JPS621817B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat insulating laminate component having a mechanically and thermally strong ceramic coating and having a heat insulating interface layer interposed therebetween.

Conventionally, gasoline engines, diesel engines, and the like have been constructed of metal members such as cast iron and aluminum alloy. However, recently, from the perspective of energy conservation, research has been actively conducted to reduce the large heat loss caused by engine exhaust and cooling, and to increase the thermal efficiency of engines. Many methods have been proposed that use ceramics alone or composite structures made of ceramics and metals laminated.

However, in either case, the use of ceramics alone or the use of ceramics for shrink-fitting, bolting, caulking, etc. of ceramics and metals requires high-strength components, so the preparation of the starting raw materials, molding and sintering conditions, and sintering Extremely advanced and precise manufacturing techniques are required, including finishing the body. This results in a significant increase in cost, and it is necessary to increase the thickness of the ceramic layer in order to further improve the heat insulation effect. Generally speaking, due to the large difference in coefficient of thermal expansion between ceramics and metal components, cracks and peeling are likely to occur due to the formation of gaps between the combined metal components, "backlash" and thermal strain under high-temperature conditions. Therefore, the reliability is poor, and there are still many problems in practical application.

The present invention solves these conventional problems and does not require advanced manufacturing technology.
Furthermore, the relatively simple method aims to provide a heat-insulating laminate component with high reliability in the manufacturing process. The present invention will be explained in detail below with reference to the drawings.

As shown in the figure, the present invention provides a heat insulating material made of a metal porous body and/or ceramics between the overlapping surfaces of a metal base 1 made of an iron-based alloy or an aluminum alloy and a metal member 2 made of iron or an iron-based alloy. The metallic interface layer 3 is interposed, and these mutually overlapping surfaces are fixed with a bonding layer by metal soldering or a chemical bonding layer 4 of chromium oxide produced by firing chromic acid, and the metal member 2
A ceramic coating 5 chemically bonded with thermally sprayed ceramics and/or chromium oxide is applied to the outer surface of the housing. In this way, an effective heat insulating effect can be obtained by the relatively porous heat insulating interface layer 3 and the ceramic coating layer 5, and in addition, the heat resistant and abrasion resistant ceramic coating layer 5 on the surface of the metal member 2 can be It is a relatively thin coating, and the two-stage structure with the interface layer 3 can greatly alleviate thermal shock and temperature gradient.

Note that the metal used for the metal substrate 1 of the present invention is an iron-based alloy and an aluminum-based alloy, and examples thereof include cast iron, carbon steel, aluminum alloy casting, and the like.

Further, the metal member 2 coated with the ceramic 5 is made of iron or an iron-based alloy, such as cast iron, carbon steel, stainless steel, heat-resistant steel, etc.

Next, the ceramics 5 coated on the outer surface of the metal member 2 made of the iron-based alloy are thermally sprayed ceramics and/or ceramics chemically bonded with chromium oxide, such as stabilized and partially stabilized ZrO ₂ , CaZrO ₃ , _{SrZrO3 , MgZrO3 , Y2Zr2O7}
This is a coating formed by plasma spraying one or more oxides selected from the following oxides. Ceramic coatings chemically bonded with chromium oxide can also be made of various heat-resistant oxides, such as ZrO ₂ , SiO ₂ , Al ₂ O ₃ , TiO ₂ ,
5 to 20 parts by weight of fine powder of one or more oxides selected from oxides such as CaZrO ₃ and MgZrO ₃
A slurry made by adding 100 parts by weight of an aqueous solution of H ₂ CrO ₄ of 1.5 to 1.7 and mixing well using a ball mill is applied to one side of the metal member 2, and heated at 450 to 650°C.
It is a ceramic coating chemically bonded by heat-treated chromium oxide, and the thickness of the coating is adjusted appropriately by repeating this coating and heat treatment. Furthermore, since the plasma sprayed layer is essentially porous, it is even more preferable to reduce the porosity and strengthen the coating by coating and heat-treating the sprayed coating with the slurry containing H ₂ CrO ₄ . A coating is obtained.

That is, MgO or CaO is added to an aqueous solution of H ₂ CrO ₄ with a specific gravity of 1.6 to 1.7 or 1 mol of H ₂ CrO ₄ in this solution.
0.1-0.4 mol added and dissolved solution or specific gravity 1.6-
A small amount of refractory oxides such as stabilized ZrO ₂ , TiO _{2 ,} SiO ₂ , Al ₂ O _{3 and}
Add a small amount, preferably 5 to 12% by weight, of fine powder of one or more oxides selected from CaZrO ₃ etc., mix well to prepare a slurry, and fill the pores of the sprayed ceramic with this slurry. Soak,
By performing a heat treatment at 450 to 650°C and repeating this treatment several times, open pores in the coating layer are eliminated and the coating is strengthened. The thickness of the ceramic 5 coated on the metal member 2 is determined to be 50 to 250 μm, preferably 130 μm, based on experimental results, taking into account the thermal shock caused by the thermal energy of combustion gas, the thermal conductivity and thermal expansion characteristics of ceramics, etc.
It is about m.

Next, one of the members used for the heat insulating interface layer 3 is a metal porous body, such as a metal fiber sintered body, a metal mesh laminated sintered body, a metal powder sintered body, etc. These metal porous bodies are stainless steel fiber sintered bodies having an average pore diameter of 10 to 100 μm and a porosity of 40 to 75%, preferably a maximum pore diameter of 50 to 60 μm and a porosity of about 50%. In terms of increasing the strength and the bonding strength between the interface layer 3 and the metal surfaces 1 and 3 on both sides, a material in which reinforcing wire mesh is sintered and integrated on both sides of stainless steel fibers is most suitable as a member.

In addition, when the member used for the interface layer 3 is ceramic, for example, it may be stabilized or partially stabilized.
For 100 parts by weight of fine powder of one or more oxides selected from ZrO ₂ , Ca (Sr, Mg) ZrO ₃ , Y ₂ Zr ₂ O ₇ etc., 10 parts by weight of ZrC fine powder and 4 parts by weight of CaCO ₃ fine powder Ceramics is made by molding a well-mixed powder by adding weight, sintering it well at 1500°C or higher, and adjusting the apparent porosity to 10 to 20%. Preferably, this sintered body is made of an oxide as described above. Fine powder of H ₂ CrO ₄ is added to a concentrated aqueous solution of H 2 CrO 4 and the prepared slurry is used to impregnate the pores of the ceramic and heat-treat it. By repeating this treatment 4 to 5 times, high strength can be achieved without reducing the insulation properties. A ceramic interfacial layer is formed.

Furthermore, the metal used for the interface layer consisting of a metal-ceramic composite structure is a metal porous body, such as a stainless steel mesh stack, a fiber sintered body,
Examples include stainless steel fiber felt. Use a material with a relatively large pore diameter and a bulk density of 40 to 70%. Ceramic raw materials are also heat-resistant oxides, such as stabilized or partially stabilized ZrO ₂ , Ca
(Sr, Mg) 20 to 50 parts by weight of one or more powders of 44 μm or less selected from ZrO ₃ , etc. with a specific gravity of 1.45 to
In addition to 100 parts by weight of an aqueous solution of 1.6 H ₂ CrO ₄ and thoroughly mixed using a ball mill, a slurry is prepared, and this slurry is impregnated into the pores of the metal porous body.
After filling and drying, heat treatment is performed at 450-650℃. By repeating this impregnation and heat treatment 6 to 8 times, an interface layer consisting of a strong heat-insulating composite structure is formed.

Next, the combination of each layer of the laminated structure component of the present invention,
The bonding will be explained in more detail with reference to Examples.

Example 1 The constituent material is a metal member made of carbon steel coated with ceramic spray, the interface layer is a stainless steel fiber sintered body,
When the metal base is made of aluminum alloy casting, first prepare a 50 x 50 x 2.5 mm specimen of carbon steel S45C (JIS), roughen both sides with 250 μm sandblasting, and coat one side with CaO6 weight. %and
Ceramic coatings were formed by plasma spraying ZrO ₂ stabilized with 10% MgO to a thickness of 0.2 mm.

Separately, 3 parts by weight of ZrO ₂ powder of 10 μm or less and 5 μm of ZrO 2 powder stabilized with CaO + MgO as above
Add 3 parts by weight of the following SiO ₂ powder to 100 parts by weight of an aqueous solution of H ₂ CrO ₄ with a specific gravity of 1.5, and grind and mix for 24 hours using a ball mill to prepare a slurry. Soak for about 15 minutes to impregnate the pores of the coating with the slurry.
Wipe off the excess slurry that has adhered to the coating surface.
Raise the temperature at 4℃/min in an electric furnace to 550℃
Heat treatment was performed for about 20 minutes. By repeating this impregnation and heat treatment four times, the apparent porosity of the sprayed ceramic coating is reduced to 1% or less, and along with this low porosity, the bonding strength with metal components is 390 kg/cm ² or more (using an epoxy resin adhesive). The tensile strength test was carried out using the adhesive, and the value was determined by peeling off the adhesive surface of the resin. The surface of the steel plate opposite to the ceramic coating needs to be bonded to the metallic interface layer as described below, so masking tape is pasted on that surface before the slurry treatment is performed, and the slurry treated material is After drying, the tape can be peeled off and bonded in the next step. Note that masking may be performed with a polystyrene resin paint instead of the tape. This decomposes and disappears during heat treatment.

The heat insulating interface layer is 50 x 50 x 4 mm, porosity is approx.
A commercially available stainless steel fiber sintered body having a carbon fiber content of 50% was used. This type of sintered body may also have reinforcing wire mesh sintered on both sides at the same time. The thermal conductivity of the interface layer used was approximately 0.008 Cal/cm·sec·°C (value measured by hot wire method).

Then, the bare surface of the carbon steel plate is coated with a waxing agent made of fine powder of pure copper in the form of a paste with a 20% nitrocellulose solution to a thickness of about 0.2 mm, and the stainless steel fiber sintered body is superimposed on this, approx. from above
A 500 g weight was placed on the joint, and brazing was performed at about 1125° C. in a reducing atmosphere of butane conversion gas (8 to 10% Co).

Next, the bonded body and the metal base are bonded.
The metal base is made of aluminum alloy casting.
JISAC5A (commercially available Y alloy), 50 x 50 x 10 mm, was used. A thin plate of Al-Si aluminum solder (equivalent to JISBAlO) is laid on the base surface, then flux is applied, the interface layer of the bonded body is superimposed on it, and a weight of about 500 g is placed on top. The material was heated to 560°C in a reducing atmosphere in an electric furnace and soldered to create a prototype heat-insulating laminate. For such a combination of laminated products, it is also possible to first bond each metal material using a metal brazing filler metal, and then in the subsequent process strengthen the coating by applying ceramic spray coating and chemical bonding with chromium oxide. can get. Furthermore, when an iron-based alloy is used instead of the aluminum alloy substrate, the interface layers can be simultaneously bonded using pure copper solder. The thermal conductivity of the laminated parts in this case is 0.007 to 0.006 Cal/cm・
The performance was sufficiently satisfactory at sec・℃.

Example 2 In the case of a heat-insulating laminate component consisting of a metal member having a ceramic coating chemically bonded with chromium oxide, a ceramic heat-insulating interface layer, and a metal base, spheroidal graphite cast iron (JIS,
FCD40), a plate of 50 x 50 x 2.3 mm was used, both sides of which were roughened by sandblasting in the same manner as in Example 1, and one side was coated with a surface of 5 μm or less per 100 parts by weight of a concentrated aqueous solution of H ₂ CrO ₄ with a specific gravity of 1.56. 9 parts by weight of SiO ₂ powder, 5μ
Add 3 parts by weight of Al ₂ O ₃ powder with a diameter of less than 10 μm and 9 parts by weight of ZrO ₂ powder with a diameter of less than 10 μm melt-stabilized with 8% by weight of CaO, and apply a slurry prepared by pulverizing and mixing using a ball mill for 24 hours, and dry. After that, heat treatment was performed at 550° C. for about 20 minutes, and the coating and heat treatment were repeated five times. Through this treatment, H ₂ CrO ₄ in the slurry is decomposed and converted to CrO ₃ → Cr ₂ O ₃ , which forms a strong chemical bond with the coexisting SiO ₂ , Al ₂ O ₃ , ZrO ₂ particles and cast iron, resulting in a slurry with a thickness of approximately 120 μm. A ceramic coating was formed. Next, to further increase the bonding strength of this film, it was immersed for 10 minutes in a concentrated aqueous solution of H ₂ CrO ₄ with a specific gravity of 1.65, and after drying, it was heat-treated at 550°C, and then immersed in this solution and heat-treated twice. I went there repeatedly. The thermal conductivity of the ceramic coating thus obtained was found to be approximately 0.006 to 0.007 by the laser pulse method.

CaO, 5% by weight + in the insulating ceramic interface layer
Below 44μm stabilized with 10% MgO by weight
1500 parts of mixed powder consisting of 100 parts by weight of ZrO ₂ powder, 12 parts by weight of ZrC of 10 μm or less, 5 parts of CaCO ₃ of 5 μm or less, and 50 parts of MgZrO ₃ powder of 20 μm or less
It was pressure molded at Kg/cm ² and sintered at 1500°C.
Its apparent porosity was 15.6%, and the following treatment was performed to strengthen this sintered body. That is, for 100 parts by weight of an aqueous solution of H ₂ CrO ₄ with a specific gravity of 1.55 as a reinforcing agent,
<10μm stabilized with CaO, 8% by weight
8 parts by weight of ZrO ₂ powder and 12 parts of SiO ₂ powder of 5 μm or less
A slurry prepared by adding parts by weight and grinding and mixing for 24 hours using a ball mill was used. The ceramic sintered body was immersed in this slurry, the slurry was impregnated into the pores of the ceramic under a reduced pressure of 1 mmHg, and the temperature was raised at 4°C/min in an electric furnace to 650°C.
Heat treatment was performed at ℃ for about 30 minutes, and this impregnation and heat treatment was further repeated 6 times. The resulting ceramic interface layer has an apparent porosity of 2.3% and a thermal conductivity of
It was 0.005 Cal/cm·sec·°C, and had satisfactory performance as a heat insulating interface layer.

Next, gray cast iron (JIS
FC35) was used, and a method using chemical bonding of chromium oxide was used to bond this to the ceramic-coated spheroidal graphite cast iron member and the ceramic interface layer in a laminated manner. This method is described in detail in Japanese Patent Application No. 58-61660 and Japanese Patent Application No. 58-61661.
That is, for the bonding agent, 500g of CrO ₃ is dissolved in water, and the specific gravity is
Make a solution of H ₂ CrO ₄ of 1.65-1.7 and add
Dissolve 25g of ZnO and 50g of MgO powder, add water to make a solution with a specific gravity of 1.85, and then add 500g of this solution.
Stabilized ZrO ₂ powder 15g, 10μm or less
15g of TiO powder with a diameter of less than 5μm and SiO ₂ powder with a diameter of less than 5μm
30 g was added and ground and mixed for 24 hours using a ball mill to prepare a bonding agent.

As a pretreatment for joining, the ceramic-coated cast iron member and the gray cast iron (FC35, 50 x 50 x 5 mm size) as a base were placed in an aqueous solution of H ₂ CrO ₄ with a specific gravity of 1.45 heated to 85°C. Soaked, approx.
The graphite exposed on both cast iron surfaces was removed by heating and holding at 85°C for 15 minutes.

The slurry of the bonding agent was thoroughly applied using a brush to the joint surfaces of the degraphitized gray cast iron base, the ceramic interface layer, and the ceramic-coated spheroidal graphite cast iron member, and after about 5 minutes, the joint surfaces were each bonded. They were stacked together, the laminates were fixed with thin wires, the temperature was raised at 4°C/min using an electric furnace, and the heat was maintained at 550°C for about 30 minutes to fabricate a prototype heat-insulating laminate part.

This prototype was cut to a size of 15 x 15 mm on the bonded surface, and a tensile test piece was made using epoxy adhesive to measure the bond strength. As a result, it peeled off at the resin bonded part, and the strength was 385 kg/ cm ² or more. Furthermore, the thermal conductivity of the laminated component was 0.004 Cal/cm·sec·°C.

[Brief explanation of the drawing]

The figure is a sectional view showing the structure of the heat insulating laminate component of the present invention. DESCRIPTION OF SYMBOLS 1... Metal base, 2... Metal member, 3... Interface layer, 4... Bonding layer, 5... Ceramic coating.

Claims (1)

[Claims] 1. A heat insulating interface layer is interposed between the overlapping surfaces of a metal base made of an iron-based alloy or an aluminum alloy and a metal member made of iron or an iron-based alloy, so that these mutual overlapping surfaces are It is fixed with a solder bonding layer by metal soldering or a chemical bonding layer of chromium oxide caused by firing chromic acid, and the outer surface of the metal member is coated with a ceramic coating chemically bonded by thermal spraying or chromium oxide. A heat-insulating laminate component characterized by: 2. The heat-insulating laminate component according to claim 1, wherein the heat-insulating interface layer is a porous metal body, a ceramic, or a composite of metal and ceramics.