JPH08165536A - Aluminum alloy for heat exchanger, excellent in corrosion resistance - Google Patents

Abstract

PURPOSE: To produce an aluminum alloy for heat exchanger, improved in corro sion resistance so that thinning is made possible. CONSTITUTION: This alloy is an aluminum alloy for heat exchanger, having a composition consisting of 0.6-1.5% Mn, 0.10-0.80% Cu, 0.06-0.30% Ti, <=0.30% Fe, <=0.20% Si, one or more kinds among 0.03-0.30% W, 0.03-0.% Mo, and 0.03-0.50% Co, and the balance Al with inevitable impurities. Moreover, this alloy is an aluminum alloy for heat exchanger, having a composition further containing, besides those components, one or >=2 kinds selected from among 0.06-0.40% Mg, 0.06-0.25% Cr, and 0.06-0.25% Zr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structural material for a heat exchanger such as a header plate of a heat exchanger for an automobile, a core material of a clad material for a fluid passage of water or the like in a brazing structure such as a drone cup. The present invention relates to an aluminum alloy used as.

[0002]

2. Description of the Related Art Heat exchangers for automobiles include oil coolers, intercoolers, radiators, evaporators and condensers for air conditioners. Among such heat exchangers for automobiles, header plates or drone cups may be used. For the attached structure, an aluminum brazing sheet in which an aluminum brazing material (skin material) is clad on one side or both sides of an aluminum alloy core material (structural material) is often used.

As a core material for such a brazing sheet, an Al--Mn system or Al--Mn--Cu is generally used.
Type, Al-Mn-Mg-Cu type and other alloys mainly containing Mn are used, and typical examples thereof include 3003 alloy and 3005 alloy, and also Al-Mg-Si. 6951 alloy and the like are also used. On the other hand, as the brazing material (skin material) of the brazing sheet, Al-Si-based, Al-Si-Mg-based, Al-S
An aluminum alloy for brazing, which mainly contains Si, such as i-Mg-Bi system is used.

[0004]

The core material of the brazing sheet in the brazing structure of the aluminum alloy heat exchanger is required to have excellent corrosion resistance and to have the mechanical strength required as a structural material. Required. Conventionally used as the core material of this type of brazing sheet 3
The 003 alloy and the 6951 alloy had relatively good corrosion resistance and were able to secure a certain degree of mechanical strength. However, in recent years, there has been an increasing demand for weight reduction and cost reduction in heat exchangers for automobiles, etc. Therefore, the thickness of structural materials for heat exchangers represented by the core material of brazing sheet for heat exchangers is further reduced. Therefore, it is strongly required to further increase the material strength so that sufficient mechanical strength can be obtained even if the wall thickness is reduced, but it is also strongly required to further improve the corrosion resistance. It has been demanded.

That is, a typical form of corrosion in the heat exchanger structural material is pitting corrosion. If pitting corrosion progresses when the wall thickness is reduced, the pitting corrosion penetrates in the plate thickness direction. , As a result, outflow of water and air inside and outside the heat exchanger,
Inflow occurs and the heat exchange function does not work properly. Therefore, in order to ensure sufficient durability of the heat exchanger while reducing the wall thickness, it is necessary to further improve the corrosion resistance as compared with the conventional case. In general, aluminum alloys such as core materials for brazing sheets tend to have lower corrosion resistance when attempting to increase strength, and therefore, when thinning and increasing strength, sufficient corrosion resistance is ensured. There is a problem that it is difficult to do so, and in reality, there is a limit to thinning and strengthening.

The present invention has been made in view of the above circumstances, and includes a core material of a brazing sheet for a heat exchanger,
As an aluminum alloy used for a heat exchanger, an object thereof is to provide an aluminum alloy having particularly excellent corrosion resistance.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, as a result of the inventors' earnest experiments and studies,
The Al-Mn-Cu system is used as a base, and Ti is added thereto, and at least one of W, Mo, and Co is added in an appropriate amount, so that the corrosion resistance is much higher than that of conventional aluminum alloys for heat exchangers. The present invention has been made and the present invention has been accomplished.

Specifically, the aluminum alloy for a heat exchanger according to the invention of claim 1 has a Mn content of 0.6 to 1.5%, Cu0.
10 to 0.80%, Ti 0.06 to 0.30%, Fe
Contains 0.30% or less, Si 0.20% or less, and W
0.03-0.30%, Mo 0.03-0.30%, C
It is characterized by containing one or more selected from 0.03 to 0.50% and the balance being Al and inevitable impurities.

The aluminum alloy for a heat exchanger according to a second aspect of the present invention is Mn 0.6 to 1.5%, Cu 0.10 to
0.80%, Ti0.06-0.30%, Fe0.30
% Or less, Si 0.20% or less, and W0.03
~ 0.30%, Mo0.03 ~ 0.30%, Co0.0
3 to 0.50%, and one or more selected from the group of Mg0.06 to 0.40%, Cr0.
It is characterized by containing one or more selected from the range of 06 to 0.25% and Zr of 0.06 to 0.25%, and the balance being Al and inevitable impurities.

[0010]

First, the reasons for limiting the alloy components in the present invention will be explained.

Mn: Mn is an alloying element which is a basic element of the alloy of the present invention, is an element effective for increasing the strength and at the same time effective for improving the corrosion resistance, and further brazing property. Is effective in improving. Mn content is 0.
If it is less than 6%, these effects cannot be sufficiently obtained, while 1.
If it is added in excess of 5%, a huge intermetallic compound is formed, resulting in a decrease in workability and corrosion resistance and an increase in intergranular corrosion susceptibility. Therefore, the Mn content is 0.6 to 1.5%
Within the range of.

Cu: Cu is used as a core material of a brazing sheet to make the potential of the core material noble, to increase the potential difference between the core material and the sacrificial anode effect of the solder material, and to enhance the strength after brazing. Is effective for. If Cu is less than 0.10%, these effects are small. On the other hand, if added over 0.80%, the self-corrosion resistance decreases, and intergranular corrosion becomes severe, resulting in deterioration of the corrosion resistance. Therefore, the amount of Cu is set within the range of 0.10 to 0.80%.

Ti: Ti contributes to the improvement of corrosion resistance by changing the pit-like corrosion form into a layered form, delaying the progress of corrosion in the plate thickness direction, and reducing the maximum corrosion depth. If the addition amount of Ti is less than 0.05%, the effect is not sufficiently exhibited, while if it exceeds 0.30%, the effect is saturated and the economical efficiency is impaired, and a giant intermetallic compound of Al ₃ Ti is formed. As a result, the moldability is lowered. Therefore, the addition amount of Ti is set within the range of 0.06 to 0.30%.

Fe: Fe is an impurity element that is inevitably contained in ordinary aluminum alloys, and is Al-F.
e-type, Al-Fe-Mn-type, and Al-Fe-Mn-Si-type intermetallic compounds are formed as crystallized substances and precipitates, and these intermetallic compounds serve as a cathode for the Al matrix and are electrochemically formed. Since it lowers the corrosion resistance, it is desirable that the Fe content be as small as possible. In particular, if the Fe content exceeds 0.30%, the corrosion resistance is severely deteriorated.
The content of e is determined to be 0.30% or less as an impurity.

Si: Si is also an impurity element that is unavoidably contained in a normal aluminum alloy, and coexists with Fe to crystallize an Al-Fe-Si-based or Al-Fe-Mn-Si-based intermetallic compound. It is desirable that the amount of Si is as small as possible, because a substance or a precipitate is generated and these intermetallic compounds serve as a cathode for the Al matrix to reduce the corrosion resistance. In particular, if the amount of Si exceeds 0.20%, the corrosion resistance deteriorates drastically.
It was decided to regulate to 0% or less.

W, Mo, Co: These elements are positively added elements in the present invention, and any one kind or two or more kinds are added for improving the corrosion resistance. That is, any of these elements contributes to the improvement of corrosion resistance by changing the pit-like corrosion form into a layered form, delaying the progress of corrosion in the plate thickness direction, and reducing the maximum corrosion depth. Further, any of these elements is effective as a core material of a brazing sheet to make its potential noble and increase the potential difference from the brazing material to enhance the sacrificial anode effect of the brazing material. If the addition amount of each element is less than 0.03%, these effects cannot be sufficiently obtained. On the other hand, if the addition amounts of W and Mo exceed 0.30%, respectively, and if the addition amount of Co exceeds 0.50%, a giant intermetallic compound is formed and formability is lowered in any case. Therefore W, M
The addition amount of o is within the range of 0.03 to 0.30%,
The amount of Co added was in the range of 0.03 to 0.50%.

Mg, Cr, Zr: In the invention of claim 2, one or more of these are positively added in order to further enhance the strength after the heat of brazing. Of these, Mg is the most effective element for increasing the strength after brazing addition heat, but if Mg is less than 0.06%, its effect is not sufficiently obtained, while Mg exceeds 0.40%. When added as Mg, the amount of Mg in the case of adding Mg is 0.06 to 0.
It was set within the range of 40%. Cr and Zr are also effective elements for increasing the strength after brazing addition heat, but if each is less than 0.06%, the effect is not sufficiently obtained, while on the other hand, if added in excess of 0.25% respectively. If so, a huge intermetallic compound is formed and workability is deteriorated. Therefore Cr
Alternatively, the amount of addition of Zr is 0.
It was set within the range of 06 to 0.25%. Of course, even in the aluminum alloy of the first aspect of the present invention, Mg, Cr, and Zr may be contained as impurities in an amount of less than 0.06%, respectively.

In addition to the above elements, Al and Fe,
It may be an unavoidable impurity other than Si, but if each impurity element is 0.05% or less, the performance targeted by the present invention is not particularly impaired. However, Sn, Pb,
Even if a small amount of Ga is used, the potential of the core material of the brazing sheet may become base and the corrosion resistance may be impaired. Therefore, it is desirable that the content of each Ga be controlled to 0.02% or less.

When the aluminum alloy for heat exchangers of the present invention having the above-described composition is used as the core material of a brazing sheet, a brazing material is clad on one side or both sides. In that case, the brazing material may be an Al-Si alloy, an Al-Si-Mg alloy, or an Al-Si-Mg.
-Bi alloy or the like can be used, and specific standard alloys thereof include 4003 alloy, 4004 alloy, 410
4 alloy, 4005 alloy, 4N04 alloy, 4045 alloy,
Although there are 4343 alloy, 4145 alloy, 4047 alloy and the like, the present invention is not particularly limited to these, and a brazing material to which other elements such as Be, Cu, Zn, In and Sn are added may be used. Note that the brazing material clad ratio when used as a brazing sheet depends on the plate thickness,
Usually, about 5 to 20% per one surface is preferable.

The method for producing the aluminum alloy for a heat exchanger according to the present invention is not particularly limited and may be in accordance with a conventional method. In particular, when it is used as a brazing material and clad as a core material of a brazing sheet. A preferred example of the brazing sheet manufacturing method is shown below.

That is, the core material is cast by a semi-continuous casting method (DC casting method) at a cooling rate of 0.05 to 100 ° C./second, and the core ingot is obtained at about 530 to 620 ° C. The homogenization treatment is performed for about 1 to 12 hours. By performing the homogenizing treatment at such a temperature, the Al-Mn-based crystallized substance becomes coarse, which is effective in preventing the erosion of the brazing material during brazing. After homogenizing and chamfering, place brazing material on one or both sides and
Hot clad rolling is performed at a temperature of about 50 to 520 ° C. Then, cold rolling is performed at a rolling rate of 60% or more, and then final annealing is performed at 300 to 550 ° C. As the final annealing method, either annealing in a batch furnace or short-time annealing in a continuous annealing furnace may be applied.
If necessary, intermediate annealing may be performed after hot clad rolling or in the middle of cold rolling.

When assembling a brazing structure using the brazing sheet using the aluminum alloy for a heat exchanger of the present invention as a core material, a vacuum brazing method, a flux brazing method, a non-corrosive flux brazing method, etc. Is preferably applied, but is not limited to these.

[0023]

EXAMPLE An example in which a brazing sheet is formed by using the aluminum alloy for a heat exchanger according to the present invention as a core material will be described below.

Alloys for core materials having compositional compositions shown in alloy numbers 1 to 25 in Table 1 were DC-cast according to a conventional method, and each ingot was homogenized at 600 ° C. for 10 hours, and then both surfaces were chamfered. , A brazing material made of JIS 4104 alloy is superposed on both sides of the core material at a thickness of 15% per side, and
Hot clad rolling was performed at 0 ° C. to obtain a hot rolled clad plate having a thickness of 3.0 mm. Then by cold rolling, plate thickness 0.5m
After setting m, final annealing was performed at 370 ° C. for 5 hours to obtain an O material.

The clad plate (brazing sheet) obtained as described above is press-formed into a basin shape, washed with a solvent, and then the basin-shaped molded bodies are alternately inverted and stacked vertically. 600 ° C in a vacuum of × 10 ^-5 Torr
After heating for 3 minutes, the brazing heat was applied by quenching. Figure 1 shows the appearance of the tank-shaped structure after brazing. FIG. 1
In FIG. 1, reference numeral 1 indicates each press-formed product, and reference numeral 2
A brazing part is shown.

The tank-shaped structure obtained as described above was subjected to a 1500-hour corrosion test by the CASS test according to JIS H8681, and the maximum pit depth was measured as a corrosion resistance evaluation. The results are shown in Table 2.

[0027]

[Table 1]

[0028]

[Table 2]

As is clear from Table 2, when the brazing sheet using the core material according to the present invention is used (alloy symbols 1 to 10), the maximum pit depth is at most 0.18 m.
m was about 0.12 mm on average, and it was confirmed to have excellent corrosion resistance.

On the other hand, a comparative example of alloy No. 11 in which Ti, W, Mo and Co were not added and the amount of Fe was excessive (300
3) (corresponding to 3 alloys) and Comparative Example of alloy No. 12 in which W, Mo and Co were not added, it was found that pitting corrosion penetrated in the plate thickness direction, resulting in poor corrosion resistance. On the other hand, the comparative example of Alloy No. 13 is an example in which the amount of Mn is excessive, but in this case, since the formability was poor, cracking occurred during pressing, and the corrosion test could not be carried out. Furthermore M
In the comparative example of alloy number 14 in which the amount of n was too small, the comparative example of alloy number 15 in which Cu was not added, and the comparative example of alloy number 16 in which the amount of Cu was excessive, pitting corrosion occurred in the plate thickness direction. It was found that it penetrated and the corrosion resistance was inferior. Further, a comparative example of alloy No. 17 having an excessive amount of W, an alloy No. 18 having an excessive amount of Mo
Comparative Example of Alloy No. 19 having an excessive amount of Co and an excessive amount of Si, Comparative Example of Alloy No. 20 having an excessive amount of Cr,
In each of the comparative examples of alloy No. 21 in which the amount of Zr was excessive, all of them had poor formability, so cracking occurred during press forming, and the corrosion test could not be performed. Further, a comparative example of alloy number 22 having an excessive Fe content, a comparative example of alloy number 23 having an excessive Mg content,
Also, in the comparative example of Alloy No. 24 having an excessive Si amount, it was found that pitting corrosion penetrated in the plate thickness direction, and the corrosion resistance was poor. In addition, alloy No. 2 with too little Ti addition
In the comparative example of 5, the maximum pitting depth reaches 0.30 mm,
The corrosion resistance was inferior to that of the case of the present invention.

From the above test results, an appropriate amount of M
n, Cu as a basic component, the amount of Fe, Si is appropriately regulated, and an appropriate amount of Ti is added, and at the same time W, M
The aluminum alloy for a heat exchanger of the present invention, in which a predetermined amount of at least one of O and Co is added, and further, a predetermined amount of Mg, Cr, and Zr is added as required, is excellent in corrosion resistance, particularly pitting corrosion resistance. It is clear.

[0032]

The aluminum alloy for heat exchangers of the present invention has good corrosion resistance, particularly pitting corrosion resistance. Therefore, it can be thinned as a structural material for heat exchangers, such as a brazing sheet core material for heat exchangers. Therefore, the weight and cost of the heat exchanger can be reduced.

The aluminum alloy for a heat exchanger of the present invention is most suitable as a core material of a brazing sheet, but it is needless to say that it can be used as a bare material.

[Brief description of drawings]

FIG. 1 is a perspective view showing a tank-shaped structure applied in an embodiment of the present invention.

Claims (2)

[Claims] 1. Mn 0.6 to 1.5% (weight%, the same hereinafter), Cu 0.10 to 0.80%, Ti 0.06 to 0.
30%, Fe 0.30% or less, Si 0.20% or less, and W0.03 to 0.30%, Mo0.03 to
Heat exchange with excellent corrosion resistance, characterized by containing one or more selected from 0.30% and Co0.03 to 0.50%, and the balance being Al and inevitable impurities. Aluminum alloy for dexterity. 2. Mn 0.6 to 1.5%, Cu 0.10
0.80%, Ti0.06-0.30%, Fe0.30
% Or less, Si 0.20% or less, and W0.03
~ 0.30%, Mo0.03 ~ 0.30%, Co0.0
3 to 0.50%, and one or more selected from the group of Mg0.06 to 0.40%, Cr0.
06-0.25%, Zr0.06-0.25%, containing 1 type or 2 types or more selected, and the balance consisting of Al and unavoidable impurities, and excellent in corrosion resistance. Aluminum alloy for heat exchangers.