JPH06200398A - Far-infrared ray radiator and its manufacture - Google Patents

Abstract

PURPOSE:To provide a far-infrared ray radiator consisting of an aluminum alloy as the base material, which can be manufactured even in some complicated shapes by using various manufacturing methods and hardly generates cracks even at a high temp. and further has excellent far-infrared radiation characteristics, and the anodically oxidized film of which has a gray color tone, and to provide the manufacturing method of the far-infrared radiator. CONSTITUTION:This far-infrared radiator is manufactured by forming the gray color anodically oxidized film having a <10mum thickness on the surface of the base material consisting essentially of an Al-Si alloy which contains 1 to 3wt.% Si. Particularly, the separated Si is controlled so that more than 80wt.% of the separated Si particles have >=0.05mum particle diameter, and the total Si content (Awt.%) and the amount of the residual Si in the solid solution (Bwt.% on the same base as above) can meet the relational expressions: B<=A-0.5 when A<1.5 and B<=1 when A>=1.5.

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 particularly relates to a far infrared radiator having an anodic oxide film formed by using an aluminum alloy as a base material and a manufacturing method thereof. .

[0002]

2. Description of the Related Art Generally, in heaters utilizing far infrared rays, the far infrared ray emissivity of the radiator is high and 10
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 the 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. 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.

However, the conventional far-infrared radiator having an anodized film formed on the surface of an aluminum substrate is 20
When it is used at a high temperature of 0 ° C. or higher, the anodic oxide film is apt to crack due to thermal shock, which causes instability of emissivity and deterioration of corrosion resistance. Further, the conventional far-infrared radiator having an anodized film formed on the surface of an aluminum substrate has a drawback that the emissivity is low in the wavelength range of 3 to 7 μm, and therefore, when trying to obtain a higher radiation amount as a whole. Had to form a thick anodic oxide film, but in that case, there was a problem that cracks due to thermal shock were more likely to occur.

Therefore, the present inventors have already disclosed in Japanese Patent Laid-Open No. 4-11.
No. 0493, containing 0.3 to 4.3% of Mn,
A far-infrared radiation member is proposed, in which an aluminum alloy having an intermetallic compound of Mn and Al finely and uniformly dispersed and deposited is used as a base material, and an anodized film is formed on the surface of the aluminum alloy material, preferably with a thickness of about 10 μm or more. is doing.
The far-infrared radiation member usually has a black anodic oxide film.

It has been confirmed that the radiating member proposed above does not easily cause cracks in the anodic oxide film even at a high temperature of 200 ° C. or higher, and exhibits considerably excellent radiating characteristics even in the wavelength range of 3 to 7 μm. .

[0009]

Recently, various applications utilizing the radiation characteristics of far-infrared rays have been expanded, and it has been found that the above-mentioned proposed radiator may not always be satisfactory.

That is, depending on the application of the far-infrared radiation member, it is often desired to use not only a rolled material but also an aluminum alloy base material made of a cast material or an extruded material. As the alloy base material, the rolled material is most suitable because it is necessary to finely and uniformly deposit the Al-Mn-based intermetallic compound, and in reality, it is difficult to apply it to the cast material, the extruded material, and the forged material. is there.

Further, as described above, the far-infrared radiation member intended to be used at a high temperature of 200 ° C. or higher is generally used in a portion which is not so much visible to the eyes or is not so conspicuous even if it is exposed to the eyes. Since it was mostly done, the aesthetic point such as the color tone of the film has not been so much a problem in the past, and therefore the black color tone of the anodic oxide film as described above is aesthetically significant. However, a black color tone was considered to be advantageous from the viewpoint of far infrared radiation characteristics.

However, recently, as the use of far-infrared radiation members such as heating food in homes or indoor heating expands, the color tone of the radiation member is desired to be in harmony with the surrounding color tone. Or, when a stain is attached, a color tone that makes it easy to discriminate the stain is desired, and there is a problem that a radiating member having a black color tone like the above proposal cannot satisfy these requirements. It has started to occur.

Further, recently, in order to reduce the cost of the process mainly for forming an anodized film, it has been desired to make the anodized film as thin as possible, and the anodized film is hard and brittle. If the thickness of the anodized film is large, the film may be easily cracked during various processes such as drilling, and a thin foil (usually having a thickness of 0.
4mm), the anodic oxide film is 10μ
If the thickness is more than about m, the toughness of the foil becomes low and the foil tends to tear easily. From these viewpoints, it is desired that the anodic oxide film be thin, and the anode thinner than about 10 μm is desired. A radiating member based on an aluminum alloy that satisfies the sufficient radiating properties even with an oxide film is desired, but the radiating member proposed above is not always sufficient in this respect.

The present invention has been made in view of the above circumstances. Not only does the anodized film hardly crack even at a high temperature of 200 ° C. or more and the far-infrared radiation characteristics are excellent even in the wavelength range of 3 to 7 μm, It has a color tone that is easy to match with the color tone of the surroundings and is easy to distinguish the adhesion of stains from the viewpoint of hygiene, and also facilitates the production of the base material by various methods such as casting, extrusion, and forging. It is an object of the present invention to provide a far-infrared emitting member having an aluminum alloy as a base material, which can obtain good far-infrared emitting characteristics even with a thin anodic oxide film.

[0015]

The inventors of the present invention have already disclosed in Japanese Patent Application No. 4-141084 that a black anodic oxide film having a thickness of 10 μm or more is formed by using an Al-1 to 3% Si alloy as a base material. The formed far-infrared radiation member is proposed. In the case of the proposed radiating member, cracks are unlikely to occur in the anodized film even at a high temperature of 200 ° C. or higher, and the radiation characteristics are excellent even in the wavelength range of 3 to 7 μm. It has the advantage that it can be easily applied to materials and the like. Therefore, further experiments on the proposed radiation member
As a result of further study and earnest experiments and studies to solve the above problems, the above-mentioned Japanese Patent Application No. 4-14
When the aluminum alloy used in the radiating member proposed in No. 1084 is used as a base material, even a thin anodic oxide film having a thickness of less than 10 μm can exhibit far-infrared radiation characteristics that are considerably excellent, and anodic oxidation is also possible. Film thickness 10 μm
If it is less than the above, as a surface color tone, it is easy to harmonize with the surrounding color tone and it is easy to determine the adhesion of stains, and a relatively light gray to white color tone can be obtained, and thus it is possible to solve all the above-mentioned problems. The invention was made.

That is, the present inventors set the aluminum alloy of the base material as a component system containing 1% or more and less than 3% of Si, and appropriately adjust the dispersion state of the metal Si particles on the surface of the base material. Further, they have found that the above-mentioned problems can be solved by setting the thickness of the anodized film formed on the surface to less than 10 μm, 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 in an amount of 1 wt% or more and less than 3 wt%, with the balance being Al and inevitable impurities. Is characterized in that a gray anodic oxide film having a film thickness of less than 10 μm is formed on the surface thereof.

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
It is characterized in that an alloy containing at least one kind and having the balance of Al and unavoidable impurities is used as a base material, and a gray anodic oxide film having a film thickness of less than 10 μm is formed on the surface of the base material. .

Further, the far-infrared radiator according to a third aspect of the present invention is used as the base material in the far-infrared radiator according to the first or second aspect, and the total number of precipitated 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.

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 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 less than 10 μm 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.

[0021]

The far-infrared radiator of the present invention is basically 1 wt.
% -Less than 3 wt% of Si is used as a base material, and a gray anodic oxide film having a thickness of less than 10 μm is formed on the surface of the base material.

As described above, in the aluminum alloy containing 1 wt% or more and less than 3 wt% of Si, the metal Si particles are dispersed and precipitated in the structure by an appropriate heat treatment as 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. Furthermore, in the process of growing the anodized film (porous layer) during the anodizing treatment, the pores grow while avoiding the metallic Si particles, so the pores in the film have a branched structure, and such branching occurs. The pore structure improves the scattering and absorption of incident light in the anodic oxide film, and further improves the radiation characteristics of far infrared rays. Since far-infrared radiation characteristics are remarkably improved in this way, it is possible to exhibit good far-infrared radiation performance that is practically unproblematic even with a relatively thin anodic oxide film of less than 10 μm.

Further, as described above, since the thickness of the anodized film is relatively thin, less than 10 μm, the color tone of the appearance of the film is also
The color is light gray to near white rather than black. Also, since the hard anodic oxide film is thin, there is little risk of cracks in the film even when mechanical processing such as drilling is performed, and even when made into a thin foil, the toughness of the foil is low and it is easy to tear. Is prevented.

Further, 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,
As a result, cracks are less likely to occur due to thermal shock,
Even if a crack occurs, its 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 an alloy component which is basically important 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 forming the pores in the film into a branched structure 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. When the Si content of the base aluminum alloy is less than 1 wt%, the volume ratio of the metal Si particles in the anodized film is small and the far infrared radiation characteristics are insufficient. On the other hand, if 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 elements of the aluminum alloy of 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 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 with each other 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 to the improvement of strength, refinement of crystal grains, and 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 Mn is added
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 amount is less than 0.05% by weight, the effect cannot be obtained. On the other hand, if the amount is more than 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 single addition amount of these elements is 0.3 wt.
If it exceeds 0.1%, the plastic workability is lowered 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 adding Ti is 0.005-0.2 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 when scrap is used as the 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 texture state of the base aluminum alloy of the far-infrared radiator of the present invention, particularly the dispersed state of metal Si particles will be described.

As described above, in an aluminum alloy of a system containing 1 wt% or more and less than 3 wt% Si, Si forms a solid solution 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 deposited 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, and the radiation characteristic of far infrared rays is improved. Furthermore, in the process of growing pores during anodizing treatment, the pores grow while avoiding 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, so that 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 amount of deposition 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. If the diameter of the precipitated Si particles is less than 0.05 μm, the far infrared absorption and absorption are insufficient, and good radiation characteristics cannot be obtained. 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 place 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 residual solid solution Si amount depends on the total Si amount, the precipitated Si amount becomes approximately 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 approximately 1.5 wt% or more, and the Si content of 1.5 wt% is added as a 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 investigating the relationship between the residual solid solution Si amount and the total Si content in this manner, 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 are insufficient.

In order to obtain the above-mentioned precipitation state of the precipitated Si particles, it is necessary to perform the precipitation treatment after the 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 carrying out hot working and / or cold working such as cold rolling. However, precipitation treatment is performed at a stage after casting in the manufacturing process of the base material, or hot working and / or post casting is 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 the 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 performed independently or may be performed 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 anodic oxidation treatment applied to the aluminum alloy substrate will be described.

By subjecting the aluminum alloy substrate having the above-mentioned chemical composition and metal structure to anodizing treatment, an anodized film exhibiting excellent far-infrared radiation characteristics can be obtained. 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. Furthermore, metallic Si that is present in the anodized film as it is
The particles and the fine pores that are branched as described above scatter and absorb the incident light, and as a result, the far infrared radiation characteristics are improved. And again, the above-mentioned branched fine pore structure and metal S in the film
The i-particles function as a relaxation point for thermal stress, so that cracks are less likely to occur in the film, and the film can be used without cracking up to a high temperature of about 500 ° C.

Here, the film thickness of the anodized film is set to less than 10 μm. That is, in order to obtain a light gray color tone that is in harmony with various usage environments, it is necessary that the film thickness be less than 10 μm. Cracking is less likely to occur, and sufficient toughness can be secured even when used as a thin foil. Even if the film thickness is less than 10 μm, stable far-infrared radiation characteristics in a wide wavelength range can be obtained by using the above-described aluminum alloy as the base material. Here, the gray color of the anodic oxide film may be any color that normally exhibits a Marcel value of more than 4.5.

The conditions of the anodic oxidation treatment are not particularly limited, and an inorganic acid such as sulfuric acid and 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-current / direct-current combination, alternating-current / direct current superimposed waveform, or the like. 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.

[0051]

【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 x 200 mm x 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 at electrolysis temperature 20 ℃, film thickness 7μ
m anodized film was formed.

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 characteristics of the 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 investigated. 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 exceeds 4.5, it can be determined that the Munsell lightness has a color tone close to gray to white in harmony with the use environment. Wavelength 6 μm
When the spectral emissivity in 1 is 0.7 or more, it can be determined that the far-infrared radiation characteristic is good.

[0054]

[Table 1]

[0055]

[Table 2]

In Example 1, alloy Nos. 1 and 40
In the 0 ° C. heating material, the conditions regarding Si satisfy the condition range specified in the present invention, and all of these have Munsell brightness and spectral emissivity satisfying predetermined values, that is, the visual color tone is close to gray to white. And the far infrared radiation characteristics are excellent. In addition, these 400 ° C. heating materials of Alloy Nos. 1 and 2 are 5 after the anodizing treatment.
No crack was observed when the surface was visually observed after heating to 00 ° C.

However, the as-cast materials of Alloy Nos. 1 and 2 and the alloys of No. 3 each had a large number of cracks visually when the surface was observed after heating to 500 ° C. after anodizing. It was Alloy numbers 1, 2, 3
As long as the 150 ° C heating material is observed with an optical microscope,
No precipitated Si was found in the dendrite portion. Then, when this portion was observed with an electron microscope, it was 0.01 to 0.03 μm or 0.01 to 0.0
The presence of fine precipitated Si particles of 2 μm was observed. Even if these fine deposited Si particles are deposited, they do not act as absorption points for far infrared rays, and therefore far infrared radiation characteristics are not improved.

Example 2 Regarding 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) in 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 Alloys having compositional compositions shown by alloy numbers 5 and 6 in Table 1 were heated 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 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 Example 3, the final annealing after cold rolling also serves as a precipitation treatment. Therefore, when the material of Alloy No. 5 within the composition range of the composition of the present invention is used, the final annealing is appropriate. A Si precipitation state was obtained. With the material of Alloy No. 5, no crack was observed even when the surface was visually observed after heating to 500 ° C. after the anodizing treatment. On the other hand, the material of Alloy No. 6 is disclosed in JP-A-4-1-1.
This is a comparative material using an Al-Mn-based alloy disclosed in No. 10493. In this case as well, no crack was observed after heating to 500 ° C, but an appropriate Si precipitation state was obtained because the Si content was small. I couldn't do it. Further, regarding the materials of alloy numbers 5 and 6 according to this Example 3, 2.5
The spectral emissivity curve at a wavelength of ~ 25 μm is shown in FIG. As is clear from FIG. 3, no decrease in emissivity was observed in the wavelength range of 7 μm or less with any of the alloys Nos. 5 and 6, but the alloy No. 5 generally had the alloy No. 6
It was confirmed that the emissivity was higher than that of the material. Figure 3
In addition, a spectral emissivity curve of 2.5 to 25 μm for a comparative material using the pure Al-based alloy of Alloy No. 3 in Example 1 described above (however, as-cast material) is also shown. In the case of this comparative material, it is found that not only the emissivity is generally low, but also the emissivity is drastically decreased particularly in the wavelength range of 6.5 μm or less.

From the above examples, if the alloys within the composition range defined in the present invention satisfy the above Si precipitation conditions, even if the thickness of the anodic oxide film is less than 10 μm, Shows excellent far infrared radiation characteristics,
Moreover, even if the anodic oxide film is heated to 500 ° C., cracks do not occur, and by setting the thickness of the anodic oxide film to less than 10 μm, it is possible to obtain a color tone close to gray to white in harmony with various usage environments. it is obvious. And again, by any manufacturing means such as casting, forging, rolling, extrusion,
It is also clear that it is possible to produce materials with excellent far infrared radiation properties.

[0064]

INDUSTRIAL APPLICABILITY The far-infrared radiator of the present invention has good far-infrared radiation characteristics despite the fact that the anodized film has a relatively small thickness of less than 10 μm. It was said that the oxide film was inferior 3 ~
It has excellent radiation characteristics in the wavelength range of 7 μm, and cracks due to thermal strain do not occur in the anodic oxide film up to a high temperature of about 500 ° C. Therefore, it has good heat resistance and long temperature at a temperature of up to about 500 ° C. It is effective as an infrared radiator, and since the surface color tone is close to gray to white, it can be harmonized with the surrounding color tone in various usage environments, and stains can be easily distinguished. It is also suitable for applications requiring hygiene such as food heating, and because the thickness of the anodized film is small, there is less risk of the film cracking during drilling and other processing, and the cost required for anodizing treatment. Is also reduced. Further, the far-infrared radiator of the present invention can be manufactured by any manufacturing means such as casting, forging, rolling, extrusion, etc. Therefore, a far-infrared radiator having an arbitrary shape can be obtained according to the application and the place of use. Besides, it is possible to easily obtain a radiator having a complicated shape. 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.

3 is a graph showing a spectral emissivity curve for each material of alloy numbers 5 and 6 of Example 3 and an as-cast material of alloy number 3 of Example 1. FIG.

Front page continuation (72) Inventor Masakazu Maejima 1-5-1 Kiba, Koto-ku, Tokyo Inside Fujikura Ltd.

Claims (4)

[Claims] 1. A base material is an alloy containing Si of 1 wt% or more and less than 3 wt%, the balance being Al and inevitable impurities, and a gray anodic oxide film having a thickness of less than 10 μm 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.
An alloy containing 5 wt% or 0.005 to 0.2 wt% of Ti 0.005 to 0.2 wt% and the balance of Al and inevitable impurities is used as a base material, and the film thickness is 10 μm on the surface of the base material.
A far-infrared radiator having a gray anodic oxide coating of less than m. 3. Of the total precipitated Si particles in the base material, 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 of less than 0 μm, 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 content is less than 1.0, 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% or less.
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.