JP2020051731A - Hydrophilic fin and heat exchanger - Google Patents

Abstract

To provide a fin with hydrophilicity and a heat exchanger.SOLUTION: A hydrophilic fin is an aluminum fin joined by brazing using a brazing material and a fluoride-based flux, where a surface coverage by the residual particles of the fluoride-based flux generated during brazing is 10% or more, and further, there are 500 to 2000 inorganic compound particles different from the residual particles of the flux per 1.0 mm square of the surface of the aluminum fin after brazing heat treatment.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a hydrophilic fin and a heat exchanger suitable for use in a heat exchanger.

In air conditioner heat exchangers such as air conditioners, heat exchangers in which a copper tube and aluminum fins are mechanically joined are widely used.
However, in recent years, due to the rising price of copper ingots and the demand for improved heat exchange performance, the use of low-priced aluminum pipes or aluminum flat tubes, which are superior in lightness, workability, and heat conductivity, are used instead of copper tubes. Is being considered.
Furthermore, the structure in which the copper tube is expanded by a plug and mechanically joined to the aluminum fins has a limit in improving the heat exchange performance as compared with the structure joined by brazing.

When examining the performance improvement of the air conditioner, coagulation water and frost are generated in the outdoor unit of the home air conditioner. Key to performance improvement.
In addition, if the fin spacing of the aluminum fins is reduced to reduce the size and weight of the heat exchanger, cohesive water and rainwater will be retained in the gaps between the fins due to surface tension, which will hinder heat exchange performance. The function of draining water from the fins is also key to improving performance in terms of miniaturization and weight reduction.
In order to ensure the drainage function from the aluminum fin, it is important to impart sufficient hydrophilicity to the surface of the aluminum fin.

In a heat exchanger in which a copper tube and an aluminum fin are combined, a pre-coated fin in which an organic paint is previously applied to the aluminum fin is used to improve the hydrophilicity of the aluminum fin.
However, in the case of an aluminum heat exchanger, it is necessary to perform a brazing heat treatment in a furnace at about 600 ° C. for joining members, and the organic paint is decomposed during the brazing heat treatment, so that sufficient aluminum fins can be obtained. There is a problem that hydrophilicity cannot be imparted.

  Therefore, in order to surely form an organic film in a heat exchanger having a brazing structure, a so-called post coat is used in which the heat exchanger after brazing is immersed in a hydrophilic resin liquid to form a hydrophilic film entirely. It is necessary to perform this process (see Patent Document 1), and a hydrophilic film can be formed by this post coating.

JP 2013-96631 A

However, in order to form a hydrophilic film on the fins by post-coating, it is necessary to perform a batch process of immersing the heat exchangers one by one in a hydrophilic treatment solution after brazing. In addition, there is also a problem that the waste of the hydrophilic resin liquid is wasteful and the waste liquid treatment is troublesome.
In view of these backgrounds, it is considered important that the aluminum fin can exhibit hydrophilicity even after brazing, and as a result of various studies on the state of flux residue on the fin surface, the present inventors have reached the present invention.

  In view of these backgrounds, the present invention is suitable for use in a heat exchanger having a structure in which an aluminum fin is brazed to an aluminum member such as an aluminum tube, and includes a fin having excellent hydrophilicity and the hydrophilic fin. It is intended to provide a heat exchanger.

  The hydrophilic fin of the present invention is a hydrophilic fin made of aluminum or an aluminum alloy joined by brazing using a brazing material and a fluoride-based flux, and has a surface formed by residual particles of the fluoride-based flux generated during brazing. The coating rate is 10% or more, and 500 to 2000 inorganic compound particles different from the residual particles of the flux are present per 1.0 mm square of the fin surface after the brazing heat treatment.

  In the hydrophilic fin of the present invention, it is preferable that the average particle diameter of the inorganic compound particles is 5 to 50 μm, and that the inorganic compound particles and the residual particles of the flux have irregularities formed on the fin surface.

In the hydrophilic fin of the present invention, it is preferable that the surface coverage of the flux with residual particles is 70% or more.
In the hydrophilic fin of the present invention, it is preferable that an area expansion ratio of a portion where the flux residual particles and the inorganic compound particles remain is in a range of 2 to 10 in a surface region of 200 μm square.

In the hydrophilic fin of the present invention, the fluoride-based flux may be K _1-3 AlF _4-6 , Cs _1-3 AlF _4-6 , Cs _0.02 K _1-2 AlF _4-5 , AlF ₃ , KF , KZnF ₃ , K ₂ SiF ₆ , and Li ₃ AlF ₆ .
In the hydrophilic fin of the present invention, it is preferable that the water contact angle on the fin surface after performing the dry-wet cycle test for 14 cycles after the brazing heat treatment is 40 ° or less.

In the hydrophilic fin of the present invention, the inorganic compound particles present on the surface of the aluminum fin are preferably one or two of an alumina monohydrate compound and a silica compound.
A heat exchanger according to the present invention is characterized in that the hydrophilic fin described in any of the above is brazed to a tube.

According to the present invention, fluoride flux residue particles derived from the fluoride flux used at the time of brazing are dispersed on the fin surface at a coverage of 10% or more, and inorganic compound particles different from the flux residue particles are further dispersed on the fin surface. Since 500 to 2,000 particles per 1.0 mm square are dispersed, the fins made of aluminum or an aluminum alloy are excellent in hydrophilicity and excellent in drainage of fins.
Therefore, if this hydrophilic fin is brazed to an aluminum member such as a tube to form a heat exchanger, the fin has excellent drainage properties, and condensed water or dew condensation water hardly adheres to the fin. An excellent heat exchanger can be provided.

It is a perspective view showing the heat exchanger of a 1st embodiment which brazed the hydrophilic fin concerning the present invention to a tube. FIG. 2 is a cross-sectional view of the heat exchanger shown in FIG. 1 taken along a plane orthogonal to a length direction of a tube. The figure which shows the longitudinal cross section of the tube before brazing in the same heat exchanger. The figure which shows the longitudinal section of the tube after brazing in the same heat exchanger. It is the front view which made a part of a 2nd embodiment of a heat exchanger obtained by brazing a hydrophilic fin concerning a tube to a tube into a section. FIG. 3 is a partially enlarged cross-sectional view showing a state where a header pipe, a tube, and a fin material are assembled and brazed in the same heat exchanger. FIG. 3 is a partially enlarged cross-sectional view showing a state in which a header pipe, a tube, and a fin material are assembled before brazing in the heat exchanger. The surface photograph which shows an example of the sample which covered the surface of the hydrophilic fin which concerns on this invention by 98% of surface coverage by the residual particle. 4 is an observation image showing an example of a result obtained by measuring the area magnification on the surface of the hydrophilic fin according to the present invention with a laser microscope. 5 is an SEM photograph showing a structure of a hydrophilic film surface of one example of a conventional sample. 5 is an SEM photograph showing the structure of the surface of the hydrophilic film for one example of the sample of the present invention. 5 is a graph showing a comparison between a water contact angle and a surface coverage of a conventional sample and a sample of the present invention.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
In addition, in the drawings used in the following description, in order to make the characteristics easy to understand, the characteristic portions may be enlarged for convenience, and the dimensional ratios and the like of the respective components are not necessarily the same as the actual ones. Absent.

FIG. 1 is a perspective view showing a heat exchanger of a first embodiment configured by brazing a hydrophilic fin and a tube according to the present invention.
The heat exchanger 11 of the present embodiment is used for a heat exchanger for an outdoor unit such as a room air conditioner or a package air conditioner, an outdoor unit for an HVAC (Heating Ventilating Air Conditioning), a heat exchanger for an automobile, and the like. All-aluminum heat exchanger used.

The heat exchanger 11 shown in FIG. 1 is composed of a pair of header pipes 14 which are spaced apart from each other on the left and right and are arranged in parallel with each other. And a plurality of fins 13 which are brazed to the outer surface of the tube 12 constituting the tube 22 and dissipate heat to the outside air.
One of the pair of header tubes 14 is provided with a supply tube 15 for supplying a refrigerant to the tube 22 via the header tube 14. The other header pipe 14 is provided with a recovery pipe 16 for recovering the refrigerant that has passed through the tube 22. The tube 22, the fins 13, the header tube 14, the supply tube 15, and the recovery tube 16 are made of aluminum or an aluminum alloy.

FIG. 2 is a sectional view of the heat exchanger 11 in which a partial section of the tube 22 is taken.
As shown in FIG. 2, a plurality (ten in the present embodiment) of refrigerant flow paths 12 </ b> D arranged in a line in the width direction are formed inside the flat tube body 12 constituting the tube 22.
Further, as shown in FIG. 2, a plurality of (eight in this embodiment) cutouts 19 corresponding to the cross-sectional shape of the tube 22 are intermittently formed in the fin 13 vertically. As shown in FIG. 2, the notches 19 are individually formed horizontally in a state where the fins 13 stand vertically when viewed from the side.

FIG. 3 is a view showing a longitudinal section of the tube 22 in the heat exchanger 11, and FIG. 3 shows a state before brazing.
As shown in FIG. 1, the fins 13 are individually arranged in a vertical direction, a plurality of fins 13 are arranged in parallel so as to be arranged in a horizontal direction, and a tube 22 is inserted into each cutout 19. . As shown in FIG. 1, the plurality of fins 13 are arranged in the length direction of the tube 22. The fin 13 has a bent portion 20 that is bent along the outer surface of the tube 22 at the inner peripheral edge of the cutout portion 19. The bent portion 20 is formed by, for example, burring.
The tube 22 and the fin 13 are fitted to the notch 19 of the fin 13 so as to skew the fins 13 arranged at regular intervals, and the connection between the tube 22 and the fin 13 is brazed. It is integrated into.

Hereinafter, main components of the heat exchanger 11 will be described in more detail.
<Fin>
As shown in FIG. 4, the fins 13 are formed by a plate-shaped substrate 3 made of aluminum or an aluminum alloy, and flux residues and inorganic compound particles on the first surface 3 a and the second surface 3 b of the substrate 3. And a hydrophilic layer 1a. The base material 3 constituting the fins 13 is made of, for example, a clad material in which a brazing material is clad and pressed on one or both sides of a plate-shaped core material made of aluminum or an aluminum alloy in a state before brazing.
<Substrate>
The substrate 3 is made of an aluminum alloy mainly composed of pure aluminum such as JIS1050 or JIS3003 aluminum. Further, the base material 3 may be made of an aluminum alloy obtained by adding about 0.5 to 3.0% by mass of Zn to a JIS3003 based aluminum alloy. Further, the base material 3 may have a surface subjected to a corrosion-resistant base treatment.

<Tube>
As shown in FIG. 4, the tube 22 after brazing has a tube 12 and a sacrificial anticorrosion layer 15 </ b> A formed on the upper surface 12 a and the lower surface 12 b of the tube 12. As shown in FIG. 2, the tube 12 is a flat multi-hole tube in which a plurality of refrigerant channels 12 </ b> D are formed, and has end surfaces 12 c at both ends in the width direction of the tube 12. At the position where the sacrificial anticorrosion layer 15A is formed in the heat exchanger 11, a Zn sprayed layer 15B is formed in a state of the heat exchanger before brazing in which the fins 13 and the tube 22 are assembled (see FIG. 3). At the time of brazing, Zn of the Zn sprayed layer 15B diffuses from the outer surface side (the upper surface 12a side and the lower surface 12b side) to the inner surface side of the tube 22, and the sacrificial anticorrosion layer 15A is formed.
The tube body 12 is made of pure aluminum such as JIS1050 or an alloy mainly composed of JIS3003, JIS3102 or Al-Cu aluminum alloy, and is manufactured by extruding the above aluminum alloy.

<Flux layer>
K _1-3 AlF _4-6 and Cs _1-3 AlF ₄ are applied to the front and back surfaces of the tube 22 before brazing and the outer surfaces of the fins 13 or the entire heat exchanger before brazing in which the fin 13 and the tube 22 are assembled. _-6 , Cs _0.02 K _1-2 AlF _4-5 , AlF ₃ , KF, KZnF ₃ , K ₂ SiF ₆ , Li ₃ AlF ₆ , a fluoride-based flux layer composed of one or more of them. 1 is applied. The flux layer 1 is formed by, for example, spray-coating the flux on the entire outer surface of the heat exchanger before brazing in which the fins 13 and the tube 22 are assembled. In addition, a plurality of inorganic compound particles described below are added to the flux layer 1. The inorganic compound particles will be described later in detail.

<Hydrophilic film>
When brazing the tube 22 and the fins 13, the flux layer 1 melts when heated to about 550 ° C. during brazing heat treatment, crystallizes in a cooling process after brazing, and forms a residue.
For this reason, on the front and back surfaces (outer surfaces) of the tube 22 and the fins 13, as shown in the surface photograph of FIG. As shown in FIG. 4, a hydrophilic layer 1a in which the inorganic compound particles 1d added to the fluoride-based flux are dispersed is dispersed.
The hydrophilic layer 1a has a structure in which the residual particles 1c of the fluoride-based flux cover 10% or more, and more preferably 70% or more, of the tube 22 and the fins 13 in a range of 200 μm square on the front and back surfaces (outer surfaces).
In FIG. 4, the hydrophilic layer 1a is depicted as a one-layer film in order to make it easier to see. However, as shown in an enlarged manner in FIG. 11, a plurality of fluoride flux residue particles 1c and inorganic compound particles 1d are shown. Are mixed and dispersed. For the coverage of 10% and 70%, the surface is observed, and a plurality of ranges of 200 μm square (200 μm square) are defined, and the coverage is measured in each range.
The flux layer 20a applied to the surface on the tube 22 side at the bent portion 20 before brazing also remains partially as a hydrophilic film 20b after brazing.

As an example of a method of obtaining the coverage, the surface of the sample is observed by EPMA, Al element mapping is performed, binarization is performed based on the Al count threshold, and the Al base area is calculated. You can ask. The threshold value of the Al count number can be applied by obtaining the count number at which the Al base can be approximately extracted while observing the SEM observation result of the surface.
The area enlargement ratio can be obtained by observing a sample in a visual field of about 200 μm square with a laser microscope, and calculating the ratio of “surface area” to “observation field area” (area enlargement ratio = surface area / observation field area). The observation visual field for obtaining the area magnification can be arbitrarily selected on the flux residue. Since 3D measurement is possible with a laser microscope, the surface area (area in consideration of height) can be obtained from the above relationship.
As the laser microscope, for example, LASER MICROSCOPE VK-X100 (observation lens: × 100) from KEYENCE can be used.
It is necessary to perform the following pretreatment before observing a sample with a laser microscope. The flux residue is translucent and transmits laser light as it is. For this reason, before observing the flux residue, the flux residue can be colored by means of gold deposition, and can be observed with a laser microscope after coloring.

When the fluoride-based flux is heated to the brazing temperature, the resin component evaporates during the heating, but the fluoride-based flux melts once, crystallizes and remains on cooling, and remains as residual particles 1c on the outer surface of the fin 13. Remains. Further, the inorganic compound particles 1d remain as they are. Thus, the hydrophilic layer 1a is generated.
FIG. 8 shows a laser microscope photograph of a hydrophilic film having a surface coverage of 98% of the fins 13 obtained in an example described later. In the photograph of FIG. 8, the region where the residual particles 1c are not drawn on the surface of the fin 13 is not necessarily free of the residual particles 1c. This region is a region where the base of the aluminum alloy constituting the fin 13 can be confirmed by electron microscopic observation even if some fine residual particles less than 3 μm are present, and this region is drawn as a region without the residual particles 1c. ing. Therefore, if the ratio of the residual particles 1c of the fluoride-based flux having an equivalent circle diameter of 3 to 10 μm covering the surface of the fin 13 is 10% or more, more preferably 70% or more, it is a desirable range in the present invention.
If the surface coverage is less than 10%, the fin contact angle after brazing increases, and good hydrophilicity cannot be obtained.

Further, it is preferable that 500 to 2,000 inorganic compound particles 1d are present on the surface of the fin 13 after the brazing heat treatment per 1.0 mm square (1.0 mm square).
When the number of inorganic compound particles 1d existing on the surface of the fin 13 is less than 500 per 1.0 mm square, the fin contact angle after brazing increases, and desired hydrophilicity cannot be obtained. When the number of inorganic compound particles 1d existing on the surface of the fin 13 exceeds 2,000 per 1.0 mm square, brazing is hindered, and it becomes difficult to obtain a good bonding state.
It is desirable to use alumina monohydrate compound particles (boehmite particles) or silica compound particles (silicon dioxide particles) as the inorganic compound particles 1d, or composite particles obtained by mixing these.
In addition, as the inorganic compound particles 1d, alumina compound particles (aluminum oxide) or aluminum hydroxide compound particles can be used.

The atmosphere for brazing the fins 13 and the tube 22 is preferably in an inert gas atmosphere, and is preferably performed in a low oxygen state. For example, the fin 13 and the tube 22 are assembled in a heat exchanger type, and after applying a mixed solution of the fluoride-based flux and the inorganic compound particles, the mixture is transferred to a brazing heating furnace filled with nitrogen gas and heated to a temperature of about 600 ° C. When brazing by heating, it is preferable to fill the heating furnace with nitrogen gas and adjust the atmosphere in the heating furnace to an oxygen concentration of 10 ppm or less. The lower the oxygen concentration, the better the brazing properties in brazing. Adjustment of the coverage by the residual particles 1c can be realized by adjusting the application amount of the fluoride-based flux. Further, as an example of the case where KAlF ₄ is used as the fluoride-based flux, when the oxygen concentration at the time of brazing is set to about 100 ppm, the residue form of the flux tends to be petal-like. It tends to be scaly, and at about 50 ppm, it tends to be a mixture of scaly and petal. The coverage by the inorganic compound particles 1d can be adjusted by adjusting the coating amount of the inorganic compound particles.

In the present embodiment, the numerical value of the surface area expansion rate of the fin 13 due to the presence of the residual particles 1c and the inorganic compound particles 1d is also important, and the surface area expansion rate is more preferably in the range of 2.0 to 10.
When the area expansion ratio is less than 2.0, the fin contact angle after brazing increases, and the possibility that good hydrophilicity cannot be obtained increases. When the area enlargement ratio exceeds 10.0, brazing is hindered, and it becomes difficult to obtain a good joining state.

  As described above, the residual particles 1c of the fluoride-based flux and the inorganic compound particles 1d are dispersed on the surface, the surface coverage of the residual particles 1c of the fluoride-based flux is 10% or more, and the inorganic compound particles 1d are dispersed. If the fin 13 has 500 to 2,000 hydrophilic layers 1a per square of 1.0 mm, the fin 13 is excellent in hydrophilicity. For this reason, if the heat exchanger 11 has the fins 13 and has the brazing structure shown in FIG. It is possible to provide the heat exchanger 11 that has a low possibility of retaining water by water or dew condensation water and has a low risk of reducing heat exchange performance.

  In addition, since the hydrophilic film 13 of the present embodiment disperses the inorganic compound particles 1d in addition to the residual particles 1c to form a plurality of fine irregularities on the surface, the surface area can be increased, and the residual particles can be increased. It is possible to obtain better hydrophilicity than the hydrophilic film of only 1c. For this reason, the hydrophilic film 13 of the present embodiment exhibits more excellent hydrophilicity even if the surface coverage is lower than that of the hydrophilic film including only the residual particles 1c.

FIG. 5 is a front view in which a part of the heat exchanger 30 according to the second embodiment including corrugated fins is sectioned.
The heat exchanger 30 of the second embodiment is used for heat exchangers for automobiles, heat exchangers for indoor / outdoor units of room air conditioners, or outdoor units for HVAC (Heating Ventilating Air Conditioning). All-aluminum heat exchanger used.
The heat exchanger 30 is composed of header pipes 31 and 32 erected in parallel at a distance from each other on the left and right sides, and the header pipes 31 and 32 are spaced apart from each other in parallel and parallel to each other. , 32 and a plurality of flat tubes 33 joined at right angles to each other, and corrugated fins (corrugated fins) 34 attached to each tube 33. The header pipes 31, 32, the tube 33 and the fins 34 are made of aluminum or an aluminum alloy.

  A plurality of slits 36 are formed on the opposing side surfaces of the header pipes 31 and 32 at regular intervals in the longitudinal direction of each pipe, and the ends of the tube 33 are inserted through the opposing slits 36 of the header pipes 31 and 32. A tube 33 is provided between the header pipes 31 and 32. In addition, fins 34 are arranged between a plurality of tubes 33, 33 laid at predetermined intervals between the header pipes 31, 32, and these fins 34 are brazed to the front side or the back side of the tube 33.

As shown in FIG. 6, a first fillet portion 38 is formed by a brazing material at a portion where the end of the tube 33 is inserted into the slit 36 of the header pipes 31 and 32, and the tube 33 is formed with respect to the header pipes 31 and 32. Be brazed. In the corrugated fin 34, the second fillet portion 39 is formed by the brazing material generated at a portion between the top of the wave and the front or back surface of the adjacent tube 33, and the surface of the tube 33 is formed. Corrugated fins 34 are brazed to the side and the back side.
The fin 34 has a plate-shaped base material 34a made of aluminum or an aluminum alloy, and a hydrophilic layer 35a attached to the entire surface (front surface, back surface, and both side surfaces) of the base material 34a.

  In the heat exchanger 30 of the present embodiment, as shown in FIG. 7, a heat exchanger assembly 41 is formed by assembling header pipes 31, 32, a plurality of tubes 33 and a plurality of fins 34 provided therebetween. , Produced by heating and brazing. Note that a Zn melt diffusion layer (sacrificial anode layer) 42 is formed on the front side and the back side of the tube 33 by heating during brazing.

Hereinafter, main components of the heat exchanger 30 will be described in more detail.
<Fin base material>
The base material 34a of the fin 34 is made of a pure aluminum-based material such as JIS1050 or an alloy mainly composed of JIS3003-based aluminum alloy. In addition, the base material 34a may be made of an aluminum alloy obtained by adding about 2% by mass of Zn to a JIS3003 aluminum alloy.

The base material 34 a of the fin 34 is preferably made of a material having a pitting potential lower than that of the tube 33. Pitting due to the corrosion of the tube 33 may lead to leakage of the refrigerant. By setting the pitting potential of the base material 34a in the fins 34 to be lower than the pitting potential of the tube 33, it is possible to delay that the base material 34a of the fins 34 is preferentially corroded and pitting occurs in the tube 33. .
The base material 34a is processed by smelting the aluminum alloy by an ordinary method and passing through a hot rolling step, a cold rolling step, a pressing step, and the like. In addition, the manufacturing method of the base material 34a is not particularly limited in the present invention, and a known manufacturing method can be appropriately adopted.

On both surfaces of the hydrophilic fin 34, a hydrophilic layer 35a including the residue particles 1c and the inorganic compound particles 1d described in the above embodiment is formed.
The corrugated hydrophilic fin 34 is brazed to the tube 33 with a brazing material at the vertex position closest to the tube 33.

The hydrophilic fin 34 of the present embodiment has a base material equivalent to the hydrophilic fin 13 of the first embodiment, and a hydrophilic layer 35a equivalent to the hydrophilic layer 1a of the previous embodiment on both front and back surfaces of the base material. Are formed. This hydrophilic layer 35a contains residue particles and inorganic compound particles as in the previous hydrophilic layer 1a.
For this reason, the hydrophilic fins 34 of the present embodiment also have excellent drainage properties, and have a feature that water droplets are not retained in gaps between the fins even when the fin spacing is small.
For this reason, even if the fins 34 are arranged adjacently at a plurality of intervals at short intervals, there is a low possibility of retaining water due to coagulated water or dew condensation between the fins 34, and there is little possibility that heat exchange performance is reduced. An exchanger 30 can be provided.

<< Preparation of sample >>
An aluminum alloy for tubes containing 0.3% by mass to 0.5% by mass of Si and 0.2% by mass to 0.4% by mass of Mn and consisting of Al and unavoidable impurities, and is cross-sectionally cut from this alloy A flat multi-hole tube (10 holes) made of an aluminum alloy for a heat exchanger having a shape (wall thickness 0.26 mm × width 17.0 mm × overall thickness 1.5 mm) was formed. Further, a surface of the multi-hole tube was sprayed with Zn to prepare a multi-hole tube coated with zinc.
It contains 0.4% by mass to 0.6% by mass of Si, 1.0% by mass to 2.0% by mass of Mn, and 0.5% by mass to 3.0% by mass of Zn, and the balance consists of unavoidable impurities and Al. A clad fin material was prepared in which a base material was used as a core material and a brazing material layer (JIS 4045 alloy layer) was disposed on one side.

Next, a heat exchanger having the structure shown in FIG. 1 was assembled from the six tubes and the 50 fins to form a temporary mini-core test body, and a flux (inorganic compound) of the type described below with a coating amount described later on the surface of the mini-core test body (Containing particles), and brazing was performed under the condition that these test pieces were kept in a heating furnace in a nitrogen atmosphere at 600 ° C. for 3 minutes. The nitrogen atmosphere of the heating furnace was adjusted to a nitrogen atmosphere having an oxygen concentration of 10 ppm. The fins were provided with six slit-shaped grooves capable of accommodating tubes, and 50 fins were stacked at intervals of 1 to 2 mm.
By this brazing, a sacrificial anticorrosion layer was formed on the front and back surfaces of the tube on which the Zn sprayed coating was formed, and the fins were brazed. These were used as heat exchanger test specimens.
Further, on the front and back surfaces of the fins of the heat exchanger test body, a hydrophilic layer in which residue particles of the fluoride-based flux and inorganic compound particles were dispersed was formed by heating and melting the flux layer at 600 ° C.
Each of the heat exchanger test specimens was subjected to each test described later.

When assembling the mini-core test specimen, a plurality of test specimens were assembled by setting the flux application amount to 0.5 to 10 g / m ² , and each was subjected to the following tests. The type of flux used was any of KAlF ₄ + K ₃ AlF ₆ , CsAlF ₄ , KZnF ₃ , K ₂ SiF ₆ , and Li ₃ AlF ₆ as described in the table below.

<Surface coverage>
After EPMA (electron beam microanalysis), elemental mapping of Al is performed on the surface of the sample after the brazing heat treatment, the image is binarized based on the threshold value of the Al count number, and the Al base area is calculated. The surface coverage of the flux residue particles and the inorganic compound particles was calculated. The threshold value of the Al count number was applied by obtaining the count number from which an Al substrate could be approximately extracted based on an observation image of the sample surface with a scanning electron microscope (SEM).
<Residual particle measurement>
Regarding the residual particles of the fluoride-based flux formed on the front and back surfaces of the fins, the elemental mapping of Al on the observation surface was performed by EPMA, and the Al base area was calculated by binarization based on the threshold value of the Al count number. Thereafter, the coverage was determined. The threshold value of the Al count number was applied by obtaining the count number at which the Al base can be approximately extracted while observing the SEM observation results.

<Particle number measurement>
Flux residue particles and inorganic compounds are obtained by EPMA (Electron Beam Micro-Analysis) by binarizing the image of the sample after the brazing heat treatment based on the threshold value of the F count number in a field of view of 1.0 mm square. The particles were separated. The size and number of the inorganic compound particles other than the flux residue were measured by performing image analysis on this.

<Area expansion rate>
The area enlargement ratio is determined by observing a sample in a 200 μm square (200 μm square) visual field with a laser microscope, and the ratio of “surface area after brazing heat treatment” to “observation visual field area” (area enlargement ratio = after brazing heat treatment). Surface area / observation visual field area). The observation visual field for obtaining the area magnification can be arbitrarily selected on the flux residue.
Since 3D measurement is possible with a laser microscope, the surface area (area in consideration of height) can be obtained from the above relationship. For example, LASER MICROSCOPE VK-X100 (observation lens: x100) can be used as the laser microscope. It is necessary to perform the following pretreatment before observing a sample with a laser microscope. The flux residue is translucent and transmits laser light as it is. For this reason, the flux residue was colored by gold vapor deposition before observation, and observed with a laser microscope after coloring.

[Hydrophilicity: water contact angle after dry-wet cycle test]
The process of immersing the brazed sample in running water for 8 hours and then drying for 16 hours was defined as one cycle, and the water contact angle of the fin surface after 14 cycles was measured. At this time, a sample having a water contact angle of 41 ° or more was evaluated as ×, a sample at 40 ° to 21 ° as Δ, a sample at 20 to 11 ° as ○, a sample at 10 ° or less as ◎, and the hydrophilicity was evaluated. .

[Brazing property: Fin joining rate evaluation test]
The flat multi-hole tube was combined with a clad fin to which a brazing material was bonded, and a brazing heat treatment was performed at a temperature of 600 ° C. for 3 minutes to prepare a test body in which the tube and the fin were brazed and joined.
For each of the brazed fins, the fins were peeled off from the tube, and the fin joint traces remaining on the tube surface were observed. Then, the number of unjoined portions (portions where brazing was performed but no trace of the joined portion remained) was counted. One specimen was observed at 100 locations, and samples having normal joints of 69 or less were evaluated as ×, samples at 70-79 as Δ, samples at 80-89 as ○, 90 as samples. More than one sample was marked with 表 記 to determine the brazing property.

In Table 1 below, the type of the used flux, the applied amount, the form of the residue after brazing, the number of the inorganic compound particles (pieces / mm ² ), the surface coverage (%: flux coverage), and the area The measurement results of the enlargement ratio (%), water contact angle (°), and brazing property are described.

From the results shown in Table 1, it is a hydrophilic film containing flux residual particles, has a surface coverage of 10% or more, and has 500 to 2,000 inorganic compound particles / mm ² having an average particle size of 5 to 50 μm, If the sample has an area expansion ratio of 2.0 to 10.0, the heat exchanger has an excellent hydrophilicity showing an excellent water contact angle of 40 ° or less after a dry-wet cycle test, and also has an excellent brazing property. Could be provided.
Therefore, it can be seen that a suitable hydrophilic film can be formed using the flux residue after brazing.

In addition, the same tendency was shown for any flux species of KAlF ₄ + K ₃ AlF ₆ , CsAlF ₄ , KZnF ₃ , K ₂ SiF ₆ , and Li ₃ AlF ₆ .

The sample of No. 28 (Comparative Example) has a small number of inorganic compound particles of 200 particles / mm ^2, which is a small example. However, the water contact angle is poor, and the sample of No. 29 (Comparative Example) is inorganic. The number of compound particles was 2500 particles / mm ² , which was too large, but the brazing property was reduced.
Although the sample of No. 30 (comparative example) was a sample having a low surface coverage, the water contact angle was slightly deteriorated, and the brazing property was lowered.
The sample No. 31 (Comparative Example) is a sample having a low area enlargement ratio, but the water contact angle is deteriorated, and the sample No. 32 (Comparative Example) is a sample having an excessively large area enlargement ratio. , The brazing property was reduced.
The sample of No. 33 (Comparative Example) was a sample in which the number of inorganic compound particles was 2500 / mm ² , the number of inorganic compound particles was too large, the surface coverage was low, and the area expansion ratio was too large. In addition, the water contact angle became worse, and the brazing property also deteriorated.

    FIG. 9 shows an example of an observation image obtained by measuring the area enlargement ratio of the sample No. 4 shown in Table 1 with a laser microscope. The example of FIG. 9 is an example in which the area enlargement ratio was measured as 3.8.

FIG. 10 shows a surface texture photograph of the No. 1 comparative example sample shown in Table 1, and FIG. 11 shows a surface texture photograph of the No. 5 example sample shown in Table 1.
In the structure shown in FIG. 11, a plurality of fine irregularities are formed on the surface by having a structure in which residue particles 1c due to the flux residue and inorganic compound particles 1d are dispersed. It can be estimated that excellent hydrophilicity is exhibited by the presence of the fine irregularities.

FIG. 12 shows the relationship between the water contact angle and the surface coverage of the samples of Examples Nos. 13, 16, and 17 shown in Table 1, and the water of Comparative Examples of Samples Nos. 28, 29, and 31 shown in Table 1. It is a graph which shows the relationship between a contact angle and a surface coverage in comparison.
As is clear from the comparison shown in FIG. 12, if the sample was the example of the present application, a more excellent water contact angle could be obtained even if the sample had a lower surface coverage than the sample of the comparative example. .
Therefore, a fin having a hydrophilic film according to the present invention provides a heat exchanger having a high drainage fin having an excellent drainage property and preventing water droplets and the like from closing a gap between the fins. it can.

  INDUSTRIAL APPLICABILITY The hydrophilic fin of the present invention can be applied to a brazing type all-aluminum heat exchanger, and can provide a heat exchanger having good drainage properties on the fin surface.

  DESCRIPTION OF SYMBOLS 1 ... Flux layer, 1a ... Hydrophilic layer, 1c ... Residual particle, 1d ... Inorganic compound particle, 3 ... Base material, 3a ... 1st surface, 3b ... 2nd surface, 5A ... Sacrificial anticorrosion layer, 11 ... Heat exchange Container, 12: pipe, 12a: upper surface, 12b: lower surface, 12c: end side surface, 12D: refrigerant channel, 13: fin, 14: header tube, 15: supply tube, 15A: sacrificial anticorrosion layer, 15B: brazing material Layer 16: Recovery tube, 22: Tube, 30: Heat exchanger, 31, 32: Header pipe, 33: Tube 33, 34: Fin (corrugated fin), 34a: Base material, 35a: Hydrophilic layer.

Claims (8)

  A hydrophilic fin made of aluminum or an aluminum alloy joined by brazing using a brazing material and a fluoride-based flux, wherein the surface coverage of the fluoride-based flux generated during brazing with residual particles is 10% or more. And hydrophilic inorganic fins, wherein 500 to 2000 inorganic compound particles different from the residual particles of the flux are present per 1.0 mm square of the fin surface after the brazing heat treatment.   2. The hydrophilic fin according to claim 1, wherein the inorganic compound particles have an average particle size of 5 to 50 μm, and the inorganic compound particles and the residual particles of the flux form irregularities on the fin surface. 3. .   The hydrophilic fin according to claim 1 or 2, wherein a surface coverage of the flux with residual particles is 70% or more.   4. The method according to claim 1, wherein an area expansion ratio of a portion where the residual particles of the flux and the inorganic compound particles remain is in a range of 2 to 10 in a 200 μm square surface region. 5. The hydrophilic fin according to the above. The fluoride-based flux is K _1-3 AlF _4-6 , Cs _1-3 AlF _4-6 , Cs _0.02 K _1-2 AlF _4-5 , AlF ₃ , KF, KZnF ₃ , K ₂ SiF _6. 5. The hydrophilic fin according to claim 1, comprising one or more of Li ₃ AlF _{6. 6} .   The hydrophilic contact according to any one of claims 1 to 5, wherein a water contact angle of the fin surface after performing a dry / wet cycle test for 14 cycles after brazing heat treatment is 40 ° or less. Sex fins.   The hydrophilic compound according to any one of claims 1 to 6, wherein the inorganic compound particles present on the fin surface are one or two of an alumina monohydrate compound and a silica compound. fin.   A heat exchanger in which the hydrophilic fin according to any one of claims 1 to 7 is brazed to a tube.