JPH09256093A - High strength aluminium alloy tube material for heat exchanger, excellent in pitting corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high strength Al alloy tube material for heat exchanger, having high strength, capable of thinning, and excellent in pitting corrosion resistance. SOLUTION: This material is an Al alloy tube material for heat exchanger, prepared by cladding the inside of the main body of tube material composed of Al alloy with a sacrificial anode material composed of Al alloy and also cladding the outside of the main body with a brazing filler metal composed of Al-Si alloy or Al-Si-Mg alloy. At this time, the main body of the tube material is composed of an Al alloy having a composition consisting of, by weight, 0.8-1.5% Mn, 0.5-1.2% Si, 0.05-0.25% Zr, 0.05-0.25% Ti, and the balance Al with inevitable impurities. Further, the sacrificial anode material is composed of an Al alloy having a composition consisting of 0.05-0.2% Sn, 0.4-0.7% Fe, 1.3-2% Mg, and the balance Al with inevitable impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al alloy pipe material for a heat exchanger, which has excellent pitting corrosion resistance and high strength, thereby making it possible to reduce the wall thickness.

[0002]

2. Description of the Related Art Conventionally, a sacrificial anode material made of an Al alloy is generally clad inside a pipe material body made of an Al alloy,
An Al alloy pipe material obtained by clad with a brazing material made of an Al-Si alloy or an Al-Si-Mg alloy on the outer side is
It is well known that a heat exchanger is manufactured by assembling it with fin material and brazing it.
Further, as the Al alloy pipe material, for example, Japanese Patent Laid-Open No. 6-1
Many others are known, including the one described in Japanese Patent No. 28675.

[0003]

On the other hand, in recent years, there has been a strong demand for weight reduction and size reduction of heat exchangers. With this demand, in particular, the Al alloy pipe material as a structural member of the heat exchanger tends to be thin. If the thickness of the Al alloy pipe material is reduced, it is inevitable to shorten the service life due to pitting corrosion. Therefore, in order to reduce the thickness of the Al alloy pipe material, not only high strength but also significant improvement of pitting corrosion resistance is indispensable under the present circumstances. .

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above viewpoints, as a result of research to develop a high-strength Al alloy pipe material for heat exchangers having excellent pitting corrosion resistance, as a result, a brazing material clad on the outside of the pipe body has a normal composition of Al-Si. Mn: 0.8-1.% By weight (hereinafter,% means% by weight) of the tube body constituting the Al alloy tube under the condition that the alloy is Al-Si-Mg alloy.
5%, Si: 0.5 to 1.2%, Zr:
0.05-0.25%, Ti: 0.05-0.
25%, and the balance is made of an Al alloy having a composition of Al and inevitable impurities, and a sacrificial anode material clad inside the alloy is Sn: 0.05 to 0.2.
%, Fe: 0.4 to 0.7%, Mg: 1.3
.About.2%, and the remainder being composed of an Al alloy having a composition of Al and unavoidable impurities, the resulting Al alloy pipe material is assembled with a fin material by brazing to form a heat exchanger, The tube body has a fine Al-Mn-Si-based compound or Al-Zr-based compound in the matrix,
Further, a structure in which an Al-Ti-based compound is dispersed and deposited is formed, whereby high strength that enables thinning is ensured, and the sacrificial anode material is an Al layer surrounded by a thin metal Sn layer in the matrix. ₃ Fe were mainly Al-Fe
A system in which the base compound is finely and uniformly dispersed and deposited, and the amount of solid solution of Sn in the base portion adjacent to the metal Sn thin layer is relatively high is formed. Since the relatively high base portion is electrochemically the most base, in practical use, this portion is preferentially melted, and this is finely and uniformly dispersed in the base material.
Since it is generated around the individual l-Fe compounds, the corrosion form becomes a general corrosion form. Therefore, even if the pipe body is thinned, pitting corrosion is significantly suppressed in the pipe body, and the pipe body is well protected. I got the research result that I will come to do.

The present invention was made on the basis of the above-mentioned research results, and Al- having an ordinary composition on the outside is formed.
Mn: 0.8-1.5 was added to the tube body main body clad with a brazing material made of Si-based alloy or Al-Si-Mg-based alloy.
%, Si: 0.5 to 1.2%, Zr: 0.
05-0.25%, Ti: 0.05-0.25
%, With the balance being Al and unavoidable impurities
A sacrificial anode material composed of an alloy and clad inside the body of the tubular material is Sn: 0.05 to 0.2%,
Fe: 0.4 to 0.7%, Mg: 1.3 to 2%,
It is characterized by a high-strength Al alloy pipe material for a heat exchanger, which is excellent in pitting corrosion resistance and is made of an Al alloy containing Al and the balance of Al and inevitable impurities.

Next, the reason why the composition of the Al alloy forming the pipe body of the Al alloy pipe and the sacrificial anode material of the present invention is limited as described above will be explained. (1) Al alloy of the pipe body (a) Mn and Si These components are finely and uniformly dispersed as Al-Mn-Si-based compound in the matrix at a brazing heat temperature of about 600 ° C, especially during brazing. Although dispersed and precipitated, which has the effect of improving the strength, the content of Mn: less than 0.8% and Si: less than 0.5% results in insufficient formation of an Al-Mn-Si compound. The desired high strength cannot be ensured. On the other hand, if the content exceeds Mn: 1.5%, the moldability decreases, and if the content exceeds Si: 1.2%, the toughness decreases. Therefore, Mn:
0.8-1.5%, preferably 0.8-1.2%, S
i: 0.5 to 1.2%, preferably 0.6 to 1.0%.

(B) Zr and Ti Al-Zr-based compounds and Al-Ti-based compounds, which are finely and uniformly dispersed in the matrix, are formed in these components, and these components are combined with the Al-Mn-Si-based compounds. In the coexistence of, there is an effect of further improving the strength, but if the content is less than Zr: 0.05% or Ti: less than 0.05%, the desired strength improving effect cannot be obtained, while the content thereof is When Zr exceeds 0.25% and Ti: 0.25%, the moldability is particularly deteriorated. Therefore, the content is Zr: 0.05 to 0.25%, preferably 0. .05
.About.0.15%, Ti: 0.05 to 0.25%, and preferably 0.05 to 0.15%.

(2) Al alloy of sacrificial anode material (a) Sn and Fe These components are contained in the solid solution of Sn as described above,
A fine Al-Fe compound surrounded by a thin metal Sn layer is uniformly dispersed and distributed, and at the time of brazing, the metal Sn is
By re-dissolving a part of the thin layer in the matrix, a matrix part having a relatively high Sn solid solution amount forms a structure formed adjacent to the metal Sn thin layer, and in practical use, the fine uniform The peripheral portion of the Al-Fe-based compound dispersed and distributed in the first embodiment has the effect of significantly suppressing the occurrence of pitting corrosion by adopting the general corrosion mode in which the Al-Fe compound is preferentially dissolved at the same time.
If it is less than 05%, the formation of the metallic Sn thin layer and the base portion having a relatively high Sn content is insufficient, and even if the Fe content is less than 0.4%, it is possible to disperse and precipitate in the base material. However, if the Sn content exceeds 0.2%, the dissolution rate of the sacrificial anode material will rapidly increase, and the desired pitting corrosion resistance cannot be ensured. It is not desirable in terms of service life, and when the Fe content exceeds 0.7%, the Al-Fe compound becomes coarse,
Since it becomes impossible to uniformly disperse and distribute the fine Al-Fe-based compound in the matrix, pitting easily occurs, so that the content of each is Sn: 0.05 to 0.2.
%, Preferably 0.05 to 0.15%, Fe: 0.4 to
It was set to 0.7%, preferably 0.5 to 0.6%.

(B) Mg The Mg component promotes precipitation of an Al-Fe-based compound as a solid solution in the matrix and re-dissolution of Sn from the metallic Sn thin layer to the matrix part during brazing, thereby providing electric conductivity. Although it has an effect of contributing to the formation of the chemically least base material part, if its content is less than 1.3%, the above effect cannot be sufficiently exerted, so that a desired pitting corrosion resistance improving effect is obtained. On the other hand, if the content exceeds 2%, the base material hardens and the moldability comes to deteriorate, so the content is set to 1.
It was set to 3 to 2%, preferably 1.4 to 1.8%.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the Al alloy pipe material of the present invention will be specifically described by way of Examples. All are Al for pipe body having the composition shown in Tables 1 and 2 under normal conditions.
Alloys A to M, Al alloys a to j for sacrificial anode material, and Al alloys a to o for brazing material are melted and cast into ingots,
After subjected to homogenizing heat treatment, hot rolled to a plate thickness of 7.5 m.
m, and the resulting Al alloy hot-rolled sheet for sacrificial anode material and Al alloy hot-rolled sheet for brazing material were subjected to cold rolling while applying intermediate annealing, and each had a thickness of 1.5 m.
m and 1 mm cold-rolled sheets, then these were stacked in the combinations shown in Table 3, clad by hot rolling, and subsequently cold-rolled while applying intermediate annealing to obtain a sheet thickness of 0.2 mm. A cold-rolled sheet is formed by electric resistance welding from this cold-rolled sheet. The flat aluminum alloy pipe materials 1 to 15 of the present invention and the comparative Al alloy pipe materials 1 to 15 having a cross-sectional outer diameter dimension of 16 mm in width and 8 mm in thickness. 7 were each manufactured. In addition, the comparative Al alloy pipe materials 1 to 7 have a content of any one of the alloy components of the Al alloy constituting the pipe body and the sacrificial anode material (the components marked with * in Tables 1 and 2). This is outside the scope of the present invention.

Then, the various Al alloy pipe materials obtained as a result are subjected to the same conditions as the brazing process performed in the production of the heat exchanger, that is, those using the Al alloys A to D for the brazing material in a nitrogen atmosphere. One using Al alloy for brazing material is 1
After heating in a vacuum of 0 ^-4 torr at a temperature of 595 ° C. for 7 minutes, tap water at 90 ° C. containing 1 ppm Cu ²⁺ in the pipe for the purpose of evaluating pitting corrosion resistance Was carried out for 12 weeks, and the maximum pitting depth on the inner surface of the tube was measured after the test. Table 3 shows the results of these measurements. In addition, Table 3 also shows the measurement results of the tensile strength of the Al alloy pipe material after the heat treatment for the purpose of evaluating the strength.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

[0015]

From the results shown in Table 3, in the Al alloy pipe materials 1 to 15 of the present invention, high strength is ensured by the pipe body constituting them and excellent pitting corrosion resistance is obtained by the sacrificial anode material. In contrast, comparative Al alloy pipe material 1
As can be seen in ~ 7, the Al of the main body of the pipe material constituting this
If the content of any one of the alloy components in the alloy deviates from the range of the present invention to the lower side, it becomes difficult to secure high strength, and similarly, in the Al alloy of the sacrificial anode material, pitting corrosion resistance It is clear that a drop in the is inevitable. As described above, the Al alloy pipe material of the present invention is
High strength is ensured by the tube material body that constitutes this, and excellent pitting corrosion resistance is secured by the sacrificial anode material, so even if it is thinned and applied to a heat exchanger, pitting corrosion does not occur, It has excellent properties and has industrially useful properties such as contributing to weight reduction and size reduction of the heat exchanger.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Itagaki 82-1 Inari, Susono City, Shizuoka Prefecture (72) Inventor Tomo Ken 46-3 Fujimidai, Mishima City, Shizuoka Prefecture

Claims (1)

[Claims] 1. A sacrificial anode material made of an Al alloy is clad on the inside of a pipe material body made of an Al alloy, and Al-S is formed on the outside.
In an Al alloy pipe material for a heat exchanger, which is obtained by clad with a brazing material made of an i-based alloy or an Al-Si-Mg-based alloy, the pipe material main body is, by weight%, Mn: 0.8 to 1.5%, Si: 0.5 ~
1.2%, Zr: 0.05 to 0.25%, Ti: 0.05
.About.0.25%, with the balance being composed of an Al alloy having a composition of Al and unavoidable impurities, and the sacrificial anode material, in the same weight%, Sn: 0.05-0.2%, Fe: 0.4-
High strength for heat exchanger with excellent pitting corrosion resistance, characterized by being composed of an Al alloy containing 0.7%, Mg: 1.3 to 2%, and the remainder being a composition of Al and inevitable impurities. Al alloy pipe material.