JP2001226729A - Aluminum alloy for heat exchanger excellent in corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy free from the need of a sacrificial anode surface material when used as a tube material for a heat exchanger of an automotive radiator, heater core or the like. SOLUTION: This aluminum alloy contains 0.1 to 1.5% Mn, 0.01 to 1.0% Cu, 0.3 to 1.5% Fe, 0.05 to 0.3% Ti and 0.01 to 0.5% Zn, containing one or two of 0.01 to 0.3% Sn and 0.01 to 0.1% In at request, containing 0.01 to 0.3% Zr at request, moreover containing 0.4 to 1.0% Si at request, and the balance Al with inevitable impurities. The alloy exhibits excellent corrosion resistance in a pH region in a wide range from acidity to alkalinity, and the cladding of a sacrificial anode surface material is made unnecessary (the omission of a cladding stage). The material can be made lighter and thinner and the simplification of the process are made possible, and the material cost and the production cost are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy used as a structural member of a heat exchanger which is required to have excellent corrosion resistance in a wide pH range from an alkaline environment to an acidic environment. It is suitably used for radiators for automobiles, heater cores and the like in which an aqueous solution containing tap water (life coolant) or tap water is used as a refrigerant.

[0002]

2. Description of the Related Art Conventionally, as a tube material of a radiator or a heater core for an automobile, an Al-Mn-based core material is clad on one surface with an Al-Si-based or Al-Si-Zn-based brazing material. A welded tube obtained by brazing or high-frequency welding a three-layer brazing sheet clad with an Al—Zn-based alloy as a sacrificial anode skin material is used on the other side. The most commonly used cladding material is JIS3003Al alloy (Mn: 1.0-1.5%, Cu: 0.1-0.2%, S:
i: 0.6% or less, Fe: 0.75% or less, Zn: 0.
10% or less, balance: A consisting of Al and unavoidable impurities
(l-Mn alloy) as a core material, and JIS is provided on one surface of the core material.
It is known that a sacrificial anode skin material made of 7072 is adhered and an Al-Si or Al-Si-Zn brazing material is adhered to the other surface.

[0003] Aluminum and aluminum alloys are covered with a strong natural oxide film and have excellent corrosion resistance and thermal conductivity especially in an environment near neutrality. It is used as a distribution channel material. However, when the oxide film is locally broken for some reason, the other parts are strong, so that corrosion concentrates on the film defect, causing pitting corrosion, and there is a defect that a through-hole is formed early. As a countermeasure, in a heat exchanger for an automobile such as a radiator, as described above, a clad material in which an aluminum alloy which is more electrically less than the core material is adhered to one surface of the core material as a sacrificial anode skin material is used. The tube obtained by brazing or high-frequency welding this clad material exhibits high corrosion resistance to the refrigerant flowing inside because the sacrificial anode skin material is located inside.

[0004]

In recent years, along with the reduction in weight and cost of vehicles, materials for automobile heat exchangers such as tubes have been required to be further reduced in thickness and weight and cost. However, in order to ensure reliable joining by brazing performed in the manufacture of the heat exchanger and sufficient corrosion resistance as a heat exchanger, a certain amount or more of the sacrificial anode skin material and brazing material in the tube material should be used. And there is a limit in reducing the thickness of the material. In addition, the production of clad materials requires extremely expensive rolling equipment and excellent production techniques, and the number of steps up to production is large and the productivity is low, so the cost of materials is high and it is difficult to reduce costs. There are also problems.

Therefore, the present inventors have studied the use of a tube material that does not use a sacrificial anode skin material. However, if the sacrificial anode skin material disappears, corrosion resistance particularly in an acidic environment becomes very problematic as in the past. It is considered to be. In fact, it has been confirmed that when the sacrificial material is not clad with the core material (JIS 3003) of the clad material, a through hole is generated in a very short period in an acidic environment. In recent years,
Cooling water obtained by adding LLC consisting of antifreeze and rust inhibitor to water is used as a refrigerant for an automobile heat exchanger.
It is known that if the LC is inferior, the cooling water becomes alkaline having a pH of about 9 to 11. Even in such an environment, the corrosion resistance of the conventional material is not sufficient, and there is a problem that pitting occurs early.

The present invention has been made in view of the above circumstances, and is an aluminum alloy used for a structural member for a heat exchanger such as a tube material, which includes weakly acidic tap water, rainwater, or poor LLC. Alkaline cooling water, that is, an aluminum alloy that can exhibit excellent corrosion resistance even when using an aqueous solution in a wide pH range from weakly acidic to alkaline as a coolant, even in a single state without cladding the sacrificial anode skin material. It is intended to provide.

[0007]

Means for Solving the Problems The present inventors have studied to obtain an aluminum alloy which is more excellent in corrosion resistance than a conventional material in an aqueous solution in a wide pH range from an acidic solution to an alkaline solution. As a result, (a) Mn: 0.1 to 1.5% in mass%, Cu: 0.0
An Al alloy containing 1 to 1.0% and Fe: 0.3 to 1.5%, with the balance being Al and inevitable impurities,
In an alkaline environment, the corrosion rate is low and the corrosion resistance is excellent, but in an acidic environment, a pit-type corrosion form is generated in a very short period of time, and the corrosion resistance is insufficient. (B) An Al alloy having the composition described in (a) above is added with T
i: 0.05 to 0.3% is added, and Zn: 0.0
The Al alloy containing 1 to 0.5% is excellent in corrosion resistance in an alkaline environment, and also has a layered corrosion form in an acidic environment, thereby suppressing the generation of through-holes. It shows excellent corrosion resistance to aqueous solutions in a wide pH range up to a wide range. (C) Similarly, Al having the composition described in (a) above
Alloy: Ti: 0.05-0.3%, Zn: 0.01-
0.05%, Sn: 0.01-0.3%, I
n: Al added with at least one of 0.01 to 0.1%
The alloy also has a corrosion form similar to that of the alloy (b) and shows very excellent corrosion resistance in both alkaline and acidic environments. Based on the above findings, the present invention has been completed.

That is, the first invention of the aluminum alloy for a heat exchanger having excellent corrosion resistance according to the present invention is,
Mn: 0.1-1.5%, Cu: 0.01-1.0%,
Fe: 0.3 to 1.5%, Ti: 0.05 to 0.3%,
Zn: 0.01 to 0.5%, with the balance being Al and unavoidable impurities.

The aluminum alloy for a heat exchanger according to the second aspect of the present invention, which has excellent corrosion resistance, has a Mn content of 0.1 to 1.5% by mass.
%, Cu: 0.01 to 1.0%, Fe: 0.3 to 1.5
%, Ti: 0.05-0.3%, Zn: 0.01-0.
5%, Sn: 0.01-0.3%, I
n: 0.01 to 0.1% of one or two kinds is contained, and the balance is composed of Al and unavoidable impurities.

The aluminum alloy for a heat exchanger according to the third aspect of the present invention, which has excellent corrosion resistance, has a Mn content of 0.1 to 1.5% by mass.
%, Cu: 0.01 to 1.0%, Fe: 0.3 to 1.5
%, Ti: 0.05-0.3%, Zn: 0.01-0.
5%, Zr: 0.01-0.3%, the balance being Al
And unavoidable impurities.

[0011] The aluminum alloy for a heat exchanger according to the fourth aspect of the present invention, which has excellent corrosion resistance, has a Mn content of 0.1 to 1.5% by mass.
%, Cu: 0.01 to 0.7%, Fe: 0.3 to 1.5
%, Ti: 0.05-0.3%, Zn: 0.01-0.
5%, Zr: 0.01-0.3%.
n: 0.01 to 0.3%, In: 0.01 to 0.1%, at least one of them is contained, and the remainder consists of Al and unavoidable impurities.

According to a fifth aspect of the present invention, there is provided an aluminum alloy for a heat exchanger having excellent corrosion resistance according to the first to fourth aspects, wherein the alloy composition further contains 0.4 to 1.0% of Si and the balance is Al. And unavoidable impurities.

The function of each component in the alloy of the present invention and the reason for limiting the content will be described below. The contents in the following are all expressed in mass%. Mn:
0.1 to 1.5% Mn is crystallized in the material as an intermetallic compound to improve the strength after brazing. Further, since the potential of the tube is made noble, a large potential difference from the fin can be obtained, and the sacrificial anode effect of the fin material is made more effective to improve external corrosion resistance. However, if the content of Mn is less than 0.1%, the above effect cannot be sufficiently obtained, and the strength is particularly insufficient. On the other hand, when the Mn content exceeds 1.5%, coarse A
The generation of the l-Mn intermetallic compound lowers the rollability and further causes peeling of the material surface during rolling. For these reasons, the Mn content is reduced to 0.1 to 1.5%.
Specified within the range. Note that the lower limit is 0.7 for the same reason.
%, And the upper limit is desirably 1.2%.

Cu: 0.01% to 1.0% Cu forms a solid solution in the matrix to improve the strength after brazing, and makes the potential of the tube noble, so that a large potential difference from the fin can be obtained. External corrosion resistance is significantly improved.
Further, the addition of Cu has the effect of improving the strength of the material. However, if the Cu content is less than 0.01%, these effects are not obtained, and the strength is particularly insufficient. On the other hand, Cu
If the content exceeds 1.0%, the corrosion rate is increased, and the growth of pitting is promoted, so that through-holes are easily generated and the corrosion resistance is reduced. Therefore, the Cu content is set to 0.0
It is set to 1 to 1.0%. For the same reason, it is desirable to set the lower limit to 0.3% and the upper limit to 0.7%.

Fe: 0.3 to 1.5% Fe forms an Al-Mn-Fe-based or Al-Fe-based intermetallic compound to improve the strength after brazing. In addition, Fe-based crystallized substances are finely crystallized in the material due to the inclusion of Fe, and they become a source of corrosion to form a corrosive form of surface corrosion, thereby improving corrosion resistance particularly in an alkaline environment. However, if the content is less than 0.3%, these effects cannot be obtained, and a problem particularly occurs in alkali corrosion resistance. on the other hand,
When the content exceeds 1.5%, a giant intermetallic compound of Al-Mn-Fe system is generated, and the castability decreases, and
Peeling occurs in court. Therefore, the Fe content is set to 0.3
に 1.5%. Note that the lower limit is 0.7 for the same reason.
%, And the upper limit is desirably 1.2%.

Ti: 0.05-0.3% Ti improves the corrosion resistance by making the form of corrosion in an acidic environment into a layer. Further, after brazing, it is dispersed in the base material as a fine intermetallic compound to increase the strength. However, if the Ti content is less than 0.05%, these effects cannot be obtained,
Particularly, a problem arises in corrosion resistance in an acidic environment. on the other hand,
Even if the content exceeds 0.3%, further effects cannot be expected, and the formation of a large intermetallic compound is promoted to cause a problem in brittleness. Therefore, the Ti content is set to 0.05 to 0.3%.
Set forth in For the same reason, it is desirable to set the upper limit to 0.3%.

Zn: 0.01-0.5% Zn forms a solid corrosion in the material to form a corroded form.
It has the function of further promoting the effect of layered corrosion due to the addition of i, and significantly improves corrosion resistance in an acidic environment. In order to obtain this effect, Zn content of 0.01% or more is necessary. On the other hand, if the content exceeds 0.5%, the corrosion rate increases and the corrosion resistance decreases rather. 0
It is set to 1 to 0.5%. In addition, the lower limit is set to 0 for the same reason.
It is desirable to set the upper limit to 2% and the upper limit to 0.4%.

Sn: 0.01-0.3% In: 0.01-0.1% Sn, In concentrates on the surface of the material during the heat treatment for brazing and makes the potential base, so that the corrosion is planar corrosion. In addition to the formation, the effect of layered corrosion of Ti is promoted to suppress the progress of corrosion in the depth direction, so that one or two kinds may be contained as desired. In order to obtain the above effect sufficiently,
Each must contain at least 0.01%. On the other hand, S
If the content of n exceeds 0.3% and the content of In exceeds 0.1%, the corrosion rate is increased and the corrosion resistance is rather reduced. In addition, the formation of a low melting point compound in Sn causes cracking of the material during pressing. Therefore, the Sn content is set to 0.01 to 0.3.
% And the In content are set to 0.01 to 0.1%. In addition,
For the same reason as described above, for Sn, the lower limit is desirably 0.05% and the upper limit is desirably 0.15%. For In, the lower limit is desirably 0.03% and the upper limit is desirably 0.07%.

Zr: 0.01-0.3% Zr assists the effect of Ti, which forms a layer of corrosion in an acidic environment, and disperses in the base material as a fine intermetallic compound after brazing to increase the strength. It is included as desired because it increases. However, when the Zr content is less than 0.01%, the above effect cannot be sufficiently obtained. On the other hand, when the Zr content exceeds 0.3%, further improvement of the effect cannot be expected. It is within the range of 0.3%. For the same reason, it is desirable to set the lower limit to 0.05% and the upper limit to 0.1%.

Si: 0.4 to 1.0% Since Si has the effect of improving the strength after brazing, particularly the proof stress, it is positively added if desired. To obtain this effect, a Si content of 0.4% or more is required, while 1.0%
If the content exceeds 0.2%, the melting point of the material is reduced and the corrosion resistance is further deteriorated. Therefore, the Si content is set to 0.4 to 1.0%.

Inevitable impurities In the alloy of the present invention, the balance of the above components consists of Al and inevitable impurities. As an inevitable impurity, in particular, Mg reacts with the flux and impairs brazing properties, so that its content is desirably reduced as much as possible. However, considering the industrial properties, the upper limit is desirably set to 0.1% or less by Mg. Further, even when Si is not positively added, up to an upper limit of 0.2% is present in the material as an unavoidable impurity.

Since the alloy of the present invention has excellent corrosion resistance in an acidic and alkaline environment, it can be used to form a heat exchanger member such as a tube without cladding a sacrificial anode skin material. In addition, there is an advantage that the manufacturing cost and the material cost can be significantly reduced because the weight can be reduced, and the elimination of the cladding step and the elimination of the sacrificial anode skin material. Further, when the alloy of the present invention is used as a core material of a clad material, although the above effects are not obtained, it is possible to provide a clad material having extremely excellent corrosion resistance to acidic and alkaline environments. .

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The aluminum alloy of the present invention can be produced by a conventional method in accordance with the above-mentioned composition setting, and its melting and casting methods are not particularly limited. The obtained ingot is further provided as a material for a heat exchanger through a process such as hot rolling, cold rolling, or extrusion by a conventional method. At this time, a hot-rolled material can be obtained by continuous casting and rolling. Note that an appropriate heat treatment can be performed between the steps or between the steps.

Although the alloy of the present invention is originally intended to be used as a single material, it does not exclude the use as a core material of a clad material. When manufacturing a clad material, a brazing material or a sacrificial anode skin material is bonded to the alloy material of the present invention. The method of manufacturing the cladding is not particularly limited, and the cladding can be performed by a conventional method.

The aluminum alloy of the present invention is processed into a tube for a heat exchanger or the like by the above-described extruded tube or plate-forming tube, and is assembled to other members (headers, fins, etc.) for the heat exchanger. The alloy of the present invention can also be applied as a structural member such as a header plate material and a tank material which conventionally used a three-layer clad material. After the assembling, brazing is performed to manufacture a heat exchanger by fixing each of them. The components of the aluminum alloy of the present invention do not affect the brazing conditions, and the brazing operation can be performed by a conventional method. The brazing material can be provided by being clad on the above aluminum alloy, or can be supplied in the form of powder applied to the brazing portion. As the brazing material, generally used brazing materials such as Al-Si and Al-Si-Zn can be used, and types of usable brazing materials are not particularly limited. The aluminum alloy material after brazing exhibits excellent corrosion resistance in a wide range of pH from acidic to alkaline environment by appropriate component adjustment, and also enables thinner and lighter tube materials and lighter heat exchangers. Therefore, the obtained heat exchanger is suitable for an automobile. However, the use of the heat exchanger is not limited to a specific use in the present invention, and the heat exchanger can be used as a heat exchanger for other uses.

[0026]

Embodiments of the present invention will be described below.
An aluminum alloy having the composition shown in Table 1 was melt-cast to produce a rolled ingot, and the ingot was homogenized under ordinary conditions, and then subjected to hot rolling, cold rolling, intermediate annealing, and tempering. According to H14, a tube material of the present invention having a plate thickness of 0.25 mm (250 μm) and a comparative tube material having a composition outside the range of the present invention were produced. These tubes are placed in a nitrogen gas atmosphere at 600 ° C.
At a cooling rate of 100 ° C./min. , A brazing equivalent heat treatment was performed to cool to room temperature, and then a tensile test was performed at room temperature to measure the tensile strength, and a corrosion test was further performed under the following conditions.

(Corrosion test 1) One side of each material was masked, and the other side was Cl ⁻ : 170 ppm, SO
_{^{4 2-: 50ppm, Fe 3+:}} 20ppm, C
u ²⁺ : Contact an aqueous solution of pH 3.0 containing 1 ppm, circulate the aqueous solution at 80 ° C. for 8 hours at a flow rate of 4 m / s, assuming that the aqueous solution is cooling water for an automotive heat exchanger, The corrosion test was performed in a temperature cycle of holding for a time. After performing this test for 28 days, the maximum pitting depth inside the tube was measured. (Corrosion test 2) One side of each material was masked, and the other side was Cl ⁻ : 170 ppm, SO ₄ ²⁻ : 50
ppm, Fe ³⁺ : 20 ppm, Cu ²⁺ : 1 ppm, and contacted with an aqueous solution adjusted to pH 11 with NaOH,
Assuming that this aqueous solution is cooling water for an automobile heat exchanger,
After circulating at a flow rate of 4 m / s for 8 hours at
The corrosion test was performed in a temperature cycle of holding for a time.
After performing this test for 60 days, the maximum pit depth in the tube was measured.

Table 2 shows the results of the tensile test and the corrosion test.
It was shown to. As is clear from the table, the test material using the aluminum alloy of the present invention has extremely excellent corrosion resistance in both acidic and alkaline environments and has a high tensile strength even in a single material. On the other hand, the test material using an alloy whose component is out of the range of the material of the present invention is inferior in corrosion resistance in either acidic or alkaline environment.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

As described above, according to the aluminum alloy for a heat exchanger of the present invention, Mn: 0.
1-1.5%, Cu: 0.01-1.0%, Fe: 0.
3 to 1.5%, Ti: 0.05 to 0.3%, Zn: 0.
0.1 to 0.5%, and if desired, Sn: 0.01 to
0.3%, In: one or more of 0.01 to 0.1%
Seed, Zr: 0.01-0.3%, Si: 0.4-1.0
%, And the balance consists of Al and unavoidable impurities, so that even in a single material, it exhibits excellent corrosion resistance in a wide pH range from acidic to alkaline, thus enabling the material to be lightweight and thin. Material costs can be significantly reduced, resulting in radiators, heater cores,
This can greatly contribute to cost reduction and improvement of the life of a heat exchanger such as an oil cooler. When used as the core material of the clad material, it contributes to the improvement of the life of the heat exchanger as a material having extremely excellent corrosion resistance.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Junichiro Hirohashi 5-24-15 Minamidai, Nakano-ku, Tokyo Calsonic Co., Ltd. (72) Inventor Masakazu Edo 85-85 Hiramatsu, Susono-shi, Shizuoka Prefecture Technology of Mitsubishi Aluminum Corporation Inside the Development Center (72) Inventor: Shu Kuroda 85, Hiramatsu, Susono-shi, Shizuoka Pref.In the Technology Development Center, Mitsubishi Aluminum Co., Ltd. (72) Inventor Tian Tate 85, Hiramatsu, Susono-shi, Shizuoka Pref.

Claims (5)

[Claims] 1. Mn: 0.1-1.5% by mass, C
u: 0.01 to 1.0%, Fe: 0.3 to 1.5%, T
An aluminum alloy for a heat exchanger having excellent corrosion resistance, characterized by containing i: 0.05 to 0.3% and Zn: 0.01 to 0.5%, with the balance being Al and unavoidable impurities. 2. Mn: 0.1 to 1.5% by mass, C
u: 0.01 to 1.0%, Fe: 0.3 to 1.5%, T
i: 0.05 to 0.3%, Zn: 0.01 to 0.5%, Sn: 0.01 to 0.3%, In: 0.
Containing 0.1 to 0.1% of one or two kinds, the balance being Al
Aluminum alloy for heat exchangers with excellent corrosion resistance, characterized by comprising aluminum and unavoidable impurities 3. Mn: 0.1 to 1.5% by mass, C
u: 0.01 to 1.0%, Fe: 0.3 to 1.5%, T
i: 0.05 to 0.3%, Zn: 0.01 to 0.5%,
Zr: an aluminum alloy for heat exchangers having excellent corrosion resistance, characterized by containing 0.01 to 0.3% and the balance consisting of Al and inevitable impurities. 4. Mn: 0.1 to 1.5% by mass, C
u: 0.01 to 1.0%, Fe: 0.3 to 1.5%, T
i: 0.05 to 0.3%, Zn: 0.01 to 0.5%,
Zr: 0.01-0.3%, and Sn:
Aluminum for heat exchangers excellent in corrosion resistance, characterized in that it contains at least one of 0.01 to 0.3% and In: 0.01 to 0.1%, and the balance consists of Al and unavoidable impurities. alloy 5. The corrosion resistance of the alloy composition according to claim 1, further comprising 0.4 to 1.0% of Si, with the balance being Al and unavoidable impurities. Excellent aluminum alloy for heat exchanger