JPH05311307A - Far infrared radiation emitter and its production - Google Patents

Abstract

PURPOSE:To produce a far infrared radiation emitter excellent in far infrared radiation characteristics, substantially free from cracking even at high temp., capable of being formed into complicated shapes by various manufacturing methods, and prepared by using an aluminum alloy as a base material. CONSTITUTION:This far infrared radiation emitter is prepared by forming a black anodic oxidation film of >=10mum thickness on the surface of a base material composed of an Al-Si alloy essentially containing 1-<3wt.% Si. The state of Si precipitation is controlled so that, particularly, >=80% of precipitated Si grains have >=0.05mum grain size and the relation in [residual content of solid-solution Si] (wt.%)<=[Si content] (wt.%)-0.5 is satisfied when Si content is less than 1.5wt.% and also the relation in [residual content of solid-solution Si]<=1 is satisfied when Si content is 1.5wt.% or above.

Description

Detailed Description of the Invention

[0001]

This invention relates to heating, cooking, drying,
The present invention relates to a member that radiates far infrared rays for heat treatment of materials and various other types of radiant heating, and more particularly to a far infrared radiator having an anodized film formed using an aluminum alloy as a base material and a method for manufacturing the same. ..

[0002]

2. Description of the Related Art Generally, in heaters using far infrared rays, the far infrared ray emissivity of the radiator is high, and
At a relatively low surface temperature of 0 ° C. or higher, the amount of radiation in the visible region is small, but the amount of radiation in the far infrared region is large.
As a radiator satisfying such requirements, those made of various ceramic materials such as alumina, graphite and zirconia have been put into practical use. Among these materials, it is known that alumina has excellent performance in terms of far infrared radiation characteristics as compared with other ceramic materials.

However, conventional far-infrared radiators made of ceramic materials have a large weight, are easily broken, and it is difficult to make thin ones, and the thermal conductivity is poor, so that the radiator is heated. There was a problem such as inefficiency.

Therefore, a radiator in which ceramics are sprayed on the surface of a metal substrate has been put into practical use, but in this case, the manufacturing cost is high and it is difficult to obtain a thin plate or a radiator having a complicated shape. There is a problem such as.

By the way, regarding alumina among ceramic materials, it is possible to easily form a layer made of alumina on the surface of an aluminum substrate by anodizing the surface of aluminum to form an alumite film (anodic oxide film). You can In this case, since the base material is aluminum, the thermal conductivity is good, and since the anodic oxide film on the surface is alumina, the far-infrared radiation characteristics are also good, and therefore both the thermal conductivity and the far-infrared radiation characteristics are good. Can meet. Therefore, recently, a far-infrared radiator in which the surface of the aluminum base material is anodized as described above has been tried.

[0006]

However, the conventional radiator having an anodizing treatment on the surface of the aluminum base material is limited due to the following drawbacks (1) to (3). There is a problem that it can be applied only to the intended use. (1) At 200 ° C. or higher, cracks are likely to occur in the alumite coating, resulting in unstable emissivity and poor corrosion resistance. (2) Emissivity is low in the wavelength range of 3 to 7 μm. (3) It is difficult to obtain a member having a complicated shape by casting or various plastic workings.

Regarding the above problem (1), the problem can be solved by using an aluminum alloy capable of forming an anodized film which is unlikely to cause cracks even at a high temperature of 200 ° C. or higher. Aluminum alloys are not currently known as far infrared radiators.

Regarding the problem described in (2) above,
It is known that the emissivity in the above wavelength range can be improved by coloring the anodic oxide film on the surface of the aluminum substrate in the infrared radiator with a dye. However, in these methods, the number of coloring steps is increased and the cost is increased, and further, at a high temperature of 200 ° C. or higher, the dye or the like is decomposed or the film is cracked, and the emissivity in that wavelength band becomes unstable. However, there is a problem that the radiation characteristic is deteriorated.

Regarding the above-mentioned problem (3), the problem can be solved by using an aluminum alloy which can be cast and various plastic workings, but it is possible to carry out plastic workings such as casting, extrusion and forging, and moreover, stable by anodizing treatment. The reality is that an aluminum alloy that can turn black and obtain good far infrared radiation characteristics has not been known so far.

The present invention has been made in view of the above circumstances, and cracks due to thermal strain are unlikely to occur in an anodized film even at a high temperature of 200 ° C. or higher, and far-infrared radiation characteristics are excellent, and casting, forging and extrusion are performed. It is an object of the present invention to provide a far-infrared radiator having an aluminum alloy as a base material, which can be manufactured by various processing methods such as to obtain a member having a complicated shape.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies and studies to solve the above-mentioned problems, and as a result, made an aluminum alloy as a base material a component system containing a small amount of Si,
Furthermore, they have found that the aforementioned problems can be solved by appropriately adjusting the dispersed state of precipitated Si particles, and have completed the present invention.

Specifically, the far-infrared radiator of the present invention according to claim 1 uses as an base material an alloy containing Si of 1 wt% or more and less than 3 wt%, and the balance of Al and unavoidable impurities. Is characterized in that a black anodic oxide film having a film thickness of 10 μm or more is formed on its surface.

The far infrared radiator according to the second aspect of the present invention contains Si in an amount of 1 wt% or more and less than 3 wt%, and Fe.
0.05-1.5 wt%, Mg 0.05-1.0 wt%, C
u 0.05-1.0 wt%, Mn 0.05-1.0 wt%,
Ni0.05-1.0wt%, Cr0.05-0.5wt
%, V0.05-0.5wt%, Zr0.05-0.5wt
%, Ti 0.005 to 0.2 wt%, one or two
An alloy containing at least one species and the balance being Al and inevitable impurities is used as a base material, and a black anodic oxide film having a thickness of 10 μm or more is formed on the surface of the base material. ..

Furthermore, the far-infrared radiator of the invention described in claim 3 is used as a base material in the far-infrared radiator of claim 1 or 2, and the total number of deposited Si particles in the base material is 80. % Or more of the precipitated Si particles is 0.05 μm or more, and the amount of residual solid solution Si is Si.
Depending on the content, when the Si content is 1 wt% or more and less than 1.5 wt%, the residual solid solution Si amount (wt%) ≦ Si content (wt%) − 0.5 is satisfied, and the Si content is When the content is 1.5 wt% or more and less than 3 wt%, the residual solid solution Si amount (wt%) ≦ 1 is satisfied.

Further, the method for producing a far-infrared radiator according to a fourth aspect of the present invention contains Si in an amount of 1 wt% or more and less than 3 wt%, and if necessary, Fe 0.05 to 1.5 wt%,
Mg0.05-1.0wt%, Cu0.05-1.0wt
%, Mn 0.05 to 1.0 wt%, Ni 0.05 to 1.0
wt%, Cr 0.05 to 0.5 wt%, V 0.05 to 0.5
wt%, Zr 0.05-0.5 wt%, Ti 0.005-
An alloy containing one or more of 0.2 wt% and the balance consisting of Al and unavoidable impurities is cast, and if necessary, hot working and / or cold working is performed to obtain a predetermined alloy. When a base material having a size is obtained and then anodized to form an anodized film of 10 μm or more on the surface, after the casting, or after hot working, or during or after cold working, 250 to By heating to a temperature in the range of 550 ° C., the Si content in the total number of precipitated Si particles is 80% or more and the precipitated Si particles are 0.05% or more.
If the residual solid solution Si content is 1 μm or more and less than 1.5 wt% depending on the Si content, the residual solid solution Si content (wt%) ≦ Si content ( wt%)-0.5 and the Si content is 1.5 wt% or more and 3 wt
When it is less than%, it is characterized in that precipitation is performed so as to satisfy the residual solid solution Si amount (wt%) ≦ 1.

[0016]

The far-infrared radiator of the present invention is basically 1 wt.
% -Less than 3 wt% Si is used as a base material, and a black anodic oxide film is formed on the surface of the base material.

In such an aluminum alloy containing Si in an amount of 1 wt% or more and less than 3 wt%, metal Si particles are dispersed and precipitated in the structure by an appropriate heat treatment as will be described later, and the surface of the base material is Is anodized, the precipitated Si particles are incorporated into the anodized film as metal Si particles. And metal Si is contained in the anodized film.
Since the particles are dispersed, the incident light is scattered and absorbed, and the radiation characteristic of far infrared rays is improved. Further, since visible light is also absorbed, the visual color tone becomes black. Further, in the process of growing the anodized film (porous layer) during the anodizing treatment, the pores grow while avoiding the metallic Si particles, so that the pores in the film have a branched structure, and such branching occurs. Due to the pore structure, scattering absorption of incident light in the anodic oxide film is improved, and the far infrared radiation characteristics are further improved.

Furthermore, the metallic Si particles dispersedly present in the anodized film also function as a stress relaxation point, and the branched structure of pores as described above has a high strain absorbing ability,
Therefore, cracks are unlikely to occur, and even if cracks occur, their propagation is blocked.

Here, the reasons for limiting the component composition in the base aluminum alloy of the far infrared radiator of the present invention will be described.

Si: Si is a fundamentally important alloying component in the present invention. Si is solid-dissolved at the time of casting depending on the amount added, and the solid-solution Si is precipitated as metal Si by heat treatment. As described above, the precipitated Si particles are taken into the anodized film as metal Si particles during the anodizing treatment, contribute to the improvement of far infrared radiation characteristics through scattering and absorption of incident light, and prevent cracks from occurring. Contribute. Further, the metal Si particles contribute to the formation of a branched structure in the pores of the film as described above, and also function as a stress relaxation material, which also contributes to the improvement of far infrared radiation characteristics and the prevention of cracks. If the amount of Si in the base aluminum alloy is less than 1 wt%, the volume ratio of metal Si particles in the anodized film is small, and the radiation characteristics of far infrared rays are insufficient. On the other hand, when the amount of Si is 3 wt% or more, the number of eutectic Si particles during casting increases, and the corrosion resistance of the anodized film decreases. Therefore, the amount of Si is set to be in the range of 1 wt% or more and less than 3 wt%.

As the constituent element of the aluminum alloy as the base material, basically, in addition to the above Si, Al and inevitable impurities may be used. That is, even if the elements other than Al and Si are treated as unavoidable impurities and the amount is less than the lower limit value defined in claim 2, the intended object of the present invention can be achieved.

However, as defined in claim 2, in order to improve the strength, Fe, Mg, Cu, Mn, Ni, Cr,
You may contain 1 type, or 2 or more types of V, Zr, and Ti. The reason for adding these is as follows.

Fe: Fe is effective for improving strength and refining crystal grains. If the Fe content is less than 0.05 wt%, the effect cannot be obtained, and if it exceeds 1.5 wt%, the strength and corrosion resistance of the anodic oxide film are deteriorated. On the other hand, if the amount of Fe exceeds 1.5 wt%, Si combines with Fe to increase the amount of Al—Fe—Si based intermetallic compounds, which deteriorates the far infrared radiation characteristics. Therefore, the amount of Fe when adding Fe is 0.05
˜1.5 wt%.

Mg: Mg also contributes to the strength improvement. If the amount of Mg is less than 0.05 wt%, the effect cannot be obtained, while 1.
If it exceeds 0 wt%, Mg and Si are combined to increase the amount of Mg ₂ Si produced and the far infrared radiation characteristics deteriorate. Therefore, when adding Mg, the amount of Mg should be 0.05 to 1.0 wt.
Within the range of%.

Cu: The addition of Cu also contributes to the improvement of strength.
If the Cu content is less than 0.05 wt%, the effect cannot be obtained, while if it exceeds 1.0 wt%, the castability, corrosion resistance, and plastic workability deteriorate. Therefore, when Cu is added, the amount of Cu is set within the range of 0.05 to 1.0 wt%.

Mn: Mn contributes not only to the improvement of strength but also to the refinement of crystal grains and the improvement of heat resistance. If the amount of Mn is less than 0.05 wt%, these effects cannot be obtained. On the other hand, if the amount of Mn exceeds 1.0 wt%, Mn is combined with Si to form Al-Mn.
The amount of -Si-based intermetallic compound produced increases, and the far infrared radiation characteristics deteriorate. Therefore, M when adding Mn
The amount of n was set in the range of 0.05 to 1.0 wt%.

Ni: Ni contributes not only to improving strength but also to improving heat resistance. If the amount of Ni is less than 0.05 wt%, these effects cannot be obtained, while if it exceeds 1.0 wt%, the corrosion resistance decreases. Therefore, when Ni is added, the amount of Ni is set within the range of 0.05 to 1.0 wt%.

Cr, Zr, V: These elements contribute to the improvement of strength and also to the refinement of crystal grains. If the content is less than 0.05% by weight, the effect cannot be obtained. On the other hand, if the content exceeds 0.5% by weight, a coarse intermetallic compound is produced and the strength is rather lowered. Therefore, Cr, Zr, V
In the case of adding one kind or two kinds or more, the addition amount is in the range of 0.05 to 0.5 wt% as a single amount. When rolling, extrusion, or forging of slabs, billets, etc. is applied, the addition amount of these elements is 0.3 wt.
If it exceeds 0.1%, the plastic workability is deteriorated and the production becomes difficult.

Ti: Ti contributes to refinement of the structure through refinement of ingot crystal grains. If the Ti content is less than 0.005 wt%, the effect cannot be obtained, while if it exceeds 0.2 wt%, a coarse intermetallic compound is formed, which is not preferable. Therefore, the amount of Ti when Ti is added is 0.005 to 0.2 wt.
Within the range of%. In addition, in order to refine the ingot crystal grains,
It is effective to make B coexist with Ti. In this case, if the amount of B is less than 1 ppm, the effect cannot be obtained.
Since the effect is saturated if it exceeds 00 ppm, the amount of B when B is added together with Ti is preferably in the range of 1 to 100 ppm.

In addition to the above elements, it is not particularly problematic to add Be in an amount of about 1 to 100 ppm for preventing oxidation during dissolution. Further, Zn is an element that is inevitably mixed in when scrap is used as a raw material.
However, if the content is about 1.0 wt% or less, the characteristics such as far-infrared radiation characteristics are not adversely affected. In addition, other elements are 1wt% in total
Far-infrared radiation characteristics are not adversely affected as long as the trace amount is below.

Next, the structure of the base aluminum alloy of the far-infrared radiator of the present invention, in particular, the dispersed state of metal Si particles will be described.

As already described, in a system aluminum alloy containing 1 wt% or more and less than 3 wt% Si, Si is solid-dissolved during casting depending on the amount added. Then, when heat treated after casting, the solid solution Si is precipitated as metallic Si from the Al matrix. The precipitated Si particles remain in the coating as metal Si particles as they are even after the anodizing treatment. And the metallic Si in this anodized film
The particles have a great influence on the infrared radiation characteristics and the crack resistance of the anodized film.

That is, since the metallic Si particles are dispersed in the anodized film, incident light is scattered and absorbed, the radiation characteristics of far infrared rays are improved, and visible rays are also absorbed.
The visual color also becomes black. Furthermore, during the process of growing the pores during the anodizing process, the pores grow while avoiding the metallic Si particles, so that the pores have a branched structure, which promotes scattering and absorption of incident light in the anodized film, and The infrared radiation characteristics are further improved.

On the other hand, the metal Si particles in the anodic oxide film also function as stress relaxation points, and the branched structure of the pores has a high strain absorbing ability, and thus cracks are less likely to occur, and if cracks occur, Its transmission is blocked.

Here, in order to obtain good far-infrared radiation characteristics, the size (particle size) of the deposited metal Si particles and the deposition amount thereof are important. That is, first, it is necessary that 80% or more of all the precipitated Si particles have a particle size of 0.05 μm or more. When the diameter of the precipitated Si particles is less than 0.05 μm, the scattering absorption of visible rays and far infrared rays is insufficient, good radiation characteristics cannot be obtained, and the yellowishness becomes strong visually. It cannot be called black. Even if precipitated Si particles of 0.05 μm or more exist, the same problem as described above occurs if the number ratio is less than 80%. Therefore, in order to achieve the intended object of the present invention, it is essential that the precipitated Si particles having a particle size of 0.05 μm or more account for 80% or more of the total number of precipitated Si particles.

Further, not only the particle size of the precipitated Si particles but also the amount of precipitation thereof is important. In Al-Si alloys, Si
Is generally the morphology of crystallized Si produced in the casting stage, the morphology of precipitated Si deposited in the subsequent heat treatment, and the solid solution Si.
Exists in the form of. At the stage of casting, crystallized Si and solid solution S
Although existing in the state of i, metallic Si is precipitated from the solid solution Si by the subsequent heat treatment. The amount of Si that forms a solid solution during casting is approximately 0.5 wt% or more. On the other hand, according to the research conducted by the present inventors, it has been confirmed that the amount of precipitated Si required to effectively radiate far infrared rays is approximately 0.5 wt%. Therefore, the amount of precipitated metal Si particles may be set to 0.5 wt% or more with respect to the total weight of the alloy. However, in an actual alloy, it is difficult to directly investigate the amount of precipitated Si particles. That is, the total amount of metallic Si in the alloy is S insoluble in hydrochloric acid as shown in FIG.
Although it is possible by i analysis, the metal Si in this case includes not only precipitated Si but also large crystallized Si at the time of casting, and since this large crystallized Si does not contribute to the improvement of far infrared radiation characteristics, It is necessary to exclude crystallized Si out of metallic Si. Therefore, first, the metal Si is analyzed in the as-cast state to obtain the amount of crystallized Si, after which the heat treatment for Si precipitation is performed, and then the metal Si is analyzed again,
It is considered possible to obtain the amount of precipitated Si by obtaining the difference. However, in general, it is difficult to perform the analysis at the same location after the casting and after the heat treatment. Therefore, the amount of precipitated Si obtained as described above should be used as a guide for the far-infrared radiation characteristics. I can't. Therefore, the present inventors tried to estimate the amount of precipitated Si by the amount of residual solid solution Si after Si precipitation.
As a result, it was found that when the amount of residual solid solution Si depends on the total amount of Si contained, the amount of precipitated Si becomes about 0.5 wt% or more, and sufficiently excellent far infrared radiation characteristics can be obtained. ..

That is, in the Al-Si type alloy, paying attention to the fact that the eutectic Si crystallizes out when the Si amount is about 1.5 wt% or more, and the added Si is added with the Si amount of 1.5 wt% as the boundary.
The relationship between the amount (total Si content), the amount of residual solid solution Si, and the amount of precipitated Si was studied. Here, the residual solid solution Si amount is
It was determined by subtracting the metallic Si amount (for example, by the method shown in FIG. 1) and the Si amount in the total intermetallic compound (for example, by the method shown in FIG. 2) from the total Si content (Si added amount).
This is because Si crystallizes and precipitates as metallic Si, and F
It is common to form compounds with e, Mn, Mg, etc.,
Therefore, an error occurs between the value obtained by subtracting the metallic Si amount from the total Si content and the residual solid solution Si amount by the amount corresponding to the Si amount in the total intermetallic compound.

As a result of examining the relationship between the residual solid solution Si amount and the total Si content in this way, first, when the Si content is 1 wt% or more and less than 1.5 wt%, the residual solid solution Si amount ( wt%) ≤total Si content (wt%)-0.
5 and the Si content is 1.5 wt% or more, 3.0 wt.
%, If the amount of residual solid solution Si (wt%) ≦ 1.0 is satisfied, the total amount of precipitated Si is 0.5 wt% or more, and excellent far infrared radiation characteristics can be obtained. It was That is, when these relationships are not satisfied, the amount of precipitated Si becomes less than 0.5 wt%, and
Even if the size of the particles is 0.05 μm or more, the far-infrared radiation characteristics will be insufficient.

In order to obtain the above-mentioned precipitation state of the precipitated Si particles, it is necessary to carry out the precipitation treatment after casting or at a later stage. That is, in the method for producing a far infrared radiator of the present invention, the base material is cast from an alloy having the above-described composition, or after casting, if necessary, hot forging, hot extrusion, hot rolling, etc. It can be obtained by performing hot working and / or cold working such as cold rolling. However, a precipitation treatment may be performed at a stage after casting in the manufacturing process of the base material, or hot working and / or post casting may be performed. Alternatively, when cold working is performed, the precipitation treatment may be performed after hot working, in the middle of cold working, or after cold working.

This precipitation treatment may be performed by heating to a temperature in the range of 250 to 550 ° C. for 0.5 to 24 hours. If the temperature of the precipitation treatment is less than 250 ° C., the size of the precipitated Si particles becomes small and the particle size tends to be less than 0.05 μm.
If the temperature exceeds ℃, re-dissolution of once-precipitated Si occurs,
The absolute amount of precipitation is insufficient. In addition, the time for the precipitation treatment is 0.
If it is less than 5 hours, it becomes difficult to sufficiently deposit metallic Si from the solid solution Si, while if it exceeds 24 hours, it is economically wasteful. Such precipitation treatment may be carried out independently or in combination with other heat treatment. That is, when hot working is performed after casting, the precipitation treatment can also be performed in combination with ingot heating before the hot working, or between hot working and cold working or during cold working. In the case of performing the intermediate annealing in, the precipitation treatment can be performed in combination with the intermediate annealing, and in the case of performing the final annealing after the cold working, the precipitation treatment can be performed in combination with the final annealing. The heat treatment may be performed under the condition that the above-described precipitation state of precipitated Si particles is obtained.

Next, the anodizing treatment applied to the aluminum alloy substrate will be described.

When an anodizing treatment is applied to the aluminum alloy substrate having the above-mentioned chemical composition and metal structure, a black anodic oxide film is formed and excellent far infrared radiation characteristics are exhibited. That is, during the anodizing treatment, the anodized film grows with the metallic Si particles remaining in the film as they are.
Therefore, the growth of pores in the film is hindered by the metal Si particles, and a porous film having branched fine pores is produced. Further, the metallic Si particles existing as they are in the anodized film and the fine pores branched as described above scatter and absorb the incident light, and as a result, the visual color tone becomes black and the far-infrared radiation characteristics become good. .. Further, the fine branch structure and the metal Si particles in the coating function as a relaxation point for thermal stress, so that the coating is less likely to crack and cracks occur up to temperatures as high as 500 ° C. There is no need to use it.

Here, the film thickness of the anodized film must be 10 μm or more. That is, in order to show a blackness with a Munsell value of 4.5 or less, the film thickness needs to be 10 μm or more. Further, when the film thickness is 10 μm or more, stable high blackness can be obtained, and thus stable far infrared radiation characteristics can be obtained in a wide wavelength range.

The conditions of the anodizing treatment are not particularly limited, and an inorganic acid such as sulfuric acid or oxalic acid, an organic acid, or an electrolytic bath of a mixed acid thereof is used.
The anodic oxidation treatment may be performed using an arbitrary waveform such as direct current, alternating current, alternating / direct combination, or alternating / superimposed waveform. However,
From the viewpoint of economy and work efficiency, it is preferable to use a direct current in a sulfuric acid bath. Also, degreasing before anodizing,
It is common to perform pretreatment such as caustic etching,
When caustic etching is performed, it is common to subsequently perform desmutting treatment with an acid such as nitric acid. In addition, it is needless to say that mechanical pretreatment such as cutting, acid cleaning, chemical polishing, hairline processing, and sailboat blasting may be carried out if necessary.

[0045]

【Example】

Example 1 Alloys having compositional compositions shown in alloy numbers 1 to 3 in Table 1 2
A sand mold was cast into a shape of 0 mm × 200 mm × 200 mm. Prior to casting, degassing treatment was performed in advance. A part of the obtained casting was used as it was, and the rest was heat-treated at 400 ° C. or 150 ° C. for 5 hours, and then gradually cooled at a cooling rate of 10 ° C./hr.

After mechanically cutting the surface of each material, etching was performed with 10% caustic soda at 60 ° C. for 5 minutes,
After washing with water, desmutting was performed using 30% nitric acid. Then, using a 15% sulfuric acid bath, the current density is 1.5 A / dm
^2. Anodizing treatment was performed at an electrolysis temperature of 20 ° C.

The Munsell brightness was measured for each material after the anodizing treatment, and the spectral emissivity at 300 ° C. was measured. Here, as the far-infrared radiation characteristic of a conventional general anodic oxide film, since the spectral emissivity at a wavelength of 3 to 7 μm is usually inferior, the spectral radiation at a typical wavelength of 6 μm within that range is obtained. The rate was measured. In addition, Si of each material
The precipitate size and the amount of solid solution Si were examined. The Si precipitate size was first determined using an optical microscope, and further, when it was considered that a precipitate near 0.05 μm, which was difficult to determine by an optical microscope, was deposited, it was determined using a transmission electron microscope.
For the amount of solid solution Si, the amount of metallic Si in the material is analyzed by the method shown in FIG. 1, and the amount of Si in the total intermetallic compound is analyzed by the phenol residue method shown in FIG.
It was determined by subtracting the former amount of metallic Si and the latter amount of Si in the intermetallic compound from (i addition amount). The results are shown in Table 2. Here, when the value of the Munsell lightness is 4.5 or less, it can be determined that the Munsell lightness has a sufficient black color. Further, when the spectral emissivity at a wavelength of 6 μm is 0.7 or more, it can be determined that the far-infrared radiation characteristic is good.

[0048]

[Table 1]

[0049]

[Table 2]

In Example 1, 40 of alloy numbers 1 and 2
The 0 ° C. heating material satisfies the condition range defined by the present invention regarding Si, and the anodic oxide film thickness is 10
In the case of 29 μm which exceeds μm, it can be seen that the Munsell brightness and the spectral emissivity satisfy the predetermined values, that is, the visual color tone is sufficiently black and the far infrared radiation characteristic is excellent. Further, among the alloy Nos. 1 and 2 heated at 400 ° C., the material having an anodized film thickness of more than 10 μm did not show any cracks when the surface was visually observed after heating at 500 ° C. after anodizing treatment. ..

However, the as-cast alloy No. 1 and No. 2 alloys, the alloy No. 1 400.degree. C. heating material with an anodized film thickness of 7 .mu.m less than 10 .mu.m, and the alloy No. 3 materials were anodized. When the surface was observed after heating to 500 ° C. after the treatment, many cracks were visually observed. Further, among the 400 ° C. heating materials of Alloy No. 1, the material having an anodized film thickness of 7 μm satisfied the conditions concerning Si satisfying the conditions specified in the present invention, but the far infrared radiation characteristics were inferior. Note that the alloys 1, 2, and 3 heated at 150 ° C. have a slightly darker color tone than the as-cast material after visual inspection after anodizing treatment, but as long as observed with an optical microscope, No precipitated Si was found in the dendrite portion. Then, when this portion was observed with an electron microscope, the presence of fine precipitated Si particles of 0.01 to 0.03 μm or 0.01 to 0.02 μm was recognized. Even if they are precipitated, these fine precipitated Si particles do not work as an absorption point for far infrared rays.
Far-infrared radiation characteristics are not improved.

Example 2 With respect to the alloy having the composition shown in alloy No. 4 in Table 1,
A 400 mm x 1000 mm x 3500 mm rolling ingot (slab) was DC cast. After chamfering the obtained slab, 4
It was heated to 00 ° C. for 2 hours and then hot rolled. After hot rolling to a thickness of 4 mm, it was cold rolled to a thickness of 1 mm, annealed at 350 ° C. for 2 hours, and then anodized in the same manner as in Example 1.

Regarding the material after anodizing treatment, Example 1
The same measurement and structure observation were performed. The results are shown in Table 2.

As shown in Table 2, in the case of Example 2, the rolled plate was annealed after slab heating and hot rolling / cold rolling, and the conditions of heat treatment (slab heating or annealing) during the manufacturing process were changed. By optimizing these heat treatments, these heat treatments could also serve as precipitation treatments, and a proper Si precipitation state could be obtained. Also in this case, far-infrared radiation characteristics were excellent, and no crack was observed even when the surface was visually observed after heating to 500 ° C. after the anodizing treatment.

Example 3 An alloy having the composition shown in alloy No. 5 in Table 1 was fed between water-cooled rolls to cast a thin plate continuous casting and rolling coil having a thickness of 7 mm and a width of 900 mm. This coil was subsequently cold-rolled to a thickness of 2 mm and heated at 390 ° C. for 2 hours as final annealing.
The obtained material was anodized in the same manner as in Example 1. For each material after the anodizing treatment, measurement and structure observation were performed in the same manner as in Example 1. The results are shown in Table 2.

In the case of this Example 3, the final annealing after cold rolling also serves as a precipitation treatment, whereby an appropriate Si is obtained.
A precipitated state was obtained. And after anodizing treatment at 500 ℃
No crack was observed even when the surface was visually observed after heating to 0. Further, in this case, FIG.
Spectral emissivity curves for wavelengths up to 5 μm are also shown. As is clear from FIG. 3, a good spectral emissivity was obtained over the entire wavelength range, and no decrease in emissivity was observed in the wavelength range of 3 to 7 μm, which is typical of ordinary anodic oxide coatings.

From the above examples, the alloys within the compositional range defined by the present invention will not only show excellent far infrared radiation characteristics if they satisfy the above Si precipitation conditions. It is clear that the anodic oxide film does not crack even when heated to 500 ° C., and is therefore effective as a far-infrared radiator at high temperatures up to about 500 ° C. It is also clear that it is possible to manufacture a material having excellent far-infrared radiation characteristics by any manufacturing means such as casting, forging, rolling and extrusion.

[0058]

According to the far-infrared radiator of the present invention, excellent far-infrared radiation characteristics are obtained, and in particular, radiation characteristics in a wavelength range of 3 to 7 μm, which are considered to be inferior to conventional aluminum anodic oxide coatings. It is excellent, and cracks due to thermal strain do not occur in the anodized film up to a high temperature of about 500 ° C.
It is effective as a far-infrared radiator at high temperatures up to about
Furthermore, since the far-infrared radiation characteristics are excellent by appropriately dispersing the precipitated Si particles in the anodic oxide film, there is no fear that the far-infrared radiation characteristics deteriorate with time. And the far-infrared radiator of the present invention also includes casting, forging, rolling,
It can be manufactured by any manufacturing means such as extrusion, so that a far-infrared radiator having an arbitrary shape can be obtained according to the application and place of use, and a radiator having a complicated shape can also be easily obtained. . As described above, the far-infrared radiator of the present invention has various excellent merits, and therefore, the far-infrared radiator has an extremely wide range in combination with the advantage of lightness due to the light weight of the base aluminum alloy. Can be put to practical use.

[Brief description of drawings]

FIG. 1 is a flowchart showing an example of a method for analyzing the amount of metallic Si in an aluminum alloy.

FIG. 2 is a flowchart showing an example of a method for analyzing the amount of Si in all intermetallic compounds in an aluminum alloy.

FIG. 3 is a graph showing a spectral emissivity curve for a material of Alloy No. 5 of Example 3.

Claims (4)

[Claims] 1. An alloy containing Si in an amount of 1 wt% or more and less than 3 wt% and the balance of Al and inevitable impurities is used as a base material, and a black anodic oxide film having a thickness of 10 μm or more is formed on the surface of the base material. Far infrared radiator characterized by being present. 2. Si 1 wt% or more and less than 3 wt%, Fe0.05-1.5 wt%, Mg0.05-1.0 wt
%, Cu 0.05 to 1.0 wt%, Mn 0.05 to 1.0
wt%, Ni0.05-1.0 wt%, Cr0.05-0.
5 wt%, V0.05-0.5 wt%, Zr0.05-0.
5 wt%, 0.005 to 0.2 wt% of Ti 0.005 to 0.2 wt%, containing 1 or 2 or more, the balance is Al and unavoidable impurities as the base material, and the film thickness 10μ on the surface of the base material.
A far-infrared radiator having a black anodic oxide coating of m or more formed. 3. Of the total precipitated Si particles in the substrate, 80% or more of the precipitated Si particles have a size of 0.05 μm or more, and the amount of residual solid solution Si is Si.
Depending on the content, when the Si content is 1 wt% or more and less than 1.5 wt%, the residual solid solution Si amount (wt%) ≦ Si content (wt%) − 0.5 is satisfied, and the Si content is The far-infrared radiator according to claim 1 or 2, wherein the content of residual solid solution Si (wt%) ≤ 1 is satisfied when the content is 1.5 wt% or more and less than 3 wt%. 4. Si is contained in an amount of 1 wt% or more and less than 3 wt%, and if necessary, Fe 0.05 to 1.5 wt%, Mg 0.
05-1.0 wt%, Cu 0.05-1.0 wt%, Mn
0.05-1.0 wt%, Ni 0.05-1.0 wt%, C
r0.05-0.5wt%, V0.05-0.5wt%, Z
r0.05-0.5wt%, Ti0.005-0.2wt%
A base material having a predetermined size, which is obtained by casting an alloy containing one or two or more of the above, with the balance being Al and inevitable impurities, and further subjecting it to hot working and / or cold working as necessary. , And then anodize the surface to give 1
Upon forming the anodized film having a thickness of 0 μm or more, Si is heated to a temperature in the range of 250 to 550 ° C. after the casting, or after the hot working, or during or after the cold working, 80% or more of the total precipitated Si particles are 0.05 μm or more, and the amount of residual solid solution Si is 1 wt% or more and 1.5 wt% or more depending on the Si content. When the amount is less than 1, the residual solid solution Si content (wt%) ≤ Si content (wt%)-0.5 is satisfied, and the Si content is 1.5 wt% or more and 3 wt%.
When it is less than%, the far-infrared radiator is produced by depositing so as to satisfy the residual solid solution Si amount (wt%) ≦ 1.