JPH04198447A - Aluminum alloy clad material having high strength and high corrosion resistance for heat exchanger - Google Patents

Abstract

PURPOSE:To obtain an Al alloy clad material excellent in brazability and having high strength and high corrosion resistance by cladding both surfaces of a core material composed of an Al alloy having a specific composition reduced in Mg content with a sacrificial anode material composed of Al alloy of specific composition and a cladding material composed of Al-Si alloy brazing filler metal, respectively. CONSTITUTION:One side of a core material composed of an Al alloy having a composition consisting of, by weight, 0.3-2.0% Mn, 0.25-0.8% Cu, 0.2-1.0% Si, <=0.5% Mg, <=0.35% Ti, and the balance Al with inevitable impurities is clad with a sacrificial anode material, and the other side is clad with a cladding material. The above sacrificial anode material is an Al alloy which has a composition consisting of 1.2-2.5% Mg, 0.2-0.8% Si, 0.5-2.0% Zn, and the balance Al with inevitable impurities and further containing, if necessary, one or more kinds among <=0.2% In, <=0.2% Sn, and <=0.2% Ga. Further, the above cladding material is a brazing filler metal of Al-Si alloy. By this method, the Al alloy clad material suitable for structural member for Al heat exchanger production, excellent in brazability, and having high strength and high corrosion resistance after brazing can be obtained.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention provides aluminum for radiators, heater cores, etc. by brazing using fluoride flux in an inert gas atmosphere.
When manufacturing heat exchangers.

This invention relates to an Al alloy clad material that has good brazing properties, high strength and high corrosion resistance after brazing, and is suitable for use as structural members such as tube materials and header plate materials. Suitable for the tubing material used.

[Prior art] Tube materials and header plate materials for automobile radiators, heater cores, etc. have an Al-Mn alloy such as 3003 as the core material, an Al-Si alloy wax on one side, and an Al-Si alloy on the other side. Al-Zn alloys and A I -Z n -M
A three-layer cladding material made of a sacrificial anode material made of a g-based alloy is used.

The Al-3i brazing material is used for joining tubes and fins and for joining tubes and header plates.

Brazing is often performed using fluoride flux in an inert gas atmosphere. The other side clad with sacrificial anode material turns inside (water side) during use and acts as a sacrificial anode to prevent pitting and crevice corrosion of the core material.

In recent years, there has been a strong demand for lighter weight products such as radiators and heater cores, making it necessary to make tube materials and header plate materials thinner. For this purpose, it is necessary to increase the strength of the material, especially the strength after brazing, and Mg is increasingly being added to the core material to increase the strength. However, Mg diffuses to the surface of the brazing material and reacts with the fluoride flux, resulting in formation and adhesion of flocculent products (Mg fluoride) and poor bonding. In this way, the amount of Mg added to the core material is limited to 0.5% at most, and in practice to 0.2 to 0.3%, which is an obstacle to increasing the strength.

The strength of the tube material and header plate material may also be improved by adding Mg to the sacrificial anode material. Regarding the cladding material in which Mg is added to the sacrificial anode material,
There have been several proposals so far.

That is, a method of containing 0Mg, Zn, etc. in the sacrificial anode material of the radiator header plate material and tube material (Japanese Patent Publication No. 63-287
No. 04), ■Method of adding Zn and Mg (Japanese Unexamined Patent Publication No. 61-89498)
(No.), ■Method of simultaneously adding Sn and Mg (JP-A-56-1fl)
i648, JP-A No. 63-89641), ■method of adding M g (!: Z n ) up to a relatively high concentration (
Special Publication No. 62-45301) has been proposed.

However, the addition of Mg in (1) and (2) above is as small as 1.1% or 1.5% or less, and is added to prevent pitting corrosion and crevice corrosion, so no improvement in strength can be obtained.

The purpose of the addition of Mg in (2) above is to suppress the grain boundary diffusion of Sn and prevent cracking during hot rolling, and the purpose of the addition of Mg in (2) above is to improve pitting corrosion resistance. M
When g is at a high concentration, it may diffuse into the core material and may also provide a certain degree of strength improvement effect. However, when a thin tube material (cladding material) is made, even though the strength of the core material can be increased by Mg diffused from the sacrificial anode material, the strength of the sacrificial anode material is insufficient due to the addition of Mg alone. It is not possible to increase the strength of the entire cladding material. That is, when the thickness becomes thinner, not only the core material but also the sacrificial anode material contribute to the strength, and it is necessary to increase the strength of the sacrificial anode material.

[Problems to be Solved by the Invention] Therefore, the present invention provides brazing without impairing properties, that is, while suppressing the amount of Mg added to the core material to a maximum of 0.5%.
Brazing is intended to provide a cladding material that will later provide high strength.

[Means for Solving the Problems] The present inventors have studied a method that can obtain high strength after brazing while keeping the amount of Mg added in the core material to a maximum of 0.5%. When high concentrations of Mg and St are added to the sacrificial anode material, some of the Mg in the sacrificial anode material diffuses into the core material during brazing, strengthening the core material, and the sacrificial anode material itself also contains Mg. The present invention was completed based on the discovery that the material is strengthened by Si.

That is, by making Mg and Si coexist in the sacrificial anode material, Mg
In addition to contributing to strengthening the core material, Mg is added to the sacrificial anode material.
It is strengthened by solid solution strengthening with □ and Si and age hardening due to precipitation of Mg2Si.

That is, the structure of the present invention is as follows: (1) The core material has Mn: 0.3 to 2.0%, Cu
: 0.25-0.8%, Si: 0.2-1.0
%, Mg: 0.5% or less, Ti: 0.35% or less, and the remainder is Al and unavoidable impurities. g: 1.2-2.5%, S
i: 0.2-0.8%, Zn:
It is composed of an aluminum alloy containing 0.5 to 2.0% and the balance is Al and unavoidable impurities, and the leather composite on the other side of the core material is a brazing material of an Al-Si alloy. A high-strength, high-corrosion-resistant aluminum alloy clad shrine for heat exchangers, characterized in that: (2) the core material is Mn: 0.3-2.0%, Cu;
: 0.25-0.8%, Si: 0.2-1.0
%, Mg: 0.5% or less, Ti: 0.35% or less, the remainder being Al and inevitable impurities, and the sacrificial anode material composited on one side of the core material is Mg: l, 2-2.5%, Si: 0.2-0
．． 8%, Zn: 0.5 to 2.0%, and further contains one or two of In2: 0.2% or less, Sn: 0.2% or less, and Ga: 0.2% or less. The skin material is composed of an aluminum alloy containing at least 100% of Al species and the remainder is Al and unavoidable impurities, and the skin material is composited on the other side of the core material.
This is a high-strength, high-corrosion-resistant aluminum alloy cladding material for a heat exchanger, characterized in that it is composed of an l-Si alloy braze.

[Operations] The reasons for limiting the composition and composition range in the present invention will be described.

(1) Core material Mn+ Mn improves strength. In addition, the potential of the core material is increased to increase the potential difference with the sacrificial anode material, thereby improving corrosion resistance. 0
．． If it is less than 3%, the effect will not be sufficient, and if it exceeds 2.0%, coarse compounds will be produced during casting, making it impossible to obtain a sound plate.

Cu: Cu makes the potential of the core material more noble, increases the potential difference between the sacrificial anode material and the brazing material, and the core material, and increases the anticorrosion effect of the sacrificial anode material and the brazing material due to the sacrificial anode effect. Furthermore, Cu in the core material diffuses into the sacrificial anode material and the brazing material during brazing, forming a gentle concentration gradient, with the core material being at a higher potential and the surface sides of the sacrificial anode material and the brazing material being less noble. potential, and a gentle potential distribution is formed between them, making the corrosion form a general corrosion type.

Cu in the core material also contributes to improving strength.

The anti-corrosion effect and strength-improving effect of Cu shown above are not exhibited when Cuff in the core material is less than 0.25%;
．． If it exceeds 8%, the corrosion resistance of the core material itself deteriorates and the melting point of the core material decreases, causing local melting during brazing.

Si: Si improves the strength of the core material. In particular, by coexisting with Mg diffused from the sacrificial anode material into the brazing filler metal, the strength becomes higher due to age hardening of the brazing filler metal. 0.2%
If it is less than 1.0%, the effect will not be sufficient, and if it exceeds 1.0%, the corrosion resistance will decrease and the melting point of the core material will drop, causing local melting during brazing.

Mg: Mg has the effect of improving the strength of the core material, but brazing deteriorates the properties. Therefore, the Mg content in the core material is 0.5
% or less.

If it exceeds 0.5%, it will react with the fluoride flux, impairing brazing performance, or producing Mg fluoride, which will deteriorate the appearance of the solder joint.

Ti: Ti further improves the corrosion resistance of the core material.

In other words, Ti is divided into high- and low-concentration regions, which are distributed alternately in the plate thickness direction to form a layered structure, and regions with low Ti concentration corrode preferentially compared to regions with high Ti concentration, resulting in a layered corrosion pattern. Make it. As a result, the progress of corrosion in the thickness direction is inhibited and the pitting corrosion resistance of the material is improved. 0.3
If it exceeds 5%, coarse compounds will be produced during casting, making it impossible to obtain a sound plate.

Other elements: Fe, Zn, Cr, Zr, etc. may be included within a range that does not impair the effects of the present invention. However, since Fe impairs corrosion resistance if contained in a large amount, it is preferably 0.7% or less. Zn makes the potential of the core material base and reduces the potential difference between the sacrificial anode material and the brazing material, so it is preferably 0.2% or less.

(2) Sacrificial anode material Mg: A part of Mg in the sacrificial anode material mainly diffuses into the core material in the brazing material and improves the strength of the core material together with Si and Cu in the core material. Further, Mg remaining in the sacrificial anode material improves the strength of the sacrificial anode material together with Si. These actions contribute to improving the strength of the cladding material as a whole. 1
If it is less than 2%, the effect will not be sufficient, and if it exceeds 2.5%, local melting will occur during brazing, which is not preferable.

= 11- Note that the Mg in the sacrificial anode material diffuses into the core material, but it has a concentration distribution as shown in Figure 1, and a large amount of Mg diffuses toward the brazing material, preventing brazing. It does not inhibit sexuality. It goes without saying that diffusion also occurs during cladding production, and that there is a slight concentration distribution at the boundary between the core material and the sacrificial anode material.

Si: Si improves the strength of the sacrificial anode material and contributes to improving the strength of the entire cladding material. In particular, M remaining in the sacrificial anode material
Along with g, age hardening occurs and contributes to improving strength.

If it is less than 0.2%, the effect will not be sufficient, and if it exceeds 0.8%, local melting will occur during brazing.

Zn: Zn lowers the potential of the skin material and provides a sacrificial anode effect.

As a result, the form of corrosion becomes a general corrosion type, and pitting corrosion and crevice corrosion are suppressed. If it is less than 0.5%, the effect is not sufficient;
If it exceeds 2.0%, self-corrosion resistance will deteriorate and the corrosion rate will increase.

= 12- In, Sn, Ga: In and Sns Ga both make the potential of the skin material less noble,
Suppresses pitting corrosion and crevice corrosion. If the upper limit is exceeded, self-corrosion resistance and rolling workability will deteriorate.

Unlike Zn and Mg, these elements do not evaporate in large quantities during brazing or react with flux, so they remain in the skin material and reliably lower the potential of the skin material. However, on the other hand, unlike Zn, it has a small effect of diffusing into the skin material to form a gentle concentration gradient and forming a gentle potential distribution, and therefore it is slightly less effective in making the corrosion form a general corrosion type. Therefore, In for leather materials.

one or more of Sn and Ga coexist with Zn,
By combining this with a core material containing 0.25 to 0.8% Cu, the effect of making the potential of In5Sn and Ga less noble, the effect of forming a gentle potential distribution of Zn and Cu in the core material, and Combined with the effect of increasing the potential of Cu in the core material, pitting corrosion and crevice corrosion can be further prevented.

(3) Brazing material The brazing material is a commonly used Al-8t alloy. Usually 6
An Al alloy containing ~13% SL is used.

[Example code] The present invention will be specifically described below with reference to Examples.

Prepare ingots of the core material alloy shown in Table 1 below, the sacrificial anode material alloy shown in Table 2, and the brazing material alloy 4045,
Homogenization treatment was performed on the alloy for the core material and the alloy for the sacrificial anode material. Then, the sacrificial anode material alloy and the brazing metal alloy were hot-rolled to a predetermined thickness, and these were combined with the ingot of the core material alloy to obtain a cladding material by hot rolling. Thereafter, a plate (HI3 material) having a thickness of 0.25 mm was produced by cold rolling, intermediate annealing, and cold rolling.

The cladding material had a core material of 0.2 On+m, and a sacrificial anode material and a brazing material of 0.025 mm each.

The alloy composition and combinations of each monthly fee are shown in Table 3.

On the brazing material side of the obtained clad plate material, Al-], 2%M
A corrugated fin having a thickness of 0.10 mm made of n-1.5% Zn alloy was mounted, and brazing was performed using fluoride flux in nitrogen gas. Brazing temperature (material temperature) is 60
It was 0°C. The state of bonding between the brazing material and the fins and the occurrence of flocculent products were visually observed, and the state of melting of the core material and sacrificial anode material was investigated by cross-sectional metallographic structure.

Next, the plate material with a thickness of 0.25 mm was heated as it was (without contact with the fins) under the same conditions as for fluoride flux brazing, and then subjected to a tensile test and a corrosion test. The corrosion test method was CASS test for 30 days on the outer surface side (brazing material side), and CI-1100 pl on the inner surface side (sacrificial anode material side).

S, 04”100100pp CO3-10010
0pp u” immersed in an aqueous solution containing 10ppm,
A cycle of heating to 80° C. for 3 hours, then cooling to room temperature, and then leaving for 16 hours was repeated for 3 months.

The above results are summarized in Table 3. Invention example No. 091~
In the case of 20, the brazing property is good and the tensile strength is 17 kgf.
'/mm2 or more, and the maximum corrosion depth is 0.1 on the inner surface.
It is small, 0 mm or less, and 0.11 mm or less on the outer surface side.

Moreover, the maximum corrosion depth on the inner surface side is No. 1 to 9, N.

17 and 0.08 to 0. LOmm, whereas In5
No. 1.0 to 1 [i, No. 1 containing SnsGa
8 to 20 are as small as 0.05 to 0.0 (imm).

In the case of Comparative Example No. 21, the tensile strength was as low as 15 kgf/mn+2 because the sacrificial anode material contained less Mg.

In Comparative Example No. 22, local melting occurred during brazing due to the large amount of Mg, so other tests were discontinued.

Comparative Example No. 28 has a low tensile strength of 15 kgr/mm2 because the sacrificial anode material contains less Si.

In Comparative Example No. 24, local melting occurred during brazing due to the large amount of Si, so other tests were discontinued.

In the case of Comparative Example No. 25, the corrosion depth on the inner surface side was slightly large at 0.13 mm because the sacrificial anode material contained less Zn.

On the other hand, positive and 26 have a large amount of Zn, so the corrosion depth on the inner surface is 0.
．． It is large at 18mm.

No. 27, 28 and 29 are In, Sn or Ga
Because of the large amount of corrosion, the corrosion depth on the inner surface is 0.15 to 0.16
It is large as n+m.

No. 80 has a low tensile strength of 15 kgf'/mm2 due to low Mn in the core material, and No. 31 has a low Mn content in the core material.
Because of the large number of errors, it was not possible to obtain a healthy board score, and the test was discontinued.

No. 32 has a tensile strength of 1 because the core material contains less Cu.
The corrosion depth on the outer surface is as low as 5 kgf/mm' and 0.19.
It is as large as mm.

As for No. 33, melting occurred during brazing due to the large amount of Cu in the core material, so other tests were discontinued.

No. 34 has a tensile strength of 1 due to less Si in the core material.
It is as low as 5kgf/m+n2.

For No. 35, melting occurred during soldering due to the large amount of Si in the core material, so other tests were discontinued.

No. 38 has a low tensile strength of 15 kgf/mm2 because the core material does not contain Mg.

In No. 37, poor brazing occurred due to a large amount of Mg in the core material.

In No. 38, since the core material does not contain Ti, the corrosion depth on the outer surface side is slightly large at 0.14 mm.

No. J9 had a high Ti content in the core material, so a healthy board could not be obtained, and the test was discontinued.

No. 40 has a core material of 3003, so its tensile strength is low at 12 kgf/mm2, and the corrosion depth on the outside surface is 0.2.
It is large at 1mm.

Table 1 * Table 2 for 3003 alloy [Effects of the invention] As explained above, the clad material of the present invention has high strength and corrosion resistance as a material used in conjunction with fluoride flux brazing, and
This is an Al heat exchanger cladding material with excellent brazing properties. As a result, the tube material and header plate material can be made thinner, and the weight of the radiator and heater can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the concentration distribution of Mg, which acts as a wax, in the material of the present invention. Patent applicant: Sumitomo Light Metal Industries, Ltd.

Claims (2)

[Claims] (1) The core material is Mn: 0.3 to 2.0% (weight%, same below), Cu: 0.25 to 0.8%, Si: 0.2 to 1
．． 0%, Mg: 0.5% or less, Ti: 0.35% or less, and the remainder is Al and inevitable impurities, and the sacrificial anode material composited on one side of the core material is Mg: 1.2-2.5%, Si: 0.2-0.8%,
It is composed of an aluminum alloy containing Zn: 0.5 to 2.0%, the balance being Al and unavoidable impurities, and the skin material composited on the other side of the core material is an Al-Si alloy wax. A high-strength, high-corrosion-resistant aluminum alloy cladding material for heat exchangers. (2) Core material: Mn: 0.3-2.0%, Cu: 0.2
5-0.8%, Si: 0.2-1.0%, Mg: 0.5
% or less, Ti: 0.35% or less, the balance being Al and unavoidable impurities, and the sacrificial anode material composited on one side of the core material has Mg: 1.2 to 2.
5%, Si: 0.2-0.8%, Zn: 0.5-2.0
%, furthermore, In: 0.2% or less, Sn: 0.2%
% or less and Ga: 0.2% or less, the skin material is composed of an aluminum alloy consisting of Al and inevitable impurities, and is composited on the other side of the core material. A high-strength, high-corrosion-resistant aluminum alloy cladding material for a heat exchanger, characterized in that the material is composed of a brazing filler metal of an Al-Si alloy.