JP2000271735A - Method for applying flux mixture for blazing for heat exchanger and heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an applying method of flux for brazing for a heat exchanger, with which the dimensional control after brazing is easily executed by partially applying to a prescribed position of each constituted member, and the heat exchanger using the applying method. SOLUTION: On the corner part, cross sectional recessed shape part, obtuse angle part and acute angle part of an aluminum member 2 forming the heat exchanger, flux matrix X is applied and held to the above corner part, etc., with the surface tension of the flux mixture. In the case of heating the flux mixture at the brazing time, the flux mixture is melted and sucked among 2c, 2d, 2e in the interval of each connecting part with capillarity to clean the oxide film formed on the surface of each member. Further, the material precipitated from the flux mixture and aluminum generate an eutectic brazing material phase and the connected part of each member is brazed in good condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for brazing an aluminum or aluminum alloy (hereinafter collectively referred to as "aluminum") member for forming a heat exchanger, and applying a flux mixture to a connection portion of the aluminum or aluminum alloy member. Further, the present invention relates to a method of applying a flux mixture for brazing of a heat exchanger for connecting between connection portions by the flux mixture, and a heat exchanger.

[0002]

2. Description of the Related Art For example, heat exchangers formed by laminating aluminum members are widely used in automotive air conditioning systems.

When brazing an aluminum member or the like, a flux is applied to remove an oxide film formed on the surface of the member, thereby cleaning the member surface, preventing re-oxidation, and improving the wettability of the brazing material. To improve brazing properties.

[0004] As the aluminum member used for the heat exchanger, for example, members constituting the heat exchanger are formed by using a brazing sheet in which a brazing material layer is coated on an aluminum material serving as a core material. After being assembled, a heat exchanger is formed by brazing in a furnace to form a heat exchanger. After assembling each member, a flux or the like is applied with a flux, and the whole is heated by about 600 ° C. Brazing has been performed.

[0005] In addition, there has been proposed a method of performing brazing by flux using a flux mixture without using a brazing material.

[0006]

When a heat exchanger is formed using a brazing sheet, a stacked heat exchanger in which fins are interposed between flat tubes is a multi-stage heat exchanger. There is a problem that the accumulation of the dimensional change of each layer caused by the melting of the brazing material of the brazing sheet becomes so large that it cannot be ignored, which hinders the design flexibility.

[0007] On the other hand, even in a method of supplying a brazing material to a connection portion of each member with a corrosive flux mixture without using a brazing sheet and brazing,
After all, it is necessary to remove the oxide film and braze,
Once the corrosive flux is applied directly to the connection,
Since the flux adhering to the member surface was washed, there was a problem that the operation became complicated.

Further, the conventional flux application method is a method of applying the entire surface of a member by shower spraying or the like. In this method, the amount of application increases, the cost increases, and the connection between the members is increased. Since the flux is also applied between the parts, it is difficult to avoid the dimensional change due to the flux melting at the time of brazing.

In view of the above, the present invention provides a method of applying a flux mixture capable of improving the degree of freedom of design, the yield, and the assembling property by reducing the amount of application without causing dimensional change, and manufactured using the method. The purpose is to provide a heat exchanger.

[0010]

The invention described in the first aspect of the present invention uses a flux mixture for brazing which is applied to an aluminum member forming a heat exchanger and connects the connecting portions of the member. In the application method, each of the aluminum members has a corner for holding the applied substance,
The flux mixture is applied to a corner between the connecting portions where the respective aluminum members are connected to each other, and is applied to a corner where the coating material is held, and when heated, the flux mixture applied to the aluminum member is melted. The flux mixture is drawn between the aluminum member connecting portions to clean the oxide film formed on the surface of each aluminum member, and to braze the heat exchanger brazing flux for connecting the connecting portions of each aluminum member. This is a method for applying the mixture.

In this case, the flux mixture itself may contain a brazing filler metal component. Alternatively, as a flux mixture for brazing, for example, using a non-corrosive flux mixture containing a silicon fluoride compound,
By brazing heating, silicon (Si) precipitates from the flux mixture, and aluminum (Al) and the precipitated Si of the aluminum member form an Al-Si eutectic liquid phase,
The liquid phase may be a brazing material phase to connect the connecting portions of the members.

The precipitated Si reacts with Al of the aluminum member to form an Al-Si eutectic liquid phase and crystallizes as a brazing material phase, thereby performing brazing.

[0013] When the flux mixture for brazing is applied to the vicinity of the connection portion of each aluminum member and is applied to the corner where the coating material of the aluminum member is held, aluminum flux is formed more than when it is formed flat. As the contact angle between the member and the flux mixture decreases, the surface tension of the flux mixture applied to the corner increases,
The flux mixture is stably held at the corners of the aluminum member.

As the temperature rises during brazing, the molten flux mixture is drawn by capillary action between the narrow connections of the aluminum member. The flux mixture drawn between the connecting portions of the aluminum member removes an oxide film formed between the aluminum member connecting portions, and a brazing filler metal component contained in the flux mixture,
And the connection part of an aluminum member is brazed by the brazing material component produced by reaction of the aluminum in a flux mixture or the aluminum in an aluminum member. For this reason, as in the case where the flux mixture is applied to the brazing sheet or the surface of each member, the dimensional change caused by the melting of the brazing material layer or the flux mixture can be almost ignored, thereby improving the degree of freedom in design,
A heat exchanger can be formed, and the yield and the assembling property can be improved.

Further, unlike the conventional method, it is not necessary to apply the flux mixture to the entire surface of the aluminum member, and the amount of the flux mixture to be applied can be reduced, and reliable brazing can be performed while reducing the cost.

As a preferred example to which the present invention is applied, the tube for the heat exchanger is formed of a single aluminum plate, and the center bent portion, the contact portions at both ends, and the aluminum plate are attached to each other. A plurality of beads whose tops are in contact with opposed flat surfaces are formed, and the heat exchange tube is bent around the bent portion, and a plurality of coolant channels are formed by the plurality of beads. Can be

According to a second aspect of the present invention, there is provided a coating method using a brazing flux mixture for applying to a connection portion of an aluminum member forming a heat exchanger and connecting the connection portions to each other. The member has a recess having a cross-sectional shape for holding the applied substance, and the flux mixture is a portion near a connecting portion where the respective aluminum members are connected to each other, and the recess having a cross-sectional shape for holding the applied substance. Is applied, and upon heating, the flux mixture applied to the aluminum member is melted, and the flux mixture is drawn into between the aluminum member connection portions to clean the oxide film formed on the surface of each aluminum member, This is a method for applying a flux mixture for brazing a heat exchanger for connecting connecting portions of aluminum members.

As described above, for example, when a bead is formed in a tube constituting a heat exchanger and a fin is attached between the tubes, when a flux mixture is applied to a concave portion of the bead in the cross-sectional shape concave portion. Due to the surface tension of the flux mixture applied to the recess, the flux mixture is stably held in the shape recess. Further, by the heating at the time of brazing, the molten flux mixture is drawn in between the connection parts of the aluminum member by capillary action, and cleans an oxide film formed between the connection parts of the aluminum member. For example, when the flux mixture itself contains a brazing filler metal component, it is also possible to braze between the connecting parts of the aluminum member by the brazing filler metal component of the flux mixture drawn in between the connecting parts of the aluminum member. .

Therefore, by applying the flux mixture to the cross-section concave portion formed in the tube with a bead or the like,
The amount of the flux mixture applied can be reduced, and reliable brazing can be performed while reducing costs.

According to a third aspect of the present invention, in the coating method using a brazing flux mixture for applying to a connection part of an aluminum member forming a heat exchanger and connecting the connection parts together, The member has an acute-angled portion for holding the applied substance, and the flux mixture is applied to the acute-angled portion where the aluminum material is connected to each other at a connection portion where the respective aluminum members are connected to each other, where the applied substance is held. Then, at the time of heating, the flux mixture applied to the aluminum member is melted, the flux mixture is drawn between the aluminum member connection parts, and the oxide film formed on the surface of each aluminum member is cleaned, and each aluminum member is cleaned. This is a method of applying a flux mixture for brazing a heat exchanger for connecting the connection portions of the above.

As described above, when the flux mixture is applied to the acute angle portion of the aluminum member, the flux mixture is stably held at the acute angle portion by surface tension, and the flux mixture melted at the time of heating causes capillary action between the connection portions of the aluminum member. And cleans the oxide film formed between the connecting portions of the aluminum member.

Further, for example, when the flux mixture itself contains a brazing filler metal component, the connecting parts of the aluminum members are brazed to each other by the brazing filler metal component of the flux mixture drawn in between the connecting parts of the aluminum member. It is also possible.

Accordingly, by applying the flux mixture to the sharp corners formed in the tube with beads or the like, the amount of the flux mixture applied can be reduced, and reliable brazing can be performed while reducing the cost. .

According to a fourth aspect of the present invention, in the coating method using a brazing flux mixture for applying to a connection portion of an aluminum member forming a heat exchanger and connecting the connection portions to each other, The member has an obtuse portion for holding the applied substance, and the flux mixture is applied to the obtuse portion where the aluminum material is connected to each other at a connection portion where the aluminum members are connected to each other, where the applied substance is held. Then, at the time of heating, the flux mixture applied to the aluminum member is melted, the flux mixture is drawn between the aluminum member connection parts, and the oxide film formed on the surface of each aluminum member is cleaned, and each aluminum member is cleaned. This is a method of applying a flux mixture for brazing a heat exchanger for connecting the connection portions of the above.

As described above, when the flux mixture is applied to the obtuse portion located in the vicinity of the connection portion of the aluminum member, the flux mixture is stably held at the obtuse portion by the surface tension, and the flux mixture melted during heating is applied to the aluminum member. It is drawn in by capillary action between the connection parts, and cleans the oxide film between the connection parts. Also, for example,
When the brazing filler metal component is contained in the flux mixture, each connection part is brazed by the flux mixture drawn between the connection parts.

Therefore, by applying the flux mixture to the obtuse portion formed in the tube with a bead or the like, the amount of the flux mixture to be applied can be reduced and the brazing can be reliably performed while reducing the cost.

According to a fifth aspect of the present invention, in a heat exchanger formed of an aluminum member, a flux mixture is applied to a corner portion, a cross-sectional shape concave portion, an acute angle portion or an obtuse angle portion of the aluminum member and heated. Sometimes, the flux mixture applied to the aluminum member is melted, the flux mixture is drawn between the aluminum member connection portions, and the oxide film formed on the surface of each aluminum member is cleaned, and the connection portion of each aluminum member is cleaned. It is a heat exchanger formed by connecting them.

As described above, when the flux mixture is applied to the corners, cross-section concave portions, acute angle portions or obtuse angle portions of the aluminum member, the surface tension is applied to the corner portions, cross-section concave portions, acute angle portions or obtuse angle portions of the aluminum member. The flux mixture is stably held, and at the time of heating, the flux mixture applied to the aluminum member is melted and drawn between the aluminum member connection parts, and the oxide film formed on each aluminum member surface is cleaned, and The connection between the aluminum members is brazed by the brazing filler metal component contained in the flux mixture or the brazing filler metal component generated by the reaction of the aluminum member of the flux mixture with aluminum. A heat exchanger is formed.

As a result, it is possible to provide a heat exchanger whose dimensional change before and after brazing is extremely small.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, specific examples of the present invention will be described in detail.

In this embodiment, the aluminum member is brazed by using a mixture of a non-corrosive silicon fluoride compound and a fluorine compound.

K ₂ SiF ₆ used as the basic composition of the non-corrosive flux is represented by the following formula:
It is considered that Si was precipitated.

3K₂SiF₆+ 4Al = 3Si + 2KA
IF₄+ 2K₂AlF₅  From the above reaction formula, Si in potassium fluorosilicate is applied
Is believed to precipitate on the damaged aluminum member
You.

In this embodiment, the K ₂ SiF ₆ -Al
In F ₃ based flux mixture was added AlF 3 _-KF system fluoride at a predetermined ratio, it was confirmed test for solderability. Furthermore, a flux mixture obtained by adding an AlF ₃ -KF-based fluoride and a metal and / or a metal alloy (eg, Al and / or an Al-Si alloy) at a predetermined ratio to a K ₂ SiF ₆ -AlF ₃ -based flux mixture. The brazing property was also confirmed using the one coated with.

In this embodiment, a polyhydric alcohol such as glycerin or ethylene glycol or a processing oil is added as a binder to the above-mentioned flux mixture, and the mixture is applied in the form of a paste.

The heat exchanger using the flux mixture application method of this embodiment is, for example, as shown in FIG. 1, laminated on a plurality of flat tubes 2 via corrugated fins 3 in parallel with each other. Both ends are header pipe 4
Is a laminated capacitor 1 that is integrally brazed and joined.

Next, a coating method test was conducted by changing the application area of the flux mixture using the members constituting the tubes and fins used in the heat exchanger 1.

FIG. 2 is a sectional view of a tube used in the test of this example. In addition, X in FIG. 2 shows the flux mixture applied near the bead portion 2b on the inner surface of the tube.

The tube 2 used in this example is formed by rolling a single aluminum plate, and is bent around a bent portion 2a to form a plurality of beads 2b and a plurality of refrigerant flow paths partitioned by the beads 2b. Is formed. The bead 2b is formed over the entire length of the tube so as to protrude inward from the flat surface of the tube 2 and to have a convex shape in which the top 2d of the bead 2b abuts on the opposing flat surface 2c.

Next, as shown in Table 1 below, the application area of the flux mixture was applied to the inside of the tube 2, and a test for confirming brazing properties was performed.

[0041]

[Table 1] After applying the flux mixture to the inside of the tube in the application area and application amount shown in Tables 1 (1) to (4),
Heating was performed at 10 ° C. to confirm brazing properties.

The results are shown in Table 1 (3) and FIG. 2 when the flux mixture was applied using the corner of the bulging portion on one side in the upward direction inside the tube where the application amount of the flux mixture X was the smallest. Even if there is, the flux mixture melted by the heating flows down the inner wall of the tube, and is drawn into the narrow space between the bead apex 2d, the uneven surface 2c inside the tube and the end contact portions 2e, 2e of the tube 2 by capillary action. Then, Si precipitated from the molten flux mixture becomes a eutectic liquid phase with Al precipitated from the aluminum member constituting the tube to form a brazing filler metal phase, and no brazing failure due to poor filling is not recognized. Was.

That is, the coating amount (3) of the flux mixture applied to the vicinity of the bead portion on one side of the tube is compared with the application amount (2) of the flux mixture applied to both inner surfaces of the tube (the bead portion and the vicinity of the bead portion). Despite being about one third, good brazing properties could be confirmed.

Note that the tube shape or bead shape used for brazing is not limited to the tube shape or bead shape of the present embodiment, and for example, the brazing flux applying method of the present embodiment is also used for inner fin type tubes and the like. It is possible.

Next, using a fin and a tube attached between the tubes, a test of a method of applying the flux mixture was performed.

Next, when the flux mixture X is applied to the bead 2b of the tube 2 in the vicinity of the bead 2b (FIG. 3 (a)), the inner and outer surfaces of the tube 2 are spray-sprayed in the same manner as in the conventional application method. In the case where the flux mixture X was applied to the sample (FIG. 3 (b)), a test for confirming brazing properties was performed.

Table 2 shows the results.

[0048]

[Table 2] After the application amount shown in Table 2 was applied, the coating was heated at 600 ° C. to 610 ° C. to confirm the brazing property.

As a result, the bead 2b and the bead 2b
When flux is applied in the vicinity (Table 2 (1) and FIG.
(A)) and the case where the flux is applied to the entire inner and outer surfaces of the tube 2 (Table 2 (2) and FIG. 3 (b)). A sufficient brazing material phase was confirmed, no brazing failure due to poor filling was observed, and it was confirmed that the brazing properties were good in both cases.

As shown in Table 2, the beads 2 of the tube 2
b, the inner surface bead 2b of the tube 2
When the flux mixture is applied to the vicinity, the amount of application is smaller than when the flux mixture is applied uniformly on the entire inner surface of the tube.

Therefore, the application of the flux mixture is sufficient if the cross section of the bead 2b is in the concave portion 2f and the vicinity of the bead 2b, and the flux mixture is applied directly between the bead apex 2d, that is, the connection with the opposing uneven surface 2c. It was confirmed that there was no need to do this. Thereby, the dimensional change in the heat exchanger lamination direction before and after brazing can be made very small.

In addition, it was confirmed that the flux mixture was held in the corners (obtuse and acute) near the concave portion 2f and the bead 2b, except during brazing, and the state was stable. Therefore, when the flux mixture is applied to the entire surface of the tube as in the related art, the dimensional change between the connecting portions of the respective members becomes large due to the melting at the time of the brazing heating. Since the number is small, each member can be designed without considering a strict dimensional tolerance.

Further, since brazing can be reliably performed with a small amount of flux, the manufacturing cost can be reduced.

When brazing is performed only by partial application of the flux as in this example, the corrosion resistance inside the tube becomes a problem, but when only the refrigerant comes into contact with the inner surface of the tube like an evaporator or a condenser. However, since the corrosion resistance inside the tube does not matter much, it is sufficiently possible to use the flux coating method of this example.

Further, even when it is necessary to perform a chromate treatment or the like to secure the corrosion resistance of the outer surface of the heat exchanger, there has been a problem that a film such as chromate is not coated well if a large amount of brazing residue is present. However, according to the flux applying method of the present example, the flux mixture is applied only to the minimum necessary portion, so that the surface residue is small and good corrosion resistance treatment can be performed.

[0056]

As described above, according to the present invention,
Unlike the conventional case, it is not necessary to apply the flux mixture to the entire surface of the aluminum member, the amount of the flux mixture to be applied can be reduced, and the members can be reliably brazed while reducing the cost.

Further, according to the present invention, the dimensional control before and after brazing can be surely performed, and the degree of freedom in design is improved.

[0058]

[Brief description of the drawings]

FIG. 1 is a front view of a heat exchanger according to a specific example of the present invention.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of a tube of a heat exchanger according to a specific example of the present invention.

FIG. 3 (a) is a schematic cross-sectional view showing an application area of a tube, a fin, and a flux mixture according to a specific example of the present invention, and FIG. 3 (b) is a tube, fin, and a flux mixture according to a conventional example. FIG. 3 is a schematic cross-sectional view showing an application area.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 heat exchanger 2 tube 2 a bent portion 2 b bead 2 c flat surface 2 d top 2 e contact portion 2 f concave interior 3 fin 4 header pipe 5 refrigerant inlet 6 refrigerant outlet X flux mixture

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) // B23K 101: 14 103: 10

Claims (5)

[Claims] 1. A coating method using a flux mixture for brazing for applying to an aluminum member forming a heat exchanger and connecting connecting portions of the member, wherein each of the aluminum members is formed by applying a coated substance. Having a corner portion for holding, the flux mixture is applied to a corner portion between the connection portions where the respective aluminum members are connected to each other, and the coating material is held on the corner portion; The applied flux mixture is melted, and the flux mixture is drawn between the aluminum member connecting portions to clean the oxide film formed on the surface of each aluminum member and connect the connecting portions of each aluminum member. A method for applying a flux mixture for brazing a heat exchanger. 2. A coating method using a brazing flux mixture for applying to a connection portion of an aluminum member forming a heat exchanger and connecting the connection portions, wherein the aluminum member holds the applied substance. The flux mixture is applied to a portion between the connecting portions where the respective aluminum members are connected to each other, and is applied to the cross-sectional concave portion in which the coating substance is held; Is melted, the flux mixture is drawn into between the aluminum member connecting portions, and the oxide film formed on the surface of each aluminum member is cleaned, and the connecting portions of each aluminum member are connected. A method for applying a flux mixture for brazing a heat exchanger. 3. A coating method using a brazing flux mixture for applying to a connecting portion of an aluminum member forming a heat exchanger and connecting the connecting portions, wherein the aluminum member holds the applied substance. The flux mixture is applied to an acute portion where the coating substance is held in a portion near a connection portion where the aluminum members are connected to each other, and the flux mixture is applied to the aluminum member during heating. The melted flux mixture is melted, and the flux mixture is drawn between the aluminum member connecting portions to clean the oxide film formed on each aluminum member surface and to connect the connecting portions of each aluminum member. A method for applying a flux mixture for brazing a heat exchanger. 4. A coating method using a brazing flux mixture for applying to a connection portion of an aluminum member forming a heat exchanger and connecting the connection portions, wherein the aluminum member holds the applied substance. The flux mixture is applied to an obtuse portion where the coating material is held in a portion near a connection portion where the aluminum members are connected to each other, and the flux mixture is applied to the aluminum member during heating. The melted flux mixture is melted, and the flux mixture is drawn between the aluminum member connecting portions to clean the oxide film formed on each aluminum member surface and to connect the connecting portions of each aluminum member. A method for applying a flux mixture for brazing a heat exchanger. 5. A heat exchanger formed from an aluminum member, wherein a flux mixture is applied to a corner, a cross-sectional concave portion, an acute angle or an obtuse angle of the aluminum member, and the flux applied to the aluminum member during heating. The mixture is melted, and the flux mixture is drawn between the aluminum member connecting portions to clean the oxide film formed on the surface of each aluminum member and to connect and connect the connecting portions of each aluminum member. Characterized heat exchanger.