JPH11209837A - Sacrificial anti-corrosion aluminum alloy for heat exchanger and aluminum alloy composite material using it for heat exchanger - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the corrosion resistance on the inner surface side of a tube of a heat exchanger for an automobile. SOLUTION: An Al alloy containing more than 6.0% by weight of Zn and not more than 15.0% by weight, containing Cu: not more than 0.05% by weight, the balance being Al and unavoidable impurities, and having an average crystal grain size on the surface. A sacrificial corrosion-resistant aluminum alloy for a heat exchanger, wherein

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin aluminum alloy composite used for a heat exchanger for automobiles and the like, and more particularly to a tube forming a refrigerant passage of a heat exchanger formed by a brazing method. The present invention relates to a three-layered Al alloy composite material used as a tube material.

[0002]

2. Description of the Related Art As shown in FIGS. 1 (a) and 1 (b), a conventional aluminum heat exchanger, for example, a radiator has a fin (2) disposed between tube tubes (1) through which a refrigerant passes, and a tube tube (1). Attach header plate (3) to both ends of 1),
After assembling the core (4), after brazing, the resin plate (5) is inserted into the header plate (3) via the packing (6),
(5 ') is attached. And fins (2)
JIS3003 alloy (Al-0.15wt% Cu-
1.1 wt% Mn) and a plate with a thickness of about 0.1 mm in which Zn is added in an amount of about 1.5 wt%.
JIS 70 on the inside (refrigerant side) of the alloy core material to which
72 (Al-1 wt% Zn) or an alloy obtained by adding Mg or the like thereto and clad as a sacrificial anode material.
A tube tube (1) with a thickness of 1.0 to 1.3 mm is used for the header plate (3) using a brazing sheet of 0.3 mm.
A brazing sheet made of the same material as that described above is used.

[0003] These brazing sheets are exposed to an atmosphere of about 580 to 610 ° C at the time of brazing application heat, whereby Zn in the sacrificial anode material diffuses into the core material as shown in FIGS. 2 and 3. Due to the preferential corrosion of the Zn diffusion layer,
The pits generated from the refrigerant side do not grow deeply, take a shallow and wide pitting form, and exhibit long-term pitting resistance. Al-
Zn-based (No more than 4 wt% Zn), Al-Zn-Mg
The Al-Mg-In-based sacrificial anode alloy itself has a feature of taking a shallow and wide pitting corrosion form (face corrosion), and furthermore, the sacrificial material is exposed even after the core material is exposed due to a potential difference between the core material and these sacrificial materials. It is said to be preferentially corroded and prevent corrosion of the core material.

[0004]

Recently, with the reduction in the thickness of the plate due to the weight reduction and the sophistication of the heat exchanger, the environment in which the liquid flow rate inside the tube tube is much faster than in the past, and the cooling used Depending on the water (coolant), a high alkali liquid specification may be used. Also, depending on the environment in which the car is running, if the coolant deteriorates for some reason, the sacrificial material of the conventional technology will not only provide a sufficient anticorrosion effect, but also will cause a serious problem of increased tube corrosion accompanying so-called erosion. is there.

[0005]

Means for Solving the Problems As a result of diligent studies to solve the above problems, we have found the present invention. That is, even when the refrigerant side of the inner surface of the tube is particularly in an alkaline liquid environment, the coolant liquid function is deteriorated, and even when the liquid flow rate is large, the epoch-making aluminum alloy composite material for the heat exchanger is hardly caused. They invented a sacrificial corrosion-resistant aluminum alloy used as a sacrificial material.

That is, the sacrificial corrosion-resistant aluminum alloy for a heat exchanger of the present invention contains Zn in an amount of more than 6.0 wt% (hereinafter, wt% is simply referred to as%) and not more than 15.0%, and Cu: 0.05%.
It contains the following or further contains Mn: 0.05 to 2.0%, and is characterized by being composed of the balance of Al and inevitable impurities.

Further, the aluminum alloy composite of the present invention
The sacrificial anti-corrosion Al alloy is clad on one surface of an Al alloy core material as a sacrificial material, and the other surface is clad with an Al-Si alloy brazing material containing a predetermined amount of Si. The core material is Si: 0.05-1.
2%, Cu: 0.003 to 1.2%, Mn: 0.05 to
2.0%, the balance consisting of Al and inevitable impurities, or Si: 0.05 to 1.2%, Cu: 0.00
3 to 1.2%, Mn: 0.05 to 2.0%, Mg: 0.03 to 0.5%, Cr: 0.03 to 0.
3%, Zr: 0.03 to 0.3%, Ti: 0.03 to
0.3%, Ni: one or two of 0.05 to 2.0%
Those containing more than one species are good. Further, the sacrifice material has a surface average crystal grain size of 100 to 700 μm.

In the present invention, it has been confirmed that, compared to the usual amount of Zn which has been conventionally known as an anticorrosion effect element in a sacrificial material, the amount of Zn to be added is so large that it is difficult to predict with the conventional idea. In addition, the present inventors have found an effect that the corrosion dissolution of the sacrificial material is not increased more than necessary by including Cu in a predetermined range and defining (controlling) the average crystal grain size on the surface of the sacrificial material. In this way, even if the coolant retains high alkali and the liquid function deteriorates depending on the use environment, and even in an environment with a high liquid flow rate, erosion and corrosion hardly occur, and the function of the sacrificial material for a long time , And the corrosion resistance can be greatly improved.

Further, in the present invention, the composition of the core material is also specified at the same time assuming any use environment. That is, within the alloy composition range of the present invention, the balance between strength and self-corrosion resistance can be improved as compared with conventional alloys, and erosion and corrosion can be further suppressed.

Next, the difference between the prior art and the present invention will be described. Japanese Patent Application Laid-Open No. 9-87 relates to a brazing sheet for a heat exchanger having excellent strength and high-temperature corrosion resistance as one of the prior arts.
No. 788 discloses a sacrificial material of the Al alloy disclosed therein, in which the Zn content is the same as that of the anticorrosion aluminum alloy of the present invention, but other essential elements are completely different. JP-A-3-124392 and JP-A-3-124392 concerning a brazing sheet for a refrigerant passage of a heat exchanger having excellent corrosion resistance.
Japanese Patent No. 124393 discloses a crystal grain size of a sacrificial material similar to that of the present invention, but the composition is completely different from that of the Al alloy of the present invention.

In the above-mentioned prior art, there is no description about a method for improving corrosion resistance in a high alkali solution and a high flow rate environment. That is, in the prior art, the present invention defines the amount of Zn in a sacrificial material defined in order to solve the problems of erosion and corrosion,
It is not the content that the Cu amount and the average crystal grain size are all controlled simultaneously.

The reason why the additive element and the crystal grain size of the Al alloy used as the sacrificial material in the present invention are specified will be described below.
The major features are the following.

[0013] Zn content: more than 6%, not more than 15%
When the coolant (coolant) is in a highly alkaline (pH 8 to 11) environment, the natural potential of the sacrificial material tends to be higher than that of the core material due to the electrochemical reaction. In the direction in which the potential difference between the two decreases. Therefore, the amount of Zn is 6
% Or less, the potential of the sacrificial material becomes more noble than the core material in combination with the core material alloy used industrially or the core material alloy of the present invention, and the corrosion resistance is rapidly deteriorated. On the other hand, if the Zn content exceeds 15%, the melting point of the sacrificial material itself starts to decrease, and there is a possibility that the sacrificial material will be melted at a normal brazing heat temperature. In order to minimize the sacrificial corrosion protection effect in the above corrosive environment, it is necessary that the amount of Zn be included within the scope of the present invention. Desirably, the Zn content is 7 to 12%.

Average crystal grain size on the surface of the sacrificial material: 100 to 7
The reason why the thickness is set to 00 μm is that the self-potential of the sacrificial material rises in an environment where the coolant (coolant) is highly alkaline (pH 8 to 11) and the liquid flow rate is further high, so that the corrosion (grain) near the crystal grain boundary (grain) occurs. The frequency of occurrence of interfacial corrosion) increases rapidly. Even when the core material is exposed by corrosion dissolution, the intergranular corrosion of the sacrificial material itself becomes more active, and the anticorrosion ability is reduced at a stretch. Therefore, if the crystal grain size is less than 100 μm, intergranular corrosion becomes significant. 7
When the thickness exceeds 00 μm, the deformability of the material is reduced when the Al alloy composite material is subjected to the electric sewing process or the bending process in the final step, and in some cases, there is a risk of crack fracture.
Therefore, in order to have the sacrificial anticorrosion effect at least in the above corrosive environment, it is necessary to define the average crystal grain size on the surface of the sacrificial material in the present invention. Desirably, 120 to 500 μm
Is good. Further, the thickness is preferably 150 to 370 μm. In addition, as a method of controlling the crystal grain size, it can be controlled by the hot rolling start temperature of the sacrificial material alone, which is the pre-clad rolling step, or the amount of Mn added in the sacrificial material. Incidentally, if the crystal grain size of the sacrificial material in the state of the composite plate having the final thickness is within the range of the present invention, even in a practical environment as an actual heat exchanger, and even under a corrosive environment, the crystal grain size is The present invention is satisfied.

Reason for restricting Cu content to 0.05% or less In order to maintain the sacrificial material's anticorrosive ability for a long time under the above corrosive environment, the Zn content and the crystal grain size of the sacrificial material are defined in the present invention. Is not enough. Cu content of sacrificial material is 0.05
%, Cu segregated at the crystal grain boundaries promotes intergranular corrosion. Starting from the intergranular corrosion of the sacrificial material, the dissolution speed of the core material may increase when corrosion is exposed. Desirably, the Cu content is 0.0
It is good to regulate to 0.05 to 0.028%.

Therefore, it is possible to use the sacrificial material under the above-mentioned corrosive environment without any problem if the Zn content and the Cu content of the sacrificial material are all within the specified ranges and the surface crystal grain size is all specified in the present invention.

If the Mn content of the sacrificial material is specified in the present invention, the erosion resistance is further improved. M
The reason why n is limited to 0.05 to 2.0% is that when the content is less than 0.05%, the above effect is not sufficiently exhibited, and when the content exceeds 2.0%, the tube tube is subjected to an electric sewing process or a brazing process. This is because, at the time of manufacture, there is a possibility that a problem of a weld defect (micro crack) or a defective bending process may be caused.

Other elements (Ti ≦ 0.2%, Mg ≦ 0.
03%, Ge or Ga ≦ 0.2%, Zr ≦ 0.2%
) May be added as long as the various properties are not reduced as long as the amount is small.

Next, the reasons for defining each element of the core material of the composite material of the present invention and the reasons for limiting the range of addition will be described. Si, C
u and Mn form a solid solution in the matrix after brazing, and are effective in improving the strength. Further, when used in combination with the sacrificial material of the present invention, defining the amount of Cu in the present invention is very effective in preventing the corrosion.

If the amount of Si added is less than 0.05%, there is no effect of improving the strength, and if it exceeds 1.2%, there is a possibility that deep pitting corrosion may be caused by Si alone. Preferably, 0.3
It is better to be 0.9%.

The reason why the addition amount of Cu is set to 0.003 to 1.2% is that if the amount is less than 0.003%, the above effect is not obtained.
If the ratio exceeds the limit, the self-corrosion resistance of the core material is reduced, and a problem occurs that intergranular corrosion is promoted. Further, there is a possibility that welding cracks may be caused during the electric resistance welding. In addition, desirably, 0.005 to 0.05% or 0.4 to 0.8% according to the use environment.
%.

The reason that the amount of Mn added is 0.05 to 2.0% is that if less than 0.05%, there is no strength improvement effect,
If the ratio exceeds the above range, a problem that workability is deteriorated occurs. Desirably, it is set to 0.3 to 1.5%. More preferably, the content is set to 0.7 to 1.2%.

Mg has an effect of improving strength by precipitating the compound of Mg ₂ Si together with Si as the core material. 0.0
If it is less than 3%, there is no effect of improving the strength, and if it exceeds 0.5%, Mg diffuses into the brazing material side surface clad on one side of the core material when the brazing heat is applied, and reacts with the flux when flux is used. This may cause brazing failure.
Desirably, it is set to 0.08 to 0.25%.

Cr, Zr and Ti are each in the range of 0.03-0.3.
%, The self-corrosion resistance of the core material can be further improved. If it is less than 0.03%, the effect is not obtained, and if it exceeds 0.3%, solidification cracking during casting may be induced. Desirably, each is 0.08 to 0.2%.

The strength can be improved by adding 0.05 to 2.0% of Ni. If it is less than 0.05%, the effect is small, and if it exceeds 2%, the rollability deteriorates, which is not good. Desirably, the content is 0.2 to 1.0%. Other elements may be added as long as various properties are not deteriorated.

The method for producing the core material and the sacrificial material is not limited to a DC method, such as a DC method and continuous casting (caster). Homogenization processing conditions, hot rolling, cold rolling, intermediate annealing conditions, and the like are not particularly limited.

Next, as a brazing material in the present invention, for example, an Al-Si based JIS 4343 alloy (Al-7.5%
Si), JIS 4045 alloy (Al-10% Si) and JIS 4004 alloy (Al-9.7% Si-1.5% M
g) can be used. Further, Cu, Zn and other elements may be added to the Al-Si alloy brazing material as long as the brazing property is not reduced. Further, the same effect can be sufficiently exerted by the method of joining the brazing material by the powder + binder coating method in addition to the clad rolling method specified in the present invention.

The Al alloy composite material of the present invention can be used not only for radiators and heater tube pipes but also for radiators and heater header plates, and can be used satisfactorily as any other member as long as the object of the present invention is the same. .

[0029]

Next, an embodiment of the present invention will be described. Table 1
No. 1 to No. 28 of the core material alloy having the composition shown in Table 2 and the sacrificial material alloy having the composition shown in Table 2 were cast by die casting. , 12,16,
Hot rolling starts at 450 ° C for the sacrificial alloys 18 and 26, hot rolling starts at 560 ° C for the No. 21 sacrificial alloy, and hot rolling starts at 500 ° C for the other sacrificial alloys. Then, each was rolled to a plate thickness of 5 mm. Each of the core alloys was homogenized at 560 ° C. for 3 hours, and finished to a thickness of 40 mm by facing. The brazing material was JIS4343 alloy, and was subjected to die casting in the same manner as the sacrificial material. That is, the cladding ratio of the sacrificial material and the brazing material to the entire composite material was set to 10%.

The brazing material, the core material, and the sacrificial material were stacked in this order, and hot rolling was started at 490 ° C. to obtain a three-layer clad material having a thickness of 3.5 mm. Thereafter, the sheet thickness was reduced to 0.
It was set to 357 mm, subjected to intermediate annealing at 340 ° C. for 2 hours, and finally cold-rolled to a sheet thickness of 0.25 mm to obtain an H14 composite sample.

The measurement of the average crystal grain size on the surface of the sacrificial material and the corrosion resistance of the material were evaluated by the following methods. First, each composite material sample was turned into a tube tube by an electric resistance welding process with the sacrificial material side inside, and the tube tube was formed into a 0.07 mm-thick Al-tube.
0.5% Si-0.2% Cu-1.0% Mn-2.0%
Corrugated fins made of Zn alloy and plate thickness
2mm header plate and side plate (JIS
As shown in FIG. 1, using a 4343 alloy brazing material and an Al-1.5% Zn sacrificial material, each of which is clad by 10% of the total thickness and a core material (an JIS 3003 alloy + 0.15% Mg Al alloy composite material). After that, brazing was performed to produce a heat exchanger core. And the following measurement was implemented about these heat exchanger cores.

<Measurement of Grain Size of Sacrificial Material> A sample of the composite material of H14 was cut out, the grain structure on the sacrificial material side surface was observed by electrolytic polishing (Barker method), and the average crystal grain size was measured based on the ASTM method. Table 3 shows the average grain size of the surface of the sacrificial material.

<Corrosion Test> A corrosion test was performed under the following two types of liquid conditions, and the maximum pit depth generated from the sacrificial material side was measured. Table 3 shows the results.

Acidic Circulation Test The following liquid was circulated in the tube using the above heat exchanger core. (Flow rate 2 m / sec) Liquid type: tap water +10 ppm Cu ion +150 ppm Cl
Ion test conditions: A cycle test of 85 ° C. × 10 hours and room temperature × 14 hours is performed for 5 months.

Alkaline erosion test Liquid type: 1 ppm Cu ion, 30 ppm Fe ion, 40 ppm
ppm sulfate and 150ppm Cl
A corrosion liquid adjusted to pH 11 by adding aOH is used. Test conditions: Nozzle diameter from which test liquid is discharged; 2 mmφ, vertical distance from nozzle to sample; 10 mm, flow rate 8 m / sec, 40 ° C.
A continuous test of × 1 month was performed.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

As is clear from Table 3, the present invention No. 1
No. 20 has a pit depth of 60μ in the acidic environment corrosion test.
m or less, ensuring excellent corrosion resistance. Furthermore, even in an erosion test in which the liquid flow rate is large under a high alkali, the maximum pitting depth is 80 μm or less, and the corrosion resistance is good. On the other hand, Comparative Example alloys No. 21 to No. 2 having alloy compositions outside the scope of the present invention
In No. 7, alkali side corrosion remarkably progresses, and a through hole is generated. Comparative Examples No. 21, 23, 24, 2
In Comparative Example No. 7, the amount of the sacrificial material Zn was out of the range of the present invention, and Comparative Example No.
22, 25 and 26, the Zn content of the sacrificial material is within the range of the present invention, but the Cu content or the crystal grain size of the sacrificial material is outside the range of the present invention.

[0040]

As is apparent from the above description, the Al alloy composite of the present invention using the sacrificial corrosion-resistant aluminum alloy of the present invention ensures excellent sacrificial corrosion protection not only in acidic but also alkaline corrosion environments. Has excellent corrosion resistance in which corrosion pitting does not progress for a long time. Further, according to the present invention, the conventional problem can be solved, such as the erosion resistance of the sacrificial material is greatly improved, even in an environment where erosion easily progresses, and the industrially remarkable effect is achieved.

[Brief description of the drawings]

FIGS. 1A and 1B show an example of a radiator, wherein FIG. 1A is a front view, and FIG. 1B is an enlarged sectional view taken along line AA of FIG.

FIG. 2 is an explanatory diagram showing an example of a Zn diffusion state before heat of brazing of a tube material.

FIG. 3 is an explanatory diagram showing an example of a Zn diffusion state after heat of brazing of a tube material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tube tube 2 Fin 3 Header plate 4 Core 5, 5 'Resin tank

Claims (6)

[Claims] 1. A composition containing Zn: more than 6.0 wt% and not more than 15.0 wt%, Cu: not more than 0.05 wt%, the balance being Al
Sacrificial anti-corrosion aluminum alloy for heat exchangers, consisting of aluminum and unavoidable impurities. 2. The composition contains Zn: more than 6.0% by weight and 15.0% by weight or less, Mn: 0.05 to 2.0% by weight, and Cu: 0.1% by weight.
A sacrificial anti-corrosion aluminum alloy for heat exchangers containing up to 05 wt%, with the balance being Al and unavoidable impurities. 3. An Al-Si alloy brazing material containing a predetermined amount of Si on one surface of an Al alloy core material, wherein the Al alloy according to claim 1 or 2 is clad as a sacrificial material. Aluminum alloy composites for heat exchangers that are clad. 4. The Al alloy core material is Si: 0.05 to 1.2.
wt%, Cu: 0.003 to 1.2 wt%, Mn: 0.05
The aluminum alloy composite material for a heat exchanger according to claim 3, wherein the aluminum alloy composite material contains about 2.0 wt% and the balance consists of Al and inevitable impurities. 5. The Al alloy core material is Si: 0.05 to 1.2.
wt%, Cu: 0.003 to 1.2 wt%, Mn: 0.05
-2.0 wt%, and further Mg: 0.03-0.5.
wt%, Cr: 0.03-0.3 wt%, Zr: 0.03-
0.3 wt%, Ti: 0.03 to 0.3 wt%, Ni: 0.
The aluminum alloy composite material for a heat exchanger according to claim 3, wherein the aluminum alloy composite material contains one or more of 0.05 to 2.0 wt%. 6. An aluminum alloy composite for a heat exchanger, wherein the sacrificial material according to claim 3, 4 or 5 has a surface average crystal grain size of 100 to 700 μm.