JP2003010964A - Brazing method for aluminum heat exchanger and aluminum member brazing solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the efficiency of Zn adhesion and the workability of Zn adhesion, and retard the rise of viscosity caused by gelation of a solution by coating Zn on the surface of an aluminum member simultaneously with a flux component, in a brazing method for an aluminum heat exchanger. SOLUTION: At least on one surface of a plurality of aluminum members 2 to be brazed, a solution containing a binder having the flux component, Zn and a carboxyl radical, and reaction retarder retarding the reaction of the Zn and the carboxyl radial is coated to perform the brazing between a plurality of the aluminum members, so as to form a Zn diffusion layer on the surface of the aluminum member coated with the solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazing method for an aluminum heat exchanger for improving corrosion resistance by a sacrificial corrosion effect of a diffusion layer of Zn (zinc), and an aluminum member brazing solution. It is suitable for use in a brazing method for a condenser of a vehicle air conditioner.

[0002]

2. Description of the Related Art Conventionally, in an aluminum heat exchanger for a vehicle, weight reduction has been required for the purpose of improving fuel efficiency of a vehicle engine. In order to meet this demand, it is necessary to reduce the thickness of constituent materials such as tubes of heat exchangers. However, as the material becomes thinner, the period until fluid (refrigerant) leakage due to pitting corrosion of the aluminum material becomes shorter, so it is an important issue to achieve both material thinning and corrosion resistance compatibility. Become.

In a condenser of a vehicle air conditioner, a tube forming a passage through which a refrigerant flows is usually formed by extruding an aluminum material into a flat multi-hole cross section. In this flat multi-hole tube, the Zn diffusion layer is formed on the outer peripheral surface by Zn spraying to improve the corrosion resistance. This Zn diffusion layer has a base electric potential lower than that of the aluminum material forming the tube, which causes the Zn diffusion layer to preferentially corrode (sacrificial corrosion) than the aluminum material, thereby preventing perforation corrosion of the aluminum tube. I try to prevent it.

[0004]

However, in the above-mentioned prior art, since Zn is deposited by thermal spraying on the outer surface of the tube, it is practically difficult to control the Zn deposition amount to a small amount. As a result, high-concentration Zn also exists in the brazed portion between the tube and the corrugated fin, and the brazed portion is likely to be selectively corroded, so that the corrugated fin is likely to drop off.

Further, since the efficiency of Zn deposition on the aluminum surface is very low (about 20%), the thermal spraying process of Zn is a factor that increases the manufacturing cost of the aluminum heat exchanger. Furthermore, since the tube is formed by extruding an aluminum material, a clad material in which a brazing material is clad cannot be used as the tube material. Therefore, it is necessary to use a clad material in which a brazing material is clad as the corrugated fin, which leads to an increase in cost.

Recently, in US Pat. No. 5100048, a non-corrosive flux (nocolok flux) is used.
A flux solution in which Si powder and a binder are mixed is applied to the surface of the aluminum member, and Si reacts with aluminum by heating during brazing to form a eutectic composition having a lower melting point than aluminum. A brazing method for brazing between members has been proposed. According to the above brazing method, an aluminum bare material which is not clad with a brazing material can be used as the fin material, and the cost of the aluminum heat exchanger can be reduced.

Also in the above brazing method, if the Zn diffusion layer is formed on the outer surface of the tube by Zn spraying, the corrosion resistance can be improved, but the above problems due to Zn spraying (decrease in Zn adhesion efficiency, etc.) occur.

Therefore, the present inventors mixed Zn powder into the flux solution in the above brazing method, and applied Zn to the aluminum member (tube) surface at the same time as the flux component and Si powder to braze the aluminum members. I examined the brazing method.

However, when this brazing method is actually tried, Zn reacts with the binder component of the flux to cause gelation, the viscosity of the flux solution increases, and the flux solution is applied to the aluminum member. It turned out to be difficult. Here, the binder is specifically an acrylic resin having a carboxyl group, and this carboxyl group reacts with Zn as shown in the following chemical formula 1 to cause gelation of the flux solution.

[0010]

Embedded image Zn ²⁺ + 2COO ⁻ → polymer-COO
-Zn-OCO-polymer (gel) In addition, the carboxyl group of the binder is used for shaping the tube after applying the flux solution, for ensuring oil resistance to the processing oil used in the cutting step, and for easily applying water after application of the solution. It is necessary to be able to wash. In view of the above points, the present invention applies Zn to the surface of an aluminum member at the same time as a flux component to improve the efficiency of Zn adhesion and the workability of Zn adhesion. The purpose is to suppress an increase in viscosity due to aging.

[0011]

Means for Solving the Problems The present invention has been devised based on the results of the following studies to achieve the above object.

The present inventors first examined the use of Zn fluoride instead of Zn powder. This is because a stable metal compound called Zn fluoride is used rather than Zn powder (that is, powder of Zn metal alone) to suppress the production of Zn ²⁺ . The Zn fluoride component is specifically KZnF ₃ , and KF / ZnF ₂ = 45/55 to 50/50 (wt.
%). Fluoride is selected because it has a low corrosive effect on metals.

Zn fluoride: flux: Si =
Mix 1: 1: 1 (weight ratio) to the
Acrylic resin binder with a base is mixed and the solvent
Diluted with (eg IPA: isopropyl alcohol)
A solution (coating solution) was prepared. The flux is fluoride
It is a non-corrosive flux (Nocolock flux) of the system
Specifically, KAlF_Four , Or KAlF_FourAnd K₃
AlF₆Mixture with (molar ratio of KAlF_Four: For 90
Then K₃AlF₆: 10) or K₂AlF _FiveEtc.
To use.

The viscosity of the above solution is measured according to JIS K1603.
When measured by the measuring method described in (5.2), as shown in FIG. 7A, the viscosity of the solution was 10,000 mPa · s / 2 in a very short period of about 3 days after the solution was prepared.
It was found that the temperature increased to a high value near 5 ° C. and could not be put to practical use. It is considered that this is because even if Zn fluoride is used, Zn ionization eventually occurs as in the following chemical formula 2 and gelation of the solution occurs.

[0015]

[Image Omitted] KF · ZnF ₂ + 3H ₂ O → Zn (OH) ₂ + K
OH + 3HF Then, the present inventors next examined the binder. That is, in the acrylic resin that constitutes the binder, the carboxyl group necessary for oil resistance and water-solubility reacts with Zn to cause gelation of the solution, so that the reaction suppression that suppresses the reaction between the carboxyl group and Zn is suppressed. The addition of agents was considered. Specifically, dimethylaminoethanol was used as the reaction inhibitor.

2 wt% of this dimethylaminoethanol was added to the solid content of the solution, and the change in viscosity of the solution to which this reaction inhibitor was added was measured. Here, the solution is Zn described above.
Fluoride: flux: Si = 1: 1: 1 (weight ratio), mixed with a binder of an acrylic resin having a carboxyl group, and diluted with a solvent (the above IPA). The solid content of the solution is the total solid content of Zn fluoride, flux, Si and binder composition.

When the change in viscosity of the solution to which the reaction inhibitor was added was measured, the viscosity of the solution was 1000 mPa · s / 25 even after 60 days, as shown by the characteristic B in FIG.
It was found that the value can be suppressed to a value below ℃.

The viscosity value after the lapse of 60 days is Z
The viscosity change characteristic C of an ordinary flux solution (mixing a flux component and a binder and diluting it with a solvent) which does not add reaction suppression with n-fluoride is slightly higher than that of the ordinary flux solution, and at a level that can be sufficiently put to practical use. is there.

When the amount of the reaction inhibitor added is reduced, the effect of inhibiting the reaction between the carboxyl group and Zn decreases,
Since the effect of suppressing the viscosity also decreases, it is preferable that the addition amount of the reaction inhibitor is 1 wt% or more with respect to the solid content component in the solution. Further, when the amount of the reaction inhibitor added is large, the effect of suppressing the viscosity is increased, but on the other hand, the odor becomes severe, which is not preferable for safety and hygiene. Therefore, the amount of the reaction inhibitor added is 5 wt% with respect to the solid component in the solution. % Or less is preferable. More preferably, the amount of the reaction inhibitor added is in the range of 1 to 3 wt% with respect to the solid component in the solution.

In addition to the above-mentioned dimethylaminoethanol, tertiary aminoalcohols such as diethylaminoethanol and secondary aminoalcohols such as methylaminoethanol and ethylaminoethanol are effective as reaction inhibitors. It is considered that these amino alcohols form an electronic interaction with the proton-dissociated carboxyl group because the nitrogen atoms in the molecules constituting them have an unpaired electron pair. Therefore, the reaction between ionized Zn ²⁺ and the carboxyl group can be suppressed.

Since Zn fluoride (KZnF ₃ ) itself has the elements (K, F) of the flux component and can fulfill the flux function, the above-mentioned Zn fluoride: flux is used to prepare the solution. : Si = 1: 1: 1
Instead of mixing at 1 (weight ratio), Zn fluoride: Si =
Even if the mixture of 2: 1 (weight ratio) is stopped and the mixing of the flux components alone is stopped, a solution having the same action can be prepared.

The present invention is based on the findings of the above-described experimental study. According to the invention of claim 1, in the brazing method for an aluminum heat exchanger, at least one of a plurality of aluminum members to be brazed is used. A solution containing a flux component, Zn, a binder having a carboxyl group, and a reaction inhibitor that suppresses the reaction between Zn and the carboxyl group is applied to the surface, brazing is performed between a plurality of aluminum members, and the solution is applied. A Zn diffusion layer is formed on the surface of the formed aluminum member.

According to this, by forming the Zn diffusion layer on the surface of the aluminum member, the sacrificial corrosion action is exerted and the corrosion resistance of the aluminum member can be improved. Moreover, in the present invention, Zn is applied at the same time as the application of the solution containing the flux component.
Can be attached to the surface of the aluminum member, and the workability of Zn attachment can be improved. In addition, since Zn is applied to the surface of the aluminum member at the same time as the solution, Zn is used in comparison with the thermal spraying method.
The adhesion efficiency can be greatly improved.

Further, Z is added to a solution containing a binder having a carboxyl group for ensuring oil resistance and water resistance.
Even when n is mixed, the reaction inhibitor that suppresses the reaction between Zn and the carboxyl group is mixed, so that the gelation of the solution can be prevented and the increase in the viscosity of the solution can be suppressed. Therefore, it is possible to prevent a situation in which the solution cannot be applied due to an increase in viscosity.

According to the invention described in claim 2, claim 1
In, the flux component and Zn can be mixed into the solution as Zn fluoride. By doing this, Z
Since it is made into a metal compound called n-fluoride and mixed into the solution,
Zn can be stabilized and a flux function can be exerted by the action of fluoride as compared with the case where Zn alone is mixed in a solution.

In the first aspect, the "solution containing the flux component and Zn" is not limited to the case of using the Zn fluoride as in the second aspect, and the flux component and Zn are independently mixed with the solution. Alternatively, the flux component and the Zn solution may be mixed in various manners, such as when the flux components are independently mixed and the Zn is mixed with the solution in the form of an Al-Si-Zn alloy as in claim 6 described later. You may mix in.

Further, as in the invention described in claim 3, in the method according to claim 1 or 2, Si is mixed in the solution,
During brazing, Si may react with the aluminum member to form a eutectic composition having a lower melting point than aluminum, and the eutectic composition may braze a plurality of aluminum members.

In particular, according to claim 3, the plurality of aluminum members can be brazed together without brazing the brazing material on the side of the plurality of aluminum members to be brazed. It can be molded with a simple aluminum bare material, which is extremely advantageous in cost reduction.

In the invention according to claim 4, in claim 3, one of the plurality of aluminum members is a multi-hole tube (14) and the other one of the plurality of aluminum members is a multi-hole tube (14). The corrugated fin (15) is brazed to the multi-hole tube (14) and the corrugated fin (1) by applying the solution to the multi-hole tube (14).
5) It is characterized by brazing between and.

According to this, aluminum and Si on the surface of the multi-hole tube (14) form a eutectic composition, and the space between the multi-hole tube (14) and the corrugated fin (15) can be brazed. Not only the hole tube (14)
The corrugated fins (15) can also be molded with a bare material that is not clad with a brazing material, which is advantageous for cost reduction and thinning (weight reduction) of the corrugated fins (15).

According to the invention described in claim 5, claim 1
Alternatively, the brazing material may be clad on at least one surface of the plurality of aluminum members, and the plurality of aluminum members may be brazed with the brazing material interposed.

According to a sixth aspect of the invention, in the brazing method for an aluminum heat exchanger, Al- is formed on at least one surface of a plurality of aluminum members to be brazed.
A solution containing a Si-Zn alloy, a flux component, a binder having a carboxyl group, and a reaction inhibitor that suppresses the reaction between Zn and the carboxyl group is applied, brazing is performed between a plurality of aluminum members, and the solution is applied. A Zn diffusion layer is formed on the surface of the formed aluminum member.

With this, the same operational effect as that of the first aspect can be exhibited. In particular, since the Al-Si-Zn alloy itself contains the brazing filler metal component of Al-Si, it is easy to secure the amount of brazing filler metal.

In the invention according to claim 7, which is a solution applied to an aluminum member before brazing, a flux component, Zn, a binder having a carboxyl group, and a reaction between the Zn and the carboxyl group are suppressed. It is characterized in that it contains a reaction suppressor.

As a result, it is possible to provide a solution for brazing an aluminum member which exhibits the effects of the first aspect.

According to the invention described in claim 8, claim 7
In, the flux component and Zn may be mixed as Zn fluoride.

According to the invention described in claim 9, claim 7
Alternatively, if Si is contained in 8, it is possible to braze the aluminum members by forming a eutectic composition with aluminum on the surface of the aluminum members and Si.

According to the tenth aspect of the invention, the solution applied to the aluminum member before brazing is Al-
It is characterized by containing a Si-Zn alloy, a flux component, a binder having a carboxyl group, and a reaction inhibitor that suppresses the reaction between Zn and the carboxyl group.

As a result, it is possible to provide a solution for brazing an aluminum member, which exhibits the effects of the sixth aspect.

In this specification, the term "aluminum" is used to include an aluminum alloy. Further, the reference numerals in the parentheses of the above-mentioned means indicate the correspondence with the specific means described in the embodiments described later.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) First, before describing the brazing method according to the first embodiment, a vehicle air conditioner is used as an aluminum heat exchanger to which the brazing method of the first embodiment is applied. The outline of the condenser will be described with reference to FIGS. 1 and 2. The condenser 10 cools the high-temperature and high-pressure superheated gas refrigerant discharged from the compressor (compressor, not shown) in the refrigeration cycle of the vehicle air conditioner. And then condense it.

The condenser 10 has a pair of first and second header tanks 11 and 12 arranged at a predetermined interval.
The first and second header tanks 11 and 12 have a shape extending in a substantially cylindrical shape in the vertical direction. A core portion 13 for heat exchange is arranged between the first and second header tanks 11 and 12.

The condenser 10 of the present embodiment is generally called a multi-flow type, and the core portion 13 has a flattened state in which the refrigerant flows horizontally between the first and second header tanks 11 and 12. A large number of tube-shaped tubes 14 are arranged in parallel in the vertical direction, and fins 15 are interposed between the large number of tubes 14 to join them. Here, the tube 14 is an extruded multi-hole flat tube in which a large number of refrigerant passage holes 14a are formed by extruding aluminum as shown in FIG. Further, the fin 15 is a corrugated fin that is bent in a wavy shape.

One end of the tube 14 communicates with the first header tank 11 and the other end communicates with the second header tank 12. A refrigerant inlet side pipe joint (refrigerant inlet portion) 16 is arranged and joined to the upper side of the second header tank 12. Further, a refrigerant outlet side piping joint (refrigerant outlet portion) 17 is arranged and joined to the lower side of the second header tank 12.

Further, in this example, one separator 1 is provided in the second header tank 12 at a portion between the inlet side pipe joint 16 and the outlet side pipe joint 17.
By arranging 8, the inside of the second header tank 12 is partitioned vertically into two spaces 12a and 12b.

As a result, after the refrigerant from the inlet side pipe joint 16 flows into the upper half tube 14 of the core portion 13 through the upper space 12a of the second header tank 12, the refrigerant in the first header tank 11 becomes U. It is turned to flow into the tube 14 in the lower half of the core portion 13, and then the refrigerant flows to the outlet side pipe joint 17 through the lower space 12b of the second header tank 12.

On the upper and lower sides of the heat exchanging core portion 13, side plates 19 and 20 having a U-shaped cross section are arranged. The side plates 19 and 20 are the outermost corrugated fins 15 and the first and the first corrugated fins. 2 header tank 11,
It is joined to 12, and plays the role of a mounting member for the vehicle body side of the condenser 10.

The first and second header tanks 11 and 12 have basically the same structure, and the first concave members 110 and 120 are the same.
And the second concave members 111 and 121 are joined together to form a substantially cylindrical hollow tank shape. First, second
Disc-shaped cap members 112 and 122 are joined to the upper and lower ends of the header tanks 11 and 12, respectively, to close the upper and lower openings of the first and second header tanks 11 and 12.

The first and second concave members 110, 120, 1
11 and 121 are press-formed aluminum plates, and the flat tube insertion holes (not shown) formed in the first concave members 110 and 120 are used to insert the tube 1 into the tube 1.
The end of No. 4 is inserted.

By the way, in the condenser, the tube 14 is extruded (or drawn) into a multi-hole shape having a flat cross section as shown in FIG. 2, and its specific material is a brazing material clad. It is made of a bare aluminum material, for example, 0.45 wt% Cu-0.15
wt% Mn-the balance is Al. The surface of the extruded multi-hole tube 14 is provided with a Zn fluoride-Si coating layer 14b, which will be described later, as shown in FIGS.

On the other hand, the fin 15 is also made of an aluminum bare material which is not clad with a brazing material, and specifically, for example, 0.15 wt% Cu-1.2 wt% Mn-2.5w.
t% Zn-balance Al.

Next, the brazing method (manufacturing method) of the heat exchanger of the first embodiment will be specifically described with reference to FIG. (1) Flux application process to component parts of heat exchanger and forming process of each part Preparation of tube coating liquid x and other component coating liquid y (tube coating liquid x) Tube coating liquid x is as follows: Is a solution prepared by mixing a reaction inhibitor with the solid content of and diluting it with a solvent.

Solid content of coating liquid Si: 30 wt%, Zn fluoride (KZnF ₃ ): 60 wt%, Binder: 10 wt
%.

As the binder, specifically, an acrylic resin made of a copolymer of methacrylic acid alkyl ester such as methyl methacrylate and isobutyl methacrylate and methacrylic acid is used. This binder is for uniformly adhering Si and Zn fluoride to the aluminum surface, and therefore has a certain degree of paint-like tackiness, and has a temperature lower than the brazing temperature (for example, 300 ° C.). It is preferable that it does not interfere with brazing by evaporating at about 450 ° C). The above acrylic resin satisfies these characteristics and, by having a carboxyl group, exhibits the above-mentioned oil resistance and water-repellent action.

The reaction inhibitor is dimethylaminoethanol, and is added at a ratio of 2 wt% with respect to the above solid content.

Solvent is isopropyl alcohol (IPA)
That is, the powdery solid content is uniformly dissolved in the solution. The ratio of the solvent is, for example, the above solid content: 5
Solvent: 48 wt% with respect to 2 wt%.

(Coating liquid y for other parts) The coating liquid y is
It is a solution prepared by diluting the following solids with a solvent, and does not contain a reaction inhibitor.

Coating liquid solid content Fluoride-based non-corrosive flux (specifically, KAlF ₄ ): 90 wt% and binder: 10 wt%. The binder is the same as the coating liquid x.

The solvent is also the same as the coating liquid x, and the mixing ratio with respect to the powdery solid content may be the same as that of the coating liquid x. FIG. 5 summarizes the compositions of both coating solutions x and y described above. However, the notation of the solvent is omitted.

Tube 14 The tube 14 is formed by extruding an aluminum bare material which is not clad with a brazing material.
As shown in FIG. 4, the extruded multi-hole tube a wound in a coil shape is unwound, and the coating solution x
Is applied by print transfer by a roll coater machine b, and then the coating liquid x on the tube surface is dried by blowing hot air or the like. At this time, Zn fluoride-extruded on the aluminum surface of the multi-hole tube a extruded by the action of the binder in the solution.
The Si coating layer 14b (FIGS. 2 and 3) can be formed with a uniform thickness.

After that, the extruded multi-hole tube a is shaped into a predetermined shape (dimension) and cut into a predetermined length c (corresponding to the length in the left-right direction in FIG. 1).

Fin 15 The fin 15 is made of a plate material d of an aluminum bare material which is not clad with a brazing material. The plate material d wound into a coil is unwound and bent into a predetermined corrugated shape to have a predetermined length e.
Cut to size. Neither of the coating liquids x and y is applied to the fin 15.

First and second header tanks 11 and 12 The first and second header tanks 11 and 12 are composed of a clad plate material f clad with a brazing material, and the clad plate material f wound in a coil shape is unwound. The above coating solution (non-corrosive flux solution) y is applied to both the front and back sides by a roll coater g.
Then, the flux is applied onto the aluminum surface of the clad plate material f by printing transfer to form a flux coating layer with a uniform thickness.

After that, the clad plate material f is press-molded into a predetermined concave shape to obtain the first and second concave members 110, 120, 111, 121 constituting both tanks 11, 12. As the binder in the coating liquid y, an acrylic resin that does not react with the press working oil and can secure good adhesion is selected. Therefore, even if press molding is performed after forming the flux coating layer, Problems such as peeling and cracking of the flux coating layer do not occur.

Side plates 19 and 20 The side plates 19 and 20 are composed of a clad plate material h clad with a brazing material, and the clad plate material h wound in a coil shape is unwound to obtain the above-mentioned coating solution (non-corrosive flux solution). ) Y is applied by printing transfer using a roll coater i, and dried to form a flux coating layer with a uniform thickness on the aluminum surface of the clad plate material h. After that, the clad plate material h is press-formed into a predetermined shape having a U-shaped cross section.

Cap members 112 and 122 The cap members 112 and 122 are made of a clad plate material j in which a brazing material is clad, and the clad plate material j wound in a coil shape is unwound to obtain the above coating solution (non-corrosive flux solution). By applying y by printing transfer with a roll coater k and drying, a flux coating layer is formed with a uniform thickness on the aluminum surface of the clad plate material j. Then, the clad plate material j is press-formed into a predetermined circular shape.

Inlet side pipe joint 16 and outlet side pipe joint 17 Both pipe joints 16 and 17 are formed into a predetermined joint shape from an extruded aluminum bare material by cutting or the like. Neither of the coating liquids x and y is applied to both pipe joints 16 and 17. (2) Heat exchanger assembling step The above-mentioned parts are assembled in the state shown in FIG. The assembled state of this assembly is held by an appropriate jig (not shown). Note that FIG. 3 shows an enlarged view of the contact portion between the tube 14 and the fin 15 after being assembled in this heat exchanger assembling step. (3) Brazing process The assembly is held by a jig and carried into a brazing heating furnace to integrally braze the parts of the heat exchanger.

Here, as a specific example of the brazing condition,
The brazing furnace atmosphere is an N ₂ gas (or inert gas) atmosphere, and the brazing temperature is 595 ° C to 600 °.
C, and the time at 450 ° C. or higher effective for Zn diffusion is 5 to 2
The heating condition is secured for 5 minutes.

The Zn fluoride-Si coating layer 14b formed on the surface of the tube 14 and each of the parts 11, 12, 19,
In the flux coating layer formed on the surface of 20, 112, 122, the binder component evaporates and scatters in the process (350 ° C. to 450 ° C.) of raising the temperature of the assembly to the brazing temperature. It does not hinder the action. On the other hand, in the Zn fluoride-Si coating layer 14b and the flux coating layer, the non-corrosive flux component is in a molten state (liquid state) at the brazing temperature and evenly spreads over the joint surface between the parts. It is possible to satisfactorily remove the oxide film on the joint surface between the parts and prevent reoxidation of the aluminum surface, and satisfactorily braze the parts.

In the tube 14, the Si component in the Zn fluoride-Si coating layer 14b reacts with the aluminum of the tube 14 to form a eutectic composition having a melting point lower than that of aluminum. The tubes 14 and the fins 15 are brazed by melting.

Also, between other parts, brazing can be performed by melting the brazing material of the clad material.

Through the above steps, the heat exchanger (condenser 10)
Manufacturing can be completed.

In this embodiment, after the heat exchanger assembling step, the entire surface of the assembled body is not coated with the flux, and the surface area becomes maximum among the heat exchanger parts. No fin is applied to the fins 15 and the surface area is relatively small.
4, header tanks 11, 12, side plates 19, 2
No. 0, the cap members 112, 122) are applied flux alone, so that the amount of flux used can be significantly reduced as compared with the conventional technique.

When the Zn diffusion concentration on the surface of the tube 14 in the condenser 10 manufactured as described above was analyzed, the Zn diffusion concentration was 0.91 to 1.10.
Since the Zn diffusion layer having a concentration of about 1 wt% is formed on the surface of the tube 14 as described above, the natural potential of the surface of the tube 14 (Zn diffusion layer) is relative to the aluminum base material of the tube 14. The electric potential is lower than the natural potential.

Specifically, a silver (-) electrode is used as a reference electrode.
Using a silver chloride electrode and 5% NaCl pH 3 as a solution in contact with the electrode, the aluminum base material of the tube 14 (0.45 wt% Cu-0.15 wt% Mn) was used.
When the spontaneous potential of the balance Al) and the Zn diffusion layer on the surface of the tube 14 was measured, the spontaneous potential of the aluminum base material was −680 mV, whereas the spontaneous potential of the Zn diffusion layer on the surface of the tube 14 was −770 mV. Was about 790 mV.

As described above, since the spontaneous potential of the Zn diffusion layer can be set to a sufficiently base potential with respect to the aluminum base material, the Zn diffusion layer can exhibit a good sacrificial corrosion action based on this potential difference, and the corrosion resistance of the tube 14 can be improved. It has been confirmed that it can be improved.

(Second Embodiment) In the first embodiment, the clad plate materials f and h are used as the materials for the first and second header tanks 11 and 12 and the side plates 19 and 20, and the surfaces of the clad plate materials f and h are used. Although the coating liquid (non-corrosive flux solution) y is applied on the upper surface, a brazing material is clad as a material for the first and second header tanks 11 and 12 and the side plates 19 and 20 in the second embodiment. Use a bare aluminum plate. Along with this, the coating liquids for the first and second header tanks 11 and 12 and the side plates 19 and 20 are changed as follows.

That is, the first and second header tanks 11,
For No. 12, the brazing material coating liquid z containing the powder of the Al—Si—Zn alloy is used. Here, the composition of the Al-Si-Zn alloy is specifically 20 wt% Si-7 wt% Zn-
The balance is Al. The composition of the entire solid content of the brazing material coating liquid z is, as shown in the bottom column of FIG. 6, Al—Si—Zn alloy: 70 wt%, flux (KAlF ₄ ): 20 wt.
%, Binder: 10 wt%. The gelling reaction inhibitor (dimethylaminoethanol) is 2 wt% with respect to the solid content as in the coating liquid x, and the solvent (IP
The ratio of A) is the same as that of the coating liquid x. The binder is the same as in the first embodiment.

In the second embodiment, by using the brazing material coating liquid z, the brazing material component (Al-Si) is applied to the first and second header tanks 11 and 12, the flux is applied, and the Zn diffusion layer is formed. Zn coating can be efficiently performed at the same time. And the header tanks 11 and 12
Also in the above, the corrosion resistance can be improved by the Zn diffusion layer. Moreover, by adding a gelling reaction inhibitor, the coating liquid z
The viscosity increase of can be suppressed to a very small value.

Since the brazing material coating liquid z contains the brazing material component (Al-Si) in advance, it is easy to secure the amount of the brazing material. Therefore, a sufficient brazing material amount can be secured at the joint between the header tanks 11 and 12 and the tube 14 without using a clad material, and the joint can be brazed well.

Further, in the second embodiment, the Si-containing coating liquid y ′ is used for the side plates 19 and 20. This Si-containing coating liquid y ′ is a flux solution in which Si is mixed with the flux. Specifically, as shown in the second column from the top of FIG. 6, Si: 30 wt%, flux (KAlF ₄ ): 60 wt%, binder: 10 wt%
Is. The binder is the same as in the first embodiment, and the ratio of the solvent (IPA) is also the same as in the first embodiment.

By applying the coating liquid y'containing Si to the side plates 19 and 20, the side plate 1
Even if 9 and 20 are made of a bare material, a eutectic composition of Al-Si is formed to form side plates 19 and 20 and fins 15.
Brazing between and can be done.

Also in the second embodiment, the tube 14 made of the extruded bare material is coated with the same coating solution x as in the first embodiment, and the cap members 112, 122 made of the clad plate material are coated with the first coating liquid x. The same coating solution (flux solution) y as in the first embodiment is applied.

(Other Embodiments) The first and second header tanks 11 and 12 and the cap members 112 and 122 in the first embodiment are brazed by using the clad plate materials f and j, respectively. , This clad plate material f,
If the same coating liquid x as that of the tube 14 is applied to the aluminum part consisting of j, the viscosity increase of the coating liquid x can be suppressed,
Moreover, the corrosion resistance of each component can be improved by forming the Zn diffusion layer.

That is, the method of the present invention can be applied to either a brazing method for an aluminum member made of a clad plate material or a brazing method for an aluminum member made of an aluminum bare material.

Further, in the first and second embodiments, the example in which IPA is used as the solvent in the coating liquid has been described, but the solvent adjusts the concentration and viscosity according to the coating conditions, and is not limited to IPA. 3MMB (3-methoxy-3
-Methyl-1-butanol), water and the like having an OH ^- group are all applicable.

Further, as a method of applying the coating liquid, in FIG.
The method of applying the coating liquid to the surface of the aluminum member by printing transfer with the roll coater has been described.
You may make it spray a coating liquid on the surface of an aluminum member with a nozzle (sprayer).

The method of the present invention can be applied not only to heat exchangers other than condensers, but also to the multi-flow type heat exchanger configuration shown in FIG. The method of the present invention can be applied to a serpent type heat exchanger configuration in which it is bent in a meandering shape, a heat exchanger configuration in which the tube 14 is formed by laminating plate materials, and the like.

[Brief description of drawings]

FIG. 1 is a front view of a heat exchanger to which the method of the present invention is applied.

FIG. 2 is a cross-sectional view of an extruded multi-hole tube in which a Zn fluoride-Si coating layer is formed by the method of the present invention.

FIG. 3 is a partial cross-sectional view showing an assembled state of the extruded multi-hole tube of FIG. 2 and a corrugated fin made of an aluminum bare material.

FIG. 4 is a process explanatory view of the first embodiment of the method of the present invention.

FIG. 5 is a chart showing the composition of a coating liquid used in the first embodiment of the method of the present invention.

FIG. 6 is a chart showing the composition of a coating liquid used in the second embodiment of the method of the present invention.

FIG. 7 is a graph showing the relationship between the number of days elapsed after preparation of a solution and the change in viscosity.

[Explanation of symbols]

11, 12 ... Header tank, 14 ... Extruded multi-hole tube, 14b ... Zn fluoride-Si coating layer, 15 ... Fin.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B23K 101: 14 B23K 101: 14 (72) Inventor Shoei Teshima 1-chome, Showa-cho, Kariya city, Aichi prefecture Address In stock company DENSO (72) Inventor Takuji Taki 1-1, Showa-cho, Kariya city, Aichi Prefecture In stock company DENSO (72) Inventor Ichiro Yanaka 467 Harima Kasei Co., Ltd. 671 Mizukushi, Noguchi-cho, Kakogawa-shi, Hyogo In the company

Claims (10)

[Claims] 1. A solution containing a flux component, Zn, a binder having a carboxyl group, and a reaction inhibitor that suppresses a reaction between the Zn and the carboxyl group, on at least one surface of a plurality of aluminum members to be brazed. Is applied to carry out brazing between the plurality of aluminum members, and a Zn diffusion layer is formed on the surface of the aluminum member coated with the solution. 2. The flux component and the Zn are Z
The method for brazing an aluminum heat exchanger according to claim 1, wherein n-fluoride is mixed with the solution. 3. The solution is mixed with Si, and during the brazing, the Si reacts with the aluminum member to form a eutectic composition having a melting point lower than that of aluminum. The brazing method for an aluminum heat exchanger according to claim 1 or 2, wherein brazing is performed between the aluminum members. 4. One of the plurality of aluminum members is a multi-hole tube (14) and the other one of the plurality of aluminum members is a corrugated fin (15) brazed to the multi-hole tube (14). 4. The flux solution is applied to the multi-hole tube (14) to braze the space between the multi-hole tube (14) and the corrugated fin (15). Brazing method for aluminum heat exchanger. 5. A brazing material is clad on at least one surface of the plurality of aluminum members, and the plurality of aluminum members are brazed via the brazing material. The method for brazing an aluminum heat exchanger according to item 2. 6. An Al—Si—Zn alloy, a flux component, a binder having a carboxyl group, and a reaction for suppressing a reaction between the Zn and the carboxyl group on at least one surface of a plurality of aluminum members to be brazed. A solution containing a suppressor is applied to perform brazing between the plurality of aluminum members, and a Zn diffusion layer is formed on the surface of the aluminum member coated with the solution. Brazing method. 7. A solution to be applied to an aluminum member before brazing, which contains a flux component, Zn, a binder having a carboxyl group, and a reaction inhibitor that suppresses a reaction between the Zn and the carboxyl group. A solution for brazing an aluminum member, which is characterized by: 8. The flux component and the Zn are Z
The aluminum member brazing solution according to claim 7, which is mixed as n-fluoride. 9. The aluminum member brazing solution according to claim 7, which contains Si. 10. A solution applied to an aluminum member before brazing, which comprises an Al—Si—Zn alloy, a flux component, a binder having a carboxyl group, and a reaction for suppressing the reaction between the Zn and the carboxyl group. A solution for brazing an aluminum member, which comprises an inhibitor.