JPH07116544B2 - High strength and corrosion resistant aluminum alloy clad material for heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to 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. Suitable for use as a tube material or header plate material,
The present invention relates to an Al alloy clad material having good brazing property and having high strength and high corrosion resistance after brazing, and is particularly suitable for a tube material used with a thin wall.

[Prior Art] For tube materials and header plate materials such as automobile radiators and heater cores, Al-Mn alloys such as 3003 are used as core materials, and Al-Si alloy brazing material is used on one side and the other side. Al
A three-layer clad material in which a sacrificial anode material such as a -Zn alloy or an Al-Zn-Mg 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. The other side clad with the sacrificial anode material becomes an inner side (water side) during use, and exhibits 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, 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 a bonding failure occurs. Thus
The amount of Mg added to the core material is 0.5% at the maximum, 0.2 for practical use
It is limited to 0.3%, which hinders high strength.

The strength of the tube material and header plate material may also 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 adding Mg and Zn to the sacrificial anode material of the radiator header plate material or tube material (Japanese Patent Publication No. 63-28704), a method of adding Zn and Mg (Japanese Patent Publication No. 61-89498), A method of simultaneously adding Sn and Mg (JP-A-56-16646, JP-A-63-89641) and a method of adding Mg and Zn to a relatively high concentration (JP-B-62-62).
−45301), has been proposed.

However, the addition of Mg above and 1.1% or 1.5
% Or less, it is added to prevent pitting and crevice corrosion, and strength cannot be improved.

The above Mg addition suppresses the grain boundary diffusion of Sn, the purpose of preventing cracking during hot rolling, the addition of the above Mg is intended to improve the pitting corrosion resistance, both Mg In the case of a high concentration, there is a possibility that it diffuses into the core material and some strength improvement effect is obtained. However, when a thin tube material (cladding material) is made, even if the strength of the core material can be increased by the Mg diffused from the sacrificial anode material, the strength of the sacrificial anode material is Mg.
Addition alone is insufficient, and the strength of the entire clad material 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.

[Problems to be Solved by the Invention] Therefore, the present invention provides a clad material 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 the one we are trying to provide.

[Means for Solving the Problems] The inventors of the present invention investigated a method for obtaining high strength after brazing while keeping the amount of Mg added in the core material at a maximum of 0.5%, and found that the high sacrificial anode material had a high strength. When a concentration of Mg and Si is added, part of the Mg in the sacrificial anode material diffuses into the core material during brazing, strengthening the core material, and the sacrificial anode material itself also contains Mg and Si.
The present invention was completed by finding out that it was strengthened by.

That is, coexistence of Mg and Si in the sacrificial anode material, contributing Mg to strengthen the core material, and strengthening the sacrificial anode material by solid solution strengthening with Mg and Si and age hardening by precipitation of Mg ₂ Si. is there.

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.
2 to less than 0.7%, Mg: containing 0.5% or less, composed of an aluminum alloy consisting of balance Al and unavoidable impurities, the sacrificial anode material compounded on one side of the core material Mg: 1.2 to 2.5%, Si: 0.2
~ 0.8%, the balance is composed of an aluminum alloy consisting of Al and unavoidable impurities, and the skin material composited on the other side of the core material is composed of a brazing material of Al-Si alloy. Characteristically high strength and corrosion resistant aluminum alloy clad material for heat exchanger, (2) core material is Mn: 0.3-2.0%, Cu: 0.25-0.8%, Si: 0.
2 to less than 0.7%, Mg: containing 0.5% or less, composed of an aluminum alloy consisting of balance Al and unavoidable impurities, the sacrificial anode material compounded on one side of the core material Mg: 1.2 to 2.5%, Si: 0.2
~ 0.8%, In: 0.2% or less, Sn: 0.2% or less, and Ga: 0.2% or less, and is composed of an aluminum alloy containing the balance Al and unavoidable impurities. And, the skin material composited 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, characterized by being composed of a brazing material of a Si-based alloy.

[Operation] The reasons 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 and the potential difference with the sacrificial anode material is increased to improve the corrosion resistance. 0.3
If it is less than%, the effect is not sufficient, and if it exceeds 2.0%, a coarse compound is formed 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 effect of the sacrificial anode material and the brazing material due to the sacrificial anode effect. Further, Cu in the core material diffuses into the sacrificial anode material and the brazing material during brazing to form a gentle concentration gradient, and the noble potential on the core 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 anticorrosion effect and strength improving effect of Cu shown above are
If the Cl content is less than 0.25%, it will not be exhibited. On the other hand, if it exceeds 0.8%, the corrosion resistance of the core material itself will deteriorate and the melting point of the core material will decrease, causing localized melting 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 increases the strength by age hardening after brazing. If it is less than 0.2%, the effect is not sufficient, and if it is more than 0.7%, the corrosion resistance is reduced 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. The effect of improving strength is more effectively exhibited by age hardening after brazing when coexisting with Si and / or Cu. However, the amount is 0.5
If it exceeds%, it reacts with the fluoride flux to hinder the brazing property, or Mg fluoride is generated to impair the appearance.

Other elements: Fe, Zn, Cr, Zr and the like may be contained 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 it must be 0.7% or less. Since Zn makes the potential of the core material base and reduces the potential difference between the sacrificial anode material and the brazing material, it must be 0.2% or less.

(2) Sacrificial anode material Mg: A part of Mg in the sacrificial anode material diffuses mainly into the brazing material into the core material, 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. Furthermore, the sacrificial anode effect is ensured by making the potential of the sacrificial anode material base.
If it is less than 1.2%, the effect is not sufficient, and if it exceeds 2.5%, local melting occurs during brazing.

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 diffuses in large amounts to the brazing material side, impeding brazing properties. There is nothing to do. 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 Crag material. In particular, age hardening occurs together with Mg remaining in the sacrificial anode material, which contributes to the improvement of strength. 0.2
If it is less than%, the effect is not sufficient, and if it exceeds 0.8%, local melting occurs during brazing.

In, Sn, Ga: In, Sn, Ga make the electric potential of the sacrificial anode material base by adding a trace amount and ensure the sacrificial anode effect on the core material. As a result, pitting corrosion and crevice corrosion of the core material are prevented. If the content exceeds the upper limit, the self-corrosion resistance and the rolling workability are deteriorated, the diffusion at the time of brazing is increased, and the sacrificial anode layer becomes thick. When a small amount of these elements is added, the diffusion is not fast unlike the case of Zn, and therefore the thickness of the diffusion layer after brazing does not become much larger than the thickness of the sacrificial anode material before brazing. Therefore, the thickness of the corrosion allowance can be controlled arbitrarily and small. Therefore, the clad material can be made thinner.

(3) Brazing material The brazing material is a commonly used Al-Si alloy. Usually 6 to 13
An Al alloy containing% Si is used.

[Examples] The present invention will be specifically described with reference to Examples below.

Ingots of core alloy shown in Table 1 below, alloy for sacrificial anode material shown in Table 2 and alloy 4045 for brazing material were prepared, and homogenization treatment was performed on the alloy for core material and the alloy for sacrificial anode material. went. 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 and hot-rolled to obtain a clad material. afterwards,
A plate (H14 material) having a thickness of 0.25 mm was prepared by cold rolling, intermediate annealing and cold rolling. The composition of the clad material is 0.0
The sacrificial anode material was 0.030 to 0.050 mm with a constant 25 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
A 0.10 mm-thick corrugated fin made of a% Zn alloy was put on and brazed in a nitrogen gas using a fluoride flux. The brazing temperature (material temperature) was 600 ° C. After brazing, the joining state of the plate material and the fin, and the melting state of the core material and the sacrificial anode material were examined.

Next, a plate material having a thickness of 0.25 mm was heated as it is (without being brought into contact with the fins) under the same conditions as in the fluoride flux brazing, and then a tensile test and a corrosion test were performed. The corrosion test method is CASS test for the outer surface (brazing material side) for 30 days, and Cl-100ppm, SO for the inner surface (sacrificial anode material side).
_{^{4 2- 100ppm, HCO 3 - 100ppm}} , immersed in an aqueous solution containing Cu ²⁺ 10 ppm, heated to 80 ° C. during -8 hr, then repeat cycle that 16hr left to cool to room temperature, repeated three months It was

The above results are summarized in Table 3. In Invention Examples Nos. 1 to 17, the brazing property is good, the tensile strength is as high as 17 kgf / mm ² or more, and the maximum corrosion depth is small.

In the case of Comparative Example No. 18, the tensile strength is low because the sacrificial anode material has a small amount of Mg.

Comparative Example No. 19 has a large amount of Mg, so that local melting occurs during brazing.

Comparative Example No. 20 has low tensile strength because the sacrificial anode material has a small amount of Si.

Since Comparative Example No. 21 has a large amount of Si, local melting occurs during brazing.

Comparative Examples Nos. 22, 23, and 24 have large amounts of In, Sn, or Ga, and therefore have a large corrosion depth on the inner surface side.

No. 25 has a low tensile strength due to a small amount of Mn in the core material.
No. 26 does not have a healthy plate material due to the large amount of Mn in the core material.

No. 27 has a low tensile strength due to a small amount of Cu in the core material, and has a large corrosion depth on the outer surface side.

No. 28 has a large amount of Cu in the core material, so that melting occurs during brazing.

No. 29 has a low tensile strength because the core material is low in Si.

No. 30 has a large amount of Si in the core material, so that melting occurs during brazing.

No. 31 has a low tensile strength because the core material does not contain Mg.

No. 32 has a brazing defect due to the large amount of Mg in the core material.

In No. 33, the core material is 3003, so the tensile strength is low and the corrosion depth on the outer surface side is large.

[Effects of the Invention] As described above, the clad material of the present invention has high strength and corrosion resistance as a material for fluoride flux brazing, and
It is an Al heat exchanger clad material with excellent brazing properties. 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 the Mg concentration distribution after brazing of the material of the present invention.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location F28F 21/08 (72) Inventor Kenji Kato 3-12-12, Chiennen, Minato-ku, Nagoya, Aichi Light Metal Industry Co., Ltd. Technical Research Institute (72) Inventor Naoki Tokizo 3-12 Hosetsu, Minato-ku, Nagoya, Aichi Prefecture 3-12, Japan Sumitomo Light Metal Industry Co., Ltd. Technical Research Center (3-12) (56) References JP-A-63-303027 (JP, A) JP-A-54-110909 (JP, A)

Claims (2)

[Claims] 1. A core material is Mn: 0.3 to 2.0% (weight%, hereinafter the same), Cu: 0.25 to 0.8%, Si: 0.2 to less than 0.7%, Mg: 0.5%
The sacrificial anode material containing the following and composed of an aluminum alloy consisting of the balance Al and inevitable impurities, and the sacrificial anode material compounded on one side of the core material contains Mg: 1.2 to 2.5%, Si: 0.2 to 0.8%, and the balance Al.
And an aluminum alloy consisting of inevitable impurities,
A high-strength and high-corrosion-resistant aluminum alloy clad material for a heat exchanger, characterized in that a skin material compounded on the other surface of the core material is composed of a brazing material of an Al-Si alloy. 2. The core material is Mn: 0.3 to 2.0%, Cu: 0.25 to 0.8
%, Si: 0.2 to less than 0.7%, Mg: 0.5% or less, balance A
The sacrificial anode material composed of an aluminum alloy consisting of 1 and unavoidable impurities and composited on one surface of the core material has a Mg: 1.2-2.
5%, Si: 0.2-0.8%, In: 0.2% or less, S
A skin material containing one or more of n: 0.2% or less and Ga: 0.2% or less, composed of an aluminum alloy consisting of the balance Al and inevitable impurities, and composited on the other side of the core material. Is a brazing material of Al-Si alloy, a high strength and high corrosion resistance aluminum alloy clad material for heat exchangers.