JP3529074B2 - Aluminum alloy clad material for heat exchanger with excellent alkali corrosion resistance - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy clad material for a heat exchanger, which is excellent in alkali corrosion resistance, and more specifically, it is used for automobiles by brazing in an inert gas atmosphere or vacuum brazing using a fluoride-based flux. When manufacturing aluminum heat exchangers such as radiators and heater cores, it can be applied as the tube material, header material, etc., which are the constituent members, especially against alkaline corrosive environment due to the coolant normally used in the heat exchanger. The present invention relates to an aluminum alloy clad material for a heat exchanger, which has excellent corrosion resistance.

[0002]

2. Description of the Related Art As a radiator tube for automobiles, a tube material for a heater core, and a header plate material, an Al-Si brazing material is clad on one side of a core material made of an Al-Mn type alloy such as 3003 alloy and the other surface is used. As a sacrificial anode material,
A three-layer aluminum alloy clad material clad with an 1-Zn alloy is used.

In the aluminum alloy clad material, the Al-Si brazing material is a tube material and a fin material joined by brazing in an inert gas atmosphere using a fluoride flux or vacuum brazing, a tube material and a header. The sacrificial anode material is provided for joining with the plate material.When the sacrificial anode material is assembled in an aluminum heat exchanger such as a radiator or a heater core, the sacrificial anode material exerts a sacrificial anode effect on the working fluid to produce the core material. It is provided to prevent pitting corrosion and crevice corrosion.

In these heat exchangers, an antifreeze solution containing ethylene glycol as a main component, which is commercially available as a coolant, is used as a working fluid in an amount of 0 to 50 vol% with water.
A neutral to weakly alkaline solution diluted to a concentration is used, but a working fluid may cause pitting corrosion through the core material in the aluminum alloy clad material forming a tube or the like, impairing the heat exchange function. Often experienced.

By examining the combination of the component composition of the core material and the component composition of the sacrificial anode material, a corrosion resistant aluminum alloy clad material having an improved sacrificial anode effect by enhancing the pitting corrosion resistance, for example, a core material is used. , Mn: 0.3 to 2.0%, M
g: 0.10 to 0.80%, Cu: 0.05 to 0.50%, aluminum alloy composed of balance Al and unavoidable impurities, and a skin material clad on one side of the core material with Zn:
An aluminum alloy containing 0.3 to 2.0% and Mg: 0.1 to 2.5%, the balance being Al and unavoidable impurities, and the skin material clad to the other side of the core material is S.
i: 7.0 to 15.0%, Mg: 0.3 to 2.5%, balance Al
Also, a clad material composed of an aluminum alloy containing unavoidable impurities has been proposed. (Japanese Patent Publication No. 62-45301)

Further, as a sacrificial anode material on at least one surface of the aluminum alloy core material, Zn: 0.1 to 2.0%, Ti: 0.0
01-0.05%, B: 0.0001-0.01%, and Fe:
0.01-1.0%, Si: 0.01-1.0% within the range of S
An aluminum alloy composite material (Japanese Patent Laid-Open No. 63-114948) formed by using an aluminum alloy containing i and Fe in a total amount of 0.02 to 1.5% and the balance Al and unavoidable impurities as a skin material, on one or both sides of a core material, Fe: 0.20 to 1.5%, Zn: 0.2 to 2.0%, Mg: 0.1 to 1.5%, M
There has been proposed an aluminum alloy composite material (Japanese Patent Laid-Open No. 1-195257) in which an aluminum alloy containing one or more of n: 0.3 to 1.5% is coated as a sacrificial anode material.

These aluminum alloy clad materials are
When used as a tube material for aluminum heat exchangers such as radiators and heater cores, the working fluid
Excellent sacrificial anode effect is exhibited in the case of a solution containing Cl ions at a relatively low temperature and neutral to weakly acidic, but pitting corrosion is still likely to occur when the working fluid is an alkaline solution having a pH of 9 or more. In many cases, the corrosion resistance is not sufficient and the anticorrosion effect cannot be exhibited.

In the process of investigating the cause of pitting corrosion that occurs in an aluminum alloy clad material clad with a sacrificial anode material in an alkaline solution having a pH of 9 or more and its countermeasure, the sacrificial anode is It has been found that a porous thick film having a brown to black color is formed on the surface of the layer, and corrosion concentrates on the defective portion of the film and preferentially corrodes, thereby forming a through hole.

[0009]

Based on the above findings, the present invention preferentially corrodes the sacrificial anode material by utilizing the potential difference between the core material and the sacrificial anode material. It was made as a result of various experiments and studies on the combination of such a core material and a sacrificial anode material, the purpose of which is to use a working fluid having excellent alkali corrosion resistance and alkalinity. Another object of the present invention is to provide an aluminum alloy clad material for a heat exchanger that can prevent the formation of through holes due to pitting corrosion.

[0010]

The aluminum alloy clad material for a heat exchanger excellent in alkali resistance according to the present invention for achieving the above object is an Al-Si type brazing material on one surface of a core material made of an aluminum alloy. In an aluminum alloy clad material for a heat exchanger in which the sacrificial anode material is in contact with the working fluid, the core material is Mn: 0.3 to 2.0%, Cu : 0.
10% to 0.8% of 1 type or 2 types, the balance of Al and aluminum alloy composed of unavoidable impurities, and the sacrificial anode material is Fe: more than 0.5% and 3.0% or less, In : 0.01 to 0.2%, the balance consisting of aluminum and unavoidable impurities, composed of an aluminum alloy , chlorine ion (Cl ⁻ ) 195 ppm, sulfate ion
(SO ₄ ²⁻ ) 60ppm , copper ion (Cu ²⁺ ) 1pp
m, corrodes an aqueous solution containing 30 ppm of iron ion (Fe ³⁺ )
As a liquid, soak in the corrosive liquid heated to a temperature of 88 ° C for 8 hours
After soaking, cool and keep at 25 ℃ for 16 hours
Sacrificial anode even if corrosion test is repeated for 3 months
First , the maximum corrosion depth of the material is 0.10 mm or less
It is a feature of.

Excellent alkali corrosion resistance according to claim 2
The aluminum alloy clad material according to claim 1, wherein the sacrificial anode material is Fe: more than 0.5% and 3.0% or less, In: 0.01%.
~ 0.2%, Mg: 0.1-2.5%, Zn: 0.5
~4.0%, Sn: 0.01 ~0.2% , Ga: includes 0.01 to 0.2% one or more of, and characterized in that it is made of aluminum alloy and the balance Al and inevitable impurities, claim Aluminum alloy clad by 3
The material according to claim 1 or 2, wherein the sacrificial anode material further comprises C
r: 0.05-0.3%, Zr: 0.05-0.3%, Ti: 0.05-
0.3%, B: 0.01-0.1%, Mn: 0.1-2.0%, Si:
It is characterized by containing one or more of 0.1 to 1.0%.

Excellent alkali corrosion resistance according to claim 4
The aluminum alloy clad material is the same as in claims 1 to 3.
The core material contains one or two of Mn: 0.3 to 2.0% and Cu: 0.10 to 0.8%, and Mg: 0.1 to 0.5%, S.
The aluminum alloy clad material according to claim 5 is characterized in that it is composed of an aluminum alloy containing i: 0.1 to 1% and the balance is Al and inevitable impurities.
In the requirements 1 to 4, the core material further contains Cr: 0.05 to 0.3.
%, Zr: 0.05-0.3%, Ti: 0.05-0.3%, B: 0.0
It is characterized by containing one or more of 1 to 0.1%.

Explaining the significance of the alloying components in the present invention and the reasons for limiting them, Fe in the sacrificial anode material is
The Al-Fe compound is finely dispersed in the matrix, and at the position of the compound existing on the surface of the material, the deposition of aluminum hydroxide, which is a coating component, is prevented and the formation of the coating is suppressed. As a result, that portion becomes a coating defect. Although pitting corrosion occurs, the film defects are present around the finely dispersed Al-Fe compound, and therefore the number of them is large and evenly distributed. It becomes shallow and no through hole is formed. The preferable Fe content range is over 0.5%.
3.0% or less, less than 0.5%, the effect is small,
If the content exceeds 3.0%, the self-corrosion property of the sacrificial anode material increases and the rolling workability deteriorates. The more preferable content range of Fe is more than 0.7% and 1.2% or less.

By adding a trace amount of In to the alloy, In functions to make the potential of the sacrificial anode material base and maintain the sacrificial anode effect on the core material, and as a result, the occurrence of pitting and crevice corrosion in the core material. To prevent. The preferable content range of In is 0.01 to 0.2%, and if it is less than 0.01%, its effect is small, and if it exceeds 0.2%, self-corrosion resistance and rolling workability are deteriorated. A more preferable content of In is 0.
It is in the range of 01 to 0.05%.

Mg diffuses into the core material during brazing, and improves the strength of the core material together with Si and Cu in the core material. A preferred content range is 0.1 to 2.5%, and if it is less than 0.1%, its effect is small, and if it exceeds 2.5%, local melting occurs during brazing. Zn makes the potential of the sacrificial anode material base and maintains the sacrificial anode effect on the core material, and as a result, prevents pitting and crevice corrosion of the core material. The preferred content is 0.5-
It is 4.0%, and if it is less than 0.5%, its effect is not sufficient,
If it exceeds 4.0%, the self-corrosion property decreases. The more preferable content range of Zn is 1.0 to 2.0%.

Sn and Ga function to make the potential of the sacrificial anode material base, reliably exert the sacrificial anode effect on the core material, and prevent pitting corrosion and crevice corrosion in the core material. The preferred content is Sn: 0.01-0.2%, G
a: 0.01 to 0.2%. If the amount is less than the lower limit, the effect is small, and if the amount exceeds the upper limit, the self-corrosion property decreases and the rolling processability is impaired. S
More preferable contents of n and Ga are 0.01 to 0.
It is in the range of 05%. In the sacrificial anode material, 0.05 to 0.3
% Cr, 0.05-0.3% Zr, 0.05-0.3% Ti,
0.01 to 0.1% B, Mn: 0.1 to 2.0%, Si: 0.1 to 1.0
%, It does not affect the characteristics, and the characteristics can be improved.

In the present invention, by using the aluminum alloy sacrificial anode material having the above composition, alkali corrosion resistance can be obtained regardless of the composition of the aluminum alloy constituting the core material. Amount of Mn, Cu
Alternatively, when an aluminum alloy containing a specific amount of Mn, Cu, Mg, Si is used, a more excellent effect can be obtained.

Mn in the core material functions not only to improve the strength of the core material, but also to make the potential of the core material noble and increase the potential difference from the sacrificial anode material to enhance the corrosion resistance. The preferred content range is 0.3 to 2.0%, and if it is less than 0.3%, its effect is small, and if it exceeds 2.0%, a coarse compound is generated during casting and the rolling processability is impaired, and it is difficult to obtain a sound plate material. . The more preferable content of Mn is 0.5 to 1.5
% Range.

Cu functions to improve the strength of the core material, make the potential of the core material noble, increase the potential difference between the sacrificial anode material and the brazing material, and improve the anticorrosion effect. Further, Cu in the core material diffuses into the sacrificial anode material and the brazing material during heating brazing to form a gentle concentration gradient, so that the potential on the core material side becomes noble and the surface of the sacrificial anode material is Side and the surface side of the brazing material become base, a gentle potential distribution is formed in the sacrificial anode material and in the brazing material, and the corrosion form becomes a general corrosion type. C
The preferred content of u is 0.10-0.8%,
If it is less than 0.8%, the effect is small, and if it exceeds 0.8%, the corrosion resistance of the core material is lowered, and the melting point is lowered, so that local melting easily occurs during brazing. The more preferable content range of Cu is 0.3 to 0.6%.

Although Mg has the effect of improving the strength of the core material, it is feared that the brazing property will deteriorate, so the content is set to 0.1 to 0.5%. When brazing in an inert gas atmosphere using a fluoride-based flux, the Mg content is 0.5%
When it exceeds, the Mg reacts with the fluoride-based flux to hinder the brazing property, and a fluoride of Mg is generated to make the appearance of the brazed portion poor. In the case of vacuum brazing, if the Mg content in the core material exceeds 0.5%, the molten solder will easily erode the core material.

Si has the function of improving the strength of the core material. In particular, by coexisting with Mg that diffuses from the sacrificial anode material during brazing, age hardening occurs after brazing and the strength is further increased. The preferred content range is 0.
1 to 1%, and if less than 0.1%, its effect is small.
If it is contained in excess of%, the corrosion resistance decreases and
The melting point of the core material is lowered, and local melting is likely to occur during brazing. More preferable contents of Mg and Si are in the ranges of 0.2 to 0.5% and 0.2 to 0.5%, respectively.

Cr, Zr, and B function to suppress the penetration of the brazing material into the core material during brazing heating. The preferred content range is Cr: 0.05-0.3%, Zr: 0.05-0.
3%, B: 0.01 to 0.1%. If the amount is less than the lower limit, the effects are small, and if the amount exceeds the upper limit, huge crystallized substances are generated during casting, which makes it difficult to produce a sound material. Ti is divided into a high-concentration region and a low-concentration region in the thickness direction of the material to form a layered structure in which these are alternately distributed,
The region having a low i concentration has an effect of layering the corrosion form by preferentially corroding the region having a high i concentration, thereby preventing the progress of the corrosion in the thickness direction and improving the pitting corrosion resistance of the material. . The preferable content of Ti is in the range of 0.05 to 0.3%, and if it is less than the lower limit, the effect is not sufficient, and if it exceeds 0.3%, huge crystallized substances tend to be generated during casting, making it difficult to manufacture sound materials. .

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum alloy clad material for a heat exchanger of the present invention is obtained by semi-continuously casting an aluminum alloy constituting a core material, a sacrificial anode material and a brazing material,
After homogenizing the core material and sacrificial anode material,
Each is hot rolled to a predetermined thickness. Then, the respective materials are combined, and a clad material is formed by hot rolling according to a conventional method, and finally, cold rolling is performed to a predetermined thickness to manufacture the clad material.

When a welded pipe is manufactured from the aluminum alloy clad material of the present invention to be used as a tube material for a heat exchanger, and also as a header plate material when used for assembling an aluminum heat exchanger such as a radiator or a heater core for an automobile. Is a combination of aluminum alloy fin materials and brazing in an inert gas atmosphere using a fluoride-based flux or vacuum brazing in a brazing furnace.

Therefore, in the aluminum alloy clad material of the present invention, an Al—Si type brazing material is clad on one surface of the core material. In this case, for brazing in an inert gas atmosphere, basically, Al-containing Si: 6 to 13%
A Si alloy is applied, and for vacuum brazing, an Al-Si-Mg alloy containing, for example, Mg: 0.5 to 3.0% is further applied. These Al-Si type brazing materials include B
i: 0.1% or less, Be: 0.1% or less, Ca: 1.0% or less, L
It is also possible to contain one or more of i: 1.0% or less.

[0026]

【Example】

Example 1 By continuous casting, an aluminum alloy for a core material having a composition shown in Table 1, an aluminum alloy for a sacrificial anode material having a composition shown in Table 2, and an alloy for a brazing material (JIS BA4343, S
i: 7.5%, balance Al and inevitable impurities) were cast. Homogenization treatment is applied to the ingots of the aluminum alloy for the core material and the aluminum alloy for the sacrificial anode material, and the ingots of the aluminum alloy for the sacrificial anode material and the alloy for the brazing material are hot-rolled to a predetermined thickness, and these rolled Material and ingot of core alloy were combined and hot rolled to obtain a clad material. Further, cold rolling and intermediate annealing were performed, and final cold rolling was performed to produce a clad plate material (H14) having a thickness of 0.25 mm. The brazing material clad ratio of the clad plate material was 10%, and the clad thickness of the sacrificial anode material was 0.025 to 0.075 mm (cladding ratio 10 to 30%).

[0027]

[Table 1] << Table Note >> Fe is an unavoidable impurity Si of test material E is an unavoidable impurity

[0028]

[Table 2] <Table Note> Si is an unavoidable impurity

On the brazing material side of the obtained clad plate material, M
A fin material made by corrugating an aluminum alloy plate (thickness 0.10 mm) containing n: 1.2%, Zn: 1.5% and the balance Al and unavoidable impurities is arranged, and a fluoride-based flux is used. After heating to a temperature of 600 ° C (material temperature) in a nitrogen gas atmosphere and brazing, visually observing the joining state of the plate and fin after brazing,
The molten state of the core material and the sacrificial anode material was examined by observing the cross-sectional structure.

Next, without disposing the fin material on the clad plate material, the clad plate material was heated as it was under the same conditions as brazing using the above-mentioned fluoride-based flux to prepare a test material, which is shown below. Such a corrosion test was performed. Corrosion test 1: A CASS test (test period 30 days) was performed on the brazing material side (outer surface side).

Corrosion test 2: For the sacrificial anode material side (inner surface side), a commercially available antifreeze solution was diluted with distilled water to a concentration of 30 vol%, and caustic soda was added to adjust the pH to 10 to prepare a test material. 8h in corrosive liquid heated to a temperature of 88 ℃
After soaking, the cycle of cooling and holding at a temperature of 25 ° C for 16 hours was repeated for 3 months.

[0032] Corrosion Test 3: the sacrificial anode material side (inner surface ^{side), Cl -: 195ppm, SO} 4 2 -: 60ppm, Cu 2+: 1ppm
, Fe ³⁺ : An aqueous solution containing 30 ppm was used as a corrosive liquid, and the test material was immersed in the corrosive liquid heated to a temperature of 88 ° C. for 8 hours,
3 cycles of cooling and holding at a temperature of 25 ° C for 16 h
Repeated for a month.

Table 3 shows the combination of the core material and the sacrificial anode material, and the brazability and corrosion test results in that case. As can be seen from Table 3, the test materials according to the present invention all have good rolling workability and do not cause defects such as cracks.
In addition, the brazing condition was good, no local melting was observed in the core material and sacrificial anode material, and the maximum corrosion depth in Corrosion Test 1 was 0.11 mm or less, which is half the plate thickness of the clad plate material. The maximum corrosion depth in the corrosion tests 2 and 3 was 0.10 mm or less, which showed excellent corrosion resistance that did not reach 1/2 of the plate thickness. The effects of the present invention were sufficiently exhibited in the range of the clad ratio of the sacrificial anode material of 10 to 30%.

[0034]

[Table 3] <Table Note> Rolling workability ○: Good brazing property ○: Good

Comparative Example 1 By continuous casting, an aluminum alloy for a core material having a composition shown in Table 4, an aluminum alloy for a sacrificial anode material having a composition shown in Table 5, and an alloy for a brazing material (JIS BA4343, Si: 7.5).
%, The balance Al and unavoidable impurities) were cast into a clad plate material having a thickness of 0.25 mm (wax material clad rate: 10%, sacrificial anode material clad rate: 20%) under the same conditions as in Example 1. . The obtained clad plate material was brazed in the same manner as in Example 1, and a test material for a corrosion test was prepared under the same conditions as in Example 1 to visually observe the brazed joint state, observe the cross-sectional structure, and corrode. The test was conducted. The results are shown in Table 6. In Tables 4, 5, and 6, those that do not satisfy the conditions of the present invention are underlined.

[0036]

[Table 4] <Table Note> Fe is an unavoidable impurity

[0037]

[Table 5] <Table Note> Si is an unavoidable impurity

[0038]

[Table 6] << Table Note >> Rolling workability ○: Good ×: Cracking and brazing property ○: Good △: Local dissolution ×: Local melting is severe

As shown in Table 6, the test material No. 16 is
Since the amount of Fe in the sacrificial anode material was small, in the corrosion test 2, through holes were formed due to pitting corrosion. Test material No. 17 had too much Fe in the sacrificial anode material, Test material No. 18 did not contain In in the sacrificial anode material, and Test material No. 21 had a large amount of Zn in the sacrificial anode material. The corrosion depth in the corrosion test 3 is large. Test material No.19, test material No.22, and test material No.23 each contained too much In, Sn, and Ga in the sacrificial anode material, and test material No.26 contained Mn in the core material. Since the amount was too large and a coarse compound was generated during casting, cracks occurred in the rolling process, and it was not possible to manufacture a clad plate material. Test material No. 20 had too much Mg in the sacrificial anode material, so that local melting occurred during brazing.

In the test material No. 24, the amount of Si in the core material was too large, the melting point of the core material was lowered, and local melting occurred during brazing. Therefore, in the test material No. 28, the Cu content in the core material was Since the amount of Mg in the core material was too high for both test materials No. 29 and local melting occurred during brazing, no corrosion test material could be produced. Test material No.25, Test material No.27
The content of Mn and Cu in the core material is too low, so that the potential difference between the core material and the sacrificial anode material is small, and a sufficient corrosion resistance effect is not provided. Particularly, in the corrosion test 1 and the corrosion test 3, The depth is increasing.

[0041]

According to the present invention, there is provided an aluminum alloy clad material for a heat exchanger, which is excellent in corrosion resistance, particularly alkali corrosion resistance. This aluminum alloy clad material can be suitably used particularly as a radiator for automobiles, a tube material such as a heater core, and a header plate material.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F28F 19/06 F28F 19/06 A (56) Reference JP-A-5-69184 (JP, A) JP-A-1-195257 ( JP, A) JP 4-193927 (JP, A) JP 5-43971 (JP, A) JP 4-198447 (JP, A)

Claims (5)

(57) [Claims] 1. An aluminum for a heat exchanger in which an Al—Si brazing material is clad on one surface of a core material made of an aluminum alloy and a sacrificial anode material is clad on the other surface, and the sacrificial anode material is in contact with a working fluid. In the alloy clad material, the core material is Mn: 0.3 to 2.0% (weight%, the same applies hereinafter), C
2. u: 0.10 to 0.8% of one or two, and the balance is made of an aluminum alloy consisting of Al and unavoidable impurities, and the sacrificial anode material exceeds Fe: 0.5%.
0% or less, In: 0.01 to 0.2% contained, balance A
1 and unavoidable impurities, it is composed of an aluminum alloy , chloride ion (Cl ⁻ ) 195 ppm, sulfur sulfate ion
(SO ₄ ^2- ) 60ppm , Copper ion (Cu ²⁺ ) 1pp
m, corrodes an aqueous solution containing 30 ppm of iron ion (Fe ³⁺ )
As a liquid, soak in the corrosive liquid heated to a temperature of 88 ° C for 8 hours
After soaking, cool and keep at 25 ℃ for 16 hours
Sacrificial anode even if corrosion test is repeated for 3 months
An aluminum alloy clad material for a heat exchanger having excellent alkali corrosion resistance , wherein the maximum corrosion depth of the material is 0.10 mm or less . 2. The sacrificial anode material contains Fe: more than 0.5% and 3.0% or less, In: 0.01 to 0.2%, and Mg: 0.1 to 2.5%, Zn: 0.5-4.0
%, Sn: 0.01 to 0.2%, Ga: 0.01 to 0.
The aluminum alloy for a heat exchanger having excellent alkali corrosion resistance according to claim 1, wherein the aluminum alloy contains one or more of 2% and the balance is Al and unavoidable impurities. Clad material. 3. The sacrificial anode material further comprises Cr: 0.05-.
0.3%, Zr: 0.05 to 0.3%, Ti: 0.05
~ 0.3%, B: 0.01-0.1%, Mn: 0.1
2.0%, Si: 0.1-1.0% of 1 type (s) or 2 or more types of containing, It is characterized by the above-mentioned.
An aluminum alloy clad material for heat exchangers having excellent alkali corrosion resistance as described. 4. The core material is Mn: 0.3 to 2.0%, C
u: 0.10 to 0.8% of one or two, Mg: 0.1 to 0.5%, Si: 0.1 to 1%, balance Al and unavoidable impurities. The aluminum alloy clad material for a heat exchanger according to any one of claims 1 to 3, which is excellent in alkali corrosion resistance. 5. The core material further comprises Cr: 0.05 to 0.3.
%, Zr: 0.05-0.3%, Ti: 0.05-0.
3%, B: 0.01-0.1% of 1 type or 2 types or more of 0.1% are contained, The heat exchange excellent in alkali corrosion resistance in any one of Claims 1-4 characterized by the above-mentioned. Aluminum alloy clad material for ware.