JP3247210B2 - Metal sintered body and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a catalyst carrier, a heater,
The present invention relates to a metal sintered body having excellent thermal shock resistance, high-temperature oxidation resistance, and corrosion resistance that can be suitably used as a main monolith catalyst of a catalytic converter, and a method for producing the same.

[0002]

2. Description of the Related Art Catalytic converters are used in automobile exhaust gas systems and include a main monolith catalyst for purifying exhaust gas with a so-called three-way catalyst. Also, in the main monolith catalyst,
Satisfactory purification efficiency is obtained after the exhaust gas has warmed above a certain temperature at which catalytic reaction occurs, but purification efficiency when the exhaust gas temperature is not warm, such as when starting the engine, is limited. Therefore, it has been proposed to provide a preheater upstream of the main monolith catalyst for heating unheated exhaust gas. The honeycomb structure is preferably used for both the main monolith catalyst and the preheater, and the exhaust gas can pass through the through holes of the honeycomb structure. In any case, the surface of the through hole may be coated with the catalyst layer. In recent years, as a catalyst carrier for carrying a catalyst for purifying nitrogen oxides, carbon monoxide, and hydrocarbons in exhaust gas discharged from an internal combustion engine of an automobile or the like, a metal plate is wound into a corrugated shape to form a honeycomb structure. Those which have been used have begun to be used, for example, those described in Japanese Patent Publication No. 58-23138. However, Japanese Patent Publication No. 58-
In the foil-type metal honeycomb structure described in Japanese Patent No. 23138, the metal substrate on which the coating is formed has poor porosity, so that the adhesion to the catalyst layer is weak, and the thermal expansion difference between the catalyst layer, which is a ceramic, and the metal substrate. There is a disadvantage that the catalyst is easily peeled off. In addition, during the operation cycle, the telescope phenomenon that the metal-metal joint peels off and deforms into a convex part in the gas flow direction is likely to occur, which may be a serious hindrance in operation, and furthermore, manufacture of foil type metal honeycomb. In the process, there is a problem that the foil rolling yield is poor and the production cost is high.

[0003] It is also known to obtain a honeycomb structure by molding and firing metal powder. Examples of such a honeycomb structure include JP-A-63-310942, JP-B-57-6974, and JP-A-57-578.
No. 03, JP-A-57-57804 and JP-A-4-308004 have been proposed. JP-A-63-310942 discloses that A
1 to 5 to 50%, Fe to 30 to 90%, Sn to 0 to 10
%, Cu is 0 to 10%, Cr is 0 to 10%, and a honeycomb structure having a composition of Mg and / or Ca of 1% or less and having a porosity of about 25 to 75% and a predetermined cell density. It is shown. Japanese Patent Publication No. 57-6974 discloses a honeycomb structure in which powders of catalytically active substances such as nickel, copper, and chromium are used as exhaust gas purifying catalysts as honeycomb components of small pieces and bundled. However, this honeycomb structure is only oxidized at a low temperature in order to obtain a catalytic activity, and has a defect that heat resistance is insufficient and the honeycomb structure is not integrated and is broken by vibration during practical use.

Further, JP-A-57-57803 and JP-A-57-57804 disclose a method in which a thermosetting binder, colloidal silica or the like is added to a metal powder, extruded into a honeycomb shape, and cured after sintering. A metallic honeycomb-shaped structure is shown, in which SUS powder and Al, C
u, Ti, Zr only, Fe-Ni-Cr-Al
There is no description about the alloy composition of the system and the additive elements thereof, and there is a problem that the obtained metal honeycomb structure has poor oxidation resistance. JP-A-4-308004 discloses that Cr
5 to 40% by weight, 2 to 30% by weight of Al, 5% by weight or less of a specific metal, 4% by weight or less of a rare earth oxide additive, and a balance consisting of an iron group metal and unavoidable impurities, The specific metals are Y, lanthanoids, Zr, H
at least one selected from f, Ti, Si, and B;
Alternatively, an alloy composition which is at least one selected from alkaline earth metals, Cu, and Sn is disclosed, and a honeycomb structure having this alloy composition is disclosed. However, substantially only iron is disclosed as the iron group metal, and the balance is Ni or an alloy composition containing Ni is not substantially described.

On the other hand, Ni-based alloys are disclosed, for example, in
No. 3,580,37, U.S. Pat. No. 3,591,362.
No. 3,964,877; U.S. Pat. No. 4,359,352; U.S. Pat. No. 4,427,44.
No. 7 and U.S. Pat. No. 4,995,922. JP-A-4-358037 discloses a Ni-based heat-resistant alloy having excellent high-temperature strength and corrosion resistance, in terms of% by weight, C: 0.01% by weight or less, Si: 1.0% by weight or less, Mn: 0.2 wt% or less, Cr: more than 5 wt% to 18 wt%, Al: 4.5 to 12 wt%,
Further, B: 0.001 to 0.03% by weight, Zr: 0.
01 to 0.3% by weight, Hf: 0.05 to 1.0% by weight,
Ti: 0.05 to 1.0% by weight and Mg: 0.001 to
0.02% by weight, the balance being Ni or Ni
And Ni comprising 5% by weight or less of Fe and unavoidable impurities
A base heat resistant alloy is disclosed. United States Patent No. 3,59
No. 1,362 discloses a mechanical alloying powder having a composition by weight of Cr: 65% by weight, Al: 8% by weight, Ti: 8% by weight, Mo4
0% by weight or less, W 40% by weight or less, Nb: 20% by weight or less, Ta: 30% by weight or less, Cu: 40% by weight or less,
V: 2% by weight or less, Mn: 15% by weight or less, C: 2% by weight or less, Si: 1% by weight or less, B: 1% by weight or less, Z
r: 2% by weight or less, Mg: 0.5% by weight or less, high-melting point compound of 10% by volume or less, and Fe, Ni and / or C
o is 25% by weight or more.

US Pat. No. 3,964,877 discloses a heat-resistant member having a density of 65 to 90% of the theoretical density, the composition of which is 15 to 35% by weight of Cr,
1 is 8 to 20% by weight, at least one selected from the group consisting of Y, Hf, and rare earth elements is 5% by weight or less, and the balance is Fe, Ni, Co and unavoidable impurities. U.S. Pat. No. 4,359,352 discloses cooling rates of 10 ⁵ to 10 ^7.
C / sec; solidified with face-centered cubic structure, average particle size about 2
A Ni-based alloy having a microstructure mainly containing a Ni solid solution phase of less than μm and having a very small composition deformability is disclosed. The composition of this Ni-based alloy is as follows: Ni is 50 atomic% or more;
20 atomic%; at least one of Cr, Co, Fe, W and Mo is 8 to 43 atomic%, and the total amount of W and Mo is 15 atomic% or less; C, Hf, Zr, V, Mn, Si and At least one kind of Mg is 0.1 to 4.0 atomic%, and further contains 0.4 to 1.7% by weight of B.

US Pat. No. 4,427,447 discloses a metal powder mixture mechanically alloyed to an oxide dispersion strengthened high temperature alloy, the mixture comprising up to 30% by weight of Cr and up to 3% by weight of Ti. , Containing 0.3 to 10% by weight of Al and 0.3 to 10% by weight of an oxide dispersed phase (however, the negative free energy of formation at 1000 ° C. is larger than that of alumina); And Co; and part or all of the oxide dispersed phase is Al ₂ O ₃ .2.
Y ₂ O ₃ , Al ₂ O ₃ .Y ₂ O ₃ , and 5Al ₂ O ₃ .3Y ₂ O ₃
At least one or more composite oxides. This patent does not contain both iron and Ni at the same time. U.S. Pat. No. 4,995,922 discloses an oxide dispersion hardened Ni-based superalloy, the composition of which is Cr
5 to 13.95% by weight, Al 2.5 to 7% by weight, C
o is 10% by weight or less, Mo is 2% by weight or less, W is 15% by weight or less, Ta is 7% by weight or less, Ti is 3% by weight or less,
Hf is 1% by weight or less, Zr is 0.02 to 0.2% by weight,
Y ₂ O ₃ contains 1 to 2% by weight or less, C contains 0.2% by weight or less, the balance is Ni, and B may contain 0.026 to 0.3% by weight. This alloy composition does not contain Fe.

[0008]

The catalyst carrier is exposed to a corrosive and high-temperature environment, such as when the metal sintered body is used as a carrier of an exhaust gas purifying catalyst composition in an exhaust gas system of an automobile. , Oxidation resistance and corrosion resistance are required. In these applications, rapid heating and cooling are repeated many times when the engine is started and stopped, and therefore, high thermal shock resistance is required. Accordingly, an object of the present invention is to improve the thermal shock resistance, the oxidation resistance at high temperatures, and the corrosion resistance of a metal sintered body.

[0009]

According to the present invention, 5 to 40% by weight of Cr, 2 to 30% by weight of Al, and 5 to 1 % of Fe are used.
5% by weight and 0.005 to 0.1% by weight
B, 0.05 to 5% by weight of Ti and / or Si, and
Consisting of Zr, Hf, Group 3A and lanthanoid elements
0.05 to 2. at least one metal selected from the group;
5 containing by weight%, the balance Ru are metal sintered body provided for being Ni and inevitable impurities. In the present invention, 0.1 to 2.5% by weight of at least one oxide selected from the group consisting of SiO ₂ , group 3A oxide, lanthanoid oxide and group 4A oxide is contained in addition to the above components. Is preferred. Preferably, the oxide is Y ₂ O ₃ .

In the present invention, Ni is preferably contained in an amount of 5% by weight or more, more preferably 10 to 30% by weight. Further, it is preferable to contain 10 to 30% by weight of Cr. In the present invention, Al is preferably contained in an amount of 5 to 15% by weight, and more preferably 8 to 15% by weight. Further, according to the present invention, there is provided a honeycomb structure formed of the above-described metal sintered body and having a large number of through holes. Also,
In the present invention, it is preferable that the honeycomb structure is formed by extruding a powdery raw material into a honeycomb shape and sintering. Further, according to the present invention, there is provided a metal sintered body supporting the catalyst composition.

Further, according to the present invention, there is provided a monolith catalyst for purifying exhaust gas from automobiles, wherein the metal sintered body described above is used as a catalyst carrier, and a catalyst composition is supported on the catalyst carrier. You. It is preferable that the metal sintered body serving as the catalyst carrier has a honeycomb shape, and that the catalyst composition is supported on the surface of the through hole of the honeycomb structure. At this time, when the exhaust gas passes through the through-hole, harmful substances in the exhaust gas are removed by the catalyst composition. Further, according to the present invention, there is provided a heat-resistant heater comprising the above-mentioned metal sintered body and a heating means for heating the metal sintered body. When the temperature for activating the catalyst has not been reached, such as when starting the engine, the catalyst can be heated by the heat-resistant heater. The heating means includes, for example, an electrode provided on the metal sintered body for flowing an electric current through the metal sintered body. It is preferable that the metal sintered body is a honeycomb structure and the exhaust gas can flow through the through-hole.

Further, according to the present invention, there is provided a heat-resistant heater comprising a metal sintered body supporting a catalyst composition and a heating means for heating the metal sintered body. . Still further, according to the present invention, there is provided a main monolith catalyst element, a metal sintered body described above, and a heater element having heating means for heating the metal sintered body. A catalytic converter is provided, characterized in that the heater element is arranged upstream and / or downstream. Further, according to the present invention, there is provided a main monolithic catalyst element, at least one heater element having the metal sintered body described above and a heating unit for heating the metal sintered body, and at least one of the heater elements On the one hand, there is provided a catalytic converter, characterized in that the catalytic composition is supported and arranged upstream and / or downstream of the main monolithic catalytic element. According to the present invention, there is provided a catalyst comprising the above-described metal sintered body, a catalyst composition supported on the metal sintered body, and heating means for heating the metal sintered body. A converter is provided.

Still further, according to the present invention, a metal powder is mixed so as to have the above-mentioned alloy composition to form a mixed powder, and the mixed powder is formed into a compact to obtain a sintered compact. A method for producing a metal sintered body, characterized by sintering the molded body at a suitable temperature for a sufficient time under a non-oxidizing atmosphere.

[0014]

Hereinafter, the present invention will be described in detail. The metal sintered body of the present invention has an Fe-Ni-Cr-Al-based composition, and may contain other specific elements at a fixed ratio. Although the metal sintered body of the present invention has a long life, this is due to heat resistance, mechanical strength, erosion resistance, and oxidation resistance at high temperatures. In the specific composition of the sintered body, oxidation resistance,
Particularly excellent in thermal shock resistance and mechanical stress.

Although the sintered body can have various shapes and sizes, a honeycomb structure is generally desirable. In the present invention, the honeycomb structure refers to an integrated structure having a large number of through holes, that is, cells, partitioned by partition walls. The cross-sectional shape (cell shape) of the through hole is circular,
Various arbitrary shapes such as a square shape and a corrugated shape can be adopted. Among these, a shape such as a hexagon that can relieve thermal stress is preferable. The length of the honeycomb structure is not limited in any direction. For example, the diameter, length, number of cells, and thickness of partition walls of the cells can be arbitrarily changed depending on the application.
Extruded honeycomb structures are particularly preferred. The sintered body is preferably dense, and the denseness is determined by the porosity expressed by volume percent as a parameter. The sintered body preferably has a porosity of 5% or less. In this range, the surface area of the sintered body becomes sufficiently small, and excellent in oxidation resistance and corrosion resistance at high temperatures. However, it is preferable to have some pores from the viewpoint of supporting the catalyst.

The sintered body of the present invention is produced by sintering powder, and in the sintering step, mutual diffusion occurs between individual powders. Therefore, the distribution, size, ratio, and the like of pores can be controlled by utilizing the surface effect (for example, contained impurities, oxidation state, surface area, and the like) of the starting powder and solid phase diffusion. However, in the cast body produced by cooling the molten metal, diffusion and homogenization in the liquid phase occur, so using the morphology and surface effects of the starting material, control of pore distribution, size, ratio, and crystal grain size No control. Therefore, the sintered body of the present invention is completely different from the molten alloy body in the microstructure (metal structure) governing the properties of the material. In the present invention, the surface of the sintered body is preferably covered with an oxide film. This oxide film improves the oxidation resistance and corrosion resistance of the sintered body. Since the sintered body of the present invention contains Al, an oxide film mainly made of aluminum oxide can be formed on the surface of the sintered body by exposing the sintered body to a high-temperature oxidizing atmosphere. The oxide film thus obtained is formed by the reaction of aluminum in the sintered body, and therefore has good adhesion to the sintered body. In addition, the oxide film obtained by an appropriate method is dense and hardly permeates oxygen, and can improve oxidation resistance and corrosion resistance at high temperatures. Therefore, it is preferable to use the sintered body in a state covered with the oxide film. Furthermore, since the oxide film is an oxide, a washcoat made of alumina, ceria, zeolite, or the like that supports a catalytically active metal is difficult to peel off, and is preferable because the catalyst composition is easily supported.

The metal sintered body of the present invention contains Cr and Al. Both metals have an effect on the oxidation resistance and corrosion resistance of the metal sintered body. In particular, Cr is effective for corrosion resistance, and Al is effective for oxidation resistance. In the present invention, the content of Cr is 5 to 40% by weight, preferably 10 to 30% by weight. C
When the content of r is less than 5% by weight, the formation of an oxide film is adversely affected, and the oxidation resistance and corrosion resistance are not sufficient. on the other hand,
If the content of Cr exceeds 40% by weight, the brittleness of the sintered body increases. In the present invention, the content of Al is 2 to 30% by weight, preferably 5 to 15% by weight, and more preferably 8 to 15% by weight. As described above, Al is necessary to form a protective film containing aluminum oxide, and is an effective element for improving oxidation resistance. If the Al content is less than 2% by weight, the formation of an alumina oxide film is insufficient, and the oxidation resistance of the sintered body is not sufficient. On the other hand, when the Al content is more than 30% by weight, the brittleness of the sintered body increases.

On the basis of the alloy composition based on Fe,
When Fe was replaced with Ni in this alloy composition, the mechanical strength of the alloy was improved in proportion to the amount of Ni replaced, and it was found that the thermal shock resistance was maximized with the composition using Ni as the base. . However, if the Fe content is less than 5% by weight, the sulfated corrosion resistance of the sintered body will not be satisfactory. Therefore, in the metal sintered body of the present invention, the Fe content is 5 to 15 % by weight.
% . Further, by replacing Ni, the solution corrosiveness to hydrochloric acid, sulfuric acid and the like is also improved. Ni content is preferably 5
% By weight or more, and more preferably 10% by weight or more. In these ranges, the high temperature strength is remarkably improved, and the thermal shock resistance is greatly improved. In some cases, the Ni content is preferably 30% by weight or less. This is because if Ni exceeds 30% by weight, the oxide film may peel off depending on the conditions.

In the metal sintered body of the present invention, it is preferable to add B as a sintering aid in order to densify the sintered body.
If B is less than 0.005% by weight, there is no effect of addition, while if B is more than 0.1% by weight, the oxidation resistance of the sintered body deteriorates. When the metal sintered body of the present invention contains Ti,
This is preferable because the mechanical strength, particularly at high temperatures, is improved. In particular, in an alloy composition using Ni as a base, addition of Ti is preferable. If Ti is less than 0.05% by weight, there is no effect of addition, while if Ti exceeds 5% by weight, the sintered body becomes brittle, and the melting point temperature decreases with an increase in the added amount, and the heat resistance becomes poor. become worse. It is preferable that the metal sintered body of the present invention contains Si because the oxidation resistance is improved. If the content of Si is less than 0.05% by weight, there is no effect of addition, while
Exceeds 5% by weight, the sintered body becomes brittle.

Further, the metal sintered body of the present invention may be made of Hf, Z
It is preferable to contain at least one element selected from the group consisting of r, Y, Nd, Ce and La in an amount of 0.05 to 2.5% by weight. This is because when these elements are included, the adhesion of the oxide film is improved, and the sulfate corrosion resistance is also improved. Particularly, Y is preferable since it has an effect of improving oxidation resistance. When the metal sintered body of the present invention is made of Y ₂ O ₃ , Hf
O ₂ , TiO ₂ , ZrO ₂ , SiO ₂ , Nd ₂ O ₃ , CeO ₂
And La ₂ O ₃ are preferable because they improve oxidation resistance and thermal shock resistance. These oxides can be added as oxide powders when mixing the raw material powders. If the amount of these oxides is less than 0.1% by weight, there is no effect, and if it exceeds 2.5% by weight, sintering of the powder is inhibited, and a dense sintered body cannot be obtained, which is not preferable.

Of these oxides, the addition of Y ₂ O ₃
The effect of forming a high-quality oxide film is large as compared with the addition of other oxides, which is preferable. Further, as compared with the case where Y is added as a metal, the cost of alloying can be reduced, which is preferable in terms of cost. In the present invention, impurities such as Mn, W, M
As long as o does not adversely affect the properties of the sintered body, it does not prevent a small amount from being contained. In the sintered body of the present invention, the content of each of carbon C and nitrogen N is preferably 1% by weight or less, and the content of oxygen O is preferably 3% by weight or less. The sintered body of the present invention is heat-resistant, and even when heated in air at 1050 ° C. or 1150 ° C. for 100 hours, the weight increases,
It is preferably at most 2.0 mg / cm ^2, more preferably at most 1.5 mg / cm ² .

Next, a method for producing a sintered body according to the present invention will be described. The metal powder and / or the metal alloy powder are mixed so that the sintered body has the desired composition ratio described above. Oxide powder may also be mixed at this point. Starting metal powder is Fe powder, N
i powder, Cr powder, Al powder, and additive metal powder. Metal components are pure metals, alloys with one or more other metals,
Alternatively, it may be either an alloy partially and a pure metal partially. Usually, iron is added as iron powder, and Ni is added as Ni powder. Chromium can be added as chromium powder, alloy powder with aluminum, alloy powder with Ni, or alloy powder with iron, but chromium-aluminum alloy powder is preferable. For stability, aluminum is supplied as an alloy powder with iron, an alloy powder with chromium, or an alloy powder with iron and chromium. An alloy powder often used to obtain a mixture that becomes a sintered body having the composition of the present invention is Fe-Ni-Cr-Al-.
(Y, Nd, Ce, La, Zr, Hf) alloy powder, Fe-
Al- (Y, Nd, Ce, La, Zr, Hf) alloy powder,
Cr-Al- (Y, Nd, Ce, La, Zr, Hf) alloy powder, Fe-B powder, Fe-Si powder, Fe-Ti powder and the like. The metal powder may be produced by any method such as a carbonyl method, an electrolytic method, a reduction method, a pulverizing method, and an atomizing method.

Although the particle size of the raw material powder depends on the thickness of the honeycomb body wall, the present invention is not limited to such. The wall thickness is 1 at 62 cells / cm ² (400 cells / in ² )
In a honeycomb body sintered to be 00 μm, the particle size is typically about 44 μm or less. 47 cells / cm ² (3
In the case of a honeycomb body sintered at 00 cells / in ² ) so as to have a wall thickness of 200 μm, the particle size is 53 μm or less. A honeycomb body sintered at 31 cells / cm ² (200 cells / in ² ) so as to have a wall thickness of 300 μm has a particle size of 74 μm or less. Next, the above-mentioned metal powder is mixed, and in some cases, the metal powder and the oxide are mixed to obtain a relatively homogeneous mixture. Typically, a mixture is obtained by dry mixing.
Next, this mixture is formed into a molded body. Press molding, injection molding, extrusion molding, etc., can be formed into a composition of this type by any existing method. The molded body thus obtained is preferably in a honeycomb shape. The honeycomb formed body is preferably formed by extrusion. Depending on the molding method, a binder, a molding aid, and a medium can be added as necessary. A water-insoluble binder such as an acrylic resin or a silicone resin to which polyvinyl alcohol is added preferably uses diacetone as a medium. In injection molding, it is preferable to use stearic acid, glycerin, or the like as a lubricant for paraffin, wax, or the like.

Organic binders such as methylcellulose, polyvinyl alcohol and the like, media and, if appropriate, auxiliary agents such as antioxidants are added to the above mixture to obtain a relatively homogeneous wet mixture. Typically, the binder and, if used, auxiliaries are also added to the mixture to obtain a dry mixture,
Next, a medium is added to obtain a wet mixture. Examples of combinations of binders and media include methyl cellulose and water, respectively. In the case of this combination, it is preferable to add an organic acid such as oleic acid as an antioxidant for the metal powder. An example of a combination of a binder / auxiliary / medium has a composition of 4 g of methylcellulose, 1 g of oleic acid, and 11 g to 12 g of water per 100 g of the mixture. This mixture is formed into a molded body by extrusion molding. A compact means a metal body that has been shaped but not yet sintered. Next, the molded body thus obtained is placed under a non-oxidizing atmosphere, preferably under an atmosphere containing hydrogen.
Sintering is performed at a sufficient temperature and for a sufficient time to obtain a sintered body having a porosity of 5% or less. The preferred atmosphere for sintering is hydrogen. During sintering, it is preferable to surround and surround the compact in close or close contact with a sintering jig. Sintering temperature is 1
It is preferably from 000 to 1400 ° C. In general,
When the sintering temperature is lower than 1000 ° C., sintering is not performed, and when the sintering temperature is higher than 1400 ° C., the obtained sintered body is undesirably deformed and costs increase.

Temperature, size of the compact, design of the device,
The sintering time is affected by the furnace atmosphere and the like. The sintering temperature is appropriately determined so that the porosity, C, N, and O fall within the above-mentioned preferred ranges. The sintering time is usually around 2 hours. In a preferred embodiment, the sintered body obtained after sintering is heat-treated in an oxidizing atmosphere for a time and at a temperature and at a desired rate sufficient to form an oxide film on the surface. Typically, this oxide coating is aluminum oxide. An oxide film is formed on the entire surface including the open pores of the sintered body and the surface of the structure. By appropriately adjusting the temperature and time of the heat treatment, a relatively uniform oxide film can cover the entire surface. Typical atmospheres include air, humid atmosphere, wet hydrogen, carbon dioxide, a mixture of oxidizing and inert gases at various dew points, but the most suitable atmosphere is air. Inside.

The heat treatment temperature is 700 ° C. to 1200 ° C.
Is preferable, and among them, 1000 ° C to 1200 ° C is more preferable. Factors such as temperature, size of the sintered body, equipment design, furnace atmosphere, etc., affect the heat treatment time, with typical heat treatment times ranging from one minute to several hours. Oxidation resistance of the metal sintered body is improved by the safe formation of the oxide film, and the catalyst can be easily carried on the sintered body. In compositions containing yttrium oxide, yttrium oxide slows the rate of oxide film formation, i.e., the rate at which the scale thickens, resulting in a thinner protective oxide film. This oxide coating protects the metal surface when the sintered metal is exposed to high temperatures and corrosive environments. The sintered body as described above is suitable for applications exposed to an oxidizing atmosphere at a high temperature, and includes a catalyst carrier for exhaust gas purification and the like, a heater, for example, a catalyst heater, a catalytic converter, and the like. The preferred shape for these applications is a honeycomb structure, but an extruded honeycomb structure is particularly preferred.

Although the composition of the sintered body is as described above, a specific composition can be selected depending on the application and desired characteristics. When the sintered body is used as a catalyst carrier, a catalyst composition such as a three-way catalyst is supported on the sintered body. The sintered body supported by the catalyst composition as described above can be suitably used as a monolith catalyst element for purifying automobile exhaust gas. The heat-resistant metal sintered body is particularly suitable for such applications because it has excellent durability. In order to use a sintered body as a catalyst carrier, it is preferable that the geometrical surface area of the sintered body is large, and a honeycomb structure is particularly preferable. For this type of application, the cell density is 0.9-341 cells / cm ² (6-2200 cells / i
n ² ). The partition wall thickness is preferably 50 to 2000 μm. The cell shape of the honeycomb structure can take any shape such as a circle, a polygon, and a corrugated shape, but a shape that can relieve thermal stress such as a hexagon is preferable.

Although not limited, the catalyst composition suitable for the sintered body of the present invention includes a catalytically active substance having a catalytic activity of a noble metal such as Pt, Pd or Rh, and an alumina, cerium oxide, zeolite or the like. And a substance supporting the catalytically active substance. Since the sintered body of the present invention has high resistance to oxidation and corrosion, for example, when the sintered body comes into contact with an acidic solution of a noble metal salt when carrying a catalytically active substance, or in applications where the temperature fluctuates, It can be suitably used for applications exposed to exhaust gas. The sintered body of the present invention can be used as a heater having a heating means for heating to a desired temperature. In addition to consumer heaters such as electric hot air heaters, it can be used for industrial heaters, especially for exhaust gas purification of automobiles. In the latter application, it can be used as a heater provided with a catalytic element such as a three-way catalyst.

For effective purification of automobile exhaust pollutants,
The sintered body needs to be heated rapidly, preferably within 20 seconds, to the activation temperature of the catalyst. The activation temperature of the catalyst composition is, for example, 150 ° C. or higher, but is typically 300 ° C.
That is all. The honeycomb shape is suitable as a heater, but is particularly suitable for purifying automobile exhaust gas. Providing electrodes on the sintered body as a means for applying a current to generate heat, and providing a resistance adjusting mechanism such as a slit between the electrodes can control the heat generation and locally or globally according to various applications. It is possible to raise the temperature, which is preferable. The sintered body of the present invention provided with the above-mentioned heater, preferably also provided with an electrode and a resistance adjusting mechanism, can be used as a catalytic converter. For example, the above-described heater with a catalyst, such as a three-way catalyst, can be used as a catalytic converter. Alternatively, the heater can be used as part of a catalytic converter system, with or without the loading of the catalyst composition. For example, a heater is provided upstream of the main monolith catalyst as one type of catalytic converter. If at least one heater carries the catalyst composition, one or more heaters can be provided in line with the main monolith catalyst. For example,
As one type of catalytic converter, a honeycomb heater carrying a catalyst composition on a partition wall surface of a through-hole is provided upstream of a main monolith catalyst element. As another type of catalytic converter, the heater of the present invention is provided downstream of the main monolith catalyst, in which the catalyst composition is carried on the surface of the partition wall of the through-hole.

As the resistance adjusting mechanism provided in the honeycomb heater, for example, slits are provided in various directions, positions, and lengths, the partition wall length in the axial direction of the through hole is changed, and the thickness of the partition wall of the honeycomb structure ( It is preferable to change the wall thickness), change the cell density of the through-holes, and provide slits in the ribs of the honeycomb structure. The metal honeycomb structure thus obtained is usually provided with electrodes by means of brazing, welding, or the like on the outer peripheral wall or inside thereof, whereby a resistance-adjustable honeycomb heater is manufactured. The resistance-adjusting honeycomb heater is preferably formed so that the resistance value as a whole is in the range of 0.001Ω to 0.5Ω.

Further, by supporting a catalyst such as a three-way catalyst on the surface of the resistance-adjusting type honeycomb heater, a rise in temperature due to a purification reaction of exhaust gas (oxidation reaction heat or the like) can be expected, which is preferable. As an example of the catalyst composition supported on the surface of the honeycomb heater, a three-way catalyst comprising a carrier having a large surface area and a catalytically active substance supported on the carrier is exemplified. Here, as the carrier having a large surface area, for example, Al ₂ O ₃ system, TiO ₂ system, SiO _2-
Al ₂ O ₃ , zeolite and perovskite are typical examples. Examples of the catalytically active substance include noble metals such as Pt, Pd, and Rh, Cu, Ni,
Base metals such as Cr and Co, and oxides and sulfides of these metals can be mentioned. Further, a rare earth compound such as La or Ce having an oxygen storage ability can be added. Of the above, it is preferable that the Al ₂ O ₃ system contains La or Ce in an amount of from 2 to 35% by weight in terms of oxide, and carries at least one noble metal at 10 to 100 g / ft ³ .

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. (Example 1) Pure Fe powder, pure Ni powder, pure Cr powder, pure Al powder, Fe-50 wt% Al alloy powder, Fe-20 wt% B alloy powder, Fe-75 wt% Si alloy having a diameter of 44 μm or less Powder, Fe-45% Ti alloy powder, Cr-4
5 wt% Al-5 wt% Hf alloy powder, Cr-45 wt% Al-5 wt% Zr alloy powder, Cr-45 wt% Al
-5 wt% Y alloy powder, Cr-45 wt% Al-5 wt% Nd alloy powder, Cr-45 wt% Al-5 wt% Ce
Alloy powder, Cr-45 wt% Al-5 wt% La alloy powder, TiO ₂ powder, SiO ₂ powder, ZrO ₂ powder, HfO ₂
Powder, Y ₂ O ₃ powder, La ₂ O ₃ powder, CeO ₂ powder and N
d ₂ O ₃ powder was prepared to have the composition shown in Table 1, and 5% by weight of methylcellulose was added and mixed as an organic binder, and 2% of oleic acid was further added as a lubricant and an antioxidant of the metal powder. %, Water was added and mixed at 20% by weight. After degassing the obtained mixture with a kneader,
Through the extrusion mold, diameter 100mm, length 40mm,
A columnar honeycomb structure having a partition wall thickness of 100 μm and a cell number of 62 cells / cm ² was formed. Next, after drying this honeycomb structure, in a hydrogen atmosphere in a molybdenum case,
Sintering was performed at 1200 ° C to 1350 ° C for 4 hours.

Various characteristic values of the thus obtained metal sintered body having the shape of the honeycomb structure were measured by the following methods. [Porosity] Measured by Archimedes' method. [Oxidation test]: The honeycomb structure was held at 1050 ° C. or 1150 ° C. in the air for 100 hours, and the weight increased by the holding was divided by the geometric surface area of the honeycomb structure.
I took the quotient. After the oxidation test, the presence or absence of oxide film peeling was visually checked. [Hydrochloric acid solution corrosion test] A 20 mm square honeycomb structure was immersed in a 0.1 N hydrochloric acid solution for 1 hour, washed with water and dried, and the weight loss was divided by the geometric surface area of the honeycomb structure to obtain a quotient. [Heat shock test] Using a rectangular parallelepiped honeycomb structure (length: 70 mm, width: 10 mm, height: 50 mm) in which the through-hole extends in the height direction and the opening of the through-hole has upper and lower end surfaces, 1000 ° C. A temperature cycle of repeatedly changing the temperature between and 100 ° C. was performed 200 times, and it was measured how much the length of the upper end face of the honeycomb structure contracted.

[Bending Strength Test] A test piece was cut out so that the length of a parallel portion parallel to the axial direction of the through hole was 50 mm, and the cross section was 3 cells. Was measured. At the time of bending strength measurement, the distance traveled by the crosshead before the test piece was broken was measured as the amount of deflection. Similarly, the kneaded clay degassed by a vacuum kneader was extruded into a plate having a thickness of 5 mm, sintered under the above conditions, and the following characteristics were measured.

[Tensile strength test] The test piece had a parallel part length of 25 mm in a direction parallel to the axial direction of the through hole and a cross section of 2 × 6.
mm, and cut into JIS G0567 (197
The tensile strength was determined at 1000 ° C. according to the tensile method specified in 8). [Sulfate Corrosion Test] An aqueous solution in which NaCl and Na ₂ SO ₄ were mixed at a weight ratio of 5: 5 was prepared, and the aqueous solution was applied to one side of the test piece such that 5 mg of these salts adhered to 1 cm ² of the surface of the test piece. Was applied. The test piece was placed in a crucible and kept at 850 ° C. in the atmosphere for 100 hours. After that, wash with water,
The weight change of the test piece was determined and divided by the initial surface area to obtain a quotient. Based on this value, the sulfate corrosion resistance indicating the corrosion resistance due to the sulfate was evaluated, and the smaller the value, the better. Tables 1 to 6 show these results.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

[Table 5]

[0041]

[Table 6]

Experiment Nos. In Tables 1, 4, 5, and 6 1 to 1
1, No. 30 to 45 and No. 3; Reference numeral 59 denotes an alloy composition using nickel as a base.
o. 12 to 29 and No. 12; 46-57, the iron Ri alloy composition der that the substrate is a reference example. No. 58 and 59 are reference examples. Experiment No. 4 and Experiment No. Comparison with No. 59 shows that when the iron content is less than 5% by weight, the corrosion resistance to sulfate decreases. Experiment No. 15 and Experiment No. It can be seen from the comparison of No. 58 that the inclusion of nickel improves the tensile strength at 1000 ° C. and the thermal shock resistance. Experiment No. The oxidation tests 3, 6, and 5 show that when the content of Cr is small, the oxidation resistance is inferior, and as the content of Cr increases, the oxidation resistance improves. If there is much Al, it will become brittle.

The sintered body to which B is added becomes dense, and accordingly, the oxidation resistance and the mechanical strength are improved. Improvements in oxidation resistance and mechanical strength were determined in Experiment Nos. 1 and No. 1 It is clear from the comparison of FIG. However, when the B content is excessive, the oxidation resistance deteriorates. Experiment No. 30 and Experiment No.
As is clear from comparison with 31 to 34, when Ti is contained, the bending strength, which is the strength measured at room temperature, and the tensile strength measured at 1000 ° C. of the sintered body are improved. But,
As the content of Ti increases, the sintered body becomes brittle and the oxidation resistance deteriorates.

Experiment No. 30 and Experiment No. As is clear from the comparison with 35 to 37, when Si is contained, the oxidation resistance is improved. Experiment No. 30 and Experiment No. 38-43
As is clear from the comparison with Hf, Zr, Y, Nd,
When any one of Ce and La is contained, the thermal shock resistance and the oxidation resistance tend to be improved. Experiment No.
2 and No. As is clear from the comparison of No. ₃ , the addition of Y ₂ O ₃ improves the oxidation resistance and the thermal shock resistance. However, it becomes brittle as the amount of addition increases. Experiment No. Experiment No. 46 or 47 and Experiment No. As is clear from the comparison with 49 to 55, H
fO ₂ , TiO ₂ , ZrO ₂ , SiO ₂ , Nd ₂ O ₃ , CeO
_When any one of La ₂ and La ₂ O ₃ is contained, the oxidation resistance and / or thermal shock resistance are improved as in the case where Y ₂ O ₃ is contained.

(Example 2) A honeycomb structure having an outer diameter of 90 mm, a thickness of 25 mm, a cell partition wall thickness of 100 μm, and a cell density of 62 cells / cm ² (400 cells / in ² ) was manufactured using the same composition as in Example 1 by the same process as in Example 1. Heater with slit (resistance controlled honeycomb heater)
Was prepared. Here, as shown in FIG. 1, two slits were formed on the outer wall 10 of the honeycomb structure, and then a slit 12 having a length of 70 mm was formed at six locations in the axial direction of the through hole. (The slit length at both ends is 50m
m) and the number of cells between the slits 12 is 7 (about 10 mm)
It formed so that it might become. Next, commercially available γ-Al ₂ O ₃
(BET surface area: 300 m ² / g) 75% by weight, and a slurry formed by adding an appropriate amount of acetic acid so that cerium powder and CeO ₂ powder become 25% by weight in terms of CeO ₂ by using a slurry obtained above. The surface of the through hole of the honeycomb heater was coated with about 50 μm, and the coating layer was dried and fired at 550 ° C. Next, the honeycomb heater is impregnated with an aqueous solution containing Pt and Rh, and a noble metal is supported on the γ-Al ₂ O ₃ .CeO ₂ composite oxide layer. Finally, the Pt: Rh ratio is 5: 1. A honeycomb heater carrying the catalyst composition carrying 45 g / ft ³ was obtained.

In the exhaust gas system of an automobile having a displacement of 2000 cc, a commercially available three-way catalyst having a diameter of 3.66 inches and a volume of 1.3 liters corresponding to the main monolith catalyst is arranged. That is, a honeycomb heater supporting the catalyst composition was installed as a preheater on the upstream side of the exhaust gas. Then, the catalytic converter in the FTP of the catalytic converter including the honeycomb heater and the three-way catalyst was measured. Table 8 shows the results. Here, the supply voltage to the pre-heater was 12 V, the energization was started when the engine was started, and the energization was stopped after 40 seconds. Therefore, the unheated exhaust gas immediately after the start of the engine is preliminarily heated by the catalyst-equipped honeycomb heater and then further purified by the three-way catalyst. Also, for 40 seconds after starting the engine,
Secondary air was supplied at 00 l / min. As a reference example, Table 7 also shows the results obtained when exhaust gas was treated using only a three-way catalyst.

[0047]

[Table 7]

(Example 3) Next, in order to examine the durability of the honeycomb heater, Experiment No. 3 was performed. A honeycomb heater having a honeycomb structure having an alloy composition of No. 44 and manufactured in the same manner as in Example 2; A rapid durability thermal cycle test using engine exhaust gas was performed on a honeycomb heater provided with 58 honeycomb structures having an alloy composition outside the range of the present invention. A thermal cycle test was performed in which the outlet temperature of the honeycomb heater was changed back and forth between 600 ° C. and 900 ° C., and this cycle was repeated 5,000 times. The honeycomb heater having a composition outside the range of the invention was deformed and some cells were broken. The honeycomb heater having the composition of 44 has a small deformation,
There was no problem in practical use. Although the present invention has been described in detail with reference to specific embodiments, it is apparent that the present invention is not limited to these embodiments.

[0049]

As described above, according to the present invention,
A metal sintered body having excellent thermal shock resistance, high-temperature oxidation resistance, and corrosion resistance, and a method for producing the same can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a honeycomb heater with slits according to the present invention.

[Explanation of symbols]

10 ... outer wall, 11 ... electrode, 12 ... slit, 13 ...
The outer periphery

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI C22C 19/05 C22C 19/05 Z (72) Inventor Nobuo Tsuno 2-56 Sudacho, Mizuho-ku, Nagoya-shi, Aichi Nippon Insulators Co., Ltd. (56) References JP-A-4-308004 (JP, A) JP-A-4-215853 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00 304 B22F 3/10 B22F 3/11 C22C 1/04 C22C 1/05 C22C 19/05

Claims (18)

(57) [Claims] (1) 5 to 40% by weight of Cr and 2 to 30% of Al
% Of Fe and 5 to 15% by weight of Fe .
005-0.1% by weight of B, 0.05-5% by weight of Ti
And / or Si, and Zr, Hf, group 3A and run
At least one selected from the group consisting of tanoid elements
A metal sintered body containing 0.05 to 2.5% by weight of a metal, with the balance being Ni and inevitable impurities. 2. In addition to the components of claim 1, SiO _2, 3
At least one oxide selected from the group consisting of group A oxides, lanthanoid oxides and group 4A oxides,
2. The metal sintered body according to claim 1, wherein the content is 2.5% by weight. 3. The metal sintered body according to claim 2 , wherein the oxide is Y ₂ O ₃ . 4. A sintered metal according to any one of claims 1 to 3, characterized in that it contains Ni 5% by weight or more. 5. The metal sintered body according to claim 4 , comprising 10 to 30% by weight of Ni. 6. A sintered metal according to any one of claims 1 to 5, characterized in that it contains Cr 10 to 30% by weight. 7. A sintered metal according to any one of claims 1 to 6, characterized in that it contains Al 5 to 15 wt%. 8. The metal sintered body according to claim 7 , comprising 8 to 15% by weight of Al. 9. The method of claim 1 and consists of a metal sintered body according to any one of 8, the honeycomb structure characterized by having a number of through holes. 10. The honeycomb structure according to claim 9 , wherein the honeycomb structure is formed by extruding a powdery raw material into a honeycomb shape and sintering. 11. sintered metal according to any one of claims 1 to 8, characterized in that supporting a catalyst composition. 12. The method of claim 1 using a metal sintered body according to any one of 8 as a catalyst carrier, an automobile exhaust gas purifying monolithic catalyst in which the catalyst composition onto the catalyst support is characterized in that it is carried . 13. thermostable heater characterized by having a metal sintered body according to any one of claims 1-8, and heating means for heating the metal sintered body. 14. A metal sintered body according to any one of claims 1 to 8 carrying a catalyst composition, heat resistance and having a heating means for heating the metal sintered body heater. 15. A main monolithic catalyst, and a heater having a heating means for heating the metal sintered body and the metal sintered body according to any one of claims 1-8, main monolithic catalyst A catalytic converter, wherein the heater is arranged on the upstream side and / or downstream side of the catalyst. 16. A main monolithic catalyst, and at least one heater has a heating means for heating the metal sintered body and the metal sintered body according to any one of claims 1-8, wherein A catalytic converter, wherein a catalyst composition is supported on at least one of the heaters, and the heater is disposed on the upstream and / or downstream side of the main monolith catalyst. A metal sintered body according to any one of claims 17] claims 1-8, the catalyst composition supported on the metal sintered body, and heating means for heating the metal sintered body A catalytic converter comprising: 18. A) a metal powder and an oxide powder are mixed to obtain the alloy composition according to claim 1 or 2 to obtain a mixed powder, and b) the mixed powder is formed into a molded body, c. A) a method for producing a metal sintered body, comprising sintering the molded body in a non-oxidizing atmosphere at a temperature and for a time sufficient to produce the metal sintered body.