JP5117812B2 - Manufacturing method of heat exchanger - Google Patents

Description

  The present invention relates to a method of manufacturing a heat exchanger, and in particular, a method called tube expansion processing in which a hole is formed in an aluminum plate by press molding, a tube is inserted into the hole, and the tube is further expanded. It is related with the manufacturing method of the heat exchanger made by.

  Heat exchangers for home or commercial air conditioners using heat pumps are made by punching a thin metal plate such as aluminum or copper to be used as a fin to produce a molding part called a collar, and a copper tube or an aluminum tube is inserted into this collar part. Thereafter, the copper tube or the aluminum tube is mechanically expanded, or is expanded by applying hydraulic pressure or air pressure, and the fin and the tube are fixed. For example, Patent Document 1 discloses a method for manufacturing such a heat exchanger.

  As the metal thin plate for fins, an aluminum material that is lightweight and has appropriate mechanical properties, and has excellent aesthetics and moldability has become the mainstream. (Hereinafter, pure aluminum material and aluminum alloy material are collectively referred to as “aluminum material” in the present specification.) This heat exchanger is used in all environments except in extremely cold regions. In other words, it is installed in areas where there is salt damage, such as near the coast, or where it is exposed to exhaust gas etc. at the expressway, and it is also used in environments where corrosive gases are used such as semiconductor factories. . Therefore, such a heat exchanger is required to have high corrosion resistance.

  In order to improve the corrosion resistance of the heat exchanger, various studies have been made so far, and in particular, the corrosion resistance of aluminum materials used for fins has been improved. One of them is a method of forming using an aluminum material that has been subjected to surface treatment such as painting. That is, a so-called precoat material obtained by subjecting an aluminum material to surface treatment is formed into a predetermined shape, a tube is inserted into the hole, and then the tube is expanded to form a heat exchanger.

  As a surface treatment used for obtaining a precoat material, for example, as disclosed in Patent Document 2, a method of previously providing a corrosion-resistant chemical conversion film such as a phosphate chromate film on an aluminum material, or disclosed in Patent Document 3 is disclosed. As described above, there is a method of providing an acrylic resin on an aluminum material. These methods are mainly effective in improving the corrosion resistance of the flat portion of the fin.

  However, in manufacturing a heat exchanger, an aluminum material is formed into a fin material, so that a large number of cut surfaces are formed in the fin. This cut surface portion has no precoat film and the aluminum surface is exposed. As a result, corrosion tends to occur during use of the heat exchanger. In recent years, the fins are often subjected to louver processing (processing that raises the portion after slit forming) for the purpose of increasing the heat exchange rate. When the louver process is performed in this way, the cut surface of the aluminum material is increased, and moisture tends to be accumulated in the cut and raised portion, so that the corrosion is further facilitated.

  In particular, when such a heat exchanger is used in places such as Okinawa and Tokunoshima, it is a severe environment with high temperature, high humidity, and high salt, so corrosion starts from the exposed aluminum part of the fins and further generates corrosion. The clogging between the fins due to objects may cause a decrease in function, or the fins may eventually fall off.

  In order to prevent such problems, as a method of protecting the exposed aluminum cut surface, spray coating with paint containing zinc, corrosion-resistant resin such as solvent-type acrylic resin, solvent-type epoxy resin after assembling the heat exchanger To be done. However, spray coating cannot sufficiently adhere the corrosion-resistant resin to fine parts in the narrow gap between the fins, and the corrosion resistance of the cut end of the part where the aluminum cut surface is exposed and the cut surface of the louver is reduced. I can't get enough. In addition, when a solvent-type corrosion-resistant resin is used, the solvent damages the precoat film, so that the corrosion resistance may be lowered. Furthermore, the working environment is also deteriorated by the solvent, which is not preferable.

  In addition, as described above, when spraying paint containing zinc, sacrificial anticorrosive action can be expected because zinc is a base metal than aluminum, but white corrosion products are produced by the corrosion of the sacrificial zinc. Since a large amount of is generated, the appearance becomes dirty and the appearance may be deteriorated. Furthermore, since the anticorrosive action after zinc is lost due to corrosion cannot be expected, the heat exchanger cannot withstand long-term use.

  On the other hand, there is a method of providing a chemical conversion film such as a phosphoric acid chromate film on the heat exchanger after assembly. However, sufficient corrosion resistance of a heat exchanger used in a harsh environment cannot be ensured only with the chemical conversion film. In addition, after forming a chemical conversion film on the heat exchanger after assembly, if a corrosion resistant paint is further provided by post coating, the corrosion resistance is improved compared to the case of only the chemical conversion film, but the chemical conversion film and the corrosion resistant paint Since it is inferior to the adhesiveness between the two, the coating film may peel off when used over a long period of time. This phenomenon is considered to be because the adhesion between the chemical conversion film and the corrosion-resistant coating film is due to a bond that is very weak such as a hydrogen bond. Furthermore, performing both the formation of the chemical conversion film and the application of the corrosion-resistant paint leads to an increase in the number of processes and an increase in cost, and there is also a concern about an increase in environmental burden due to the rinse water waste liquid after the chemical conversion film treatment.

It is possible to post-coat the corrosion-resistant paint directly on the heat exchanger after assembly without providing a chemical conversion film. Depending on the case, peeling of the coating film may occur.
JP 59-43538 A JP 2000-226675 A Japanese Patent Laid-Open No. 06-65524

  The present invention has been made in view of the above-mentioned problems of the prior art, and in manufacturing a heat exchanger manufactured using tube expansion processing, a cut surface formed when a fin material is formed and processed. It was made for the purpose of protecting the exposed portion of aluminum and ensuring high corrosion resistance over a long period of time for the heat exchanger.

In order to achieve the above object, the heat exchanger of the present invention includes a step of punching a metal plate to form a hole, a step of inserting a tube into the hole formed in the metal plate, and a tube expansion of the tube. In the heat exchanger produced including the step of fixing the tube to the metal plate to form an assembly,
A corrosion-resistant resin layer containing a zirconium compound is formed on the surface of the metal plate including the end face of the hole, and the zirconium concentration in the corrosion-resistant resin layer continuously decreases from the metal plate side upward. It is a heat exchanger characterized by this.

Such a heat exchanger includes a step of immersing a part or the whole of the assembly in a water-based paint containing a zirconium compound and a water-soluble corrosion-resistant resin,
A step of heating the immersed heat exchanger at 40 ° C or higher and lower than the curing temperature of the corrosion-resistant resin for 1 second or more, and then heating to a temperature equal to or higher than the curing temperature of the corrosion-resistant resin;
It is implement | achieved by the manufacturing method containing.

It is particularly preferable that the zirconium compound is at least one of zirconium oxide, zirconium hydroxide, zirconium carbonate, zirconium phosphate, and fluorinated zirconium acid.
Moreover, it is more preferable that the water-soluble corrosion-resistant resin contains one or more of acrylic acid, acrylic acid ester, acrylamide, acrylic-modified epoxy, and urethane.

  According to the heat exchanger manufacturing method of the present invention, the corrosion-resistant film can be spread to the details of the heat exchanger, and the entire surface including the exposed portion of the aluminum cut surface is reliably covered with the corrosion-resistant resin. Therefore, it is possible to ensure a high degree of corrosion resistance over a long period of time for the heat exchanger. Further, due to the action of the zirconium compound contained in the corrosion resistant resin, the adhesion of the corrosion resistant resin to the surface of the heat exchanger is greatly improved, and the high corrosion resistance of the heat exchanger can be obtained.

  Next, a preferred embodiment of the present invention will be described.

  In the method for producing a heat exchanger according to the present invention, a zirconium compound-containing corrosion-resistant resin layer (hereinafter sometimes simply referred to as a corrosion-resistant resin layer) is formed on the heat exchanger surface including the hole end face formed by punching. Immerses the assembled heat exchanger in a water-based paint containing a zirconium compound and a water-soluble corrosion-resistant resin, and performs heating and drying under predetermined conditions described later. By performing this step, a kind of inclined structure is obtained in which the concentration of the zirconium compound in the corrosion-resistant resin decreases upward from the surface of the heat exchanger. Therefore, a corrosion-resistant film structure having the same effect as that obtained when an inorganic chemical conversion film and a resin film are sequentially formed on the surface of the metal plate can be realized in one step. In addition, since the zirconium compound concentration in the corrosion-resistant resin continuously changes, there is no problem of insufficient adhesion between the chemical conversion film and the resin coating film.

  As the zirconium compound, it is preferable to use at least one of zirconium oxide, zirconium hydroxide, zirconium carbonate, zirconium phosphate, and fluorinated zirconium acid. The amount of the zirconium compound is preferably in the range of 0.2 to 5.5% by weight based on the solid content of the water-soluble corrosion-resistant resin. If it is less than 0.2% by weight, the amount of the zirconium compound is too small and the adhesion between the corrosion-resistant resin layer and the heat exchanger surface is poor. On the other hand, if it exceeds 5.5% by weight, the corrosion-resistant resin may be gelled, which is not preferable.

  As the water-soluble corrosion-resistant resin, it is preferable to use at least one of acrylic acid, acrylic acid ester, acrylamide, acrylic-modified epoxy, and urethane.

  The formation amount of the corrosion resistant resin layer can be adjusted by adjusting the solid content concentration of the corrosion resistant resin in the water-based paint. In the present invention, it is preferable that the resin solid content concentration is 5 to 30% by weight. If the resin solids concentration is less than 5%, the required amount of corrosion-resistant coating cannot be secured, the viscosity of the water-based paint will be low, paint repellency will occur, and it will not adhere to the cut surface of the metal plate. Or invite you. On the other hand, if the resin solid content concentration is 30% or more, the viscosity of the water-based paint becomes too high to reliably form a corrosion-resistant film up to the details of the heat exchanger, and the film becomes too thick. A bridge may be formed between the fins, and the heat exchange performance of the heat exchanger may be hindered.

The formation amount of the corrosion-resistant resin layer provided in the heat exchanger is adjusted to be 2.0 to 30.0 g / m ² as described above. When the amount of the corrosion-resistant film is less than 2.0 g / m ² , sufficient corrosion resistance cannot be obtained. On the other hand, if it exceeds 30.0 g / m ² , the corrosion resistance is not improved any more, and the heat transfer from the fin material to the air is lowered, which is not preferable.

  In order to obtain the inclined structure of the corrosion-resistant resin, which is a feature of the present invention, a heating / drying step after immersing the heat exchanger in the water-based paint is important. In a water-based paint containing a zirconium compound and a water-soluble corrosion-resistant resin, the zirconium compound is uniformly dispersed in the liquid. Therefore, just immersing the heat exchanger in this paint, heating and drying by the usual method, only a film in which the zirconium compound is uniformly dispersed can be obtained, which is a feature of the present invention, in the corrosion-resistant resin layer. It is not possible to obtain a structure in which the zirconium concentration continuously decreases from the metal plate side upward. In order to obtain a structure which is a feature of the present invention, that is, a structure rich in zirconium compound near the surface of the metal plate of the corrosion-resistant resin layer, gradually decreasing in zirconium compound as it goes upward, and rich in resin near the surface of the corrosion-resistant resin layer In the step of providing the corrosion-resistant resin layer, it takes time for the metal on the surface of the metal plate to undergo a chemical reaction with the zirconium compound.

  In order to make this possible, first, after dipping in a water-based paint, the removed heat exchanger is held at 40 ° C. or higher and at an atmospheric temperature lower than the temperature at which the water-soluble corrosion-resistant resin is cured for 1 second or longer. At this temperature, the water and solvent components in the water-based paint only volatilize gradually, and the resin does not cure. The zirconium compound is in a state where it can move freely in the water-based paint on the surface of the metal plate. Therefore, before the resin hardens, the metal on the surface of the metal plate and the zirconium compound in the water-based paint selectively react repeatedly, and a region rich in the zirconium compound is formed near the surface of the metal plate.

  Thereafter, the resin is cured by heating the heat exchanger to a temperature equal to or higher than the curing temperature of the water-soluble corrosion-resistant resin. As a result, a corrosion-resistant resin layer having a so-called inclined structure as described above can be obtained. (Hereafter, the process of drying and curing the resin coating aqueous solution on the surface of the heat exchanger by heating is referred to as “baking process” as appropriate.) The time for this baking process is 5 minutes or more, and the productivity and manufacturing of the heat exchanger What is necessary is just to set suitably in consideration of line capability etc. If it is less than 5 minutes, the corrosion-resistant resin layer may be insufficiently cured.

  The type of the baking apparatus is not particularly limited as long as the above-described temperature and time conditions can be realized. A hot stove, an infrared furnace, or the like can be used, but a hot stove is optimal from the viewpoint of processing efficiency.

  In the manufacturing method of the heat exchanger of the present invention, when the corrosion resistant resin layer is provided, the entire heat exchanger is immersed in the water-based paint, so that the coating of the corrosion resistant resin layer is spread to the details of the heat exchanger. Thus, the entire surface including the portion where the cut surface of the metal plate is exposed can be reliably covered with the corrosion-resistant resin layer. In addition, as long as it can cover with the corrosion-resistant resin from which the cut surface of a metal plate is exposed at least, the aspect by which the required part is immersed may not be necessarily immersed in the whole heat exchanger.

[Example 1]
An aluminum alloy thin plate (plate thickness of 0.100 mm) corresponding to JIS3003 was prepared. This aluminum alloy thin plate was formed by a fin press apparatus, and then a copper tube was inserted into the hole and expanded to produce a heat exchanger having a size of 210 mm × 300 mm × 38.1 mm. In molding, the diameter of the hole portion was 7.3 mm, and the height of the formed collar portion was 1.5 mm. In addition, since volatile press oil adhered, in order to remove this, the heat exchanger was dried at 150 degreeC for about 5 minutes.

  In order to form a corrosion-resistant resin layer on this heat exchanger, the heat exchanger is immersed in an aqueous paint (epoxy resin paint made by Dainippon Ink) containing zirconium carbonate and a water-soluble epoxy resin, and immediately after that, the temperature is increased to 40 ° C. Held for 1 second. Then, the baking process was performed at 200 degreeC. The baking time was 5 minutes.

  Heat exchangers produced by variously changing the zirconium carbonate concentration in the water-based paint and the holding conditions after immersion in the heat exchanger were designated as Invention Examples 1 to 5 and Comparative Examples 1 to 4, and evaluated as described below. .

[Evaluation of Example 1]
(1) Evaluation of the state of the corrosion-resistant resin layer: The state of the corrosion-resistant film was visually evaluated for the heat exchanger after being immersed in a water-based paint and subjected to baking treatment. The criteria for evaluation are as follows. That is, ◯ indicates that there was no abnormality, Δ indicates that film repelling occurred partially, and X indicates that film repelling occurred in many parts.

  (2) Corrosion resistance of heat exchanger: A CASS test was performed in a state in which the heat exchanger arranged in the CASS tester was joined to a compressor unit installed outside the tester and the heat exchanger was operated. The operation was repeated for 30 minutes of cooling operation and 1 hour of stoppage, and the total test time was 500 hours. After the CASS test, the heat exchanger was taken out, the area where corrosion occurred was visually confirmed, and evaluated according to the following criteria. That is, the case where the ratio of the corrosion occurrence area to the surface area of the entire heat exchanger was 30% or less was evaluated as ◯, the case where it exceeded 30% and 60% or less was evaluated as Δ, and the case where it exceeded 60% was rated as ×.

  (3) Adhesion of the corrosion-resistant resin layer: In the heat exchanger after performing the above-described corrosion resistance test, the adhesiveness of the portion where the corrosion-resistant resin layer remains is visually evaluated for the presence or absence of peeling, and then the tape adhesion test is performed. And the presence or absence of peeling was evaluated. The evaluation criteria are as follows.

No peeling of the corrosion-resistant resin layer before and after the tape adhesion test
No peeling before tape adhesion test, peeling after test ... △
Already peeled off before tape adhesion test ... ×
The evaluation results of (1) to (3) are shown in Table 1.

  (4) Confirmation of inclined structure: In order to investigate the depth direction distribution of the zirconium carbonate concentration in the corrosion-resistant resin layer, the element distribution in the depth direction was measured using a glow discharge optical emission spectrometer (GDS). The apparatus used was Horiba "JY-5000RF", and Ar gas was used as the plasma emission source. The detection wavelength of each element was C = 156 nm and Zr = 339 nm.

  As can be seen from Table 1, in Examples 1 to 5 of the present invention, the zirconium carbonate concentration in the water-based paint is in the range of 0.2 to 5.5% by weight, and the holding time after immersion in the heat exchanger is 40 ° C., 1 Because of the second, good results were obtained for the state of the corrosion-resistant film, the corrosion resistance of the heat exchanger, and the adhesion of the corrosion-resistant film.

  On the other hand, in Comparative Example 1, since the zirconium carbonate concentration in the water-based paint was as low as 0.18%, the adhesion between the corrosion-resistant resin layer and the heat exchanger surface was poor, and as a result, the corrosion resistance of the heat exchanger was reduced. It was inferior to.

  In Comparative Example 2, since the zirconium carbonate concentration in the water-based paint was as high as 6%, the water-based paint gelled and the heat exchanger could not be immersed.

  In Comparative Example 3, since the heat exchanger was immersed in the water-based paint and baked without being held at 40 ° C., the Zr compound concentration distribution in the corrosion-resistant resin layer had a uniform structure instead of an inclined structure. became. For this reason, the adhesion of the corrosion-resistant resin layer is inferior and the corrosion resistance of the heat exchanger is also insufficient.

  In Comparative Example 4, since the temperature at which the heat exchanger was held after being immersed in the water-based paint was as low as 38 ° C., the Zr compound concentration distribution in the corrosion-resistant resin layer became a uniform structure without an inclined structure. For this reason, the adhesion of the corrosion-resistant resin layer is inferior and the corrosion resistance of the heat exchanger is also insufficient.

[Example 2]
An aluminum alloy thin plate (plate thickness of 0.100 mm) corresponding to JIS3003 was prepared. This aluminum alloy thin plate was formed by a fin press apparatus, and then a copper tube was inserted into the hole and expanded to produce a heat exchanger having a size of 210 mm × 300 mm × 38.1 mm. In molding, the diameter of the hole portion was 7.3 mm, and the height of the formed collar portion was 1.5 mm. In addition, since volatile press oil adhered, in order to remove this, the heat exchanger was dried at 150 degreeC for about 5 minutes.

  In order to form a corrosion-resistant resin layer on this heat exchanger, the heat exchanger is immersed in a water-based paint (epoxy resin paint made by Dainippon Ink) containing 0.5% by weight of zirconium carbonate and a water-soluble epoxy resin. Immediately thereafter, it was held at 40 ° C. for 2 seconds. Thereafter, baking treatment was performed at various temperatures. The baking time was 5 minutes.

  The heat exchangers produced by varying the amount of the corrosion-resistant coating formed by adjusting the solid content concentration of the corrosion-resistant resin in the water-based paint are referred to as Invention Examples 1 to 7 and Comparative Examples 1 to 4 as described below. Was evaluated.

[Evaluation of Example 2]
The evaluation method and evaluation criteria in Example 2 are the same as those shown in Example 1. These evaluation results are shown in Table 2.

As can be seen from Table 2, in Examples 1 to 7 of the present invention, since the formation amount of the corrosion-resistant resin layer was in the range of 2.0 to 30.0 g / m ² , the state of the corrosion-resistant film, the corrosion resistance of the heat exchanger, Good results were obtained for the adhesion of the corrosion-resistant film.

On the other hand, in Comparative Example 1, since the amount of the corrosion-resistant resin layer formed was as small as 1.5 g / m ² , the corrosion resistance of the heat exchanger was inferior. In addition, since the resin solid content in the aqueous resin coating solution is lowered in order to achieve the above formation amount, the viscosity of the resin coating becomes insufficient. The adhesion was also insufficient.

In Comparative Example 2, since the formation amount of the corrosion-resistant film was as small as 1.8 g / m ² , the corrosion resistance of the heat exchanger was inferior.

In Comparative Example 3, the amount of the corrosion-resistant film formed was as large as 32.0 g / m ² , so that the corrosion-resistant film became too thick and bridges were formed between the fins.

  In Comparative Example 4, because the baking time was insufficient, the corrosion resistance of the heat exchanger and the adhesion of the corrosion resistant film were inferior.

Claims (6)

A step of punching a metal plate to form a hole, a step of inserting a tube into the hole formed in the metal plate, and a step of fixing the tube to the metal plate by expanding the tube to form an assembly In a heat exchanger manufactured including:
A water-based paint containing 0.2 to 5.5% by weight of a zirconium compound with respect to the solid content of the water-soluble corrosion-resistant resin on the surface of the metal plate including the end face of the hole is formed in an amount of 2.0 to 30.0 g / m ² the corrosion resistance resin layer is formed is a heat exchanger that a zirconium concentration of the corrosion-resistant resin layer is characterized in that it decreases towards the on continuously from the metal plate side. The heat exchanger according to claim 1, wherein the zirconium compound is at least one of zirconium oxide, zirconium hydroxide, zirconium carbonate, zirconium phosphate, and fluorinated zirconium acid. The heat exchanger according to claim 1 or 2, wherein the water-soluble corrosion-resistant resin contains at least one of acrylic acid, acrylic ester, acrylamide, acrylic-modified epoxy, and urethane. A step of punching a metal plate to form a hole, a step of inserting a tube into the hole formed in the metal plate, and a step of fixing the tube to the metal plate by expanding the tube to form an assembly In the manufacturing method of the heat exchanger produced including
Immersing a part or the whole of the assembly in a water-based paint containing a zirconium compound and a water-soluble corrosion-resistant resin;
A step of heating the immersed heat exchanger at 40 ° C or higher and lower than the curing temperature of the corrosion-resistant resin for 1 second or more, and then heating to a temperature equal to or higher than the curing temperature of the corrosion-resistant resin;
The manufacturing method of the heat exchanger characterized by including. The method for producing a heat exchanger according to claim 4, wherein the zirconium compound is at least one of zirconium oxide, zirconium hydroxide, zirconium carbonate, zirconium phosphate, and fluorozirconic acid. The method for producing a heat exchanger according to claim 4 or 5, wherein the water-soluble corrosion-resistant resin contains at least one of acrylic acid, acrylic acid ester, acrylamide, acrylic-modified epoxy, and urethane. .
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