JPH07116545B2 - High strength and corrosion resistant aluminum alloy clad material for heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a structural member for manufacturing an Al heat exchanger such as a radiator or a heater core by brazing using a fluoride flux in an inert gas atmosphere. Suitable for use as a tube material or header plate material,
The present invention relates to an Al alloy clad material having good brazing property and having high strength and high corrosion resistance after brazing, and is particularly suitable for a tube material used with a thin wall.

[Prior Art] Tube materials such as automobile radiators and heater cores and header plate materials are made of Al-Mn alloy such as 3003 as the core material, and Al-Si alloy brazing material on one side and other one side. Al-
A three-layer clad material in which a sacrificial anode material such as a Zn-based alloy or an Al-Zn-Mg-based alloy is clad is used. The Al-Si type brazing material is used for joining the tube to the fin and joining the tube to the header plate. Brazing is often performed using a fluoride flux in an inert gas atmosphere. The other side clad with the sacrificial anode material becomes an inner side (water side) during use, and exhibits a sacrificial anode function to prevent pitting and crevice corrosion of the core material.

In recent years, there has been a strong demand for weight reduction of radiators and heater cores, and it has become necessary to reduce the thickness of tube materials and header plate materials. For that purpose, it is necessary to increase the strength of the material, especially the strength after brazing, and in order to increase the strength, Mg is often added to the core material. However, since Mg diffuses to the surface during brazing and reacts with the fluoride flux, a cotton-like product (fluoride of Mg) is produced and adheres, or a bonding failure occurs. Thus
The amount of Mg added to the core material is 0.5% at the maximum, 0.2 for practical use
It is limited to 0.3%, which hinders high strength.

The strength of tubular and header plate materials may also be improved by adding Mg to the sacrificial anode material.
There have been some proposals for the clad material in which Mg is added to the sacrificial anode material.

That is, a method of including Mg and Zn in the sacrificial anode material such as the header plate material for radiators and the tube material (Japanese Patent Publication No. 63-28704).
However, the method of adding Zn and Mg (JP-A-61-89498) and the method of simultaneously adding Sn and Mg (JP-A-56-16646, JP-A-63-89641) are relatively high. Method of adding Mg and Zn up to the concentration (Japanese Patent Publication Sho 62
−45301), has been proposed.

However, the addition of Mg above and 1.1% or 1.5
% Or less, it is added to prevent pitting and crevice corrosion, and strength cannot be improved.

The above Mg addition suppresses the grain boundary diffusion of Sn, the purpose of preventing cracking during hot rolling, the addition of the above Mg is intended to improve the pitting corrosion resistance, both Mg In the case of a high concentration, there is a possibility that it diffuses into the core material and some strength improvement effect is obtained. However, when a thin tube material (cladding material) is made, even if the strength of the core material can be increased by the Mg diffused from the sacrificial anode material, the strength of the sacrificial anode material is Mg.
Addition alone is insufficient, and the strength of the entire clad material cannot be increased. That is, when the thickness is reduced, the contribution to the strength of not only the core material but also the sacrificial anode material is large, and it is necessary to increase the strength of the sacrificial anode material.

Conventionally, Al-Zn alloy or Al-Zn-Mg alloy is used as the sacrificial anode material.
A concentration gradient extending to a depth of 0.2 mm is formed, and the diffusion layer is used as a sacrificial anode layer to protect the core material from corrosion.

This method is used when the clad material is relatively thick, i.e.
It is effective when 0.3 mm or more, but when the cladding material is thinned, for example, 0.25 mm or less, the diffusion depth of Zn, that is,
If the thickness of the sacrificial anode layer is 0.1 to 0.2 mm, it is too large, and most of the clad material plate thickness is a corrosion allowance. As a result, during use, the sacrificial anode layer is consumed and the strength of the material is significantly reduced, which is a problem.

For the above reasons, there has been a limit to thinning the cladding material for fluoride flux brazing.

[Problems to be Solved by the Invention] The present invention provides high strength after brazing without impairing the brazing property, that is, while keeping the amount of Mg added to the core material to a maximum of 0.5%, and at the same time sacrificial. An object of the present invention is to provide a clad material in which the thickness of the anode layer does not become too large.

[Means for Solving the Problems] The inventors of the present invention investigated a method for obtaining high strength after brazing while keeping the amount of Mg added in the core material at a maximum of 0.5%, and found that the high sacrificial anode material had a high strength. When a concentration of Mg and Si is added, part 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 and Si.
The present invention was completed by finding out that it was strengthened by.

Furthermore, as a result of investigating the additive elements of the sacrificial anode material, when an element such as Zn that has a large diffusion rate into the core material during brazing is added, a diffusion layer (sacrificial anode layer) is formed on the surface of the core material. Is thicker, while Sn, In, and Ga are 1
It was found that the sacrificial anode layer does not increase in thickness because the speed of diffusion into the core material is small when a small amount of more than one species is added, and that the thickness of the sacrificial anode layer can be arbitrarily adjusted by changing the cladding rate.

The present invention has been completed based on these findings.

That is, the structure of the present invention, the core material, Mn: 0.3 ~ 2.0%, Cu: 0.25 ~ 0.8%, Si: 0.2 ~ 1.0%
%, Mg: 0.5% or less, Ti: more than 0.1 and 0.35% or less,
The balance of the sacrificial anode material composed of an aluminum alloy consisting of Al and unavoidable impurities and composite on one surface of the core material is Mg: 1.2-
2.5%, Si: 0.2-0.8%, In: 0.2% or less,
A skin that contains one or more of Sn: 0.2% or less and Ga: 0.2% or less, is composed of an aluminum alloy consisting of the balance Al and inevitable impurities, and is compounded on the other side of the core material. A high-strength and high-corrosion-resistant aluminum alloy clad material for a heat exchanger, characterized in that the material is composed of a brazing material of an Al-Si alloy.

Hereinafter, the amount and action of each component of the above material will be described.

(1) Core material Mn: Improves strength. Further, the potential of the core material is made noble and the potential difference with the sacrificial anode material is increased to improve the corrosion resistance. If it is less than 0.3%, the effect is not sufficient, and if it exceeds 2.0%, a coarse compound is generated during casting, and a sound plate material cannot be obtained.

Cu: The potential of the core material is made noble, the potential difference between the sacrificial anode material and the brazing material and the core material is increased, and the anticorrosion effect by the sacrificial anode effect of the sacrificial anode material and the brazing material is increased. Furthermore, in the core material
Cu diffuses into the sacrificial anode material and the brazing material during brazing to form a gentle concentration gradient, and the core side has a noble potential, and the sacrificial anode material and the brazing material each have a base potential on the surface side, with a gentle potential gradient between them. A uniform potential distribution is formed to make the corrosion form a general corrosion type.

Cu in the core material also contributes to the improvement of strength.

The anticorrosion effect and strength improving effect of Cu shown above are
If the Cu content is less than 0.25%, it will not be exhibited. On the other hand, if it exceeds 0.8%, the corrosion resistance of the core material itself will deteriorate and the melting point of the core material will decrease, causing localized melting during brazing.

Si: Improves the strength of the core material. In particular, Mg coexists with Mg that diffuses from the sacrificial anode material during brazing, and the strength becomes higher due to age hardening after brazing. If it is less than 0.2%, the effect is not sufficient, and if it exceeds 1.0%, the corrosion resistance is lowered and the melting point of the core material is lowered to cause local melting during brazing.

Mg: Improves the strength of the core material. The effect of improving strength is more effectively exhibited by age hardening after brazing when coexisting with Si and / or Cu. However, if it exceeds 0.5%, it reacts with a fluoride flux to hinder the brazing property, or Mg fluoride is produced to impair the appearance.

Ti: Ti exceeding 0.1% further improves the corrosion resistance of the core material. That is, Ti is divided into a high concentration region and a low concentration region,
They are alternately distributed in the plate thickness direction to form a layer, and the region where the Ti concentration is low is preferentially corroded as compared with the region where the Ti concentration is high, so that the corrosion form is layered. As a result, the progress of corrosion in the plate thickness direction is prevented and the pitting corrosion resistance of the material is improved. 0.35%
If it exceeds the range, a coarse compound is generated during casting, and a sound plate material cannot be obtained.

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

(2) Sacrificial anode material Mg: A part of Mg in the sacrificial anode material diffuses into the core material mainly during brazing, 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. And these effects contribute to the improvement of the strength of the entire clad material. If it is less than 1.2%, the effect is not sufficient, and if it exceeds 2.5%, local melting occurs during brazing.

Although Mg in the sacrificial anode material diffuses into the core material during brazing, it has a concentration distribution as shown in Fig. 1 and diffuses in large amounts to the brazing material side, impeding brazing properties. There is nothing to do. Needless to say, diffusion also occurs during the production of the clad, and a slight concentration distribution is present at the boundary between the core material and the sacrificial anode material.

Si: Improves the strength of the sacrificial anode material and contributes to the strength of the entire clad material. In particular, age hardening occurs together with Mg remaining in the sacrificial anode material, which contributes to the improvement of strength. If it is less than 0.2%, the effect is not sufficient, and if it exceeds 0.8%, local melting occurs during brazing.

Sn, In, Ga: The addition of a small amount of Sn makes the potential of the sacrificial anode material base, and ensures the sacrificial anode effect on the core material. As a result, pitting corrosion and crevice corrosion of the core material are prevented. If the content exceeds the upper limit, the self-corrosion resistance and the rolling workability are deteriorated, the diffusion at the time of brazing is increased, and the sacrificial anode layer becomes thick. When a small amount of these elements is added, the diffusion is not fast unlike the case of Zn, and therefore the thickness of the diffusion layer after brazing does not become much larger than the thickness of the sacrificial anode material before brazing. Therefore, the thickness of the corrosion allowance can be controlled arbitrarily and small.

(3) Brazing material The brazing material is a commonly used Al-Si alloy. Usually 6 to 13
An alloy containing% Si is used.

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

Ingots of core alloy shown in Table 1 below, sacrificial anode alloy shown in Table 2 and brazing alloy 4343 are prepared and homogenized with respect to the core alloy and sacrificial anode alloy. went. Then, the alloy for the sacrificial anode material and the alloy for the brazing material were hot-rolled to a predetermined thickness, and these and the ingot of the alloy for the core material were hot-rolled to obtain a clad material. Then, a plate (H14 material) having a thickness of 0.23 mm was prepared by cold rolling, intermediate annealing and cold rolling. The composition of the clad is 0.0
The sacrificial anode material was set to 0.025 to 0.050 mm with a constant 25 mm.

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

On the brazing material side of the obtained clad plate material, Al-1.2% Mn-1.5
A 0.10 mm-thick corrugated fin made of a% Zn alloy was put on and brazed in a nitrogen gas using a fluoride flux. The brazing temperature (material temperature) was 600 ° C. After brazing, the joining state between the plate material and the fin was visually observed, and the melting state of the core material and the sacrificial anode material was examined by the cross-section metallographic structure.

Next, the 0.23 mm-thick plate material was heated as it was (without being brought into contact with the fins) under the same conditions as the fluoride flux brazing, and then a tensile test and a corrosion test were conducted. The corrosion test method is CASS test for the outer surface (brazing material side) for 30 days, and Cl-100ppm, SO for the inner surface (sacrificial anode material side).
_{^{4 2- 100ppm, HCO 3 - 100ppm}} , immersed in an aqueous solution containing Cu ²⁺ 10 ppm, heated to 80 ° C. during -8 hr, then repeat cycle that 16hr left to cool to room temperature, repeated three months It was

The above results are summarized in Table 3. In Invention Examples Nos. 1 to 13, the brazing property is good, the tensile strength is as high as 17 kgf / mm ² or more, and the maximum corrosion depth is small.

In the case of Comparative Example No. 14, the tensile strength is low because the sacrificial anode material has a small amount of Mg.

Comparative Example No. 15 has a large amount of Mg, so that local melting occurs during brazing.

Comparative Example No. 16 has low tensile strength because the sacrificial anode material has a small amount of Si.

In Comparative Example No. 17, since the amount of Si is large, local melting occurs during brazing.

In Nos. 18, 19, and 20, the sacrificial anode material has a large amount of Sn, In, or Ga, so that the corrosion depth on the inner surface side is large.

In No. 21, since the sacrificial anode material does not contain Sn, In, or Ga, the corrosion depth on the inner surface side is large.

Since No. 22 uses a sacrificial anode material containing Zn, the inner surface has a large corrosion depth.

No. 23 has a low tensile strength due to a small amount of Mn in the core material.
In No. 24, a healthy plate material is not obtained because the core material has a large amount of Mn.

No. 25 has a low tensile strength due to a small amount of Cu in the core material, and has a large corrosion depth on the outer surface side.

No. 26 has a large amount of Cu in the core material, so that melting occurs during brazing.

No. 27 has a low tensile strength because the core material is low in Si.

No. 28 has a large amount of Si in the core material, so that melting occurs during brazing.

No. 29 has a low tensile strength because the core material does not contain Mg.

No. 30 has a brazing defect due to a large amount of Mg in the core material.

No. 31 has a slightly larger corrosion depth on the outer surface side because the core material does not contain Ti.

In No. 32, a healthy plate material is not obtained because the core material has a large amount of Ti.

In No. 33, the core material is 3003, so the tensile strength is low and the corrosion depth on the outer surface side is large.

[Effects of the Invention] As described above, the clad material of the present invention has high strength and corrosion resistance as a material for fluoride flux brazing, and
It is an Al heat exchanger clad material with excellent brazing properties. As a result, the tube material and the header plate material can be made thin, and the weight of the radiator and the heater can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing the Mg concentration distribution after brazing of the material of the present invention.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location F28F 21/08 (72) Inventor Kenji Kato 3-12-12, Chiennen, Minato-ku, Nagoya, Aichi Light Metal Industry Co., Ltd. Technical Research Institute (72) Inventor Naoki Tokizo 3-1-1, 1000, Minen-ku, Nagoya-shi, Aichi Pref. Sumitomo Light Metal Industry Co., Ltd. Technical Research Center (3-12) (56) References JP-A-63-303027 (JP, A) JP-A-54-110909 (JP, A)

Claims (1)

[Claims] 1. The core material is Mn: 0.3 to 2.0% (weight%, the same applies hereinafter), Cu: 0.25 to 0.8%, Si: 0.2 to 1.0%, Mg: 0.5% or less, and Ti: 0.1 to 0.35%. The sacrificial anode material containing the following, composed of an aluminum alloy consisting of balance Al and unavoidable impurities, and having a composite sacrificial anode material on one surface of the core material: Mg: 1.2 to 2.5%, Si: 0.2
To 0.8%, and further contains one or more of In: 0.2% or less, Sn: 0.2% or less, and Ga: 0.2% or less, and the balance Al.
And an aluminum alloy consisting of inevitable impurities,
A high-strength and high-corrosion-resistant aluminum alloy clad material for a heat exchanger, characterized in that a skin material compounded on the other surface of the core material is composed of a brazing material of an Al-Si alloy.