JPH09316578A - Al alloy brazing sheet for vacuum brazing - Google Patents

Abstract

(57) [Problem] To find an Al alloy brazing sheet excellent in corrosion resistance suitable for a heat exchanger to be joined and assembled by vacuum brazing. SOLUTION: Mn: 0.5 to 2.0 mass% (hereinafter simply referred to as%), Cu: 0.1 to 1.0%, Mg: 0.
05 to 0.5%, Ti: 0 to 0.3%, the balance being Al alloy core material consisting of Al and unavoidable impurities, and coated on both sides with a clad ratio of 5 to 20% on each side. Al-Si-Mg-based brazing filler metal, and between the brazing filler metal corresponding to the outer surface of the tank portion and the refrigerant passage and the core material, Mn: 0.5-2.0%, Mg: 0.05- 0.5
%, Ti: 0 to 0.3%, and In: 0.0
An Al alloy containing 5 to 0.5%, the balance being Al and unavoidable impurities and having a thickness of 30 μm or more,
An aluminum alloy brazing sheet for vacuum brazing, characterized in that an intermediate layer having a clad ratio of 35% or less is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy heat exchanger for use in automobiles and various industries, which is suitable for brazing (assembly and joining) by vacuum brazing, in particular, and has excellent corrosion resistance. The present invention relates to an alloy brazing sheet.

[0002]

2. Description of the Related Art A brazing method is an effective method for manufacturing a complex structure made of an Al alloy, and a vacuum brazing method which does not require flux is particularly popular because it does not cause pollution. It is being appreciated. In vacuum brazing, a brazing sheet having Al or an Al alloy as a core material and one or both sides of which is clad with an Al alloy brazing material as a clad material is formed into various shapes, and these members are formed into a predetermined structure such as a heat treatment material. It is a method of assembling in an exchanger and heating it in a vacuum to perform brazing.

For brazing sheets for vacuum brazing, various aluminum alloys for core materials and aluminum alloy brazing materials for skin materials have been developed, and these materials are now JIS.
-Z-3263 and JIS-H-4000. As a brazing sheet for vacuum brazing used in a heat exchanger, JIS 3003 (representative example Al-0.15 mass% Cu-1.1 mass%) is used as a core material.
Mn alloy, mass% will be simply referred to as% hereinafter), JIS3
005 (representative example Al-1.1% Mn-0.4% Mg alloy), JIS3105 (representative example Al-0.6% Mn-)
0.6% Mg alloy) as a skin material according to JIS 4004 (typical example Al-10% Si-1.5% Mg alloy), JIS
4104 (Representative example Al-10% Si-1.5% Mg-
It is usual to use a brazing filler metal (0.1% Bi alloy). The brazing sheet has a plate thickness of about 0.5 to 1.2 mm, and the brazing material has a clad ratio of 5 to 15% per one side with respect to the total plate thickness, and the brazing sheet is clad on one or both sides.

As a heat exchanger made of an aluminum alloy having a hollow structure using such a brazing sheet, a drone cup type evaporator, an oil cooler, a radiator and the like are manufactured. For example, as shown in FIG. 4, in a Delon cup type evaporator 10, a brazing sheet is formed into a member 1 shown in FIGS. 1 and 2, and the member 1 is laminated as shown in FIG. The corrugated fins 2 are arranged between the two, and the side plate 6, the refrigerant inlet pipe 7, and the refrigerant outlet pipe 8 are further arranged and assembled, which is vacuum brazed, and the brazing is 1.3 × 10 ^{− 3} ~
It is performed by heating to about 873K in a vacuum of about 1.3 × 10 ⁻² Pa.

[0005]

With the reduction in the weight of automobiles, it has been required that these heat exchangers be made thinner. On the other hand, automobiles are used in various environments, and materials that can withstand all use conditions are required. That is, sea salt, Cl _{chromatography} such as snow melting salt, corrosion substances SO _X or the like from the exhaust gas adhering to the evaporator surface. Then, even if the corrosion material is concentrated due to repeated dryness and humidity caused by the use and stoppage of the air conditioner, and the chromate treatment is performed, the evaporator material needs to have high food resistance. Particularly in the case of a drone cup type heat exchanger that does not have a sacrificial layer due to the restriction of the brazing process, the corrosion resistance of the core material is the most important required property for the material, and the development of a corrosion resistant brazing sheet has been earnestly desired and various studies have been made. Is being done.

The corrosion resistance of the brazing sheet is related to the distribution of elements in the plate thickness direction of the material, but the elements such as Cu and Zn that contribute to the corrosion resistance of the material are centered on the plate thickness when brazing heat is applied. The distribution is symmetrical with respect to the front and back. Therefore, when pitting occurs on the surface of the brazing sheet, the material whose pitting progresses more slowly on the surface side than the center of the plate thickness has a faster pitting progress after passing through the center of the plate thickness. That is, it is no exaggeration to say that the portion that contributes to the improvement of corrosion resistance is half the plate thickness, and there is a limit to the improvement of the penetration life by adding an element to the core material. Therefore, when pitting corrosion occurs on the surface of the brazing sheet, a material having a slower pitting corrosion on the surface side than the plate thickness center has a faster pitting corrosion progress after passing the plate thickness center. That is, it is no exaggeration to say that the portion that contributes to the improvement of corrosion resistance is half the plate thickness, and there is a limit to the improvement of the penetration life by adding an element to the core material. Therefore, studies on 4-layer materials or 5-layer materials have been made conventionally. For example, Japanese Patent Laid-Open No. 1-2
08432 and JP-A-5-65582 correspond to this. However, it cannot be said that the conventional technique has sufficiently improved the performance for the following reasons.

That is, since the addition of Cu makes the potential of aluminum noble, it is added to the core material of the brazing sheet for the purpose of improving the corrosion resistance. However, Cu added to the core material diffuses into the molten brazing material during the brazing heat, and is discharged and concentrated in the eutectic part when the brazing material solidifies after the brazing heat. Therefore, as the brazing sheet has more Cu in the core material, the layer in which the brazing material is re-solidified is corroded more quickly. Further, due to the diffusion of Cu to the surface, the potential difference between the core and the surface of the brazing material is reduced, and the core material is less likely to be sacrificed and protected. Further addition of a large amount of Cu increases the intergranular corrosion susceptibility of the core material. Therefore, there is a limit to the amount of elements such as Cu for improving the corrosion resistance of the core material of the brazing sheet.

The inventors of the present invention have made earnest studies to solve this problem, and as a result, in order to improve the corrosion resistance of the brazing sheet member, in order to improve the corrosion resistance of the brazing sheet member, the brazing material is diffused into the core material after the brazing heat is applied and It was found that it is effective to prevent the diffusion of elements such as Cu into the brazing material, and at the same time, it is effective to provide a sacrificial layer that protects the core material. An object of the present invention is to find an Al alloy brazing sheet having excellent corrosion resistance based on the above findings.

[0009]

The invention according to claim 1 for solving the above-mentioned problems is an Al alloy for a heat exchanger which constitutes a tank part and a refrigerant passage by joining a press-molded brazing sheet by vacuum brazing. A brazing sheet made of Mn: 0.5 to 2.0 mas.
s%, Cu: 0.1 to 1.0 mass%, Mg: 0.0
Al containing 5 to 0.5 mass% and Ti: 0 to 0.3 mass% with the balance Al and unavoidable impurities
An alloy core material and an Al-Si-Mg-based brazing material coated on both surfaces with a clad ratio of 5 to 20% on one surface, and a brazing material and a core corresponding to the outer surface of the tank portion and the refrigerant passage. Between materials, Mn: 0.5-2.0 mass
%, Mg: 0.05 to 0.5 mass%, Ti: 0
Containing 0.3 mass%, and further In: 0.05-
Vacuum brazing, characterized in that it is an Al alloy containing 0.5 mass% and the balance being Al and unavoidable impurities and having an intermediate layer having a thickness of 30 μm or more and a cladding rate of 35% or less. It is a brazing sheet made of aluminum alloy for attachment.

The invention of claim 2 is directed to the Al--Si.
The brazing sheet made of an Al alloy for vacuum brazing according to claim 1, wherein the Mg-based brazing material further contains In: 0.05 to 1.0%.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. First, Al for vacuum brazing according to the invention of claim 1
The alloy brazing sheet will be described. The significance of the added elements of the Al alloy used in the core material and the reasons for limiting the range are as follows. Cu is added in an amount of 0.1 to 1.0% in order to improve the corrosion resistance. However, if its content is less than the lower limit, the effect is weak, and if it exceeds the upper limit, intergranular corrosion is easily generated, and the core material of the brazing material is used. Therefore, the corrosion resistance is reduced because the amount of diffusion into the steel increases. Therefore, the range is 0.1-1.
Although it is 0%, it is more preferably 0.15 to 0.5%.

Mn is 0.5 to 2.0 for improving strength.
%, But if it is less than the lower limit value, the effect of improving the strength is small, and if it exceeds the upper limit value, the amount of the brazing material diffused into the core material during the brazing heat is increased, and the brazing property and the corrosion resistance are deteriorated. Therefore, the range is 0.5 to 2.0%, but 0.
It is more preferably set to 8 to 1.5%.

Mg is added in an amount of 0.05-0.
5% is added, but if it is less than the lower limit value, the effect of improving the strength is small, and if it exceeds the upper limit value, the amount of the brazing material diffused into the core material during the brazing heat is increased and the brazing property and the corrosion resistance are deteriorated. Therefore, the range is 0.05-0.5%,
More preferably, it is 0.1 to 0.3%.

If necessary, Ti is added in an amount of 0 to 0.3% in order to improve the corrosion resistance. However, if the addition amount exceeds 0.3%, it becomes difficult to manufacture the material. Further, the lower limit is slightly 0.01% to 0.03% as compared with the case where no addition is made (0%).
% May be added. Whether to add or not is determined by appropriately selecting it according to the application of the product. In addition, when adding, it is more preferable to set it to about 0.05 to 0.2%.

Elements other than those mentioned above and unavoidable impurities in the core material include Si, Fe, Cr, Zn, etc., but generally accepted ranges, that is, Si is 0.6% or less and Fe is 0.7%. Hereinafter, if Cr is 0.2% or less and Zn is 0.4% or less, there is no particular problem. However, Si and Fe are preferably 0.2% or less of Si and 0.2% or less of Fe, if possible.

Next, the significance of the additive elements of the Al alloy used in the intermediate layer of the Al alloy brazing sheet according to the present invention and the reasons for limiting the range will be described. Mn is added in an amount of 0.5 to 2.0% in order to improve the strength, but if it is less than the lower limit value, the effect of improving the strength is small, and if it exceeds the upper limit value, the diffusion amount of the brazing material into the core material during the brazing heat. , Which reduces brazing and corrosion resistance. Therefore, the range is 0.5 ~
Although it is 2.0%, 0.8 to 1.5% is more preferable.

Mg is added in an amount of 0.05-0.
5% is added, but if it is less than the lower limit value, the effect of improving the strength is small, and if it exceeds the upper limit value, the amount of the brazing material diffused into the core material during the brazing heat is increased and the brazing property and the corrosion resistance are deteriorated. Therefore, the range is 0.05-0.5%,
More preferably, it is 0.1 to 0.3%.

Ti is added in an amount of 0 to 0.3% as required to improve the corrosion resistance. However, if the addition amount exceeds 0.3%, it becomes difficult to manufacture the material. Further, the lower limit is slightly 0.01% to 0.03% as compared with the case where no addition is made (0%).
% May be added. Whether to add or not is determined by appropriately selecting it according to the application of the product. When it is added, it is more preferably about 0.05 to 0.2%.
In the invention of claim 2, 0.05 to 1.0% of In is added in order to make the potential base, improve the sacrificial anticorrosive action on the core material, and improve the corrosion resistance of the material, but the addition amount is If it is less than the lower limit, the effect of improving the corrosion resistance is small, and if it exceeds the upper limit, the self-corrosion resistance of the intermediate layer decreases,
This will increase the cost of materials. Therefore, the range is 0.0
Although it is 5 to 1.0%, 0.05 to 0.2% is more preferable. Cu is not added to the intermediate layer. The reason for this is that when Cu is added to the intermediate layer, when heat is added to the solder,
This is because Cu diffuses from the intermediate layer to the brazing material on the outer surface side, and when the brazing material solidifies, Cu is discharged to the eutectic portion and becomes concentrated, thereby deteriorating the corrosion resistance.

Elements other than those mentioned above in the Al alloy material of the intermediate layer, which are inevitable impurities, include Si, Fe, Cr, and Zn.
Etc., but generally accepted range, that is, Si is 0.6
% Or less, Fe 0.7% or less, Cr 0.2% or less, Z
If n is 0.4% or less, there is no particular problem. However, Si,
Regarding Fe, if possible, Si 0.2% or less, Fe 0.
2% or less is preferable.

Next, this Al alloy intermediate layer is provided on one of the core materials, that is, on the surface corresponding to the outside of the tank portion and the refrigerant passage of the heat exchanger, and the brazing material is clad on it. The brazing material is directly clad on the other surface of the core material. The reason why the intermediate layer is provided on the surface corresponding to the outside of the tank portion and the refrigerant passage is that the outside is more severe in the corrosive environment. In the intermediate layer of the Al alloy brazing sheet according to the present invention, the thickness is 30 μm.
The reason why the thickness is set to m or more is that when the thickness of the intermediate layer is less than 30 μm, Cu of the core material passes through the intermediate layer and diffuses to the brazing material when the brazing heat is applied. Cu reaching the brazing material
When the brazing material melts and solidifies, it is discharged to the eutectic part and becomes concentrated, which reduces the corrosion resistance. The reason why the clad ratio of the intermediate layer is 35% or less of the total plate thickness is that if the intermediate layer becomes too thick with respect to the plate thickness, the material strength decreases and molding becomes difficult, and the core material The sacrificial anticorrosion part becomes too large and the remaining plate thickness becomes thin when corrosion progresses,
This is because the internal pressure of the heat exchanger cannot be withstood. Therefore, the intermediate layer has a thickness of 30 μm or more and the cladding rate is 35% or less.

The brazing material used in the present invention is not particularly limited. Al- which is usually used for vacuum brazing
Si-Mg type brazing material, that is, 4004 (typical example Al-10
% Si-1.5% Mg alloy), 4104 (typical example Al-)
10% Si-1.5% Mg-0.1% Bi alloy) or the like can be used. Also, as for the clad rate of the brazing material, a usual clad rate, that is, 5 to 20% per one surface with respect to the total plate thickness can be used. In the case of the present invention, the brazing material is clad on both sides of the plate.

The structure of the Al alloy brazing sheet according to the present invention is as described above. The sectional structure of this sheet (plate) is shown in FIG.
That is, the brazing material 3 is provided on the side C corresponding to the outer surface of the heat exchanger tank portion and the refrigerant passage of the Al alloy core material 5 with the intermediate layer 4 interposed therebetween, and the other side of the core material 5 (corresponding to the inner surface). wax material 3 on the side) ^D, a four-layer structure in which a.

According to a second aspect of the present invention, the brazing material of the Al alloy brazing sheet of the first aspect further contains 0.05 to 0.05% In.
1.0% was added. Since In is discharged to the eutectic part when the brazing material solidifies after the brazing heat, it can neutralize the potential of the eutectic part and further improve the corrosion resistance of the brazing sheet surface after the brazing heat. . If the addition amount is less than the lower limit value, there is no effect, and if the addition amount exceeds the upper limit value, the corrosion resistance of the surface after the brazing addition heat is reduced and the progress of corrosion is promoted. Therefore, the addition amount is set to 0.05 to 1.0%, but since In is added to the intermediate layer, in order to lower the potential of the brazing material from that of the intermediate layer, the addition amount is made larger than that in the intermediate layer, Further, it is more preferable to set it to 0.7% or less. Other requirements are the same as those of the first aspect.

The Al alloy brazing sheet according to the present invention can be manufactured by a conventional method as in the conventional method. That is, a predetermined Al alloy material such as a core material, an intermediate layer material, and a brazing material is melt-cast, the ingot is subjected to homogenizing heat treatment (soaking), and further, if necessary, rolled to a predetermined thickness, and these are combined. It can be manufactured by hot rolling and then cold rolling (annealing if necessary).

[0025]

EXAMPLES Next, examples of the present invention will be described in more detail in comparison with comparative examples and conventional examples. Example 1 Various core materials shown in Table 1 were subjected to soaking treatment, one surface of the core material was matched with an intermediate layer at a clad ratio of 15%, and JIS 4104 alloy was used as a brazing material on both surfaces of the core material.
The brazing sheet having a thickness of 1.0 mm was manufactured by hot rolling, intermediate annealing and cold rolling with 15% per one side. These brazing sheets shown in Table 1 were washed, finish annealed, and then subjected to a vacuum brazing heat of 873 K × 3 minutes in a vacuum of 6.7 × 10 ⁻³ Pa to obtain test materials. One surface (the surface on the side where the intermediate layer was not clad) of these test materials was coated with a resin, and a corrosion test (CASS test) was performed. After 500 hours had passed from the start of the test, the test material was taken out and the surface corrosion product was removed to evaluate the corrosion state of the material. For evaluation, the pitting depth of the maximum pitting portion was measured by the depth of focus method using an optical microscope. For some materials, the corrosion morphology was observed from the cross section. The measurement results are shown in Table 1.

[0026]

[Table 1]

As is clear from Table 1, the brazing sheet according to the present invention is superior in corrosion resistance to the conventional example and the comparative example.

[Example 2] No. 2 shown in Table 1 9 breaks
Change the cladding ratio and plate thickness of the intermediate layer
The brazing sheet with a thickness of 1.0 mm and 0.5 mm
Manufactured. Table 2 shows these various brazing sheets.
Shown in Wash these brazing sheets shown in Table 2,
After finish annealing, 6.7 × 10 ^-3873 in a vacuum of Pa
A vacuum brazing heat was applied for K × 3 minutes to obtain a test material. This
JIS No. 5 test pieces were prepared using these test materials, and tensile strength was increased.
Was measured. Also, one side of the test material (cladding the intermediate layer
Corrosion test (CASS test)
Was carried out. 500 hours after the test started
Remove the test material and remove surface corrosion products to
Eating status was evaluated. Maximum pitting corrosion is evaluated using an optical microscope.
The depth of pitting corrosion was measured by the depth of focus method. This measurement result
The results are also shown in Table 2.

[0029]

[Table 2]

As is clear from Table 2, the brazing sheet according to the present invention has strength comparable to that of the conventional example and the comparative example, and has excellent corrosion resistance.

Example 3 In various brazing sheets shown in Table 1, JIS 4104 alloy was added to the alloy.
A brazing sheet having a thickness of 1.0 mm was manufactured by replacing the brazing filler metal added with 03 to 1.2% In. Table 3 shows the details of these brazing sheets. After cleaning and finishing annealing these brazing sheets shown in Table 3,
Vacuum brazing heat was applied for 873 K × 3 minutes in a vacuum of 6.7 × 10 ⁻³ Pa to obtain a test material. A corrosion test (CASS test) was carried out by coating one surface (the surface on the side where the intermediate layer is not clad) of these test materials with a resin. After 500 hours had passed from the start of the test, the test material was taken out and the surface corrosion product was removed to evaluate the corrosion state of the material. For evaluation, the pitting depth of the maximum pitting portion was measured by the depth of focus method using an optical microscope. Table 3 also shows the measurement results.

[0032]

[Table 3]

As is clear from Table 3, the brazing sheet according to the present invention (claim 2) is superior in corrosion resistance to the conventional example. In addition, the core material and the intermediate layer have the same composition,
The corrosion resistance is superior to that of the comparative example in which the addition amount of is out of the range of the present invention (claim 2).

[0034]

As described in detail above, the present invention can significantly improve the corrosion resistance of one side of a corrosive environment which is severe in the use of an Al alloy brazing sheet. In this case, the corrosion life of the heat exchanger can be remarkably improved, and this has an industrially remarkable effect.

[Brief description of drawings]

FIG. 1 is a plan view showing a molded member for a drone cup evaporator.

FIG. 2 is a sectional view taken along line BB in FIG.

FIG. 3 is an enlarged cross-sectional view of a portion A of the member of FIG. 2, showing a cross-sectional structure of a conventional Al alloy brazing sheet.

FIG. 4 is an explanatory view showing an example of a heat exchanger (Drone cup evaporator), and is a schematic sectional view thereof.

FIG. 5 is a diagram showing a cross-sectional structure of an Al alloy brazing sheet according to the present invention.

[Explanation of symbols]

1 Refrigerant passage constituent member for a drone cup evaporator 2 Fins 3 Brazing material layer 4 Intermediate layer 5 Core material layer 6 Side plate 7 Refrigerant inlet pipe 8 Refrigerant outlet pipe 10 Heat exchanger (dron cup evaporator) C Heat exchanger tank part And the side corresponding to the outer surface of the refrigerant passage D The side corresponding to the tank section of the heat exchanger and the inner surface of the refrigerant passage

Claims (2)

[Claims] 1. An Al alloy brazing sheet for a heat exchanger, which comprises a press-molded brazing sheet joined by vacuum brazing to form a tank portion and a refrigerant passage, the composition of which is Mn: 0.5 to 2 0.0 mass%,
Cu: 0.1 to 1.0 mass%, Mg: 0.05 to
Al alloy core material containing 0.5 mass% and Ti: 0 to 0.3 mass% and the balance of Al and unavoidable impurities, and Al coated on both surfaces thereof with a clad ratio of 5 to 20% on one surface. -Si-Mg based brazing filler metal,
Further, between the brazing material and the core material corresponding to the outer surface of the tank portion and the refrigerant passage, Mn: 0.5 to 2.0 mass%, M
g: 0.05 to 0.5 mass%, Ti: 0 to 0.3 m
%, and further In: 0.05-0.5 ma
For vacuum brazing, characterized by being an Al alloy containing ss% and the remainder being Al and inevitable impurities, having an intermediate layer with a thickness of 30 μm or more and a clad ratio of 35% or less. Al alloy brazing sheet. 2. The brazing sheet made of an Al alloy for vacuum brazing according to claim 1, wherein the Al—Si—Mg brazing material further contains In of 0.05 to 1.0 mass%.