JP2000144290A - Aluminum alloy sacrificial anode material for heat exchanger and high corrosion resistant aluminum alloy composite material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy composite material for heat exchanger having excellent corrosion resistance even under any of an acidic and alkaline corrosive environment. SOLUTION: An aluminum alloy sacrificial anodic material consisting of 3.1-12.0 wt.% Zn, 0.05-0.3 wt.% Zr and the balance Al with inevitable impurities is clad on one surface of an aluminum alloy core material consisting of 0.005-1.2 wt.% Si, 0.005-0.8 wt.% Fe, 0.003-1.2 wt.% Cu, 0.5-2.0 wt.% Mn and the balance Al with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy composite material applicable to both acidic and alkaline refrigerants, and an aluminum alloy sacrificial anode suitable for a tube tube of an automotive heat exchanger manufactured by brazing. It is about materials.

[0002]

2. Description of the Related Art A radiator of a heat exchanger for automobiles has, for example, a structure shown in FIGS. 1 (a) and 1 (b). A header plate (3) is attached to each end of the tube (1) to assemble a core (4), and after the assembly is brazed, a resin tank (6) is attached to the header plate (3) via a packing (5). 7) is attached, and has a structure in which the refrigerant is cooled by passing the refrigerant through the tube tube (1). The side surface of the core (4) is reinforced by a side plate (not shown).

Here, the fins are made of JIS-3003 alloy (Al-
A thin plate having a thickness of about 0.1 mm obtained by adding about 1.5 wt% of Zn to 0.15 wt% Cu-1.1 wt% Mn) is used. The tube tube has a core material of JIS-3003 alloy, a brazing material on one surface and a JIS-7072 alloy (Al-1.0wt% Zn) clad on another surface as a sacrificial anode material for preventing pitting corrosion. An aluminum alloy composite material (brazing sheet) having a thickness of 0.2 to 0.4 mm, which is subjected to electric resistance welding in a tubular shape with the sacrificial anode material inside (coolant side) is used. In addition, the header plate has a thickness of 1.
An aluminum alloy composite of the same material as the tube tube of 0 to 1.3 mm is used.

[0004] In recent years, the weight of the heat exchanger has been required to be reduced. However, when the thickness of the member is reduced in order to reduce the weight of the heat exchanger, it is necessary to improve the corrosion resistance of the member. Until now, only corrosion resistance in an acidic environment has been considered so far.However, recently, an alkaline refrigerant is sometimes used, so for the purpose of improving corrosion resistance not only in an acidic environment but also in an alkaline corrosive environment, An aluminum alloy composite material in which an additive element is further added to a sacrificial anode material has been proposed (Japanese Patent Application Laid-Open No. Hei 9-176768).

[0005]

However, it has been found that the conventional aluminum alloy composite material has insufficient corrosion resistance in an alkaline corrosion environment. The following two points cause the corrosion resistance of the aluminum alloy composite to decrease in an alkaline corrosive environment. That is, one is that under a certain alkaline environment, a film of aluminum hydroxide is formed on the surface of the sacrificial anode material, and in the presence of such a film, the sacrificial anode material loses its anticorrosion effect on the core material. Is to put it. The other is that, in an alkaline environment exceeding pH 10, the natural potential of the Al-Mn-based alloy largely shifts to the lower side, so that in the conventional Al-Zn sacrificial anode material (Zn content is 1 to 3 wt%), The potential relationship between the Al-Mn alloy core material and the sacrificial anode material is reversed, and the sacrificial anode material loses its anticorrosion action.

Accordingly, the present inventors have conducted intensive studies and studied the components of the sacrificial anode material to obtain an aluminum alloy sacrificial anode material having an excellent sacrificial anode effect under both acidic and alkaline environments. The present inventors have also found that by examining the sacrificial anode material and the core material components, it is possible to realize an aluminum alloy composite material having excellent corrosion resistance under both acidic and alkaline corrosion environments.

That is, an object of the present invention is to provide an aluminum alloy sacrificial anode material having a sufficient sacrificial anticorrosive action under both acidic and alkaline corrosion environments, and an aluminum alloy composite material for a heat exchanger having excellent corrosion resistance. is there.

[0008]

Accordingly, the aluminum alloy sacrificial anode material for a heat exchanger according to the present invention comprises Zn 3.1 to 12.
0 wt%, Zr 0.05-0.3 wt%, or further Mn 0.5-2.0 wt%, In 0.002-0.3 wt%
% Or 0.002 to 0.3 wt% of Sn, and the balance consists of Al and inevitable impurities. Next, the high corrosion-resistant aluminum alloy composite material for a heat exchanger of the present invention contains Si 0.005 to 1.2 wt%,
Fe 0.005 to 0.8 wt%, Cu 0.003 to 1.2
wt%, Mn 0.5-2.0 wt%, or M
g 0.03-0.5wt%, Cr 0.03-0.3wt%,
Zr 0.03-0.3wt%, Ti 0.03-0.3wt
%, Ni 0.05 to 2.0 wt%, and the above-mentioned aluminum alloy sacrificial anode material is clad on one side of an aluminum alloy core material containing the balance of Al and inevitable impurities. Is what you do.

The significance of the additional elements and the reasons for limiting the composition range of the alloy components of the aluminum alloy composite of the present invention will be described below. In the aluminum alloy composite of the present invention, the most important components for imparting sufficient corrosion resistance under both acidic and alkaline corrosion environments are Zn content, Mn content, In content, and Sn content in the sacrificial anode material. And Zr amount.

[0010] In an alkaline corrosive environment exceeding pH 10, the natural potential of the Al-Mn alloy is largely shifted to the base side as described above. Therefore, in order to prevent the corrosion of Al-Mn alloy core materials in an alkaline corrosive environment exceeding pH 10, the sacrificial anode material Z
It has been found that by increasing the n content to 3.1 wt% or more and further adding In or Sn, it is possible to exert a sufficient sacrificial anticorrosion action on the core material.

Even when the potential difference between the core material and the sacrificial anode material is sufficiently ensured as described above, even in an alkaline environment,
_{^{Al + OH - + H 2 O}} → [Al (OH) 4 · 2H 2 O] - + 3 / for coating of aluminum hydroxide sacrificial anode material surface by reactions such as 2H ₂ generated, the sacrificial anode material by the presence of said coating The anticorrosive effect of the work stops working. However, by adding 0.05 to 0.3 wt% of Zr to the sacrificial anode material, it is possible to suppress the generation of hydrogen in the above reaction formula and to inhibit the formation of an aluminum hydroxide film, thereby effectively exhibiting an anticorrosion effect. it can.

Hereinafter, alloying elements of the sacrificial anode material used in the present invention will be described. Zn has a sacrificial anticorrosive effect in both acidic and alkaline corrosive environments to prevent corrosion of the core material. The reason for limiting the Zn content to 3.1 to 12.0 wt% is that if the content is less than 3.1 wt%, the effect is not sufficient, and 12.0 wt%
%, The rollability of the alloy is reduced and the yield is reduced. The desirable content of Zn is 6.1 to 12.0 wt%. Under an alkaline corrosive environment, the potential of the core material is lower than in a neutral environment. Therefore, by setting Zn to 6.1 wt% or more, corrosion resistance in an alkaline corrosive environment can be improved.

Zr has the function of suppressing the generation of hydrogen under an alkaline environment as in the above reaction formula, inhibiting the formation of an aluminum hydroxide film on the aluminum surface, and increasing the anticorrosion effect. Therefore, the corrosion resistance in an alkaline environment can be improved. Zr content 0.05
The reason for defining the content to be 0.3 wt% is that if the content is less than 0.05 wt%, the effect is not sufficient, and if it exceeds 0.3 wt%, casting cracks may occur. The desirable content of Zr is 0.08 to 0.2 wt%.

Sn and In make the natural potential of the sacrificial anode material extremely low in both acidic and alkaline corrosion environments, and further enhance the sacrificial corrosion protection effect of the sacrificial anode material. The reason why the contents of Sn and In are both defined as 0.002 to 0.3 wt% is as follows.
If the content is less than 0.3% by weight, the rollability of the alloy is reduced and the yield is reduced. The preferred content of Sn and In is 0.005 to 0.1 wt%.

Mn is an element added when it is necessary to improve the strength of the sacrificial anode material. Mn disperses a fine Al-Mn-based compound in the alloy and improves the strength of the sacrificial anode material without lowering the corrosion resistance. The Al-Mn compound has a function of inhibiting the formation of a film in an alkaline corrosive environment, and does not impair the corrosion resistance even in an acidic corrosive environment.
The reason for defining the content of Mn to be 0.5 to 2.0 wt% is 0.5 wt%
If the amount is less than 2.0%, the effect cannot be sufficiently obtained, and if the amount exceeds 2.0% by weight, the moldability deteriorates and the yield decreases. Mn
Is preferably 0.8 to 1.2% by weight.

The above is the alloy element of the sacrificial anode material used in the present invention and the reason for its addition.
Although it can be contained up to 5 wt%, 0.1 wt% or less is desirable.
Elements other than Si may be contained as impurity elements as long as they are each 0.05% by weight or less.

Next, the alloy elements of the core material used in the present invention will be described. Si contributes to the strength improvement by forming a solid solution in the matrix after brazing. The reason for limiting the Si content to 0.005 to 1.2 wt% is that if the content is less than 0.005 wt%, its effect cannot be sufficiently obtained, and if it exceeds 1.2 wt%, elemental Si is precipitated and the self-corrosion resistance of the core material is reduced. This is because Desirable content of Si is 0.005 to 0.8 wt%.

Fe has the effect of distributing coarse intermetallic compounds in the alloy, making the crystal grains of the core material fine, and preventing cracking during forming. The reason for specifying the Fe content to be 0.005 to 0.8 wt% is that if the content is less than 0.005 wt%, the effect cannot be sufficiently obtained, and if the content exceeds 0.8 wt%, the self-corrosion resistance of the core material is reduced. Desirable Fe content is 0.005-0.3wt%
It is.

[0019] Cu contributes to the improvement of strength, but when its content increases, the self-corrosion resistance of the core material decreases. Cu content
The reason for defining the content to be 0.003 to 1.2 wt% is that if the content is less than 0.003 wt%, the effect cannot be sufficiently obtained, and if the content exceeds 1.2 wt%, the melting point of the core material is lowered and the core material is melted at the time of brazing. When the Cu content is 0.003 to 0.01 wt%, the strength decreases, but the self-corrosion resistance of the core material in an alkaline corrosive environment can be improved. Particularly in an alkaline corrosive environment, when Cu is contained in the core material, Cu of the core material is reprecipitated on the surface of the material to form a strong cathode, so that the corrosion resistance is reduced. Therefore, by reducing the Cu content of the core material to less than 0.01 wt%, the self-corrosion resistance of the core material in an alkaline corrosive environment can be improved. When the content of Cu is 0.01 to 1.2 wt%, the self-corrosion resistance of the core material can be improved.

Mn distributes fine intermetallic compounds in the alloy and improves the strength without lowering the corrosion resistance. Mn
The reason for defining the content of 0.5 to 2.0 wt% is that if the content is less than 0.5 wt%, the effect cannot be sufficiently obtained, and if the content exceeds 2.0 wt%, the moldability deteriorates and the yield decreases. The preferred content of Mn is 0.5 to 1.5 wt%.

The selected elements Cr, Zr, and Ti contained in the core material all form fine intermetallic compounds and contribute to the strength and corrosion resistance of the alloy. Cr, Zr, Ti content is 0.03 ~
The reason for specifying 0.3 wt% is that if the content is less than 0.03 wt%, the effect cannot be sufficiently obtained, and if it exceeds 0.3 wt%, casting cracks may occur. The desirable content of each is
0.08 to 0.2 wt%.

Ni, a selective element contained in the core material, has the effect of distributing fine intermetallic compounds in the alloy and improving the strength of the alloy. The reason for defining the Ni content to be 0.05 to 2.0 wt% is that if the content is less than 0.05 wt%, the effect cannot be sufficiently obtained.
If it exceeds 0 wt%, casting cracks may occur. Ni
Is 0.08 to 1.0 wt%.

The selected element Mg contained in the core material is Si as the core material.
At the same time, the Mg ₂ Si compound is age-precipitated to contribute to the improvement of the strength. The reason why the content of Mg is defined as 0.03 to 0.5 wt% is 0.03 w
If it is less than t%, the effect cannot be obtained sufficiently. If it exceeds 0.5 wt%, if brazing material is clad on one side of the core material during brazing, Mg diffuses into the brazing material and reacts with the flux. This is because the brazing property is reduced.

The above is the alloying element of the core material used in the present invention and the reason for its addition. B and other unavoidable impurity elements added for refining the cast structure are contained if each is 0.05 wt% or less. It does not matter.

The aluminum alloy composite material of the present invention comprises an aluminum alloy having the above composition as a core material, and one surface of which is clad with an aluminum alloy sacrificial anode material having the above composition. At this time, an aluminum alloy brazing material may be clad on another side of the core material if necessary. This aluminum alloy brazing material includes Al-Si JIS-4343 alloy (Al-7.5wt% Si), JIS-4045 alloy (Al-10wt% Si), JIS
-4004 alloy (Al-9.7wt% Si-1.5wt% Mg) can be used.
Applications of the aluminum alloy composite material of the present invention are a tube material for a heat exchanger, a header plate material, and the like. When the aluminum alloy composite material of the present invention is used as a tube tube, a method of forming the tube by an electric resistance welding process or a method of forming a tube by brazing after bending is preferably used.

[0026]

The present invention will be further described with reference to the following examples.
A core material having the composition shown in Table 1 and an aluminum alloy of a sacrificial anode material having the composition shown in Table 2 were cast into molds, and the core material was finished to a thickness of 40 mm by facing, and the sacrificial anode material was heated after facing. It was finished to a thickness of 5 mm by cold rolling. As the brazing material, a JIS-4343 alloy was die-cast, and the surface was finished to a thickness of 5 mm by hot rolling after being cut.
The brazing material, the core material, and the sacrificial anode material are laminated in this order, and hot-rolled at 500 ° C. to produce a 3-layer clad material having a thickness of 5 mm, and then cold-rolled to a thickness of 0.29 mm. Rolled, 340
After intermediate annealing at 2 ° C for 2 hours, it was further cold-rolled to a thickness of 0.
A 25 mm H14 brazing sheet was obtained. The cladding ratio of the brazing sheet in the composite material of the sacrificial anode material and the brazing material is 10% for the sacrificial anode material and 10% for the brazing material.

Each of the obtained brazing sheets was subjected to a corrosion resistance test in an acidic environment and a corrosion resistance test in an alkaline environment by the following methods.

[Corrosion resistance test in acidic environment] Each brazing sheet was subjected to electric resistance welding to form a tube tube (length 500 m).
m, the cross-section width was 16 mm, and the cross-section height was 2 mm), and a heat exchanger having the structure shown in FIG. 1 was assembled using this tube tube and the following fins, header plate, and side plate. Thereafter, a corrosive solution under the following conditions was circulated through the tube tubes of the heat exchanger for a predetermined period of time. After the circulation was completed, 10 tube tubes were randomly sampled from the heat exchanger. The pitting depth on the inner surface of these tube tubes was measured by the depth of focus method using an optical microscope, and the largest measured value was rounded off to the maximum pitting depth and indicated in units of 5 μm. For the above fins, a 0.1 mm thick thin plate made of Al-0.5wt% Si-1.0wt% Mn-2.0wt% Zn alloy is corrugated.
Both JIS-3003 for header plate and side plate
A JIS-4343 alloy brazing material is clad on one side of a core material containing 0.15 wt% of Mg added to the alloy, and a sacrificial anode material of Al-0.15 wt% Zn alloy is clad on one side, with a cladding rate of 10%, and the thickness is 1.2. mm
Was used. As the etchant, Cl ^- ion: 195ppm, SO ₄ ^2- ions: 60 ppm, C
u ^{2 +} ions: 1ppm, Fe ^3+: aqueous solution containing 30 ppm (pH
3) was used as a corrosive liquid, which was alternately circulated for 6 months at 88 ° C. for 8 hours and at room temperature for 16 hours.

[0029] the tubes of the heat exchanger of the same configuration as the [alkaline environment corrosion resistance test] The heat exchanger used in the acidic environment corrosion resistance test, Cl ^- ion: 195ppm, SO ₄ ^2- ions: 60 ppm, Cu ²⁺ Ion: 1 ppm, Fe ³⁺ : 30 ppm
A NaCl was added to an aqueous solution (pH 3) containing NaOH to adjust the pH to 11, and the etchant was alternately circulated for 6 months at 88 ° C. for 8 hours and at room temperature for 16 hours. After completion of the circulation, the pit depth on the inner surface of the tube was measured by the same method as in the corrosion resistance test under an acidic environment, and the maximum pit depth was determined.

The results of the corrosion resistance test under acidic and alkaline environments are also shown in Table 2. In any of the corrosion resistance test results, those having a maximum pit depth exceeding 70 μm were indicated by x, and those having a maximum pit depth of 70 μm or less were indicated by ○. Particularly, those having a maximum pit depth of 30 μm or less in the corrosion resistance test under an alkaline environment are indicated by ◎.

[0031]

[Table 1]

[0032]

[Table 2]

As is clear from Table 2, the present invention sample No. 1
In both acidic and alkaline corrosive environments, the pits had a pit depth of 70 μm or less and showed excellent corrosion resistance. Furthermore, the Cu content of the core material of the present invention example is 0.003.
Nos. 5 to 13 having a content of less than 0.01 wt% showed particularly excellent corrosion resistance in a corrosion resistance test under an alkaline environment. In the present invention, the desired Zn content of the sacrificial anode material is 6.1 to 1 as described above.
2% by weight, but less than this range.
Nos. 4 to 4 were slightly inferior in the corrosion resistance test in an alkaline environment as compared with Inventive Examples Nos. 5 to 22 in this range.

On the other hand, in Comparative Examples Nos. 23 to 31 and Conventional Example No. 32 in which the alloy composition of the core material or the sacrificial anode material was not specified in the present invention, the corrosion resistance was reduced under any of acidic or alkaline corrosive environment. , Or as a heat exchanger. That is, in Comparative Example No. 23, since the sacrificial anode material had a low Zr content, an aluminum hydroxide film was firmly formed in an alkaline corrosive environment, resulting in poor corrosion resistance. In Comparative Example No. 24, the In content of the sacrificial anode material was too large, and in Comparative Example No. 25, the Sn content of the sacrificial anode material was too large, so the aluminum alloy composite material could not be manufactured due to cracking during rolling. Was. Further, in Comparative Example No. 26, since the Zn content of the sacrificial anode material was small, the potential difference between the sacrificial anode material and the core material could not be obtained in an alkaline corrosive environment, and the corrosion resistance was poor. In Comparative Example No. 27, the Zn content of the sacrificial anode material was too large, and in Comparative Example No. 28, the Zr content of the sacrificial anode material was too large to break during rolling and aluminum alloy composites could not be manufactured. Was. In Comparative Example No. 29, the Mn content of the core material was too large to form a tube. In Comparative Example No. 30, Si alone as the core material was precipitated, and the self-corrosion resistance of the core material was reduced under both acidic and alkaline corrosion environments. In Comparative Example No. 31, since the Cu content of the core material was too large, the tube was melted at the time of brazing application heat. Also, the conventional example No. 32 is made of Zn as a sacrificial anode material.
Since the content was as low as 1.0 wt%, the potential difference from the sacrificial anode material could not be obtained in an alkaline corrosive environment, and the corrosion resistance was poor.

[0035]

As described above, according to the present invention, it is possible to obtain an aluminum alloy composite material for a heat exchanger having excellent corrosion resistance under both acidic and alkaline corrosion environments, and has a remarkable industrial effect. Things.

[Brief description of the drawings]

FIG. 1 shows a heat exchanger (radiator) for an automobile, in which (A) is a front view and (B) is a cross-sectional view taken along line AA of (A).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tube tube 2 Corrugated fin 3 Header plate 4 Core 5 Packing 6,7 Resin tank

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) B23K 20/00 360 B23K 20/00 360B 35/22 310 35/22 310E 35/28 310 35/28 310B // F28F 19 / 06 F28F 19/06 B B23K 101: 14 (72) Inventor Takenori Tsunobu 2-6-1 Marunouchi, Chiyoda-ku, Tokyo F-term within Furukawa Electric Co., Ltd. 4E067 AA05 BB02 BD02 EB01 EB11

Claims (5)

[Claims] 1. Zn 3.1-12.0 wt%, Zr 0.0
An aluminum alloy sacrificial anode material for a heat exchanger, comprising 5 to 0.3 wt% and the balance being Al and unavoidable impurities. 2. Zn 3.1 to 12.0 wt%, Zr 0.0
An aluminum alloy sacrificial anode material for a heat exchanger, comprising 5 to 0.3 wt% and Mn of 0.5 to 2.0 wt%, the balance being Al and unavoidable impurities. 3. The Al alloy according to claim 1, further comprising 0.002 to 0.3% by weight of In and 0.002 to 0.3% of Sn.
An aluminum alloy sacrificial anode material for a heat exchanger, comprising one or two kinds of 3 wt%. 4. An alloy containing 0.005 to 1.2 wt% of Si, Fe.
005 to 0.8 wt%, Cu 0.003 to 1.2 wt%, M
n on a surface of an aluminum alloy core material containing 0.5 to 2.0 wt% and the balance being Al and unavoidable impurities,
A highly corrosion-resistant aluminum alloy composite for a heat exchanger, wherein the aluminum alloy sacrificial anode material according to 2 or 3 is clad. 5. The aluminum alloy core material according to claim 4, further comprising: Mg 0.03 to 0.5 wt%, Cr 0.03 to 0.5 wt%.
0.3 wt%, Zr 0.03-0.3 wt%, Ti0.03
1 or 2 of Ni-0.3wt%, Ni0.05-2.0wt%
A highly corrosion-resistant aluminum alloy composite for heat exchangers, characterized by containing at least one kind.