JP5789401B2 - Aluminum fin material for heat exchanger - Google Patents

Description

  The present invention relates to an aluminum fin material made of aluminum or an aluminum alloy having a film formed on the surface thereof, and more particularly to an aluminum fin material for a heat exchanger that is preferably used in a heat exchanger such as an air conditioner.

  Heat exchangers are used in various fields such as room air conditioners, packaged air conditioners, refrigeration showcases, refrigerators, oil coolers, and radiators. In heat exchangers such as room air conditioners and packaged air conditioners, an aluminum material or an aluminum alloy material is used as the fin material because of its excellent thermal conductivity and workability.

  Heat exchangers provided for air conditioners and the like include an indoor unit for exchanging heat indoors and an outdoor unit for exchanging the heat with outdoor air. The environment where heat exchangers such as air conditioners are installed includes high humidity environments for outdoor units, salt damage environments in coastal areas, acidic environments due to acid rain, high humidity environments for indoor units, special facilities, etc. There are various corrosion-promoting environments, and by installing a heat exchanger in these environments, the corrosion of the fin material is likely to proceed, the failure and deterioration of the heat exchanger are promoted, and the cause of unpleasant odor due to corrosion of the aluminum plate Had the problem of becoming.

  Therefore, as a method of imparting corrosion resistance to the air conditioner fin material, a corrosion resistant film is provided on the surface of the fin material. For example, a chromate film, a non-chromate film made of titanium or zirconium compound, a boehmite film and an inorganic film such as water glass are formed on the surface of aluminum or aluminum alloy thin plate, or an organic coating agent such as acrylic resin is roll-coated. Came to be formed.

  However, in inorganic films such as boehmite film and chromate film, the water condensed on the aluminum fins of the heat exchanger becomes coarse water droplets and stays on the fin surface. The result is that the ventilation efficiency is increased and the thermal efficiency is greatly reduced.

  In the case of an organic film, if a film is coated with a roll coater or a bar coater, many film defects such as coating omission occur on the film surface. Therefore, there is a disadvantage that the desired corrosion resistance cannot be obtained unless the film thickness is increased. However, increasing the film thickness tends to cause film cracking and peeling during molding, and also causes a decrease in thermal conductivity. Furthermore, since it takes time for baking and drying, it becomes an obstacle to improvement in productivity, and since the amount of paint used is large, the cost is increased and the amount of VOC (Volatile Organic Compounds) generated during baking and drying is also large.

  As means for solving such a problem, for example, a method disclosed in Patent Document 1 has been proposed. That is, a method has been proposed in which an extremely thin and uniform electrodeposition film is formed on an aluminum plate by an electrodeposition coating method, thereby solving the problems of corrosion resistance degradation due to film defects and film cracking during processing.

Japanese Patent Publication No. 05-041718

However, the conventional aluminum fin material has the following problems.
The method for producing a pre-coated fin material having an electrodeposition film proposed in Patent Document 1 is inferior in productivity because it cannot be produced in large quantities and continuously like a roll coater, and it is difficult to meet the recent increase in demand. It is.

  Therefore, by forming a thin corrosion-resistant film on the surface of an aluminum alloy plate by roll coating or bar coating, corrosion resistance, productivity, thermal conductivity, reduced VOC generation, and workability during fin forming after film formation There is a need to provide excellent aluminum precoat fin materials.

In the case of organic coatings, coating with a roll coater or bar coater with a coating amount of 1200 mg / m ² or less results in coating defects due to the influence of the surface condition of the material because the coating amount on the aluminum plate is very small. And film unevenness are likely to occur. The coating material has a correlation that the area ratio of pitting corrosion increases as the number and area of coating defects increase, and it is considered that corrosion progresses mainly starting from the coating defects. In addition, when the film is applied, even a small amount of film unevenness generates a film thickness several times thinner than the average film thickness. For this reason, it is considered that water permeability of the film is likely to occur even in the thin part of the film and is easily corroded. As described above, when a corrosion-resistant resin is coated with a roll coater, there is a problem that a film defect or film unevenness occurs and the corrosion resistance deteriorates.

The present invention has been made in view of the above-mentioned problems, and performs film coating with a film amount of 1200 mg / m ² or less by roll coating or bar coating, and is excellent in thermal conductivity, productivity, workability and reduction of paint usage. An object of the present invention is to provide an aluminum fin material for a heat exchanger with good corrosion resistance, in which the generation amount of film defects is suppressed and pitting corrosion hardly occurs.

That is, the aluminum fin material for a heat exchanger according to the present invention is an aluminum fin material for a heat exchanger comprising an aluminum plate and a corrosion-resistant film formed on a surface of the aluminum plate by a roll coater or a bar coater, and the aluminum plate Fe: 0.05 to 0.4 mass%, Cu: 0.04 mass% or less (including 0 mass%), Ti: 0.01 mass% or more and 0.08 mass% or less , Si: 0.15 The corrosion resistance coating comprising : mass% or less (including 0 mass%), the balance being Al and inevitable impurities, the number density of intermetallic compounds having a maximum length of 3 μm or more on the surface thereof is 2766 / mm ² or less. is a main component thereof coating weight consists corrosion resistance resin comprises at least one urethane resin and epoxy resin is be 100 to 800 mg / ^{m 2} Wherein the coating defect number density is 300 pieces / mm ² or less.

According to such a structure, an aluminum plate contains 0.05% or more of Fe, whereby the strength is improved by solid solution strengthening. Further, the sub-crystal grains are refined, the elongation is improved, and β-Fiber is sufficiently generated. Moreover, the pinning effect can be anticipated by containing Fe, and crystal grain coarsening is suppressed, and color cracking can be suppressed. On the other hand, when the aluminum plate contains 0.4% or less of Fe, the number density of intermetallic compounds is suppressed, which contributes to the reduction of film defects. When the aluminum plate contains Cu: 0.04% by mass or less, the self-corrosion resistance of the aluminum plate is improved, and even if water reaches the Al base, it hardly corrodes. When the aluminum plate contains Ti: 0.08% by mass or less, the crystal grains are refined and the color cracking resistance is improved. When the aluminum plate contains Si: 0.15% by mass or less, the number density of intermetallic compounds is further suppressed, which contributes to the reduction of film defects. Moreover, when the coating amount of the corrosion-resistant resin film whose main component is at least one of urethane resin and epoxy resin is 800 mg / m ² or less, the thermal resistance of the film is reduced, which contributes to the improvement of thermal conductivity. . And since the number density of the film | membrane defect of a corrosion-resistant film | membrane is 300 pieces / mm < ² > or less, since the origin of corrosion is few, even if there are few film | membrane amounts, corrosion resistance is favorable.
In the present invention, the film defect means a part having a film amount of 80 mg / m ² or less, and does not mean only a part where the film is missing and the Al substrate is exposed.

Further, in the aluminum fin material for heat exchanger, the number density of intermetallic compounds having a maximum length of 3 μm or more on the aluminum plate surface is preferably 2500 pieces / mm ² or less.

  According to such a configuration, the number of film defects can be reduced regardless of the film thickness by suppressing the number density of intermetallic compounds having a maximum length of 3 μm or more to a predetermined amount or less by lowering the soaking temperature. .

  Furthermore, the aluminum fin material for heat exchanger further includes a base treatment film between the aluminum plate and the corrosion-resistant film, and the base treatment film is made of an inorganic oxide or an organic-inorganic composite compound and has a thickness of 1 nm to 100 nm. Is preferred.

  According to such a configuration, the corrosion resistance of the aluminum fin material for heat exchangers is further improved, and the adhesion of the corrosion resistant film is also improved.

In addition, the aluminum fin material of the present invention further includes a hydrophilic resin film on the corrosion-resistant film, and the hydrophilic resin film contains a hydrophilic resin, and the film amount is 50 to 10,000 mg / m ² . It is preferable.

  With such a configuration, it is possible to prevent the water condensed on the fins from becoming large water droplets, so that the heat efficiency of the heat exchanger using the aluminum fin material for heat exchanger of the present invention can be improved.

The aluminum fin material for heat exchangers according to the present invention can maintain good corrosion resistance to the environment even with a coating amount of 1200 mg / m ² or less. Thereby, the heat exchange efficiency as a fin can be improved, preventing deterioration of the aluminum fin material for heat exchangers. Furthermore, since the corrosion-resistant film is easily cured during the production of the fin material, the baking / drying time is shortened and the furnace temperature is lowered, thereby contributing to the improvement of productivity. In addition, the film peeling during processing is reduced, the load on the processing jig is reduced, and the amount of paint used is reduced, so that there is an effect of reducing VOC.

It is a schematic diagram of the cross section of the aluminum fin material for heat exchangers which concerns on this invention. It is a drawing substitute photograph of the mapping image of EPMA. It is a schematic diagram at the time of thermal conductivity measurement of a heat exchanger. It is sectional drawing of the XX line of FIG.

  Next, an embodiment of an aluminum fin material for a heat exchanger according to the present invention (hereinafter, appropriately referred to as a fin material) will be described in detail with reference to the drawings as appropriate.

<Fin material>
As shown in FIGS. 1A to 1D, the fin material according to the present invention includes an aluminum plate (1) and a corrosion-resistant film (3) formed on the surface of the aluminum plate (1) by a roll coater or a bar coater. The aluminum plate (1) contains a predetermined amount of Fe, and the balance is made of Al and inevitable impurities. Then, the fin material according to the present invention, on an aluminum plate (1), a coating amount 100~1200mg / ^{m 2,} requires a corrosion barrier coating (3) coating defects number density is 300 pieces / mm ² or less. It is preferable that a base treatment film (such as a phosphate chromate treatment film) (2) or a hydrophilic resin film (4) is formed on the aluminum plate (1). Further, it is preferable that the number density of intermetallic compounds in the aluminum plate is specified to 2500 pieces / mm ² or less. Preferably, Si, Cu, and Ti are suppressed to a predetermined amount or less.
Each configuration will be described below.

(Aluminum plate)
The metal plate used in the present invention is a plate material made of aluminum or an aluminum alloy, and is excellent in thermal conductivity and workability. Therefore, an alloy type 1000 series aluminum and aluminum alloy specified in JIS H4000 are preferably used. . In this invention, the aluminum prescribed | regulated to the following raw material component is used.
The reason for limiting the component numerical values will be described below.

(Fe: 0.05 to 0.4 mass%)
Fe is an element added to improve strength by solid solution strengthening, improve corrosion resistance, and improve elongation by refinement of subgrains. If the Fe content is less than 0.05% by mass, those effects cannot be obtained. Moreover, the pinning effect by Fe cannot be expected, leading to coarsening of crystal grains and causing color cracking. Furthermore, when the Fe content is less than 0.05% by mass, there are other factors such as poor productivity because of the need for washing in the factory, and the high price of Al bullion, which is not economical. On the other hand, when the Fe content exceeds 0.4% by mass, the intermetallic compound becomes coarse, which causes the occurrence of film defects in the corrosion resistant film and leads to deterioration of the corrosion resistance. Therefore, the Fe content is 0.05 to 0.4 mass%.

(Si: 0.15 mass% or less (including 0 mass%))
Si is an element mixed as an unavoidable impurity. However, if the Si content exceeds 0.15% by mass, the intermetallic compound becomes coarse, which causes the occurrence of film defects in the corrosion-resistant film and leads to deterioration of the corrosion resistance. Therefore, the Si content is 0.15% by mass or less. In addition, you may suppress to 0 mass%.

(Cu: 0.04 mass% or less (including 0 mass%)
Cu is an element to be added in a small amount in order to sufficiently improve the strength by solid solution strengthening, improve the elongation by refinement of subgrains, and sufficiently generate β-Fiber. When Cu content exceeds 0.04 mass%, the self-corrosion resistance of a raw material will fall. Therefore, the Cu content is 0.04% by mass or less. In addition, you may suppress to 0 mass%.

(Ti: 0.01-0.08 mass%)
Ti is an element to be added in a trace amount in order to refine the ingot structure. You may add as an Al-Ti-B intermediate alloy. That is, an Al-Ti-B ingot refining agent having a ratio of Ti: B = 5: 1 or 5: 0.2 is melted in the form of a waffle or a rod (melting furnace, inclusion filter before slab solidification). The degassing device and the molten metal flow rate control device may be added to the molten metal at any stage). The Al—Ti—B intermediate alloy is allowed to contain up to 0.08% by mass in terms of Ti. If the Ti content is less than 0.01% by mass, the effect of refining the ingot structure cannot be obtained. On the other hand, when the Ti content exceeds 0.08% by mass, the intermetallic compound becomes coarse, which causes the occurrence of film defects in the corrosion-resistant layer and leads to deterioration of the corrosion resistance. Therefore, when adding Ti, Ti content shall be 0.01-0.08 mass%.

(Balance: Al and inevitable impurities)
In addition to the above components, the aluminum plate is composed of Al and inevitable impurities. In addition to the above-described Si, for example, Mn, Cr, Mg, Zn, Ga, V, Ni, etc. within the normally known range, which are included in the metal and the intermediate alloy, are inevitable impurities. Inclusion of up to 0.02% by mass is permitted.

(Intermetallic compound)
The number density of intermetallic compounds having a maximum length of 3 μm or more on the surface of the aluminum plate (1) of the present invention is preferably 2500 / mm ² or less.
When the number density of the intermetallic compound in the aluminum plate exceeds 2500 / mm ² , it causes a film defect of the corrosion resistant film, leading to deterioration of the corrosion resistance of the fin material.
The number density of intermetallic compounds having a maximum length of 3 μm or more can be controlled by the content of each component contained in the aluminum plate (1) and the homogenization heat treatment conditions (temperature and time).
In addition, the number density of the intermetallic compound is measured by SEM.

(Thickness 0.08-0.3mm)
In consideration of strength, thermal conductivity, workability, and the like, the aluminum plate preferably has a thickness of about 0.08 to 0.3 mm.

(Corrosion resistant coating)
The corrosion-resistant film (3) is formed of a corrosion-resistant resin made of at least one of a urethane resin, an epoxy resin, a polyethylene resin, and an acrylic resin. The corrosion-resistant resin is mainly composed of a urethane resin, an epoxy resin, an acrylic resin, or a polyethylene resin, and a modified resin such as a polyester-based urethane resin, a modified epoxy resin, an acrylic / styrene copolymer resin, or a urethane-modified polyethylene resin, Also includes a copolymer resin. Thereby, corrosion (oxidation) of the aluminum plate is suppressed, and corrosion resistance is imparted to the fin material. For example, even in a harsh and humid environment such as an acidic atmosphere, it is possible to suppress the condensed water that has permeated through another film such as a hydrophilic resin film from coming into contact with the aluminum plate (1). The formation of the corrosion-resistant film (3) is performed, for example, by applying and baking an aqueous solution of a hydrophobic resin by bar coating or roll coating.

In a general heat exchanger, a copper tube is often used as a heat transfer tube formed through a fin material. If the amount of the corrosion-resistant coating (3) is large, the contact thermal resistance between the fin material and the copper tube by the corrosion-resistant coating (3) increases, and the heat transfer performance may be reduced. However, if the coating amount is as small as 1200 mg / m ² or less, excellent thermal conductivity can be exhibited. Moreover, in the case of a coating amount of less than 100 mg / m ² , the coating is very thin and easily penetrates water, and a large amount of coating unevenness and coating defects occur regardless of the surface state of the material such as the fin material. Because it occurs, the starting point of corrosion increases. For these reasons, a coating amount of less than 100 mg / m ² cannot be applied because the corrosion resistance is significantly deteriorated. Thus coating amount shall be as 100mg ^{/ m 2} ~1200mg ^/ m 2 of the. More preferably from 200 to 1000 mg / ^{m 2.} More preferably from 250~800mg / ^{m 2.}

The corrosion-resistant film (3) has a defect number density of 300 / mm ² or less. The number density of film defects is controlled by the amount of the corrosion-resistant resin and the number of intermetallic compounds on the surface of the material. The film defect number density is measured by SEM as described later.
A plurality of coatings may be present, and it is desirable that the hydrophilic resin coating (4) is formed on the outermost surface (FIGS. 1 (c) and (d)).
Further, it is desirable to form a plurality of corrosion resistant films (3) in consideration of the desired corrosion resistance of the fin material and the performance of the coating resin used.
The amount of film is measured by fluorescent X-ray, infrared film thickness meter, weight measurement by film peeling, EPMA (Electron Probe Microanalyzer) or the like.

(Undercoat film)
A base treatment film (2) may be formed between the aluminum plate (1) and the corrosion-resistant film (3). The base treatment film (2) is made of an inorganic oxide or an organic-inorganic composite compound. The inorganic oxide preferably contains chromium (Cr) or zirconium (Zr) as a main component, and is formed by, for example, phosphoric acid chromate treatment, zirconium phosphate treatment, or chromate chromate treatment. . However, in the present invention, the base treatment film (2) can be formed by performing, for example, zinc phosphate treatment or phosphate titanate treatment as long as it exhibits corrosion resistance. . The organic-inorganic composite compound is formed by performing a coating type chromate treatment or a coating type zirconium treatment, and examples thereof include an acryl-zirconium composite.

  Corrosion resistance is imparted to the fin material by the formation of the base treatment film (2). Further, when forming the corrosion-resistant film (3), when the corrosion-resistant film (3) is present on the base treatment film (2), rather than when the corrosion-resistant film (3) is directly present on the aluminum plate. This improves the adhesion of the corrosion-resistant film (3) to the aluminum plate (1). Thereby, the adhesiveness of the corrosion-resistant film (3) at the time of processing a precoat fin material can be improved. Further, the corrosion of the fin material due to the installation environment such as an air conditioner can be further suppressed.

The base treatment film (2) preferably contains Cr or Zr in a range of 1 mg to 100 mg / m ² in terms of Cr or Zr. The thickness of the base treatment film (2) is preferably 1 nm to 100 nm. Needless to say, the film thickness of the base treatment film can be appropriately changed in accordance with the purpose of use. If the film thickness of the base treatment film (2) is less than 1 nm, the corrosion resistance of the fin material tends to be lowered. If the film thickness exceeds 100 nm, the adhesion between the base treatment film (2) and the corrosion resistance film (3). Tends to decrease. From the economical viewpoint, the film thickness is preferably 100 nm or less.

(Hydrophilic resin film)
A hydrophilic resin film (4) may be formed on the surface of the corrosion-resistant film (3). Thereby, hydrophilicity can be imparted to the fin material. As a result, the condensed water becomes coarse water droplets and stays on the fin surface, so that the ventilation resistance is not increased and the heat efficiency of the heat exchanger is not significantly reduced.

  The hydrophilic resin film (4) is mainly composed of a hydrophilic resin. The hydrophilic resin to be used is preferably an organic compound having a hydrophilic functional group or a derivative of the organic compound having the hydrophilic functional group. Examples of the hydrophilic functional group include a sulfone group, a sulfone group derivative, a carboxyl group, a carboxyl group derivative, a hydroxyl group, and a hydroxyl group derivative. An organic compound having a hydrophilic functional group, a derivative of the organic compound having a hydrophilic functional group is a polymer (polymer) or copolymer of a monomer having a hydrophilic functional group, or a polymer having the hydrophilic functional group. A blend of these. For example, examples of the polymer having a carboxyl group include polyacrylic acid, and examples of the polymer having a hydroxyl group include polyvinyl alcohol and polyalkylene glycol.

  The hydrophilic resin film (4) is preferably a resin or substance that does not contain a nitrogen compound such as an acrylamide resin. In addition, the content in the case of containing a nitrogen compound is preferably 1 atom% or less in nitrogen content ratio measurement by GD-OES (glow emission spectroscopic analysis). If the nitrogen compound is contained in an amount exceeding 1 atomic%, the nitrogen compound is oxidized in a severe environment such as an acidic environment or a high humidity environment, and an odor is likely to be generated.

The coating amount of the hydrophilic coating (4) is 50 to 10,000 mg / m ² . When the coating amount is less than 50 mg / m ² , the hydrophilicity of the fin material tends to be lowered. On the other hand, when the coating amount exceeds 10,000 mg / m ² , no further improvement in hydrophilicity is observed. At the same time, it is not economically preferable that the coating amount exceeds 10,000 mg / m ² . Particularly preferably, the coating amount is 150 to 2000 mg / m ² . By such a coating amount, the hydrophilicity of the fin material is further enhanced without impairing the economy. The coating amount is measured by fluorescent X-ray, infrared film thickness meter, weight measurement by coating peeling, or the like.

(Yield strength: 130 N / mm ² or more)
Since the fin material (10) of the present invention performs drawless press molding or combination press molding in fin production, the proof stress is preferably 130 N / mm ² or more. When the proof stress is less than 130 N / mm ² , the strength is insufficient, and a large number of color cracks occur during drawless press and combination press molding. Therefore, the proof stress is preferably 130 N / mm ² or more. In addition, Preferably it is more than 130 N / mm < ² >. Further, if the strength is too high, color cracks are liable to occur during drawless press molding, so the upper limit is preferably set to 170 N / mm ² .

≪Method for manufacturing fin material≫
The manufacturing method of a fin material (10) includes an aluminum plate manufacturing process and a surface treatment process.

(Aluminum plate manufacturing process)
The aluminum plate (1) according to the fin material for an aluminum heat exchanger is manufactured by an ingot production process, a heat treatment process, a hot rolling process, a cold working process, and a temper annealing process.
Hereinafter, each step will be described.

(Ingot production process)
The ingot production step is a step of producing an aluminum alloy ingot by melting and casting an aluminum alloy.
In the ingot production step, an ingot having a predetermined shape is produced from a molten metal in which an aluminum alloy having the above composition is melted. The method for melting and casting the aluminum alloy is not particularly limited, and a conventionally known method may be used. For example, it can be melted using a vacuum induction furnace and cast using a continuous casting method or a semi-continuous casting method.

(Heat treatment process)
The heat treatment step is a step of subjecting the aluminum alloy ingot having the above chemical components to a heat treatment (homogenization heat treatment) at a temperature of 450 ° C. to 560 ° C. for 1 hour to 10 hours.
If the heat treatment temperature is less than 450 ° C., the ingot structure is not sufficiently homogenized. In addition, the hot workability is reduced. On the other hand, when the heat treatment temperature exceeds 560 ° C., the fine intermetallic compound that is refined during heating becomes coarse, the sub-crystal grains become coarse, and the elongation decreases. In addition, the amount of solid solution increases. Therefore, the heat treatment temperature is set to 450 ° C to 560 ° C. Preferably, it is 480 degreeC-540 degreeC. Moreover, it is normal to perform heat processing for 1 hour or more, and since the effect will be saturated if it exceeds 10 hours, heat processing time shall be 1 hour-10 hours.

(Hot rolling process)
The hot rolling step is a step of performing hot rolling after the heat treatment under the condition that the finish temperature of hot finish rolling is 250 ° C. or higher and lower than 300 ° C.
When the finish temperature of hot finish rolling is less than 250 ° C., the rollability of the material is lowered, and the rolling itself becomes difficult or the thickness control becomes difficult, and the productivity is lowered. On the other hand, at 300 ° C. or higher, since a recrystallized structure is formed in the hot-rolled sheet, a fibrous group of identical crystal orientations is generated after temper annealing, and constriction occurs during the piercing and burring process. Therefore, the finish temperature of hot finish rolling is 250 ° C. or higher and lower than 300 ° C. More preferably, it is 260 to 290 ° C.

(Cold working process)
The cold working step is a step of performing cold working (cold rolling) with a cold working rate of 96% or more after the hot rolling.
After the hot rolling is completed, the cold working is performed once or a plurality of times, so that the fin material has a desired final thickness. However, if the cold work rate is less than 96%, the sub-crystal grains become coarse after the temper annealing, and furthermore, the generation of β-Fiber becomes insufficient. Therefore, the cold working rate in cold working is 96% or more.
If intermediate annealing is performed during this cold working process, it becomes difficult to achieve a cold working rate of 96% or more. For this reason, intermediate annealing is not performed during the cold working process. The cold working rate in the case of performing the intermediate annealing in the cold working step indicates the working rate from the intermediate annealing to the final plate thickness.
In addition, since a cold work rate is so preferable that it is high, there is no upper limit in particular.

(Refining annealing process)
The temper annealing step is a step of performing temper annealing (finish annealing) that is held at a temperature of 160 ° C. to 250 ° C. for 1 to 6 hours after the cold working.
If the temperature of temper annealing is less than 160 ° C., a sufficient structure recovery effect cannot be obtained. On the other hand, when the temperature of temper annealing exceeds 250 ° C., recrystallized grains are generated after annealing, and cracks are generated starting from this. In addition, the refinement of the sub-crystal grains is not promoted, and the production of β-Fiber becomes insufficient. Therefore, the temperature of temper annealing is set to 160 ° C to 250 ° C.

(Surface treatment process)
When the fin material (10) includes the base treatment film (2), the corrosion-resistant film (3), and the hydrophilic resin film (4), it is performed as follows.
The formation of the base treatment film (2) is performed by applying a chemical conversion treatment liquid such as a phosphate chromate treatment or a zirconium phosphate treatment to the aluminum plate (1) by spraying or the like. Moreover, it is preferable to perform a degreasing treatment on the surface of the aluminum plate (1) as a pretreatment for forming the base treatment film. The degreasing treatment on the surface of the aluminum plate (1) is performed by spraying an alkaline aqueous solution on the surface of the aluminum plate (1) and then washing with water.
The corrosion-resistant film (3) and the hydrophilic resin film (4) are formed by applying a resin paint with a bar coater or a roll coater and then baking it. The baking temperature (the temperature reached by the aluminum plate) is appropriately set depending on the resin paint to be applied, but is generally in the range of 100 ° C to 300 ° C.

The embodiments for carrying out the present invention have been described above. Below, the Example which confirmed the effect of this invention and the reference example are demonstrated. In addition, this invention is not limited to this Example.

(Production method of specimen)
First, a fin material was produced by the following method. An aluminum alloy having the composition shown in Table 1 was melted and cast into an ingot, and the ingot was chamfered and then subjected to a homogenization heat treatment at 480 ° C. or 540 ° C. for 4 hours. This homogenized ingot was hot-rolled by controlling the finish temperature of hot finish rolling to be 270 ° C. to obtain a hot-rolled sheet having a thickness of 3.0 mm. Further, each of the hot-rolled plates is cold-rolled at a cold working rate of about 97% to obtain a plate thickness of 0.1 mm, and subjected to temper annealing at the temperature and holding time shown in Table 1 to obtain an aluminum plate did. And the following surface treatment was performed. The aluminum plate was degreased by dipping in an alkaline degreasing solution for 5 seconds, and then dipped in a phosphoric acid chromate solution to form a phosphate chromate film of 15 to 40 mg / m ² on the surface of the aluminum plate. This phosphoric acid chromate-treated plate was coated with an epoxy resin corrosion-resistant resin coating with a bar coater so that the coating amount shown in Table 1 was baked at 260 ° C. for 10 seconds, and finally the water-soluble cellulose resin coating was coated with a coating amount of 200 mg. / ^{m 2} was overcoated with fin material performed 10 seconds baked at 230 ° C. (sample 1-31).

(Intermetallic compound number density)
The intermetallic compound number density of the aluminum plate was measured by the following method.

The number density of intermetallic compounds of 3 μm or more on the aluminum plate is analyzed by image analysis of a scanning electron microscope (SEM) structure obtained by photographing a sample surface having an area of 1.0 mm ² at an observation magnification of 500 times (by JEOL SEM). (20 shooting locations). The image analysis method used JEDS's EDS software (ParticleFinder) to extract and count areas of brightness greater than a certain value in the captured COMPO image. In addition, the size of an intermetallic compound means the maximum length of each compound.

(Number density of film defects)
Surface analysis (15 kV) with carbon element on the fin material surface was performed at an observation magnification of 200 times with EPMA (Electron Probe Microanalyzer) (manufactured by JEOL Ltd.) (n = 10, average value converted to around 1.0 mm ²⁾ ). In the mapping image which is the surface analysis result, a site where the characteristic X-ray intensity of carbon is equivalent to 80 mg / m ² or less in terms of the coating amount was defined as a coating defect site. Then, based on the mapping image, image analysis was performed on Software Image-Pro Plus manufactured by Nippon Ropa to measure the number of coating defects, and the coating defect density of the test material was calculated. An example of these mapping images and image analysis is shown in FIG. In addition, the said film | membrane defect site | part was attached | subjected and clarified.

(Strength)
The proof stress can be measured by cutting out a tensile test piece according to JIS No. 5 from the fin material so that the tensile direction is parallel to the rolling direction and performing a tensile test according to JIS Z 2241. In addition, the tensile speed in evaluation of a present Example , a reference example, and a comparative example was performed at 5 mm / min.

  Using the produced fin materials (Samples 1 to 31), the color crack resistance, corrosion resistance, and thermal conductivity were evaluated by the following methods, and the results are shown in Table 1.

(Color crack resistance evaluation)
The produced surface-treated fin material was press-molded by drawless molding, and the color cracking resistance was evaluated. Specifically, AF2AS manufactured by Idemitsu was used as a water-based press oil for performing pressing. Punching was performed under pressing conditions with a processing speed of 200 spm and an ironing rate of 40%.
The evaluation of color cracking resistance was evaluated by visually counting the cracks generated in the collar portion with respect to 400 press-formed product totals (100 pieces × 4 rows).
Table 1 shows “number of cracks / 400 × 100 (%)” as an occurrence rate, and the occurrence rate is less than 10% as pass (◯), and 10% or more as fail (×).

(Evaluation of corrosion resistance of materials)
Among the salt spray test methods shown in JIS Z 2371, the neutral salt spray test was performed on the aluminum plate without surface treatment to evaluate the corrosion resistance. The test time was 500 hours.

Corrosion resistance after the salt spray test was evaluated based on the results of corrosion weight reduction carried out in accordance with the corrosion weight reduction measurement method shown in ISO 8407: 2009. As the corrosion product removal solution, a mixed aqueous solution of phosphoric acid and chromic acid (85% phosphoric acid 35 mL / L, chromic anhydride 20 g / L) at 100 ° C. was used as described in the method for measuring weight loss of corrosion. The weight change of the fin material before and after the corrosion test was obtained, and the ratio of the corrosion weight loss was calculated. Corrosion weight loss is less than 2%: ○, 2% or more and less than 2.5%: Δ, 2.5% or more: x and shown in Table 1.
Blank materials (materials that have not been subjected to a corrosion test) of various test pieces were prepared, and the weight error of Al dissolved in the chromium phosphate aqueous solution was measured to correct the decrease in the corrosion weight.

(Evaluation of corrosion resistance of surface treatment materials)
The salt spray was performed for 500 hours also on the fin material prepared from the surface-treated aluminum plate. The corrosion state of the test material was visually observed, and a score was assigned according to the rating number method defined in JIS Z 2371 according to the corrosion area ratio. In Table 1, RtNo 9.5 or more (◎), RtNo 9.3 or more and less than 9.5 (◯), RtNo 9 or more and less than 9.3 (◯ △) are passed, and RtNo 9 is rejected (x) in Table 1. Show.

(Thermal conductivity)
As shown in FIGS. 3 and 4, a heat exchanger having a size described later is manufactured, and water 50 ° C. (flow rate 3 L / min) is passed through the copper tubes (A) and (B) adjacent to each other across the row, Heat was released without flowing anything in the other copper tubes. And the surface temperature of the copper tube (C) which is the same row as the copper tube (A) and adjacent to the copper tube (A) and is adjacent to the copper tube (B) reaches 30 ° C. Measure the time until.
The time required to reach 30 ° C. in the thermal conductivity evaluation is less than 15 seconds (、), 15 seconds or more and less than 20 seconds (◯), and two passes, 20 seconds or more and less than 30 seconds (Δ), 30 seconds or more The above two (x) are shown in Table 1 as rejects.
The environment at the time of measurement is room temperature 23 ° C. and relative humidity 50% (no ventilation).
The created heat exchanger was measured using 10 aluminum fins pressed with a 7φ drawless. Copper tubes were alternately passed in two rows at intervals of 14 mm through aluminum fins made of the aluminum plate of the present invention. Fin size: about 210 mm x about 25 mm, number of presses: 1 row 10 holes x 2 rows, copper tube inner diameter: about 7 mm, copper tube thickness: 0.25 mm, number of copper tubes: 20, copper tube Length: about 100 mm.
The copper tube (A) and the copper tube (C) have a temperature measurement location on the surface of the copper tube 10 mm away from the end of the aluminum fin.

Generally, since the thermal resistance of the film can be expressed by a model formula, the theoretical value of the thermal resistance of the film was obtained from the following formula (1). The (average) thermal conductivity of the precoat film is based on Shigeharu Onoki, Polymer Materials Science, published in 1973 and the 5th edition of the Aluminum Handbook. The thermal resistance of the film ^{12.54 × 10 -3 (J / m} 2 · hr · ℃) below: (◎), greater than 12.54 × ^{10 -3} 25.08 × ^{10 -3} or less: (○), The results are shown in Table 1 after being divided into 25.08 × 10 ⁻³ and 62.70 × 10 ⁻³ or less: (Δ) and 62.70 × 10 ⁻³ : (×).

  In Equation (1), H is the thermal resistance of the corrosion-resistant film, δf is the thickness of the corrosion-resistant film, and kf is the heat transfer coefficient of the corrosion-resistant film [resin].

  In general, there is a correlation between the heat exchange rate of the heat exchanger and the thermal conductivity of the film, and it can be expressed by a model equation such as the following equation (2). Thereby, it can be explained that the overall heat transfer coefficient is affected when the film is thinned.

In Equation (2), K ₀ : Overall heat transfer coefficient, E: Thermal resistance of the heat transfer part in the copper pipe, F: Thermal resistance of the air side heat transfer part, G: Thermal resistance of the copper pipe, H: Precoat film I: The thermal resistance of contact between the copper tube and the fin.

Table 1 shows the calculation results of the thermal resistance and overall heat transfer coefficient of these corrosion-resistant films.
In addition, about the thing which does not satisfy | fill the range and preferable range of this invention concerning Claim 1 or Claim 2 , it shows by underlining a numerical value.

As shown in Table 1, the test material No. 2 , 3, 7 to 10 and 19 were excellent in the corrosion resistance after the surface treatment, the thermal conductivity of the coating, and the color cracking resistance in order to satisfy claim 1 of the present invention. Sample No. of Reference Example Since 1, 4 to 6, 16, and 17 also satisfy conditions other than the coating amount of claim 1 of the present invention, they were excellent in corrosion resistance, thermal conductivity of the coating, and color cracking resistance.

In addition, sample material No. of a reference example . In No. 12, since the Si content exceeds the specified value, the number of intermetallic compounds of 3 μm or more increases, and as a result, the film defect number density increases. However, coating defect number density are specified value (300 / mm ²⁾ Ri der Hereinafter, although not degraded self corrosion resistance is large materials, corrosion resistance after the surface treatment not be said to have been secured.

In addition, the test material No. Since 6 , 11 and 13 had a Cu content exceeding the specified value, the intermetallic compound containing Cu increased and the self-corrosion resistance of the material deteriorated . Sample No. of Reference Example 6 has secured corrosion resistance after the surface treatment.

No. 4 is No.4. Since the soaking temperature was higher than 1, the intermetallic compound of 3 μm or more exceeded 2500 / mm ² . For this reason, although the number of film defects slightly increases within the specified film thickness, the self-corrosion resistance of the material and the corrosion resistance after the surface treatment are good.

No. No. 7 2, no. Since the soaking temperature is higher than 3, the intermetallic compound of 3 μm or more exceeds 2500 / mm ² . Moreover, although the number of film defects slightly increases even within the specified film thickness, the self-corrosion resistance of the material and the corrosion resistance after surface treatment are good.

In addition, the test material No. 1 , 16 , and 17 are different in corrosion resistance resin, but have some differences, but have good corrosion resistance and thermal conductivity.
Sample No. of Example 2, although the even 1 9 as well as corrosion resistance resin is in some differences for different corrosion resistance and thermal conductivity is good.
Sample No. of Reference Example Similarly to the above, 15, 18 and 20 are different in corrosion-resistant resin, so that there is some difference, but the thermal conductivity is good.
However, thermally conductive theoretical value of the thermal conductivity and a resin of the heat exchanger was high value in the order of epoxy ≒ acrylic>Urethane> polyethylene.

On the other hand, since Comparative Examples 21-34 did not satisfy the scope of the present invention, the following results were obtained.
No. 21-No. Since No. 23 satisfies the range of the coating amount of the present invention, the thermal conductivity is good. However, since the number density of coating defects exceeds the upper limit value, there are many starting points of corrosion and the corrosion resistance is poor.

  No. 24, no. 25, no. 32, no. 33, no. No. 34 satisfies the range of the number density of film defects and thus has good corrosion resistance after the surface treatment, but exceeds the upper limit of the film amount, so that the thermal resistance of the film becomes high and the thermal conductivity is inferior.

  No. 26, no. In No. 27, the amount of the film is less than the lower limit value so that the film can easily pass through water, and the number density of film defects exceeds the upper limit regardless of the state of the untreated surface of the fin material. inferior.

  No. Since No. 28 satisfies the coating amount and the number density of coating defects, it has good corrosion resistance and thermal conductivity. However, since the Fe content of the aluminum plate was below the specified range, the crystal grains were coarsened and the color cracking resistance was poor.

  No. 29-No. Since No. 31 satisfies the coating amount and the number density of coating defects, it has good corrosion resistance and thermal conductivity. However, since the Fe content exceeded the specified range, the intermetallic compound was coarsened and the color cracking resistance was poor.

  The aluminum fin material for heat exchanger according to the present invention has been described in detail with reference to the best mode and examples. Needless to say, the contents of the present invention are not limited to the above-described embodiments, and can be appropriately modified and changed without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Aluminum plate 2 Ground treatment film 3 Corrosion-resistant film 4 Hydrophilic resin film 10 Fin material (Aluminum fin material for heat exchangers)

Claims (4)

An aluminum fin material for a heat exchanger comprising an aluminum plate and a corrosion-resistant film formed by a roll coater or a bar coater on the surface of the aluminum plate,
The aluminum plate is composed of Fe: 0.05 to 0.4 mass%, Cu: 0.04 mass% or less (including 0 mass%), Ti: 0.01 mass% or more and 0.08 mass% or less , Si: Including 0.15% by mass or less (including 0% by mass), the balance being Al and inevitable impurities, and the number density of intermetallic compounds having a maximum length of 3 μm or more on the surface thereof is 2766 / mm ² or less,
The corrosion-resistant film is composed of a corrosion-resistant resin whose main component is at least one of a urethane-based resin and an epoxy-based resin, the film amount is 100 to 800 mg / m ² , and the film defect number density is 300 pieces / mm ² or less. An aluminum fin material for a heat exchanger, characterized in that there is. ^{2. The} aluminum fin material for a heat exchanger according to claim 1 , wherein the aluminum plate has a number density of intermetallic compounds having a maximum length of 3 μm or more on the surface thereof of 2500 / mm ² or less. The aluminum fin material for heat exchanger further includes a base treatment film between the aluminum plate and the corrosion-resistant film, and the base treatment film is made of an inorganic oxide or an organic-inorganic composite compound and has a thickness of 1 nm to 100 nm. The aluminum fin material for a heat exchanger according to claim 1 or 2 , characterized in that: The aluminum fin material for heat exchanger further includes a hydrophilic resin film on the corrosion-resistant film, and the hydrophilic resin film includes a hydrophilic resin, and the film amount is 50 to 10,000 mg / m ^2. The aluminum fin material for a heat exchanger according to any one of claims 1 to 3 , characterized in that: