WO2012093697A1

WO2012093697A1 - Exhaust pipe and exhaust pipe manufacturing method

Info

Publication number: WO2012093697A1
Application number: PCT/JP2012/050106
Authority: WO
Inventors: 史幸陸田; 祐生藤田
Original assignee: イビデン株式会社
Priority date: 2011-01-06
Filing date: 2012-01-05
Publication date: 2012-07-12
Also published as: DE112012000415T5

Abstract

Disclosed is an exhaust pipe comprising a metallic substrate and, formed on the surface of thereof, a surface coating layer containing an inorganic amorphous material. The surface coating layer is porous and, if the surface coating layer in an electron microscope image at 500x magnification of a cross section parallel to the thickness direction of the exhaust pipe is cut in the direction perpendicular to said exhaust pipe thickness direction into five rectangular sections that have 1/5 the thickness of the surface coating layer after said cut, there is at least one pore-concentrated section which is a rectangular section having pores making up 30% or more of the pore area of the entire surface coating layer. The pore-concentrated section comprises the central section of the five rectangular sections, or one or two of the rectangular sections adjacent to said central rectangular section. The pores present in the aforementioned surface coating layer include closed pores, but said closed pores do not connect the outside of the exhaust pipe and the surface of the aforementioned substrate.

Description

Exhaust pipe and method of manufacturing exhaust pipe

The present invention relates to an exhaust pipe and an exhaust pipe manufacturing method.

In order to treat harmful substances such as harmful gases contained in the exhaust gas discharged from the engine, a catalytic converter is provided in the path of the exhaust pipe.
In order to increase the purification efficiency of harmful substances by the catalytic converter, it is necessary to maintain the temperature of exhaust gas and the exhaust pipe through which the exhaust gas circulates at a temperature suitable for catalyst activation (hereinafter also referred to as catalyst activation temperature). .
However, during high-speed operation of the engine, the exhaust gas temperature may temporarily become a high temperature exceeding 1000 ° C., which may deviate from the upper limit value of the catalyst activation temperature. As a result, there are problems that it becomes difficult to efficiently purify the exhaust gas and that the catalyst deteriorates.

Therefore, for example, the exhaust pipe connected to the automobile engine is required to be able to radiate the heat of the exhaust gas passing through the exhaust pipe to the outside during the high-speed operation of the automobile engine.

Therefore, for example, Patent Document 1 discloses an exhaust pipe in which a surface coating layer made of a crystalline inorganic material and an amorphous inorganic material is formed on the outer peripheral surface of a cylindrical base material made of metal. Yes.
In the conventional exhaust pipe described in Patent Document 1, the average thickness of the amorphous inorganic material located on the outer peripheral surface side with respect to the crystalline inorganic material is 20 μm or less, and it is said that the heat dissipation is excellent.

JP 2009-133214 A

In the conventional exhaust gas purification system, the temperature of the catalytic converter is lower than the catalyst activation temperature when the engine is started. Then, heat is applied to the catalytic converter by the inflow of high-temperature exhaust gas, and the temperature of the catalytic converter reaches the catalyst activation temperature after a predetermined time has elapsed from the start of the engine. In recent years, in order to shorten the time until the temperature of the catalytic converter reaches the catalyst activation temperature, an exhaust gas purification system having a mechanism for directly energizing the catalytic converter to increase the temperature of the catalytic converter has been studied.
Since an electrode may contact or adjoin to the exhaust pipe used in the exhaust gas purification system that directly energizes the catalytic converter, high insulation is required in order to prevent troubles such as electric leakage.

The inventors of the present invention have tried to increase the thickness of the surface coating layer in order to improve insulation in an exhaust pipe having a base material and a surface coating layer used as an exhaust pipe. Although the insulation is improved by increasing the thickness of the surface coating layer, cracks occur in the surface coating layer in an environment where a thermal shock such as a rapid temperature increase or a rapid temperature decrease of 20 ° C./second or more is applied. The problem that the coating layer was destroyed occurred.
The present invention has been made to solve such problems. When used as an exhaust pipe, the present invention can ensure high insulation and can maintain heat resistance at low temperatures and at high temperatures. It aims at providing the exhaust pipe excellent in heat dissipation.

As a result of earnestly examining the method of preventing the destruction of the surface coating layer even when the thickness of the surface coating layer is increased in order to improve the insulating property, The inventors have found that it is possible to prevent the development of cracks and the destruction of the surface coating layer by specifying the positions of the pores present in the present invention, and have arrived at the present invention.

That is, the exhaust pipe according to claim 1 is a base material made of metal,
An exhaust pipe provided with a surface coating layer containing an amorphous inorganic material formed on the surface of the substrate,
There are pores in the surface coating layer,
The portion of the surface coating layer in the electron microscope image having a magnification of 500 times in the cross section parallel to the thickness direction of the exhaust pipe is perpendicular to the thickness direction of the exhaust pipe, and the thickness after cutting is the surface coating layer When the five strips are defined by cutting to be 1/5 of the thickness of
Among the area of the pores present in the entire surface coating layer, there is at least one pore concentration portion which is a strip portion having pores of 30% or more as the pore area,
The strip portion which is the pore concentration portion is a central strip portion of five strip portions or one or two strip portions adjacent to the central strip portion,
The pores present in the surface coating layer have independent pores, and the independent pores do not communicate between the outside of the exhaust pipe and the surface of the substrate.

In the exhaust pipe according to claim 1, the surface covering layer is provided with a pore concentrating portion which is a strip portion in which 30% or more of the pores are present as the area of the pores in the entire surface covering layer. ing.
It is considered that a crack generated in the surface coating layer due to thermal shock first occurs on the surface of the surface coating layer and progresses toward the base material in the thickness direction of the surface coating layer.
When a crack generated in the surface coating layer develops and collides with an independent pore, the crack is prevented from progressing before the independent pore. That is, if at least one of the strips in the surface coating layer is a pore concentration part, even if a crack occurs on the surface of the surface coating layer, the crack easily collides with independent pores existing in the pore concentration part. It is possible to prevent the crack from progressing to the base material side from the pore concentration portion.
The pores have independent pores, and the independent pores do not communicate the outside of the exhaust pipe with the surface of the base material. If the independent pores do not communicate with the outside of the exhaust pipe and the surface of the base material, the crack does not penetrate the surface coating layer when the crack collides with the pores.
As described above, when the surface coating layer is provided with pore concentrating portions, and the independent pores provided in the surface coating layer do not communicate with the outside of the exhaust pipe and the surface of the substrate, the surface coating is caused by thermal shock. Even when cracks occur in the layer, the progress of cracks can be prevented by the independent pores present in the pore concentration portion.
As a result, the surface coating layer can be prevented from being destroyed. Therefore, the exhaust pipe can ensure high insulation.

3. The exhaust pipe according to claim 2, wherein the pore concentration portion has a pore ratio (B / A) that is a ratio of an area (B) occupied by pores to an area (A) of the strip portion of 0.02 or more.

When the pore ratio is 0.02 or more, pores for preventing the progress of cracks are sufficiently present in the pore concentration portion, and the probability that the cracks collide with the pores increases. Therefore, since the progress of a crack is prevented more reliably, it is more preferable.

In the exhaust pipe according to claim 3, the surface coating layer further includes a crystalline inorganic material.

Crystalline inorganic materials tend to have high infrared emissivity. For this reason, if the surface coating layer contains a crystalline inorganic material, infrared radiation from the crystalline inorganic material is generated, so the emissivity of the surface coating layer increases, and the exhaust pipe has excellent heat dissipation at high temperatures. It can be.

In the exhaust pipe according to claim 4, the surface coating layer includes an amorphous inorganic material layer containing an amorphous inorganic material, and a mixed layer containing an amorphous inorganic material and a crystalline inorganic material. The pore concentration part includes a boundary between the amorphous inorganic material layer and the mixed layer.

When forming the surface coating layer, a roughened surface is formed on the surface of the lower layer (the layer closer to the substrate), and the upper layer on the roughened surface (the material is different from the lower layer) By forming the layer, the pore concentration part is formed at a position including the boundary between the lower layer and the upper layer.
That is, in the exhaust pipe according to claim 4, pores are formed at positions including a boundary between a lower layer (mixed layer or amorphous inorganic material layer) and an upper layer (amorphous inorganic material layer or mixed layer). A concentrated part is formed. If the pore concentrating portion is formed at this position, the thermal stress generated between the upper layer and the lower layer is relieved by the pores existing in the pore concentrating portion, so that the thermal shock resistance is excellent.

In the exhaust pipe according to claim 5, the crystalline inorganic material contains at least one oxide of manganese, iron, copper, cobalt, chromium, and aluminum.

Since the oxide has a high infrared emissivity, the emissivity of the surface coating layer can be further increased. In particular, when aluminum oxide is used, it contributes to the improvement of the insulation of the exhaust pipe.

In the exhaust pipe according to claim 6, the number of the pore concentrating portions is one with respect to one surface of the base material, and the strip portion serving as the pore concentrating portion includes five strip portions. This is the central strip.

As the thickness of the surface coating layer increases, the strength of thermal shock on the surface coating layer tends to increase.
The fact that the strip portion which is the pore concentration portion is the central strip portion of the five strip portions means that the pore concentration portion exists at a position where the surface coating layer is divided into two in the thickness direction. That is.
When the pore concentrating portion exists at a position where the surface coating layer is divided into two in the thickness direction, the surface coating layer is divided into two portions having a half thickness by the pore concentrating portion. Therefore, the strength of the thermal shock on the surface coating layer becomes the same as that when the thickness of the surface coating layer is thin, and the surface coating layer can be more effectively prevented from being destroyed.

In the exhaust pipe according to claim 7, the number of the pore concentrating portions is two with respect to one surface of the base material, and the strip portion serving as the pore concentrating portion includes five strip portions. Of these, two strip portions adjacent to the central strip portion.

In the exhaust pipe according to claim 7, the surface coating layer is divided into three portions having a thickness of 1/3 by the two pore concentration portions. As in the exhaust pipe according to claim 6, it is more effective that the strength of the thermal shock to the surface coating layer is the same as that when the surface coating layer is thin, and the surface coating layer is destroyed. Can be prevented.

In the exhaust pipe according to claim 8, the thickness of the surface coating layer is 25 to 1000 μm.

When the thickness of the surface coating layer is less than 25 μm, sufficient insulation cannot be secured when used as an exhaust pipe. On the other hand, when the thickness of the surface coating layer exceeds 1000 μm, the strength of the thermal shock to the surface coating layer becomes strong, and the surface coating layer is easily broken.

In the exhaust pipe according to claim 9, the thermal conductivity of the surface coating layer at room temperature is 0.1 to 2 W / m · K.
If the thermal conductivity of the surface coating layer at room temperature is less than 0.1 W / m · K, the heat dissipation of the exhaust pipe in the high temperature region is insufficient, and the heat of the exhaust gas passing through the exhaust pipe is difficult to dissipate to the outside. Become.
Also, if the thermal conductivity of the surface coating layer at room temperature exceeds 2 W / m · K, the heat retention of the exhaust pipe in the low temperature region becomes insufficient, and the time until the temperature of the catalytic converter reaches the catalyst activation temperature Becomes longer.

In the exhaust pipe according to claim 10, the volume resistance value of the exhaust pipe is 10 ⁷ to 10 ¹⁴ Ωm.
If the volume resistance value of the exhaust pipe is less than 10 ⁷ Ωm, there is a risk of leakage from the exhaust pipe.

In the exhaust pipe according to claim 11, the surface coating layer is formed by coating the surface coating layer forming raw material composition a plurality of times.
When the surface coating layer is formed by coating the raw material composition for forming the surface coating layer a plurality of times, the surface of the exhaust pipe and the surface of the substrate are formed in the surface coating layer formed by a single coating. Even if there is a communicating hole that communicates, the communicating hole is covered by the next coat. Therefore, the presence of pores communicating with the surface coating layer in the surface coating layer can be reliably prevented. If there are no pores communicating in the surface coating layer, moisture does not touch the surface of the base material, so that the base material made of metal does not rust and can be an exhaust pipe.

In the exhaust pipe according to a twelfth aspect, the surface coating layer further has blind pores, part of which communicates with the outside of the exhaust pipe.
Blind pores are pores that do not allow the outside of the exhaust pipe to communicate with the surface of the base material, like the independent pores. Therefore, even if the exhaust pipe has blind pores in the surface coating layer, it is possible to prevent cracks from progressing to the substrate side with respect to the boundary portion between the amorphous inorganic material layer and the mixed layer.

The exhaust pipe according to claim 13, a base material made of metal,
An exhaust pipe provided with a surface coating layer containing an amorphous inorganic material formed on the surface of the substrate,
The surface coating layer has an amorphous inorganic material layer containing an amorphous inorganic material, and a mixed layer containing an amorphous inorganic material and a crystalline inorganic material,
The surface coating layer has independent pores,
The independent pores do not communicate with the outside of the exhaust pipe and the surface of the base material, and the independent pores are localized at the boundary between the amorphous inorganic material layer and the mixed layer. To do.

It is considered that a crack generated in the surface coating layer due to thermal shock first occurs on the surface of the surface coating layer and progresses toward the base material in the thickness direction of the surface coating layer.
When a crack generated in the surface coating layer develops and collides with an independent pore, the crack is prevented from progressing before the independent pore.
If independent pores that do not communicate with the outside of the exhaust pipe and the surface of the base material are localized at the boundary between the amorphous inorganic material layer and the mixed layer, even if a crack occurs on the surface of the surface coating layer, Since the cracks easily collide with the independent pores localized at the boundary between the amorphous inorganic material layer and the mixed layer, the crack propagates more toward the substrate than the boundary between the amorphous inorganic material layer and the mixed layer. Is prevented.
As a result, the surface coating layer can be prevented from being destroyed. Therefore, the exhaust pipe can ensure high insulation.

15. The exhaust pipe according to claim 14, wherein the surface coating layer further has blind pores, part of which communicates with the outside of the exhaust pipe.
Blind pores are pores that do not allow the outside of the exhaust pipe to communicate with the surface of the base material, like the independent pores. Therefore, even if the exhaust pipe has blind pores in the surface coating layer, it is possible to prevent cracks from progressing to the substrate side with respect to the boundary portion between the amorphous inorganic material layer and the mixed layer.

The exhaust pipe manufacturing method according to claim 15 comprises:
Preparing a metal substrate;
Preparing a raw material composition for forming a surface coating layer;
A method for producing an exhaust pipe, comprising: a surface coating layer forming step of forming the surface coating layer by applying and firing the raw material composition for forming the surface coating layer on the metal substrate,
In the step of preparing the surface coating layer forming raw material composition, the amorphous inorganic material layer raw material composition containing an amorphous inorganic material and / or a mixed layer containing an amorphous inorganic material and a crystalline inorganic material A raw material composition was prepared, and a pore-forming material was prepared by blending a pore-forming material with the amorphous inorganic material layer raw material composition or the mixed layer raw material composition,
In the surface coating layer forming step, the pore concentration portion forming raw material composition is applied at least once and baked to form pores in the surface coating layer, and the amorphous inorganic material layer raw material composition or the above The mixed layer material composition is applied at least once.

In the manufacturing method, a pore-forming material is prepared by blending a pore-forming material with the amorphous inorganic material layer raw material composition or the mixed layer raw material composition, and the pore-concentrating portion-forming raw material composition is prepared. The product is applied and fired.
Since the pores are formed at the position where the pore-forming material exists by firing, an exhaust pipe having a pore concentration portion at a desired position of the surface coating layer can be manufactured.

The exhaust pipe manufacturing method according to claim 16 comprises:
Preparing a metal substrate;
Preparing a raw material composition for forming a surface coating layer;
A method for producing an exhaust pipe, comprising a step of forming a surface coating layer by applying the surface coating layer forming raw material composition a plurality of times on the metal substrate and firing the composition;
In the surface coating layer forming step, a step of forming a lower surface coating layer by applying and baking the raw material composition for forming the surface coating layer at least once,
A step of roughening the surface of the lower surface coating layer, and
The surface coating layer forming raw material composition is applied to the surface of the roughened lower surface coating layer and baked to form an upper surface coating layer. At the same time, the lower surface coating layer and the upper surface coating layer are formed. It is characterized by forming pores between the layers.

In the said manufacturing method, the process of roughening the surface of the lower surface coating layer is performed. When the raw material composition for forming the upper surface coating layer is applied to the surface of the roughened lower surface coating layer, all the concave portions of the roughened surface on the surface of the lower surface coating layer are formed. However, a space remains between the concave portion of the roughened surface on the surface of the lower surface coating layer and the raw material composition for forming the upper surface coating layer. Since the space becomes pores after firing, independent pores localized at the boundary between the lower surface coating layer and the upper surface coating layer can be formed. And the exhaust pipe which has a pore concentration part in the desired position of a surface coating layer can be manufactured.

FIG. 1 is a cross-sectional view schematically showing an example of a cross section of an exhaust pipe according to the first embodiment of the first invention. FIG. 2A is a photograph of a part of the cross section of the exhaust pipe of the first embodiment of the first aspect of the present invention taken with an electron microscope image, and FIG. 2B is a strip in FIG. It is the photograph which showed the part and the pore. 3 (a), 3 (b), 3 (c) and 3 (d) are cross sections schematically showing an example of a cross section of another exhaust pipe of the first embodiment of the first invention. FIG. FIG. 4 is a cross-sectional view schematically showing an example of a cross section of another exhaust pipe according to the first embodiment of the first invention. 5 (a), 5 (b) and 5 (c) are cross-sectional views schematically showing an example of a cross section of still another exhaust pipe of the first embodiment of the first invention. FIGS. 6A and 6B are cross-sectional views schematically showing an example of a cross section of the exhaust pipe of the second embodiment of the first invention. FIGS. 7A and 7B are cross-sectional views schematically showing an example of a cross section of the exhaust pipe of the third embodiment of the first invention. 8 (a), 8 (b) and 8 (c) are cross-sectional views schematically showing a part of the process for manufacturing the exhaust pipe of the third embodiment of the first invention. FIGS. 9A and 9B are cross-sectional views schematically showing an example of a cross section of the exhaust pipe of the fourth embodiment of the first invention. FIG. 10 is a cross-sectional view schematically showing an example of a cross section of the exhaust pipe of the fifth embodiment of the first present invention. FIG. 11: is sectional drawing which shows typically an example of the cross section of the exhaust pipe of 6th embodiment of 2nd this invention. 12 is a cross-sectional view showing a case where the surface coating layer in the exhaust pipe shown in FIG. 11 has five strip portions. FIG. 13: is sectional drawing which shows typically an example of the cross section of the exhaust pipe of 7th embodiment of 2nd this invention. FIG. 14 is a cross-sectional view schematically showing an example of a cross section of the exhaust pipe of the eighth embodiment of the second invention.

(First embodiment)
Hereinafter, a first embodiment which is an embodiment of the exhaust pipe of the first invention will be described with reference to the drawings.
An exhaust pipe according to a first aspect of the present invention is an exhaust pipe including a base material made of a metal and a surface coating layer containing an amorphous inorganic material formed on the surface of the base material. The layer has pores, and the portion of the surface coating layer in the electron microscope image with a magnification of 500 times in the cross section parallel to the thickness direction of the exhaust pipe is perpendicular to the thickness direction of the exhaust pipe. When the five strips are defined by cutting so that the thickness after cutting is 1/5 of the thickness of the surface coating layer, the pores out of the area of the pores existing in the entire surface coating layer There is at least one pore concentrating portion which is a strip portion having pores of 30% or more as an area, and the strip portion serving as the pore concentrating portion is a central strip portion of the five strip portions or the center. Is one or two strip portions adjacent to the strip portion, and is present in the surface coating layer. Hole has a closed cell, and the closed cell is characterized in that that does not communicate with the outside surface of the base material of the exhaust pipe.

FIG. 1 is a cross-sectional view schematically showing an example of a cross section of an exhaust pipe according to the first embodiment of the first invention.
An exhaust pipe 1 as an example of the exhaust pipe of the present embodiment shown in FIG. 1 includes a base material 10 made of metal and a surface coating layer 20 formed on the surface of the base material 10.

Examples of the material of the base material 10 include metals such as stainless steel, steel, iron, and copper, and nickel alloys such as Inconel, Hastelloy, and Invar. Since these metal materials have high thermal conductivity, they can contribute to the improvement of heat dissipation of the exhaust pipe.
Although the shape of the base material 10 is not specifically limited, Since the shape of an exhaust pipe is usually a cylindrical shape, it is preferable to use a cylindrical shape.

The surface coating layer 20 has an amorphous inorganic material layer 21 containing an amorphous inorganic material 31 and a mixed layer 22 (22a, 22b) containing an amorphous inorganic material 31 and a crystalline inorganic material 32. Yes.
The surface coating layer 20 has a three-layer structure. Specifically, three layers are laminated in the order of the mixed layer 22b, the amorphous inorganic material layer 21, and the mixed layer 22a in this order from the substrate 10 side. Each layer is about 1/3 of the thickness of the surface coating layer 20.

The amorphous inorganic material layer 21 is preferably a layer containing a low-melting glass having a softening point of 300 to 1000 ° C. as the amorphous inorganic material 31. The kind of the low-melting glass is not particularly limited, and examples thereof include barium glass, boron glass, strontium glass, alumina silicate glass, soda zinc glass, and soda barium glass.
These glasses may be used alone or in combination of two or more.

Since such a low-melting glass has a softening temperature in the range of 300 to 1000 ° C., it is melted and coated on the outer peripheral surface of the base material, and then subjected to a heat-firing treatment, whereby the outer peripheral surface of the base material is surface-coated. The layer can be formed easily and firmly.

When the amorphous inorganic material is a low-melting glass, the softening point is preferably 300 to 1000 ° C.
When the softening point of the low-melting glass is less than 300 ° C., the low-melting glass is easily softened when an exhaust pipe is used, which may cause foreign matters to adhere to the surface coating layer. On the other hand, when the softening point of the low-melting glass exceeds 1000 ° C., the base material is likely to be deteriorated by heat treatment when the surface coating layer is formed.
Specific examples of the low melting point glass include, for example, SiO ₂ —B ₂ O ₃ —ZnO glass, SiO ₂ —B ₂ O ₃ —Bi ₂ O ₃ glass, SiO ₂ —PbO glass, SiO ₂ —PbO. —B ₂ O ₃ glass, SiO ₂ —B ₂ O ₃ —PbO glass, B ₂ O ₃ —ZnO—PbO glass, B ₂ O ₃ —ZnO—Bi ₂ O ₃ glass, B ₂ O ₃ — Bi ₂ O ₃ glass, B ₂ O ₃ —ZnO glass, BaO—SiO ₂ glass, and the like can be given.
The softening point should be measured, for example, using a glass automatic softening point / strain point measuring device (SSPM-31) manufactured by Opt Corp., based on the method specified in JIS R 3103-1: 2001. Can do.
The amorphous inorganic material may be composed of only one kind of low-melting glass among the above-described low-melting glasses, or may be composed of a plurality of kinds of low-melting glasses.

The mixed layer 22 is a layer that includes the amorphous inorganic material 31 included in the amorphous inorganic material layer 21 and further includes the crystalline inorganic material 32. As the crystalline inorganic material 32, it is desirable to use an oxide of a transition metal, and it is more desirable that the crystalline inorganic material 32 is an inorganic particle made of at least one oxide of manganese, iron, copper, cobalt, chromium, and aluminum.
Inorganic particles composed of these oxides may be used alone or in combination of two or more.
Since these transition metal oxides have high infrared emissivity, they contribute to improvement in heat dissipation from the exhaust pipe.
In particular, when aluminum oxide is used, it contributes to the improvement of the insulation of the exhaust pipe.

There are pores 33 in the surface coating layer 20 of the exhaust pipe 1 according to the present embodiment.
The pores 33 existing in the exhaust pipe 1 according to the present embodiment are independent pores. The independent pores are pores that exist inside the surface coating layer 20 and are not exposed from the surface of the surface coating layer.
The independent pores are pores that do not communicate the outside of the exhaust pipe with the surface of the base material.

In the surface coating layer 20 of the exhaust pipe 1 according to the present embodiment, a pore concentration portion 23 exists.
Hereinafter, a method for defining the pore concentration portion 23 will be described with reference to the drawings.
When determining the pore concentrating portion, an electron microscope image having a magnification of 500 times in a cross section parallel to the thickness direction of the exhaust pipe is taken, and the surface coating layer portion is perpendicular to the thickness direction of the exhaust pipe. Then, cutting is performed so that the thickness after cutting becomes 1/5 of the thickness of the surface coating layer, and five strips are defined.
In FIG. 1, five strip portions are indicated by 20A, 20B, 20C, 20D and 20E.
Then, the area of the pores 33 existing in the entire surface coating layer 20 is calculated, and among the areas of the pores 33 existing in the entire surface coating layer 20, the strip portion having 30% or more of the pores as the pore area is concentrated in the pores. Set as part.
In the exhaust pipe 1 shown in FIG. 1, the strip portion 20 </ b> C is a pore concentration portion 23.
The pore concentration part 23 is a part of the amorphous inorganic material layer 21.
It should be noted that the pores 33 may or may not exist in the parts other than the pore concentration part 23.

FIG. 2A is a photograph of a part of the cross section of the exhaust pipe of the first embodiment of the first aspect of the present invention taken with an electron microscope image, and FIG. 2B is a strip in FIG. It is the photograph which showed the part and the pore.
In the photographs shown in FIGS. 2A and 2B, the acceleration voltage is 10.0 kV, the magnification is 500 times, and the photographing region (the lateral width of the photograph) is 250 μm.

The surface coating layer 20 in the exhaust pipe shown in the photographs of FIG. 2A and FIG. 2B is in order of an amorphous inorganic material layer, a mixed layer, and an amorphous inorganic material layer in this order from the base material 10 side. It has a configuration in which three layers are stacked.
In the photographs of FIG. 2A and FIG. 2B, the boundary line of each layer cannot be clearly identified, but the thickness of each layer is about 25 μm.

In determining the pore concentration portion, in the cross-sectional photographs shown in FIG. Is cut into strips so that the thickness becomes 1/5 of the thickness of the surface coating layer.
At this time, the thickness of the surface coating layer is determined with the upper surface of the surface coating layer 20 as the starting point and the surface of the substrate as the end point, and cutting is performed. And each strip-shaped part cut | disconnected by the said procedure is defined as a strip part.

When the position of the upper surface (starting point of cutting) of the surface coating layer 20 is determined, when the upper surface is uneven, the most concave portion is determined as the upper surface of the surface coating layer 20. The position of the upper surface of the surface coating layer 20 is a position indicated by a broken line in FIG.
In the photograph shown in FIG. 2B, no conspicuous unevenness exists on the upper surface of the surface coating layer.

Further, when determining the position of the surface of the substrate (end point of cutting), when the surface of the substrate has irregularities, the most concave portion is determined as the surface of the substrate. The position of the surface of the substrate is the position indicated by the alternate long and short dash line in FIG.

In the photograph shown in FIG. 2B, five strip portions indicated by reference signs A to E are defined from the upper surface side of the surface coating layer to the base material side by the above procedure.

After determining the strip portion in this manner, the ratio of the area of the pores existing in the entire surface coating layer and the area of the pores existing in each strip portion out of the area of the pores existing in the entire surface coating layer is determined.
In determining the area of the pores, “pores” existing in the surface coating layer are determined.
In the present specification, pores having a pore diameter of 5 μm or more are referred to as “pores” in a cross-sectional photograph taken with an electron microscope. The “pore diameter” is determined as the diameter of the pore if the shape is circular.
When the shape of the pores is non-circular, the maximum length when a straight line is drawn in the pores is determined as the diameter of the pores.
In the photograph of FIG. 2B, the pores determined as “pores” by the above procedure are indicated by circles.
When calculating the area of the pores, only the area of the circled pores (the pores determined as “pores”) is considered.

After the “pores” existing in the surface coating layer are determined, all the areas of the pores existing in the surface coating layer are totaled to obtain “the area of the pores existing in the entire surface coating layer”.
Subsequently, the areas of all the pores present in each strip portion are summed to obtain “the area of the pores present in the strip portion” for each strip portion.
Subsequently, the ratio of “the area of pores existing in the strip portion” of each strip portion to the “area of pores existing in the entire surface coating layer” is set to 100% of “the area of pores existing in the entire surface coating layer”. It is expressed as a percentage.
FIG. 2B shows the ratio of “the area of pores existing in the strip portion” of each strip portion to “the area of pores existing in the entire surface coating layer” for the strip portions A to E.
In the strip portion C, the ratio is 73.8%, which is 30% or more. Therefore, the strip portion C is defined as the pore concentration portion (pore concentration portion 23).
The other strips A, B, D, and E are not pore concentration portions because the ratio is less than 30%.

In the present embodiment, the pore ratio (B / A), which is the ratio of the area (B) occupied by the pores to the area (A) of the strips, is 0.02 or more in the pore concentration portion.
The pore ratio is determined by obtaining the area (A) of the strip portion, obtaining the “area of pores existing in the strip portion” (B) of each strip portion, and obtaining the ratio (B / A).
The porosity of the strip C shown in FIG. 2 (b) is 0.27.

In the photograph shown in FIG. 2B, the pore concentrating portion is only the strip portion C, and the number of the pore concentrating portions is one.
When counting the number of pore concentrating portions present in the surface coating layer, if both adjacent strip portions are pore concentrating portions, the number of pore concentrating portions is assumed to be one.
Further, when there are strip portions that are not pore concentration portions between the pore concentration portions and the pore concentration portions, they are different pore concentration portions, and the number of pore concentration portions is two. .

The thickness of the surface coating layer in the exhaust pipe of this embodiment is preferably 25 to 1000 μm.
When the thickness of the surface coating layer is less than 25 μm, sufficient insulation cannot be secured when used as an exhaust pipe. On the other hand, when the thickness of the surface coating layer exceeds 1000 μm, the strength of the thermal shock to the surface coating layer becomes strong, and the surface coating layer is easily broken.
The thermal conductivity of the surface coating layer at room temperature (25 ° C.) is preferably 0.1 to 2 W / m · K.
If the thermal conductivity of the surface coating layer at room temperature is less than 0.1 W / m · K, the heat dissipation of the exhaust pipe in the high temperature region is insufficient, and the heat of the exhaust gas passing through the exhaust pipe is difficult to dissipate to the outside. Become.
Also, if the thermal conductivity of the surface coating layer at room temperature exceeds 2 W / m · K, the heat retention of the exhaust pipe in the low temperature region becomes insufficient, and the time until the temperature of the catalytic converter reaches the catalyst activation temperature Becomes longer.
The thermal conductivity of the surface coating layer at room temperature can be measured by a laser flash method.
The emissivity of the surface coating layer at a wavelength of 1 to 15 μm at room temperature (25 ° C.) is desirably 0.6 or more. When the emissivity of the surface coating layer is less than 0.6, the heat dissipation of the exhaust pipe in a high temperature region is insufficient, and the heat of the exhaust gas passing through the exhaust pipe is hardly radiated to the outside.
The emissivity of the surface coating layer at a wavelength of 1 to 15 μm at room temperature (25 ° C.) is desirably 0.99 or less. This is because it is difficult to increase the emissivity of the surface coating layer beyond 0.99.

The place where the electron microscope image of the magnification of 500 times of the cross section parallel to the thickness direction of the exhaust pipe is taken is the center point in the longitudinal direction of the exhaust pipe, the point 1/3 of the length in the longitudinal direction, the longitudinal direction The total number of points is 2/3 of the length.
When the surface coating layer is formed only on a part of the base material, the center point in the longitudinal direction of the exhaust pipe and 1/3 of the length in the longitudinal direction of the portion where the surface coating layer is formed , And 2/3 of the length in the longitudinal direction.
An exhaust pipe that satisfies the requirements defined in the first aspect of the present invention at any of these three measurement points is the exhaust pipe of the first aspect of the present invention.

3 (a), 3 (b), 3 (c) and 3 (d) are cross sections schematically showing an example of a cross section of another exhaust pipe of the first embodiment of the first invention. FIG.
In the exhaust pipe 50 shown in FIG. 3A, the surface coating layer 20 has a three-layer structure. The arrangement of the mixed layer and the amorphous inorganic material layer is opposite to the arrangement of the mixed layer and the amorphous inorganic material layer in the exhaust pipe 1 shown in FIG.
Specifically, in order from the substrate 10 side, three layers are laminated in the order of the amorphous inorganic material layer 21b, the mixed layer 22, and the amorphous inorganic material layer 21a. Is about 1/3 of the thickness of the surface coating layer 20.
In the exhaust pipe 50 shown in FIG. 3A, the pore concentrating part 23 exists in the mixed layer 22 which is a central layer.

In the exhaust pipe 60 shown in FIG. 3B, the surface coating layer 20 is composed of two layers, an amorphous inorganic material layer 21 and a mixed layer 22.
In the exhaust pipe 60, the portion of the surface coating layer 20 having a thickness of about 2/3 on the base material side is the mixed layer 22, and the portion of the surface side of the exhaust pipe having a thickness of about 1/3 is amorphous. This is the inorganic material layer 21.
In the exhaust pipe 60 shown in FIG. 3B, the pore concentrating portion 23 exists in the mixed layer 22.

In the exhaust pipe 70 shown in FIG. 3C, the surface coating layer 20 is composed of two layers, an amorphous inorganic material layer 21 and a mixed layer 22.
In the exhaust pipe 70, the portion of the surface coating layer 20 having a thickness of about 1/3 on the base material side is the mixed layer 22, and the portion of the surface side of the exhaust pipe having a thickness of about 2/3 is amorphous. This is the inorganic material layer 21.
In the exhaust pipe 70 shown in FIG. 3C, the pore concentration part 23 exists in the amorphous inorganic material layer 21.

In the exhaust pipe 80 shown in FIG.
Each of the surface coating layers 20a and 20b has a two-layer structure similar to the surface coating layer shown in FIG.
The surface coating layer 20a has a configuration in which two layers are laminated in the order of the mixed layer 22a and the amorphous inorganic material layer 21a in this order from the substrate 10 side.
In the exhaust pipe 80 shown in FIG. 3D, the pore concentration part 23a exists in the mixed layer 22a.
The surface coating layer 20b has a configuration in which two layers are laminated in the order of the mixed layer 22b and the amorphous inorganic material layer 21b in this order from the substrate 10 side.
In the exhaust pipe 80 shown in FIG. 3D, the pore concentrating portion 23b exists in the mixed layer 22b.
In the exhaust pipe 80, of the surface coating layers 20a and 20b, the part having a thickness of about 2/3 on the substrate side is the

mixed layer

22a and 22b, and the part having a thickness of about 1/3 on the surface side of the exhaust pipe. Are the amorphous

inorganic material layers

21a and 21b.

The order of lamination of the mixed layer 22 and the amorphous inorganic material layer 21 is not particularly limited, but as shown in FIGS. 1, 3B, 3C, and 3D. More preferably, the mixed layer 22 is disposed at a position in contact with the substrate 10. Since the adhesive force between the mixed layer 22 and the base material 10 is higher than the adhesive force between the amorphous inorganic material layer 21 and the base material 10, and is more preferable in that the adhesion between the base material and the surface coating layer can be improved. It is.

FIG. 4 is a cross-sectional view schematically showing an example of a cross section of another exhaust pipe according to the first embodiment of the first invention.
In the exhaust pipe 190 shown in FIG. 4, the surface coating layer 20 has a three-layer structure.
Specifically, the three layers are laminated in this order from the substrate 10 side in the order of the mixed layer 22, the amorphous inorganic material layer 21b, and the amorphous inorganic material layer 21a.
The thickness ratio of the mixed layer 22, the amorphous inorganic material layer 21b, and the amorphous inorganic material layer 21a is as follows: mixed layer 22: amorphous inorganic material layer 21b: amorphous inorganic material layer 21a = 25: 10: 5.
In FIG. 4, five strip portions corresponding to the thickness ratio are indicated by 20A, 20B, 20C, 20D and 20E.
The amorphous inorganic material layer 21 b has many large independent pores 33, and most of the strip portions 20 </ b> B are the amorphous inorganic material layer 21 b, so that the strip portions 20 </ b> B become the pore concentration portions 23.
The strip portion 20B is a strip portion adjacent to the central strip portion 20C among the five strip portions.

In order to form the surface coating layer as shown in FIG. 4, a pore forming material was blended with the mixed layer raw material composition and the amorphous inorganic material layer raw material composition in the method of manufacturing the exhaust pipe described later. Application may be performed in the order of the pore concentration portion forming raw material composition and the amorphous inorganic material layer raw material composition, and the thickness of each layer may be adjusted by adjusting the application amount in each application step.

5 (a), 5 (b) and 5 (c) are cross-sectional views schematically showing an example of a cross section of another exhaust pipe according to the first embodiment of the first invention.
In the exhaust pipe 90 shown to Fig.5 (a), the shape of a base material differs from the exhaust pipe of 1st embodiment of 1st this invention shown in FIG.
In the exhaust pipe 90, the shape of the base material 11 is a semi-cylindrical shape in which the cylinder is cut in half.
The surface coating layer 20 is formed on the surface of the base material 11 on the side having a larger area. The configuration of the surface coating layer 20 in the exhaust pipe 90 is the same as the configuration of the surface coating layer 20 in the exhaust pipe 70 shown in FIG.
In the exhaust pipe of the present embodiment, when the semi-cylindrical base material 11 is used, the surface on which the surface coating layer 20 is formed is the surface on the side having a smaller area (the side opposite to the form shown in FIG. 5A). Surface).
Further, the surface coating layer 20 may be formed on both surfaces of the base material 11.

In the exhaust pipe 100 shown in FIG.5 (b), the shape of the base material 12 is a cylindrical shape.
The surface coating layer 20 is formed on the surface of the base material 11 on the side having the larger area (on the outer peripheral surface). The configuration of the surface coating layer 20 in the exhaust pipe 100 is the same as the configuration of the surface coating layer 20 in the exhaust pipe 70 shown in FIG.
In the exhaust pipe of the present embodiment, the surface on which the surface coating layer 20 is formed when the cylindrical substrate 12 is used may be a surface on the side having a smaller area (on the inner peripheral surface).

In the exhaust pipe 110 shown in FIG.5 (c), the shape of the base material 12 is a cylindrical shape.
The surface coating layer 20 is formed on both surfaces of the surface of the substrate 11, that is, on the outer peripheral surface and the inner peripheral surface.
The configuration of the surface coating layers 20a and 20b in the exhaust pipe 110 is the same as the configuration of the surface coating layer 20 in the exhaust pipe 70 shown in FIG.

This embodiment shown in FIG. 1, FIG. 3 (a), FIG. 3 (b), FIG. 3 (c), FIG. 3 (d), FIG. 5 (a), FIG. 5 (b) and FIG. In this exhaust pipe, the number of pore concentrating portions 23 is one with respect to one surface of the substrate, and the pore concentrating portions 23 exist in the central strip portion of the five strip portions. That is, the pore concentration part 23 exists in the position which divides the surface coating layer 20 (20a, 20b) into two in the thickness direction.

In addition, the fact that the pore concentrating portion is provided in the exhaust pipe of the present embodiment does not mean that the pores are evenly distributed in the surface coating layer, and the pores are not present in the portion other than the pore concentrating portion of the surface coating layer. It is shown that there are sites with less (non-stomach concentration part).
The part with few pores contributes to the improvement of the mechanical strength and insulation of the entire surface coating layer.
This is because the strength of the surface coating layer is higher as the number of pores is smaller, and the volume resistance is higher in a portion having fewer pores.
The dielectric breakdown distance of the pores is 3 kV / mm. When 500 V is applied, the insulation does not contribute to the improvement of the insulation without a pore diameter of 167 μm or more.
Since the pore diameter in the exhaust pipe of the present embodiment is almost less than 167 μm, the volume resistance is higher in the portion having fewer pores.
Therefore, the exhaust pipe of the present embodiment can exhibit an advantageous effect as compared with the exhaust pipe in which many pores exist in the entire surface coating layer.

Next, a method for manufacturing an exhaust pipe according to the first embodiment of the first invention will be described in the order of steps.
The method for producing an exhaust pipe according to the first embodiment of the first invention includes a step of preparing a metal substrate,
Preparing a raw material composition for forming a surface coating layer;
A method for producing an exhaust pipe, comprising: a surface coating layer forming step of forming the surface coating layer by applying and firing the raw material composition for forming the surface coating layer on the metal substrate,
In the step of preparing the surface coating layer forming raw material composition, the amorphous inorganic material layer raw material composition containing an amorphous inorganic material and / or a mixed layer containing an amorphous inorganic material and a crystalline inorganic material A raw material composition was prepared, and a pore-forming material was prepared by blending a pore-forming material with the amorphous inorganic material layer raw material composition or the mixed layer raw material composition,
In the surface coating layer forming step, the pore concentration portion forming raw material composition is applied at least once and baked to form pores in the surface coating layer, and the amorphous inorganic material layer raw material composition or the above The mixed layer material composition is applied at least once.
Here, taking the case of manufacturing the exhaust pipe 1 of the first embodiment of the first invention schematically shown in FIG. 1, the manufacture of the exhaust pipe according to the first embodiment of the first invention is taken as an example. The method will be described.

(1) Using a metal base material (metal base material) as a starting material, first, a cleaning process is performed to remove impurities on the surface of the metal base material.
The cleaning process is not particularly limited, and a conventionally known cleaning process can be used. Specifically, for example, a method of performing ultrasonic cleaning in an alcohol solvent can be used.

Further, after the cleaning treatment, if necessary, the surface of the base material may be roughened to increase the specific surface area of the base material surface or to adjust the surface roughness of the base material. Good. Specifically, for example, a roughening process such as a sandblast process, an etching process, or a high temperature oxidation process may be performed. These may be used alone or in combination of two or more.
You may perform a washing process after this roughening process.

(2) A crystalline inorganic material and an amorphous inorganic material are wet-mixed to prepare a mixed layer raw material composition.
Specifically, the powder of the crystalline inorganic material and the powder of the amorphous inorganic material are prepared so as to have a predetermined particle size, shape, etc., and each powder is dry-mixed at a predetermined blending ratio and mixed powder The mixed layer raw material composition is prepared by adding water and wet mixing with a ball mill.
Here, the mixing ratio of the mixed powder and water is not particularly limited, but is preferably about 100 parts by weight of water with respect to 100 parts by weight of the mixed powder. It is because it becomes a viscosity suitable for apply | coating to a metal base material. Moreover, you may mix | blend dispersion media, such as an organic solvent, and an organic binder with the said raw material composition for mixed layers as needed.

(3) A raw material composition for an amorphous inorganic material layer containing an amorphous inorganic material is prepared.
Preparation of the raw material composition for the amorphous inorganic material layer can be carried out in the same manner as in the preparation method of the raw material composition for the mixed layer, except that the crystalline inorganic material is not added and dry mixing is not performed. it can.

(4) A raw material composition for forming pore concentration parts is prepared.
When forming the pore concentration part in the mixed layer, as a method for forming the pore concentration part, in the raw material composition for the mixed layer, at least one of a pore former, a foaming agent, a hollow filler, and inorganic fibers It is possible to use a method of preparing a pore concentration part forming raw material composition by blending one pore forming material.
Among these, it is preferable to use a pore former.
As the pore former, for example, balloons that are fine hollow spheres containing oxide ceramics, spherical acrylic particles, graphite and the like can be used.
In addition, when forming a pore concentration part in an amorphous inorganic material layer, at least one of a pore former, a foaming agent, a hollow filler, and an inorganic fiber is used as the raw material composition for an amorphous inorganic material layer. A blending method can be used.
In the present specification, hereinafter, the mixed layer raw material composition and the amorphous inorganic material layer raw material composition including the pore concentration portion forming raw material composition are also referred to as a surface coating layer forming raw material composition.

(5) The surface of the metal substrate is coated with a surface coating layer forming raw material composition (mixed layer raw material composition).
Examples of the method for coating the mixed layer material composition include spray coating, electrostatic coating, inkjet, transfer using a stamp or roller, and brushing.
Moreover, you may coat the said raw material composition for surface coating layers by immersing the said metal base material in the said raw material composition for surface coating layers.
When the exhaust pipe 1 shown in FIG. 1 is manufactured, the mixed layer 22b, the amorphous inorganic material layer 21 including the pore concentrating portion 23, and the mixed layer 22a are sequentially stacked from the base material side.
Therefore, first, the raw material composition for the mixed layer is coated on the surface of the metal substrate.

(6) The metal substrate coated with the surface coating layer raw material composition (mixed layer raw material composition) is fired.
Specifically, the metal substrate coated with the surface coating layer raw material composition is dried and then heated and fired to form the surface coating layer.
The firing temperature is preferably set to be equal to or higher than the softening point of the amorphous inorganic material, and is preferably 700 ° C. to 1100 ° C. depending on the kind of the blended amorphous inorganic material. By setting the firing temperature to a temperature equal to or higher than the softening point of the amorphous inorganic material, the metal substrate and the amorphous inorganic material can be firmly adhered, and the surface coating layer (mixed layer) firmly adhered to the substrate ) Can be formed.

(7) A surface coating layer forming raw material composition (a pore concentration portion forming raw material composition) is coated on the surface of the surface coating layer (mixed layer). In this step, the pore concentration portion forming raw material composition in which the pore former is blended in the amorphous inorganic material layer raw material composition is coated. And after drying, a surface coating layer is formed by baking by heating.
Since pores are formed by the function of the pore former in the process of drying and heating and firing, the surface coating layer laminated in this step becomes an amorphous inorganic material layer including pore concentration portions.
The coating method and drying / firing method of the raw material composition for forming the surface coating layer can be performed in the same manner as in the above steps (5) and (6).

(8) A surface coating layer forming raw material composition (mixed layer raw material composition) is coated on the surface of the surface coating layer (amorphous inorganic material layer including pore-concentrated portions). And after drying, a surface coating layer is formed by baking by heating. The surface coating layer laminated in this step becomes a mixed layer.
The coating method and drying / firing method of the raw material composition for forming the surface coating layer can be performed in the same manner as in the above steps (5) and (6).
By the above procedure, the exhaust pipe of the present embodiment (the exhaust pipe 1 schematically shown in FIG. 1) can be manufactured.

The effects of the exhaust pipe of the present embodiment and the exhaust pipe manufacturing method of the present embodiment will be listed below.
(1) In the exhaust pipe of the present embodiment, the surface covering layer is provided with a pore concentrating portion which is a strip portion in which 30% or more of the pores exist as the area of the pores in the entire surface covering layer. It has been.
It is considered that a crack generated in the surface coating layer due to thermal shock first occurs on the surface of the surface coating layer and progresses toward the base material in the thickness direction of the surface coating layer.
When a crack generated in the surface coating layer progresses and collides with a pore, the crack is prevented from progressing before the pore. That is, if at least one of the strips in the surface coating layer is a pore concentration part, even if cracks occur on the surface of the surface coating layer, the cracks easily collide with the pores existing in the pore concentration part. It is possible to prevent cracks from developing on the substrate side with respect to the concentrated portion.
The pores are independent pores, and the pores do not communicate the outside of the exhaust pipe with the surface of the substrate. If the pores do not communicate with the outside of the exhaust pipe and the surface of the substrate, the cracks do not penetrate the surface coating layer when the cracks collide with the pores.
As described above, when the surface coating layer is provided with the pore concentrating portions, and the pores provided in the surface coating layer do not communicate with the outside of the exhaust pipe and the surface of the substrate, the surface coating layer is caused by thermal shock. Even if cracks occur in the inside, the progress of cracks can be prevented by the pores present in the pore concentration portion.
As a result, the surface coating layer can be prevented from being destroyed. Therefore, the exhaust pipe can ensure high insulation.

(2) In the exhaust pipe of the present embodiment, the pore concentration portion has a pore ratio (B / A) that is a ratio of the area (B) occupied by the pores to the area (A) of the strip portion is 0.02 or more. When the pore ratio is 0.02 or more, the pores for preventing the progress of cracks are sufficiently present in the pore concentration portion, and the probability that the cracks collide with the pores increases. Therefore, the progress of cracks can be prevented more reliably.

(3) In the exhaust pipe of this embodiment, the surface coating layer contains a crystalline inorganic material. The crystalline inorganic material contains at least one oxide of manganese, iron, copper, cobalt, chromium, and aluminum.
Since the oxide has a high infrared emissivity, the emissivity of the surface coating layer can be further increased. When the emissivity of the surface coating layer is increased, an exhaust pipe excellent in heat dissipation at high temperatures can be obtained.
In particular, when an aluminum oxide is used, it contributes to an improvement in the insulation of the exhaust pipe.

(4) In the exhaust pipe of the present embodiment, the number of the pore concentrating portions is one with respect to one surface of the base material, and the strip portions serving as the pore concentrating portions are five strip portions. Including the case of the central strip portion.
If the pore concentrating portion is present in the central strip portion where the surface covering layer is divided into two in the thickness direction, the surface covering layer is divided into two portions having a half thickness by the pore concentrating portion. Will be divided. Therefore, the strength of the thermal shock on the surface coating layer becomes the same as that when the thickness of the surface coating layer is thin, and the surface coating layer can be more effectively prevented from being destroyed.

(5) In the exhaust pipe of this embodiment, the thickness of the surface coating layer is 25 to 1000 μm.
When the thickness of the surface coating layer is less than 25 μm, sufficient insulation cannot be secured when used as an exhaust pipe. On the other hand, when the thickness of the surface coating layer exceeds 1000 μm, the strength of the thermal shock to the surface coating layer becomes strong, and the surface coating layer is easily broken.
(6) In the exhaust pipe manufacturing method of the present embodiment, a pore forming material is blended with the amorphous inorganic material layer raw material composition or the mixed layer raw material composition to prepare a pore concentration portion forming raw material composition. Then, the metal substrate coated with the raw material composition for forming pore concentration portions is subjected to a firing treatment.
Since the pores are formed at the positions where the pore-forming material is present by the above-described treatment, it is possible to manufacture the exhaust pipe having the pore concentration portions at the desired positions of the surface coating layer.

(Example)
Hereinafter, the first invention will be described in more detail with reference to examples, but the first invention is not limited to these examples.

(Preparation of base material)
As a base material made of a metal, a plate-like stainless steel base material (made of SUS430) having a thickness of 2 mm is used as a material, and ultrasonic cleaning is performed in an alcohol solvent. Was roughened. The sand blast treatment was performed for 10 minutes using # 80 Al ₂ O ₃ abrasive grains.
A flat substrate was produced by the above treatment.

Using a cylindrical stainless steel substrate (made of SUS430) having a diameter of 40 mm and a thickness of 2 mm as a material, the same cleaning treatment and roughening treatment as those performed on the flat substrate were performed, and a cylindrical substrate was obtained. A material was prepared.
Further, the cylindrical base material was cut in half to prepare a semi-cylindrical base material.

(Preparation of mixed layer raw material composition)
As a crystalline inorganic material powder, a powder composed of 30 wt% MnO ₂ powder, 5 wt% FeO powder, 5 wt% CuO powder, and 5 wt% CoO powder was prepared.
As an amorphous inorganic material powder, K4006A-100M (Bi ₂ O ₃ -B ₂ O ₃ glass, softening point 770 ° C.) manufactured by Asahi Glass Co., Ltd. was prepared.
As an organic binder, methyl cellulose (product name: METOLOSE-65SH) manufactured by Shin-Etsu Chemical Co., Ltd. was prepared.
In preparing the mixed layer raw material composition, a crystalline inorganic material powder and an amorphous inorganic material powder are dry mixed to prepare a mixed powder, and 100 parts by weight of water is added to 100 parts by weight of the mixed powder. A slurry was prepared by wet mixing with a ball mill.
As the mixed layer raw material composition, two types of mixed layer raw material compositions X and mixed layer raw material composition Y were prepared.
The mixing ratio of the mixed layer raw material composition X is crystalline inorganic material: amorphous inorganic material: organic binder = 4: 6: trace amount (wt%), and the mixing ratio of the mixed layer raw material composition Y ( wt%) is crystalline inorganic material: amorphous inorganic material: organic binder = 1: 9: trace amount.
Here, the “trace amount” is 0.1 to 3 wt% when the total weight of the mixed layer raw material composition is 100 wt%.

(Preparation of raw material composition for amorphous inorganic material layer)
In the preparation procedure of the raw material composition for the mixed layer, a slurry to be the raw material composition for the amorphous inorganic material layer is prepared in the same manner except that the crystalline inorganic material is not used and the dry mixing step is not performed. Prepared.
Hereinafter, this slurry is also referred to as a raw material composition Z for an amorphous inorganic material layer.

(Preparation of raw material composition for forming pore concentration part)
In the preparation procedure of the raw material composition for the mixed layer or the preparation procedure of the raw material composition for the amorphous inorganic material layer, 10 wt% of fine hollow spheres mainly composed of silica as a pore-forming material when wet mixing is performed. By adding part, a raw material composition for forming a pore concentration part was prepared.
In addition, the raw material composition for pore concentration part formation prepared by adding a pore former to the raw material composition X for the mixed layer, the raw material composition Y for the mixed layer, and the raw material composition Z for the amorphous inorganic material layer, respectively, These are also referred to as a pore concentration part forming raw material composition X, a pore concentration part forming raw material composition Y, and a pore concentration part forming raw material composition Z.

The following examples and comparative examples were carried out using the base material, the mixed layer raw material composition, the amorphous inorganic material layer raw material composition, and the pore concentration part forming raw material composition prepared by the above procedure.
Example 1
The raw material composition X for mixed layers was applied to the surface of a flat substrate by spray coating, and dried at 70 ° C. for 20 minutes in a dryer. Subsequently, a surface coating layer (mixed layer) was formed by heating and baking in air at 850 ° C. for 15 minutes. The thickness of the mixed layer was 25 μm. This layer is also referred to as the first layer.

Subsequently, the pore concentration part forming raw material composition Z was applied to the surface of the mixed layer by spray coating and dried in a dryer at 70 ° C. for 20 minutes. Subsequently, a surface coating layer (amorphous inorganic material layer including pore concentrating portions) was formed by heating and baking in air at 850 ° C. for 15 minutes. The thickness of the amorphous inorganic material layer including the pore concentration portion was 10 μm. This layer is also called the second layer.

Subsequently, the amorphous inorganic material layer raw material composition Z was applied by spray coating on the surface of the amorphous inorganic material layer including the pore-concentrated portions, and dried at 70 ° C. for 20 minutes in a dryer. Subsequently, a surface coating layer (amorphous inorganic material layer) was formed by heating and baking in air at 850 ° C. for 15 minutes. The thickness of the amorphous inorganic material layer was 25 μm. This layer is also called the third layer.
An exhaust pipe was manufactured by the above procedure.

The thickness of the surface coating layer of the exhaust pipe thus obtained was 60 μm.
Moreover, the pore concentration part was formed at a position where the surface coating layer was divided into two in the thickness direction.

(Examples 2 to 7)
Exhaust pipes were manufactured in the same manner as in Example 1 except that the structure of the surface coating layer was changed as shown in Table 1.
Examples 2 to 7 differ from Example 1 in the following points.
In Example 2, the first layer is 25 μm using the mixed layer raw material composition X, the second layer is 10 μm using the pore concentration portion forming raw material composition X, and the amorphous inorganic material layer raw material composition Z Was used to form a third layer of 25 μm.
In Example 3, the first layer is 25 μm using the mixed layer raw material composition X on both surfaces of the base material, the second layer is 25 μm using the pore concentration portion forming raw material composition Z, and for the mixed layer A third layer of 25 μm was formed using the raw material composition X.
In Example 4, the first layer is 25 μm using the amorphous inorganic material layer raw material composition Z, the second layer is 25 μm using the pore concentration portion forming raw material composition X, and the amorphous inorganic material layer is used. A third layer of 25 μm was formed using the raw material composition Z.
In Example 5, the mixed layer raw material composition X is used to form the first layer of 5 μm, the pore concentration portion forming raw material composition Z is used to form the second layer of 10 μm, and the mixed layer raw material composition X is used. Three layers were formed to 5 μm.
In Example 6, on both surfaces of the base material, the first layer is 100 μm using the mixed layer raw material composition X, the second layer is 50 μm using the pore concentration portion forming raw material composition Y, amorphous A third layer of 50 μm was formed using the inorganic material layer raw material composition Z.
In Example 7, the first layer was 250 μm using the mixed layer raw material composition X, the second layer was 100 μm using the pore concentration forming raw material composition Z, and the amorphous inorganic material layer raw material composition Z Was used to form a third layer of 50 μm.
In any of the examples, the number of pore concentration portions was one for one surface of the substrate. In Examples 1 to 5, the strip portion serving as the pore concentration portion was the central strip portion of the five strip portions.
In Examples 6 and 7, the strip portion serving as the pore concentration portion is a strip portion (second strip portion from the top counted from the surface) adjacent to the central strip portion among the five strip portions. It was.

(Example 8)
In this example, a semi-cylindrical base material was used as the base material.
Then, an exhaust pipe was manufactured in the same manner as in Example 1 except that a surface coating layer was formed on the surface of the semicylindrical base material on the surface having the larger area so as to have the configuration shown in Table 1.
Specifically, the first layer is 50 μm using the mixed layer raw material composition X, the second layer is 50 μm using the pore concentration portion forming raw material composition X, and the amorphous inorganic material layer raw material composition Z. Was used to form a third layer of 35 μm.
Also in the present embodiment, the number of pore concentrating portions is one for one surface of the base material, and the strip portion serving as the pore concentrating portion is the central strip portion of the five strip portions. there were.

Example 9
In this example, a cylindrical base material was used as the base material.
And the exhaust pipe was manufactured like Example 1 except having formed the surface coating layer on both surfaces of the surface of a cylindrical base material so that it might become the composition shown in Table 1.
Specifically, the first layer is 50 μm using the mixed layer raw material composition X, the second layer is 50 μm using the pore concentration portion forming raw material composition X, and the amorphous inorganic material layer raw material composition Z. Was used to form a third layer of 35 μm.
Also in the present embodiment, the number of pore concentrating portions is one for one surface of the base material, and the strip portion serving as the pore concentrating portion is the central strip portion of the five strip portions. there were.

(Comparative Examples 1 to 6)
In each comparative example, the surface coating layer was formed so as to have the configuration shown in Table 1 without using the pore concentration portion forming raw material composition. In Comparative Examples 1 to 5, a surface coating layer was formed on one side of the substrate.
In Comparative Example 1, the first layer is 20 μm using the mixed layer raw material composition X, the second layer is 20 μm using the mixed layer raw material composition X, and the third layer using the mixed layer raw material composition X. Was formed to 20 μm.
In Comparative Example 2, the first layer is 25 μm using the mixed layer raw material composition X, the second layer is 10 μm using the amorphous inorganic material layer raw material composition Z, and the amorphous inorganic material layer raw material composition A third layer of 25 μm was formed using the object Z.
In Comparative Example 3, the first layer is 25 μm using the mixed layer raw material composition X, the second layer is 10 μm using the mixed layer raw material composition X, and the amorphous inorganic material layer raw material composition Z is used. A third layer of 25 μm was formed.
In Comparative Example 4, the first layer was formed to 50 μm using the mixed layer raw material composition X, and the second layer was formed to 50 μm using the mixed layer raw material composition X. The third layer was not formed.
In Comparative Example 5, a semi-cylindrical base material was used as the base material. The first layer is 50 μm using the mixed layer raw material composition X, the second layer is 50 μm using the mixed layer raw material composition X, and the third layer using the amorphous inorganic material layer raw material composition Z. A layer of 35 μm was formed.
In Comparative Example 6, a cylindrical base material was used as the base material. And on both surfaces of the surface of the cylindrical base material, the first layer is 50 μm using the mixed layer raw material composition X, the second layer is 50 μm using the mixed layer raw material composition X, and the amorphous inorganic material A third layer of 35 μm was formed using the layer raw material composition Z.
In any of the comparative examples, there was no pore concentration portion in the surface coating layer.

(Evaluation of exhaust pipe characteristics)
About the exhaust pipe manufactured by the Example and the comparative example, the characteristic was evaluated in the following procedures.
The evaluation results for each characteristic are summarized in Table 2.

(Thermal shock test)
Each exhaust pipe was heated to 600 ° C., the 600 ° C. exhaust pipe was dropped into 25 ° C. water to give a thermal shock, and it was visually confirmed whether or not there was peeling on the surface coating layer.
In the column of “peeling during thermal shock test” in Table 2, “existing” indicates that there was peeling in this test, and “no” indicates that there was no peeling.

(Measurement of volume resistance)
The volume resistance value of each exhaust pipe was measured using a digital ultrahigh resistance / microammeter (model number: R8340) manufactured by Advantest Corporation. The measurement was performed by applying a voltage of 500 V and measuring the resistance value of each exhaust pipe according to the procedure defined in JIS C 2141.
In addition, since the volume resistance value of a metal base material is very small, the volume resistance value measured here becomes a value depending on the magnitude of the volume resistance value of a surface coating layer substantially.

(Measurement of dielectric strength)
According to the procedure specified in JIS C 2110-2, a voltage of 500 V was applied to the front and back of the exhaust pipe, and the presence or absence of dielectric breakdown of each exhaust pipe was visually confirmed.
When the surface coating layer was formed only on one side of the exhaust pipe, one electrode was brought into contact with the upper surface of the surface coating layer and the other electrode was brought into contact with the substrate.
When the surface coating layer was formed on both surfaces of the exhaust pipe, one electrode was brought into contact with the upper surface of the surface coating layer on one surface, and the other electrode was brought into contact with the upper surface of the surface coating layer on the other surface.
In the column of “Dielectric withstand voltage (500V)” in Table 2, “Yes” indicates that the dielectric breakdown does not occur, and “No” indicates that the dielectric breakdown does not occur. Indicated.

(Measurement of emissivity)
The emissivity of the surface coating layer of each exhaust pipe was measured using an emissivity meter AERD (manufactured by Kyoto Electronics Industry Co., Ltd.).

(Measurement of thermal conductivity of surface coating layer)
The thermal conductivity of the surface coating layer of each exhaust pipe was measured using a laser flash device (thermal constant measuring device: NETZSCH LFA457 Microflash).

Table 2 shows the overall judgment as well as the measurement results for each exhaust pipe in four levels: excellent, good, good, and bad.
The overall criteria were as follows.
(1) Detachment in thermal shock test: Defect (2) Not applicable to (1), Dielectric withstand voltage “No”: Yes (3) Not applicable to (1) and (2) The volume resistance value is 1. E + 10 [Ωm] or less, emissivity less than 0.80, or surface coating layer thermal conductivity less than 0.5 [W / mK]: Good (4) (1) to (3 ) Not applicable to any of the above: Excellent In Examples 1 to 9 shown in Table 2, the evaluation result of Example 5 was “OK”, but other Examples 1 to 4 and Example 6 The evaluation results of ˜9 were “excellent”.
In each example, since the pore concentration portion was formed, no peeling occurred in the thermal shock test, and the surface coating layer was prevented from being broken.
In Example 5, the total film thickness of the surface coating layer is as thin as 20 μm. When the thickness of the surface coating layer was small, the insulation withstand voltage became “none” because sufficient insulation could not be secured. And since the withstand voltage became “none”, the evaluation result was “possible”.
In Comparative Examples 1 to 6, since the pore concentration portion was not formed, peeling occurred in the thermal shock test, and the evaluation results were all “bad”.

(Second embodiment)
Next, a second embodiment which is an embodiment of the exhaust pipe of the first invention will be described.
In the exhaust pipe of the second embodiment of the first aspect of the present invention, the surface coating layer consists of only an amorphous inorganic material layer or a mixed layer. The other structure is the same as that of the exhaust pipe of 1st embodiment of 1st this invention.
FIG. 6A and FIG. 6B are cross-sectional views schematically showing an example of the cross section of the exhaust pipe of the second embodiment of the first present invention.

In the exhaust pipe 120 shown in FIG. 6A, the surface coating layer 20 is composed of only the amorphous inorganic material layer 21, and no mixed layer is present. The pore concentrating portion 23 exists in the central strip portion of the five strip portions.

In the exhaust pipe 130 shown in FIG. 6B, the surface coating layer 20 is composed only of the mixed layer 22, and there is no amorphous inorganic material layer. The pore concentrating portion 23 exists in the central strip portion of the five strip portions.

In the exhaust pipe manufacturing method of the first embodiment of the first aspect of the present invention, the exhaust pipe of the present embodiment is the raw material composition for forming the surface coating layer, or only the raw material composition for the amorphous inorganic material layer, or It can manufacture by using only the raw material composition for mixed layers.
As shown in FIGS. 6 (a) and 6 (b), as a method for forming a pore concentrating portion in the central strip portion of the five strip portions, the coating of the raw material composition is made by each coat. The surface coating layer to be formed is divided into five times so that the thickness is the same, and the raw material composition to be coated third is at least one of a pore former, a foaming agent, a hollow filler, and inorganic fibers. The method of using the raw material composition for pore concentration part formation with which one was mix | blended is mentioned.
In addition, the coating of the raw material composition is divided into three times so that the thickness of the surface coating layer formed by each coating is the same, and as the raw material composition to be coated second, the above-mentioned pore concentration portion forming Even when the raw material composition is used, the pore concentration portion can be formed in the central strip portion of the five strip portions with high probability.
Moreover, a pore concentration part can be formed in a desired position also by changing suitably the thickness of the surface coating layer formed by a coating according to the frequency | count of a coating.

The exhaust pipe of this embodiment can exhibit the effects (1), (2), (4), and (5) of the exhaust pipe of the first embodiment of the first invention. Further, when the surface coating layer is composed only of the mixed layer, the effect (3) of the exhaust pipe of the first embodiment of the first aspect of the present invention can be exhibited.

(Examples 10 and 11)
Similarly to the procedure performed in Example 1 of the first embodiment of the first aspect of the present invention, the structure of the surface coating layer was changed as shown in Table 3 to manufacture an exhaust pipe.
In Example 10, on both surfaces of the cylindrical base material, the first layer is 50 μm using the amorphous inorganic material layer raw material composition Z, and the pore concentrated portion forming raw material composition Z is used for the second. A third layer was formed to 50 μm using the raw material composition Z for an amorphous inorganic material layer.
In Example 11, on both surfaces of the surface of the cylindrical base material, the first layer is 50 μm using the mixed layer raw material composition X, the second layer is 50 μm using the pore concentration portion forming raw material composition X, A third layer of 50 μm was formed using the mixed layer raw material composition X.
In any embodiment, the number of pore concentrating portions is one for one surface of the substrate, and the strip portion serving as the pore concentrating portion is the central strip portion of the five strip portions. Met.
That is, in Example 10, a surface coating layer consisting only of an amorphous inorganic material layer was formed, and in Example 11, a surface coating layer consisting only of a mixed layer was formed.
Evaluation similar to Example 1 of 1st embodiment of 1st this invention was performed, and the evaluation result of each Example was shown in Table 4.

The overall judgment of Example 10 was “excellent”, and the overall judgment of Example 11 was “good”.
In any of the examples, since the pore concentrating portion was provided, no peeling occurred in the thermal shock test, and the surface coating layer was prevented from being broken.
Since the exhaust pipe according to Example 10 has a surface coating layer made of only an amorphous inorganic material layer, the volume resistance value of the surface coating layer is 1. It was as high as E + 13 [Ωm].
On the other hand, since the exhaust pipe according to Example 11 has a surface coating layer composed of only a mixed layer and does not have an amorphous inorganic material layer, the volume resistance value of the surface coating layer is 1. It was as low as E + 08 [Ωm]. Therefore, the evaluation result was “good”.

(Third embodiment)
Next, a description will be given of a third embodiment which is an embodiment of the exhaust pipe of the first invention and the method of manufacturing the exhaust pipe of the first invention.
The exhaust pipe of the third embodiment of the first aspect of the present invention differs from the first embodiment of the first aspect of the present invention in the method of forming the pore concentration portion.
In the exhaust pipe of the present embodiment, the surface coating layer is divided into a plurality of layers.
In the step of forming the surface coating layer, the lower surface coating layer and the upper surface coating layer are formed by roughening the surface of the lower layer of the surface coating layer and forming an upper surface coating layer on the roughened surface. A pore is formed at the boundary of the. A portion including the boundary between the lower surface coating layer and the upper surface coating layer including the pores formed in this manner is a pore concentration portion.
The exhaust pipe of the present embodiment also has a pore concentrating portion, and the pore concentrating portion in the present embodiment is the same method as the method of defining the pore concentrating portion in the exhaust pipe of the first embodiment of the first present invention. It is determined using
The “lower layer” refers to a layer on the side close to the substrate of the surface coating layer, and the “upper layer” refers to a layer on the side closer to the surface of the surface coating layer.

FIGS. 7A and 7B are cross-sectional views schematically showing an example of a cross section of the exhaust pipe of the third embodiment of the first invention.
In the exhaust pipe 140 shown in FIG. 7A, the surface coating layer 20 includes a mixed layer 22a, an amorphous inorganic material layer 21, and a mixed layer 22b.
The pore concentration part 23 includes a boundary between the mixed layer 22 b on the side close to the base material 10 (lower layer) and the amorphous inorganic material layer 21.
The strip portion which is the pore concentrating portion 23 in FIG. 7A is a strip portion located second from the bottom among the five strip portions, and can be said to be a strip portion adjacent to the central strip portion. .

In the exhaust pipe 150 shown in FIG. 7B, the structure of the surface coating layer 20 is the same as that of the exhaust pipe shown in FIG. 7A, but the thickness of the mixed layer 22b is the same as that of the amorphous inorganic material layer 21. It is almost equal to the total thickness of the thickness and the thickness of the mixed layer 22a.
Therefore, the strip portion which is the pore concentrating portion 23 is a central strip portion of the five strip portions, and exists at a position where the surface coating layer 20 is divided into two in the thickness direction.

A method for manufacturing the exhaust pipe of this embodiment will be described in the order of steps.
The method for producing an exhaust pipe according to the third embodiment of the first invention includes a step of preparing a metal substrate,
Preparing a raw material composition for forming a surface coating layer;
A method for producing an exhaust pipe, comprising a step of forming a surface coating layer by applying the surface coating layer forming raw material composition a plurality of times on the metal substrate and firing the composition;
In the surface coating layer forming step, a step of forming a lower surface coating layer by applying and baking the raw material composition for forming the surface coating layer at least once,
A step of roughening the surface of the lower surface coating layer, and
The surface coating layer forming raw material composition is applied to the surface of the roughened lower surface coating layer and baked to form an upper surface coating layer. At the same time, the lower surface coating layer and the upper surface coating layer are formed. It is characterized by forming pores between the layers.
Here, the exhaust according to the third embodiment of the first invention is taken as an example in the case of manufacturing the exhaust pipe 140 of the third embodiment of the first invention schematically shown in FIG. A method of manufacturing the tube will be described.
8 (a), 8 (b) and 8 (c) are cross-sectional views schematically showing a part of the process for manufacturing the exhaust pipe of the third embodiment of the first invention.
(1) Substrate, raw material composition for mixed layer and raw material composition for amorphous inorganic material layer in the same manner as in the manufacturing steps (1) to (3) of the exhaust pipe of the first embodiment of the first invention Prepare the product.

(2) A lower surface coating layer (mixed layer) is formed on the substrate in the same manner as in the exhaust pipe manufacturing steps (5) to (6) of the first embodiment of the first aspect of the present invention.
FIG. 8A shows a state in which the mixed layer 22 b is formed on the base material 10.

(3) A roughening treatment is applied to the surface of the lower surface coating layer.
FIG. 8B shows a state in which the surface of the mixed layer 22b has been roughened. As a roughening method, sandblasting, etching, or the like can be used.
The surface roughness Rz _JIS of the roughened surface is preferably 0.1 to 100 μm.
The surface roughness Rz _JIS of the roughened surface can be measured according to JIS B 0601 (2001).
When the surface roughness Rz _JIS of the roughened surface is less than 0.1 μm, pores may not be sufficiently formed between the lower surface coating layer and the upper surface coating layer. The relaxation effect of is reduced. Further, when the surface roughness Rz _JIS of the roughened surface exceeds 100 μm, the adhesion area between the lower surface coating layer and the upper surface coating layer becomes small, and therefore the lower surface coating layer and the upper surface coating layer Adhesion decreases.
The surface roughness Rz _JIS of the roughened surface can be measured according to JIS B 0601 (2001) using Handy Surf E-35B manufactured by Tokyo Seimitsu.

(4) A surface coating layer forming raw material composition (amorphous inorganic material layer raw material composition) is coated on the surface of the lower surface coating layer subjected to the roughening treatment, dried, and then heated and fired. An amorphous inorganic material layer is formed.
FIG. 8C shows a state in which the amorphous inorganic material layer 21 is formed on the mixed layer 22b.
When an amorphous inorganic material layer is formed on the surface of the lower surface coating layer (mixed layer) subjected to the roughening treatment, pores can be formed at the boundary between the two layers. Therefore, in the exhaust pipe manufacturing method according to the present embodiment, the pore concentrating portion 23 is formed at a position including the roughened surface.

(5) An upper surface coating layer (mixed layer) is formed on the substrate in the same manner as in the exhaust pipe manufacturing process (8) of the first embodiment of the first invention (not shown).
By the above procedure, the exhaust pipe of the present embodiment (the exhaust pipe 140 schematically shown in FIG. 7A) can be manufactured.

In addition, the exhaust pipe 140 shown to Fig.7 (a) is only an example of the exhaust pipe of 3rd embodiment of 1st this invention, and is in the surface coating layer of the exhaust pipe of 3rd embodiment. The position of the pore concentration portion is not limited to the position including the boundary between the lower mixed layer and the amorphous inorganic material layer.
Moreover, the surface coating layer may consist of only an amorphous inorganic material layer or a mixed layer like the exhaust pipe of the second embodiment.

The exhaust pipe of this embodiment can exhibit the effects (1) to (5) of the exhaust pipe of the first embodiment of the first invention. Moreover, the manufacturing method of the exhaust pipe of this embodiment can exhibit the following effects.
(7) In the exhaust pipe manufacturing method of the present embodiment, when forming the surface coating layer, a step of roughening the surface of the lower surface coating layer is performed. When the raw material composition for forming the upper surface coating layer is applied to the surface of the roughened lower surface coating layer, all the concave portions of the roughened surface on the surface of the lower surface coating layer are formed. However, a space remains between the concave portion of the roughened surface on the surface of the lower surface coating layer and the raw material composition for forming the upper surface coating layer. Since the space becomes pores after firing, independent pores localized at the boundary between the lower surface coating layer and the upper surface coating layer can be formed. And the exhaust pipe which has a pore concentration part in the desired position of a surface coating layer can be manufactured.

(Example 12)
In the same manner as the procedure performed in Example 1 of the first embodiment of the first aspect of the present invention, a base material, a mixed layer raw material composition X, and an amorphous inorganic material layer raw material composition Z were prepared.
First, in the same manner as the procedure performed in Example 1 of the first embodiment of the first aspect of the present invention, the raw material composition X for the mixed layer was applied to the surface of the flat substrate by spray coating, and the inside of the dryer And dried at 70 ° C. for 20 minutes. Subsequently, a surface coating layer (mixed layer, first layer) was formed by heating and baking in air at 850 ° C. for 15 minutes. The thickness of the mixed layer was 20 μm.

Subsequently, the surface of the mixed layer was roughened by sandblasting. The surface roughness Rz _JIS of the surface of the roughened mixed layer was 10 μm.
The surface roughness Rz _JIS of the roughened surface was measured according to JIS B 0601 (2001) using Handy Surf E-35B manufactured by Tokyo Seimitsu Co., Ltd.

Subsequently, on the surface of the mixed layer subjected to the roughening treatment, the raw material composition for the amorphous inorganic material layer is formed by spray coating in the same manner as the procedure performed in Example 1 of the first embodiment of the first invention. Product Z was applied and dried in a dryer at 70 ° C. for 20 minutes. Then, the surface coating layer (amorphous inorganic material layer, 2nd layer) was formed by heat-baking for 15 minutes at 850 degreeC in the air. The thickness of the amorphous inorganic material layer was 20 μm.

Subsequently, the mixed layer raw material composition X was applied to the surface of the amorphous inorganic material layer by spray coating, and dried in a dryer at 70 ° C. for 20 minutes. Subsequently, a surface coating layer (mixed layer, third layer) was formed by heating and baking in air at 850 ° C. for 15 minutes. The thickness of the mixed layer was 20 μm.
An exhaust pipe was manufactured by the above procedure.
Table 5 collectively shows the structure of the surface coating layer of the exhaust pipe manufactured in Example 12.
In the exhaust pipe manufactured in Example 12, the pore concentration portion was present at a position including the boundary between the layer 1 (lower mixed layer on the base material side) and the layer 2 (amorphous inorganic material layer). In Table 5, the position of such a pore concentration portion is indicated as “between layer 1 and layer 2”.
In Table 5, the “roughening” column shows “Yes” when the surface of each layer was roughened, and “None” when the surface was not roughened. The third layer indicated by “Layer 3” is a layer that appears on the surface of the exhaust pipe, and since the surface is not subjected to roughening treatment, the “roughening” column is not provided.

(Examples 13 to 19)
Exhaust pipes were manufactured in the same manner as in Example 12 except that the configuration of the surface coating layer was changed as shown in Table 5.
Examples 13 to 19 differ from Example 12 in the following points.
In Example 13, the first layer is 20 μm using the amorphous inorganic material layer raw material composition Z, the second layer is 20 μm using the mixed layer raw material composition X, and the amorphous inorganic material layer raw material composition The third layer was formed to 20 μm using the object Z.
The roughened surface was formed on the surface of the first layer.
In Example 14, the first layer is 20 μm using the mixed layer raw material composition X, the second layer is 20 μm using the amorphous inorganic material layer raw material composition Z, and the mixed layer raw material composition X is used. The third layer was formed to 20 μm.
The roughened surface was formed on the surface of the second layer.
In Example 15, the first layer is 20 μm using the amorphous inorganic material layer raw material composition Z, the second layer is 20 μm using the mixed layer raw material composition X, and the amorphous inorganic material layer raw material composition The third layer was formed to 20 μm using the object Z.
The roughened surface was formed on the surface of the second layer.
In Example 16, the first layer is 40 μm using the mixed layer raw material composition X, the second layer is 20 μm using the amorphous inorganic material layer raw material composition Z, and the mixed layer raw material composition X is used. The third layer was formed to 20 μm.
The roughened surface was formed on the surface of the first layer.
In Example 17, the first layer is 40 μm using the amorphous inorganic material layer raw material composition Z, the second layer is 20 μm using the mixed layer raw material composition X, and the amorphous inorganic material layer raw material composition The third layer was formed to 20 μm using the object Z.
The roughened surface was formed on the surface of the first layer.
In Example 18, the first layer is 20 μm using the mixed layer raw material composition X, the second layer is 20 μm using the mixed layer raw material composition X, and the third layer using the mixed layer raw material composition X. Was formed to 20 μm.
The roughened surface was formed on the surface of the first layer.
In Example 19, the first layer is 20 μm using the amorphous inorganic material layer raw material composition Z, the second layer is 20 μm using the amorphous inorganic material layer raw material composition Z, and the amorphous inorganic material A third layer of 20 μm was formed using the layer raw material composition Z. The roughened surface was formed on the surface of the first layer.
In Examples 14 and 15, the roughening treatment was performed on the surface of the layer indicated by Layer 2, and a pore concentration portion was formed between Layer 2 and Layer 3.
In Examples 16 and 17, as shown in FIG. 7B, the thickness of the layer 1 is increased to 40 μm, and the roughening treatment is performed on the surface of the layer indicated by the layer 1, whereby the layer 1 to the layer 2 A pore concentration part was formed between them.
That is, the pore concentrating portion was formed at a central strip portion of the five strip portions, that is, at a position where the surface coating layer was divided into two in the thickness direction.
In Example 18, a surface coating layer consisting only of a mixed layer was formed, and in Example 19, a surface coating layer consisting only of an amorphous inorganic material layer was formed.

(Examples 20 to 23)
Exhaust pipes were manufactured in the same manner as in Example 12 except that the configuration of the surface coating layer was changed as shown in Table 5.
Examples 20 to 23 differ from Example 12 in the following points.
In Example 20, the first layer was formed to 50 μm using the mixed layer raw material composition X, and the second layer was formed to 30 μm using the amorphous inorganic material layer raw material composition Z. The third layer was not formed.
The roughened surface was formed on the surface of the first layer.
In Example 21, the first layer was formed to 30 μm using the amorphous inorganic material layer raw material composition Z, and the second layer was formed to 50 μm using the mixed layer raw material composition X. The third layer was not formed.
The roughened surface was formed on the surface of the first layer.
In Example 22, the first layer was formed to 20 μm using the mixed layer raw material composition X, and the second layer was formed to 200 μm using the amorphous inorganic material layer raw material composition Z. The third layer was not formed.
The roughened surface was formed on the surface of the first layer.
In Example 23, the first layer was formed to 100 μm using the amorphous inorganic material layer raw material composition Z, and the second layer was formed to 100 μm using the amorphous inorganic material layer raw material composition Z. The third layer was not formed.
The roughened surface was formed on the surface of the first layer.
In these examples, roughening treatment was performed on the surface of the layer indicated by layer 1 to form a pore concentration portion between layer 1 and layer 2. In these examples, the layer 3 is not provided.
Evaluation similar to Example 1 of 1st embodiment of 1st this invention was performed, and the evaluation result of each Example was shown in Table 6.

The overall judgment of Examples 12 to 17 and Examples 19 to 23 was “excellent”, and the overall judgment of Example 18 was “good”.
In any of the examples, since the pore concentrating portion was provided, no peeling occurred in the thermal shock test, and the surface coating layer was prevented from being broken.
Since the exhaust pipes according to Examples 12 to 17 and Examples 19 to 23 have a surface coating layer made of an amorphous inorganic material layer, the volume resistance value of the surface coating layer is 1. It was higher than E + 10 [Ωm].
On the other hand, since the exhaust pipe according to Example 18 has a surface coating layer composed of only a mixed layer and does not have an amorphous inorganic material layer, the volume resistivity of the surface coating layer is 1. It was as low as E + 08 [Ωm]. Therefore, the evaluation result was “good”.
In any of Examples 12 to 23, since the pore concentration portion was provided, no peeling occurred in the thermal shock test, and the surface coating layer was prevented from being destroyed.

(Fourth embodiment)
Next, a fourth embodiment which is an embodiment of the exhaust pipe of the first invention will be described.
The exhaust pipe of the fourth embodiment of the first aspect of the present invention has two pore concentrating portions, and the pore concentrating portions are present at positions where the surface coating layer is divided into three in the thickness direction. The other structure is the same as that of the exhaust pipe of 1st embodiment of 1st this invention.
FIGS. 9A and 9B are cross-sectional views schematically showing an example of a cross section of the exhaust pipe of the fourth embodiment of the first invention.

In the exhaust pipe 160 shown in FIG. 9 (a), as in the exhaust pipe of the first embodiment of the first aspect of the present invention, a pore concentrating portion is formed by blending a pore former or the like into the surface coating layer raw material composition. Is formed.
In the exhaust pipe 160 shown in FIG. 9A, the surface coating layer includes a mixed layer 22a, an amorphous inorganic material layer 21a, a mixed layer 22b, an amorphous inorganic material layer 21b, and a mixed layer 22c.
The thicknesses of the mixed layer 22a, the amorphous inorganic material layer 21a, the mixed layer 22b, the amorphous inorganic material layer 21b, and the mixed layer 22c are the same. Therefore, each layer of the mixed layer 22a, the amorphous inorganic material layer 21a, the mixed layer 22b, the amorphous inorganic material layer 21b, and the mixed layer 22c can be regarded as five strip portions.
The amorphous inorganic material layer 21a is a pore concentration portion 23a, and the amorphous inorganic material layer 21b is a pore concentration portion 23b.
That is, the number of pore concentrating portions is two with respect to one surface of the base material, and two strip portions adjacent to the mixed layer 22b that is the central strip portion among the five strip portions are amorphous. The inorganic material layer 21 a and the amorphous inorganic material layer 21 b serve as the pore concentration part 23.
It can be said that the pore concentration portion 23a and the pore concentration portion 23b are present at positions where the surface coating layer 20 is divided into three in the thickness direction.

In the exhaust pipe 170 shown in FIG. 9 (b), the pore concentrating portion is formed by roughening the surface of the lower layer of the surface coating layer, similarly to the exhaust pipe of the third embodiment of the first present invention. .
In the exhaust pipe 170 shown in FIG. 9B, the surface coating layer includes a mixed layer 22a, an amorphous inorganic material layer 21, and a mixed layer 22b.
The number of pore concentration portions is two, and the pore concentration portion 23a is a strip portion including a boundary between the mixed layer 22a on the surface side (upper layer) of the surface coating layer and the amorphous inorganic material layer 21, The concentrated portion 23 b is a strip portion including a boundary between the mixed layer 22 b on the side close to the substrate 10 (lower layer) and the amorphous inorganic material layer 21.
The pore concentrating portion 23a and the pore concentrating portion 23b are two strip portions adjacent to the central strip portion of the five strip portions. It exists at a position that is divided into three in the direction.

The exhaust pipe of the present embodiment forms a pore concentrating portion in the exhaust pipe manufacturing method of the first embodiment of the first aspect of the present invention or the exhaust pipe manufacturing method of the third embodiment of the first aspect of the present invention. It can be manufactured in the same manner except that the step (application of the raw material composition for forming the pore concentrating portion or roughening treatment of the surface coating layer) is performed twice (two locations).

The exhaust pipe of the present embodiment is the operation effect (1) to (3), (5) to (7) of the exhaust pipe of the first embodiment of the first invention or the third embodiment of the first invention. Can be demonstrated.
Further, the following effects can be exhibited.
(8) In the exhaust pipe of the present embodiment, the number of pore concentrating portions is two with respect to one surface of the base material, and the strip portions serving as the pore concentrating portions are among the five strip portions. These are two strip portions adjacent to the central strip portion. That is, the pore concentration portion exists at a position where the surface coating layer is divided into three in the thickness direction.
When the pore concentrating portion exists at a position where the surface coating layer is divided into three in the thickness direction, the surface coating layer is divided into three portions having a thickness of 1/3 by the two pore concentrating portions. become. Therefore, the strength of the thermal shock on the surface coating layer becomes the same as that when the thickness of the surface coating layer is thin, and the surface coating layer can be more effectively prevented from being destroyed.

(Example 24)
The exhaust pipe was manufactured by changing the configuration of the surface coating layer as shown in Table 7 in the same manner as the procedure performed in Example 1 of the first embodiment of the first present invention.
Example 24 is different from Example 1 of the first embodiment of the first aspect of the present invention in the following points.
In Example 24, the first layer was 30 μm using the mixed layer raw material composition X, the second layer was 10 μm using the pore-concentrated portion forming raw material composition Z, and the mixed layer raw material composition X was used. The third layer was formed to 20 μm, the pore-concentrated portion forming raw material composition Z was used to form the fourth layer of 10 μm, and the mixed layer raw material composition X was used to form the fifth layer of 30 μm. The fourth layer and the fifth layer were formed by forming a surface coating layer on the third layer in the same manner as the method for forming the first layer to the third layer.
By the above procedure, pore concentrating portions were formed in two places, the second layer and the fourth layer.

(Example 25)
In the same manner as the procedure performed in Example 12 of the third embodiment of the first invention, the structure of the surface coating layer was changed as shown in Table 7 to manufacture an exhaust pipe.
Example 25 differs from Example 12 of the third embodiment of the first invention in the following points.
In Example 25, the first layer is 20 μm using the mixed layer raw material composition X, the second layer is 20 μm using the amorphous inorganic material layer raw material composition Z, and the mixed layer raw material composition X is used. The third layer was formed to 20 μm.
The roughened surface was formed on the surface of the first layer and the surface of the second layer.
As a result, pore-concentrated portions were formed at two locations between layer 1 and layer 2 and between layer 2 and layer 3.
The position where the pore concentration portion includes the boundary between layer 1 (mixed layer on the lower layer on the base material side, first layer) and layer 2 (amorphous inorganic material layer, second layer), and layer 2 and layer 3 ( It existed in the strip part including the boundary of the surface layer (upper layer) mixed layer, the third layer) of the surface coating layer.

In Table 7, the item “pore forming material or roughening” indicates the presence or absence of the pore forming material in the raw material composition for forming the surface coating layer in Example 24, and the presence or absence of the roughening treatment applied to the surface of each layer in Example 25. Is shown.
Evaluation similar to Example 1 of 1st embodiment of 1st this invention was performed, and the evaluation result of each Example was shown in Table 8.

In both Example 24 and Example 25, the evaluation result was “excellent”.
In both Example 24 and Example 25, since the pore concentration portion was provided, no peeling occurred in the thermal shock test, and the surface coating layer was prevented from being destroyed.

(Fifth embodiment)
Next, a fifth embodiment which is an embodiment of the exhaust pipe of the first aspect of the present invention will be described.
The exhaust pipe of the fifth embodiment of the first aspect of the present invention has blind pores partially communicating with the outside of the exhaust pipe in the surface coating layer.
FIG. 10 is a cross-sectional view schematically showing an example of a cross section of the exhaust pipe of the fifth embodiment of the first invention.
An exhaust pipe 180 according to the fifth embodiment of the first invention shown in FIG. 10 has blind pores 34 partially communicating with the outside of the exhaust pipe in the surface coating layer.
The other structure is the same as that of the exhaust pipe 1 of 1st embodiment of 1st this invention shown in FIG.
Blind pores are pores that partially communicate with the outside of the exhaust pipe. In other words, the blind pores indicate portions that are exposed to the surface coating layer and are recessed. The blind pores do not communicate with the outside of the exhaust pipe and the surface of the base material, and are not pores reaching the surface of the base material.

In the exhaust pipe manufacturing method of the first embodiment of the first aspect of the present invention, the exhaust pipe of the present embodiment is used as a surface coating layer forming raw material composition for forming a surface coating layer that is the uppermost layer. It can manufacture by using the raw material composition for pore concentration part formation.

The exhaust pipe of this embodiment can exhibit the effects (1) to (5) of the exhaust pipe of the first embodiment of the first invention.
It is also possible to provide blind pores in the exhaust pipe of the third embodiment of the first invention or the exhaust pipe of the fourth embodiment of the first invention. In that case, the effect (7) of the manufacturing method of the exhaust pipe of the third embodiment of the first aspect of the present invention or the effect (8) of the exhaust pipe of the fourth embodiment of the first aspect of the present invention is exhibited. Can do.

(Sixth embodiment)
The sixth embodiment, which is an embodiment of the exhaust pipe of the second invention, will be described below with reference to the drawings.
The exhaust pipe of the second aspect of the present invention comprises a base material made of metal,
An exhaust pipe provided with a surface coating layer containing an amorphous inorganic material formed on the surface of the substrate,
The surface coating layer has an amorphous inorganic material layer containing an amorphous inorganic material, and a mixed layer containing an amorphous inorganic material and a crystalline inorganic material,
The surface coating layer has independent pores,
The independent pores do not communicate with the outside of the exhaust pipe and the surface of the base material, and the independent pores are localized at the boundary between the amorphous inorganic material layer and the mixed layer. To do.

FIG. 11: is sectional drawing which shows typically an example of the cross section of the exhaust pipe of 6th embodiment of 2nd this invention.
In the exhaust pipe 200 shown in FIG. 11, the surface coating layer 220 includes a mixed layer 222a, an amorphous inorganic material layer 221, and a mixed layer 222b.
The composition of the

mixed layers

222a and 222b in the exhaust pipe of the sixth embodiment of the second invention is the same as the composition of the mixed layer 22 in the first embodiment of the first invention.
The composition of the amorphous inorganic material layer 221 in the exhaust pipe of the sixth embodiment of the second invention is the same as the composition of the amorphous inorganic material layer 21 in the first embodiment of the first invention.
The thickness of the surface coating layer 220 is 25 to 1000 μm.
The surface coating layer 220 has independent pores 233, and the independent pores 233 do not communicate the outside of the exhaust pipe 200 with the surface of the substrate 10.
The independent pores 233 are localized at the boundary between the mixed layer 222b and the amorphous inorganic material layer 221.

Hereinafter, with reference to FIG. 11, it will be described that “independent pores are localized at the boundary between the mixed layer and the amorphous inorganic material layer”.
“Independent pores are localized at the boundary between the mixed layer and the amorphous inorganic material layer” means that the entire surface coating layer is located in a region within 40% of the thickness of the surface coating layer with the center line of the boundary as the center. In the area of the independent pores existing in the above, it means a state in which 60% or more of the independent pores exist as the pore area.

In the exhaust pipe 200 shown in FIG. 11, the surface of the mixed layer 222b is not a smooth surface but a roughened surface, and independent pores 233 exist between the mixed layer 222b and the amorphous inorganic material layer 221.

The boundary portion between the mixed layer and the amorphous inorganic material layer is a portion determined by the following method.
A line 240L passing through the lowest part of the roughened surface of the lower layer (mixed layer 222b in the exhaust pipe 200 shown in FIG. 11) is drawn, and a line 240H passing through the highest part of the roughened surface of the lower layer is drawn. The middle line 240M of the line 240L and the line 240H is drawn.
The middle line 240M determined in this way becomes the center line of the boundary portion.
Here, the line 240L, the line 240H, and the line 240M are parallel lines.

The thickness of the surface coating layer 220 is obtained. The method for determining the thickness of the surface coating layer 220 is a method for determining the thickness of the surface coating layer with the upper surface of the surface coating layer 220 as the starting point and the surface of the substrate as the ending point. This is the same as the method used when determining the strip portion in the form.
Then, a region of 40% of the thickness of the surface coating layer 220 is determined around the center line 240M of the boundary portion. Specifically, an area of 20% of the thickness of the surface coating layer 220 is defined on the upper side around the line 240M, and a boundary line 250H is drawn. Further, an area of 20% of the thickness of the surface coating layer 220 is defined on the lower side around the line 240M, and a boundary line 250L is drawn.
Here, the line 250L, the line 250H, and the line 240M are parallel lines.
“A region within 40% of the thickness of the surface coating layer centering on the center line of the boundary portion” is a region sandwiched between the

lines

250H and 250L, and this region becomes the “boundary portion”.

The area of the independent pores existing in the entire surface coating layer is determined in the same manner as in the method described in the first embodiment of the first invention. In determining the area of the independent pores, the method for determining the “pores” present in the surface coating layer is the same as the method described in the first embodiment of the first invention.
In the exhaust pipe according to the sixth embodiment of the second aspect of the present invention, 60% or more of the independent pores are present in the boundary portion as the area of the independent pores existing in the entire surface coating layer.

In the exhaust pipe of the sixth embodiment of the second aspect of the present invention, pores are localized at the boundary between the lower surface coating layer and the upper surface coating layer.
In the exhaust pipe 200 according to the sixth embodiment of the second invention shown in FIG. 11, the lower surface coating layer is the mixed layer 222 b and the upper surface coating layer is the amorphous inorganic material layer 221.

However, the exhaust pipe of the sixth embodiment of the second invention is the same as the exhaust pipe of the third embodiment of the first invention when the surface coating layer is cut and five strips are defined. It is not always necessary to have the defined pore concentration portion.
FIG. 12 shows a case where the surface covering layer in the exhaust pipe 200 shown in FIG.
In the exhaust pipe 200 shown in FIG. 12, the boundary line between the strip 220D located second from the bottom and the center strip 220C overlaps the center of the boundary, and the mixed layer 222b and the amorphous inorganic material layer 221 overlap. The independent pores 233 are localized at the boundary portion.
In such an embodiment, when the surface coating layer has five strip portions, the strip portion 220D located second from the bottom and the central strip portion 220C are independent of the entire surface coating layer. There may be a case where 30% or more of independent pores do not exist in the pore area. In this case, there is no pore concentrating part defined when the surface coating layer is cut and five strips are defined, and in that case, the exhaust pipe of the third embodiment of the first invention is not provided. . However, since the independent pores 233 are localized at the boundary between the mixed layer 222b and the amorphous inorganic material layer 221, it can be said that the exhaust pipe of the sixth embodiment of the second aspect of the present invention is obtained.
In addition, as in the exhaust pipe according to the third embodiment of the first aspect of the present invention, among the aspects in which the portion including the boundary between the lower surface coating layer and the upper surface coating layer is a pore concentration portion, independent pores The mode localized at the boundary between the amorphous inorganic material layer and the mixed layer is included in the exhaust pipe of the sixth embodiment of the second aspect of the present invention.

A method for manufacturing the exhaust pipe of this embodiment will be described in the order of steps.
The method for producing an exhaust pipe according to the sixth embodiment of the second invention comprises a step of preparing a metal substrate,
Preparing a raw material composition for forming a surface coating layer;
A method for producing an exhaust pipe, comprising a step of forming a surface coating layer by applying the surface coating layer forming raw material composition a plurality of times on the metal substrate and firing the composition;
In the surface coating layer forming step, a step of forming a lower surface coating layer by applying and baking the raw material composition for forming the surface coating layer at least once,
A step of roughening the surface of the lower surface coating layer, and
The surface coating layer forming raw material composition is applied to the surface of the roughened lower surface coating layer and baked to form an upper surface coating layer. At the same time, the lower surface coating layer and the upper surface coating layer are formed. It is characterized by forming pores between the layers.

Here, an exhaust pipe according to the sixth embodiment of the second invention is manufactured by taking as an example the case of manufacturing the exhaust pipe 200 of the sixth embodiment of the second invention shown schematically in FIG. How to do it will be explained.
(1) Substrate, raw material composition for mixed layer and raw material composition for amorphous inorganic material layer in the same manner as in the manufacturing steps (1) to (3) of the exhaust pipe of the first embodiment of the first invention Prepare the product.

(2) The lower surface coating layer (mixed layer) is formed on the substrate in the same manner as in the exhaust pipe manufacturing steps (5) to (6) of the first embodiment of the first invention.

(3) A roughening treatment is applied to the surface of the lower surface coating layer.
As a roughening method, sandblasting, etching, or the like can be used.
The surface roughness Rz _JIS of the roughened surface is preferably 0.1 to 100 μm.
The surface roughness Rz _JIS of the roughened surface can be measured according to JIS B 0601 (2001).
When the surface roughness Rz _JIS of the roughened surface is less than 0.1 μm, pores may not be sufficiently formed between the lower surface coating layer and the upper surface coating layer. The relaxation effect of is reduced. Further, when the surface roughness Rz _JIS of the roughened surface exceeds 100 μm, the adhesion area between the lower surface coating layer and the upper surface coating layer becomes small, and therefore the lower surface coating layer and the upper surface coating layer Adhesion decreases.
The surface roughness Rz _JIS of the roughened surface can be measured according to JIS B 0601 (2001) using Handy Surf E-35B manufactured by Tokyo Seimitsu Co., Ltd.

(4) A surface coating layer forming raw material composition (amorphous inorganic material layer raw material composition) is coated on the surface of the lower surface coating layer subjected to the roughening treatment, dried, and then heated and fired. An amorphous inorganic material layer is formed.
When an amorphous inorganic material layer is formed on the surface of the lower surface coating layer (mixed layer) subjected to the roughening treatment, independent pores can be formed at the boundary between the two layers.
Therefore, in the exhaust pipe manufacturing method of the present embodiment, independent pores localized at the boundary between the mixed layer and the amorphous inorganic material layer are formed.

(5) An upper surface coating layer (mixed layer) is formed on the substrate in the same manner as in the exhaust pipe manufacturing step (8) of the first embodiment of the first invention.
By the above procedure, the exhaust pipe of the present embodiment (exhaust pipe 200 schematically shown in FIG. 11) can be manufactured.

The effects of the exhaust pipe of the present embodiment and the exhaust pipe manufacturing method of the present embodiment will be listed below.
(9) In the exhaust pipe of the present embodiment, the surface covering layer has independent pores, and the independent pores do not communicate the outside of the exhaust pipe with the surface of the base material, and the independent pores. Is localized at the boundary between the amorphous inorganic material layer and the mixed layer.
It is considered that a crack generated in the surface coating layer due to thermal shock first occurs on the surface of the surface coating layer and progresses toward the base material in the thickness direction of the surface coating layer.
When a crack generated in the surface coating layer develops and collides with an independent pore, the crack is prevented from progressing before the independent pore.
If independent pores that do not communicate with the outside of the exhaust pipe and the surface of the base material are localized at the boundary between the amorphous inorganic material layer and the mixed layer, even if a crack occurs on the surface of the surface coating layer, Since the cracks easily collide with the independent pores localized at the boundary between the amorphous inorganic material layer and the mixed layer, the crack propagates more toward the substrate than the boundary between the amorphous inorganic material layer and the mixed layer. Is prevented.
As a result, the surface coating layer can be prevented from being destroyed. Therefore, the exhaust pipe can ensure high insulation.

(10) In the exhaust pipe of this embodiment, the surface coating layer contains a crystalline inorganic material. The crystalline inorganic material contains at least one oxide of manganese, iron, copper, cobalt, chromium, and aluminum.
Since the oxide has a high infrared emissivity, the emissivity of the surface coating layer can be further increased. When the emissivity of the surface coating layer is increased, an exhaust pipe excellent in heat dissipation at high temperatures can be obtained.
In particular, when an aluminum oxide is used, it contributes to an improvement in the insulation of the exhaust pipe.

(11) In the exhaust pipe of this embodiment, the thickness of the surface coating layer is 25 to 1000 μm.
When the thickness of the surface coating layer is less than 25 μm, sufficient insulation cannot be secured when used as an exhaust pipe. On the other hand, when the thickness of the surface coating layer exceeds 1000 μm, the strength of the thermal shock to the surface coating layer becomes strong, and the surface coating layer is easily broken.

(12) In the exhaust pipe manufacturing method of the present embodiment, when the surface coating layer is formed, a step of roughening the surface of the lower surface coating layer is performed. When the raw material composition for forming the upper surface coating layer is applied to the surface of the roughened lower surface coating layer, all the concave portions of the roughened surface on the surface of the lower surface coating layer are formed. However, a space remains between the concave portion of the roughened surface on the surface of the lower surface coating layer and the raw material composition for forming the upper surface coating layer. And since the said space becomes an independent pore after baking, the independent pore localized at the boundary part of the lower surface coating layer and the upper surface coating layer can be formed.
An exhaust pipe in which independent pores are localized at the boundary between the amorphous inorganic material layer and the mixed layer of the surface coating layer can be manufactured.

(Seventh embodiment)
Next, a seventh embodiment which is an embodiment of the exhaust pipe of the second invention will be described.
In the exhaust pipe of the seventh embodiment of the second aspect of the present invention, there are two boundary portions where the independent pores are localized.
FIG. 13: is sectional drawing which shows typically an example of the cross section of the exhaust pipe of 7th embodiment of 2nd this invention.

In the exhaust pipe 270 shown in FIG. 13, similarly to the exhaust pipe of the sixth embodiment of the second aspect of the present invention, by roughening the surface of the lower layer of the surface coating layer, the amorphous inorganic material layer and the mixed layer are formed. Independent pores are formed at the boundary.
In the exhaust pipe 270 shown in FIG. 13, the surface coating layer includes a mixed layer 222a, an amorphous inorganic material layer 221, and a mixed layer 222b.
The number of boundary portions determined using the method described in the sixth embodiment of the second invention is two.
In the present embodiment, the center lines 240Ma and 240Mb of the boundary portion are determined in the same manner as the method described in the sixth embodiment of the second invention. Then, two regions of 40% of the thickness of the surface coating layer 220 are determined with the center lines 240Ma and 240Mb of the boundary portions as the centers.
The “region within 40% of the thickness of the surface coating layer centering on the center line of the boundary” defined in this way is the region sandwiched between the lines 250Ha and 250La, and between the lines 250Hb and 250Lb. This area
That is, the region sandwiched between the lines 250Ha and 250La and the region sandwiched between the lines 250Hb and 250Lb are both boundary portions.

The exhaust pipe of this embodiment has a plurality (two) of boundary portions. When there are multiple boundary portions in the surface covering layer, the area of the independent pores existing in each boundary portion is calculated, and the total area of the independent pores existing in each boundary portion is present in the entire surface covering layer. What is 60% or more of the area of the independent pores is the exhaust pipe of the second invention.
In the exhaust pipe of the present embodiment, the sum of the areas of the independent pores existing at the two boundary portions (the region sandwiched between the lines 250Ha and 250La and the region sandwiched between the lines 250Hb and 250Lb) is the surface. It is 60% or more of the area of the independent pores existing in the entire coating layer.

The exhaust pipe of the present embodiment is manufactured in the same manner as in the exhaust pipe manufacturing method of the sixth embodiment of the second invention, except that the surface coating layer is roughened twice (two locations). can do.

The exhaust pipe of this embodiment can exhibit the effects (9) to (11) of the exhaust pipe of the sixth embodiment of the second invention.

(Eighth embodiment)
Next, an eighth embodiment which is an embodiment of the exhaust pipe of the second invention will be described.
The exhaust pipe according to the eighth embodiment of the second aspect of the present invention has blind pores partially communicating with the outside of the exhaust pipe in the surface coating layer.
FIG. 14 is a cross-sectional view schematically showing an example of a cross section of the exhaust pipe of the eighth embodiment of the second invention.
The exhaust pipe 280 according to the eighth embodiment of the second aspect of the present invention shown in FIG. 14 has blind pores 34 partially communicating with the outside of the exhaust pipe in the surface coating layer.
The other structure is the same as that of the exhaust pipe 200 of 6th embodiment of 2nd this invention shown in FIG.
Blind pores are pores that partially communicate with the outside of the exhaust pipe. In other words, the blind pores indicate portions that are exposed to the surface coating layer and are recessed. The blind pores do not communicate with the outside of the exhaust pipe and the surface of the base material, and are not pores reaching the surface of the base material.

In the exhaust pipe manufacturing method of the sixth embodiment of the second aspect of the present invention, the exhaust pipe of the present embodiment is a surface coating layer forming raw material composition for forming a surface coating layer that is the uppermost layer. It can manufacture by using the raw material composition for pore concentration part formation.

(Other embodiments)
In the surface coating layer in the exhaust pipe of the present invention, there are no pores penetrating the surface coating layer, that is, pores communicating with the outside of the exhaust pipe and the surface of the substrate.
When there are pores penetrating the surface coating layer, the surface of the base material made of metal is exposed, so moisture enters from the exposed surface, and the surface of the base material is exposed from the exposed surface. There is a possibility of rusting. When there are no pores penetrating the surface coating layer, the surface of the substrate is not exposed, so that moisture does not enter and the metal substrate is prevented from being rusted.
Also, in order to prevent the presence of pores penetrating the surface coating layer, a method of coating the surface coating layer forming raw material composition a plurality of times on the surface of the substrate is used when forming the surface coating layer. Is preferred.
In addition, the thickness of the surface coating layer may be increased so that there are no pores penetrating the surface coating layer.

In the raw material composition for forming a mixed layer which is a raw material composition for forming a surface coating layer, the blending amount of the amorphous inorganic material is based on the total weight of the amorphous inorganic material powder and the crystalline inorganic material powder, A desirable lower limit is 50% by weight and a desirable upper limit is 99.5% by weight.
If the blending amount of the amorphous inorganic material is less than 50% by weight, the amount of the amorphous inorganic material that contributes to the adhesion between the surface coating layer and the substrate is too small, so the surface coating layer falls off in the manufactured exhaust pipe. Sometimes. On the other hand, if the blending amount of the amorphous inorganic material exceeds 99.5% by weight, the amount of the crystalline inorganic material is decreased, and the heat dissipation of the exhaust pipe may be lowered. The more desirable lower limit of the blending amount of the amorphous inorganic material is 60% by weight, and the more desirable upper limit is 95% by weight.

In the raw material composition for forming a mixed layer, which is a raw material composition for forming a surface coating layer, the blending amount of the crystalline inorganic material is desirable with respect to the total weight of the amorphous inorganic material powder and the crystalline inorganic material powder. The lower limit is 0.5% by weight, and the desirable upper limit is 50% by weight.
When the amount of the crystalline inorganic material is less than 0.5% by weight, the amount of the crystalline inorganic material having heat dissipation is too small, and the heat dissipation of the exhaust pipe may be lowered. On the other hand, when the blending amount of the crystalline inorganic material exceeds 50% by weight, the amount of the amorphous inorganic material that contributes to the adhesion between the surface coating layer and the substrate decreases, and the surface coating layer falls off in the manufactured exhaust pipe. There are things to do.

As a dispersion medium which can be mix | blended with the raw material composition for surface coating layer formation, organic solvents, such as water and methanol, ethanol, acetone, etc. are mentioned, for example. The mixing ratio of the mixed powder and the dispersion medium is not particularly limited. For example, the dispersion medium is desirably 50 to 150 parts by weight with respect to 100 parts by weight of the mixed powder. This is because the viscosity is suitable for application to the exhaust pipe substrate.
As an organic binder which can be mix | blended with the raw material composition for surface coating layer formation, polyvinyl alcohol, methylcellulose, ethylcellulose, carboxymethylcellulose etc. can be mentioned, for example. These may be used alone or in combination of two or more.
Moreover, you may use a dispersion medium and an organic binder together.

In addition to a flat plate, a semi-cylinder, and a cylindrical shape, the shape of the outer edge of the cross section may be an arbitrary shape such as an ellipse or a polygon.

In the exhaust pipe of the present invention, the surface coating layer does not necessarily have to be formed on the entire outer peripheral surface of the base material, and only needs to be formed only on a portion that is insulated from the current-carrying portion (electrode). .

The exhaust pipe of the first aspect of the present invention includes a base material made of metal and a surface coating layer containing an amorphous inorganic material formed on the surface of the base material, and a cross section parallel to the thickness direction of the exhaust pipe When the portion of the surface coating layer in the microscope image is cut into a strip shape having a thickness after cutting of 10 μm in a direction perpendicular to the thickness direction of the exhaust pipe, a plurality of strip portions are defined. It is an essential component that at least one strip portion of the plurality of strip portions is a pore concentrating portion in which the proportion of pores in a certain strip portion is larger than that of other strip portions.
The exhaust pipe of the second aspect of the present invention includes a base material made of a metal and a surface coating layer containing an amorphous inorganic material formed on the surface of the base material, and the surface coating layer is made of an amorphous material. An amorphous inorganic material layer containing a porous inorganic material, and a mixed layer containing an amorphous inorganic material and a crystalline inorganic material, the surface coating layer has independent pores, and the independent pores are In addition, the outside of the exhaust pipe does not communicate with the surface of the base material, and the independent pores are essential components that are localized at the boundary between the amorphous inorganic material layer and the mixed layer. .
Various constituents detailed in the first to eighth embodiments and other embodiments (for example, the presence or absence of a crystalline inorganic material layer, the presence or absence of a mixed layer, the addition of a pore former, etc.) are included in such essential components. The desired effect can be obtained by appropriately combining the formed pores and the pores formed by the roughening treatment.

1, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 270, 280

Exhaust pipe

10, 11, 12

Base material

20, 220

Surface Coating layer

20A, 20B, 20C, 20D,

20E Strip portion

21, 21a, 21b, 221 Amorphous

inorganic material layer

22, 22a, 22b, 22c, 222a, 222b

Mixed layer

23, 23a, 23b Pore concentration portion 31 Amorphous Inorganic material 32 Crystalline

inorganic material

33, 233 Independent pore 34 Blind pore

Claims

A base material made of metal;
An exhaust pipe provided with a surface coating layer containing an amorphous inorganic material formed on the surface of the substrate,
There are pores in the surface coating layer,
A portion of the surface coating layer in the electron microscope image having a magnification of 500 times in a cross section parallel to the thickness direction of the exhaust pipe is perpendicular to the thickness direction of the exhaust pipe, and the thickness after cutting is the surface coating layer When the five strips are defined by cutting to be 1/5 of the thickness of
Of the area of the pores present in the entire surface coating layer, there is at least one pore concentration portion that is a strip portion in which pores of 30% or more exist as pore areas,
The strip portion which is the pore concentration portion is a central strip portion of five strip portions or one or two strip portions adjacent to the central strip portion,
The exhaust pipe, wherein the pores present in the surface coating layer have independent pores, and the independent pores do not communicate with the outside of the exhaust pipe and the surface of the substrate.
2. The exhaust pipe according to claim 1, wherein the pore concentration portion has a pore ratio (B / A) that is a ratio of an area (B) occupied by pores to an area (A) of the strip portion of 0.02 or more.
The exhaust pipe according to claim 1, wherein the surface coating layer further includes a crystalline inorganic material.
The surface coating layer has an amorphous inorganic material layer containing an amorphous inorganic material, and a mixed layer containing an amorphous inorganic material and a crystalline inorganic material, and the pore concentration portion is formed of the amorphous material. The exhaust pipe according to claim 3, comprising a boundary between a porous inorganic material layer and the mixed layer.
The exhaust pipe according to claim 3 or 4, wherein the crystalline inorganic material contains at least one oxide of manganese, iron, copper, cobalt, chromium, and aluminum.
The number of the pore concentrating portions is one for one surface of the base material, and the strip portion serving as the pore concentrating portion is a central strip portion of five strip portions. The exhaust pipe according to any one of 1 to 5.
The number of pore concentrating portions is two for one surface of the base material, and the strip portion serving as the pore concentrating portion is adjacent to the central strip portion of the five strip portions. The exhaust pipe according to any one of claims 1 to 5, which has two strip portions.
The exhaust pipe according to any one of claims 1 to 7, wherein the thickness of the surface coating layer is 25 to 1000 袖 m.
The exhaust pipe according to any one of claims 1 to 8, wherein a thermal conductivity of the surface coating layer at room temperature is 0.1 to 2 W / m · K.
The exhaust pipe according to any one of claims 1 to 9, wherein a volume resistance value of the exhaust pipe is 10 7 to 10 14 Ωm.
The exhaust pipe according to any one of claims 1 to 10, wherein the surface coating layer is formed by coating the raw material composition for forming the surface coating layer a plurality of times.
The exhaust pipe according to any one of claims 1 to 11, wherein the surface coating layer further has blind pores, part of which communicates with the outside of the exhaust pipe.
A base material made of metal;
An exhaust pipe provided with a surface coating layer containing an amorphous inorganic material formed on the surface of the substrate,
The surface coating layer has an amorphous inorganic material layer containing an amorphous inorganic material, and a mixed layer containing an amorphous inorganic material and a crystalline inorganic material,
The surface coating layer has independent pores;
The independent pores do not communicate with the outside of the exhaust pipe and the surface of the base material, and the independent pores are localized at the boundary between the amorphous inorganic material layer and the mixed layer. Exhaust pipe.
The exhaust pipe according to claim 13, wherein the surface coating layer further has blind pores, part of which communicates with the outside of the exhaust pipe.
Preparing a metal substrate;
Preparing a raw material composition for forming a surface coating layer;
A method for producing an exhaust pipe, comprising: applying a surface coating layer forming raw material composition on the metal substrate, and forming a surface coating layer by firing;
In the step of preparing the surface coating layer forming raw material composition, the amorphous inorganic material layer raw material composition containing an amorphous inorganic material and / or a mixed layer containing an amorphous inorganic material and a crystalline inorganic material A raw material composition is prepared, and a pore-forming material is prepared by blending a pore-forming material with the amorphous inorganic material layer raw material composition or the mixed layer raw material composition,
In the surface coating layer forming step, the pore concentration portion forming raw material composition is applied at least once and baked to form pores in the surface coating layer, and the amorphous inorganic material layer raw material composition or the A method for producing an exhaust pipe, wherein the mixed layer raw material composition is applied at least once.
Preparing a metal substrate;
Preparing a raw material composition for forming a surface coating layer;
A method for producing an exhaust pipe, comprising a step of forming a surface coating layer by applying the surface coating layer forming raw material composition a plurality of times on the metal substrate and firing the composition;
In the surface coating layer forming step, a step of forming a lower surface coating layer by applying and firing the raw material composition for forming the surface coating layer at least once,
Roughening the surface of the lower surface coating layer, and
A surface coating layer forming raw material composition is applied to the surface of the roughened lower surface coating layer and baked to form an upper surface coating layer. At the same time, the lower surface coating layer and the upper surface coating layer are formed. A method for manufacturing an exhaust pipe, wherein pores are formed between layers.