufficiently formed, and a good γ-AΩ20. Adhesion of the coating layer was difficult to obtain.

In order to overcome the problems of the above-mentioned conventional method using high Aj2-containing stainless steel foil, the surface of iron, stainless steel, heat-resistant alloy, etc. is coated with Aρ in advance, and heat treated in an oxidizing atmosphere. A technology to improve oxidation resistance and adhesion of γ-Al and 03 coating layers by forming a film and alloying was developed in the Japanese Patent Publication No. 57-341.
No. 8, Japanese Patent Publication No. 61-33621, etc. However, since catalytic converters are used in harsh environments as described above, the bonding strength of the Aρ-coated stainless steel foil honeycomb body is very important.

[Problem that the invention seeks to solve]

As a method for joining these Al-coated stainless steel foils, a technique disclosed in JP-A-63-54946 involves joining i-deposited ferritic stainless steel foils by brazing or welding, and then subjecting them to heat treatment to grow alumina whiskers. . Further, Japanese Patent Publication No. 57-55886 discloses a technique in which a honeycomb body made of metal foil and a metal outer cylinder are press-fitted and then joined by welding or brazing. Moreover, Japanese Patent Publication No. 57-55886 discloses a technique in which a honeycomb body made of metal foil and a metal outer cylinder are press-fitted and then joined by welding or brazing. However, even if Ni solder having a high melting point and oxidation resistance is used, the oxidation resistance of the brazed portion is inferior to that of AΩ-coated metal foil. In addition, when joining by welding, A
l There is a problem in that the oxidation resistance of the welded part decreases because the coating layer melts and scatters.

The base is made of a laminate material made by roll-bonding aluminum foil or aluminum brazing foil to iron-based alloy foil via a reducing agent. After being integrated by diffusion treatment in a vacuum or a reducing atmosphere, it is oxidized in an atmospheric atmosphere to form alumina on the surface. Japanese Patent Application Publication No. 6
2-227447 and Japanese Patent Laid-Open No. 63-44942 discloses a technique in which substrates made of Al-coated stainless steel foil are heat-treated and bonded in a vacuum or in a reducing atmosphere. However, these methods require heat treatment in a vacuum or a reducing atmosphere, and this treatment alone does not produce stable Al220. Since no film is formed, brazing is done later with γ-AI220. There is a problem in that an AR203 film forming treatment must be applied to improve the adhesion of the coating layer.

Therefore, in order to use Al-coated stainless steel foil in catalytic converters, a major challenge is to develop a joining technology that takes advantage of the advantages of I-coated stainless steel foil, which does not require heat treatment or welding in a vacuum or reducing atmosphere. It had become.

[Structure of the invention]

In the present invention, after press-fitting an outer cylinder to a honeycomb body made of stainless steel foil coated with Al or Al alloy,
Provided is a method for producing a substrate for a catalyst carrier, characterized in that bonding portions of a honeycomb body are bonded by heating at a temperature of 00 to 1100° C. for 1 minute to 100 hours.

In the present invention, ferritic stainless steel coated with Al or A2 alloy is preferably used.

As the ferritic stainless steel, one having good heat resistance is suitable. An example of this desirable ingredient is shown below.

C: 0.2 wt% or less, Mn: 2.0 Ilt% or less, Si: 5. (ht% or less, Cr: 10-30wt%, Al: O~6.Ow
t%,■, Rare earth elements total 20~0.2wt%.

Ti, Nb, V, Zr are total: 0~1.0w
t%, ribs, L Co total: O-2.0iit%.

The remainder is Fe and unavoidable impurities.

The rare earth elements include La, Ce, Sc, and the like. Further, Al diffuses into the steel from the coating layer during heat treatment, and if 6.0 wt % or less of Al is contained in the steel in advance, a honeycomb body with even better oxidation resistance can be obtained.

As described above, in the present invention, ordinary ferritic stainless steel can be used.

In addition to pure AΩ, AΩ-based coatings include Al, Si, and K.
An Al alloy containing a small amount of n, Mg, Fe-Cr, Ni, rare earth elements, etc. can be used, and the coating method may be any conventional method such as hot-dip plating, electroplating, vapor deposition plating, or cladding. In addition, the substrate used as a catalytic converter is usually formed from a foil-shaped steel plate with a thickness of about 50 μm, but the Al-based coating may be applied to a foil-shaped stainless steel plate that has been rolled to the above-mentioned thickness in advance.
A thin stainless steel plate having a thickness of 0.1 to 0.5 m+m may be coated with an AΩ type coating and then rolled into a foil having the above thickness.

The above Al-based coating layer is α-AI220. It is for forming whiskers. Therefore, the coating film thickness is
As disclosed in No. 15144, the wicker is uniformly formed on the foil surface during heat treatment with a thickness of 0.03 μm.
0.5 to 8 to facilitate heat treatment.
．． 0 μm is optimal.

The thus obtained Al1 or A2 alloy is formed into a honeycomb body made of stainless steel foil coated with it. The outer cylinder was press-fitted into the honeycomb body, and the contact portion between the flat steel foil and the corrugated steel foil constituting the honeycomb body was kept in close contact with each other for 80 minutes in the atmosphere.
When heat treated at a temperature of 0 to 1100°C, Aff in the coating layer on the surface of the honeycomb body diffuses into solid solution in the steel, improving oxidation resistance and at the same time forming chemically stable acicular Al oxides (Ag
2O, whiskers) are formed on the surface. The whiskers intertwine at the contact portion between the flat steel foil and the corrugated steel foil that constitute the honeycomb body, thereby fixing the flat sheet steel foil and the corrugated steel foil.

In order to generate this whisker, 800
It may be heated at ~1100°C for 1 minute to 100 hours.

If the heating temperature is less than 800°C, whiskers will not grow sufficiently, and if it exceeds 1100°C, no whiskers will form.

A block-shaped Al oxide grows. In order to sufficiently grow whiskers, heating time of 1 minute or more is required within the above temperature range.

Moreover, heating for less than 100 hours is preferable for the production of the catalyst carrier. Here, as the heating atmosphere, this method can be applied to an oxidizing atmosphere other than the air as long as chemically stable whiskers are generated on the surface.

Furthermore, although the manufacturing process becomes complicated, it is also possible to heat the honeycomb body in a crimped state under conditions that generate whiskers, join the honeycomb body, and then attach the honeycomb body to the outer tube.

Finally, γ-Al20. Coat the coating (washcoat layer). A known method can be used for the composition of the γ-Al203 coating layer and its coating method. - As an example, an aqueous solution in which γ-A[20 powder is suspended is mainly used, and a substrate is immersed in the solution, dried, and sintered to obtain γ-1t20. A coating layer is formed. Due to the °anchor effect of the whiskers mentioned above, the γ
-AI220. The adhesion of the coating layer is also improved.

The present invention uses a simple manufacturing process that combines press fitting of the outer cylinder and heat treatment in the atmosphere, instead of conventional methods such as heat treatment, brazing, or welding in a vacuum or reducing atmosphere. The honeycomb body can be bonded together, and at the same time, it can provide the honeycomb body with excellent oxidation resistance and good adhesion with the γ-Al203 coating layer. This contributes to lower cost and higher performance of the catalytic converter, and its industrial benefits are extremely large.

[Specific disclosure of the invention]

The present invention will be specifically described with reference to the drawings.

FIG. 1(a) is a sectional view of a base body according to the present invention, which is composed of a honeycomb body 2 and an outer cylinder 1 surrounding the honeycomb body 2. FIG. In this configuration, the inner surface 3 of the outer cylinder 1 is in contact with the entire outer surface 4 of the honeycomb body 2 with a press fit. This press fit is achieved by reducing the outer cylinder 1 from its initial diameter to a diameter d□.

FIG. 1(b) is a front view of the base body, showing that the outer cylinder 1 surrounding the honeycomb body 2 has a circular cross section.
C) is an enlarged view of the honeycomb body 2 on the front side of the base in FIG. A part of the honeycomb body 2 is shown in which close contact between the contact portions is ensured by fold press fitting.

FIG. 2(a) is a cross-sectional view of a base body in which the end portion of the outer cylinder 1 is left at its original diameter, and the center portion is reduced to a diameter d1 in a wavy manner and press-fitted. ) is a cross-sectional view of a base body in which the center part remains the same as the original diameter and the end parts are reduced to the diameter d1 and press-fitted.

FIG. 3 is a front view of a base body (b) which has an elliptical cross section after having (a) press-fitted the outer tube 1 into the hollow cylindrical honeycomb body 2. FIG.

11th! The shapes and formation methods of the honeycomb bodies shown in FIGS. 1(a) to 3(b) are known (for example,
55886), and the shape of the press-fitted outer cylinder may be of any shape as long as it presses the honeycomb body and brings the flat plate and corrugated plate into close contact, and various shapes are applicable.

Example I 1llll with a plate thickness of 50 μm as an Al-coated stainless steel foil
Material A-1, which is a ferritic stainless steel foil with a base material component of Cr-0,2Ti, coated with AΩ plating with a coating thickness of 5μ on both sides, and 18Cr with a plate thickness of 0.4in+.
Material A-2, which is made by hot-dip Al plating on a ferritic stainless steel plate base material with a base material composition of -0,2Ti, and then rolling it to a plate thickness of 50 μm and a coating film thickness of 7 μm. was used.

As an example of the present invention, materials A-1 and A-2 are used in Fig. 1 (c
) Honeycomb body with structure shown in (outer diameter 70φmm, length 8
0mm), made of heat-resistant steel with an inner diameter of 70φl and a length of 10mm.
After being attached to a 0 mm outer cylinder, it was press-fitted to form a cylindrical base as shown in FIG. 1, and the base was joined by heat treatment at 1000° C. for 1 hour in the atmosphere.

As comparative example 1, a honeycomb body was formed using the material of A-1 in the same manner as in the inventive example, and after mounting this on an outer cylinder,
i brazing filler metal (BNi-5) in vacuum (1 x 10-'
Torr) to 1180° C. for bonding. after that,
Al, O was heated in the air at 1000℃ for 1 hour.
1 film was produced. As Comparative Example 2, a honeycomb body was formed using the material of A-1 in the same manner as in the inventive example, and after joining the honeycomb body by spot welding, it was press-fitted to an outer cylinder in the same manner as in the inventive example. After that, at 1000℃ in the atmosphere,
Heat treatment was performed for 1 hour to form an 8Ω 20° film. As Comparative Example 3, a honeycomb body was formed using the material of A-2 in the same manner as in the inventive example, and this was attached to the outer cylinder.
In vacuum (l x 10-'
They were bonded by heat treatment at 1000° C. for 1 hour. As Comparative Example 4, a honeycomb body was formed using the material of A-2 in the same manner as in the present invention example, and while it was attached to the outer cylinder, heat treatment was performed at 1000°C for 1 hour in the atmosphere. I joined it.

Table 1 The substrate thus produced was subjected to γ-
Al20. The coating is applied, then immersed in an aqueous solution of chloroauric acid and rhodium trichloride, pulled up and dried at 250°C for 1 hour to give approximately 1 g of Pt,R per liter of support.
A catalyst for exhaust gas purification was obtained by supporting h. 20% of the catalyst
It was connected immediately after the manifold of a 00cc engine, and a 50-hour durability test was conducted at an exhaust gas temperature of approximately 1000°C to determine bonding strength (presence or absence of deformation of the honeycomb body), oxidation resistance, and adhesion of the γ-Al203 coating layer. compared gender.

Moreover, γ-Al20. The adhesion of the coating layer was evaluated by the peeling rate expressed by the following formula.

Table 2 summarizes these results. In addition, γ−AΩ
20. The evaluation criteria for adhesion of the coating layer are as follows.

○: Peeling rate less than 5% Δ: Peeling rate 5% to 15% On the other hand, Nf of Comparative Example 1 or 2
When joining by brazing or welding, abnormal oxidation is observed in the Ni brazed or welded parts, and γ-A
l20. The adhesion of the coating layer cannot be evaluated. In addition, in the case of Comparative Example 3, which was heated in vacuum without press fitting and joined by fusion burning of the AΩ coating layer, γ-Al20
．． There is a problem with the adhesion of the coating layer. When the outer cylinder of Comparative Example 4 was press-fitted and the honeycomb body was heat-treated in the atmosphere while attached to the outer cylinder, sufficient bonding strength was not obtained and the center part of the honeycomb body protruded. Also, γ-Al
The adhesion of the 203 coating cannot be evaluated.

Example 2 Al-coated stainless steel foil with a plate thickness of 50 μl
Coating film thickness 0.5 μm on both sides of ferritic stainless steel foil with base material component of 5Cr-3AI2-0.02La
Material A-3, which was electroplated with an Al-20% Mn alloy, was used.

Using the material A-3, press fit the outer cylinder as shown in Part 3 to form an elliptical columnar base (major axis 125 mm, minor axis 80 m).
m, length 100 mm). The substrate was heated in the atmosphere at 800°C for 30ml and 800°C for 30hr, respectively.
950℃×3hr, 1100℃×Latin and 1
Examples of the present invention are those bonded by heat treatment at 100°C x Ihr, and each was heated at 700°C x 30hr for 1200'' in the atmosphere.
Comparative Example 5 and Comparative Example 6 were those subjected to CXIhr heat treatment.
shall be. The whisker morphology after these heat treatments was evaluated based on the following criteria.

○: Nice force generation △: Non-uniformity of Nice ker formation - (presence or absence of deformation of the honeycomb body), oxidation resistance,
γ-Al20. The adhesion of the coating layers was compared. Table 3 summarizes these results.

As is clear from the wood surface, all of the examples of the present invention show good results, whereas in Comparative Example 5, whisker formation is uneven, so γ-AI220. The adhesion of the coating layer is somewhat poor. In Comparative Example 6, block-shaped Al oxides were produced instead of whiskers, so that sufficient bonding strength of the honeycomb body could not be obtained even by press fitting, and the honeycomb body was deformed and the center part of the honeycomb body was blown out. And γ-Al20.
The adhesion of the coating layer could not be evaluated.

Therefore, the press-fitted substrate has a temperature of 800 to 110
By heating at 0° C. for 1 minute or more, the bonded portions of the honeycomb body can be bonded.

〔Effect of the invention〕

The present invention makes it possible to join honeycomb bodies using a simple manufacturing process that combines press fitting of the outer cylinder and heat treatment in the atmosphere, and at the same time provides the honeycomb bodies with excellent oxidation resistance and γ-120. Good adhesion with the coating layer can be provided. This contributes to lower cost and higher performance of the catalytic converter, and its industrial benefits are extremely large.

[Brief explanation of drawings]

FIG. 1(a) is a side view with half of the base body fully press-fitted. FIG. 1(b) is a front view of the cylindrical base. 1st
Figure (C) is an enlarged view of the honeycomb body portion on the front of the base. FIGS. 2(a) and 2(b) are side views with half of the partially press-fitted base body cut away. FIG. 3(a) is a front view of the press-fitted basics. FIG. 3(b) is a front view of a press-fitted base body which has been deformed from the state shown in FIG. 3(a) and has an oval cross section. 1: outer cylinder, 2: honeycomb body, 3: inner surface of outer cylinder, 4: outer surface of honeycomb body, 5: flat steel foil, 6: corrugated steel foil. Figure (0) Figure (a) Figure (b)

Claims (1)

[Claims] After press-fitting the outer cylinder to a honeycomb body made of stainless steel foil coated with Al or Al alloy,
A method for producing a substrate for a catalyst carrier, characterized in that bonding portions of a honeycomb body are bonded by heating at a temperature of 100° C. for 1 minute to 100 hours.