JPH04325644A - High strength al alloy tube stock for al heat exchanger excellent in pitting corrosion resistance - Google Patents

Abstract

PURPOSE:To improve the pitting corrosion resistance of a high strength Al alloy tube stock for Al heat exchanger. CONSTITUTION:One or >=2 elements among Ga, Cd, In, Sn, Tl, and Pb are incorporated, so that it comprises 1-100ppm based on the whole, as alloy components into an Al alloy which has a composition consisting of, by weight, 0.2-1.5% Fe, 0.05-1.2% Si, and the balance Al with inevitable impurities and further containing, if necessary, one or >=2 kinds among 0.05-0.15% Zr, 0.1-1.2% Mn, 0.02-0.2% Ti, and 0.05-0.3% Mg and which constitutes a high strength Al alloy tube stock for Al heat exchanger.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength Al alloy tube material that exhibits excellent pitting corrosion resistance when used as a tube material for brazing and assembling an Al heat exchanger.

0002

[Prior Art] Conventionally, Al heat exchangers such as radiators for automobiles and motorcycles, and even evaporators have been made of aluminum alloy tubes and aluminum alloy fins whose outer surfaces are clad with aluminum alloy brazing filler metal, or aluminum alloy tubes. It is manufactured by assembling and brazing an Al alloy fin material clad with an Al alloy brazing material on one or both sides, and as the Al alloy brazing material, Si: 7 to 12%, and if necessary, Mg: 0.1 to 2%, Bi: 0.02 to 0.
2%, one or two of them, and the rest is Al.
It is also known that an Al alloy having a composition consisting of unavoidable impurities is used.

[0003] In addition, in order to respond to the recent demands for higher performance, smaller size, and lighter weight Al heat exchangers, Al alloys with high strength that can be made thinner, such as Fe as described in ASTM8011, have been developed. :0.6~1%, Si:0.5~
It is also known that a high-strength Al alloy having a composition containing 0.9% Al and the remainder consisting of Al and unavoidable impurities is used as a tube material.

0004

[Problems to be Solved by the Invention] However, in the conventional high-strength Al alloy pipe material described above, since the Al alloy constituting the pipe material has high strength, especially high temperature strength, even if the wall thickness is reduced, thermal deformation occurs during brazing. However, due to the material, pitting corrosion is likely to occur, and this, combined with the thinness of the wall, leads to through holes, which leads to the end of the service life in a relatively short period of time.

[0005]

[Means for solving the problem] Therefore, the present inventors
From the above-mentioned viewpoint, we conducted research focusing on the conventional high-strength Al alloy pipe material mentioned above in order to develop an Al alloy pipe material that has high strength that can be made thinner and has excellent pitting corrosion resistance. , Ga, Cd, In, and Sn are added as alloy components to the Al alloy constituting the conventional high-strength Al alloy tube material.
, Tl, and Pb.
When contained in a proportion of 100 ppm, these alloy components diffuse and move to the inner and outer surfaces of the tube material during brazing and assembly of the Al heat exchanger, and the tube material in which the alloy components are agglomerated in this manner. The inner and outer surfaces of the pipe material become electrochemically significantly less noble, and the corrosion becomes a general corrosion type, which significantly suppresses the occurrence of pitting corrosion.On the other hand, the inner surface of the pipe material is As a result of diffusion and movement to the outer surface, these alloy components are almost non-existent, so the tube material itself has the same high strength as the conventional high-strength Al alloy tube material mentioned above, and is especially resistant to thermal deformation during brazing. The research results showed that it maintains high-temperature strength.

[0006] This invention was made based on the above research results.
:0.05~1.2%, Ga, Cd, In,
One or more of Sn, Tl, and Pb:
1 to 100 ppm, and if necessary,
Zr: 0.05-0.15%, Mn: 0.1-1.2%
, Ti: 0.02-0.2%, Mg: 0.05-0.3
%, and the rest is A.
High-strength Al for aluminum heat exchangers with excellent pitting corrosion resistance, which is made of an Al alloy having a composition consisting of l and inevitable impurities.
It is characterized by alloy tube material.

Next, the reason why the composition of the Al alloy constituting the high-strength Al alloy tube material of the present invention is limited as described above will be explained.

(a) Fe and Si These components have the effect of combining with Al to form various compounds that are finely and uniformly dispersed in the matrix, thereby improving high-temperature strength (heat deformation resistance). , its content is Fe
Even if the content is less than 0.2% or less than 0.05%, the desired high-temperature strength cannot be secured. If each exceeds 2%, the solid solution ratio of these components in the base material increases, resulting in a decrease in corrosion resistance and workability. Si:0
．． It was set at 0.05 to 1.2%.

(b) Ga, Cd, In, Sn, Tl, and Pb As mentioned above, these components have the ability to diffuse and move to the inner and outer surfaces of the pipe material and agglomerate during brazing. The inner and outer surfaces of the pipe material are relatively electrochemically significantly less noble, and as a result, the corrosion form on the inner and outer surface portions of the pipe material becomes a general corrosion type, which has the effect of completely eliminating the occurrence of pitting corrosion. However, if the content is less than 1 ppm, the desired effect cannot be obtained, while if the content exceeds 100 ppm, it will remain inside the pipe material after brazing, making it difficult to achieve the desired high-temperature strength. Since it would be difficult to secure the content, the content was set at 1 to 100 ppm.

(c) Zr, Mn, and Ti These components form various compounds and have the effect of improving high-temperature strength to prevent heat deformation during brazing and further improving room-temperature strength. , may be included if necessary,
The content is Zr: less than 0.05%, Mn: 0
．． If the content is less than 1% and Ti: less than 0.02%, the desired effect of improving the above action cannot be obtained; on the other hand, if the content is Zr: 0.15%, Mn: 1.2%, and Ti: 0
．． If it exceeds 2%, the formed compound will become coarse and rolling workability will deteriorate. .2
%, and Ti: 0.02 to 0.2%, respectively.

(d) Mg The Mg component has the effect of solidly dissolving in the base material and further improving the room temperature strength, so it is included as necessary.
If the content is less than 0.05%, the desired room temperature strength improvement effect cannot be obtained, while if the content exceeds 0.3%,
Since the high-temperature strength decreases, its content is set at 0.05 to 0.3%.

[0012] Next, the high-strength Al alloy tube material of the present invention will be specifically explained using examples.

[0013] Al alloys having the compositions shown in Tables 1 to 3 were melted using a normal melting method, and the following conditions were all normal: Width: 1450 mm x Length: 2800 m
Cast into a slab with dimensions of m x thickness: 400 mm,
After homogenizing this slab, it was hot rolled into a hot rolled plate with a thickness of 9 mm, and then cold rolled (final cold rolling ratio: 30%) was repeatedly applied while adding intermediate annealing to reduce the thickness. :
A 0.2 mm cold-rolled plate was used. For the purpose of evaluating high-temperature strength, a specimen for sagging resistance test with dimensions of width: 30 mm x length: 140 mm was cut out from this cold-rolled plate. High-strength Al alloy tube materials 1 to 15 of the present invention consisting of flat electric resistance welded tubes with width: 15 mm x thickness: 3 mm, and compositions that do not contain Ga, Cd, In, Sn, Tl, and Pb among the constituent components. Comparative high strength Al alloy tube materials 1 to 15 with
were manufactured respectively.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

The drooping resistance test was carried out under conditions equivalent to vacuum brazing, that is, approximately 10-4 torr, with a length of 30 mm in the length direction of the specimen being held horizontally and a length of 110 mm being extended horizontally. The test was carried out in a vacuum at a temperature of 600° C. for 5 minutes, and the hanging height of the protruding tip of the specimen after the test was measured.

Furthermore, the above-mentioned high-strength Al alloy tube material 1 of the present invention
- 15 and Comparative high-strength Al alloy tube materials 1 to 15 were similarly heat-treated under conditions equivalent to vacuum brazing, that is, in a vacuum of approximately 10-4 torr, and held at a temperature of 600°C for 5 minutes. (a) Cu2
Tap water immersion test containing 1 ppm of + ions and immersed in tap water at a temperature of 40°C for 30 days, (b) Cl- ions: 100 ppm, SO4 2- ions: 100 ppm
m, HCO3 − ion: 100 ppm, Cu2
An aqueous solution immersion test was conducted in which the sample was immersed in an aqueous solution containing 1 ppm of + ion at a temperature of 40° C. for 30 days, and the number of pitting corrosion per 40 cm 2 on the inner surface and the maximum depth of pitting corrosion were measured. These results are shown in Tables 4 and 5.

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

[Effects of the Invention] From the results shown in Tables 1 to 5, it is clear that Ga, Cd, In, Sn, Tl, and Pb were removed from the inner surface of the tube materials by brazing heating in high-strength Al alloy tube materials 1 to 15 of the present invention. (and the outer surface) and agglomerate, and these alloy components are not present inside the tube, so it is equivalent to comparative high-strength Al alloy tube materials 1 to 15 that do not contain these alloy components. It has high-temperature strength, and becomes electrochemically base due to the diffusion and aggregation of the trace alloy components on the inner surface of the pipe material, resulting in a general corrosion type.
It is clear that these tube materials exhibit much better pitting corrosion resistance than Alloy Tube Materials 1-15.

As mentioned above, the high-strength Al alloy tube material of the present invention has high strength, so even if it is thinned, it will not undergo thermal deformation during brazing, and as mentioned above, Ga, which is contained as an alloy component, Cd, In, Sn, Tl, and P
b diffuses and moves to the inner and outer surfaces of the tube material during brazing and assembly of the Al heat exchanger, electrochemically changing the inner and outer surface portions to be less noble, thereby creating holes in the inner and outer surface portions of the tube material. No corrosion occurs, and as a result, the Al heat exchanger exhibits excellent performance over a long period of time, giving it industrially useful properties.

Claims (4)

[Claims] Claim 1: Fe: 0.2 to 1.5%, Si: 0.
05 to 1.2%, and further contains Ga, Cd, In
, Sn, Tl, and Pb: 1 to 100 ppm, and the remainder consists of Al and unavoidable impurities (weight %). High-strength Al alloy tube material for Al heat exchangers with excellent pitting corrosion resistance. [Claim 2] Fe: 0.2 to 1.5%, Si: 0.
05-1.2%, Zr: 0.05-0.15
%, Mn: 0.1-1.2%, Ti: 0.02-0.2
%, and further contains one or more of the following:
One of Ga, Cd, In, Sn, Tl, and Pb
For an Al heat exchanger having excellent pitting corrosion resistance, the aluminum alloy is made of an Al alloy having a composition (by weight %) containing a species or two or more species: 1 to 100 ppm, and the remainder consisting of Al and unavoidable impurities. High strength Al alloy tube material. 3. Fe: 0.2 to 1.5%, Si: 0.
05-1.2%, Mg: 0.05-0.3%
, and further contains Ga, Cd, In, Sn, Tl,
and one or more of Pb: 1 to 100p
A high-strength A for an Al heat exchanger with excellent pitting corrosion resistance, characterized by being composed of an Al alloy having a composition (by weight %) containing .pm and the remainder consisting of Al and unavoidable impurities.
l Alloy tubing. 4. Fe: 0.2-1.5%, Si: 0.
05-1.2%, Zr: 0.05-0.15
%, Mn: 0.1-1.2%, Ti: 0.02-0.2
%, one or more of the following, and Mg: 0.05~
0.3%, and further contains Ga, Cd, In, Sn
, Tl, and Pb: 1 or more
A high-strength Al alloy tube material for an Al heat exchanger having excellent pitting corrosion resistance, characterized in that the tube material is made of an Al alloy having a composition (weight %) of 100 ppm and the remainder consisting of Al and unavoidable impurities.