JPH04198448A - 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 having a composition consisting of 1.2-2.5% Mg, 0.2-0.8% Si, and the balance Al with inevitable impurities. 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.
Related to Al alloy cladding materials that have good brazing properties and have high strength and high corrosion resistance for use as brazing materials, suitable for use as structural members such as tube materials and header plate materials when manufacturing heat exchangers. and
Particularly suitable for thin-walled tube materials.

[Prior art] Al-Mn such as 3003 is used for tubes and header plate materials such as automobile radiators and heater cores.
The core material is Al-Si alloy, and the other side is Al-Si alloy or A1-Z alloy.
A three-layer rad shrine clad with a sacrificial anode material of n-Mg alloy is used.

The Al-8i brazing material is used for joining tubes and fins, and 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. To achieve this, it is necessary to improve the strength of the material, especially the strength of the solder, and it is becoming increasingly common to add Mg to the core material to increase the strength. However, Mg diffuses to the surface of the fistula 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 1.5% at maximum, but in practice it is limited to 0.2 to 0.3%, which is a hindrance to increasing the strength.

The strength of the tube shrine and header play 1 shrine may also be improved by adding Mg to the sacrificial anode material. There have been several proposals regarding cladding materials in which Mg is added to sacrificial anode materials.

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 adding Sn and Mg simultaneously (Japanese Unexamined Patent Publication No. 186-1986)
46, Japanese Patent Publication No. 63-89641), ■ A method of adding Mg and Zn to a relatively high concentration (Japanese Patent Publication No. 62-89641).
5301) has been proposed.

However, the addition of Mg in (1) and (2) above is as low as 1.1% or 1.5% or less, and is added to prevent pitting corrosion and crevice corrosion, so that 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, and the strength of the entire cladding material is insufficient. The only thing you can do is increase the strength. 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.

[Problem 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 Si are added to the sacrificial anode material, part of the Mg in the sacrificial anode material will diffuse into the core material during brazing, strengthening the core material, and the sacrificial anode material itself will also contain 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 the strengthening of the core material, Mg
It is strengthened by solid solution strengthening with Si and age hardening with precipitation of Mg2Si.

That is, the structure of the present invention is such that the core material has Mn: 0.3 to 2.0% and Cu: 0.
．． 25-0.8%, Si: 0.2-1.0%, M
g: 0.5% or less, Ti: 0.35% or less, and the remainder is Al and unavoidable impurities.
g: 1.2-2.5%, Si: 0.2-0.8%
The core material is made of an aluminum alloy containing aluminum and the remainder is Al and unavoidable impurities, and the skin material composited on the other side of the core material is made of a brazing material of an Al-8L alloy. This is a high-strength, high-corrosion-resistant aluminum alloy cladding material for heat exchangers with a rating of -6.

[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 affects the potential of the core material, increases the potential difference between the sacrificial anode material and brazing material, and the core material, and increases the anticorrosion effect of the sacrificial anode material and 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 having a higher potential and the sacrificial anode material and the brazing material having a lower potential on the surface side. 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 corrosion-preventing effect and strength-improving effect of Cu shown above are not exhibited when the amount of Cu 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, it coexists with Mg diffused from the sacrificial anode material into the brazing material, and the strength increases due to age hardening after brazing. 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.

The strength improving effect is better exhibited by age hardening after brazing when it coexists with Si and/or Cu. However, if the amount exceeds 0.5%, it will react with the fluoride flux, impairing brazing properties, and producing Mg fluoride, which will impair the appearance.

T1: 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 must be kept at 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 wax, so it needs to be 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 81 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.

Furthermore, the potential of the sacrificial anode material is made base to ensure the sacrificial anode effect. ■ If it is less than 2%, the effect is not sufficient, and 2.5
%, local melting occurs during brazing.

Note that 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, inhibiting brazing properties. There's nothing to do. 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. 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 11%, local melting will occur during brazing.

(3) Brazing material The brazing material is a commonly used Al-8t alloy. Usually 6
An Al alloy containing ~13% Si 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 4047,
Homogenization treatment was performed on the core material alloy and the sacrificial anode alloy. Then, the sacrificial anode material alloy and the brazing material 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. After that, the thickness is 0 by cold rolling, intermediate annealing, and cold rolling.
．． A 25 mm plate (HI3 material) was produced.

The composition of the cladding material is that the brazing material is constant at 0.025mm.
The sacrificial anode material was bound to 0.030 to 0.050 mm+.

The alloy composition of each material and its combinations are shown in Table 3.

Al-1.2%M was applied to the brazing material side of the obtained clad plate material.
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 (feed temperature) is 60
It was 0°C. The state of bonding between the brazing material and the fin was visually observed, and the state of melting of the core material and sacrificial anode material was examined by cross-sectional metallographic structure.

Next, the plate material with a thickness of 0.25+ nm 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 is CASS test for 30 days on the outside side (brazing metal side), and CASS test on the inside side (sacrificial anode side).
I-1100pp.

-]2-5 O422-1O0pp, HCO3LOOppmS
It was immersed in an aqueous solution containing 10 ppm of Cu, heated to 80°C for 8 hours, and then cooled to room temperature for 16 hours.
The cycle of leaving it for 3 months was repeated for 3 months.

The above results are summarized in Table 3. Invention example No. 1
~12, the brazing properties are good and the tensile strength is 17kg.
r/mm 2 or higher, and the maximum corrosion depth is also small.

In the case of Comparative Example No. L3, the tensile strength was low because the sacrificial anode material contained less Mg.

In Comparative Examples NO and L4, local melting occurred during brazing due to the large amount of Mg.

Comparative Example No. 15 has low tensile strength because the sacrificial anode material contains less Si.

In Comparative Example No. IB, local melting occurred during brazing due to the large amount of Si.

No. 17 had a low tensile strength because the core material had a low Mn content, and No. 18 had a high Mn content in the core material, so a sound board material was not obtained.

No. 19 has a low tensile strength due to a small amount of Cu in the core material, and a large corrosion depth on the outer surface side.

Since N0120 has a large amount of Cu in the core material, melting occurs during brazing.

No. 21 had low tensile strength because the core material contained less Si.

No. 22 melted during brazing because the core material contained a large amount of Si.

No. 23 has a low tensile strength because the core material does not contain Mg.

In No. 24, poor brazing occurred due to a large amount of Mg in the core material.

No. 25 has a large corrosion depth on the outer surface side because the core material does not contain Ti.

Since Nα2B has a large amount of Ti in the core material, a healthy plate material cannot be obtained.

In No. 27, since the core material is 3003, the tensile strength is low and the corrosion depth on the outer surface side is large.

= 14 = Table 1 * 3003 Alloy Table 2 [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 combination with fluoride flux brazing, and
This is an Al heat exchanger cladding 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 (1)

[Claims] The core material is Mn: 0.3 to 2.0% (weight%, the same below)
, 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, and the sacrificial anode material composited on one side of the core material contains Mg
: 1.2 to 2.5%, Si: 0.2 to 0.8%, and the remainder is Al and unavoidable 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 skin material is composed of a brazing filler metal of an Al-Si alloy.