JPH02207995A - Brazing material for joining metallic catalyst carrier and production of metallic catalyst carrier - Google Patents

Abstract

PURPOSE:To provide a brazing material for joining metallic catalyst carriers which can maintain sufficient oxidation resistance and toughness over a long period of time in a waste gas by incorporating respectively prescribed ratios of Cr, Si, Al, P, and S therein, incorporating substantially no Ni therein and consisting the balance essentially of Fe. CONSTITUTION:The above-mentioned brazing material for joining is composed of contain, by weight %, 15 to 40% Cr, 1 to 10% Si, 1 to 10% Al, 0.1 to 5% P, and 0.005 to 0.3% S, and to contain substantially no Ni and is constituted of the balance substantially Fe. This brazing material for joining has excellent wettability with the surfaces of stainless steel sheets and does not contain the Ni and, therefore, the brazing material does not form an Ni-Al alloy and does not consume the solid soln. Al necessary for forming an Al2O3 film which withstands hightemp. oxidation. The deterioration in the oxidation resistance and toughness of the Al-contg. metallic carriers brazed by using the above- mentioned brazing material is consequently prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a brazing material for bonding metal carriers of catalysts mainly used in purification devices for automobile exhaust gas, etc., and to manufacturing metal catalyst carriers using the brazing material. It is about the method.

[Conventional technology]

In recent years, automobile exhaust gas regulations have been enacted, and it has become customary for passenger cars to be equipped with exhaust gas purification devices. There were several methods of automobile exhaust gas purification systems, but they oxidized HC and CD using a catalytic converter, and at the same time oxidized NL.
Currently, the type that reduces The structure of the catalytic converter is a carrier made of fired ceramics whose main component is cordierite in the form of a honeycomb, and γ-M203 powder supporting a precious metal catalyst such as PT is attached to this carrier to impart purification and stagnation ability. This is now widely used. However, this ceramic honeycomb has drawbacks such as being weak against mechanical shock and having high exhaust resistance.

Recently, in order to deal with this problem, ferritic stainless steel containing 10% or less of M is rolled into a foil with a thickness of several tens of microns, and this flat plate is further formed into a corrugated plate and then layered. , are laminated or rolled into a honeycomb shape, and then joined by brazing or the like.The stainless steel surface is then coated with M, 0. Japanese Patent Publications No. 54-15035 and Japanese Patent Publication No. 58-23138 disclose a carrier prepared by coating a film with 7M2Q3.

Vacuum brazing is generally used to join these metal carriers, and the brazing filler metal used is N1-based BNi-5 (19Cr
-10Si -Ni remainder) is - front reduction. As already mentioned, the feature of this metal support is that it forms an At 2 Q 3 film on the surface of the high M-containing ferritic stainless steel, which serves as a supporting matrix for 7-pi203, and
That N20. The film also acts as a barrier against the harsh high-temperature corrosive environment of exhaust gas. However, when a Ni-based brazing filler metal is used to join these metal carriers, the Ni in the brazing filler metal easily diffuses under high temperatures during use and reacts with M in the base material, which is several tens of microns thick, resulting in N1 -N20. forms M alloy and resists high temperature oxidation. A major problem arises in that the solid solution M required to form a film is consumed. In addition, during actual use, large thermal stress is generated due to the temperature distribution within the carrier and rapid temperature changes.
Deterioration of foil due to M alloy formation is a major factor in the destruction of metal carriers, and has become a serious problem.

[Problem to be solved by the invention]

In view of these drawbacks of brazing filler metals, the present invention provides a brazing filler metal for bonding vine metal catalyst carriers that maintains sufficient oxidation resistance and toughness in exhaust gas for a long period of time, and a method for manufacturing metal catalyst carriers using the brazing filler metal. The purpose is to provide

[Means to solve the problem]

The present invention contains 15 to 40% Cr by weight.

10-25% Si, 1-10% M, Q, 1-5% P1
This is a brazing material for bonding metal catalyst carriers, which contains 0.005 to 0.3% S, the balance substantially consists of Fe, and substantially does not contain N1. The brazing filler metal of the present invention preferably has the chemical composition described above and is made into powder by gas atomization. The present invention also provides 15 to 4% by weight.
0% Kano, 10~25%5i11~10%Ae, Q, l~
Contains 5% P, the remainder substantially consists of Fe, and substantially N.
The present invention provides a brazing material component for joining metal catalyst carriers, which is characterized in that it does not contain i. S-containing precipitates such as surfactants (for example, sodium lauryl sulfate) and S-containing inorganic substances such as IJum are added to the powder obtained by pulverizing this brazing material component by a gas atomization method. A brazing filler metal mixed in an amount of 0.005 to 0.3% is also a brazing filler metal of the present invention. In this way, in the brazing material of the present invention, S may be melted by mixing it with other components at the same time, or by adding a compound containing S to an alloy powder obtained by melting components to which S is not added. May be mixed.

The present invention further provides a method for producing a metal catalyst insect body using the brazing filler metal, and a method of mixing the S-containing compound with the brazing filler metal component in an amount of 0.005 to 0.3% as S. The present invention provides a method for manufacturing a metal catalyst carrier, which is characterized in that it is used as a brazing material.

The present invention will be explained in detail below.

[For production]

The brazing filler metal for joining metal carriers of the present invention eliminates N+, which consumes M in the base material, which is the most important for the joined metal carriers to maintain excellent oxidation resistance and toughness over a long period of time in high-temperature exhaust gas. The biggest feature is that it does not contain any That is, in the case of a foil having a thickness of several tens of microns, the M concentration in the foil decreases due to the growth of a surface film of Al 2 Q 3 during use at high temperatures. On the other hand, the M2O3 film has a strong effect of suppressing the oxidation of the underlying metal, and when the film reaches a predetermined thickness determined by the atmosphere composition and temperature, the oxidation rate of the underlying metal becomes extremely small, and the growth of the M2O3 film also slows down. It almost stops at this point. N20. As the film grows, M in the underlying metal
The concentration continues to decrease, but if the Hfi degree in the underlying metal falls below 2% before reaching a film thickness that provides sufficient protection,
The Al2O film begins to contain oxides of Cr and Fe, reducing the protective properties of the film and increasing the oxidation rate, until the entire foil is oxidized and loses its function as a supporting matrix for the catalyst. . In view of this, the foil material usually contains 5% or more of M.

However, as mentioned above, BNi-
5 (19cr-10Si-Ni remainder) vacuum brazing method is adopted using a solder powder, and the Ni in the solder diffuses into the solder and becomes Ni-Al! A problem occurred in that the solid solution M necessary for forming the alloy and forming the Al2O3 film was consumed, and at the same time, the foil became brittle due to the precipitation of the N1-M alloy phase. For this reason, attempts were made to keep the M content in Rakuchu excessively high and to limit the amount of solder used, but these efforts resulted in new problems such as a decrease in the manufacturability of the foil and a decrease in reliability as a structure. This caused a problem. After various studies including the wettability of the wax, the inventors found that the above object can be achieved by not including Ni in the wax, and have completed the present invention.

In the brazing filler metal of the present invention, the content of Cr needs to be 15% or more from the viewpoint of oxidation resistance, but if it exceeds 40%, the precipitation of foreign phases will be promoted in combination with the high concentration of M. 40% is appropriate.

Si is an important element that lowers the melting point, and its content is 1
Although the range is 0 to 25%, addition of about 20% is most preferable. Even if it increases or decreases beyond this range, the effect of lowering the melting point will be small.

M is added to reduce the surface tension of molten solder during brazing and to improve oxidation resistance. It is necessary to add 1% or more in order to lower the surface tension, and conversely, if it exceeds 10%, brazing will result in a reaction with residual oxidizing components in the atmosphere and N20.
Since M forms an extremely poor wetting of the solder, an appropriate M content range is 1 to 10%.

P is added for the purpose of lowering the melting point, and in order to confirm the effect of addition, it is necessary to add 0.1%, and the larger the amount added, the greater the decrease in the melting point, but it is accompanied by a deterioration of oxidation resistance. . Taking this into consideration, the range of P content was set to 0.1 to 5%.

S is added to lower the surface tension of molten solder, and in order to confirm the effect of addition, it is necessary to add 0.005%, and as the amount added increases, the surface tension of 1.0% decreases. However, as the amount added increases, brazing tends to leave slag on the part surface. From this, it is appropriate that the S content ranges from 0.005% to 0.3%. Here, even if S is not added during melting, S can be enriched during melting by mixing organic or inorganic substances containing S into the wax powder after powdering.

The brazing filler metal of the present invention usually contains 0.1% or less C, 0.1% or less B, 2% or less ζJn, and 2% or less Ni as unavoidable elements during melting. In addition, to increase the oxidation resistance of the material:
Nb, Zr, Hf and up to 0.5% RE V may be added.

The brazing filler metal of the present invention is produced by melting it using a normal melting method and then powdering it. The most preferable powdering method is gas atomization. There are other powderization methods, such as water atomization and pulverization, but both of them involve a large degree of oxidation during the powderization process, resulting in a high oxygen content, and brazing has poor wettability. inhibit.

These wax powders are used as follows.

In other words, a flat plate made of foil with a thickness of several tens of microns and a wavy plate made from the same are layered together and rolled into a roll.The ends of the honeycomb body are dipped in a binder, and then the wavy plate and the flat plate are formed. The excess binder other than the contact area is removed, and wax powder is applied to the remaining binder by sprinkling, and the corrugated plate and flat plate are joined by vacuum brazing. The present invention will be specifically explained below using Examples.

[Example-1] A filler material having a chemical composition shown in Table 1 was melted in a 5 kg high-frequency melting furnace sealed with argon, and then powdered by a gas atomization method using argon gas.

This material was sieved to select powder with a particle size of 40 to 105 μm, which was used as a sample. Since the basic characteristic of brazing filler metals is wettability, we first compared wettability. The collected powder was put into a compressor with an inner diameter of 5 mm, and under pressure of 3000 kg, pancakes with a diameter of 5non and a thickness of 1ff1m were made. This material is 20Cr-5M with a thickness of 1 mm.
-0,15Nb-0,04Ce-0,015(C+N
) on a stainless steel plate with a composition of 1230
Vacuum heating for 30 minutes at ℃ (on the order of 10-'Torr)
The contact angle between the surface of the stainless steel plate and the molten solidified brazing filler metal at room temperature was measured. Note that the contact angle was measured at the center cross section. The measurement results are shown in Table 1. In Table 1, Nα5 and Nα6 are the brazing filler metal components of the present invention, Nα7
~Nα13 is the brazing filler metal of the present invention, and the others are comparative examples. When evaluating wettability, it is judged that the smaller the contact angle, the better, and preferably 20° or less. Judging from this point, it can be said that the brazing filler metal and brazing filler metal components of the present invention exhibit clearly superior wettability compared to the comparative example. In particular, since Ni reacts with M in the base material to form an N1-M alloy and deteriorates oxidation resistance, attempts to reduce the amount of Ni added to deal with this problem may end in failure. I can see it. Adding Ni halfway can be judged to have the opposite effect in terms of wettability, and this is the gist of the present invention, which does not include Ni.

[Example-2] 20Cr-5AI-o, 15Nb-0,04Ce-0
,015 (C1N) stainless steel, plate width 50
A rolled foil with a thickness of 50 μm was made, and this was processed into a trapezoidal corrugated plate with a height of 1.25 mm and a pitch of 2.5 mm, which was overlapped with a flat plate and rolled into a roll with an outer diameter of 30φ. The outer edge was fixed with a spot. This product was immersed in a 1% PVA aqueous solution (binder), and the excess binder was removed with compressed air.
105μmφ) to adhere to the binder, and vacuum brazing (10-'Tor) at 1230℃ x 30 minutes.
r order) was performed. This product was cut and the bonded state was observed and compared with that using conventional BNi-5 solder powder, and it was found to be completely comparable. Also, 1100℃×200
No abnormalities were observed even after atmospheric oxidation over time.

[Example-3] 2% by weight of a surfactant (sodium lauryl sulfate) was added to wax powder No. 6 (40 to 105 μmφ) in Table 1 and dried at 150° C. for 2 hours. This material was pulverized in a pot to return it to its original state, and a carrier was produced in the same manner as in Example-2. This material was evaluated in the same manner as in Example-2, and it was confirmed that it had properties equivalent to those of Nα7 brazing material.

Table 1 Chemical composition and wettability of brazing filler metal baj! : Remainder [Effect of the Invention] The brazing filler metal of the present invention has excellent wettability to the surface of a stainless steel plate, and since it does not contain Ni, it does not form an N1-M alloy and has M, 0, which is resistant to high temperature oxidation. ．． Since the solid solution M necessary for forming the film is not consumed, deterioration of the oxidation resistance and toughness of the M-containing metal carrier brazed using this can be prevented.

Claims (4)

[Claims] (1) In weight%, 15-40% Cr, 10-25
%Si, 1-10% Al, 0.1-5% P, 0.005
A brazing filler metal for bonding metal catalyst carriers, characterized in that it contains ~0.3% S, the remainder is substantially Fe, and is substantially free of Ni. (2) A method for manufacturing a metal catalyst carrier, which comprises brazing using the brazing material according to claim (1). (3) In weight%, 15-40% Cr, 10-25
%Si, 1 to 10% Al, and 0.1 to 5% P, the balance being substantially Fe and substantially not Ni. (4) Brazing is performed using a brazing material obtained by mixing a compound containing S with the brazing material component described in claim (3) so that the amount of S is 0.005 to 0.3%. A method for producing a featured metal catalyst carrier.