JPH0362798B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an infrared blackbody coating composition that uses various metals as a base material and that has an infrared emitter and a low melting point high expansion glass as main components on the surface of the base material. In particular, the present invention relates to an infrared radiator on which a coating of an object is formed and a method for manufacturing the same, and particularly the present invention has excellent adhesion between a metal base material and a black body coating, which is a surface coating, and improves the thermal shock resistance and mechanical strength of the base material. The present invention relates to an infrared radiator having an excellent metal base material and a method for manufacturing the same.

In general, infrared radiators have a low surface temperature, a large radiation area, and a good infrared absorption rate of the irradiated object, so they are widely used for home heating, cooking, drying food and various paints, and infrared processing. In particular, due to the recent energy conservation issues, this heater is attracting attention as a heater that efficiently emits infrared rays.

[Conventional technology]

Conventionally, infrared radiators have been made of sintered oxide ceramics such as cordierite, alumina, and zirconia, or coated with transition element oxide compositions such as manganese dioxide, iron oxide, and cobalt oxide. What has been done is known.

However, the conventional oxide-based ceramic sintered bodies generally have low thermal conductivity; for example, cordierite has a relatively low coefficient of thermal expansion of 2 to 3 x 10 ^-6 /°C, but a thermal conductivity of 0.003 cal/cm. sec/°C, and when heated and used, there is an imbalance in temperature distribution, which has poor thermal shock resistance and is prone to cracking.

[Problem that the invention seeks to solve]

The present invention aims to eliminate and improve the drawbacks of the infrared radiators in the prior art, and uses various metals as base materials that have particularly excellent thermal shock resistance and malleability and good workability, and has a metal surface on the surface. The object of the present invention is to provide an inexpensive infrared radiator with excellent thermal shock resistance, mechanical strength, etc. by interposing a low melting point glass material or the like which has good adhesion to the infrared ray radiator and is easy to form a coating of the infrared ray radiator at a relatively low temperature.

That is, the present invention focuses on the fact that conventional infrared radiators are made of ceramic alone or as a ceramic base material, which has poor thermal shock resistance and is expensive. The base material is a metal with excellent workability, and a glassy substance with a relatively low melting point and high expansion coefficient is mixed into the infrared black body coating formed on the metal surface to lower the melting point of the black body paint as a whole. To provide an infrared radiator made of a metal base and capable of emitting all infrared wavelengths and having excellent thermal shock resistance and mechanical strength, by forming a black body film by firing an infrared radiator forming composition at a low temperature. It is something.

[Means for solving problems and their effects]

According to the present invention, it is necessary that an infrared blackbody coating composition film consisting of an infrared emitter mainly composed of an oxide of a transition element and an inorganic compound with a low melting point is formed on the surface of a metal substrate.

As the metal, various metals such as stainless steel, steel, iron, and aluminum can be used. The reason why various metals are used as the base material in the present invention is that metals are generally cheaper than ceramic base materials, have excellent thermal shock resistance, and have excellent workability. This is because it has properties suitable as a base material for black body paint. The above-mentioned metals are relatively inexpensive and widely used, and can be used for various purposes, such as high temperature (heat resistance temperature of about 1000℃) and medium temperature (heat resistance temperature of about 800℃) at the temperature to be heated by an infrared radiator. ℃), low-temperature (heat-resistant temperature 550℃), and metal base materials suitable for each temperature can be selected. For example, if the operating temperature is 600℃ or higher, it is advantageous to choose a material with a heat resistance of around 800℃, such as steel or iron, or a material with a heat resistance of approximately 1000℃ or higher, such as stainless steel. When the temperature is below 600°C, it is advantageous to use an aluminum base material. Also, metals other than those exemplified above can be used, but it is advantageous to choose a metal with a coefficient of thermal expansion as small as possible. Since the thermal expansion coefficient of the black body paint film formed on the surface is generally smaller than that of metal, this is to prevent mismatch between the two.

As the oxide of the transition element, one or more selected from manganese dioxide, oxidizing material, cobalt oxide, copper oxide, and chromium oxide can be used. In this way, in the present invention, the infrared radiator mainly composed of an oxide of a transition element can be used as the infrared radiator of conventional product 1 (cordierite porcelain alone) or the metal base of conventional product 2, as shown in the graph of FIG. The spectral emissivity is extremely low in the wavelength range of 2 μm to 4 μm, as is the case with single materials (stainless steel), and near-infrared radiation (2 μm to 3 μm)
It also has the characteristic of being able to uniformly radiate infrared rays in the entire far-infrared wavelength range (5 μm to 15 μm) with high efficiency (spectral emissivity of 90% or more).

Further, it is necessary that the oxide of the transition element be contained in the total composition of the black body paint in an amount of 10 to 90% by weight. If the content ratio is less than 10% by weight, the infrared radiation characteristics emitted from the infrared black body paint coating formed on the surface of the metal substrate will be significantly reduced, making it unsuitable for the purpose of use; If the infrared black body paint film formed on the surface of the metal base material is baked at a relatively high temperature, strong adhesion to the metal base material cannot be obtained, and the heat resistance temperature of the metal base material is 1000 °C. This is because sintering at a relatively high temperature of .degree. C. or higher causes deterioration of the metal base material.

Note that the oxide of the transition element has a thermal expansion coefficient α
is approximately 8 to 9×10 ^-6 /°C, whereas in the case of metal substrates such as stainless steel, α is approximately 9 to 6×10 ^-6 /℃.
℃, and the α of the transition element oxide is slightly smaller than that of the metal, so select a glass with a low melting point and high expansion, for example, with α in the range of 8 to 25 × 10 ^-6 /℃, and mix it in an appropriate amount. It is necessary to bring the entire blackbody paint close to the α of the metal. Further, since the transition element oxide is not toxic to the human body, the infrared radiator of the present invention can be used in a fish grill or a grilled meat cooker. In addition, the infrared ray emitter of the present invention can emit infrared rays of a wavelength that is uniformly absorbed into the interior and deep parts of grilled fish and grilled meat, and furthermore, it is possible to cook grilled fish and grilled meat while retaining moisture in its structure. Because of this, it has the advantage of being able to cook fish and meat much more deliciously than conventional cookers of the same type.

Examples of the low melting point inorganic compound include glass having a low melting point and a high coefficient of expansion, such as alumina silicate glass, soda zinc glass, soda barium glass,
barium glass, soda lead glass, high lead glass,
Potash soda lead glass, potash lead glass can be used advantageously. These low melting point glasses have a softening temperature in the range of 400-1000℃,
By varying the composition ratio of this to the infrared radiator, the melting point and baking temperature of the entire infrared blackbody paint can be varied. Therefore, the heat resistance temperature of various metal base materials is approximately 1200℃.
It is important to appropriately select and use the type and amount of the glass in consideration of the following. In other words, according to the present invention, by mixing an appropriate amount of various types of glass having a low melting point and a relatively high coefficient of expansion into the black body paint, heating and baking at a relatively low temperature, that is, 500 to 1100°C, is possible. An infrared blackbody film can be easily and firmly formed on a metal surface by changing the temperature.

Furthermore, the coefficient of thermal expansion α of the low-melting point glass varies depending on the type, but it has a relatively high coefficient of expansion of about 8 to 25×10 ^-6 , so as explained earlier, it is higher than that of metal. By mixing the black body paint with small transition element oxides and bringing the α of the entire black body paint close to the α of the metal, it is possible to prevent mismatch between the two, thereby achieving strong adhesion to the metal surface. An infrared blackbody coating can be formed.

As described above, according to the present invention, various metals with excellent thermal shock resistance and workability are used as the base material depending on the purpose of use, and furthermore, an oxide of a transition element with high radiation efficiency in the entire infrared wavelength region, By forming a film of an infrared black body paint on the surface of the metal base material at a relatively low firing temperature, the coating is made of various types of glass having a low melting point and a thermal expansion coefficient α close to that of metals. Defects of infrared radiators can be removed and improved.

Next, a method for manufacturing an infrared radiator according to the present invention will be explained.

According to the present invention, a manufacturing process consisting of the following sequences (a) to (c) is required. That is, (a) a step of treating the surface of a metal substrate; and (b) adding a viscous substance such as a vehicle to a composition of 10 to 90 parts by weight of an oxide of a transition element and 90 to 10 parts by weight of an inorganic compound with a low melting point. (c) baking at a heating temperature of 500 to 1100°C to form a composition film of an infrared emitter and a low melting point inorganic compound on the surface of the metal base; It consists of a process.

The step (a) above is necessary for removing dirt or degreasing the surface of the metal base material, and it also chemically coats the metal surface in order to form an infrared black body film with good adhesion on the surface of the metal base material. This is necessary to activate the metal oxide to form a metal oxide film and improve the affinity with the oxide of the transition element.

In the step (b) above, Fe ₂ O ₃ and MnO ₂ are used as described above.
Oxides of transition elements such as Relatively low temperature, e.g. 500~1100℃ by mixing with body paint
It is possible to form an infrared blackbody coating with strong adhesion at a firing temperature of . The reason for this is that a conventional infrared radiator made of alumina or cordierite porcelain alone cannot form a black body coating on the surface of a metal substrate. That is, the present invention applies an infrared black body paint film having a coefficient of thermal expansion comparable to that of the metal onto the surface of a base material that has been chemically activated by surface treatment of the metal, at a temperature of 500 to 1100 degrees Celsius, which is lower than the heat resistance temperature of the metal. This is because by heating and firing at a relatively low temperature, an infrared ray emitter of a metal base material with excellent thermal shock resistance and adhesion can be manufactured.

As mentioned above, the step (c) is a necessary step to form a strong infrared black body paint film at a firing temperature lower than the heat-resistant temperature of the metal base material,
This is the reason for using a low melting point, high expansion glass composition. In other words, the above-mentioned glass having a low melting point serves to lower the melting point of the entire infrared blackbody paint.

In the step (b) above, the method for forming a film of infrared emitting blackbody paint on the surface of a metal substrate is to add various solvents and A method of forming a uniform coating by applying a viscous substance mixed with a vehicle, etc., which is a mixture of binders, etc. to a uniform and appropriate viscosity, such as spraying, brush printing, screen printing, and drip-dipping impregnation. can be adopted.

Next, the most typical embodiment of the infrared radiator of the present invention will be described.

〔Example〕

Example 1 A stainless steel corrugated plate (300 mm x 50 mm x thickness 1.5 mm) with a thermal expansion coefficient (hereinafter abbreviated as α, TR→300°C and below) of 9×10 ^-6 /°C was first polished with a sandblaster. After polishing, ultrasonic degreasing with trichlene, drying, and heating in air at 850°C for 1 hour, a thin oxide film was formed. Then, 60 parts by weight of MnO ₂ , 20 parts by weight of Fe ₂ O ₃ , 10 parts by weight of CuO, and 10 parts by weight of CoO
The mixture with parts by weight is once calcined in air at 1100°C to 1200°C for 1 hour and has an α of 8×10 ^-6 /°C40
In the weight part, α is 10× as a low melting point high expansion coefficient glass.
Add 60 parts by weight of a mixture of barium glass with a temperature of 10 ^-6 /°C and alumina silicate glass with an α of 5 x 10 ^-6 /°C, grind it in a ball mill, and add a solvent consisting of ethyl cellulose and butyl carbitol acetate to the resulting fine powder. was added and the paste was brushed to form a uniform infrared black body paint film, and baked in the air at 900℃ for 1 hour in a box furnace until α was 8.8×10 ^-6 /℃.
A metal-based red wire radiator with a strong infrared blackbody coating was created.

When this radiator was used as a gas stove cooker for grilling fish and beef, the surface of the fish and beef turned slightly brown and the inside was different from the surface and inside, as shown in Figure 2. It was confirmed that the temperature difference was small and that the deep part was heated evenly.

Example 2 A ^stainless steel plate (300 mm
x 400mm x thickness 1mm) with 5% sodium orthosilicate,
After degreasing with a hot aqueous solution of 0.5% surfactant for 20 minutes, it was washed with water. Next, acid treatment with 7% H ₂ SO ₄ at 60-70°C for 5 minutes, neutralization with an alkaline solution of 3.6 g of soda ash and 1.2 g of hydrated borax per 1 part of water, followed by washing with water.
It was dried at 110°C for 1 hour to form a thin oxide film.
and 60 parts by weight of MnO ₂ and 25 parts by weight of Fe ₂ O ₃ ,
Once a mixture of 10 parts by weight of CuO and 5 parts by weight of CoO is
After calcining in air at 1100°C to 1200°C for 1 hour, α was 8.5×10 ^-6 /°C, and 30 parts by weight of this was added to a low melting point high expansion glass with α of 10×10 ^-6 /°C. 70 parts by weight of barium glass was made into a slurry in the same manner as in Example 1, and a uniform infrared black body paint film was formed on the stainless steel flat plate by spray coating, and baked at 850°C in the air in a box furnace for 30 minutes. Then α is
A metal-based external radiation emitter with a strong infrared blackbody coating of 9.5×10 ^-6 /°C was fabricated.

When this radiator was used as a reflector for a gas stove, compared to conventional metal reflectors, the hands, feet, and face closest to the stove did not feel hot due to strong secondary radiation, but the center of the body It felt warm enough, and the heating effect was excellent.

Example 3 A steel plate (500 mm x 500 mm x 2 mm thickness) with α of 12 x 10 ^-6 /°C was first roughened by sandblasting to roughen the metal surface.
Next, the material was ultrasonically degreased with trichloride, dried, and then heated in air at 400° C. for 1 hour to form a thin oxide film.
and 60 parts by weight of MnO ₂ and 20 parts by weight of Fe ₂ O ₃ and CuO10.
A mixture of parts by weight and 10 parts by weight of CoO was heated to 1100℃~1200℃.
When calcined in air at ℃ for 1 hour, α is 8×
10 ^-6 /℃, and this is added to 10 parts by weight of soda lead glass with α of 12×10 ^-6 /℃ as a low melting point high expansion glass.
90 parts by weight were mixed, made into a slurry in the same manner as in Example 1, sprayed to form a uniform infrared black body paint film, and heated at 600°C in the air in a box furnace.
After firing for 30 minutes, a metal-based infrared radiator having a strong infrared blackbody coating with an α of 11.6×10 ^-6 /°C was produced.

When this radiator was used as a reflector in a food oven, the internal temperature distribution became smaller as in Example 1 compared to the conventional reflector, and food could be heated more uniformly.

〔Effect of the invention〕

As described above, according to the present invention, the metal-based infrared radiator has extremely high spectral emissivity of 90% or more in the entire infrared region as shown in Figure 1, and has excellent thermal shock resistance and processability. It is used in relatively inexpensive cooking appliances, dryers, heaters, etc. that have excellent complex shapes for various purposes, and as shown in Figure 2, it is a highly efficient infrared ray that can uniformly heat foods, especially protein foods. You can donate your body.

[Brief explanation of drawings]

FIG. 1 shows a metal-based infrared radiator of the present invention,
A graph showing the relationship between infrared wavelength and spectral emissivity for conventional products 1 to 3, and FIG.
This figure shows the temperature difference between the bottom surface and the center over a certain period of time when grilling mm of beef.

Claims (1)

[Claims] 1 Manganese dioxide, iron oxide,
Any one of cobalt oxide, copper oxide, and chromium oxide
10 to 90 parts by weight of an infrared radiator made of a species or oxide selected from two or more species, and 90 to 90 parts by weight of an inorganic compound with a low melting point.
1. An infrared radiator having a metal base and having an infrared black body coating composition film formed thereon. 2. The inorganic compound is a low melting point high expansion glass, such as alumina silicate glass, potash lead glass, soda lead glass, soda zinc glass, soda barium glass, barium glass, high lead glass,
Any one or two types of potash soda lead glass
The infrared radiator according to claim 1, which is selected from at least one species. 3 (a) A step of treating the surface of the metal base material; (b) 10 to 90% by weight of an oxide selected from one or more of manganese dioxide, iron oxide, cobalt oxide, copper oxide, and chromium oxide. (c) heating at 500 to 1100°C A method for manufacturing an infrared radiator of a metal base material, comprising: firing at a high temperature to form a composition film of an infrared radiator and a low melting point inorganic compound on the surface of the metal base material.