JP2019074281A - Aluminum film with hydrophilic coating film, coating material for forming hydrophilic coating film, method for manufacturing aluminum fin and heat exchanger - Google Patents

Abstract

To provide an aluminum fin having excellent hydrophilic property after coating, obtaining excellent hydrophilic property even after brazing, capable of obtaining a hydrophilic film where discoloration never occurs, and having beautiful appearance.SOLUTION: An aluminum fin comprises a hydrophilic coating film provided on at least one of a front face or rear face of a base material, and mainly consisting of aluminate, wherein the base material is composed of aluminum or aluminum alloy. Also, the aluminum fin employs configuration comprising of a hot water- or water-washed hydrophilic coating film of the hydrophilic coating film provided on at least one of the front face or rear face of the base material composed of aluminum or aluminum alloy, and mainly consisting of aluminate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a highly hydrophilic aluminum fin provided with a hydrophilic coating film, a paint for forming a hydrophilic film, a method for producing the aluminum fin, and a heat exchanger provided with the aluminum fin.

A heat exchanger in which a copper tube and an aluminum fin are mechanically joined is widely used as a heat exchanger for air conditioning such as an air conditioner.
However, due to the recent increase in the price of copper metal, there is an increasing demand for replacing all members including tubes with inexpensive aluminum. Aluminum is excellent in lightness, processability and thermal conductivity, is recyclable, and is inexpensive.

As an example of this kind of air conditioning heat exchanger, as described in Patent Document 1 below, there is a fixed space between the first header manifold and the second header manifold arranged on the left and right. A heat exchanger is known which has a configuration in which a plurality of aluminum alloy flat tubes arranged side by side are provided and corrugated fins having a shape that meanders up and down are provided between the upper and lower flat tubes.
In the heat exchanger described in Patent Document 1, the heat transfer portion of the fin is disposed between flat tubes arranged in the upper and lower direction, the air passage is divided between the flat tubes, and the air flowing through the air passage and the flat tube Heat exchange is performed with the fluid flowing inside the

  In addition, a flux composition consisting of a synthetic resin containing a polymer or copolymer of methacrylic acid ester as a main component, a flux for brazing, and an organic solvent in order to suppress retention of dew condensation water to an extruded porous flat tube made of aluminum alloy. The flat tube for heat exchangers which covered the object on the surface is described in the following patent documents 2.

JP, 2012-163317, A Japanese Patent Application Laid-Open No. 11-239867

In the above-described heat exchanger in which copper and aluminum are combined, in order to improve the hydrophilicity of the fin made of aluminum, a pre-coated fin in which an organic paint is previously applied to the fin is used. However, for aluminum heat exchangers, it is necessary to carry out brazing heat treatment in a furnace at about 600 ° C for joining members, and the organic paint is decomposed during brazing heat treatment, which is sufficient for fins. There is a problem that hydrophilicity can not be secured.
In addition, when water glass inorganic paint is used for pre-coated fins, the hydrophilicity after brazing heat treatment can be secured to some extent, but there is a problem that the inorganic paint on the fin surface is discolored to cause appearance defects in the heat exchanger. .
Furthermore, when the heat exchanger is used as the evaporator side, the water vapor in the air is condensed, and the condensed water adheres to the fins as water droplets, so that the ventilation resistance increases, the pressure loss increases, and the heat exchanger There was a problem that the capacity decline occurred.

In view of these circumstances, the present invention shows that even if it is a precoat type fin in which a hydrophilic film is previously formed before brazing, the fin exhibits the required hydrophilicity after brazing and the appearance This is a result of intensive studies to provide a fin that does not cause problems such as discoloration.
Further, the present invention has been made as a result of intensive studies in order to provide a fin which exhibits excellent hydrophilicity and does not cause problems such as discoloration, separately from the presence or absence of brazing heating.
In the present invention, a coating film mainly composed of aluminate is formed on aluminum fin, and if necessary, a hot-water-washed hydrophilic coating obtained by hot-water washing or washing is applied after brazing heat treatment It has been found that even the fins can be provided with excellent hydrophilicity. In addition, it has been found that if it is this hot water-washed hydrophilic coating, it is difficult to cause discoloration even after brazing. Furthermore, it was also found that the above-mentioned hydrophilic coating film exhibited excellent hydrophilicity regardless of the presence or absence of hot water washing.

(1) An aluminum fin according to an embodiment of the present invention is characterized in that a hydrophilic coating mainly composed of an aluminate is provided on at least one of the front surface and the back surface of a substrate made of aluminum or an aluminum alloy. .
(2) The aluminum fin according to one aspect of the present invention comprises a hot water-washed, hydrophilic coating comprising an aluminate as a main component on at least one of the front surface and the back surface of a substrate made of aluminum or aluminum alloy. It is characterized by having.

(3) In the aluminum fin according to one aspect of the present invention, the aluminate preferably comprises one or more of sodium aluminate, potassium aluminate and calcium aluminate.
(4) In the aluminum fin which concerns on one form of this invention, it is preferable that the said hydrophilic coating film contains either an acrylic resin and an inorganic colloid particle.
(5) In the aluminum fin according to one aspect of the present invention, the hot-water-washed hydrophilic coating includes an oxide of aluminum or a hydrate of aluminum as a result of peak shift analysis based on narrow scan analysis by XPS analysis Is preferred.

(6) In the aluminum fin according to one aspect of the present invention, the aluminum fin is brazed to a tube made of aluminum or an aluminum alloy, and the water contact angle of the hot water-washed hydrophilic coating after the brazing heat treatment is It is preferable that it is 40 degrees or less.
(7) In the aluminum fin according to one aspect of the present invention, the color value of the hot water-washed hydrophilic coating after brazing heat treatment is L: 70 to 100, a: -3 to +5, b: -3 to +10 Is preferred.
(8) In the aluminum fin according to one aspect of the present invention, the hot-water-washed hydrophilic coating film after the brazing heat treatment has aluminum oxide or aluminum water as a peak shift analysis result based on narrow scan analysis by XPS analysis It is preferable that it is a coating film containing a hydrate.

(9) The paint for hydrophilic film formation concerning one form of the present invention is a paint which contains an aluminate as a main ingredient and turns into a hydrophilic paint film.
(10) The coating for forming a hydrophilic coating according to an embodiment of the present invention is a coating which contains an aluminate as a main component, and which becomes a hydrophilic coating after being rinsed with hot or cold water.

(11) The paint for hydrophilic film formation concerning one form of the present invention can contain acrylic resin or inorganic colloid particles in addition to the above-mentioned aluminate.
(12) In the paint for hydrophilic film formation concerning one form of the present invention, it is preferred that the aluminate consists of one sort or two sorts or more of sodium aluminate, potassium aluminate, and calcium aluminate.
(13) In the coating material for forming a hydrophilic coating film according to one aspect of the present invention, it is applied to at least one of the front surface or the back surface of the substrate made of aluminum or aluminum alloy in a coverage of 30 to 3000 mg / m ^2. Is preferred.
(14) In the coating for hydrophilic film formation concerning one form of the present invention, it is preferred that it is a paint for hydrophilic film formation which expresses water contact angle 40 degrees or less after brazing heat treatment.

(15) In the method for producing an aluminum fin according to one aspect of the present invention, a coated film containing an aluminate as a main component is formed on at least one of the front surface and the back surface of a substrate made of aluminum or aluminum alloy. It is characterized in that the membrane is washed with water or washed to obtain a water-washed hydrophilic coating.
(16) In the method for producing an aluminum fin according to an aspect of the present invention, a coating film to which an acrylic resin or inorganic colloid particles are added in addition to the aluminate can be used.
(17) In the method for producing aluminum fin according to one aspect of the present invention, one or more of sodium aluminate, potassium aluminate and calcium aluminate can be used as the aluminate.
(18) The method for producing an aluminum fin according to an aspect of the present invention can be applied to at least one of the front surface and the back surface of a substrate made of aluminum or an aluminum alloy in a coverage of 30 to 3000 mg / m ² .
(19) A method for producing an aluminum fin according to one aspect of the present invention, a paint including an oxide of aluminum or a hydrate of aluminum as a result of peak shift analysis based on narrow scan analysis by XPS analysis as the hydrophilic coating film. It is preferred to use a membrane.

(20) A heat exchanger according to one aspect of the present invention is characterized in that the aluminum fin described above is brazed to a tube made of aluminum or an aluminum alloy.
(21) In the heat exchanger according to one aspect of the present invention, the aluminum fin described in any one of the above is a corrugated fin, and a plurality of tubes made of aluminum or aluminum alloy are arranged in parallel, The fins are brazed, and the plurality of tubes are individually brazed to the header pipe.
(22) A heat exchanger according to one aspect of the present invention is an aluminum or aluminum alloy in which a plurality of the aluminum fins according to any one of the above are arranged at predetermined intervals from one another and the plurality of aluminum fins are penetrated. A plurality of tubes are brazed to the aluminum fins, and the plurality of tubes are brazed individually to the header tube.
(23) In the heat exchanger according to one aspect of the present invention, the hot-water-washed hydrophilic coating on the brazed aluminum fin is an oxide or aluminum of aluminum as a result of peak shift analysis based on narrow scan analysis by XPS analysis. It is preferable that it is a coating film containing the hydrate of aluminum.
(23) In the heat exchanger according to one aspect of the present invention, an aluminum or an aluminum alloy in which the plurality of aluminum fins described in any one of the above are arranged at predetermined intervals from one another and the plurality of aluminum fins are penetrated. A plurality of tubes made of aluminum are expanded and joined to the aluminum fins.

  In the case of the aluminum fin according to the present invention, by forming a hydrophilic coating film mainly composed of aluminate before brazing, or a hot water rinsing hydrophilic coating film obtained by washing it with hot water or washing with water. Of course, before or after brazing, aluminum fins can be provided with excellent hydrophilicity even after brazing. In addition, if the coating is a hydrophilic coating mainly composed of aluminate, or if it is a hot water-washed hydrophilic coating, the hydrophilic coating does not change color even after being heated by brazing, and the appearance is We can provide beautiful aluminum fins.

  In the case of a paint for a hydrophilic coating film mainly comprising the aluminate according to the present invention or a paint for forming a water-washed hydrophilic film, the wax is applied by being applied to aluminum fins before brazing. It is possible to obtain a hydrophilic film which has excellent hydrophilicity and does not cause discoloration even after application, and an aluminum fin having a beautiful appearance can be produced. Moreover, the above-mentioned paint can be applied to fins of the type not brazed, can exhibit good hydrophilicity, and can obtain a hydrophilic coating film that is not likely to be discolored even when heated.

  In the case of the heat exchanger according to the present invention, since the aluminum fin of a type in which a hot water-washed hydrophilic coating corresponding to the precoated fin is provided in advance is joined to the tube by brazing, It is possible to provide a heat exchanger provided with aluminum fins that can be manufactured in the same process as the manufacturing process used and that has good hydrophilicity even after brazing. Also, by pre-coating a hot water-washed hydrophilic coating before brazing, it is possible to provide a heat exchanger equipped with an excellent-looking aluminum fin which has no discoloration in the fin appearance even after brazing. . Of course, the above-mentioned hydrophilic coating can be applied to a type of heat exchanger which does not braze fins, and a heat exchanger provided with fins having excellent hydrophilicity can be provided.

It is a front view of the heat exchanger of 1st Embodiment. The heat exchanger of 1st Embodiment WHEREIN: It is the fragmentary sectional view which took the longitudinal cross section along the length direction of the tube. It is a fragmentary sectional view showing a heat exchanger assembly before brazing a heat exchanger of a 1st embodiment. It is a perspective view which shows the heat exchanger of 2nd Embodiment. FIG. 5 is a cross-sectional view of the heat exchanger shown in FIG. 4 taken along a plane perpendicular to the longitudinal direction of the tube. FIG. 5 is a cross-sectional view of the heat exchanger shown in FIG. 4 taken along the longitudinal direction of the tube, showing a state before a brazing step. FIG. 5 is a cross-sectional view of the heat exchanger shown in FIG. 4 taken along the longitudinal direction of the tube, showing a state after a brazing process. The heat exchanger of 3rd Embodiment WHEREIN: It is sectional drawing which took the longitudinal cross-section along the length direction of a tube. The graph which shows the relationship between the sputter | spatter time and atomic concentration in the XPS analysis of an Example sample. The graph which shows the narrow scan spectrum of the sample. The data which showed the data used for the analysis of an analysis result are shown, (A) is a graph which shows the value of 2p binding energy in Al and its compound, (B) is a graph which shows an example of the peak of Al oxide.

  Hereinafter, an example of an embodiment of the present invention will be described in detail based on the attached drawings. In the drawings used in the following description, for the sake of easy understanding of the features, the features that are the features may be enlarged and shown for convenience, and the dimensional ratio of each component is the same as that of the actual heat exchanger It does not have to be.

First Embodiment
FIG. 1 is a front view showing a heat exchanger 30 of the first embodiment provided with corrugated fins.
The heat exchanger 30 of the first embodiment is used for heat exchangers for automobiles, heat exchangers for indoor and outdoor units of room air conditioners, and outdoor units for heating and ventilating air conditioning (HVAC). It is an all aluminum heat exchanger used.
The heat exchangers 30 according to the first embodiment are formed of header pipes 31 and 32 vertically arranged in parallel standing apart from each other in the left and right direction, and in parallel with the header pipes 31 and 32 with a space therebetween. A plurality of flat tubes 33 joined at right angles to the header pipes 31 and 32 and corrugated fins (corrugated fins) 34 attached to the respective tubes 33 are mainly used. The header pipes 31, 32, the tubes 33 and the fins 34 are made of aluminum or an aluminum alloy.

  A plurality of slits 36 are formed on the opposite side surfaces of the header pipes 31 and 32 at regular intervals in the longitudinal direction of each pipe, and the end of the tube 33 is inserted through the opposed slits 36 of the header pipes 31 and 32 A tube 33 is installed between the header pipes 31 and 32. Further, fins 34 are disposed between a plurality of tubes 33, 33 installed at a predetermined interval between the header pipes 31, 32, and these fins 34 are brazed to the front side or the back side of the tubes 33.

As shown in FIG. 2, the first fillet portion 38 is formed of brazing material at a portion where the end of the tube 33 is inserted into the slit 36 of the header pipe 31, 32, and the tube 33 is formed relative to the header pipes 31, 32. It is brazed. Further, in the corrugated fins 34, the second fillet portion 39 is formed by the brazing material generated in the portion between the apexes of the waves facing the front or back of the adjacent tube 33 and the surface of the tube 33 Corrugated fins 34 are brazed to the side and back side.
The fin 34 has a plate-like base 34a made of aluminum or an aluminum alloy, and a hydrophilic film 35a attached to the entire surface (front and back and both sides) of the base 34a.

  The heat exchanger 30 of the present embodiment assembles the header pipes 31, 32 and the plurality of tubes 33 and the plurality of fins 34 installed between them to form the heat exchanger assembly 41 as shown in FIG. , It is manufactured by heating and brazing. In addition, the Zn melting | diffusion diffusion layer (sacrificial anode layer) 42 is formed in the surface side and back surface side of the tube 33 by heating at the time of brazing.

Hereinafter, the main components of the heat exchanger 30 will be described in more detail.
<Base material for fins>
The base 34 a of the fin 34 is made of an alloy mainly composed of a pure aluminum such as JIS 1050 or an aluminum alloy of JIS 3003. The base 34a may be made of an aluminum alloy in which about 2% by weight of Zn is added to an aluminum alloy of JIS 3003 series.

It is preferable that the base 34 a of the fins 34 be made of a material that has a pitting potential lower than that of the tube 33. Pitting due to the corrosion of the tube 33 may lead to the leakage of the refrigerant. By setting the pitting potential of the base 34 a of the fin 34 to be lower than the pitting potential of the tube 33, it is possible to delay the corrosion of the base 34 a of the fin 34 preferentially and the pitting of the tube 33. .
The base material 34a melts the said aluminum alloy by a conventional method, and is processed through a hot rolling process, a cold rolling process, a press process, etc. In addition, the manufacturing method of the base material 34a is not specifically limited in this invention, A well-known manufacturing method can be employ | adopted suitably.

<Hydrophilic film>
The hydrophilic film 35 a is attached to the entire surface of the base 34 a of the fin 34. This hydrophilic film 35a is a film obtained by brazing and heat treating a hot water-washed hydrophilic coating film obtained by washing with water or washing a hydrophilic coating film containing an aluminate or an aluminate as a main component.
This hydrophilic film 35a is made of an aluminate such as sodium aluminate, potassium aluminate (AlKO ₃ ), calcium aluminate (Ca (AlO ₂ ) ₂ ), etc., and these aluminates such as acrylic resin, inorganic colloid liquid, etc. Manufacture is performed using a paint for forming a hydrophilic coating film, which is added with an additive according to need. The hot water-washed paint for forming a hydrophilic coating is applied to the outer surface of the substrate 34 a and dried to form a hydrophilic paint film, and this hydrophilic paint is washed with water or water-washed to obtain a water-washed hydrophilic paint 35 After that, the hydrophilic film 35a can be obtained through a brazing heat treatment. As sodium aluminate, sodium aluminum dioxide (NaAlO ₂ ), sodium tetrahydroxyaluminate (Na [Al (OH) ₄ ]) or the like can be used.

As shown in FIG. 3, the coating amount of the hydrophilic coating before hot water washing or water washing applied to the outer surface of the fin 34 before brazing shows an excellent water contact angle after brazing and obtains good brazing property. For this purpose, a range of 30 to 3000 mg / m ² can be selected. In addition, it is preferable to set it as the application amount of the range of 50-2000 mg / m < ² >, in order to make compatible the water contact angle and brazing property which were especially excellent even if the application amount before hot water flush is in the above-mentioned range.
In addition, having an aluminate as a main component means that 50 mass% or more of a coating film consists of an aluminate. Even in this range, it is desirable that 80% by mass or more, more preferably 85% by mass or more of the coating film mass is an aluminate. Of course, in the case where the additive described later is not contained, 100% of the coating film may be an aluminate.
If it is a hot-water-washed hydrophilic coating 35 obtained by hot-water washing or water-washing a coating film containing an aluminate or an aluminate as a main component, even if it receives heating at around 600 ° C. in the brazing step described later It is possible to obtain a hydrophilic film 35a that exhibits the required hydrophilicity after application.

For hot water washing, heated water (hot water), for example, about 30 to 90 ° C. hot water can be used. Washing with hot water means washing with heated or unheated liquid H ₂ O, for example, H ₂ O at any temperature or higher than normal temperature can be used. The hot and cold water used for washing may contain impurities and a small amount (for example, 1% by weight or less) of a surfactant, and may be an alkaline aqueous solution having a pH of 10 or less.
As a method of hot water washing or water washing, various methods can be used such as a method of washing by spraying using high pressure water, and a method of washing by immersing (immersing) in a water washing tank (water tank). When washing is performed by immersing in hot water or water, if a large amount of the substance removed from the coating film by washing is dissolved in the hot water washing tank or in the water tank, then Since there is a risk that the components of the coating film will adhere again, it is desirable to take measures such as supplying fresh water to the hot water washing tank or the water washing tank as necessary during the washing to maintain the water quality.

When an additive is added to the hot water-washed hydrophilic coating film 35 in addition to the aluminate, an acrylic resin, inorganic colloid particles and the like can be added in an amount of about 5% by mass to 40% by mass.
Also, if it is a hot-water-washed hydrophilic coating 35 obtained from an aluminate or a coating containing an aluminate as a main component, after being subjected to heat treatment heated to around 600 ° C. in the brazing step Also, the color change of the hydrophilic film 35a is small, and the beautiful fin 13 of the appearance with the metallic gloss inherent to aluminum or aluminum alloy can be provided. In the hot-water-washed hydrophilic coating film 35, the less color change after brazing heat treatment means that the color values measured with a color difference meter after brazing are L: 70 to 100, a: -3 to +5, b: -3 It means that the range of ~ + 10 is satisfied. If the color value of the hot-water-washed hydrophilic film 35a is within this range, the appearance of the fin 34 having the metallic gloss inherent to aluminum or aluminum alloy is not impaired.

<< Tube >>
As shown in FIG. 3, the tube 33 before brazing has a brazing coating 37 formed on the upper surface 33A and the lower surface 33B. The tube 33 is, for example, a flat multi-hole tube in which a plurality of refrigerant passages 33C are formed. Moreover, as a tube, the tube produced by bend | folding and shape | molding an aluminum alloy brazing sheet can also be used.
The tube 33 is made of, for example, an alloy mainly composed of a pure aluminum such as JIS 1050 series or an aluminum alloy of JIS 3003 series. As an example, Si: 0.10 to 0.60%, Fe: 0.1 to 0.6% by mass, Mn: 0.1 to 0.6% by mass, Ti: 0.005 to 0.2% by mass, Cu: made by extruding an aluminum alloy containing less than 0.1% by mass, the balance being aluminum and unavoidable impurities.
The tube 33 is preferably made of a material that has a pitting potential nobler than the pitting potential of the fillet portions 38 and 39 formed as shown in FIG. 2 and the base 34 a of the fin 34 after the brazing step. . Thus, corrosion of the fillets 38 and 39 and the base 34 a can be started before corrosion of the tube 33 is started, and corrosion of the tube 33 can be delayed.

The brazing coating 37 formed on the tube 33 before brazing shown in FIG. 3 is a coating applied corresponding to at least a portion to which the fins 34 are brazed. The composition of the coating film 37 for brazing is Si powder: 1.0 to 5.0 g / m ² , Zn-containing fluoride flux (KZnF ₃ ): 3.0 to 20.0 g / m ² , binder ( For example, it is preferable that it is a coating film for brazing of the compounding composition which consists of acrylic resin: 0.5-8.5 g / m < ² >.

Hereinafter, the composition which comprises the coating film 37 for brazing is demonstrated.
<Si powder>
The Si powder reacts with Al constituting the tube 33 to form a braze bonding the fins 34 and the tube 33, but during brazing, the Zn-containing flux and the Si powder melt to form a braze solution.
The Zn in the flux diffuses uniformly in the wax solution and spreads uniformly on the front and back of the tube 33. Since the diffusion rate of Zn in the liquid phase wax is significantly higher than the diffusion rate in the solid phase, this causes uniform Zn diffusion on the tube front and back, and the Zn concentration in the surface direction of the tube front and back It becomes almost uniform. In addition, as for diffusion from the surface of the tube 33 in the depth direction, Si is eutectic with Al to lower the melting point, so Zn diffuses into the eutectic composition on the surface of the tube 33 and the tube 33 The Zn melt diffusion layer 42 of a predetermined thickness is formed on the surface of The formation of the Zn melt diffusion layer 42 can improve the corrosion resistance of the tube 33.

<Si powder application amount: 1.0 to 5.0 g / m ² >
If the coating amount of Si powder is less than 1.0 g / m ² , there is a possibility that the wax formation may be insufficient, and if the coating amount exceeds 5.0 g / m ² , the melting amount of the tube increases and the tube Is not preferable because the wall thickness of the For this reason, it is preferable that content of Si powder in the coating film 37 for brazing shall be 1.0-5.0 g / m < ² >.
<Si powder particle size: Maximum particle size: D (99): 30 μm or less>
If the particle size of the Si powder is 30 μm or less in D (99), it is possible to form a uniform Zn melt diffusion layer 42, but if it exceeds 30 μm, deep erosion locally occurs and uniform Zn There is a possibility that the melt diffusion layer 42 can not be formed. Therefore, the particle size of the Si powder is preferably 30 μm or less at the maximum particle size D (99). In addition, D (99) is the particle size of the particle | grains which accumulate from a small particle in a volume ratio, and become 99% of the whole. All these values can be measured by the laser light scattering method.

<Zn-containing flux, non-Zn-containing flux>
The Zn-containing flux forms the Zn melt diffusion layer 42 on the surface of the tube 33 at the time of brazing, and has an effect of improving the pitting resistance. In addition, at the time of brazing, the oxide film on the outer surface of the tube 33 is destroyed, spreading of the brazing, and promoting the wetting to improve the brazing property. Since this Zn-containing flux has a higher activity than a flux not containing Zn, good brazability can be obtained even using a relatively fine Si powder. As the Zn-containing flux, one or more of KZnF ₃ , ZnF ₃ and ZnCl ₂ can be used. A non-Zn containing flux may be added to the Zn containing flux.

As a non-Zn-containing flux, a fluoride-based flux or a potassium fluoroaluminate-based flux is a flux containing KAlF ₄ as a main component, and various compositions to which additives are added are known. Examples thereof include those having a composition of K ₃ AlF ₆ + KAlF ₄ , Cs _(x) K _(y) F _{(z), and the} like. In addition, a fluoride-based flux (for example, a potassium fluoroaluminate-based flux) to which a fluoride such as LiF, KF, CaF ₂ , AlF ₃ , or K ₂ SiF ₆ is added can also be used. The addition of a fluoride-based flux (for example, a potassium fluoroaluminate-based flux) in addition to the Zn flux contributes to the improvement of the brazing property.

<Flux coating amount: 3.0 to 20 g / m ² >
If the coating amount of the Zn-containing fluoride flux is less than 3.0 g / m ² , the potential difference in the case of using the heat exchanger 30 becomes low, and there is a possibility that the sacrificial effect may not be exhibited. In addition, since the surface oxide film of the tube 33 (brazing material) is insufficiently broken and removed, there is a possibility that a brazing failure may occur. On the other hand, if the coating amount exceeds 20 m ² , the potential difference becomes excessive, the corrosion rate increases, and the corrosion prevention effect due to the presence of the Zn melt diffusion layer 42 may become short. For this reason, it is preferable to make the application quantity of Zn containing fluoride type flux into 3.0-20 g / m < ² >. The Zn-containing fluoride flux can use KZnF ₃ as an example. The aforementioned non-Zn-containing flux can be added in addition to the Zn-containing flux.

<Binder application amount: 0.5 to 8.5 g / m ² >
The brazing coating 37 can contain a binder in addition to the Si powder and the Zn-containing fluoride flux. An acrylic resin can be mentioned as an example of a binder.
The binder functions to fix the Si powder and the Zn-containing flux necessary for the formation of the Zn melt diffusion layer 42 on the front and back of the tube 33, but when the amount of the binder applied is less than 0.5 g / cm ² At the time of application, the Si powder and the Zn flux may fall out of the tube 33, and the uniform Zn melt diffusion layer 42 may not be formed. On the other hand, if the coating amount of the binder exceeds 8.5 g / cm ² , the brazing property may be deteriorated by the binder residue, and the uniform Zn melt diffusion layer 42 may not be formed. Therefore, the coating amount of the binder is preferably 0.5 to 8.5 g / m ² . The binder usually evaporates by heating at the time of brazing.

  The method for forming the coating film 37 for brazing comprising Si powder, flux and binder is not particularly limited in this embodiment, and a spray method, a shower method, a flow coater method, a roll coater method, a brush coating method, an immersion method It can be carried out by an appropriate method such as a method or an electrostatic coating method.

<< header pipe >>
The aluminum alloy which comprises the header pipes 31 and 32 is preferably an aluminum alloy based on an Al-Mn system.
For example, it is preferable to contain Mn: 0.05 to 1.50%, and to contain Cu: 0.05 to 0.8% and Zr: 0.05 to 0.15% as other elements. it can.

<< manufacturing method >>
An example of the manufacturing method of the heat exchanger 30 provided with the fin 34 and the tube 33 which were mentioned above is demonstrated below.
First, the tube 33 and the fins 34 are prepared. As for the fins 34, a hydrophilic coating is formed on at least the front and back surfaces of the base 34a by a coating method, and the hot water washing hydrophilic coating 35 is formed by hot water washing or water washing.
Most of the film thickness is removed by washing with hot water or washing with water, or the coating film containing the above-mentioned aluminate or aluminate as a main component, and an extremely thin hot water-washing hydrophilic coating having a thickness of about 10 nm to 500 nm. 35 remain. According to the analysis by XPS analysis (X-ray photoelectron spectroscopy), the hot-water-washed hydrophilic coating film 35 shows that the metal component constituting the aluminate such as sodium aluminate, for example, sodium almost disappears in sodium aluminate When an acrylic resin is used as an additive, carbon of the acrylic resin almost disappears, and it means a coating film having a film thickness of about 50 nm in terms of SiO ₂ . It is known from XPS analysis that aluminum hydrate or oxide and oxygen are present in the coating film of this residue. Therefore, it can be estimated that the hot-water-washed hydrophilic coating 35 is an extremely thin coating composed of aluminum hydrate or aluminum oxide and oxygen.

  As shown in FIG. 3, the heat exchanger assembly 41 is assembled by assembling the header pipes 31 and 32, the tube 33 and the fins 34 using the tubes 33 coated with the brazing coating 37 on the joint surface with the fins 34. Configure Both ends of the tube 33 are inserted into the slits 36 provided in the left and right header pipes 31 and 32, and assembled so that the corrugated fins 34 are positioned above and below the tube 33. The corrugated fins 34 are disposed such that the top of the corrugation contacts the upper or lower surface of the tube 33.

  Next, a brazing step is performed by heating to a temperature above the melting point of the brazing coating 35, for example, 580 to 620 ° C. for several minutes in a heating furnace. By heating, the brazing coating 37 formed on the tube 33 is melted and becomes a brazing liquid. The wax flows into the gap between the top of the fin 34 and the upper or lower surface of the tube 33 by capillary force to fill the gap. Subsequently, by cooling, as shown in FIG. 2, the brazing liquid solidifies, and the first fillet portion 38 and the second fret portion 39 are formed. The header pipes 31 and 32, the tube 33 and the fins 34 are joined by these fillets 38 and 39.

  The heat treatment conditions at the time of brazing are not particularly limited. As an example, the inside of the heating furnace is a nitrogen atmosphere, and the heat exchanger assembly 41 is heated to a brazing temperature (substantial temperature) of 580 to 620 ° C. at a heating rate of 5 ° C./min or more, and the brazing temperature is 30 seconds or more The temperature may be maintained and the cooling rate from the brazing temperature to 400 ° C. may be 10 ° C./min or more.

At the time of brazing, the coating film 37 is melted by heating to an appropriate temperature in an appropriate atmosphere such as an inert atmosphere. In this case, the activity of the flux is increased and Zn in the flux diffuses in the thickness direction of the tube 33, and the oxide film on the surface of both the braze material and the tube is broken to be between the braze material and the tube Promote the wetting of
During brazing, a portion of the aluminum alloy matrix constituting the tube 33 reacts with the composition of the brazing coating 37 to be brazed, and the tube 33 and the fins 34 are brazed. In the upper surface layer portion and the lower surface layer portion of the tube 34, Zn in the flux is diffused by brazing to form a Zn melt diffusion layer (sacrificial anode layer) 42 which is wrinkled more than the Zn non-diffusion portion of the tube.
The region receiving Zn diffusion on the tube surface side or the lower surface side is more wrinkled than the inner side in the thickness direction of the tube 33 (region not receiving Zn). Here, the inner side in the thickness direction of the tube 33 indicates a region deeper in the thickness direction of the tube 33 than the surface layer region or the back layer region of the tube 33 in which the melt diffusion layer 42 is formed.

The aluminate or aluminate-based coating applied over the entire surface of the fin 34 is hot-water-washed in a hot-water-washed hydrophilic coating 35, although it is somewhat degraded by heating during brazing heat treatment, but most of it Remains, and a hydrophilic film 35a is formed.
Therefore, the result of peak shift analysis based on narrow scan analysis by XPS analysis for the hydrophilic film 35a after brazing heat treatment shows that it is a coating film containing aluminum oxide or aluminum hydrate. .

<< Effect >>
According to the structure of this embodiment, good brazing is performed, and fillets 38 and 39 of sufficient size are formed between the tube 33 and the fins 34.
The fillet portions 38 and 39 have a lower pitting potential than the Zn non-diffusion portion of the tube 33 and the fins 34. Therefore, it can corrode preferentially as compared with the Zn non-diffusion portion of the tube 33 and the fin 34, and can delay the pitting corrosion of the tube 33 and the fin 34. Further, since the Zn melt diffusion layer 42 is corroded in the state of surface corrosion next to these corrosions, it is possible to suppress the occurrence of pitting in the tube 33.

Since the hydrophilic film 35 a which has been subjected to the heat treatment process at the time of brazing is formed on the fin 34 after brazing shown in FIG. 2, the hydrophilicity of the fin 34 can be increased. Therefore, the hydrophilic film 35 a can be formed by a precoating process which is previously formed on the base 34 a of the fin 34 before the heat exchanger 30 is assembled. Since the process of separately forming a hydrophilic film by post coating after brazing is not necessary, the heat exchanger 30 with a simplified manufacturing process can be provided.
In addition, the hot-water-washed hydrophilic paint film 35 obtained by washing with water or washing a paint film containing an aluminate or an aluminate as the main component is discolored even after being heated to about 600 ° C. through a brazing process. Few. Therefore, the appearance of the fins 34 made of aluminum or aluminum alloy having a metallic luster is not impaired.

In the embodiment described above, a structure in which the brazing coating 37 for brazing is provided on the outer surface such as the front surface or the back surface of the tube 33 is adopted. A placement bra may be placed around the portion 34 to be brazed and the brazed structure may be employed.
The tube 33 and the fin 34 may be brazed and joined by melting the setter by heating at the time of brazing and distributing the molten solder to the boundary portion between the tube 33 and the fin 34.

Alternatively, the fins 34 may be formed of a brazing sheet having a two-layer structure including a core layer and a brazing material layer, and the tube 33 may have a structure in which the coating film 37 for brazing is not provided.
In this case, the above-mentioned hydrophilic film 35a can be provided on the side or both sides of the brazing sheet on which the brazing material layer is not provided. Alternatively, the fins 13 can be formed of a three-layered brazing sheet having a brazing material layer on both sides of the core material layer.

  When using a brazing sheet, as an example, the core material layer is Zn: 4% or less, Mn: 0.5 to 2.0%, Si: 1.3% or less, Fe: 0.25% or less by mass% , Cu: 0.5% or less, and consists of an aluminum alloy having the composition of the balance Al and unavoidable impurities, the brazing material layer contains Si: 5.0-13.0% by mass%, the balance Al And a combination of an aluminum alloy having a composition of unavoidable impurities.

"2nd Embodiment"
FIGS. 4 to 7 show a heat exchanger according to a second embodiment of the present invention, and the heat exchangers 11 according to the second embodiment are disposed parallel to each other as shown in FIG. A pair of header pipes 14, and a plurality of flat tubes 22 joined in parallel at a distance from each other between the pair of header pipes 14 at upper and lower intervals and substantially at right angles to the header pipe 14; A plurality of fins (aluminum fins) 13 which are brazed to the outer surface (upper surface or lower surface) 12 b of the tube body 12 constituting the tubes 22 and which dissipates heat to the outside air are provided. A supply pipe 15 for supplying the refrigerant to the tube 22 is connected to the upper end of one of the pair of left and right header pipes 14 via the header pipe 14. Further, to the lower end portion of the other header pipe 14, a recovery pipe 16 for recovering the refrigerant passing through the tube 22 is connected. The tube 22, the fins 13, the header tube 14, the supply tube 15, and the recovery tube 16 are all made of aluminum or an aluminum alloy.

  FIG. 5 is a partial cross-sectional view of the heat exchanger 11 taken along the plane orthogonal to the longitudinal direction of the tube 22. As shown in FIG. 5, a plurality of (six in the present embodiment) refrigerant flow paths 12 a are formed in the inside of the tubular body 12 constituting the tube 22 along the width direction. Further, as shown in FIG. 5, in the fins 13, a plurality of notches 19 having a shape corresponding to the cross-sectional shape of the tube 22 are formed at predetermined intervals in the vertical direction. The tubes 22 are fitted in these notches 19 respectively, and the individual tubes 22 are fixed to the fins 13 by brazing.

  6 and 7 are partial sectional views of the heat exchanger 11 taken along the longitudinal direction of the tube 22 in the longitudinal direction, FIG. 6 shows the state before the brazing step, and FIG. 7 is the brazing step Indicates the later state. A plurality of fins 13 are arranged in parallel along the longitudinal direction of the tube 22, and the tubes 22 are inserted through the individual notches 19. The plurality of fins 13 are arranged in parallel parallel to each other at a constant distance. The fin 13 has a bent portion 20 which is bent on one side in the thickness direction of the fin 13 along the outer surface 12 b of the tube 22 at the periphery of the notch 19. The bent portion 20 is formed, for example, by burring.

The tubes 22 and the fins 13 are arranged such that the tubes 22 pierce through a plurality of fins 13 arranged at regular intervals, and the tubes 22 are fitted in the notches 19 of the fins 13, and the fins 13 and the tubes 22 are It is fixed individually by brazing.
In the state before brazing shown in FIG. 6, the gap between the bent portion 20 formed in the notch 19 of the fin 13 and the upper or lower surface of the tube 22 is preferably about 10 μm or less. If this gap is too large, the amount of wrap around of molten solder in the brazing step described later may be insufficient, which may cause a brazing failure.
In the fin 13 of this embodiment, the tube 22 is inserted through the notch 19. However, instead of the notch 19, the slit 13 is provided with a slit-like through hole, and the tube 22 is inserted through the through hole. It is good also as composition.

Hereinafter, main components of the heat exchanger 11 will be described in more detail.
<< Fin >>
The fins 13 include a plate-like base 3 made of aluminum or an aluminum alloy, and a hydrophilic film 1 provided on substantially the entire first face 3 a and second face 3 b of the base 3 and other side faces. have.
The base 3 is made of aluminum or an aluminum alloy equivalent to the base 34 a in the heat exchanger 30 of the first embodiment.
The base material 3 is preferably made of a material that has a pitting potential of a weir more than the pitting potential of the tube 12 constituting the tube 22. Pitting corrosion caused by the corrosion of the tubular body 12 may lead to the leakage of the refrigerant. By setting the pitting potential of the base material 3 to be higher than the pitting potential of the tube 12, it is possible to delay the corrosion of the fins 13 and the occurrence of pitting in the tube 12.

<Hydrophilic film>
The fins 13 have a hydrophilic film 1 a on substantially the entire surface of the first surface 3 a and the second surface 3 b of the base material 3. The hydrophilic film 1a is obtained by subjecting the hot-water-washed hydrophilic coating 1 shown in FIG. 6 to hot-washing with a hot-water-washed coating containing an aluminate or an aluminate as the main component through heat treatment associated with brazing. The hot-water-washed hydrophilic coating film 1 is made of the same material as the hot-water-washed hydrophilic coating film 35 applied to the heat exchanger 30 of the first embodiment described above. This hydrophilic film 1a is obtained by forming a hot-water-washed hydrophilic coating 1 as in the case of the hydrophilic film 35a applied to the heat exchanger 30 of the first embodiment, and then subjecting it to a brazing heat treatment. Hydrophilic film.

<< Tube >>
As shown in FIG. 6, the tube 22 before brazing has a tube 12 and a brazing material layer 5 formed on the outer surface (upper surface or lower surface) 12 b of the tube 12. The tube body 12 is a flat multi-hole tube made of aluminum or aluminum alloy in which a plurality of refrigerant channels 12a are formed as shown in FIG.
The tubular body 12 is made of, for example, the same material as the tube 33 of the first embodiment described above.
The tube 12 is preferably made of a material having a pitting potential that is nobler than the pitting potential of the base 5 of the fillet 5A and the base 3 of the fins 13 formed through the brazing process as shown in FIG. Thereby, the corrosion of the base material 3 of the fillet 5A and the fins 13 is started before the corrosion of the tubular body 12 is started, and the corrosion of the tubular body 12 can be delayed.

In the tube body 12 of the tube 22 before brazing shown in FIG. 6, the brazing material layer 5 made of the same material as the brazing coating film 37 of the first embodiment on a part of the outer surface 12 b to which the fins 13 are joined. Is applied.
In the heat exchanger 11 before brazing shown in FIG. 6, the brazing material layer 5 of the tube 22 is located between the portion (facing surface 20 a) of the bent portion 20 of the fin 13 facing the tube 22 and the tube 22. . The brazing material layer 5 is cooled after heating (brazing step) at around 600 ° C. to solidify in a state of being filled between the facing surface 20 a and the tube 22, and as shown in FIG. As a brazing material layer), the fins 13 and the tubes 22 are brazed and joined.

As shown in FIG. 5, the outer surface 12b of the tubular body 12 has flat surface (upper surface) 6A and back surface (lower surface) 6B, and first and second side surfaces 6C and 6D adjacent to the surface 6A and back surface 6B. It consists of The first side face 6C is located on the opening side of the notch 19 of the fin 13 and is open to the outside. The second side face 6D is located on the opposite side of the first side face 6C and is disposed so as to be surrounded by the notch 19.
The brazing material layer 5 is formed, as an example, in a region of the outer surface 12 b of the tube 12 in contact with the fins 13, that is, on the surface 6 A and the back surface 6 B of the tube 12. Further, Si and Zn contained in the surface 6A and the back surface 6B of the tube 12 after brazing and the brazing material layer 5 diffuse to the tube 12 at the brazing temperature, and the surface layer portion of the tube 12 with Si A sacrificial anode layer containing Zn is formed.

<< manufacturing method >>
An example of the manufacturing method of the heat exchanger 11 provided with the fin 13 and the tube 22 which were mentioned above is demonstrated below.
First, the tube 22 and the fins 13 are prepared. The fin 13 forms a coating on the entire surface including the first surface 3a and the second surface 3b of the substrate 3 by a coating method or an immersion method, etc. The film 1 is formed.
The notch portion 19 and a bent portion 20 at the periphery thereof are formed in the fin 13. Further, as the tube 22, a tube in which the brazing material layer 5 is formed in advance on a part of the outer surface 12 b of the tubular body 12 is prepared. The formation range of the brazing filler metal layer 5 is preferably a range that covers the entire area of the upper surface, the lower surface, and the side surface of the tube 12 joined to the fins 13.
Next, as shown in FIG. 3, a plurality of fins 13 are arranged in parallel, and the tube 22 is inserted into the notch 19.

  Next, a brazing step of heating to a temperature of not less than the melting point of the brazing material layer 5, for example, 580 to 620 ° C. in a heating furnace for several tens of seconds to several minutes is performed. By heating, the brazing material layer 5 formed on the outer surface 12 b of the tube 12 melts and becomes brazing liquid. The wax flows into the gap between the facing surface 20a of the bent portion 20 of the fin 13 and the outer surface 12b of the tube 12 by capillary force to fill the gap. Subsequently, by cooling, as shown in FIG. 7, the brazing liquid solidifies and forms fillets 5A (brazing material layer). The tube 22 and the fin 13 are joined by the fillet 5A.

At the time of brazing, the brazing material layer 5 is melted by heating to an appropriate temperature in an appropriate atmosphere such as an inert atmosphere. In this case, the activity of the flux is increased, and in addition to the diffusion of Zn in the flux to the thickness direction of the brazing material (base 3 of the fin 13), the surfaces of both the brazing material and the brazing material Destroys the oxide film of the metal and promotes the wetting between the brazing material and the brazing material.
During brazing, a portion of the aluminum alloy matrix constituting the tube body 12 of the tube 22 reacts with the composition of the brazing material layer 5 to be brazed, and the tube body 12 of the tube 22 and the fins 13 are brazed . In the upper surface layer portion and the lower surface layer portion of the tubular body 12, Zn in the flux is diffused by brazing to form a sacrificial anode layer which is wrinkled more than the inside of the tubular body 12.

  The hot-water-washed hydrophilic coating 1 obtained by hot-water washing from the aluminate or the coating mainly composed of aluminate coated on the entire surface of the fin 13 is hydrophilic coating 1a by heating at the brazing heat treatment. It becomes.

<< Effect >>
According to the structure of this embodiment, good brazing is performed, and a fillet 5A (brazing material layer) of a sufficient size is formed between the tube body 12 and the fin 13.
The fillet 5A has a lower pitting potential than the tube 12 and the fins 13. Therefore, it can corrode preferentially as compared with the tube body 12 and the fins 13, and can delay pitting corrosion of the tube body 12 and the fins 13.

  In the step of melting and solidifying the brazing material layer 5 of the tube 22 to join the fins 13 and the tube 22, it is preferable to simultaneously braze the header tube 14 to the tube 22.

In the fin 13 after brazing shown in FIG. 7, since the hydrophilic film 1 a which has been subjected to the heat treatment step at the time of brazing is formed, the hydrophilicity of the fin 13 can be increased. Therefore, the hydrophilic film 1a can be formed by a precoating process which is previously formed on the base material 3 of the fins 13 before the heat exchanger 11 is assembled. Since the process of separately forming a hydrophilic film by post coating after brazing is not necessary, the heat exchanger 11 with a simplified manufacturing process can be provided.
In addition, a hot water-washed hydrophilic coating 1 obtained by hot-water washing or water-washing from an aluminate or a film mainly composed of an aluminate is heated to about 600 ° C. through a brazing step to form a hydrophilic film 1a. Even after being discolored, the color change is small, and the appearance of the aluminum or aluminum alloy fin 13 having a metallic luster is not impaired.

In the embodiment described above, the brazing material layer 5 for brazing is provided on the outer surface such as the front surface or the back surface of the tube 22. However, the brazing material layer 5 is omitted and the brazing of the tube 22 and the fins 13 is performed. A placement bra may be placed around the portion to be joined and a brazed structure may be adopted using the placement bra.
The tube 22 and the fin 13 may be brazed and joined by melting the set wax by heating at the time of brazing and distributing the molten solder to the boundary portion between the tube 22 and the fin 13.

Alternatively, the fins 13 may be formed of a brazing sheet having a two-layer structure including a core layer and a brazing material layer, and the tube 22 may not have the brazing material layer.
In this case, the above-mentioned hydrophilic film 1a can be provided on one side or both sides of the core layer. Alternatively, it is also possible to constitute a fin 13 composed of a three-layered brazing sheet having a brazing material layer on both sides of the core layer.

"3rd Embodiment"
FIG. 8 shows the third embodiment in which the hydrophilic film 1a is provided not on both sides but only on one side of the fins 13 in the plate fin type heat exchanger 11 described above with reference to FIGS. The heat exchanger 21 is shown.
In the heat exchanger 21 of this embodiment, the hydrophilic film 1a is provided only on one surface side of two opposing surfaces of the plurality of fins 13 arranged at intervals.
In the structure of the third embodiment, since the distance between the fins 13 is as small as, for example, several mm, a water droplet is generated between the fins 13 and 13 and the water droplet tries to close the gap between the fins 13 and 13 In addition, since the water droplet touches the hydrophilic film 1 a on the one side, the water droplet can be lowered along the fins 13, and the function of removing the water droplets from between the fins 13 can be sufficiently exhibited.

Also in the heat exchanger 21 of the third embodiment, similar to the heat exchanger 11 of the second embodiment, the hydrophilic film 1a can be provided on the fins 13 to obtain excellent hydrophilicity. For this reason, even if water droplets are to be attached to the gaps around the fins 13, the water droplets can be easily removed without keeping them in the gaps of the fins 13. Therefore, the gaps between the fins are not closed with water droplets, and the efficiency of the heat exchanger 21 does not decrease.
In addition, the aluminate or the film mainly composed of aluminate formed on the fin 13 is washed with hot water or washed with water, and the hot water-washed hydrophilic coating 1 is hydrophilic after being heated to around 600 ° C. through the brazing process. Even if it becomes the crystalline film 1a, almost no discoloration occurs. For this reason, the appearance of the fins 13 made of aluminum or an aluminum alloy and having a metallic luster is not impaired.

By the way, in the embodiment described above, the hydrophilic coating 35 applied to the base 34 a of the fin 34 described above is washed with hot water or washed with water to form a hot water-washed hydrophilic coating and then subjected to a brazing heat treatment. The configuration using 35a has been described. However, it goes without saying that a hydrophilic coating which has not been rinsed or rinsed with water may be used as it is as a hydrophilic coating. Of course, it is also possible to apply a hydrophilic coating 35 which has not been rinsed with water or rinsed with water, to the fins of a heat exchanger of the type not subjected to the brazing heat treatment.
That is, since the hydrophilic coating film 35 having the above-mentioned composition containing the aluminate as a main component has excellent hydrophilicity without being washed with hot water or washing with water, the hydrophilic coating film 35 is used as it is as a final hydrophilic property. You may form in a fin as a coating film.

In a heat exchanger, when joining a fin and a tube, there is known a type in which the fin and the tube are mechanically joined by diffusion by a tube expansion plug to constitute a heat exchanger. In the case of this type of heat exchanger, a plurality of fins are spaced apart, a straight pipe tube is inserted so as to pierce through the through holes formed in the plurality of fins, and the expanded plug is inserted into the tube. Expand the tube and join the fin and the tube. A heat exchanger can be configured by connecting the ends of adjacent tubes with a U-shaped tube after pipe expansion to form a pipeline.
In this type of heat exchanger, since the brazing heat treatment is not performed, it is possible to use the above-mentioned aluminate or the hydrophilic coating mainly composed thereof as the hydrophilic coating as it is. Of course, this may be further rinsed with hot water or washed with water to form a hydrophilic coated film with hot water rinsing, which may be used as a hydrophilic film.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.
<< Preparation of sample >>
Si: 0.9% by mass, Mn: 1.2% by mass, Zn: 1.5% by mass, the balance with respect to front and back surfaces of a corrugated plate-like base material composed of unavoidable impurities and Al, the following Table 1 The coating material of the main component shown in Table 1 is applied in the coating amount (coating amount) shown in Table 1 to form a coated film, and these are washed with hot water at 60.degree. C. for 10 seconds to give No. 1 to No. No. 17 corrugated aluminum fins were prepared. The No. 18 corrugated fin of Table 1 is a fin which has not formed the coating film.
Moreover, corrugated type aluminum fins of No. 19-27 of Table 1 are samples provided with the coating which is not washed with hot water.
The coating films of the samples No. 1 to No. 8 and the samples No. 11 to 17 and 19 to 27 shown in Table 1 have 100% of each component in the state of a dried coating film. No. Sample No. 10 is a coating film containing 30% by mass of acrylic resin in addition to the main component aluminate. No. Sample No. 11 is a sample containing 30% by mass of inorganic colloid particles (derived from an alumina dispersion and an aluminum monohydrate dispersion) in the coating film in addition to the main component aluminate.

Next, a tube aluminum alloy containing Si: 0.4% by mass, Mn: 0.3% by mass and the remainder including unavoidable impurities and Al is melted, and the aluminum alloy is extruded to form a flat cross-sectional shape. The flat multi-hole pipe (wall thickness 0.26 mm × width 17.0 mm × total thickness 1.5 mm) of the aluminum alloy for heat exchanger of the above was obtained.
Furthermore, the coating film for brazing was formed in the surface (upper surface), back surface (lower surface), and the side of this flat-hole multi-hole pipe. Coatings for brazing: ₃ g of Si powder (D (99) particle size 10 μm), 6 g of Zn-containing flux (KZnF ₃ powder: D (50) particle size 2.0 μm), 1 g of acrylic resin binder, as a solvent A solution consisting of a mixture of 3-methoxy-3-methyl-1-butanol and 16 g of isopropyl alcohol was roll applied and dried.

A temporary mini-core test body is constructed by assembling 10 stages of tubes with respect to the fins using the 11 tubes and the fins (10 sheets) of any of the above No. 1 to No. 27 which are corrugated in a corrugated shape. Then, these mini-core test pieces were brazed under the condition of being held at 600 ° C. for 3 minutes in a furnace under a nitrogen atmosphere.
This brazing diffuses Zn on the front and back surfaces of the tube on which the brazing coating was formed, to form a sacrificial anode layer, and a hydrophilic coating mainly composed of components of various compositions shown in Table 1 The fins were brazed so that they were used as No. 1 to No. 27 heat exchanger test pieces.

<< Examination >>
Using these heat exchanger test specimens, a color change observation test of a fin, a hydrophilicity evaluation test, a brazing property evaluation test, and a coating film adhesion test described below were performed.

[Fin discoloration observation test]
For fins after brazing at 600 ° C for 3 minutes, those whose color values measured by a color difference meter satisfy the range of L: 70 to 100, a: -3 to +5, b: -3 to +10 It was judged that there was no discoloration. Moreover, it determined that the color value did not satisfy | fill the range of L: 70-100, a: -3 to +5, b: -3 to +10 as discoloration.
[Hydrophilicity: Water contact angle after repeated wet and dry tests]
Immerse in flowing water for 8 hours and then dry for 16 hours for one cycle, and measure the water contact angle on the surface of the fin after 14 cycles for the specimen before brazing and after brazing for 3 days at 600 ° C for 3 minutes did. When the water contact angle at this time was 40 ° or less, it was judged to have good hydrophilicity.

[Brazability: Fin joint rate evaluation test]
For each brazed-joined fin, the fin was removed from the tube and the fin joint trace remaining on the tube surface was observed. Then, the number of unjoined portions (locations where brazing was performed but no joint trace was left) was counted. One hundred specimens were observed for one test body, and it was determined that one having 80 points or more (80% or more) properly joined was regarded as having good brazability.
[Coating film adhesion test]
A rubbing test was performed in which rubbing was performed ten times while pressing a felt contact terminal at a load of 500 g onto the surface of each fin after coating formation. On the fin surface after the test, a trace of friction was observed and a sample in a state in which the coating was peeled off was x, a sample of a state in which the rub was confirmed but the coating was not peeled off was ○, a change in appearance A sample in a state in which no coating film was peeled off was shown by ◎, and the coating film adhesion was evaluated.
The results of the fin discoloration test, the measurement results of hydrophilicity, the measurement results of brazing property, and the evaluation results of coating film adhesion are summarized in Table 2 below.

As is clear from the test results of the examples shown in Table 2, a hot-water-washed hydrophilic coating or a hot-water-washed or water-washed coat was obtained by washing the aluminate or the aluminate-based coating film with hot water or water. No hydrophilic coating is formed on fins as a precoat coating, and these fins are used to construct a minicore test body of a heat exchanger, and brazed using a brazing coating on the fin surface. It has been found that a heat exchanger can be produced which has a non-discoloring, excellent hydrophilic film and is also excellent in brazeability. In addition, when a hot-water-washed hydrophilic coating obtained by alumite washing or washing with an aluminate-based coating film as the main component is formed on the fin as a precoat coating film, excellent coating adhesion can be obtained. all right.
The value of the water contact angle after the wet and dry cyclic test of the example sample showed a range of 10 to 30 °. The mini-core test sample of the example is excellent in hydrophilicity which can maintain the water contact angle on the surface of the fin at a low value even under a severe test environment in which 16 cycles of 16 hours of drying after immersion in running water are carried out for 14 cycles. I was able to get Therefore, if it is a hydrophilic film consisting of a hot-water-washed hydrophilic coating obtained by hot-water washing a coating film containing an aluminate as the main component, the hydrophilicity is excellent even after high-temperature heat treatment associated with brazing. It turned out that the coating film which exhibits

On the other hand, since the coating amount of the coating film formed on the surface of the fin is too small in the comparative example of No. 12, the water contact angle after the repeated wet and dry test became large. The comparative example of No. 13 resulted in inferior brazeability because the coating film formed on the fin surface was too thick.
The brazing of aluminum is characterized in that the oxide film present on the aluminum surface during brazing heat treatment is weakened by the effect of the flux, and the brazing material that has melted the surface flows together to join a large number of places. On the other hand, if the coating film is too thick, the flux contained in the brazing material paint does not sufficiently obtain the effect of weakening the oxide film, and the flow of the molten brazing material is impeded, so that the brazing property is not good. It can be estimated to decrease.

The comparative example of No. 14 is an example in which the coating film made of polyvinyl alcohol is formed on the fin surface in place of the hot-water-washed hydrophilic coating film obtained from the coating film mainly composed of aluminate, after brazing Color change in the fins, and the water contact angle after brazing increased.
The comparative example of No. 15 is an example using the coating film consisting of carboxymethylcellulose on the fin surface instead of the hot-water-washed hydrophilic coating film obtained from the coating film mainly composed of aluminate, but after brazing Color change in the fins, and the water contact angle after brazing increased.

A comparative example of No. 16 is an example using a coating film made of sodium silicate on the fin surface in place of the hot-water-washed hydrophilic coating film obtained from the coating film mainly composed of aluminate, but brazing Color change was caused to the fins after.
A comparative example of No. 17 is an example using a coating film made of lithium silicate on the fin surface in place of the hot-water-washed hydrophilic coating film obtained from the coating film mainly composed of aluminate, but brazing Color change was caused to the fins after.
Although the comparative example of No. 18 is an example brazed without forming a coating film on the surface of an aluminum fin, although brazing property can be ensured, hydrophilicity is not obtained.
The example of No. 19-27 shows the example made into the hydrophilic coating film in the state of a dry coating film without washing with hot water. A coating film containing sodium aluminate, potassium aluminate, or calcium aluminate as a main component, and having excellent hydrophilicity and brazing property even if it is a coating that has not been rinsed with water, Good results were also obtained in terms of adhesion.
From these test results, it is possible to precoat a hot water-washed hydrophilic coating obtained from an aluminate of a desired range of application amount or a coating film containing the aluminate as a main component, or a hydrophilic coating not washed with hot water or water. If it is a heat exchanger used on the surface of fins as a film, even if it is a film by pre-coating, it is excellent in hydrophilicity after brazing, there is no problem of discoloration in appearance, and it is also excellent in brazing property It turned out that a heat exchanger can be provided.

The graph shown in FIG. 9 shows the result of elemental analysis in the film thickness direction by XPS analysis for the hydrophilic coating film obtained after hot water washing in the sample No. 10 shown in Table 1. As an XPS analyzer, trade name: PHI Quantere SXM manufactured by ULVAC-PHI, Inc. was used.
The analysis conditions are: X-ray source 25 W, pass energy 26 eV, step 0.05 eV, sputtering conditions, acceleration potential 1 kV, raster range 1 mm × 1 mm. The SiO ₂ sputtering rate is 5.02 nm / min, and the Al ₂ O ₃ sputtering rate is 2 nm / min.
The vertical axis of the graph shown in FIG. 9 indicates the atomic concentration (%), and the horizontal axis indicates the sputtering time (minutes). Since the data of Si2p and the data of Cls cross at a sputtering time of about 12 minutes, it can be estimated that a hot water-washed hydrophilic coating of about 60 nm thickness is formed, assuming that it is 5 nm / min in terms of crossed SiO ₂ . As a result of conducting the same analysis also about other coating films, the film thickness of each hot water washing hydrophilic coating film was distributed in the range of about 50 nm-500 nm.

FIG. 10 shows the result of measuring the narrow scan spectrum by XPS analysis for the hot-water-washed hydrophilic coating of the sample No. 10. In the graph shown in FIG. 10, the vertical axis represents Counts / s, and the horizontal axis represents binding energy (eV).
All spectra near the horizontal axis in FIG. 10 can be estimated to be spectra obtained from metallic aluminum on the surface portion of the aluminum base, and these peaks were present in the vicinity of 73 eV inherent to metallic aluminum.
On the other hand, the spectrum on the upper side of FIG. 10 obtained from the hot-water-washed hydrophilic coating film surface has a peak near 75 eV due to chemical shift.
FIG. 11A shows the distribution of 2p bond energy (eV) in various compounds of Al, and FIG. 11B shows an example of a standard peak of aluminum oxide.
From these comparisons, when a compound having a peak in the vicinity of 75 eV is selected, it can be estimated that aluminum oxide or aluminum hydrate is present in the hot-water-washed hydrophilic coating of the sample No. 10.
Therefore, it can be estimated that the hydrophilic coating after hot water washing contains aluminum oxide and aluminum hydrate.
In addition, as a result of measuring a narrow scan spectrum by XPS analysis about the fin surface after brazing of the sample of No. 10, the graph of the same tendency as the graph shown in FIG. 10 was obtained. From this result, it can be estimated that the hot-water-washed hydrophilic coating still contains aluminum oxide or aluminum hydrate after brazing.

  DESCRIPTION OF SYMBOLS 1 ... Hot-water-washed hydrophilic coating film, 1a ... hydrophilic film | membrane, 3 ... base material, 3a ... 1st surface, 3b ... 2nd surface, 5 ... brazing material layer, 5A ... fillet (brazing material layer), 6A ... surface, 6B ... back surface, 6C ... first side surface, 6D ... second side surface, 11 ... heat exchanger, 12 ... pipe body, 12a ... refrigerant flow path, 12b ... outer surface, 13 ... fin, 14 ... header pipe , 15: supply pipe, 16: recovery pipe, 19: notch portion, 20: bent portion, 20a: opposite surface, 22: tube, 30: heat exchanger, 31, 32: header pipe, 33: tube, 34: 34 Fin, 34a: core material, 35: hot water-washed hydrophilic coating, 35a: hydrophilic coating, 36: slit, 37: brazing coating, 38: first fillet, 39: second fillet, 42 ... Zn melt diffusion layer (sacrificial anode layer).

Claims (24)

  An aluminum fin comprising a hydrophilic coating mainly composed of aluminate on at least one of a front surface and a back surface of a substrate made of aluminum or an aluminum alloy.   An aluminum fin comprising a hot-water-washed, hydrophilic coating of a hydrophilic coating mainly composed of aluminate on at least one of the front surface and the back surface of a substrate made of aluminum or an aluminum alloy.   The aluminum fin according to claim 1 or 2, wherein the aluminate comprises one or more of sodium aluminate, potassium aluminate and calcium aluminate.   The aluminum fin according to any one of claims 1 to 3, wherein the hydrophilic coating film contains any one of an acrylic resin and inorganic colloid particles.   The hot water-washed hydrophilic coating film is a coating film containing an oxide of aluminum or a hydrate of aluminum as a result of peak shift analysis based on narrow scan analysis by XPS analysis. Aluminum fin according to any of the.   An aluminum fin to be brazed to a tube made of aluminum or an aluminum alloy, wherein the water contact angle of the hot water-washed hydrophilic coating after the brazing heat treatment is 40 ° or less. The aluminum fin as described in any one of Claim 5.   The hot-water-washed hydrophilic coating film after the brazing heat treatment is a coating film containing an oxide of aluminum or a hydrate of aluminum as a result of peak shift analysis based on narrow scan analysis by XPS analysis. An aluminum fin according to Item 6.   The color values of the hot-water-washed hydrophilic coating after brazing heat treatment are L: 70 to 100, a: -3 to +5, b: -3 to +10. The aluminum fin as described in any one.   A paint for forming a hydrophilic coating film which contains an aluminate as a main component and is a hydrophilic coating film.   A paint for forming a hydrophilic coating film, which contains an aluminate as a main component, and which becomes a hydrophilic coating film by hot water washing or water washing.   The coating for hydrophilic film formation according to claim 9 or 10, further comprising an acrylic resin or inorganic colloid particles in addition to the aluminate.   The hydrophilic coating film according to any one of claims 9 to 11, wherein the aluminate comprises one or more of sodium aluminate, potassium aluminate, and calcium aluminate. Forming paint. The method according to any one of claims 9 to 12, wherein at least one of the front surface and the back surface of the substrate made of aluminum or aluminum alloy is applied at a coverage of 30 to 3000 mg / m ² . Coating film for hydrophilic film formation.   The paint for hydrophilic film formation according to any one of claims 9 to 13, which exhibits a water contact angle of 40 ° or less after the brazing heat treatment.   A coated film containing an aluminate as a main component is formed on at least one of the front surface and the back surface of a substrate made of aluminum or aluminum alloy, and then the coated film is washed with hot water or water to obtain a hot water-washed hydrophilic coating. A method of manufacturing an aluminum fin characterized by   The method for producing an aluminum fin according to claim 15, wherein a coating film to which an acrylic resin or inorganic colloid particles are added in addition to the aluminate is used.   The method for producing aluminum fin according to claim 15 or 16, wherein one or more kinds of sodium aluminate, potassium aluminate and calcium aluminate are used as the aluminate. Aluminum according to any one of claims 15 to claim 17, wherein applying a range of coating weight 30~3000mg / m ² of aluminum or the surface or the back surface of the substrate made of an aluminum alloy to at least one How to make fins.   19. The coating film containing an oxide of aluminum or a hydrate of aluminum as a result of peak shift analysis based on narrow scan analysis by XPS analysis is used as the hydrophilic coating film. A method of producing an aluminum fin according to   A heat exchanger characterized in that the aluminum fin according to any one of claims 1 to 8 is brazed to a tube made of aluminum or an aluminum alloy.   The aluminum fin according to any one of claims 1 to 8 is a corrugated fin, and a plurality of tubes made of aluminum or aluminum alloy are arranged in parallel, and the corrugated fin is brazed between the tubes, A heat exchanger characterized in that a plurality of tubes are individually brazed to a header pipe.   A plurality of tubes made of aluminum or aluminum alloy in which the aluminum fins according to any one of claims 1 to 8 are arranged at predetermined intervals from one another, and the plurality of aluminum fins are penetrated. A heat exchanger characterized in that it is brazed to an aluminum fin and the plurality of tubes are brazed individually to a header pipe.   The hot-water-washed hydrophilic coating on the aluminum fin after brazing is a coating containing an oxide of aluminum or a hydrate of aluminum as a result of peak shift analysis based on narrow scan analysis by XPS analysis. The heat exchanger according to any one of claims 20 to 22, wherein   A plurality of tubes made of aluminum or aluminum alloy in which the aluminum fins according to any one of claims 1 to 8 are arranged at predetermined intervals from one another, and the plurality of aluminum fins are penetrated. A heat exchanger characterized by expansion joint to aluminum fins.

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