JPH08197B2 - Substrate for catalyst converter - Google Patents

Description

TECHNICAL FIELD The present invention is mainly installed in an exhaust gas path of an automobile or the like,
The present invention relates to a catalytic converter substrate used for decomposing and purifying various oxides in exhaust gas.

[Prior Art and Problems] Currently, a monolithic catalytic converter is used in an exhaust gas path of an automobile for the purpose of purifying exhaust gas. Since the converter is generally exposed to a corrosive gas at a high temperature ranging from 800 ° C to about 1200 ° C, it is required to have oxidation resistance at a high temperature. Conventionally, a honeycomb-shaped ceramic is used for a frame that holds a catalyst carrier. Has been. However, the ceramic frame has the following problems.

a. Since the thermal conductivity is low, it is difficult to raise the temperature and exhaust gas purification at the start of operation cannot be expected.

b. Sensitive to thermal shock and mechanical vibration.

c. Since the difference in thermal expansion from metal is large, it is difficult to fix it to the converter shell.

In order to eliminate the drawbacks of the above ceramic converter,
Recently, the use of a heat-resistant stainless steel foil (foil) having a plate thickness of about 50 μm as a frame material of a catalyst carrier has been studied, and it has already been put to practical use in Europe and America. Since stainless steel is excellent in oxidation resistance at high temperatures, corrugating stainless steel foil to form a honeycomb-shaped frame,
The frame is coated with γ-Al ₂ O ₃ to be a catalyst support, dried and sintered, and then coated with a catalyst,
Manufactures metallic frame converters. However, the above-mentioned stainless steel frame does not always have sufficient adhesion to alumina that serves as a catalyst carrier, and therefore various improvements have been attempted. As an example, Al is 3-8%
Using Al-containing stainless steel containing, corrugated after annealing the foil of the stainless steel, after forming, further heat treatment by using Al in the steel α-Al ₂ O on the stainless steel surface
₃ whisker to produce a method of coating a gamma-Al ₂ O ₃ on the needle-like crystals has been known (JP 56-9672
6). In addition, in order to promote the formation of α-Al ₂ O ₃ whiskers, the above-mentioned Al-containing stainless steel is preheated in a CO ₂ atmosphere or the like (JP-A-57-71898), or the components of the stainless steel are Zr and Y. And the like to improve mechanical strength and high temperature creep characteristics (Japanese Patent Laid-Open Nos. 56-121641 and 58-17743).
7) etc. are known.

However, the above-mentioned conventional methods of forming the frame of the catalytic converter using stainless steel, all use high Al content stainless steel, the heat treatment of the stainless steel
Since Al is used to generate α-Al ₂ O ₃ on the steel surface, the manufacturing process is complicated. Further, since the Al content is about 3 to 8%, the rolling property is poor, and it is difficult to manufacture a foil with a plate thickness of about 50 μm. Further, since Al in the steel is used, there is a problem that the formation of α-Al ₂ O ₃ tends to be insufficient.

In order to avoid the problems of the above-mentioned conventional method using stainless steel, a method of manufacturing the metallic frame using titanium-containing low carbon steel is also known. An example is 0.01
This is a method of forming a foil by using a low carbon steel containing Ti of 1.0% to 1.0%, applying hot-dip Al plating on the surface of the carbon steel, and then cold rolling to form a foil (Japanese Patent Laid-Open No. 61-568, JP-A-60-568). −50176
Five). This method uses economically advantageous low-carbon steel instead of expensive stainless steel, adds Ti to the steel in order to improve rolling property and high temperature oxidation resistance, and further coats the surface of the steel with molten Al plating. However, the whisker is generated by heat treatment, as compared with the method using the Al-containing stainless steel, the manufacturing process is simple and economically advantageous, but the mother of those to which Ti is added Since the material is low carbon steel, the heat resistance of the product is still inferior, and its reliability is poor when used at high temperatures of 800 ° C or higher. Moreover, since a hard and brittle alloy layer (Fe-Al, Fe-Al-Si) is formed in the hot-dip plated layer, there is a serious problem that the plated layer is easily peeled off during rolling after plating.

[Knowledge for Solving Problems] The present inventor has attempted to improve a metal frame using stainless steel, since stainless steel has markedly superior oxidation resistance at high temperatures as compared with Ti-containing low carbon steel. Unlike conventional methods that utilize the contained Al in the steel as the source, by subjecting the stainless steel surface to Al plating by vapor deposition plating or electroplating, and forming the above whiskers by heat treatment of the Al plating layer, at high temperatures, It has been found that it is possible to produce a metallic frame having excellent oxidation resistance and excellent workability that does not cause peeling of the plating layer during rolling and molding.

Further, in the method of forming a plating layer on stainless steel, the plating method is important, and when Al plating is performed by hot dipping, non-plating is likely to occur, and it is difficult to obtain a thin and uniform plating layer. . On the other hand, it has been found that if Al plating is applied by vapor deposition plating or electroplating, a uniform plating layer having excellent adhesion to the base material can be obtained and a good alumina whisker can be formed.

According to the present invention, a stainless steel foil is used as a frame, and at least one surface of the frame is coated with alumina for supporting a catalyst, which is a catalytic converter substrate, wherein the stainless steel is Cr: 3-25% by weight (% below),
C: 0.08% or less, Ti: 0.05 to 0.5%, Al: less than 1%, Mn: 0.8%
Hereinafter, Si: 0.8% or less, the balance is a Ti-containing stainless steel consisting of iron and unavoidable impurities, the stainless steel surface is subjected to Al plating by vapor deposition plating or electroplating,
In the case of the vapor deposition plating, heat treatment is performed simultaneously with or after plating, and in the case of the electroplating, heat treatment is performed after plating to generate α-Al ₂ O ₃ whiskers in the Al plating layer and then γ-Al. _A substrate for a catalytic converter is provided, which is coated with ₂ O ₃ to form the alumina carrier.

An example of the manufacturing process of the metallic frame according to the present invention is shown in FIG.

Ti-containing stainless steel is used for the metallic frame of the present invention. The Ti-containing stainless steel means Cr: 3 to 25
%, C: 0.08% or less, Al: less than 1%, Ti: 0.05 to 0.5%, Mn and Si are contents in the range contained in ordinary stainless steel, and the balance is It is composed of iron and inevitable impurities.

In the case of stainless steel that does not contain Ti, Al diffused into the steel from the Al plating layer combines with carbon and nitrogen in the steel to form voids near the interface between the plating layer and the base metal, which causes the peeling of the plating layer. Cause. Therefore, Ti is required in an amount sufficient to combine with all the carbon and nitrogen in the steel. Furthermore, in the present invention, Al of the Al plating layer is smoothly diffused in the steel, and it serves to clean the steel structure and improve the rolling property, and from this viewpoint, the Ti amount is 0.05 to 0.
5% is preferable.

If the Ti content is less than 0.05%, not all carbon and nitrogen in the steel will be sufficiently bonded to Ti. Moreover, even if the Ti content is 0.5% or more, the free Ti content in the steel only increases,
The above effect is not further improved.

The Cr content needs to be 3 to 25%, preferably 11 to
20%. When the Cr content is less than 3%, the high temperature oxidation resistance of the base material is poor. Stainless steel generally contains 11% or more of Cr, but in the present invention, if 3% or more of Cr is contained, a complex oxide of Fe, Cr, and Al is formed, and a minimum source is required. Since high temperature oxidation resistance can be obtained, those containing 3% or more of Cr are included in the range of stainless steel. Even if the Cr content exceeds 25%, the effect of significantly improving the oxidation resistance of the base metal is not recognized, and considering that Cr is an expensive metal, the Cr content is 25% or less economically. Preferably there is.

Unlike the conventional method, the present invention does not use Al in steel to generate α-Al ₂ O ₃ whiskers in the method using stainless steel, so that it is not necessary to use high Al-containing stainless steel. In the present invention, stainless steel containing no Al or having an Al content of less than 1% is used. As a result, it is easy to manufacture a cold rolled foil having a plate thickness of about 50 μm. If the amount of Al exceeds 1%, the base material becomes hard as the amount of Al increases and rolling becomes difficult, which is not preferable.

The content of Mn and Si is within the range contained in ordinary stainless steel, and is generally Mn: 0.8% or less and Si: 0.8% or less.

The contents of Mn, Si and Ni are not essential in the present invention.

In addition, the stainless steel contains P, S, and the like as unavoidable impurities, but there is no problem if they are below the usual mixing amount. Considering the mechanical properties of the base material, the smaller the amount of these elements, the more preferable.

Both or one surface of the above stainless steel is plated with Al by vapor deposition or electroplating. During the plating treatment, the stainless steel may be rolled in advance to a foil having a plate thickness of about 50 μm, or a plate thickness of 0.1 to
A steel plate having a thickness of about 0.3 mm may be plated and then rolled to the thickness of the foil.

The plating layer is for forming the α-Al ₂ O ₃ whiskers, and therefore the thickness of the plating layer may be such that the uniform whiskers are formed on the steel surface. Specifically, when foil-shaped stainless steel is used, the film thickness of the plating layer is optimally 0.5 to 8.0 μm, and even when a steel plate having a plate thickness of 0.1 to 0.3 mm is used, the foil after rolling is used. It is preferable that the plating layer has a thickness of 0.5 to 8.0 μm. If the thickness of the plating layer is less than 0.5 μm, insufficient formation of the above whiskers occurs. If the thickness of the plating layer is more than 8.0 μm, heating for a long time is required to generate the above whiskers. Treatment or treatment at higher temperature is required. Therefore, the film pressure of the plating layer is 0.5 to 8.0.
μm is preferred.

The Al plating layer is formed by vapor deposition plating or electroplating. In the case of hot dip plating, it is unavoidable that a brittle alloy layer is formed near the plating layer interface as described above. The alloy layer is likely to cause the peeling of the plating layer, and also makes the α-Al ₂ O ₃ whiskers formation uneven.

The principle of vapor plating is to deposit the vapor of the plating metal on the surface of the steel strip in the vacuum vapor deposition chamber and condense it to form a plating layer, without the inconvenient alloy layer found in hot dip plating. It is possible to obtain a plating layer having excellent adhesion. Further, vapor deposition plating can form a good plating layer even on an extremely thin steel strip having a plate thickness of about 50 μm. On the other hand, in hot dip galvanizing, a steel strip is passed through a plating bath heated to a temperature higher than its melting point, so that an extremely thin steel strip is apt to cause remarkable thermal strain and is usually limited to a steel strip having a plate thickness of 0.25 mm or more. Further, when the stainless steel sheet is subjected to Al plating by Al hot dip coating, the wettability between the molten Al and the stainless steel sheet is poor and dot-like non-plating is likely to occur. In the case of vapor deposition plating,
Al plating with good adhesion can also be applied to stainless steel sheets. Further, the vapor deposition plating can be thin plating, and the α-Al ₂ O ₃ coating can be immediately formed on the Al plating layer in the vapor deposition step by utilizing the heat during vapor deposition.

Instead of the vapor deposition plating, Al plating may be formed by electroplating. As with the case of vapor deposition plating, the plating layer formed by electroplating does not form an alloy layer as seen in hot dipping, and a good plating layer can be obtained.

The Al-plated stainless steel foil by vapor deposition plating or electroplating is processed into a honeycomb-shaped structure by corrugation, and is subsequently processed into a converter frame through a canning process.

After the above processing, heat treatment in the atmosphere forms α-Al ₂ O ₃ whiskers on the Al plating layer (see FIG. 2 (a)). The heat treatment may be heating in the air, and specific heat treatment conditions are slightly different depending on the type of stainless steel and the film thickness of the plating layer, but usually 800 to 1100 ° C., 5 minutes to 5 minutes.
0 hours is all right.

When the above Al plating is applied to a stainless steel plate having a plate thickness of 0.1 to 0.3 mm, the steel plate is rolled to a plate thickness of 25 to 90 μm and a plating layer thickness of 0.5 to 8.0 μm, and then the corrugation and heat treatment are performed. Give.

In the conventional method of forming the above whiskers without forming a plating layer using high Al content stainless steel, it is not possible to form satisfactory whiskers by heating in the atmosphere. Therefore, heating is performed in an inert gas atmosphere with an oxygen partial pressure of 0.75 Torr or less, or in a carbon dioxide gas atmosphere.

In the present invention, it is not necessary to adjust the atmosphere, which is indispensable in the above-mentioned conventional method, and heating in the air is sufficient, whereby a good whisker can be formed.

The heating temperature and time for the α-Al ₂ O ₃ whiskers to form are A
l It depends on the film thickness of the plating layer. As mentioned above, if the film thickness of the plating layer is 0.5 to 8.0 μm, 800 to 1100 ° C, 5 minutes to 50
The whiskers are generated in time. It should be noted that a thinner plating layer tends to form fine and needle-like whiskers in a short time, but even if the thickness is thick, if the heating temperature is high within the above range, needle-like whiskers can be formed. Whiskers can be formed in a short time.

Chemically stable α-Al ₂ O on the steel surface by the above heat treatment
_{While 3} is formed, Al in the plating layer diffuses into the steel and forms a solid solution, which improves the heat resistance of the stainless steel foil.

After the heat treatment (whisker treatment), γ-Al ₂ O _{3 serving as} a catalyst carrier is coated on the whiskers (see FIG. 2 (b)). The coating of γ-Al ₂ O ₃ may be carried out by a usual method. For example, the coating alumina sol is applied onto the foil, and after drying,
It is formed by heating to 500 to 800 ° C. in the air and firing. The film thickness of γ-Al ₂ O ₃ is usually 1 to 10 μm.
The adhesion of the γ-Al ₂ O ₃ layer depends on the form of the α-Al ₂ O ₃ whiskers, and the finer and acicular whiskers, the better the adhesion. A metal catalyst such as platinum or rhodium is further coated on the γ-Al ₂ O ₃ layer (FIG. 2 (c)) to finally form a catalytic converter substrate.

In Fig. 2, 10 is stainless steel foil, 11 is α-
Al ₂ O ₃ whiskers, 12 is γ-Al ₂ O ₃ , and 13 is a metal catalyst.

EFFECTS OF THE INVENTION The catalytic converter substrate of the present invention has the following advantages.

a. It is easy to manufacture the foil because normal Ti-containing stainless steel is used as the base material. Since the conventional method using stainless steel is limited to high Al content stainless steel, it is difficult to roll the foil to a thickness of about 50 μm.
Also, those using low carbon steel have poor oxidation resistance at high temperatures.
It cannot withstand long-term use in the temperature range of 800 ° C or higher.

b. Since Al plating is formed by vapor deposition plating or electroplating, a fragile alloy layer does not occur near the plating interface that occurs in hot dip plating, and the plating layer does not peel off even by rolling after plating, Good rolling workability.
Therefore, as a result of forming the above whiskers uniformly on the steel surface, the adhesion of the γ-Al ₂ O ₃ coding layer is excellent.

c. α that is chemically stable to the Al plating layer when heated in the atmosphere
In the conventional method using high Al content stainless steel, in which Al ₂ O ₃ whiskers are easily formed, satisfactory whiskers cannot be formed by heating in the atmosphere. Therefore, heating is performed in an inert gas atmosphere with an oxygen partial pressure of 0.75 Torr or less, or in a carbon dioxide gas atmosphere. In this respect, the present invention has an advantage that it is not necessary to adjust the atmosphere, which is indispensable in the above-mentioned conventional method, and heating in the air is sufficient, whereby a good whisker can be formed.

d. The heat resistance of the stainless steel foil is further improved because Al diffuses and forms a solid solution in the steel during the above whisker treatment. In the conventional method of hot dip plating, low carbon steel is used instead of stainless steel, so that even if Al diffuses from the Al plating layer into the steel, the heat resistance is limited.

[Examples and Comparative Examples] Example 1 A stainless steel foil having the components shown in Table 1 (plate thickness 50 μm
After degreasing and pickling according to a conventional method using m), Al vapor deposition plating was performed on both surfaces of the stainless steel surface under the vapor deposition conditions shown in Table 2.

Subsequently, the Al-plated foil was heated to 900 ° C. for 10 minutes to 10 hours in the atmosphere to form whiskers. When the Al diffusion state in the steel during the whisker treatment was examined, the results shown in FIGS. 3 (a) and 3 (b) were obtained. FIG.
Shows the Al diffusion behavior in steel when a sample with a plating film thickness of 3 μm was heated to 900 ° C. in the atmosphere. As shown in FIG. 4A, it was confirmed from the chemical analysis result that the average Al content in the steel after the heat treatment at 900 ° C. for 3 hours was about 3%. The diffusion depth of Al was proportional to the heating temperature and the holding time, and the calculated diffusion coefficient was 2.17 × 10 ⁻¹⁰ (cm ² / s). Further, FIG. 3B shows the Al concentration distribution in the thickness direction of a sample having a plating film thickness of 3 μm after heating and holding at 900 ° C. for 1 to 3 hours in the atmosphere. 900 according to FIG.
It can be confirmed that the Al concentration inside the Al plating foil becomes substantially uniform by the heat treatment at 3 ° C. for 3 hours.

Next, the samples with plating film thicknesses of 1 μm, 3 μm and 7 μm
Scanning electron micrographs of the plated layer surface after heat treatment at 0 ° C. for 10 hours are shown in FIGS. 4 (a), (b) and (c). Further, FIG. 5 shows an X-ray diffraction chart of the plating layer of the sample prepared under the same conditions as in FIG. FIG. 4 (a)-
As shown in (c), fine and dense needle-like crystals are formed on the surface of the Al-plated stainless steel, and if the heat treatment conditions are the same, the thinner the plating film, the faster the growth of whiskers. Was confirmed. Further, it was confirmed from the chart of FIG. 5 that the whiskers were α-Al ₂ O ₃ .

Γ-Al ₂ O ₃ was further coated on the sample in which whiskers were formed by heat treatment at a plating film thickness of 3 μm at 900 ° C. for 10 hours under the conditions shown in Table ₃ . A scanning electron micrograph of the surface portion of the coating-treated sample is shown in FIG. In addition, after putting a 2 mm cross cut on the surface of the same sample, a test by peeling the tape is performed,
The adhesion of the coating layer was investigated. The results are shown in FIG. The degree of peeling in Fig. 7 is the total coating layer (γ-Al
₂ O ₃ ) Expressed by the ratio of the peeled area to the area. Sixth
As shown in the figure, γ-A was formed through α-Al ₂ O ₃ whiskers formed on the surface of the sample Al-plated stainless steel of this example.
The l ₂ O ₃ coating layer is adhered and the whiskers project into the coating layer to form a strong bond. Therefore, as shown in FIG. 7, it was confirmed that the coating layer had extremely high adhesion to Al-plated stainless steel.

Example 2 A stainless steel foil (plate thickness: 50 μm) having various Cr contents in the range of 2.5 to 25.8% was used as a plating base material.
In addition, the components (%) in steel other than Cr are C: 0.200-0.035, Si: 0.047-0.57 Mn: 0.18-0.36, P: 0.005-0.016 S: 0.006-0.018, Al: 0.06-0.20 Ti: 0.14-0.42 Is.

The stainless steel foil was subjected to Al plating under the same vapor deposition conditions as in Table 2 and then subjected to whisker treatment at 1000 ° C. for 5 hours and coated with γ-Al ₂ O ₃ under the conditions in Table ₃ .

The above samples were tested for whisker morphology and γ-Al ₂ O ₃ adhesion, respectively.

After the vapor deposition Al plating was applied to the above stainless steel foil, the heating and cooling cycle of heating at 1100 ° C. for 1 hour in the air and air cooling for 30 minutes was defined as one cycle, and the oxidation increase after 100 cycles of this was measured. The heat resistance was evaluated by.

Table 4 collectively shows these results. The evaluation criteria are as follows.

Whisker morphology x: Non-uniformity of whisker formation Δ: Coarse whisker formation ○: Uniform and fine whisker formation Adhesion of γ-Al ₂ O ₃ by tape peeling test x: Peeling rate of 15% or more △: Peeling degree of 10 to less than 15% ○: Degree of peeling less than 10% Heat resistance ×: Oxidation increase of 1 mg / cm ² or more ○: Oxidation increase of less than 1 mg / cm ² From this table, it can be seen that the samples having Cr contents of 2.5% or less (Nos. 1 to 4) have a problem in heat resistance of the substrate itself. The Cr content of 25.8% (No. 13 to 16) has both the adhesion heat resistance of the coating layer and the heat resistance of the base material which are satisfactory properties as a base material for a catalytic converter. The degree is equivalent to that of Cr content of 4.5 to 17.6%, so it can be seen that the Cr content is sufficient within the above range.

Further, it can be seen from this table that by applying the Al plating film, a γ-Al ₂ O ₃ layer having better adhesion than the conventional one is formed. The degree of peeling of the samples shown in Comparative Examples 1 and 2 described later are both 15% or more, while the degree of peeling of the samples according to the present invention is less than 15%. But
The peeling degree of those having a thickness of 1.5 to 7.5 μm is less than 10%, and the adhesiveness of the coating layer is greatly improved.

Example 3 A stainless steel plate having a plate thickness of 0.2 mm and having the following composition was subjected to vapor deposition Al plating having a thickness of 12 μm on one surface.

C: 0.010%, Si: 0.35%, Mn: 0.31%, P: 0.012%, S: 0.014%, Cr: 13.8%, Ti: 0.24%, the balance is Fe and unavoidable impurities. On the street.

Substrate temperature: 200 ° C, vacuum degree: approx. 1 × 10 ^-5 Torr Vapor deposition rate: 20 μm / min Deposition rate of the vapor-deposited Al-plated steel sheet produced under the above conditions is 75%
Cold-rolled to form an Al-plated stainless steel foil having a plate thickness of 50 μm and a plating film thickness of 3 μm. Further, the Al plating foil was heated in air at 900 ° C. for 10 hours to form whiskers, and γ-Al ₂ O ₃ was coated on the whiskers under the conditions shown in Table ₃ .

The substrate obtained by the above manufacturing process satisfied the evaluation criteria shown in Example 2 and satisfied all of the whisker morphology, the adhesion of γ-Al ₂ O ₃ , and the heat resistance.

Example 4 A stainless steel foil having the components shown in Table 1 (plate thickness 50 μm
m) is subjected to plating pretreatment such as degreasing and pickling by a conventional method, then dried and immediately immersed in a plating bath (bath temperature 20 ° C) that has been kept in an inert atmosphere in advance for Al electricity. It was plated. The plating bath was a molten salt bath containing 67 mol% of aluminum chloride (AlCl ₃ ) and 33 mol% of alkylpyridinium halide (C ₅ H ₅ N—R—Cl, where R is a methyl group or a butyl group). Benzene was added at 60 vol% to the above. For plating, the stainless steel foil was used as a cathode and an Al plate (purity 99.99% by weight) was used as an anode, and a direct current with an electric density of 3 A / dm ² was applied for about 5 minutes to obtain a thickness of about 3 μm on both sides of the stainless steel foil. Al plating was applied.

Subsequently, the Al plating foil was exposed to air for 10 hours at 900
The mixture was heated to ℃ to form whiskers, and γ-Al ₂ O ₃ was coated under the conditions shown in Table ₃ .

The catalytic converter substrate according to the present invention obtained by the above electroplating showed good results in the various tests shown in Table 4 like other substrates according to the present invention obtained by the vapor deposition Al plating.

Comparative Examples 1 and 2 Using a high Al-containing stainless steel having the components shown in the following table, a whisker treatment was performed by heating in the atmosphere at 900 ° C. for 10 hours in the same manner as in Example 1. The results are shown in FIGS. 8 (a) and 8 (b). As is clear from the figure, in each of Comparative Examples 1 and 2 having no Al plating film, the above whiskers cannot be formed by the heat treatment in the same atmosphere as in Example 1.
In the sample of Comparative Example 2, the above whiskers were not formed even by heating in CO ₂ gas at 900 ° C. for 10 minutes, and then the whiskers were formed only by further heating in air at 975 ° C. for 16 hours. However, no whiskers were formed in the sample of Comparative Example 1 under any of the above heating conditions.

Further, for Comparative Examples 1 and 2, after the above heat treatment, γ-Al ₂ O
₃ coated. FIG. 9 shows a partially enlarged photograph of the vicinity of the surface of the sample according to Comparative Example 1. Further, a peeling test of the coating layer was performed on these samples. The results are shown in Table 4. The results of Comparative Example 1 are shown in FIG. As shown in FIG. 9, the whiskers were not formed in the sample, and the boundary between the γ-Al ₂ O ₃ layer and the plating layer was a flat surface. Therefore, as shown in FIG. 7, the γ-Al ₂ O ₃ layer of Comparative Example 1 is easily peeled off and the adhesion is poor. Similarly, Comparative Example 2 also has poor adhesion as shown in Table 4.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example of a manufacturing process of a metallic frame according to the present invention, and FIGS. 2 (a), (b),
(C) is a schematic explanatory view of the foil surface related to whisker treatment or catalyst coating, and FIGS. 3 (a) and 3 (b).
Is a graph showing the Al diffusion state in Example 1, FIGS. 4 (a), (b), and (c) are electron micrographs showing the metal structure of the plating layer surface for the sample of Example 1, and FIG. 5 is the same. An X-ray diffraction chart of the sample, FIG. 6 is an electron micrograph showing the metal structure of the surface section of the sample, FIG. 7 is a graph showing the results of the peeling test, and FIGS. 8 (a) and 8 (b) are Electron micrograph showing the sawtooth structure on the surface of the sample of Comparative Example, No. 9
The figure is an electron micrograph showing the sawtooth structure of the surface partial cross section of the same sample. In the drawing, 10 ... Stainless steel foil, 11 ... α-AlO whiskers, 12 ... γ-AlO, 13 are metal catalysts.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Yusuke Hirose, 5 Ishizu Nishimachi, Sakai City, Osaka Prefecture, Nisshin Steel Co., Ltd., Hanshin Research Center (56) Reference JP 61-568 (JP, A) JP 62 -95142 (JP, A) JP-A-49-99985 (JP, A) JP-A-52-4491 (JP, A)

Claims (5)

[Claims] 1. A substrate for a catalytic converter, comprising a stainless steel foil as a frame, and at least one surface of the frame being coated with alumina for carrying a catalyst, comprising:
The above stainless steel is Cr: 3 to 25% by weight (hereinafter%), C: 0.08
% Or less, Ti: 0.05 to 0.5%, Al: less than 1%, Mn: 0.8% or less,
Si: 0.8% or less, balance consisting of iron and unavoidable impurities
Ti-containing stainless steel, Al plating is applied to the surface of the stainless steel by vapor deposition plating or electroplating, and the Al plating layer is formed by heat treatment at the same time as the vapor deposition plating or by heat treatment after the vapor deposition plating or the electroplating. α-
A substrate for a catalytic converter, characterized in that after forming Al ₂ O ₃ whiskers, γ-Al ₂ O ₃ is coated to form the alumina carrier. 2. The use of the stainless steel foil, wherein the foil surface is subjected to Al vapor deposition plating or Al electroplating, followed by corrugation and heat treatment to produce the whiskers. Substrate. 3. The plate thickness of the stainless steel foil is 25 to 90.
The substrate of claim 1 which is μm. 4. A stainless steel plate as described above is used.
The substrate according to claim 1, wherein after the aluminum vapor deposition plating or the aluminum electroplating, the steel sheet is rolled into a foil, corrugated, and then heat-treated to form the whiskers. 5. The thickness of the plating layer applied to the stainless steel foil and the thickness of the plating layer after the aluminum foil plating and the Al electroplating of the stainless steel plate and rolling to form a foil are 0.5 to 8.0 μm. The substrate according to claim 2 or 4, which is