JPH05230577A - High strength and high corrosion resistance aluminum alloy clad material for heat exchanger - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a clad material having high strength after brazing without impairing the brazing property. [Structure] Core material is Mn: 0.3 to 2.0%, Cu:
0.25-0.8%, Si: 0.05-1.0%, M
g: 0.5% or less, Ti: 0.35% or less, and a balance of Al and an Al alloy composed of unavoidable impurities. The composition of the sacrificial anode material compounded on one side of the core material is Mg:
1.0 to 2.5%, Si: 0.05 or more and less than 0.20%, optionally Zn: 3.0% or less, and the balance Al, which was compounded on the other side of the core material. A high-strength and high-corrosion-resistant Al alloy for a heat exchanger whose skin material is a brazing material of an Al-Si alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tube which is a structural member for manufacturing an Al heat exchanger such as a radiator or a heater core by brazing using a fluoride flux in an inert gas atmosphere or vacuum brazing. The present invention relates to an Al alloy clad material which is suitable for use as a material or header plate material, has good brazing properties, and has high strength and high corrosion resistance after brazing, and is particularly suitable for a thin tube material used.

[0002]

2. Description of the Related Art A tube material such as a radiator and a heater core of an automobile and a header plate material are made of an Al-Mn alloy such as 3003 as a core material, an Al-Si alloy brazing material on one side, and another surface on the other side. Al-Zn alloy and Al-Zn
A three-layer clad material in which a sacrificial anode material of a Mg-based alloy is clad is used. The Al-Si type brazing material is used for joining the tube to the fin and joining the tube to the header plate. Brazing is often performed using a fluoride flux in an inert gas atmosphere or vacuum brazing. The other side clad with the sacrificial anode material becomes an inner side (water side) during use and exerts a sacrificial anode function to prevent pitting and crevice corrosion of the core material.

In recent years, there has been a strong demand for weight reduction of radiators and heater cores, and it has become necessary to reduce the thickness of tube materials and header plate materials. For that purpose, it is necessary to increase the strength of the material, especially the strength after brazing, and in order to increase the strength, Mg is often added to the core material. However, Mg reduces the corrosion resistance and
Brazeability is impaired. That is, in the case of fluoride flux brazing, since Mg diffuses to the surface during brazing and reacts with the fluoride flux, a cotton-like product (fluoride of Mg) is produced and adheres, or is bonded. It causes defects.
Also, in the case of vacuum brazing, the brazing property is impaired. In this way, the amount of Mg added to the core material is limited to 0.5% at the maximum and 0.2 to 0.3% in practical use, which hinders high strength. The strength of the tube material and header plate material is
It may be improved by adding Mg to the sacrificial anode material. There have been some proposals for the clad material in which Mg is added to the sacrificial anode material.

That is, a method of containing Mg and Zn in a sacrificial anode material such as a header plate material for a radiator or a tube material (Japanese Patent Publication No. 63-28).
No. 704), a method of adding Zn and Mg (Japanese Patent Laid-Open No. 61-8949).
No. 8), a method of simultaneously adding Sn and Mg (JP-A-56-16).
646, JP-A-63-89641), a method of adding Mg and Zn to a relatively high concentration (JP-B-62-45301), and a method of adding Mg or Mg and Zn (JP-A-2-175093). ), Are proposed.

However, the above-mentioned additions of Mg and Mg are as small as 1.1% or 1.5% or less, and they are added to prevent pitting corrosion and crevice corrosion, and strength cannot be improved.

The above-mentioned addition of Mg is intended to suppress the grain boundary diffusion of Sn and prevent cracking during hot rolling, and the above-mentioned addition of Mg is intended to improve pitting corrosion resistance. However, when Mg has a high concentration, there is a possibility that it will diffuse into the core material and some strength improvement effect can be obtained. Also,
The above is intended to improve the strength by diffusing Mg into the core material. However, when a thin tube material (clad material) is made, even if the strength of the core material can be increased by the Mg diffusing from the sacrificial anode material, the strength of the sacrificial anode material is insufficient only by adding Mg, and the strength of the entire clad material is reduced. The strength cannot be increased. That is, when the thickness is reduced, the contribution to the strength of not only the core material but also the sacrificial anode material is large, and it is necessary to increase the strength of the sacrificial anode material.

[0007]

SUMMARY OF THE INVENTION Therefore, the present invention provides a clad that does not impair the brazing property, that is, keeps the amount of Mg added to the core material to a maximum of 0.5% and obtains high strength after brazing. It is intended to provide wood.

[0008]

Means for Solving the Problems The inventors of the present invention have investigated a method for obtaining high strength after brazing while keeping the amount of Mg added in the core material to a maximum of 0.5%, and If a high concentration of Mg and Si is added to the
A part of g will diffuse into the core material during brazing to strengthen the core material, and the sacrificial anode material itself will be strengthened by Mg and Si. Further, Si in the sacrificial anode material will increase. Intergranular corrosion occurs when the cooling rate after attachment is low.
The inventors have found that intergranular corrosion can be prevented by adjusting the amount of a suitable amount to complete the present invention.

That is, in the sacrificial anode material, Mg and Si to the extent that the corrosion resistance is not present are made to coexist to contribute to the strengthening of the core material, while the sacrificial anode material is solid solution strengthened by Mg and Si and the precipitation of Mg ₂ Si. It is reinforced by age hardening by.

That is, in the constitution of the present invention, (1) the core material is Mn: 0.3 to 2.0%, Cu: 0.25 to 0.8
%, Si: 0.05 to 1.0%, Mg: 0.5% or less,
Ti: 0.35% or less, a balance sacrificial anode material composed of an aluminum alloy consisting of balance Al and unavoidable impurities, and one side of the core material is Mg: 1.0 to 2.5%, S
i: 0.05% or more and less than 0.20%, an aluminum alloy composed of the balance Al and unavoidable impurities, and a skin material compounded on the other surface of the core material is Al-Si.
A high-strength and high-corrosion-resistant aluminum alloy clad material for heat exchangers, which is composed of a brazing material of a series alloy. (2) The core material is Mn:
0.3-2.0%, Cu: 0.25-0.8%, Si:
0.05-1.0%, Mg: 0.5% or less, Ti: 0.35
% Or less and is composed of an aluminum alloy consisting of balance Al and unavoidable impurities, and the sacrificial anode material compounded on one surface of the core material is Mg: 1.0 to 2.5%, Si: 0.05 or more and 0 or more. Less than 20%, Zn: 3.0% or less, is composed of an aluminum alloy consisting of the balance Al and unavoidable impurities, and the skin material compounded on the other side of the core material is Al.
A high-strength and high-corrosion-resistant aluminum alloy clad material for a heat exchanger, which is composed of a brazing material of a Si-based alloy.

[0011]

The reason for limiting the composition and composition range in the present invention will be described.

(1) Core material Mn: Mn improves the strength. Further, the potential of the core material is made noble to increase the potential difference from the sacrificial anode material to improve the corrosion resistance. If it is less than 0.3%, the effect is not sufficient, and if it exceeds 2.0%, a coarse compound is generated during casting, and a sound plate material cannot be obtained.

Cu: Cu makes the potential of the core material noble, increases the potential difference between the sacrificial anode material and the brazing material and the core material, and enhances the anticorrosion action by the sacrificial anode effect of the sacrificial anode material and the brazing material. Further, Cu in the core material diffuses into the sacrificial anode material and the brazing material at the time of brazing to form a gentle concentration gradient, and the noble potential on the core material side and the surface side of each of the sacrificial anode material and the brazing material are base. A potential is applied, and a gentle potential distribution is formed between them to make the corrosion form a general corrosion type.

Cu in the core material also contributes to the improvement of strength.

The above-described anticorrosion effect and strength improving effect of Cu are not exhibited when the amount of Cu in the core material is less than 0.25%, while when it exceeds 0.8%, the corrosion resistance of the core material itself is poor. As a result, the melting point of the core material lowers, and local melting occurs during brazing.

Si: Si improves the strength of the core material. In particular, coexistence with Mg that diffuses from the sacrificial anode material during brazing further increases the strength due to age hardening after brazing. If it is less than 0.05%, the effect is not sufficient.
If it exceeds 0%, the corrosion resistance is lowered and the melting point of the core material is lowered to cause local melting during brazing.

Mg: Mg has the effect of improving the strength of the core material, but deteriorates the brazing property. Therefore, the Mg content in the core material needs to be 0.5% or less. That is, in the case of fluoride flux brazing, Mg is 0.5%.
If it exceeds the range, it reacts with the fluoride flux to hinder the brazing property, or Mg fluoride is generated to deteriorate the appearance of the brazed portion. In the case of vacuum brazing, Mg is 0.5
If it exceeds%, the wax will easily erode the core material.

Ti: Ti further improves the corrosion resistance of the core material. That is, Ti is divided into a high-concentration region and a low-concentration region, and these are alternately distributed in the plate thickness direction to form a layer,
A region where the Ti concentration is low is preferentially corroded as compared with a region where the Ti concentration is high, so that the corrosion form is layered. As a result, the progress of corrosion in the plate thickness direction is prevented, and the pitting corrosion resistance of the material is improved. If it exceeds 0.35%, a coarse compound is generated during casting, and a sound plate material cannot be obtained. Other elements: Fe, Z
n, Cr, Zr and the like may be included within a range that does not impair the effects of the present invention. However, if Fe is contained in a large amount, the corrosion resistance is impaired, so the Fe content is preferably 0.7% or less. Zn
Is preferably 0.2% or less because the potential of the core material is made base and the potential difference between the sacrificial anode material and the brazing material is reduced.

(2) Sacrificial anode material Mg: A part of Mg in the sacrificial anode material diffuses into the core material mainly during brazing, and improves the strength of the core material together with Si and Cu in the core material. Further, Mg remaining in the sacrificial anode material improves the strength of the sacrificial anode material together with Si. And these effects contribute to the improvement of the strength of the entire clad material. If it is less than 1.0%, the effect is not sufficient, and if it exceeds 2.5%, local melting occurs during brazing, which is not preferable.

Although Mg in the sacrificial anode material diffuses into the core material during brazing, it has a concentration distribution as shown in FIG. 1, and a large amount diffuses to the brazing material side, resulting in brazing property. Does not hinder. Needless to say, diffusion also occurs during the production of the clad, and there is a slight concentration distribution at the boundary between the core material and the sacrificial anode material.

Si: Si improves the strength of the sacrificial anode material and contributes to the strength of the entire clad material. In particular, age hardening occurs together with Mg remaining in the sacrificial anode material,
Contributes to strength improvement. If it is less than 0.05%, the effect is not sufficient. As the amount of Si increases, the strength increases, but 0.20%
In the above case, intergranular corrosion occurs in the sacrificial anode material and immediately below it when the cooling rate after brazing is low.

Zn: Zn makes the potential of the skin material base and ensures the sacrificial anode effect. In other words, the mode of corrosion is set to the general corrosion type to suppress pitting corrosion and crevice corrosion. If it exceeds 3.0%, the self-corrosion resistance decreases and the corrosion rate increases.

Other elements: Fe, Cu, Mn, Ti,
Cr, Zr and the like may be included within a range that does not impair the effects of the present invention. However, if Cu and Mn are contained in a large amount, the potential of the sacrificial anode material becomes noble, so 0.05% and 0.5% respectively.
The following is preferable.

(3) Brazing material The brazing material is an Al-Si type alloy which is usually used. Usually, an Al alloy containing 6 to 13% of Si is used. In the case of vacuum brazing, Al-Si-Mg alloy or Al-Si-M
A g-Bi alloy or the like is used.

[0025]

EXAMPLES The present invention will be specifically described with reference to the following examples.

Ingots of alloy for core material shown in Table 1 below, alloy for sacrificial anode material shown in Table 2 and alloy 4045 for brazing material were prepared, and the alloy for core material and the alloy for sacrificial anode material were homogeneous. The chemical treatment was performed. Then, the alloy for the sacrificial anode material and the alloy for the brazing material were hot-rolled to a predetermined thickness, and these and the ingot of the alloy for the core material were combined to obtain a clad material by hot-rolling. Then, a plate (H14 material) having a thickness of 0.25 mm was produced by cold rolling, intermediate annealing and cold rolling.
The clad material had a core material of 0.20 mm, and each of the sacrificial anode material and the brazing material was 0.025 mm.

The alloy composition of each material and its combination are shown in Table 3.

On the brazing material side of the obtained clad plate material, Al
-1.2% Mn-1.5% Zn alloy thickness 0.1
A 0 mm corrugated fin was placed and brazing was performed in a nitrogen gas using a fluoride flux. The brazing temperature (material temperature) was 600 ° C. After brazing, the joining condition between the plate and the fin and the generation condition of the cotton-like product were visually observed, and the melting condition of the core material and the sacrificial anode material was examined by the cross-section metallographic structure.

Next, the plate material having a thickness of 0.25 mm is heated as it is (without being brought into contact with the fins) under the same conditions as the brazing with the fluoride flux, and then at 50 ° C./min and 15
It was cooled at a rate of ° C / min, and a tensile test and a corrosion test were performed. Corrosion test method is for outer surface (brazing material side)
CASS test, and 30 days, for the inner surface (sacrificial anode material _{^{side) Cl - 100ppm, SO 4 2-}} 100ppm, HC
O ₃ ^- 100 ppm, was immersed in an aqueous solution containing Cu ²⁺ 10 ppm, heated to between 88 ° C. of -8 hr, then repeat cycle that 16hr left to cool to room temperature,
I went there for 3 months. The above results are summarized in Table 3.
In the case of Inventive Examples No. 1 to 18, the brazing property is good, the tensile strength after brazing is as high as 17 kgf / mm ² or more, and the corrosion depth on the inner surface side and the outer surface side is high regardless of the cooling rate after brazing. The size is small.

In the case of Comparative Example No. 19, the sacrificial anode material Mg
As a result, the tensile strength is as low as 14 kgf / mm ² .

In Comparative Example No. 20, since a large amount of Mg caused local melting during brazing, other tests were stopped.

Comparative Example No. 21 has a low tensile strength of 15 kgf / mm ² because the sacrificial anode material contains a small amount of Si.

Since Comparative Example No. 22 contains a large amount of Si, intergranular corrosion occurs when the cooling rate after brazing becomes small.

In Comparative Example No. 23, since the sacrificial anode material contains a large amount of Zn, the inner surface has a large corrosion depth of 0.17 to 0.18 mm.

No. 24 has a low tensile strength of 14 kgf / mm ² due to a small amount of Mn in the core material, and No. 25 has a large amount of Mn in the core material, so a sound plate material cannot be obtained and the test was interrupted. did.

No. 26 has a low tensile strength of 15 kgf / mm ² due to a small amount of Cu in the core material, and a large corrosion depth of 0.19 to 0.20 mm on the outer surface side.

With respect to No. 27, melting occurred during brazing due to the large amount of Cu in the core material, so other tests were stopped.

No. 28 has a low tensile strength of 15 kgf / mm ² because the core material is low in Si.

For No. 29, melting occurred during brazing due to the large amount of Si in the core material, so other tests were stopped.

No. 30 has a low tensile strength of 14 kgf / mm ² because the core material does not contain Mg.

No. 31 has a brazing defect due to a large amount of Mg in the core material.

In No. 32, since the core material does not contain Ti, the corrosion depth on the outer surface side is slightly large at 0.12 to 0.13 mm.

In No. 33, since the core material had a large amount of Ti, a sound plate material could not be obtained, and the test was interrupted. No. 34, whose core material is 3003, has a low tensile strength of 12 kgf / mm ² and a large corrosion depth of 0.22 to 0.23 mm on the outer surface side.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

[Table 4]

[0048]

As described above, the clad material of the present invention is a material for fluoride flux brazing or vacuum brazing, which has high strength and corrosion resistance, and particularly excellent corrosion resistance even if the cooling rate after brazing is small. Al with excellent brazing property
It is a clad material for heat exchangers. As a result, the tube material and the header plate material can be made thin, and the weight of the radiator and the heater can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a Mg concentration distribution after brazing of a material of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kenji Kato 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industry Co., Ltd. (72) Inventor Mitsuo Hashiura 1-1-1, Showa-cho, Kariya city, Aichi prefecture Inside Nippondenso Co., Ltd. (72) Inventor Atsushi Fukuda 1-1, Showa-cho, Kariya city, Aichi Prefecture Inside Nihondenso Co., Ltd.

Claims (2)

[Claims] 1. A core material comprising: Mn: 0.3 to 2.0% (weight%, the same hereinafter), Cu: 0.25 to 0.8%, Si:
0.05 to 1.0%, Mg: 0.5% or less, Ti: 0.
A sacrificial anode material containing 35% or less and composed of an aluminum alloy consisting of balance Al and unavoidable impurities, and compounded on one surface of the core material is Mg: 1.0 to 2.5%, Si: 0.0
5 or more and less than 0.20%, and is composed of an aluminum alloy composed of balance Al and unavoidable impurities, and the skin material compounded on the other surface of the core material is composed of a brazing material of Al-Si alloy. A high-strength, high-corrosion-resistant aluminum alloy clad material for heat exchangers. 2. The core material is Mn: 0.3 to 2.0% (weight%, the same applies hereinafter), Cu: 0.25 to 0.8%, Si:
0.05-1.0%, Mg: 0.5% or less, Ti: 0.35
% Or less, and a sacrificial anode material composed of an aluminum alloy consisting of the balance Al and unavoidable impurities and compounded on one surface of the core material, Mg: 1.0 to 2.5%, Si: 0.05 to 0. Less than 20%, Zn: 3.0% or less, is composed of an aluminum alloy consisting of the balance Al and unavoidable impurities, and the skin material compounded on the other side of the core material is Al.
-A high-strength and high-corrosion-resistant aluminum alloy clad material for a heat exchanger, which is composed of a brazing material of a Si-based alloy.