JP3406540B2 - Glass coating - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass coated body in which the surface of a substrate is covered with a glass layer, and more particularly to a glass coated body in which a layer exhibiting heat insulating properties is formed on the surface of the substrate.

[0002]

2. Description of the Related Art In an exhaust system member with which the exhaust gas of an internal combustion engine such as a vehicle engine comes into contact, it is required to reduce the amount of heat stored in the member to achieve early warm-up and early activation of the catalyst. There is. In addition, it has become necessary to improve heat resistance in response to the rise in exhaust gas temperature accompanying the improvement in combustion efficiency. Therefore, it has been studied to improve the heat insulating performance by subjecting the metal base material of the exhaust system member to the surface treatment. Specifically, a layer mainly made of a ceramic material is formed on the surface of a metal base material. Generally, a heat insulating layer is formed by forming a film with a ceramic material having a low thermal conductivity, for example, a coating material having a composition of 50% by weight of Fe ₂ O ₃ , 30% by weight of ZrO _{2 and} 20% by weight of Cr. . However, such a heat insulating layer requires a film thickness of about 1000 μm.

There is also an attempt to use a glass layer in which highly radiative particles are dispersed in glass having high heat resistance as a heat insulating layer. This technique is described in Japanese Patent Laid-Open No. 10-287443. According to this heat insulating layer, high heat insulating performance is expected due to the heat insulating property of the glass layer as the mother layer and the radiant property of the radiant particles. In order for this glass layer to exhibit stable heat insulation performance, it is necessary to bond the glass layer to the substrate with good adhesion. However, during high temperature use, an intermetallic compound of Si and a base metal is formed and deposited at the interface between the glass layer and the base due to diffusion of the Si component in the glass layer toward the metal base. There is. It has been found that the glass layer tends to peel off when such an intermetallic compound is formed.

[0004]

Therefore, according to the present invention,
It is an object of the present invention to provide a glass cover provided with a glass layer in a state of good adhesion.

[0005]

[Means for Solving the Problems] Even if the glass layer components are diffused during use at high temperature, the present inventors can maintain a good adhesion between the glass layer and the substrate. The layer was found and the present invention was completed. That is, the present invention is
On the surface of the metal substrate, metal atoms that can diffuse to the substrate side (hereinafter,
Simply called diffusion metal. ) A glass coated body having a glass layer via an intermediate layer including a diffusion layer of 4). According to this glass cover, since the diffusion layer of the diffusion metal is provided between the base material and the glass layer, the adhesion of the glass layer is secured even if the components of the glass layer diffuse into the intermediate layer. Further, the intermediate layer has good adhesion to the substrate.

In the present invention, the intermediate layer preferably contains the constituent components of the glass layer. According to such an intermediate layer, good adhesion with the glass layer is obtained, and precipitation of intermetallic compounds due to diffusion of the components of the glass layer is effectively suppressed. Further, it is preferable that the diffusion metal is also a constituent component of the glass layer (in particular, a metal of a metal oxide that constitutes the glass layer).

It is also preferable to provide an oxide layer of a diffusion metal on the base material side of the intermediate layer. Oxidation resistance is improved by the oxide layer, and peeling of the glass layer due to oxidation is suppressed. In addition, the metal oxide in this oxide layer,
It is more preferable that the metal oxide corresponds to the metal oxide forming the glass layer.

[0008] It is also preferable that the intermediate layer contains aluminum as the diffusion metal, and the metallic base material contains iron. When the diffusion metal is aluminum, a good diffusion layer can be obtained between the diffusion metal and the base material containing iron.

It is preferable that the glass layer has a glass structure and radiative particles dispersed in the glass structure. It is more preferable that the emissive particles include emissive particles having a coating layer having a silicon dioxide content higher than that of the dense portion of the glass structure. According to this mode, high heat insulation performance is obtained by the radiative particles in the glass structure. Therefore, the thin glass layer provides sufficient heat insulation performance.

It is preferable that the glass cover is an exhaust system member. Since good heat insulation performance is obtained in the exhaust system member, early warm-up and early activation of the catalyst are possible, and the heat resistance of the exhaust system member is secured.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. The glass coated body of the present invention includes an intermediate layer having a diffusion layer of a diffusion metal on the surface of a metal substrate, and a glass layer on the intermediate layer. A glass cover 2 which is an embodiment of the present invention will be described with reference to FIG. The metal base material 4 is not particularly limited, and various simple metals, alloys, and the like can be used. A metal base material containing iron (Fe) is preferable. More preferably, various steel materials mainly composed of iron. Also, the glass cover 2
However, in the case of a member for use in which heat resistance is required, including an exhaust system member such as an exhaust pipe, the base material 4 is cast iron, various stainless steel,
Cast steel or the like is preferable. As the cast iron, spheroidal graphite cast iron is preferable. Such cast iron has a tensile strength of 400 N /
mm ² or more, yield strength of 250 N / mm ² or more, elongation of 18
% Or more is preferable. Specifically, JIS G
5502 and the like.

The glass layer 6 is preferably a borosilicate glass containing silicon dioxide as a main component and boric acid. For example, the silicon dioxide content is 96 wt
% Of high-purity silica glass to which several wt% of boron oxide is added and fired, borosilicate glass having a silicon dioxide content of about 81 wt%, and the like. The glass layer 6 is preferably made of, for example, borosilicate glass as a whole, and has a glass mother phase 8 having a coefficient of thermal expansion of about 2 × 10 ⁻⁶ / ° C., and this mother phase 8 contains SiO ₂ 96
%, B ₂ O ₃ 3%, Al ₂ O ₃ 0.4%, a porous portion 10 made of high-purity silica-containing borosilicate glass derived from high-purity silica glass, and the high-purity silica glass and boron oxide. Narrow silica content 82% dense part 12
And have.

Further, more preferably, the glass layer contains radiative particles 14. Radiant particle 14
Is preferably contained in about 2.5 wt% in the entire glass layer 6. The radiative particles 14 are, for example, at least one selected from silicon borides such as silicon tetraboride (SiB ₄ ) or silicon hexaboride, molybdenum disilicide, silicon carbide, iron oxide, silicon nitride, and chromium oxide. Formed from. Preferred is silicon boride. And, more preferably, a coating layer 16 made of silica glass is provided on the surface. The coating layer 16 preferably contains silica at a concentration higher than the silica content of the matrix 8 at the interface with the particles 14, that is, the dense portion 12. Specifically, it is preferable to contain 85 wt% or more of silica. The coating layer 16 is
It is preferably about 0.1 μm to several μm. The thickness of such a glass layer 6 is preferably 10 to 100 μm, and more preferably 25 μm to 50 μm.

The intermediate layer 20 is made of such a metal base material 4.
And the glass layer 6 are formed. The intermediate layer 20 contains a metal capable of diffusing to the metal base material 4 side, that is, a diffusion metal. The intermediate layer is provided with the diffusion layer 22 having the concentration distribution of the diffusion metal. As the diffusion metal, aluminum (Al), chromium (Cr) and the like are preferable when the base material 4 contains iron, particularly when iron is the main constituent, although it depends on the kind of the base material 4. Aluminum is particularly preferable.

The intermediate layer 20 preferably contains the components contained in the glass layer 6. If the glass cover 2 is used at a high temperature, the glass layer 6 is changed from the glass layer 6 to the intermediate layer.
Although the component of (4) is diffused, it is preferable that the component of the glass layer 6 is contained in the intermediate layer 20 in advance. In such cases,
Adhesion with the glass layer 6 is easily secured. As such a component, a metal of a metal oxide other than silicon dioxide forming the glass layer 6 is more preferable. In particular, it is preferable that the diffusion metal is also a metal contained in the glass layer 6. When the glass layer 6 contains aluminum oxide, the diffusion metal is preferably aluminum.

Further, the intermediate layer 20 diffuses the metal from the base material 4 at the time of applying the intermediate layer 20 and contains a component which is not originally contained in the composition of the intermediate layer 20, but The base material 4 as a component of the intermediate layer 20 (preliminarily).
The metal contained in can be included. For example, when the base material 4 is cast iron, iron, silicon, etc. can be contained. In addition, the intermediate layer 20 may contain a component that is not included in the base material 4 and the glass layer 6.

By providing such an intermediate layer 20, even if the components of the glass layer 6 are diffused to the base material 4 side, they are diffused in the diffusion layer 22 having the concentration distribution of the diffusion metal.
Contact with high concentrations of base metal is prevented. Further, due to such diffusion, the coefficient of thermal expansion between the glass layer 6 and the intermediate layer 20 is favorably graded.

Further, in the diffusion layer 22 of the intermediate layer 20, the metals in the base material 4 are also mutually diffused. That is, these alloy layers are formed in the diffusion layer 22. Therefore, the intermediate layer 20 is in good contact with the base material.

In particular, it is preferable that the diffusion metal oxide layer 24 is formed on the glass layer 6 side of the diffusion layer 22.
The oxide layer 24 suppresses the oxidation of the base material 4. Further, the oxide layer 24 preferably matches the oxide of a metal other than silicon contained in the glass layer 6. In this case, the glass layer 6 and the intermediate layer 20 are diffused during use.
And are well coupled through the oxide layer 24.

By providing the intermediate layer 20, for example, near the transformation temperature of the base metal (cast iron (transformation temperature 73
0 ° C.), for example, even when exposed to 700 ° C. and 850 ° C.) for a long time (for example, 50 to 100 hours), diffusion of the base material component into the diffusion layer 22 is observed, but the glass layer 6
The peeling of the glass layer 6 is suppressed. As a result, the oxidation of the base metal is also suppressed. Also, the adhesion strength between the glass layer 6 and the intermediate layer 20 does not change significantly above and below the transformation temperature. Further, for example, cold shock stress (for example, room temperature to 850 ° C.) that passes through the transformation temperature of the base metal (about 730 ° C. in the case of cast iron).
The peeling of the glass layer is suppressed even in the case of giving. As a result, the oxidation of the base metal is also suppressed. Further, even when a strong thermal shock stress is applied to cause cracks in the intermediate layer 20, peeling of the glass layer 6 is suppressed.

The thickness of the intermediate layer 20 is 10-2.
00 μm is preferable, and more preferably 25 to 150 μm.
m. Further, the diffusion layer 22 in particular has a thickness of 25 to 100 μm.
Is preferred. Further, the oxide layer 24 of the diffusion metal has a thickness of about several μm. A diffusion metal simple substance layer may be provided between the diffusion metal oxide layer 24 and the diffusion layer 22.

The substrate 4, the glass layer 6 and the intermediate layer 2
As a preferable combination of 0, the base material 4 contains Fe and the glass layer 6 is SiO ₂ —B ₂ O ₃ —Al ₂ O ₃
This is a case where the intermediate layer 20 includes an Al diffusion layer 22 and an Al oxide layer 24. More preferably,
An Al simple substance layer is provided between the Al diffusion layer and the Al oxide layer. This Al diffusion layer contains an Al-Fe alloy layer. In the glass covering 2 of such a combination, for example, the base material 4 is cast iron (transformation temperature of about 730 ° C.)
In the case of 50 to 100 at 700 ° C and 850 ° C, respectively.
When exposed for about time, diffusion of the base material component to the intermediate layer 20 was observed, but there was no noticeable change in the glass layer, and peeling of the glass layer 6 was suppressed. As a result, the oxidation of the base metal was also suppressed. Further, the glass layer 6 and the intermediate layer 2
The adhesion strength of 0 did not change significantly above and below the transformation temperature. This indicates that the glass cover 2 is suitable for use as an exhaust system member.

Further, for example, in the case of the glass covering 2 of the above combination in which the base material 4 is the cast iron (transformation temperature of about 730 ° C.), the thermal shock stress such that it passes the transformation temperature, for example, room temperature to 850. Even when the temperature change of ° C was given about 1000 times, the peeling of the glass layer 6 was suppressed. As a result, the oxidation of the base metal was also suppressed. Further, by imparting such a strong thermal shock stress, the intermediate layer 20
Even if cracks were generated in the glass, peeling of the glass layer 6 was suppressed. This indicates that the glass cover 2 is suitable for use as an exhaust system member.

The glass coated body of the present invention has a good heat insulating property and is provided with a heat insulating layer which is not easily peeled off even at a high temperature. Therefore, the glass coated body is used particularly in a portion exposed to a high temperature and is required to have heat resistance. It is preferable to use
More preferably, it is preferably used for a member that is repeatedly subjected to thermal shock stress. In particular, it is preferably used for an exhaust system member such as an exhaust pipe that comes into contact with exhaust gas of an internal combustion engine of a vehicle or the like.

When the glass layer is radiative such as containing radiative particles, the heat insulating effect of the glass layer is a synergistic effect of the heat blocking effect and the radiative cooling effect, so that the layer thickness is 100 μm. Even below, a sufficient heat insulating effect can be obtained. In particular, a thin glass layer (for example, 25 μm to 50 μm)
Since a sufficient heat insulating effect can be obtained by the glass layer), even when the glass layer is broken, there is an advantage that the function imparted to the glass cover is unlikely to be hindered by the fragments of the glass layer. In particular, in the exhaust system member, even when the surface layer is peeled off, the exhaust system is less likely to cause any trouble. Further, the exhaust member refers to, for example, parts such as an exhaust pipe, an exhaust engine valve, a piston, an exhaust switching valve, an exhaust throttle valve, an EGR passage, a muffler, a turbocharger and a combustion chamber.

Next, a method for manufacturing such a glass cover will be described. In order to form the intermediate layer on the surface of the base material, it is possible to form a film containing a diffusion metal and then heat-treat it to diffuse it, or use a hot dipping method or a diffusion infiltration method. When the heat treatment is performed after forming the metal film, the diffusion metal is formed by a thermal spraying method, a physical vapor deposition method, a chemical vapor deposition method, a sputtering method, or the like, and then heat treatment is performed to form a diffusion layer by thermal diffusion. The heat treatment is performed at a temperature and for a time such that mutual diffusion of the diffusion metal and the base metal is performed.

In the case of the hot dipping method, the base material is dipped in a molten liquid containing the diffusion metal and the molten diffusion metal is solidified on the surface of the base material to coat the surface of the base material and at the same time to form the diffusion metal. A diffusion layer (alloy layer) is formed by mutual diffusion with the base metal. Hot dipping is convenient for providing a diffusion layer of aluminum to steel or cast iron. Further, it is convenient when it is desired to provide a diffusion layer on the inner surface or in a place where it is difficult to form a coating by a thermal spraying method. From this point of view, it is particularly preferable to be applied to an exhaust system member such as an exhaust pipe.

In hot dipping, an alloy layer (diffusion layer) of a base metal and a diffusion metal is formed in a plating bath. Further, when the metal is taken out from the plating bath, the molten metal adheres and the surface thereof is naturally oxidized to form an oxide layer. It is also possible to suppress the formation of the oxide layer.

The diffusion permeation method is a method in which a metal is diffused and permeated into a substrate from a gas phase or a solid phase. For example, the base material is embedded in aluminum powder and alumina powder and heated. The composition in the solid phase is appropriately selected. After being taken out from the powder, it may be further heated to promote diffusion.

When the metal coating is applied to the surface of the base material in this way, it is preferable that the metal surface is subjected to pretreatment suitable for each treatment such as degreasing, acid cleaning and drying. Also,
The metal coating may contain a base metal or a metal contained in the glass layer, instead of a single diffusion metal, and may further contain other additives. To form such a metal coating, an appropriate coating material is selected in each of the above methods.

After the intermediate layer having the diffusion layer is formed in this way, a glass layer is then applied. A usual method can be applied to the glass layer. A glass paste is prepared and applied to the surface of the intermediate layer by coating, dipping, spraying or the like. After applying, heat treatment under predetermined conditions,
Form a glass layer. In particular, when forming a glass layer containing the above-mentioned radiative particles dispersed therein, JP-A-10-2
It can be manufactured by the method disclosed in 87443. That is, particles containing high-purity silicon tetraboride or the like are added to an inorganic polymer liquid and mixed, and this dispersion liquid is sprayed with a spray dryer or the like and dried with hot air. As a result, the inorganic polymer liquid is dried and condensed to form an inorganic polymer film on the particle surface. Furthermore, when this particle group is heat-treated in the atmosphere, the inorganic polymer is combined with oxygen to produce silicon dioxide. As a result, emissive particles having a silicon dioxide glass film on the surface of the particles are obtained.
Further, the radiative particles, the reaction hardening glass raw material powder, the dispersant and the shape-retaining agent are mixed to form a glass paste. Fill the spray gun with this glass paste,
By spray coating on the surface of the intermediate layer and heat treatment,
A high-purity silica glass-coated radiative particle-containing glass layer can be obtained.

The coefficient of thermal expansion of the glass layer is preferably approximated to the coefficient of thermal expansion of the intermediate layer. This makes it possible to ensure good bondability between the intermediate layer and the glass layer interface. For example, when the intermediate layer includes an aluminum diffusion layer, it is preferable to adjust the thermal expansion coefficient of the glass layer to about 8 × 10 ⁻⁶ / ° C.

Before forming the glass layer,
It is preferable to degrease and wash the surface of the intermediate layer. On the other hand, it is preferable to avoid treatment such as acid cleaning or shot blasting for roughening or partially destroying the surface of the intermediate layer.

[0034]

EFFECTS OF THE INVENTION According to the present invention, the glass layer can be held on the surface of the metal base material with good adhesion, so that the effectiveness of applying the glass layer is stably exhibited.

[0035]

EXAMPLES Specific examples of the present invention will be described below. The present embodiment is an example in which the present invention is applied to an exhaust pipe of an internal combustion engine. The exhaust pipe 40 has a length of 100 mm as shown in FIG.
A cylindrical body of spheroidal graphite-containing cast iron (FCD500) having a thickness of 5 mm, an outer diameter of 70 mm, an inner diameter of 60 mm and a thickness of 5 mm is formed as the base material 42, and exhaust gas passes through the inside. After degreasing and acid cleaning the inner surface of the base material 42 in advance, and then drying, a molten aluminum bath at 670 ° C. to 700 ° C. (Al: 99 wt% or more, Si: 0.50 wt% or less, Fe: 0.80 wt % Or less) for several minutes to form an intermediate layer 44 having an aluminum diffusion layer of about 25 μm on the inner surface of the base material 42. Fe-A is used for the aluminum diffusion layer.
The formation of an alloy layer of 1 was confirmed. In addition, the intermediate layer 44
An aluminum oxide film was formed on the outermost surface of, and an aluminum layer was formed on the inside.

After the intermediate layer 44 is formed in this way,
As radiative particles, the surface of silicon tetraboride particles was coated with a radiant particle (2.5 wt%) coated with a silica glass layer having a purity of 98 wt% or more, and reactive cured glass (composition: S
A glass paste containing i-B-Al) (95 wt%) was sprayed and fired at about 900 ° C. to form a radiative glass layer. The glass paste has a coefficient of thermal expansion of 8 ×.
What was prepared so that it might become 10 ^<-6 > / ^degreeC was used. As a result, as shown enlarged in FIG. 3, the intermediate layer 44 of about 25 μm and the glass layer 46 of about 25 μm are formed on the inner surface of the substrate 42.
A coating 48 consisting of was formed.

By using the exhaust pipe 40 of this embodiment coated with the glass layer 46 as a turbo exhaust pipe, the engine exhaust gas is allowed to pass therethrough, and the exhaust temperature (° C.) and the exhaust pipe outer surface temperature (° C.) are set. It was measured. As a comparative example, the same test was performed on the exhaust pipe of this embodiment except that the surface was untreated. The result is shown in FIG.

According to the results shown in FIG. 4, the exhaust temperature 850
In the vicinity of ° C, the outer surface temperature of the exhaust pipe 40 of the example was about 700 ° C, whereas the outer surface temperature of the exhaust pipe of the comparative example was about 820 ° C. That is, the exhaust gas temperature 850
It was found that the exhaust pipe 40 of the present embodiment at 120 ° C. has a heat insulating effect of about 120 ° C. as compared with the exhaust pipe of the comparative example. In addition, the conventional ceramics heat insulation layer (about 1
000 μm thickness), in the same test, about 70 ° C
Only the heat insulating effect of (exhaust gas temperature of 850 ° C.) was obtained. It has been found that cast iron (transformation temperature of about 780 ° C.) can be sufficiently used as an exhaust pipe base material if the glass layer 46 of the present embodiment has a heat insulating effect. Further, the glass layer 46 having a layer thickness of about 25 μm provided a sufficient heat insulating effect.

Next, regarding the exhaust pipe 40 of this embodiment, the transformation temperature of spheroidal graphite cast iron (FCD500) is 700 ° C., which is lower than 730 ° C., and 850 ° C., which is higher than that temperature, respectively.
After standing for 0 hour and 50 hours, the presence or absence of peeling of the glass layer before and after standing, the weight increase rate (oxide weight), and the adhesion strength were measured. The results are shown in Table 1.

[0040]

[Table 1]

As shown in Table 1, the exhaust pipe 40 of this embodiment
Regarding, the glass layer 46 was not peeled off at any temperature. Further, no increase in weight was observed, confirming that there was no high temperature oxidation. Further, the adhesion strength was also maintained stably. In particular, the temperature above the transformation point (850
Even at (° C.), sufficient adhesion strength was maintained. From this, it was found that the exhaust pipe 40 of this example had sufficient heat-resistant adhesion.

Further, with respect to the exhaust pipe 40 of this embodiment, condition 1 (normal temperature (blasting, 2 minutes) to 700 ° C. (in a high temperature furnace, 4
Min)) and condition 2 (normal temperature (blast, 2 minutes) to 850 ° C)
(In a high-temperature furnace, 4 minutes)), two types of cooling / heating cycles were performed 130 times, and in any case, peeling of the glass layer 46 was not observed. Moreover, when the above-mentioned two types of cooling / heating cycle conditions were each performed 1000 times to evaluate cooling / heating durability, no peeling of the glass layer 46 was observed in any case. From this, it was found that the exhaust pipe 40 of the present example has sufficient adhesiveness against cold shock.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an embodiment of the present invention.

FIG. 2 is a diagram showing an embodiment applied to an exhaust pipe of the present invention.

FIG. 3 is a diagram showing a laminated structure of an intermediate layer and a glass layer in an example.

FIG. 4 is a graph showing the heat insulation effect when the exhaust pipe of the example is exposed to engine exhaust gas.

[Explanation of symbols] 2 Glass cover 4 base material 6 glass layers 20 Middle class 22 Diffusion layer

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Yano 3-36 Noritake Shinmachi, Nishi-ku, Nagoya, Aichi Prefecture Noritake Co., Ltd. Limited (72) Inventor Takamitsu Fukui 3-chome, Noritake Shincho, Nishi-ku, Nagoya, Aichi Prefecture No. 1-36 Noritake Company Limited (56) Reference JP-A-56-47565 (JP, A) JP-A-4-209588 (JP, A) JP-A-10-287443 (JP, A) Kaihei 2-92531 (JP, A) JP 4-135846 (JP, A) JP 2-125735 (JP, A) JP 4-363221 (JP, A) JP 61-8349 ( (58) Fields surveyed (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 F01N ^7/ 00-7/20

Claims (7)

(57) [Claims] 1. A glass-coated body, a spheroidal graphite cast iron base material, and an intermediate layer provided on the surface of the base material.
And a glass layer through which the glass layer is made of aluminum oxide in addition to silicon dioxide.
Having a glass structure and radiative particles, the intermediate layer containing Al provided on the surface of the base material.
In the metal layer of
Are diffused into each other to form a diffusion layer on the glass layer side.
Is a coating having a structure in which an Al oxide layer is formed . 2. The thickness of the diffusion layer is 25 μm or more and 100 μm
The glass cover according to claim 1, which is: 3. The glass cover according to claim 1 , wherein the intermediate layer contains iron or silicon . 4. The glass layer comprises SiO ₂ —B ₂ O ₃ —Al ₂
The glass coated body according to claim 1, which is an O ₃ system. 5. The radiative particle is formed of one or more selected from the group consisting of a silicon compound, molybdenum disilicide, silicon carbide, iron oxide, silicon nitride, and chromium oxide. Item 5. The glass cover according to any one of items 1 to 4. 6. The intermediate layer is formed by a hot dip plating method.
That, glass-coated body according to any one of claims 1 to 5. 7. The glass cover according to any one of claims 1 to 6, which is an exhaust system member that comes into contact with exhaust gas of an internal combustion engine for a vehicle.