JP3238565B2 - Metal honeycomb for catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal honeycomb used for a catalyst device for purifying exhaust gas of an internal combustion engine and a catalyst device for a chemical plant.

[0002]

2. Description of the Related Art In recent years, metal honeycombs have been increasingly used as catalyst devices for purifying exhaust gas from internal combustion engines, especially gasoline engines for automobiles. This is because the metal honeycomb has a larger porosity than conventionally used ceramic honeycombs, and has advantages such as excellent durability even in an environment where the temperature rises and falls sharply. This metal honeycomb is formed by superimposing a flat foil having a thickness of about 50 μm, which is a stainless steel foil having excellent heat resistance, and a corrugated flat foil, and joining them together.

As a stainless steel foil, Japanese Patent Publication No. 58-23
138, JP-B-54-15035, JP-A-56-96726, etc.
An Fe-Cr-Al-based alloy foil having excellent oxidation resistance is used. These foils form an aluminum oxide film on the surface at high temperatures and retain extremely good oxidation resistance. Examples of the joining method include brazing as described in JP-A-61-199574, resistance welding as described in JP-A-64-40180, and description of JP-A-54-13462. Various types of laser beam welding and electron beam welding are used.

[0004]

SUMMARY OF THE INVENTION Fe-Cr-Al alloy foil used as a honeycomb material, for example, 20Cr-5
Although Al steel foil has excellent oxidation resistance, its productivity is extremely poor and its production cost is high. Further, the actual use environment is often used at a maximum of about 800 ° C., and the oxidation resistance of this material is often excessive. In addition, the brazing material used in brazing is expensive in the brazing method, and the process for performing the brazing is extremely complicated, such as application of a binder → adhesion of the brazing material → vacuum heat treatment. Resistance welding is a production method with low productivity and is not suitable for mass production. Further, laser beam welding has a disadvantage that a welding apparatus becomes extremely expensive.

A relatively inexpensive joining method is disclosed in US Pat.
There are also diffusion bonding methods described in the description of Japanese Patent No. 300956 and Japanese Patent Application Laid-Open No. 1-270947. However, in order to secure the oxidation resistance required for a catalyst base in a foil material, the material used is as described above. in the Fe-Cr-Al alloy, a slight oxygen source in the furnace (CO, H ₂ O) in the reaction to the foil surface coating of very thin aluminum oxide occurs in a vacuum heat treatment for performing diffusion bonding However, even if the film is heated to a high temperature of 1200 ° C. or more, these films may hinder diffusion bonding, and the bonding must be local and unstable. In addition, SU described in Japanese Patent Application Laid-Open No. 1-270947
Normal stainless steels such as S410L, 430, and 434 have insufficient oxidation resistance and high-temperature strength as a foil material and lack heat resistance as a base material of a catalyst for automobile exhaust gas. Furthermore, sulfuric acid dew-point corrosion may occur on honeycombs due to the high concentration of S in fuels for diesel catalysts. Not enough.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned current problems, and it is an object of the present invention to provide an inexpensive metal honeycomb for a catalyst by a relatively simple joining method using a Cr-Mo stainless steel foil. With the goal.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and its gist is as follows. (1) containing 0.3 to 3% by weight of Mo and Al
A 0.8% impurity level content, acid at high temperature
Catalyst metal honeycomb, characterized in that of comprising an aluminum film and made ferritic stainless steel foil of flat and corrugated sheets to produce a chromium oxide film on the surface without and diffusion bonding joining or liquid phase with each other. ( 2 ) The chemical composition of the stainless steel foil is by weight: C: 0.2% or less, Si: 1% or less, Cr: 11 to 25%, Mo: 0.3 to 3%, Al: impurity level to 0 The catalyst metal honeycomb according to the above (1), wherein 0.8% and the balance are Fe and unavoidable impurities. ( 3 ) The chemical composition of the stainless steel foil is, by weight ratio, C: 0.2% or less, Si: 1% or less, Cr: 11 to 25%, Mo: 0.3 to 3%, Al: impurity level to 0.1%. The metal honeycomb for a catalyst according to the above item (1), comprising a total of 0.01% to 0.2% of one or more rare earth elements containing 8% and Y, and the balance being Fe and unavoidable impurities. ( 4 ) The chemical composition of the stainless steel foil is by weight: C: 0.2% or less, Si: 1% or less, Cr: 11 to 25%, Mo: 0.3 to 3%, Al: impurity level to 0 0.8%, Ti: 0.05 to 0.5%, Zr: 0.05 to 0.5%, V: 0.03 to 0.5%, W: 0.5 to 3% 2. The metal honeycomb for a catalyst according to the above item (1), comprising one or more kinds, and the balance being Fe and unavoidable impurities. ( 5 ) The chemical composition of the stainless steel foil is, as a weight ratio, C: 0.2% or less, Si: 1% or less, Cr: 11 to 25%, Mo: 0.3 to 3%, Al: impurity level to 0.1%. 8%, one or more of the rare earth elements containing Y are added in a total amount of 0.1%.
01-0.2%, Ti: 0.05-0.5%, Zr: 0.05-0.5%, V: 0.03-0.5%, W: 0.5-3% 2. The metal honeycomb for a catalyst according to claim 1, comprising at least one of the following, and the balance being Fe and inevitable impurities. 3.

The present inventors have previously disclosed in Japanese Patent Application No. Hei 5-24517 a method of diffusing while maintaining the oxidation resistance required for a foil material.
It has been proposed to limit Al to a low level and to add more than 1% to 3.5% of Si in order to improve the liquid phase bonding property.
According to subsequent studies, Mo was reduced to 0.1 even when Si was set to 1% or less.
The present invention has been made based on the finding that the addition of 3 to 3% can improve the diffusion-liquid phase bonding property while maintaining the required oxidation resistance. Further, the present inventors have found that Mo addition is effective for sulfuric acid dew-point corrosion which may be a problem in diesel catalysts, and reached the present invention. That is, the present invention provides a metal honeycomb foil material,
By using a stainless steel foil containing 0.3 to 3% Mo, diffusion or liquid phase bonding is facilitated, and at the same time, necessary oxidation resistance is ensured. Al content is 0.8% to ensure sulfuric acid corrosiveness and to prevent the formation of an alumina film which is a hindrance when using relatively simple diffusion or liquid phase bonding in the process.
By suppressing the content below, diffusion or liquid phase bonding can be smoothly performed at a lower temperature. Thus, the present invention uses a Cr-Mo-based stainless steel foil, which is much more manufacturable than a Fe-Cr-Al alloy-based stainless steel foil, and performs relatively simple diffusion or liquid phase bonding at lower temperatures at lower temperatures. It is possible to provide a low-cost metal honeycomb that can be closed.

Next, the reason why the components of the stainless steel foil of the honeycomb are limited in the present invention will be described. Mo is Al or Si
In a ferritic stainless steel that does not contain
The oxidation resistance is reinforced and the high-temperature strength is increased to improve the thermal fatigue resistance of the honeycomb. At the same time, even for a steel material containing aluminum at a low level, the formation of an aluminum oxide film is inhibited and diffusion bonding is facilitated. However, if it is less than 0.3%, the effect of the addition is insufficient, and if it exceeds 3%, the material is deteriorated. In addition, sulfuric acid dew point corrosion may occur on honeycombs for diesel catalysts,
In this case, if Mo is added in an amount of 0.5% or more, the dew-point corrosion resistance is improved. Si is an element inevitably contained and if added at a high level, improves the oxidation resistance of the steel material and has the effect of inhibiting the formation of an aluminum oxide film, thereby facilitating diffusion bonding. Since it plays this role, the range of Si is set to 1% or less. However, Cr is 18%
In the following cases, the Si content is desirably 0.6% or more to reinforce the oxidation resistance of the foil.

When Al is added as much as 1% to Cr-based stainless steel, a protective film of aluminum oxide is formed at a high temperature to improve the oxidation resistance. However, in the present invention, diffusion or liquid phase bonding is hindered. Exclude. However, in order to shift the transformation point of the foil material to a higher temperature side than the operating temperature, an aluminum oxide film must be formed within a range in which an aluminum oxide film is not formed, ie, 0.8% or less.
Can be added.

C lowers the melting point of the foil material to facilitate diffusion or liquid phase bonding. However, excessive addition of C deteriorates the material, so the upper limit was made 0.2%. Cr is a basic element for maintaining the oxidation resistance of stainless steel. If it is less than 11%, the oxidation resistance is insufficient, and if it exceeds 25%, the material is hardened and the productivity is deteriorated.

Since rare earth elements containing Y improve the oxidation resistance of the foil material, they are added as necessary in the present invention.
However, if the total amount of one or more of them is less than 0.01%, there is no effect, and if it exceeds 0.2%, a flaw is caused in the material, so that the content is set to 0.01 to 0.2%. Ti, Zr, V, and W each improve the high-temperature strength of the foil material, and are added as necessary. If the amount is less than the respective lower limits, the effect of addition is insufficient. If the amount exceeds the upper limit, the material becomes hard and the productivity is deteriorated. Also, N
b can be added in an amount of 0.1 to 0.6% for improving the high temperature strength.

[0013] Table 1 shows examples of foil material compositions that can be used in the honeycomb of the present invention. Among the chemical compositions of the foil material used in the present invention, Mn, P, and S are not particularly specified,
There is no problem if these are levels contained in ordinary stainless steel.

The diffusion bonding in the present invention is a bonding in which the top surface of the corrugated foil and the contact surface of the flat foil are mutually diffused while maintaining a solid phase. The liquid-phase joining in the present invention means joining both surfaces into a liquid phase by a melting point depressant such as graphite powder applied to the contact surface.

[0015]

[Table 1]

[0016]

EXAMPLES [Example 1] Foil having a chemical composition of A, G, N, and R shown in Table 1 and having a thickness of 50 μm was prepared, and a part of the foil was corrugated to obtain a corrugated foil. By stacking and winding, a honeycomb having an outer diameter of 97 mmφ and a length of 100 mm was produced. Further, as the outer cylinder, a thickness of 19% Cr steel 1.5
A cylinder having an outer diameter of 100 mmφ and a length of 100 mm was made of a stainless steel plate of mm, and the above-mentioned honeycomb was inserted into the cylinder. This was subjected to a heat treatment at 1200 ° C. for 30 minutes in a vacuum, and the outer cylinder and the outermost periphery of the honeycomb, and the corrugated plate and the flat plate in the honeycomb were mutually diffusion bonded. At this time, if the corrugated foil and the flat foil are joined over the entire area in the honeycomb, thermal fatigue destruction is likely to occur during use in the engine. Therefore, as schematically shown in the cross-sectional view of FIG. The portion 3 shown was coated with a diffusion stop material containing titania as a main component when wound around a honeycomb, so that diffusion bonding did not occur in this portion. 1 is an outer cylinder containing a honeycomb body,
Reference numeral 2 denotes a region where the honeycomb bodies are joined. 2 as a comparative example
Using a 50 μm thick foil of 0Cr-5Al steel , a honeycomb was inserted into the outer cylinder in the same manner as described above, and vacuum heat treatment was performed.

[0017] These two types of metal substrates were evacuated to a displacement capacity of 2000.
Installed in the middle of the exhaust pipe of a cc, 4-cylinder engine and operated at 5000 mpm at full load, 800 ° C x 10
A cooling test was performed 900 times with minute heating and engine stop for 20 minutes. As a result, in the case of using the foils of A, G, N, and R in Table 1, no particular abnormality was observed even after 900 times of the thermal test, while in the case of the comparative example using the 20Cr-5Al foil, During the cold and hot inspection 600 times, 3
About two-thirds had a shift on the outlet side of the exhaust gas. As a result of the investigation, in the former honeycomb, the vertex of the corrugated foil and the flat foil were surely diffusion-bonded, and the bonding had a planar spread,
In the latter case, the bonding was performed only sparsely, and only the point-like bonding was performed in the bonding part. In other words, it is shown that aluminum foil was formed on the 20Cr-5Al foil during the vacuum heat treatment, and diffusion bonding was not sufficiently performed.

Example 2 A 50 μm thick foil having the chemical composition of A, G, M and S shown in Table 1 was prepared, and a metal substrate was prepared in the same manner as in Example 1. In this case, however, graphite powder was applied as paste to the top of the corrugated foil to be joined, and the vacuum heat treatment was performed at 1150 ° C. At the same time, the heat treatment of the research honeycomb was examined. When the graphite powder was applied, the foil surface melted and liquid phase bonding was performed. As a comparative example, a 50 μm-thick foil of SUS430 (16% Cr steel) was prepared, and a metal substrate was prepared in the same manner as described above.

These two types of metal substrates were subjected to a cooling test using an engine bench in the same manner as in Example-1. As a result, no particular abnormality was found in the former metal substrate even after 900 times of cold heat, but in the latter case, the foil of the honeycomb surface on the exhaust gas entrance side was partially blackened during the 600 times of cold heat inspection. The test was discontinued because part of it was missing. As a result of the investigation, it was found that diffusion bonding was sufficiently performed in the latter metal-substrate honeycomb, but the inside of the honeycomb was considerably oxidized and a cavity was formed in part. That is, SUS4 of the comparative example
This indicates that the foil 30 has insufficient oxidation resistance.

Example 3 A foil having a chemical composition of A, B, G, and M shown in Table 1 having a thickness of 50 μm was prepared, and a metal substrate was prepared in the same manner as in Example 1. SUS430 as a comparative example
A 50 μm thick foil of (16% Cr steel) was prepared, and a metal substrate was prepared in the same manner as described above. From these metal substrates, 1
A test sample was carefully cut out into a strip of 0 mm × 10 mm × 50 mm, and a sulfuric acid corrosion test simulating a corrosion environment generated in the case of a catalyst carrier for a diesel engine was performed. The test was performed 50 cycles of a cycle test in which the pre-oxidation treatment was performed at 700 ° C. × 1 hr in the atmosphere, and then a dipping in a low PH solution mainly containing sulfuric acid at 150 ° C. and drying were performed for 4 hrs. As a result, in the metal substrate of the present invention, no particular abnormality was observed even after 50 cycles, but in the case of the comparative example, the corrosion deterioration was severe and holes were penetrated through the foil material. That is, it is shown that the SUS430 foil of the comparative example has insufficient sulfuric acid corrosion resistance.

As shown in the above embodiments, the present invention provides a low-cost catalyst honeycomb using a relatively inexpensive foil material and a simple joining method, and greatly contributes to pollution control technology. It is.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an example of a bonding structure of a metal base for implementing the present invention.

[Explanation of symbols]

 1 outer cylinder 2 area where honeycomb is joined 3 area where honeycomb is not joined

Continuation of the front page (72) Inventor Hitoshi Ota 5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Corporation Nagoya Works (56) References JP-A-5-208140 (JP, A) JP-A-1 -270947 (JP, A) JP-A-4-156945 (JP, A) JP-A-7-213918 (JP, A) Patent 2598242 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB) Name) B01J 21/00-37/36 B01D 53/86 C22C 38/00

Claims (5)

(57) [Claims] (1) containing 0.3 to 3% of Mo by weight ,
And the content of Al is the impurity level ~ 0.8%,
Catalyst metal honeycomb, characterized in that formed by mutually bonding diffusion bonding or liquid-phase a flat plate and the corrugated plate of ferritic stainless steel foil to produce an oxidized chromium film on the surface without creating an aluminum oxide film at high temperatures. 2. The chemical composition of the stainless steel foil is as follows: C: 0.2% or less by weight, Si: 1% or less, Cr: 11 to 25%, Mo: 0.3 to 3%, Al: impurity level 2. The metal honeycomb for a catalyst according to claim 1, wherein the content of Fe is 0.8%, and the balance is Fe and unavoidable impurities. 3. The chemical composition of the stainless steel foil is as follows: C: 0.2% or less by weight, Si: 1% or less, Cr: 11 to 25%, Mo: 0.3 to 3%, Al: impurity level 2. The composition according to claim 1, wherein one or more rare earth elements containing Y are contained in a total of 0.01 to 0.2%, and the balance is made of Fe and unavoidable impurities. Metal honeycomb for catalyst. 4. The chemical composition of the stainless steel foil is as follows: C: 0.2% or less by weight, Si: 1% or less, Cr: 11 to 25%, Mo: 0.3 to 3%, Al: impurity level 0.8%, further Ti: 0.05 to 0.5%, Zr: 0.05 to 0.5%, V: 0.03 to 0.5%, W: 0.5 to 3% 2. The metal honeycomb for a catalyst according to claim 1, comprising at least one of the following, and the balance being Fe and unavoidable impurities. 3. 5. The chemical composition of the stainless steel foil is as follows: C: 0.2% or less by weight, Si: 1% or less, Cr: 11 to 25%, Mo: 0.3 to 3%, Al: impurity level 0.8%, one or more of the rare earth elements containing Y are added in a total amount of 0.1%.
01-0.2%, Ti: 0.05-0.5%, Zr: 0.05-0.5%, V: 0.03-0.5%, W: 0.5-3% The metal honeycomb for a catalyst according to claim 1, comprising at least one of the following, and the balance being Fe and unavoidable impurities.