JP2001335869A - Al ALLOY-BRAZING SHEET EXCELLENT IN BRAZABILITY, BRAZING METHOD AND HEAT EXCHANGER - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al alloy-brazing sheet capable of being thinned without deteriorating its corrosion resistance and brazability, to provide its brazing method and to provide a heat exchanger produced by using the same brazing sheet. SOLUTION: In this Al alloy-brazing sheet obtained by coating at least either surface of a core material 1 formed by an Al alloy with a brazing filler metal layer 2, the brazing filler metal layer 2 is formed of an Al-Si-Mg brazing alloy containing, by mass, 11.0 to 12.5 mass% Si and 0.3 to 5.0% Mg, and the balance substantially Al. As to the brazing sheet, preferably, the brazing is performed in a vacuum atmosphere and also in the temperature range of (TL+3) deg.C to (TL+10) deg.C provided that the liquidus temperature of the above Al-Si-Mg brazing alloy is defined as TL.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al alloy brazing sheet which has a conventional level of corrosion resistance and can be made thinner, a brazing method thereof, and a heat exchanger using the same.

[0002]

2. Description of the Related Art In order to prevent global warming, it has been demanded to suppress carbon dioxide emissions. For this reason, in order to improve the fuel efficiency of automobiles, a reduction in the weight of a heat exchanger (evaporator) for a car air conditioner mounted on the automobile is required as part of the weight reduction of the automobile.

[0003] This type of heat exchanger is assembled by brazing aluminum alloy members together for weight reduction. A tube forming a coolant flow path and an aluminum alloy brazed to this tube are used. And a corrugated fin. The tube is made of aluminum alloy core material with A
It is manufactured by processing an Al alloy brazing sheet clad with a brazing material layer made of an l-Si-based brazing alloy into a tube. The fins are brazed by melting a brazing material layer of a brazing sheet constituting the tube. The Al-Si brazing alloy is:
Usually, from the viewpoint of productivity, those having a hypoeutectic composition having an Si content of less than 11 mass% are used.

Conventionally, A for producing a tube of a car air conditioner has been used.
As an alloy brazing sheet, for example, 420 μm
A brazing material layer having a thickness of about 90 μm is formed on both sides of a core material having a thickness of about 90 μm, and has a total thickness of about 600 μm. At least 50% of the brazing material in the brazing material layer of the brazing sheet flows to the brazing portion (fillet portion) of the fin during brazing. On the other hand, the brazing material remaining on the core material (referred to as a residual brazing material) causes atoms to diffuse with the core material, erodes the core material, and forms an erosion portion. Since the erosion portion hardly contributes to the corrosion resistance, the corrosion resistance is determined mainly by the thickness of the core portion where no erosion occurs (referred to as a residual core material).
Conventionally, the thickness of the remaining core material is required to be at least 270 μm.

[0005]

In recent years, car air conditioners for automobiles have been increasingly required to be reduced in weight, and the heat exchangers thereof are also required to be further reduced in weight. In order to reduce the weight of the heat exchanger, it is effective to reduce the thickness of the Al alloy brazing sheet. However, simply reducing the thickness may degrade corrosion resistance and brazing properties. Corrosion resistance is mainly governed by the thickness of the residual core material after brazing of the brazing sheet. If the thickness is small, the life until corrosion holes penetrate the tube (corrosion resistance life) is shortened. On the other hand, the brazing property is related to the thickness of the brazing material layer of the brazing sheet. If the brazing material layer is thin, poor brazing occurs.

The present invention has been made in view of the above problems, and has been made using an Al alloy brazing sheet that can be made thinner without impairing corrosion resistance and brazing properties, a brazing method thereof, and the brazing sheet. It is intended to provide a heat exchanger.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to minimize the residual brazing material that does not contribute to the joining during brazing and also minimize the amount of erosion of the core material by the residual brazing material. As a result, even if the thickness of the core material and the thickness of the brazing material layer are reduced as compared with the conventional case, the corrosion resistance and the brazing property are not impaired.
An alloy brazing sheet and a brazing method thereof have been found, and the present invention has been completed.

That is, the Al alloy brazing sheet of the present invention is a brazing sheet in which at least one surface of a core material formed of an Al alloy is coated with a brazing material layer, The brazing material layer is composed of Si: 11.0 to 12.5 mass%, Mg: 0.3 to
5.0 mass%, Al-Si containing Al as the essential component
-Formed by a Mg-based brazing alloy, in a vacuum atmosphere,
And the liquidus temperature of the Al-Si-Mg based brazing alloy is T
L is used for brazing within a temperature range of (TL + 3) ° C. to (TL + 10) ° C. The total thickness of the brazing sheet is preferably set to 500 μm or less.

Further, the brazing method according to the present invention is described in claim 2.
As described in the above, when a member to be joined made of an Al alloy is brazed to the Al alloy brazing sheet, in a vacuum atmosphere, and when the liquidus temperature of the Al-Si-Mg-based brazing alloy is TL. (TL + 3) ° C. to (TL + 1
0) This is a method of brazing within a temperature range of ° C.

According to a third aspect of the present invention, there is provided a heat exchanger in which a tube manufactured using the Al alloy brazing sheet is brazed with an Al alloy fin. The fins are not brazed, the thickness of the non-fillet portion of the tube after brazing is 430 μm or less, and the thickness of the residual core material not causing erosion is 270 μm or more.

Japanese Patent Application Laid-Open Nos. 9-94689 and 7-331372 describe thin Al alloy brazing sheets having a thickness of about 500 μm. % Or less, and a large amount of Zn is added.
% Or less, and one or more of Zn or In are added, and the brazing material according to the present invention and the component system are completely different, and the technical ideas are different.

[0012]

FIG. 1 shows an Al alloy brazing sheet according to an embodiment of the present invention, in which a brazing material layer 2 is laminated on both surfaces of a core material 1 formed of an Al alloy having excellent strength and corrosion resistance. ing. As the Al alloy of the core material 1, typically, Mn: 0.05 to 2.0 mass%, and the balance A
Al alloy containing l as an essential component, for example, JIS 3000
It is formed of a system Al alloy.

On the other hand, the brazing filler metal layer 2 comprises Si: 11.0 to 1
2.5 mass%, Mg: 0.3-5.0 mass%, balance Al
Is formed of an Al-Si-Mg-based brazing alloy containing aluminum as an essential component. This Al alloy brazing alloy enables brazing at a low temperature without impairing brazing properties. Hereinafter, the technical significance of this brazing material will be described in detail.

The erosion of the core material by the residual brazing material at the time of brazing is promoted by diffusion and intrusion of Si in the brazing material into the core material side. Since the diffusion of Si is sensitive to temperature, if the brazing temperature is set to a low temperature, the diffusion of Si can be suppressed, and erosion can also be suppressed. On the other hand, if the brazing is performed at a low temperature, the fluidization of the brazing material is impaired, so that the brazing property is reduced. The Al- according to the present invention
According to the Si-Mg-based brazing alloy, since appropriate amounts of Si and Mg are added, even if brazing is performed at a low temperature, the fluidity of the brazing material does not decrease. Therefore, low-temperature brazing can be performed, whereby the diffusion of Si can be suppressed, and Si, which is advantageous for fluidity, can be stopped in the brazing material. As a result, even if the thickness of the brazing filler metal layer is made thinner than before, the amount of brazing filler metal used for brazing can be secured, and the amount of residual brazing filler metal that forms the basis of erosion is also reduced. be able to. Therefore, erosion can be effectively suppressed by the low brazing temperature, the reduction in the amount of the brazing material used, and the effect of improving the fluidity of Si retained in the brazing material. As a result, A
The thickness of the core material 1 of the 1 alloy brazing sheet can also be reduced by the amount by which the erosion is suppressed, and the total thickness of the brazing sheet can be effectively reduced.

Al-Si-M for forming the brazing material layer 2
The reason why the g-based brazing alloy exhibits excellent fluidity even at a low brazing temperature is not necessarily clear, but is considered as follows. The Si concentration of the brazing alloy is Al-
It is near the Si eutectic point, and its liquidus temperature is lower than that of the conventional Al-Si brazing alloy. The brazing material can be sufficiently melted even at a temperature. Furthermore, when the brazing temperature is low, the amount of Si diffused from the brazing material to the core material is also reduced, and the Si in the brazing material is maintained without being reduced in the brazing heating step, contributing to an improvement in fluidity. Probably because it was possible.

Here, the reasons for limiting the components of the Al—Si—Mg brazing alloy will be described. Hereinafter, the unit is mass%. Si: 11.0 to 12.5% Si is added to lower the liquidus temperature and to stop in the brazing material during low-temperature brazing to improve fluidity. 1
If it is less than 1.0%, such an effect is too small.
If it exceeds 2.5%, it becomes difficult to produce a brazing filler metal. That is, in order to produce a brazing material, it is necessary to first produce an ingot, but when the Si concentration exceeds 12.5%, Si is generated in primary crystals, and it becomes difficult to obtain an ingot. For this reason, Si
The lower limit of the amount is 11.0%, preferably 11.2%, and the upper limit is 12.5%, preferably 12.2%.

Mg: 0.5-3.0% Mg has a function of lowering the liquidus temperature of the brazing filler metal and removing an oxide film formed on the surface of the brazing filler metal melted during vacuum brazing. . At less than 0.5%, such effects are insignificant, while over 3.0% of Mg vapor-produced material is formed, which significantly contaminates the vacuum brazing furnace. For this reason, the lower limit of the amount of Mg is set to 0.5%, preferably 1.0%, and the upper limit is set to 3.0%, preferably 2.0%.
%.

As is apparent from the above description, the Al alloy brazing sheet forms the brazing material layer 2 with a specific Al.
-Si-Mg brazing alloy allows brazing at low temperatures and excellent fluidity.
Even if the brazing material layer is made thin, there is no problem in brazing. In addition, since erosion can be suppressed under low-temperature brazing, the thickness of the core material can be reduced. For this reason, even if the total thickness is 500 μm or less, there is no problem in brazing properties, and the weight can be reduced. Preferably, the core material is about 370 μm or more, the brazing material layer is about 35 to 65 μm, and the total thickness is about 500 μm or less.

The brazing of the Al alloy brazing sheet of the present invention is performed in a vacuum
When the liquidus temperature of the i-Mg based brazing alloy is TL (T
It is desirable to braze within a temperature range of (L + 3) ° C. to (TL + 10) ° C. If the temperature is lower than (TL + 3) ° C., in an industrial brazing process, a temperature variation inevitably occurs in the brazing object, and a portion having a temperature lower than the melting point may be locally generated, resulting in poor brazing. On the other hand, (TL
If the temperature exceeds (+10) ° C., the advantage of low-temperature brazing is lost, erosion is increased, and corrosion life is shortened.
Further, by brazing in a vacuum atmosphere, it is possible to easily remove an oxide film generated on the surface of the brazing material, and to secure good brazing properties. The liquidus temperature can be measured using a differential thermal analyzer under a temperature change of about 10 ° C./min.

FIG. 2 shows a main structure of a heat exchanger according to an embodiment of the present invention.
Al alloy fin 1 formed into a corrugated shape between 1 and 11
2 are brazed to the outer surface of tube 11. The tube 11 has a coolant channel 13 formed therein, and is assembled by brazing flange portions of a pair of concave members. The concave member is formed in a concave shape using the Al alloy brazing sheet shown in FIG. In the figure, the cross section of the wall of the tube 11 is 3 as in the case of the brazing sheet.
Although it has a layer structure, it is depicted in a simplified manner.

The conditions for brazing the tube 11 and the fins 12 are (TL + 3) ° C. to (TL + 1) as described above.
0) Performed within a temperature range of ° C. The brazing sheet has a core material of about 370 μm or more and a brazing material layer of 35 to
By using one having a thickness of about 65 μm and a total thickness of about 500 μm or less, the total thickness of the non-fillet portion 14 of the tube 11 can be made 430 μm or less, and the weight of the heat exchanger can be reduced. In this case, the thickness of the residual core material in the non-fillet portion 14 is 270 μm
The above can be ensured, and a corrosion life equivalent to that of the related art can be ensured.

Although the Al alloy brazing sheet according to the above embodiment has a brazing material layer 2 laminated on both sides of the core material 1, the brazing material layer does not necessarily have to be formed on both surfaces of the core material 1. It may be formed only on the side where attachment is performed.

Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not construed as being limited to such Examples.

[0024]

[Example] JISA3003 Al alloy (mass% 0.6%)
% Si-0.7% Fe-1.2% Mn-0.1% Zn-
The core sheet consisting of the remainder Al) and S shown in Table 1 below
Al-Si-Mg alloy containing i amount (Si-1.2 mass%
And a thin plate for a brazing material layer composed of Mg-remainder Al).
The thin plate for the brazing material layer was laminated on both sides of the thin plate for the core material and clad and rolled. After annealing, cold rolling and annealing were performed.
As shown in FIG.
Al having a three-layer structure in which a brazing material layer 2 having a thickness of 0 μm is laminated.
An alloy brazing sheet was produced. In addition, each thin plate,
It was manufactured by melting an Al alloy of a predetermined component, hot rolling, and further performing cold rolling and annealing.

This brazing sheet was formed into a concave member as a tube member, and was formed into a corrugated fin using JIS A3003 alloy as a fin material. FIG.
As shown in the above, the concave member is assembled in a tube shape facing each other, and the fins are arranged in contact with the outer surface of the concave member,
A heat exchanger was manufactured by vacuum brazing. Brazing was carried out in a vacuum atmosphere of 10 ^-4 torr at a brazing temperature shown in Table 1 for 5 minutes.
Table 1 also shows the liquidus temperature of the brazing material in each brazing material layer. The liquidus temperature was 10 ° C. by a differential thermal analyzer.
Measured under a temperature change of / min.

With respect to the obtained heat exchanger, the total thickness of the non-fillet portion 14 of the tube 11 and the thickness of the remaining core material were examined. The thickness of this part is 430 μm or less, which is recognized to be effective in reducing the weight.
A level equal to or greater than 70 μm was evaluated as a pass level. In addition, brazing properties were also evaluated. The brazing property was evaluated by injecting gas into the tube 11 after brazing and applying pressure to the tube, and determining whether or not there was gas leakage (absence: o, existence: x). These measurement results and evaluation results are also shown in Table 1.

[0027]

[Table 1]

From Table 1, it can be seen that Sample No. 3 has a low Si content less than the range of the invention, so that the fluidity of the brazing material is inferior, so that erosion is promoted and the remaining core thickness of the non-fillet portion is less than the conventional level. became. On the other hand, in No. 12, since the amount of Si was excessive, casting after melting was difficult, and it could not be processed into a thin plate, and a brazing sheet could not be manufactured.
Further, even if the amount of Si is appropriate, the brazing temperature is set to the liquidus temperature T
In Nos. 4 and 6 below (TL + 3) ° C. with respect to L,
Since the residual brazing material increases, the total thickness after brazing is generally large, and there is also a problem in brazing properties. On the other hand, No. 5, 7, 1 where the brazing temperature exceeds (TL + 10) ° C.
In Nos. 0 and 11, erosion was promoted, and the residual core thickness after brazing was lower than the conventional level. On the other hand, in Examples Nos. 1, 2, 8 and 9, the total thickness of the non-fillet portion after brazing was 420 μm or less, the residual core thickness was 270 μm or more, and the brazing property was good. Met.

[0029]

The aluminum alloy brazing sheet of the present invention,
According to the brazing method, excellent brazing properties can be obtained even at a predetermined low-temperature brazing, and the erosion of the core material can be suppressed by reducing the amount of the brazing material and suppressing the diffusion of Si in the brazing material. It is possible to improve the corrosion resistance. For this reason, a conventional level of corrosion resistance life can be ensured by reducing the thickness of the brazing material layer and the thickness of the core material, which can contribute to weight reduction. Further, according to the heat exchanger of the present invention, the thickness of the remaining core material is reduced to the conventional level of 27 mm, even though the total thickness of the non-fillet portion is as thin as 430 μm or less.
It is 0 μm or more, and it is possible to reduce the weight while ensuring the conventional corrosion life.

[Brief description of the drawings]

FIG. 1 shows a partial cross-sectional view of an Al alloy brazing sheet according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of the heat exchanger according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core material 2 Brazing material layer 11 Tube 12 Fin 14 Non-fillet part

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B23K 31/02 310 B23K 31/02 310D 35/22 310 35/22 310E F28F 21/08 F28F 21/08 A // B23K 101: 14 B23K 101: 14 103: 10 103: 10

Claims (3)

[Claims] 1. A brazing sheet in which a brazing material layer is coated on at least one surface of a core material formed of an Al alloy, wherein the brazing material layer is composed of Si: 11.0 to 12.5 mass%, M
g: 0.3-5.0 mass%, formed by an Al-Si-Mg-based brazing alloy containing Al as an essential component, in a vacuum atmosphere, and at the liquidus of the Al-Si-Mg-based brazing alloy When the temperature is TL, (TL + 3) ° C. to (TL + 1
0) An aluminum alloy brazing sheet excellent in brazing properties used for brazing within a temperature range of ° C. 2. When brazing a member to be joined made of an Al alloy to the Al alloy brazing sheet according to claim 1, the liquidus temperature of the Al—Si—Mg based brazing alloy is set in a vacuum atmosphere. TL (TL + 3) ° C ~
A brazing method for brazing within a temperature range of (TL + 10) ° C. 3. A heat exchanger in which a fin made of Al alloy is brazed to a tube manufactured using the Al alloy brazing sheet according to claim 1, wherein the fin is not brazed. The thickness of the non-fillet portion after brazing is 430 μm or less, and the thickness of the residual core material without erosion is 2 mm.
A heat exchanger having a size of 70 μm or more.