JPH026851A - Catalyst carrier and its production - Google Patents

Abstract

PURPOSE:To increase the bonding strength of a base body to a thin alumina layer by providing the alumina layer on the surface of the porous base body consisting of the stainless steel, etc., having specified contents of Ti and C with an Al-O-Ti-C bond through an aluminum-iron alloy, etc. CONSTITUTION:A metallic wire is made of a stainless steel contg. at least 0.2-0.8wt.% Ti and 0.01-0.5 wt.% C or a nickel-based alloy. The surface of the metallic wire is then plated with aluminum, the plated metallic wire is then rolled, and the rolled metallic wire is formed into a corrugated porous body having unidirectional air permeability. The porous body is subsequently heat-treated at 600-1000 deg.C for >=10min to form a thin alumina layer firmly bonded with an Al-O-Ti-C bond on the surface of the porous body made of the metallic wire, and a catalyst carrier is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a metal catalyst carrier for a purification catalyst for purifying combustion exhaust gas discharged from automobiles, factories, etc., and a method for manufacturing the same.

(Prior Art) Conventionally, as a metal catalyst carrier, a technology has been proposed in which aluminum-containing ferritic stainless steel is used as a foil, and the foil is heat-treated to form alumina whiskers on its surface to be used as a carrier. It is disclosed in Japanese Patent No. 96.726. This technology uses stainless steel that can withstand high temperatures and has alumina whiskers on its surface, so it can be used as a wash coat using T-AI!
When a catalyst such as 203 is supported, the alumina whiskers act as a wedge, and a strong bond can be achieved between the wash coat layer made of r-A 120s or the like and the metal catalyst carrier.

(Problems to be Solved by the Invention) However, in the catalyst carrier disclosed in JP-A-56-96-726, the bond between the aluminum-containing ferritic stainless steel foil forming the base of the carrier and the alumina whiskers is Since this was achieved only through physical bonding rather than chemical bonding, there was a problem with the stability of the bonding force between the stainless steel foil and the alumina whiskers.

Furthermore, since the ferritic stainless steel used as the base material contains aluminum, its plastic workability is significantly reduced, and there is also the problem that it takes a lot of time and effort to make it into foil.

The object of the present invention is to solve the above-mentioned problems, to achieve a strong bond between the metal base material and the alumina thin layer constituting the catalyst carrier, and to provide a catalyst carrier and a method for manufacturing the same without deterioration of plastic workability. This is what we are trying to provide.

(Means for Solving the Problems) The catalyst carrier of the present invention contains a small amount of Ti (both 0.2 to 0.8 weight% (hereinafter referred to as wt%)) and CO9 old to 0.5W.
A thin alumina layer firmly adhered by Al-0-Ti-C bonds is applied to the surface of a substrate made of stainless steel or nickel-based alloy containing It is characterized by being formed into a porous body that has air permeability in both directions.

Further, the method for producing a catalyst carrier of the present invention includes at least Ti
0.2 to 0.8 wt% and 0.01 to 0.5 w of C
A metal strip is made from stainless steel or a nickel-based alloy containing t%, the surface of the metal strip is plated with aluminum, the plated metal strip is rolled, and the rolled metal strip is made permeable in one direction. A corrugate-like porous body,
After that, the porous body is heat-treated at 600 to 1000°C for 10 minutes or more, so that the surface of the porous body made of metal strips is
It is characterized by the formation of a thin alumina layer firmly adhered by j2-0-Ti-C bonds.

(Function) In the above-mentioned structure, since the stainless steel or nickel-based alloy that serves as the base contains a certain amount of TI and C, the aluminum plating provided on the surface may be oxidized by heat treatment. The alumina thin layer formed through the aluminum-iron alloy or aluminum-nickel alloy layer reacts with Ti and C in the metal, forming a strong Al-0-Ti-C bond at the interface, and the metal base material and the alumina thin layer react with each other. A strong bond can be achieved between the layers through chemical bonding.

In addition, by heat-treating the aluminum plating layer formed on the base material without adding Al to generate alumina whiskers in the base material, we can create a chemically bonded alumina thin film that has performance equivalent to or better than that of alumina whiskers. Since layers are formed, plastic workability does not deteriorate.

Furthermore, when performing aluminum plating as in the present invention, compared to coating with alumina etc.
Since there is no need for pretreatment such as roughening the plated surface, the process can be simplified. Note that because the aluminum plating layer is heat treated, an aluminum iron alloy layer or aluminum nickel alloy layer is generated between the aluminum plating layer and the base made of stainless steel or Ni-based alloy due to the diffusion of aluminum into the base. , this thickness is 40
If the thickness is less than μm, it will not affect adhesion.

The reason for limiting the amounts of T1 and C added is as follows. First, as for the lower limit, as is clear from the examples described later, the Ti content is less than 0.2 wt% or the C content is 0.2 wt%. When Q1wt% was less than 1wt%, this was because peeling of the alumina layer was observed. This is considered to be because sufficient Al-〇-TiC bonds cannot be formed due to the small amounts of Ti and C added. In addition, the content of C is 0.5wt
%, carbon will precipitate at the interface between the base metal and the alumina layer, making it brittle and easy to peel off. Further, when the Ti content exceeds 0.8 wt%, the thickness of the Ti-C bonding layer increases due to repeated heat treatments, and due to the hardness of the bond, the thicker the layer becomes, the easier it is to peel off. For the above reasons, T
0.2 to 0.8 wt% of 1, 0.01 to 0.5 w of C
It was limited to t%.

Regarding the Cr content, when C is limited to 0.12wt%, the desired tensile strength cannot be obtained if the strength in the annealed state is less than 1Qwt%, while even if it exceeds 25wt%, there is no significant improvement in strength. Therefore, the Cr content is preferably in the range of 10 to 25 wt%.

As for heat treatment conditions, a temperature lower than 600° C. is not practical because alloying requires a very long time and sufficient adhesion cannot be obtained. On the other hand, if the temperature exceeds 1000°C, the alloy layer will peel off due to rapid alloying into an aluminum-iron alloy layer or an aluminum-nickel alloy layer. In addition, if the heat treatment time is less than 10 minutes, alloying will not be sufficient and A
l-0-Ti-C bonds are not sufficiently formed and no improvement in strength is observed. Therefore, the heat treatment conditions are 600-1000℃
The duration was limited to 10 minutes or more within the range of .

Furthermore, if the thickness of the aluminum plating layer exceeds 10 .mu.m, as will be seen from the examples described later, it will be susceptible to peeling off due to the difference in thermal expansion.

On the other hand, it is very difficult to produce an aluminum plating layer with a thickness of less than 1 μm. Therefore, the thickness of the aluminum plating layer is preferably in the range of 1 to 10 μm.

Preferred embodiments of each component of the present invention will be described in more detail below.

(1) Regarding the substrate (a) Preferred embodiments of the shape of the substrate include those shown in Table 1 below.

Table 1 (b) Composition range of stainless steel (all units are wt)
%) It is necessary to have a composition consisting of the essential components and additional elements shown in Table 2 below.

Table 2 Table 3 Among these, preferable stainless steels include those with compositions shown in Table 3 below.

(C) Composition range of Ni-based alloy (all units are wt%)
) The composition must consist of the main components and additional elements shown in Table 4 below.

Table 4 Among these, preferable Ni-based alloys include alloys having the compositions shown in Table 5 below.

(2) Regarding the shape of the porous body As shown in Table 6 below, there is a preferred shape of the porous body for each base material.

Table 6 (3) Main component of aluminum plating layer is 3Q
It is preferably made of metallic aluminum of 1 wt % or more, and has a thickness of 1 to 10 μm, as is clear from the examples described later.

The aluminum plating layer can be formed by a conventionally known method such as hot-dip aluminum plating.

(4) ^f-0-600-10 for Ti-C bonding layer
After heat treatment at 00℃ for 10 minutes or more, there is a layer of less than 0.5μm at the interface between the base metal and the alumina thin layer! - A bonding layer of DTi-C is present. This is because Ti atoms in the base metal diffuse into the surface layer by heating to form TiC, and the intervening Ti atoms link C in the metal base and 0 atoms in the alumina thin layer, Aj! This is to form a -0-Ti-C bonding layer to form a strong bond.

(Example) As mentioned above, in order to achieve the helo-0-Ti-C bond of the present invention, stainless steel or It can be obtained by applying aluminum plating to the surface of a base material of a specified composition made of a nickel-based alloy and then carrying out a specified heat treatment at 600 to 1000°C for 10 minutes or more, but when actually applied to products, the following is shown. The method is preferred.

FIG. 1 is a flowchart showing an example of the method for manufacturing a catalyst carrier of the present invention. In the flowchart shown in Figure 1,
An example of producing a corrugated honeycomb carrier from metal strips is shown. First, a metal strip having the aforementioned predetermined composition is produced. Conventionally known methods such as rolling can be used to produce the strips. Next, the surface of the obtained metal strip is plated with aluminum lamb to a predetermined thickness, and then rolled into a metal foil.

The obtained metal foil is made into a corrugated foil, and the corrugated foil and the planar metal foil are alternately wound to produce a honeycomb-shaped base material. A predetermined heat treatment is performed on the obtained honeycomb-shaped base material to transform the aluminum plating layer into a thin alumina layer, and at the same time form an Al0-Ti-C bonding layer at the interface between the base metal and the thin alumina layer. A honeycomb-shaped catalyst carrier which also contains an aluminum-iron alloy layer or an aluminum-nickel alloy layer and has air permeability in at least one direction is obtained.

In the following, a practical example of the bond between the substrate and the thin alumina layer will be described.

Example First, in order to produce a metal strip to serve as a base, approximately 3 kg of ingots were melted in a vacuum melting furnace with stainless steel or Ni-based alloy prepared to the prescribed compositions shown in Tables 7 and 8 below. made. The resulting ingot having a predetermined composition was hot rolled, then cold rolled and annealed repeatedly to obtain a metal strip with a thickness of about 1 mm. The obtained metal strip was cut into a size of 100 x 500 mm and used as a test base material.

Next, aluminum plating was performed using the following procedure. First, aluminum containing 3 wt % of Si was prepared as aluminum for plating in order to perform hot-dip aluminum plating. Next, as a pretreatment of the base metal, the base material was treated in a mixed acid solution of 10% nitric acid and 2% hydrofluoric acid for about 10 minutes, and then washed with water. After immersing the pretreated base metal in the prepared aluminum melt, the amount of adhesion was adjusted using a gas wipe. The plating thickness was further adjusted by rolling the hot-dip plated base material, and the base material was cut into 100 mm square pieces as test base materials. The thickness of the plating was adjusted to 5 μm in all cases.

Thereafter, heat treatment was performed on the metal base material on which the aluminum plating layer was formed. The heat treatment was carried out by heating the plated metal base material in an electric furnace at 800° C. for 30 minutes.

In order to evaluate the characteristics, 900
A thermal shock test by heating and cooling was conducted using a device that automatically takes the material into and out of an electric furnace at ℃. 900 test cycles
The test specimen was subjected to 500 cycles of 15 minutes at °C and 45 minutes at room temperature, and the surface condition of the specimen was visually observed. Table 7 shows the results when the base material is stainless steel, and Table 8 shows the results when the base material is N1-based alloy.

Table 7 1 Table 2 Table 1 Table 3 Table 2 Table 3 From the results in Table 9, the thickness of the aluminum plating layer is 10
It can be seen that it is preferable that the thickness is μm or less.

Table 7 showing the results for stainless steel as the base material and N1
From Table 8 showing the results of the base alloys, TI and C of the present invention
It can be seen that in the examples where the composition range of Ti or C does not satisfy the composition range of the present invention, there is no abnormality at all in the thermal shock test, whereas in the examples where the composition range of Ti or C does not meet the composition range of the present invention, some peeling occurs.

Further, among the above-mentioned examples, thermal shock tests were similarly conducted on stainless steel and Ni-based alloy base materials satisfying the composition range of the present invention while changing the thickness of the aluminum plating layer. The results are shown in Table 9.

Furthermore, among the above-mentioned examples, 50%
After heat treatment at a temperature of 0 to 1100°C for various times, the cross section was observed using a microscope to investigate the heat treatment conditions. In addition,
At this time, the thickness of all aluminum plating layers was 5 μm. The results are shown in Table 10.

Table 10 From the results in Table 10, the heat treatment conditions are 600 to 1000℃.
You can see that it needs to be 10 minutes or more.

Further, composition Ti in the above-mentioned examples: 0.580. C:
0.042°Cr: 19.0. S: 0,03. M
o:1.00. Ni+11.0. Fe: 5 μm aluminum plating is applied to the stainless steel base material consisting of the remainder, and 9
Auger analysis of the material heat-treated at 00°C for 10 minutes shows the result as shown in Figure 2, where the concentration of Ti and C is high near the interface between the surface oxide layer and the alloy layer.<10-Ti-C bonds are formed. It is shown that.

(Effects of the Invention) As is clear from the above description, according to the catalyst carrier of the present invention and the method for producing the same, since the metal base contains a predetermined amount of Ti and C, the metal base and the alumina thin layer A chemically strong bonding layer of A, 12-O-TiC can be formed between the substrate and the alumina thin layer, thereby achieving a strong bond between the substrate and the alumina thin layer. In addition, since a thin alumina layer is generated by heat-treating the aluminum plating layer without adding Al to generate alumina whiskers in the base, there is no deterioration in plastic workability and it is a simple process. A catalyst carrier having air permeability in at least one predetermined direction can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an example of the method for manufacturing the catalyst carrier of the present invention, and FIG. 2 is an explanatory diagram showing the results of Auger analysis of the catalyst carrier of the present invention. Figure 1

Claims (1)

[Scope of Claims] 1. At least 0.2 to 0.8 wt% of Ti and C0.
A thin alumina layer firmly adhered by Al-O-Ti-C bond is applied to the surface of a substrate made of stainless steel or nickel-based alloy containing 01 to 0.5 wt% via an aluminum-iron alloy layer or an aluminum-nickel alloy layer. A catalyst carrier, characterized in that it is formed into a porous body having air permeability in at least one direction. 2, at least 0.2-0.8 wt% Ti and C0.
After producing a metal strip from stainless steel or nickel-based alloy containing 01 to 0.5 wt%, applying aluminum plating to the surface of the metal strip, and rolling the plated metal strip,
The rolled metal strip is made into a corrugated porous body with air permeability in one direction, and then the porous body is heated at 600 to 1000°C.
A method for producing a catalyst carrier, which comprises performing a heat treatment for 10 minutes or more to form a thin alumina layer firmly adhered to the surface of a porous body made of a metal strip by Al-O-Ti-C bonds. .