JPH0670265B2 - A brazing fin material for aluminum heat exchangers having excellent thermal conductivity after brazing and sacrificial anode effect - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a condenser for an air conditioner, an evaporator,
Alternatively, it relates to a brazing fin material for an Al heat exchanger in which fins and a working fluid passage forming material such as a radiator are joined by brazing. Particularly, the fin material has a high thermal conductivity after brazing and is excellent in sacrificial anode effect. Regarding

[Prior Art] Al-Cu alloys, Al-Mn alloys, Al-Mn-Cu alloys are used for heat exchangers such as condensers and evaporators of car air conditioners, radiators of automobiles, heaters, intercoolers and oil coolers. Working fluid passage material such as alloy,
The aluminum alloy fin material is assembled by brazing. The brazing material may be arranged on the passage forming material side or the fin material side. In the latter case, the fin material is made of aluminum alloy as the core material and Al-Si
A composite material in which a braze alloy alloy is clad is used. Further, the fin material is required to have a sacrificial anode effect in order to prevent corrosion of the working fluid passage constituent material, and also has an excellent high temperature buckling resistance so as not to be deformed by high temperature heating during brazing or the brazing material does not corrode. Sex is required. The addition of Mn is effective in preventing deformation during brazing and erosion of the braze.
Al-Mn alloys such as 3003 alloy and 3203 alloy are used.
Then, in order to impart a sacrificial anode effect, a method of adding Zn, Sn, In, or the like to an Al-Mn alloy to make it electrochemically base (see, for example, Japanese Patent Publication No. 56-12395), To further improve high temperature buckling resistance (high temperature sag resistance),
A method of adding Cr, Ti, Zr or the like (see, for example, JP-A-54-6135).
No. 4) is proposed.

Further, the present applicants proposed a heat exchanger fin material (Japanese Patent Application No. 1-218648) excellent in strength and thermal conductivity by previously increasing the content of Fe without adding Mn.

[Problems to be Solved by the Invention] By the way, in recent years, there have been strong demands for weight reduction and cost reduction of heat exchangers. It is necessary to reduce the material thickness). However, when the fin material is made thin, the heat transfer cross-sectional area becomes small, which causes a problem of impairing the heat exchange performance.

In order to solve this problem, it is effective to increase the thermal conductivity of the fin material after brazing, but in the case of Al-Mn based alloy, Mn is a solid solution at high temperature during brazing, so the thermal conductivity The degree of decrease is remarkable. In order to increase the thermal conductivity, pure aluminum (1050, 1070, etc.) can be coated with Zn, Sn, In or Cr,
Attempts have also been made to use fin materials to which Ti, Zr, etc. have been added, but in this case, the high temperature buckling resistance is poor, and the fins collapse due to their high thermal conductivity but low strength after brazing. Is likely to occur and is not a fundamental solution to the problem.

More recently, a zinc-coated tube has been often used as a material for forming a passage, and in this case, a zinc diffusion layer is formed during brazing to protect the tube from corrosion. And such a tube and conventional fin material, namely Al-
When using a fin material in which Zn, Sn, In, etc. are added to Mn by brazing, since the zinc diffusion layer has a lower potential or base than the fin, the zinc diffusion layer corrodes earlier than the fin, There is a problem that the fins come off from the tube.

The previously proposed "heat exchanger fin material having excellent strength and thermal conductivity by increasing the content of Fe without containing Mn" has no Al-Si brazing material on both sides of the core material. , Not suitable for joining with bare tube material (without brazing material).

The present invention is intended to solve these problems fundamentally.

[Means for Solving the Problems] The present inventors have studied various aluminum alloys, and have a significantly higher thermal conductivity after brazing than fin materials having a conventional Al-Mn alloy as a core material. And the strength is high,
The present invention has been completed by finding a brazing fin material excellent in sacrificial anode effect, particularly sacrificial anode effect for zinc-coated tubes and high temperature buckling resistance, that is, the present invention, Fe: more than 1.0% and 1.8% or less, Zn: 0.3 ~
3.0%, Cu: 0.3% or less, further Zr: 0.05-0.25%,
Cr: 0.05 to 0.25% of one or two, Mn as an impurity is 0.3% or less, the balance is an aluminum alloy consisting of Al and other unavoidable impurities as a core material, and Al-Si-based brazing alloys on both sides A brazing fin material for an Al heat exchanger, which is excellent in thermal conductivity after brazing and a sacrificial anode effect, characterized by clad material.

The reasons for limiting each component in the present invention are as follows.

(1) Core material Fe: Fe improves the strength of the alloy, that is, the strength of the fin material before brazing and the strength after brazing. Since the alloy of the present invention does not contain Mn, more than 1.0% of Fe is necessary for improving the strength. On the other hand, if it exceeds 1.8%, coarse crystallized substances are generated during casting, and it becomes difficult to manufacture a plate material.

Unlike Mn, Fe does not form a solid solution during brazing to lower the thermal conductivity or make the potential noble. Therefore, the fin material has excellent thermal conductivity and sacrificial anode effect, especially for the zinc-coated tube. Suitable as an additive element to the core material.

Zn: Zn makes the electric potential of the fin material base and gives a sacrificial anode effect. In particular, when Zn is added to the Al-Fe alloy, the potential becomes effectively base, and the sacrificial anode effect on the zinc-coated tube becomes particularly good. If it is less than the lower limit, the effect is not sufficient, and if it exceeds the upper limit, the self-corrosion resistance deteriorates.

Cu: Cu improves the strength after brazing. If the upper limit is exceeded, the potential of the fin material becomes noble and the sacrificial anode effect is impaired.

Zr, Cr: Zr and Cr improve high temperature buckling resistance. If it is less than the lower limit, the effect is not sufficient, and if it exceeds the upper limit, the thermal conductivity after brazing decreases.

Mn: It is preferable that the content of Mn as an impurity is small as the content thereof increases, as described above, because the thermal conductivity decreases and the potential becomes noble. However, if its content is 0.3% or less, it is acceptable.

Other elements may include Si, Mg, Ti, etc. within a range that does not impair the effects of the alloy of the present invention. However, in both cases, the thermal conductivity decreases as the content increases. Therefore, Si is
It is desirable that the content is 0.6% or less, the content of Mg is 0.2% or less, and the content of Ti is 0.05% or less. Since Mg reacts with the flux when brazing with fluoride flux, it is even lower, that is, 0.
It is desirable to keep it below 1%. Ti may be added as an alloying element for crystal refining during casting, and Al-Ti
Although it may be added as a -B refining agent, it is desirable to suppress it within the above range.

(2) Brazing material As the brazing material, an Al-Si alloy is used. Usually 6 to 13%
An alloy containing Si is used. A part of Si in the brazing material diffuses into the core material during brazing (solid diffusion) and contributes to the improvement of strength. Further, Zn may be added to the brazing material in order to enhance the sacrificial anode effect of the entire fin material.

[Example] Example 1 Alloys for core materials A to O shown in Table 1 and alloy 4343 for brazing material
(Al-7.5% Si) was melted and cast. The alloy ingot for core material is subjected to homogenization treatment, and this is combined with a brazing material that has been hot rolled in advance, hot rolling, cold rolling, intermediate annealing and finish cold rolling are performed, and mm (brazing material clad ratio: 10% on both sides) brazing fin materials No. 1 to 15 were produced. Next, as in brazing, 600 ℃ x 3 in nitrogen gas
After heating for 1 minute, a tensile test and an electric conductivity measurement were performed, and the electrode was immersed in a 3% NaCl aqueous solution adjusted to pH 3 for 8 hours, and then the natural electrode potential was measured. In general, the thermal conductivity and the electrical conductivity of a metal are in a proportional relationship, and therefore the electrical conductivity (at 25 ° C.) is measured here instead of the thermal conductivity. Also, 600 ℃
After heating for 3 minutes, the erosion state of the brazing material in the core material was observed by the cross-section metallographic structure to judge the brazing property.

The above results are shown in Table 2.

In the case of Examples 1 to 4 of the present invention, the tensile strength and electrical conductivity after brazing are higher than those of the conventional fin material No. 15, the brazing property is good, and the natural electrode potential is base and sacrificial. Excellent anode effect.

Comparative Example No. 5 has a low tensile strength due to a small amount of Fe in the core material, and No. 6 has a large amount of Fe, on the contrary, a sound fin material cannot be obtained.

No. 7 has a slightly noble natural electrode potential due to the small amount of Zn in the core material. Since No. 8 has a large amount of Zn, its electrical conductivity is slightly low.

No. 9 has a slightly low tensile strength because Cu is not contained in the core material.

No. 10 has a high natural electrode potential due to the large amount of Cu in the core material.

No. 11 has a poor brazing property due to the small amount of Zr and Cr in the core material. No. 12 and No. 13 have low Zr or Cr and therefore have low electrical conductivity.

No. 14 has a low electric conductivity due to a large amount of Mn in the core material, and the natural electrode potential is slightly noble.

No.15 is a conventional fin material with a core material of 3003 + Zn alloy, but its tensile strength is rather low, its electrical conductivity is low, and its natural electrode potential is also slightly noble.

Example 2 The brazing fin material produced in Example 1 was corrugated to form a zinc sprayed extruded tube (material: Al-0.4Cu-0.1M).
n, Zn adhesion amount: 10 g / m ² ) and fluoride flux brazing were performed to prepare a test piece as shown in FIG. This test piece was subjected to a CASS test (JIS D 0201) for 4 weeks and a salt spray test (JIS Z 2371) for 4 weeks to check the maximum corrosion depth of the tube, the corrosion state of the fin and the detachment state of the fin from the tube. It was

The results are shown in Table 3.

In the case of Examples 1 to 4 of the present invention, the maximum corrosion depth was small, the corrosion state of the fins was not abnormal, and the fins were not separated.

In Comparative Examples Nos. 5 to 15, since the tube is a zinc-coated tube, the maximum corrosion depth is small, but No. 7, No. 10, No. 1
In No.4 and No.15, fins were detached, and in No.8, fins were significantly consumed.

Example 3 The brazing fin material prepared in Example 1 was corrugated to form a bare extruded tube (material: Al-0.4Cu-0.1Mn).
Fluoride flux brazing was performed in combination with the above to prepare a test piece as shown in FIG. This test piece was subjected to the SWAAT test (ASTM G43) for 4 weeks, and the maximum corrosion depth of the tube at the fin joint and the corrosion protection distance (the shortest distance from the point where deep pitting occurred at the non-fin joint to the fin joint) ), And examined the corrosion state of the fins.

In the case of the invention examples Nos. 1 to 4, the maximum corrosion depth is small, the corrosion prevention distance is large, and the fin corrosion condition is not abnormal.

Looking at Comparative Examples Nos. 5 to 15, in No. 7, the maximum corrosion depth is large and the corrosion prevention distance is short because Zn is small. No.8
In the case of, since the amount of Zn is large, the fin wear is remarkable. No.1
In the case of 0, the maximum corrosion depth is large due to the large amount of Cu, and the corrosion protection distance is short. In case of No.14, the corrosion prevention distance is short because of the large amount of Mn. The conventional fin material No. 15 has a short anticorrosion distance.

According to the present invention, the thermal conductivity after brazing, the sacrificial anode effect,
In particular, a fin material having an excellent sacrificial anode effect for a zinc-coated tube can be provided, the fin material can be made thinner, and the weight and cost of the heat exchanger can be reduced.

[Brief description of drawings]

FIG. 1A is a front view of a test piece for testing the effect of the present invention, and FIG. 1B is an end view thereof. 1 ... fins, 2 ... tubes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Kato 3-12-12, Minen-ku, Nagoya-shi, Aichi, Sumitomo Light Metal Industries, Ltd. Technical Research Institute (72) Inventor Naoki Tokizo, Minen-ku, Nagoya, Aichi 3-1-12-1 Sumitomo Light Metal Industries, Ltd. Technical Research Institute (72) Inventor Kenji Nekura 1-1-1, Showamachi, Kariya City, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Sadayuki Kamiya Kariya City, Aichi Prefecture 1-chome, Showa-cho, Nippon Denso Co., Ltd. (56) Reference JP-A-55-119146 (JP, A)

Claims (1)

[Claims] 1. Fe: more than 1.0% and 1.8% or less (weight%, the same below), Zn: 0.3 to 3.0%, Cu: 0.3% or less, and further Z
r: 0.05 to 0.25%, Cr: 0.05 to 0.25%, one or two, Mn as an impurity is 0.3% or less, the balance is an aluminum alloy consisting of Al and other unavoidable impurities as a core material, and A brazing fin material for an Al heat exchanger having excellent thermal conductivity after brazing and a sacrificial anode effect, which is characterized in that an Al-Si brazing material is clad on both sides.