JP3200158B2 - Infrared radiator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared radiator that emits infrared rays for heating, cooking, heating and drying, heat treatment of materials, and various other types of radiant heating. The present invention relates to an infrared radiator having excellent infrared (far infrared) radiation characteristics.

[0002]

2. Description of the Related Art Generally, in heaters utilizing infrared rays, the radiator has a high infrared emissivity,
At the relatively low surface temperature described above, radiation in the visible region is small, but radiation in the far infrared region is large. As a radiator satisfying such requirements, conventionally, alumina,
Those made of various ceramic materials such as graphite and zirconia have been put to practical use. Among these materials, it is known that alumina has excellent performance as compared with other ceramic materials in terms of far-infrared radiation characteristics and heat resistance.

However, the conventional infrared radiator made of a ceramic material has a large weight and is easily broken.
Furthermore, there are problems that it is difficult to produce a thin material, and the heat conductivity of the radiator is poor due to poor thermal conductivity.

Therefore, a radiator in which ceramic is sprayed on the surface of a metal substrate has been put to practical use. However, in this case, a high cost is required for production, and it is difficult to obtain a thin plate or a radiator having a complicated shape. There are problems such as.

On the other hand, recently, an infrared radiator in which an anodized film (alumite film) having a thickness of about 20 μm or more is formed by applying an anodized film to the surface of a wrought aluminum alloy is also known. In this case, the anodic oxide film on the surface is
For an infrared ray having a wavelength of about 7 μm or more, the emissivity is not more than 0.
It is known to exhibit excellent radiation characteristics of 8 or more. In addition, since such an infrared radiator is made of a wrought aluminum alloy base material, it is lighter and less susceptible to cracking than a case where the whole is made of a ceramic material, is easy to perform various forming processes, and further has a heat conduction property. It has various advantages such as good properties.

[0006]

As described above, an infrared radiator obtained by forming an anodized film on the surface of a wrought aluminum alloy has excellent radiation characteristics at a wavelength of 7 μm or more, but has a wavelength of 7 μm or less. There was a drawback that the emissivity dropped extremely in the region. The anodic oxide film of wrought aluminum alloy has low heat resistance, and can be used for a long time at a surface temperature of about 150 ° C or more, or by a heat cycle between normal temperature and a high temperature of about 200 ° C or more. There is a problem that cracks are likely to occur. If such cracks occur in the anodic oxide film, the emissivity becomes unstable and the corrosion resistance decreases. If the thickness of the wrought aluminum alloy with anodized film is small,
There is also a problem that thermal deformation occurs due to long-time use at about 150 ° C. or more or use in a heat cycle, which causes the infrared radiator to warp or abnormally deform.

The present invention has been made in view of the above circumstances. As described above, the characteristics of an aluminum anodic oxide film exhibiting excellent radiation characteristics in a wavelength range of 7 μm or more are effectively utilized, and at the same time, the aluminum alloy is spread. Solved the disadvantages of conventional infrared radiators that formed anodized film on the material,
It is intended to provide a new infrared radiator. Specifically, not only the wavelength range of 7 μm or more but also 7 μm
m, it has excellent radiation characteristics even in a short wavelength range of less than m, and also has excellent heat resistance. It does not crack even at high temperatures exceeding 150 to 200 ° C, shows stable radiation performance up to about 300 ° C, and also generates thermal deformation. It is intended to provide a hard infrared radiator.

[0008]

In order to solve the above-mentioned problems, the infrared radiator according to the first aspect of the present invention basically comprises 2 to 50 vol% in a base material made of aluminum or an aluminum alloy. The base material is a composite sintered body in which ceramic fine powder particles are dispersed, and a thickness of 1
0 μm or more of an anodic oxide film is formed, and Al, Si, Mg, N
One or two or more selected from oxides of i, Cr, Zr, Cu, Fe, Mn, and Ti or composite oxides thereof or SiC are used.

[0009]

[0010] The infrared radiator of the invention according to claim 2 further comprises:
The infrared radiator according to claim 1, wherein the ceramic fine powder particles have a particle size of -325 mesh.

[0011]

FIG. 1 shows a conceptual configuration of the infrared radiator of the present invention.
Shown in In FIG. 1, a substrate 1 is made of a composite sintered body in which ceramic fine powder particles 3 are uniformly dispersed in a base material 2 made of aluminum or an aluminum alloy. This means that the ceramic fine powder particles 3 are evenly dispersed in the oxide film 4. Here, the anodic oxide film of the aluminum material itself has good infrared radiation characteristics, particularly excellent radiation characteristics of 7 μm or more, and further, the ceramic fine particles dispersed therein have excellent infrared radiation characteristics. It has excellent radiation characteristics, especially not only in the wavelength region of 7 μm or more but also in the short wavelength region of 7 μm or less, and the color tone of the film becomes turbid due to the dispersion of the ceramic fine powder particles, and the lightness is lowered. As a result of these acting synergistically, the anodic oxide film in which the ceramic fine powder particles are uniformly dispersed exhibits excellent infrared radiation characteristics, and particularly, excellent radiation not only in the wavelength region of 7 μm or more but also in the short wavelength region of 7 μm or less. Characteristics.

Further, since the fine ceramic powder particles uniformly dispersed in the anodic oxide film serve as a stress relaxation point, the film is less likely to crack due to thermal strain caused by a heat cycle or the like. Even so, crack propagation is prevented by the ceramic fine powder particles, so that crack growth is prevented. That is, cracks due to thermal strain are generated in the film, or the film is less likely to grow, so the heat resistance of the film is excellent, continuous use at high temperature for a long time, or heat cycle between normal temperature and high temperature. Without cracking for use,
It shows excellent infrared radiation characteristics stably up to about 300 ° C.

Further, the base material itself is made of a composite sintered body in which ceramic fine powder particles are dispersed in aluminum or an aluminum alloy, and such a composite sintered body is compared with a wrought material made of aluminum or an aluminum alloy. It has remarkably high strength, particularly high high-temperature strength, so that the substrate itself is less likely to be deformed due to thermal strain at a high temperature, and can be sufficiently used up to a high temperature of about 300 ° C. In addition, since the base material is a sintered body, an infrared radiator having a complicated shape that is difficult to form by cutting or the like,
It can be obtained accurately, easily and inexpensively.

Further, the anodic oxide film is formed by subjecting the surface of the base material to an anodic oxidation treatment. The anodic oxide film is integrated with the base material portion and both are completely adhered to each other. Since the ceramic fine powder particles are embedded in a state of being dispersed in the anodic oxide film, there is little risk of the ceramic fine powder particles falling off.

The mixing ratio of the ceramic fine powder particles in the base material must be in the range of 2 to 50 vol% in total. If the proportion of the ceramic fine powder is less than 2 vol%, the effect of obtaining excellent radiation characteristics cannot be sufficiently obtained even in a short wavelength range of 7 μm or less as described above. On the other hand, when the proportion of the ceramic fine powder exceeds 50 vol%, it becomes difficult to produce a sound sintered body with few defects, and the anodizing property is deteriorated, so that a uniform anodic oxide film can be formed. It will be difficult. In addition, even in the range of 2 to 50 vol%,
It is preferably within the range of 5 vol%, and especially between 10 and 2 vol%.
The optimum range is 0 vol%.

As the ceramic fine powder particles, A
1, Si, Mg, Ni, Cr, Zr, Cu, Fe, M
It is appropriate to use one or two or more mixed powders selected from the oxides of n and Ti or their composite oxides or SiC. Specifically, for example, Al ₂
O ₃ , SiO ₂ , MgO, SiC, NiO, Cr
Typical are ₂ O ₃ , ZrO ₂ , CuO, Fe ₂ O ₃ and MnO ₂ , and one or more of these may be used. According to experiments conducted by the present inventors, these ceramic fine powders are capable of imparting excellent infrared radiation characteristics even in a short wavelength range of 7 μm or less to an anodized film by being uniformly dispersed in the anodized film. It has been found to contribute to improving the heat resistance of the film. Further, in producing the infrared radiator of the present invention, it is essential to perform anodizing treatment with an acid or alkali aqueous solution, and therefore, the ceramic powder particles are dissolved by these treating solutions during the anodizing treatment,
Although it is necessary to avoid causing structural change, each of the above-listed ceramic materials has no particular problem in this regard.

Although only one of the above-mentioned ten types of ceramic materials may be used, the radiation characteristics of the ceramic materials differ at least slightly depending on the ceramic material. Therefore, a plurality of types of ceramic materials may be used in combination. It is desirable to average out the different emission characteristics of the ceramic material so as to exhibit, on average, excellent emission characteristics. When only one type of ceramic material is used, the mixing ratio of the ceramic fine powder is desirably 5 vol% or more in order to stably obtain excellent radiation characteristics even in a short wavelength range of 7 μm or less.

Further, it is desirable that the ceramic fine powder particles have a particle size of -325 mesh (under 325 mesh, that is, about 44 μm or less). If the particle size is larger than this, it is difficult to sufficiently obtain the above-described effects.

Although any material can be used as aluminum or aluminum alloy as a base material of the composite sintered body of the substrate, it is usually desirable to use pure aluminum having a purity of 99% or more. The particle size of the base material (aluminum or aluminum alloy) powder before sintering is not particularly limited, but is usually -3 as in the case of the ceramic fine powder particles.
It is preferable to set it to about 25 mesh.

The thickness of the anodic oxide film needs to be 10 μm or more. If the film thickness is less than 10 μm, the infrared radiation performance deteriorates, and it becomes difficult to stably obtain a high emissivity over a wide wavelength range.

The specific method for producing the composite sintered body of the substrate is not particularly limited, but a powder of aluminum or an aluminum alloy and one or more kinds of ceramic fine powders are mixed at a predetermined compounding ratio. After stirring, the mixed powder may be molded and sintered in the same manner as applied to a normal aluminum-based sintered material. Press molding, extrusion molding, rubber pressing, explosion An arbitrary method such as a powder compaction method using a force, a high-temperature pressing method (hot pressing), a method of continuously obtaining a strip, or a slip casting method can be applied.

Further, the method of anodizing the surface of the substrate is not particularly limited. For example, in the case of an acidic electrolyte, an inorganic acid such as sulfuric acid or oxalic acid, or an organic acid,
Further, the anodizing treatment may be performed by using an electrolytic bath such as a mixed acid thereof and using an arbitrary waveform such as a direct current, an alternating current, a combined AC / DC, or a superimposed AC / DC waveform as an electrolytic waveform.
However, from the viewpoint of economy and work efficiency, it is desirable to use a direct current in the sulfuric acid bath. If the base material is subjected to anodizing treatment in this way, the anodic oxide film grows in a state where the ceramic fine powder particles in the base material are taken in as it is, and the ceramic fine powder is uniformly dispersed in the film. Is formed.

[0023]

Embodiment No. 1 in Table 1 1 to No. One or more types of ceramic fine powder (grain size-325 mesh) and pure aluminum powder (grain size-32
After mixing and stirring, a cylindrical compact having a diameter of 50 mm and a length of 100 mm was prepared by a rubber press and sintered to obtain a sintered body. A 5 mm × 30 mm × 30 mm square plate-shaped specimen was cut out from each cylindrical sintered body, anodized by direct current using a sulfuric acid electrolytic bath, and subjected to 5 μm, 10 μm, 20 μm, 30 μm, and 40 μm.
Anodized films having various thicknesses of m were formed.

For each sample, a spectral emissivity curve from a wavelength of 3 μm to 30 μm was examined at a temperature of 300 ° C., and the total emissivity in that case was calculated. The results are shown in Table 2 for each sample for each film thickness of the anodic oxide film. In each sample, the sample number No. The spectral emissivity curve at 300 ° C. in the case of forming a 30 μm-thick anodic oxide film on the sample No. 5 (using a composite sintered body in which ten types of ceramic fine powders are blended) is shown by curve No. 2 in FIG. 5 and the sample number No. A film thickness of 30 for one sample (using a sintered body of aluminum alone without blending ceramic fine powder)
The spectral emissivity curve at 300 ° C. when an anodized film having a thickness of μm is formed is shown in FIG. Indicated by 1. Further, the sample number No. The spectral emissivity curves of the samples Nos. 4, 6, 7, 8, 9, and 10 under the same conditions as those described above are shown by curve Nos. 4,
Indicated by 6, 7, 8, 9, 10. For comparison, 30 μm was added to a conventional ordinary pure aluminum wrought material that was not a sintered body.
FIG. 3 shows a spectral emissivity curve at 300 ° C. when the anodic oxide film was formed.

[0025]

[Table 1]

[0026]

[Table 2]

As is clear from Table 2, No. 1 using a composite sintered body in which 10 kinds of ceramic fine powders were blended in a total of 15 vol% each in 1.5 vol%. In sample No. 5, the total emissivity at 300 ° C. was 0.3 when the anodic oxide film thickness was 30 μm.
No. 98, which is a remarkably high value, and uses a sintered body containing no ceramic fine powder. The same thickness of one sample,
It can be seen that it is significantly higher than the total emissivity of 0.68 at the same temperature. And this No. In the case of the sample No. 5, the curve No. of FIG. As shown in No. 5, it was confirmed that a high emissivity was stably obtained even in a short wavelength range of 7 μm or less.

No. 2-No. Sample No. 4 used a sintered body in which two types of ceramic fine powder were mixed in a total of 10 vol%. No. 5 using a sintered body which is lower than the sample of No. 5 but does not contain the ceramic fine powder. The value of the total emissivity is significantly higher than that of the sample No. 1 (0.
85) was obtained with a film thickness of 30 μm. These sample Nos.
2-No. No. 4 among No. 4 FIG. 2 shows a spectral emissivity curve for No. 4 which shows that a relatively stable high emissivity is obtained in a short wavelength range of 7 μm or less.

Further, in the case of 6-No. All 10 samples used one kind of alumina as ceramic fine powder,
The blending amount was changed in the range of 1 to 15 vol%. As shown in Table 2, if the blending amount was 2 vol% or more, the total emissivity was 0.7 or more at a film thickness of 10 μm or more. It can be seen that a high emissivity can be obtained, and a relatively high emissivity can be obtained even in a short wavelength region as shown in FIG.

And also No. 11-No. Sample No. 19 used a sintered body in which one type of ceramic fine powder was blended at 5 vol%. Total emissivity values higher than one sample were obtained.

[0031]

According to the infrared radiator of the present invention, a high infrared emissivity can be obtained stably even in a short wavelength region of 7 μm or less, as in a wavelength region of 7 μm or more. High emissivity can be obtained stably without cracking of the anodic oxide film on the surface even when used at a high temperature of about 300 ° C.,
In addition, since the base material itself has excellent heat resistance and high-temperature strength, 3
Even at a high temperature of about 00 ° C, there is little risk that the substrate will be warped or deformed due to thermal strain. Eventually, it can be used continuously at a high temperature of about 300 ° C or a heat cycle between normal temperature and high temperature. Regardless of the above, it can be used stably.

[Brief description of the drawings]

FIG. 1 is a schematic view conceptually showing a cross-sectional structure of an example of an infrared radiator of the present invention.

FIG. 2 is a characteristic diagram showing a spectral emissivity curve of the infrared radiator of the example.

FIG. 3 is a characteristic diagram showing a spectral emissivity curve of a conventional infrared radiator using a normal aluminum wrought material.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-19796 (JP, A) JP-A-1-165796 (JP, A) JP-A-63-145797 (JP, A) (58) Investigation Field (Int. Cl. ⁷ , DB name) C25D 11/00 C25D 11/38

Claims (2)

(57) [Claims] An Al, Si, Mg, Ni, Cr, Z metal in a base material made of aluminum or an aluminum alloy.
Composite firing in which one to two or more ceramic fine powder particles selected from oxides of r, Cu, Fe, Mn, Ti or their composite oxides or SiC are dispersed in 2 to 50 vol%. An infrared radiator comprising: a base material; and an anodic oxide film having a thickness of 10 μm or more formed on a surface of the base material. 2. The infrared radiator according to claim 1, wherein said ceramic fine powder particles have a particle size of -325 mesh.