JPH1161305A - Aluminum alloy clad material for heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy clad material for heat exchanger, improved in corrosion resistance to a greater extent. SOLUTION: This aluminum alloy clad material for heat exchanger has a core material having a composition consisting of, by weight, 0.3-1.2% Si, 0.3-1.0%, Cu, 0.5-2.0% Mn, 0.05-0.5% Mg, and the balance Al with inevitable impurities. Further, one side of this core material is clad with a sacrificial anode material composed of an Al alloy which has a composition consisting of, by weight, >2.0-6.0% Zn, 0.2-2.0% Mn, and the balance Al with inevitable impurities and in which corrosion current value is regulated to <=40 μA/cm<2> by incorporating an Al-Mn intermetallic compound of 0.1-0.8 μm average grain size at >=2.0×10<9> pieces/mm<3> number density, and the other side is clad with a brazing filler metal of an Al-Si alloy containing prescribed amounts of Si.

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 material 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. 3 suitable as tube material
The present invention relates to a layered aluminum alloy composite material.

[0002]

2. Description of the Related Art One example of a conventional aluminum heat exchanger, for example, a radiator, is shown in FIGS. 1A is a front view, and FIG. 1B is a cross-sectional view taken along line AA of FIG. 1A. As shown in FIG. 1, the radiator has fins 2 arranged between tube tubes 1 through which a refrigerant passes. Then, the header plate 3 is attached to both ends of the tube tube 1 to assemble the core 4, and after the brazing, the packing 6 is attached to the header plate 3.
And the resin tanks 5 and 5 'are attached thereto. For the fin 2, a plate having a thickness of about 0.1 mm obtained by adding about 1.5% of Zn to the JIS3003 alloy composition (hereinafter, unless otherwise specified,% indicating the composition refers to% by weight) is used. In order to prevent pitting corrosion on the refrigerant side, JI
A brazing sheet having a thickness of 0.3 to 0.2 mm in which a JIS7072 alloy or an alloy obtained by adding Mg or the like is clad as a sacrificial anode material on the inner side (coolant side) of an alloy core material obtained by adding Si, Cu, etc. to the S3003 alloy composition. Using
A brazing sheet of the same material as that of the tube tube 1 having a thickness of 1.0 to 1.3 mm is used for the header plate 3.

[0003] These brazing sheets are exposed to an atmosphere of about 580 to 610 ° C during brazing, whereby Zn in the sacrificial anode material diffuses into the core material. FIG.
2 shows this state. FIG. 2A shows the state before brazing and FIG. 2B shows the state after brazing. Since the Zn diffusion layer is preferentially corroded, 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 system, Al-Zn-Mg system or Al-M
The g-In-based sacrificial anode alloy itself has a feature that it takes a shallow and wide pitting form (surface corrosion), and furthermore, the sacrificial anode material is preferentially exposed even after the core material is exposed due to the potential difference between the core material and these sacrificial anode materials. Corroded, prevents corrosion of core material.

As such a conventional aluminum alloy composite material, there has been proposed a technique of using a sacrificial anode material of an aluminum alloy containing a predetermined amount of Zn and Mn and having improved strength (Japanese Patent Application Laid-Open No. 56-1981). 127194, 58
-113367). However, Mn in the sacrificial anode material
Is to improve the strength or to make the potential noble,
It is not intended to improve corrosion resistance. However, while the thickness has been reduced due to recent weight reduction, the liquid flow velocity inside the tube tube has become much faster than before due to the sophistication of heat exchangers. The anode material is no longer able to provide a sufficient anticorrosion effect. In other words, the higher the liquid flow rate inside the tube tube, the higher the corrosion rate. Therefore, the development of an aluminum alloy composite material exhibiting higher corrosion resistance (self-corrosion resistance or sacrificial corrosion resistance) is required. ing.

[0005]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an aluminum alloy composite for a heat exchanger having further improved corrosion resistance. More specifically, an object of the present invention is to provide an aluminum alloy composite material for a heat exchanger, in which the erosion-corrosion phenomenon is less likely to occur in a tube of a heat exchanger in which the liquid flow rate is higher than in the past, in a refrigerant side environment of the inner surface of the tube. Aim.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, have found that the sacrificial anode material Z
After defining the n and Mn amounts, Al-Mn in the sacrificial anode material
By controlling the particle size and distribution of the systemic compound, the corrosion current value associated with the anticorrosion action of the sacrificial anode material can be reduced, thereby enabling erosion and
It has been found that corrosion is unlikely to occur, the function of the sacrificial anode material can be maintained for a long time, and the corrosion resistance can be greatly improved, and further research has been carried out on this finding, leading to the present invention. That is, the present invention relates to (1) Si 0.3 to 1.2
%, Cu 0.3-1.0%, Mn 0.5-2.0
%, Mg 0.05 to 0.5%, and a core material composed of the balance of Al and inevitable impurities, and one surface of each of the core materials having a Zn content of more than 2.0% and 6.0% or less, Mn 0.2
Al-Mn having an average particle diameter of 0.1 to 0.8 μm, the Al alloy containing 0.1% to 0.8% (the above percentages indicate weight%), the balance being Al and other unavoidable impurities.
A sacrificial anode material composed of an Al alloy containing a number density of 2.0 × 10 ⁹ / mm ³ or more and a predetermined amount of S
an aluminum alloy composite material for a heat exchanger, which is formed by cladding a brazing material of an Al-Si alloy containing i, and (2) a corrosion current value of the sacrificial anode material of 40 μm.
A / cm ² or less is provided, wherein the aluminum alloy composite material for a heat exchanger according to the above (1) is provided. According to the present invention, corrosion dissolution of sacrificial anode material (corrosion current)
While keeping the core low, the core material can be efficiently corroded and erosion can be suppressed. In the present invention, A in the sacrificial anode material
By defining the size and distribution of the l-Mn-based compound, there is an effect of significantly reducing the corrosion current value of the sacrificial anode material,
This makes it difficult for erosion and corrosion to occur even in a use environment in which the flow velocity of the fluid flowing in the tube is high, so that the function of the sacrificial anode material can be maintained for a long time, and the corrosion resistance can be greatly improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The sacrificial anode material used in the present invention has excellent corrosion resistance (self-corrosion resistance and sacrificial corrosion resistance). Zn in the sacrificial anode material should be more than 2.0% and not more than 6.0%. Zn makes the sacrificial anticorrosion effect sufficiently large regardless of whether the corrosive environment is acidic or alkaline. If the amount of Zn added is 2.0% or less, sacrificial corrosion protection in an acidic environment cannot be maintained. If it exceeds 6.0%, the effect of suppressing the oxide film and the effect of maintaining the sacrificial corrosion protection ability in an alkaline environment may be significantly reduced, and the sacrificial anode material and the core material may be reduced depending on the temperature during brazing heating. Material melting may occur in the vicinity of the interface.
Preferably, the amount of Zn added is 2.5% to 4.5%.

[0008] Mn is 0.2 to 2.0%. Mn is A
It regulates the distribution of l-Mn compounds and acts to solve the problem of erosion and corrosion. If Mn is less than 0.2%, the above effect is not sufficiently exerted. If it exceeds 2.0%, welding defects (microcracks) may occur when a tube tube is manufactured by electric resistance welding or bending brazing. Otherwise, there is a fear that a problem of defective bending dimension may be caused. In the present invention, Al-Mn in the sacrificial material
The average particle size of the intermetallic compound is 0.1 to 0.8 μm,
The reason why the number density is set to 2.0 × 10 ⁹ / mm ³ or more is that if the compound distribution is out of this range, the effect of reducing the corrosion current due to the corrosion prevention of the sacrificial anode material and suppressing the erosion and corrosion is insufficient. That's why. In the present invention, as described above, the sacrificial material corrosion current value can be significantly suppressed and reduced as compared with the value of the conventional sacrificial anode material. FIG.
FIG. 3 shows a schematic diagram of the results of electrochemical measurement of the sacrificial anode material of the present invention. FIG. 3 shows that controlling the distribution of the Al—Mn compound within the range of the present invention significantly reduces the so-called corrosion current corresponding to the intersection of the anode curve and the cathode curve. Corrosion current value of sacrificial material is 40μ
If the A / cm ² or less, the above effect is exhibited. FIG.
In the above, A and B indicate the intersections of the anode and cathode polarization curves of the present invention example and the conventional example, respectively. In the present invention, this intersection point is on the left side from the dotted line C (corresponding to a current of 40 μA / cm ² ).

Next, the reasons for defining each element of the core material and the reasons for limiting the range of addition will be described. Si, Cu and Mn form a solid solution in the matrix after brazing and exhibit a strength improving action. Si is 0.3 to 1.2%. If the amount of Si added is less than 0.3%, there is no strength improvement effect, and if it exceeds 1.2%, deep pitting corrosion is caused by Si alone. The addition amount of Si is preferably 0.7 to 1.0%.

[0010] The added amount of Cu is 0.3 to 1.0%.
If it is less than 0.3%, there is no strength improvement effect, and if it exceeds 1.0%, a large amount of Cu diffuses to the sacrificial anode material side, so that the function of the sacrificial anode material is impaired. Further, there is a possibility that welding cracks may be caused during the electric resistance welding. Preferably, the added amount of Cu is 0.4 to 0.8%. Mn addition amount of 0.5 to
The reason for setting the content to 2.0% is that if the content is less than 0.5%, there is no effect of improving the strength, and if the content exceeds 2.0%, a problem that the workability is reduced occurs. %.

Mg contributes to the improvement of strength by precipitating the Mg ₂ Si compound together with the core material Si. 0.05
If it is less than 0.5%, 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 at the time of brazing and reacts with the flux when flux is used. There is a danger that brazing failure will occur.
Preferably, it is 0.1 to 0.3%. The brazing material in the present invention is not particularly limited. For example, Al-Si JIS 4343, JIS 4045 alloy and JIS 40
04 alloy or the like can be used.

Such a heat exchanger aluminum alloy composite can be prepared as follows. Al- in sacrificial anode material
Control of the distribution of the Mn-based intermetallic compound can be realized by performing the homogenization treatment temperature before the sacrificial anode material rolling at 420 to 520 ° C. If it is lower than 420 ° C., it is difficult to make the ingot structure uniform. When the temperature exceeds 520 ° C., coarsening of the compound becomes active, and it becomes difficult to make the distribution as defined above in the present invention. The holding time at the above temperature is preferably 3 to 9 hours. Not only the homogenization temperature of the sacrificial anode material but also the definition of the clad rolling start temperature, which is the subsequent step, is important, and the clad temperature is preferably 420 to 520 ° C. If the temperature is lower than 420 ° C., there is a possibility that the sacrificial anode material may peel off from the core material during the clad rolling. 52
When the temperature is higher than 0 ° C., there is no problem of poor clad pressure bonding, but it is difficult to satisfy the compound distribution of the sacrificial anode material specified in the present invention. In addition, the conditions for cold rolling and intermediate annealing are not particularly limited.

The Al alloy composite material of the present invention can be used for a radiator header plate in addition to a radiator tube tube, and any other member similar to the object of the present invention, for example, a heater core or a tube of a drone cup evaporator. It can be used as a sheet or header tube. In the aluminum alloy composite material of the present invention, the cladding ratio of the sacrificial anode material is not particularly limited, but is preferably 8 to 20% (by thickness) with respect to the total thickness of the composite material.
2-17% is more preferable. The cladding ratio of the brazing material is not particularly different from that of the conventional brazing material.
-15%, preferably 8-12%. The thickness of the heat exchanger aluminum alloy composite of the present invention varies depending on the application, the type of the heat exchanger, and the like, but is usually 0.2 to 0.4 mm.

[0014]

Next, the present invention will be described in more detail with reference to examples. Example 1 Combination alloy 1 of sacrificial anode material and core material having the composition shown in Table 1
0 types were cast by die casting, and after both surfaces were ground, the sacrificial anode material was homogenized under the conditions shown in Table 2. The thickness was 5 mm by hot rolling, and the core material was 40 mm only by facing. Finished. That is, the cladding ratio of the sacrificial anode material to the entire composite material (including the brazing material) was set to 10%. In addition, the comparative sample No. in Table 2 No. 11 is alloy No. 11 of the present invention. 2
In the sample No. of the present invention, except that the homogenization treatment of the sacrificial anode material was changed as shown in FIG. Exactly the same as 2. As the brazing material, a JIS4343 alloy was used, and the mold was cast as in the case of the sacrificial anode material, and the surface was cut and hot-rolled to a thickness of 5 mm. That is, the clad ratio for the entire composite material was set to 10%. Three sheets of a brazing material, a core material, and a sacrificial anode material were stacked in this order, and hot rolling was started under the conditions shown in Table 2 to obtain a three-layer clad material having a thickness of 3.5 mm. After that, 0.29mm by cold rolling
It was subjected to intermediate annealing at 340 ° C. × 2 hours and finally cold-rolled to a thickness of 0.25 mm to obtain a sample of H14 material. For these samples, the number density of Al-Mn-based intermetallic compounds having an average particle size of 0.1 to 0.8 µm in the sacrificial anode material was cut out in a direction perpendicular to the rolling direction with a precision cutter (microtome device), and transmitted. It was measured with an electron microscope. After that, determine the sample thickness with the equal thickness interference fringes,
Among the intermetallic compounds in the visual field range, the average particle size is 0.1.
The number density of the Al-Mn compound of 1 to 0.8 µm was calculated by the following equation.

[0015]

(Equation 1)

The conditions for measuring the corrosion current value of the sacrificial anode material are as follows. A standard calomel electrode was used as a reference electrode, 3.5% saline was used as an electrolyte, and the temperature was 40 ° C.
, A sample having an area of 1 cm ² was measured at a sweep rate of 20 mV / min and a natural potential measurement time of 5 minutes. The corrosion current value is a current value corresponding to the intersection (A or B in FIG. 3) of the anode and cathode polarization curves obtained in this manner. The corrosion resistance of the sample was evaluated by the following method. Each of the composite material sample of the present invention and the comparative alloy composite material sample was formed into a tube tube by an electric resistance welding process, and the tube tube was formed of an Al—
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 (4
343 brazing filler metal and Al-1.5% Zn sacrificial anode material
A heat exchanger was manufactured using a core material (3003 + 0.15% Mg, an Al alloy composite material) clad by 0%.
A circulating corrosion test using the following two types of corrosive liquids and an erosion test in which a high-velocity liquid flow collides against the sacrificial anode material side of the tube plate were performed, and the maximum pitting depth generated from the sacrificial anode material side was measured. Table 2 shows the results.

<Liquid conditions for corrosion test> Severe acid side test Liquid type: tap water +10 ppm Cu ion +150 ppmC
1 ion; pH 3 Test conditions: A cycle test of 85 ° C. × 10 hours and room temperature × 14 hours is performed for 5 months. Severity test on alkaline side Liquid type: tap water + 200ppm CO ₃ ^2- ion + 50pp
mCl ion; pH 9 Test conditions: A cycle test of 85 ° C. × 10 hours and room temperature × 14 hours is performed for 5 months. Erosion / corrosion test Liquid type: tap water +200 ppm CO ₃ ^2- ion +50 pp
mCl ion; pH10 Conditions: Nozzle diameter from which the tester liquid comes out: 2 mmφ, vertical distance from the nozzle to the sample: 5 mm, flow rate 8 m / sec. At 40 ° C. × 1 week.

[0018]

[Table 1]

[0019]

[Table 2]

As is apparent from Table 2, the sample No. of the composite material of the present invention. 1 to 8 have a pit depth of 80 μm or less in any of the corrosion tests in an acidic environment and an alkaline environment,
Ensure excellent corrosion resistance. Furthermore, even when the liquid flow rate in the tube is high, chemical dissolution of the surface, which is a starting point of the erosion phenomenon, is suppressed, and as a result, the maximum pitting depth is 70 μm or less. On the other hand, Comparative Sample No. having an alloy composition outside the range of the present invention. Samples Nos. 9 and 10 have inferior corrosion resistance in the acidic and alkaline test environments. Further, even in the erosion test, the corrosion progresses remarkably, leading to the generation of through holes. As is clear from the above, A according to the present invention
The 1-alloy composite sample ensures excellent sacrificial corrosion protection not only in the corrosive environment on the alkaline side but also on the acidic side, and obtains excellent corrosion resistance in which corrosion pitting does not progress for a long period of time. Further, even in an environment where erosion is likely to proceed, the conventional problems such as the surface of the sacrificial anode material being hardly chemically dissolved and the erosion resistance being greatly improved can be solved, and an industrially remarkable effect can be achieved.

[0021]

As described above, the aluminum alloy composite material for a heat exchanger of the present invention has an excellent anti-corrosion effect due to the sacrificial anode material, and the pits from the refrigerant side of the heat exchanger do not grow deeply and exhibit long-term pitting resistance and corrosion resistance. Significantly higher heat exchangers can be produced.

[Brief description of the drawings]

FIG. 1A is a front view showing an example of a conventional radiator, and FIG. 1B is a sectional view taken along line AA of FIG.

FIGS. 2A and 2B are explanatory diagrams of a diffusion state of Zn in a sacrificial anode material into a core material, wherein FIG. 2A shows a state before brazing and FIG. 2B shows a state after brazing.

FIG. 3 is a graph showing a result of electrochemical measurement of a sacrificial anode material of the present invention in comparison with a conventional one.

Claims (2)

[Claims] 1. 0.3% to 1.2% of Si, 0.3% of Cu
~ 1.0%, Mn0.5 ~ 2.0%, Mg 0.05 ~
A core material containing 0.5%, the balance being Al and unavoidable impurities, and one surface of each of the core materials having Zn in excess of 2.0% and 6.0% or less, Mn 0.2-2.0% (more % Represents% by weight), an Al alloy comprising the balance of Al and other unavoidable impurities, and having an average particle diameter of 0.1 to 0.8 μm. A sacrificial anode material made of an Al alloy containing 2.0 × 10 ⁹ / mm ³ or more, and an Al—S containing a predetermined amount of Si
An aluminum alloy composite for a heat exchanger, comprising clad with an i-based alloy brazing material. 2. The sacrificial anode material has a corrosion current value of 40 μA.
² / cm ² or less, the aluminum alloy composite for heat exchangers according to claim 1.