Title of Invention	"METAL CARRIER FOR A CATALYST"
Abstract	[object] Provided is a metal carrier for a catalyst having a cylindrical case having an excellent high temperature oxidation resistance. [Solving means] A metal carrier 2 for a catalyst has a honeycomb structure 5 which is in a cylindrical form and has plural air vents 4 extending in its axial direction, and a cylindrical case 6 covering the periphery of the honeycomb structure 5. The cylindrical case 6 is made of ferritic stainless steel containing Mo. This makes it possible to avoid occurrence of abnormal oxidation of the cylindrical case 6 at high temperature.

Title of Invention

"METAL CARRIER FOR A CATALYST"

Abstract

[object] Provided is a metal carrier for a catalyst having a cylindrical case having an excellent high temperature oxidation resistance. [Solving means] A metal carrier 2 for a catalyst has a honeycomb structure 5 which is in a cylindrical form and has plural air vents 4 extending in its axial direction, and a cylindrical case 6 covering the periphery of the honeycomb structure 5. The cylindrical case 6 is made of ferritic stainless steel containing Mo. This makes it possible to avoid occurrence of abnormal oxidation of the cylindrical case 6 at high temperature.

Full Text	The present invention relates to a metal carrier for a catalyst, and more particularly to improvement in a metal carrier for a catalyst comprising a honeycomb structure which is in a cylindrical form and has plural air vents extending in its axial direction, and a cylindrical case covering the periphery of the honeycomb structure. [Prior art] Such a type of metal carrier is fitted to an exhausting system of a vehicle in a state that a catalyst for cleaning exhaust gas is carried on its honeycomb structure. [Problems to be solved by the invention] For example, in motorcycles, particularly motorcycles on which a small-sized 2-cycle engine is mounted, the metal carrier is fitted to the inside of a muffler, because of a restriction of arrangement thereof and the like, in such a manner that an opening portion at one end of its case is welded to the outlet of the exhaust pipe. For this reason, the metal carrier is exposed to a high temperature of, for example, 900 °C or higher. In this case, the honeycomb structure is covered with a catalyst layer and thus oxidation thereof does not come into ques t ion very much . However, the periphery of the case is exposed and, in consequence, oxidation thereof rapidly advances when the case is exposed to high temperature. In other words, abnormal oxidation may be introduced. [Means for solving the problems] An object of the present invention is to provide a metal carrier for a catalyst, in which high temperature oxidation resistance of its case is greatly improved. According to the present invention, in order to attain the object, provided is a metal carrier for a catalyst comprising a honeycomb structure which is in a cylindrical form and has plural air vents extending in its axial direction, and a cylindrical case covering the periphery of the honeycomb structure, wherein the cylindrical case is composed of ferritic ..Stainless steel containing Mo. [0007] Specifying the material of the case as above causes high temperature oxidation resistance of the case to be greatly improved, and makes it possible to avoid abnormal oxidation thereof. Accordingly, the present invention relates to a metal carrier for a catalyst comprising: a honeycomb structure made of ferritic stainless steel and shaped in a cylindrical form, said honeycomb structure having a plurality of air vents, the honeycomb structure having alternating waved plates and base plates, the waved plates having first sections, and each of the base plates having an inner and an outer surface being disposed against the first sections of adjoining ones of the waved plates located inwardly and outwardly thereof, respectively, and the waved plates also having second sections extending outwardly from one of the base plates to the base plate immediately adjacent thereto, wherein the second sections of the waved plates are planar surfaces extending an axial direction from one end of the metal carrier to another, thus forming the air vents as passages from one end of the metal carrier to the other end; a cylindrical case covering an outer peripheral surface of the honeycomb structure, wherein the cylindrical case is composed of ferritic stainless steel having Mo and phosphorous, said Mo content in the ferritic stainless steel is in the range of 0.30 wt% [Brief Explanation of the Drawings] [Figure 1] This is a perspective view of a cleaner for exhaust gas . [Figure 2] This is an enlarged cross sectional view of an important portion in Fig. 1. [Figure 3] This is a graph showing an example of the relationship between heating temperature and oxidation increase. [Figure 4] This is a graph showing another example of the relationship between heating temperature and oxidation increase. [Figure 5] This is a cross sectional view of an important portion showing arrangement relationship among an exhaust pipe, a muffler and a cleaner. [Embodiments of the invention] In Figs. 1 and 2, a cleaner 1 for exhaust gas fitted to an exhausting system of a motorcycle is composed of a metal carrier 2 for a catalyst and a catalyst layer 3 carried thereon. The metal carrier 2 Has a honeycomb structure 5 which is in a cylindrical form and has plural air vents 4 extending in its axial direction, and a cylindrical case 6 covering the periphery of the honeycomb structure 5. In this embodiment, the plural air vents 4 existing at the outermost position of the honeycomb structure 5 are formed by cooperation of the inner face of the case 6 and a waved plate 7 of the honeycomb structure 5. The catalyst layer 3 is carried after sintering treatment of the inner face of the respective air vents 4 . The waved plates 7 and base plates 8 of the honeycomb structure 5 are made of ferritic stainless steel, for example, widely-used ferritic stainless steel containing no Mo. The case 6 is composed of a seam welded pipe comprising ferritic stainless steel containing Mo. The Mo content in this ferritic stainless steel is preferably set into the range of 0.30 wt %^Mo^2.50 wt %. Specifying the material of the case 6 as above causes great improvement in high temperature oxidation resistance of the case 6 and makes it possible to avoid abnormal oxidation thereof. Besides, since the material of the case 6 is the same as that of the honeycomb structure 5, difference in coefficient of linear expansion between them is small, thereby suppressing greatly thermal deformation of the case 6 based on the difference. In addition, when the case 6 is welded to the outlet of the exhaust pipe, weldability thereof becomes better. Concerning the Mo content, in the case of Mo 2 . 50 wt%, the Mo content is remarkably larger than ordinary standardized materials, thereby raising material cost. Thus, such a material is unsuitable for a constituting material of the cases for mass production. The following will explain high temperature oxidation resistance of the material constituting the case 6, and practical vehicle endurance tests. [1] High temperature oxidation resistance Table 1 shows compositions of Examples 1 - 3 of ferritic stainless steel. (Table Removed) In Examples 1-3, test pieces having a thickness of 1.0 mm and the same surface area were produced, and then these test pieces were set inside a heating furnace in the atmosperic pressure. Heating temperature was then raised to a predetermined value, and the raised temperature was kept for 20 hours. Subsequently, oxidation increase (wt %) of the respective test pieces was obtained. This measuring operation was repeated given times. Figure 3 shows results of the measurement. In this figure, Examples 1-3 corresponds to Examples 1 - 3 in Table 1, respectively. As shown in Fig. 3, when the heating temperature was over about 800 °C, oxidation in Examples 1 -3 started. However, in case of Example 1, which contained Mo, its oxidation increase was merely about 0.57 wt% even at a heating temperature of 1000 °C . This made it clear that Example 1 had an excellent high temperature oxidation resistance. On the other hand, abnormal oxidation arose at a heating temperature of about 900 °C or more in Example 2, and at a temperature of about 950 °C or more in Example 3, respectively. Next, the inside of the furnace was kept into a moisture added atmosphere and then the same measuring operation as above was repeated given times. In this case, the moisture added atmosphere comprised 90 vol % of a mixture gas (0.5 vol % of oxygen and the balance of nitrogen) and 10 vol % of water. Figure 4 shows results of the measurement. In this figure, Examples 1-3 corresponds to Examples 1 - 3 in Table 1, respectively. As shown in Fig. 4, in case of Example 1, which contained Mo, its oxidation increase was about 0.48 wt % at a heating temperature of 950 °C . This made it clear that Example 1 also had an excellent high temperature oxidation resistance in the moisture added atmosphere. On the other hand, abnormal oxidation arose at a heating temperature of about 900 °C or more in Examples 2 and 3 . [II] Practical vehicle endurance test The catalyst layer 3 having a noble metal such as platinum was carried on the metal carrier 2 for a catalyst having the case 6 made of Example 1, to obtain the cleaner 1 of Example 1 . The same catalyst layer 3 as above was carried on 2 kinds of metal carriers 2 for a catalyst which had the case 6 and were made of Examples 2 and 3 to obtain the cleaners 1 of Examples 2 and 3. As shown in Fig. 5, in an exhausting system of a small-sized 2-cycle engine mounted on a motorcycle, an opening portion at one end of the case 6 was welded to the outlet of the exhaust pipe 9 so that the metal carrier 2, that is, the cleaner 1 of Example 1 was set up inside the muffler 10. The engine was then driven for a specified period, and subsequently the state of the case 6 was examined. During the driving of the engine, the temperature inside the muffler 10 at a distance of 20 cm behind the cleaner 1 was about 900 °C . The same test was carried out about the cleaners of Examples 2 and 3. Table 2 shows results of the test. (Table Removed) From Table 2, it can be understood that the case 6 of the cleaner 1 of Example 1 had an excellent high temperature oxidation resistance and good deformation resistance . Thus , exhaust gas cleaning ability of Example 1 is kept for a long time. From Table 2, it is also clear that the cleaners 1 of Examples 2 and 3 were not practical. In particular, the catalyst layer 3 of Example 2 was subjected to EPMA (XMA) analysis. As a result, a portion 3a (see Fig. 2), of the catalyst layer 3, adhering to the inner face of the case 6 was covered with an oxide resulting from abnormal oxidation, and further an Fe component was detected at a portion 3b (see Fig. 2) , of the catalyst layer 3, adhering to the honeycomb structure 5. The exhaust gas cleaning ability of this cleaner 1 of Example 2 was greatly reduced, as compared with its initial value. [Advantageous effect of the invention] According to the present invention, a metal carrier for a catalyst is provided wherein high temperature oxidation resistance of its case is greatly improved by the aforementioned structure. [Explanation of symbols] 2 metal carrier for a catalyst 3 catalyst layer 4 air vent 5 honeycomb structure 6 cylindrical case 1. A metal carrier for a catalyst comprising a honeycomb structure ( 5 ) which is in a cylindrical form and has plural air vents (4) extending in its axial direction, and a cylindrical case (6) covering the periphery of the honeycomb structure (5), characterized in that the cylindrical case (6) is composed of ferritic stainless steel containing Mo . 2- • The metal carrier for a catalyst-feo claim 1, wherein the Mo content in the ferritic stainless steel satisfies 0.30 wt%≤ Mo ≤2.50wt%. 3. A metal carrier for a catalyst substantially as herein described with reference to the accompanying drawings.

Full Text

The present invention relates to a metal carrier for a catalyst, and more particularly to improvement in a metal carrier for a catalyst comprising a honeycomb structure which is in a cylindrical form and has plural air vents extending in its axial direction, and a cylindrical case covering the periphery of the honeycomb structure.
[Prior art]
Such a type of metal carrier is fitted to an exhausting system of a vehicle in a state that a catalyst for cleaning exhaust gas is carried on its honeycomb structure.
[Problems to be solved by the invention] For example, in motorcycles, particularly motorcycles on which a small-sized 2-cycle engine is mounted, the metal carrier is fitted to the inside of a muffler, because of a restriction of arrangement thereof and the like, in such a manner that an opening portion at one end of its case is welded to the outlet of the exhaust pipe. For this reason, the metal carrier is exposed to a high temperature of, for example, 900 °C or higher. In this case, the honeycomb structure is covered with a catalyst layer and thus oxidation thereof does not come into ques t ion very much . However, the periphery of the case is exposed and, in consequence, oxidation thereof rapidly advances when the case is exposed to high temperature. In other words, abnormal oxidation may be introduced. [Means for solving the problems]
An object of the present invention is to provide a metal carrier for a catalyst, in which high temperature oxidation resistance of its case is greatly improved. According to the present invention, in order to attain the object, provided is a metal carrier for a catalyst comprising a honeycomb structure which is in a cylindrical form and has plural air vents extending in its axial direction, and a cylindrical case covering the periphery of the honeycomb structure, wherein the cylindrical case is
composed of ferritic ..Stainless steel containing Mo. [0007]
Specifying the material of the case as above causes high temperature oxidation resistance of the case to be greatly improved, and makes it possible to avoid abnormal oxidation thereof.

Accordingly, the present invention relates to a metal carrier for a catalyst comprising: a honeycomb structure made of ferritic stainless steel and shaped in a cylindrical form, said honeycomb structure having a plurality of air vents, the honeycomb structure having alternating waved plates and base plates, the waved plates having first sections, and each of the base plates having an inner and an outer surface being disposed against the first sections of adjoining ones of the waved plates located inwardly and outwardly thereof, respectively, and the waved plates also having second sections extending outwardly from one of the base plates to the base plate immediately adjacent thereto, wherein the second sections of the waved plates are planar surfaces extending an axial direction from one end of the metal carrier to another, thus forming the air vents as passages from one end of the metal carrier to the other end; a cylindrical case covering an outer peripheral surface of the honeycomb structure, wherein the cylindrical case is composed of ferritic stainless steel having Mo and phosphorous, said Mo content in the ferritic stainless steel is in the range of 0.30 wt% [Brief Explanation of the Drawings]
[Figure 1]
This is a perspective view of a cleaner for exhaust gas .
[Figure 2]
This is an enlarged cross sectional view of an important portion in Fig. 1.
[Figure 3]
This is a graph showing an example of the relationship between heating temperature and oxidation increase.
[Figure 4]
This is a graph showing another example of the relationship between heating temperature and oxidation increase.
[Figure 5]
This is a cross sectional view of an important portion showing arrangement relationship among an exhaust pipe, a muffler and a cleaner.
[Embodiments of the invention]
In Figs. 1 and 2, a cleaner 1 for exhaust gas fitted to an exhausting system of a motorcycle is composed of a metal carrier 2 for a catalyst and a catalyst layer 3 carried thereon. The metal carrier 2 Has a honeycomb structure 5 which is in a cylindrical form and has plural air vents 4 extending in its axial direction, and a cylindrical case 6 covering the periphery of the honeycomb structure 5. In this embodiment, the plural air vents 4 existing at the outermost position of the honeycomb structure 5 are formed by cooperation of the inner face of the case 6 and a waved plate 7 of the honeycomb structure 5. The catalyst layer 3 is carried after sintering treatment of the inner face of the respective air vents 4 .
The waved plates 7 and base plates 8 of the honeycomb structure 5 are made of ferritic stainless steel, for example, widely-used ferritic stainless steel containing no Mo.
The case 6 is composed of a seam welded pipe comprising ferritic stainless steel containing Mo. The Mo content in
this ferritic stainless steel is preferably set into the
range of 0.30 wt %^Mo^2.50 wt %.
Specifying the material of the case 6 as above causes great improvement in high temperature oxidation resistance of the case 6 and makes it possible to avoid abnormal oxidation thereof. Besides, since the material of the case 6 is the same as that of the honeycomb structure 5, difference in coefficient of linear expansion between them is small, thereby suppressing greatly thermal deformation of the case 6 based on the difference. In addition, when the case 6 is welded to the outlet of the exhaust pipe, weldability thereof becomes better.
Concerning the Mo content, in the case of Mo 2 . 50 wt%, the Mo content is remarkably larger than ordinary standardized materials, thereby raising material cost. Thus, such a material is unsuitable for a constituting material of the cases for mass production.
The following will explain high temperature oxidation resistance of the material constituting the case 6, and practical vehicle endurance tests. [1] High temperature oxidation resistance
Table 1 shows compositions of Examples 1 - 3 of ferritic
stainless steel.

(Table Removed)
In Examples 1-3, test pieces having a thickness of 1.0 mm and the same surface area were produced, and then these test pieces were set inside a heating furnace in the atmosperic pressure. Heating temperature was then raised to a predetermined value, and the raised temperature was kept for 20 hours. Subsequently, oxidation increase (wt %) of the respective test pieces was obtained. This measuring operation was repeated given times. Figure 3 shows results of the measurement. In this figure, Examples 1-3 corresponds to Examples 1 - 3 in Table 1, respectively. As shown in Fig. 3, when the heating temperature was over about 800 °C, oxidation in Examples 1 -3 started. However, in case of Example 1, which contained Mo, its oxidation increase was merely about 0.57 wt% even at a heating temperature of 1000 °C . This made it clear that Example 1 had an excellent high temperature oxidation resistance. On the other hand, abnormal oxidation arose at a heating temperature of about 900 °C or more in Example 2, and at a temperature of about 950 °C or more in Example 3, respectively.
Next, the inside of the furnace was kept into a moisture added atmosphere and then the same measuring operation as above was repeated given times. In this case, the moisture added atmosphere comprised 90 vol % of a mixture gas (0.5 vol % of oxygen and the balance of nitrogen) and 10 vol % of water.
Figure 4 shows results of the measurement. In this figure, Examples 1-3 corresponds to Examples 1 - 3 in Table 1, respectively. As shown in Fig. 4, in case of Example 1, which contained Mo, its oxidation increase was about 0.48 wt % at a heating temperature of 950 °C . This made it clear that Example 1 also had an excellent high temperature oxidation resistance in the moisture added atmosphere. On the other hand, abnormal oxidation arose at a heating temperature of about 900 °C or more in Examples 2 and 3 . [II] Practical vehicle endurance test
The catalyst layer 3 having a noble metal such as platinum was carried on the metal carrier 2 for a catalyst having the case 6 made of Example 1, to obtain the cleaner 1 of Example 1 . The same catalyst layer 3 as above was carried on 2 kinds of metal carriers 2 for a catalyst which had the case 6 and were made of Examples 2 and 3 to obtain the cleaners 1 of Examples 2 and 3. As shown in Fig. 5, in an exhausting system of a
small-sized 2-cycle engine mounted on a motorcycle, an opening portion at one end of the case 6 was welded to the outlet of the exhaust pipe 9 so that the metal carrier 2, that is, the cleaner 1 of Example 1 was set up inside the muffler 10. The engine was then driven for a specified period, and subsequently the state of the case 6 was examined. During the driving of the engine, the temperature inside the muffler 10 at a distance of 20 cm behind the cleaner 1 was about 900 °C . The same test was carried out about the cleaners of Examples 2 and 3.
Table 2 shows results of the test.

(Table Removed)
From Table 2, it can be understood that the case 6 of the cleaner 1 of Example 1 had an excellent high temperature oxidation resistance and good deformation resistance . Thus , exhaust gas cleaning ability of Example 1 is kept for a long time.
From Table 2, it is also clear that the cleaners 1 of Examples 2 and 3 were not practical. In particular, the catalyst layer 3 of Example 2 was subjected to EPMA (XMA) analysis. As a result, a portion 3a (see Fig. 2), of the
catalyst layer 3, adhering to the inner face of the case 6 was covered with an oxide resulting from abnormal oxidation, and further an Fe component was detected at a portion 3b (see Fig. 2) , of the catalyst layer 3, adhering to the honeycomb structure 5. The exhaust gas cleaning ability of this cleaner 1 of Example 2 was greatly reduced, as compared with its initial value.
[Advantageous effect of the invention] According to the present invention, a metal carrier for a catalyst is provided wherein high temperature oxidation resistance of its case is greatly improved by the aforementioned structure.
[Explanation of symbols]
2 metal carrier for a catalyst
3 catalyst layer
4 air vent
5 honeycomb structure
6 cylindrical case

1. A metal carrier for a catalyst comprising a honeycomb structure ( 5 ) which is in a cylindrical form and has plural air vents (4) extending in its axial direction, and a cylindrical case (6) covering the periphery of the honeycomb structure (5), characterized in that the cylindrical case (6) is composed of ferritic stainless steel containing Mo .
2- • The metal carrier for a catalyst-feo claim 1, wherein the Mo content in the ferritic stainless steel satisfies 0.30 wt%≤ Mo ≤2.50wt%.
3. A metal carrier for a catalyst substantially as herein described with reference to the accompanying drawings.

Documents:

3684-del-1998-abstract.pdf

3684-del-1998-claims.pdf

3684-del-1998-correspondence-others.pdf

3684-del-1998-correspondence-po.pdf

3684-del-1998-description (complete).pdf

3684-del-1998-drawings.pdf

3684-del-1998-form-1.pdf

3684-del-1998-form-13.pdf

3684-del-1998-form-19.pdf

3684-del-1998-form-2.pdf

3684-del-1998-form-3.pdf

3684-del-1998-form-4.pdf

3684-del-1998-form-6.pdf

3684-del-1998-gpa.pdf

3684-del-1998-petition-137.pdf

3684-del-1998-petition-138.pdf

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Patent Number

215396

Indian Patent Application Number

3684/DEL/1998

PG Journal Number

11/2008

Publication Date

14-Mar-2008

Grant Date

26-Feb-2008

Date of Filing

08-Dec-1998

Name of Patentee

HONDA GIKEN KOGYO KABUSHIKI KAISHA

Applicant Address

1-1, MINAMIAOYAMA 2-CHOME, MINATO-KU, TOKYO, JAPAN

Inventors:

#	Inventor's Name	Inventor's Address
1	MASAHARU NAKAMORI	C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, OF 4-1 CHUO 1-CHOME, WAKO-SHI, SAITAMA, JAPAN
2	KATSUNORI OKUBO	C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, OF 4-1 CHUO 1-CHOME, WAKO-SHI, SAITAMA, JAPAN
3	MASASHI YOKOYAMA	C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, OF 4-1 CHUO 1-CHOME, WAKO-SHI, SAITAMA, JAPAN
4	HIROSHI KATO	C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, OF 4-1 CHUO 1-CHOME, WAKO-SHI, SAITAMA, JAPAN

PCT International Classification Number

B01D 53/74

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	HEI-10-002302	1998-01-08	Japan