JPH0686640B2 - Aluminum alloy for heat exchanger fin material which has excellent thermal conductivity after brazing and sacrificial anode effect - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an aluminum alloy for a fin material of a heat exchanger in which a fin and a working fluid passage constituent material are joined by brazing such as a radiator and a car air conditioner. In particular, the present invention relates to an aluminum alloy for a fin material, which has a high thermal conductivity after brazing and has an excellent sacrificial anode effect.

[Prior Art] In radiators of automobiles, air conditioners, heat exchangers such as intercoolers and oil coolers, working fluid passage configurations of Al-Cu alloys, Al-Mn alloys, Al-Mn-Cu alloys, etc. The material and the aluminum alloy fin material are assembled by brazing. And, the fin material is required to have a sacrificial anode effect in order to prevent corrosion of the working fluid passage constituent material, and it may be deformed by high temperature heating during brazing,
Excellent high temperature buckling resistance is required so that the wax does not corrode. Mn to prevent deformation and brazing erosion during brazing
Is effective, and Al-Mn alloys such as 3003 alloy and 3203 alloy are used for the fin material. 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 (for example, JP-A-62-1
However, in order to further improve the high temperature buckling resistance (high temperature sag resistance), a method of adding Cr, Ti, Zr or the like (see, for example, Japanese Patent Application Laid-Open No. 50-118919). Is proposed.

[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 alloys, Mn forms a solid solution at high temperature during brazing, so thermal conductivity The degree of decrease is remarkable. In order to improve the thermal conductivity, pure aluminum (1050, 1070, etc.) is Zn, Sn, In or C.
Attempts have also been made to use fin materials to which r, Ti, Zr, etc. have been added, but in this case, fin collapse is likely to occur due to the low thermal strength after brazing, which is the root cause of the problem. Not a solution.

The present invention is intended to solve this point fundamentally.

[Means for Solving the Problems] The present inventors have studied various aluminum alloys, and compared with conventional Al-Mn alloys, the thermal conductivity without significantly lowering the strength after brazing. Greatly improved,
The present invention has been completed by finding an aluminum alloy for fin materials which is excellent in sacrificial anode effect and high temperature buckling resistance.

That is, the present invention, Fe: more than 1.0% and 1.8% or less, Zr: 0.
05-0.20%, Zn: 0.3-2.0%, Cu: 0.3% or less,
An aluminum alloy for a fin material of a heat exchanger, which is excellent in thermal conductivity after brazing and sacrificial anode effect, characterized by comprising the balance Al and unavoidable impurities.

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

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. The more Fe, the stronger the strength
If it exceeds 1.8%, coarse crystallized substances are generated during casting, making it difficult to manufacture a plate material.

Zr: Zr improves 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.

Zn: Zn makes the electric potential of the fin material base and gives a sacrificial anode effect. If it is less than the lower limit, the effect is not sufficient, and if it exceeds the upper limit, not only the effect is saturated, but also the self-corrosion resistance is deteriorated.

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.

Other elements may include Si, Mn, Mg, Cr, 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, so
Si less than 0.6%, Mn less than 0.1%, Mg less than 0.2%, Cr less than
It is desirable that 0.05% or less and Ti be 0.05% or less. Mg
When reacting with fluoride flux brazing, it reacts with the flux, so it is desirable to keep it lower, that is, 0.1% or less. Ti may be added as an alloying element for refining the crystal during casting or as an Al-Ti-B refining agent, but it is desirable to suppress it within the above range.

[Examples] 14 alloys shown in Table 1 were melted and cast, homogenized,
Hot rolling, cold rolling, intermediate annealing and finish cold rolling were performed to obtain a fin material having a thickness of 0.07 mm. Next, after heating in nitrogen gas at 600 ° C for 3 minutes in the same manner as brazing, tensile test and electrical conductivity measurement were performed, and after immersion for 8 hours in a 3% NaCl aqueous solution adjusted to pH 3, The natural electrode potential was measured. In general, the thermal conductivity and the electrical conductivity of a metal are in a proportional relationship, so here, the electrical conductivity (at 25 ° C.) is measured instead of the thermal conductivity.

Further, the fin material was corrugated, placed on a plate material having 3003 as a core material and 4045 as a skin material (brazing material), and was subjected to fluoride flux brazing to examine brazing properties. And CASS about the joint of fin and plate
The test (JIS D0201) was conducted for one month, the maximum corrosion depth of the plate was examined, and the corrosion state of the fin was observed.

The results are also shown in Table 1.

Inventive examples Nos. 1 to 4 have high tensile strength of 8.8 kgf / mm ² or more,
It also has a high electrical conductivity of over 50%. Moreover, the brazing property is also good, and the natural electrode potential is as low as -770 mVvsSCE or less,
The maximum corrosion depth of the plate material is as small as 0.06 to 0.07mm, and it has excellent sacrificial anode effect. Comparative Example No. 6 has a low tensile strength due to a small amount of Fe. Since No. 7 has a large amount of Fe, a sound fin material is not obtained, and the tensile strength tends to be saturated, and the effect of increasing Fe cannot be seen. No. 8 has a small amount of Zr, so the brazing material is eroded in the fin material during brazing and the fins buckle. No. 9 has a large amount of Zr and therefore has low electric conductivity. Since No. 10 has a small Zn content, the natural electrode potential is noble at −710 mVvsSCE, and the maximum corrosion depth of the plate material is large at 0.50 mm, so the sacrificial anode effect is not sufficient. No.11
Since Zn has a large amount of Zn, the self-corrosion resistance of the fin material is inferior and the fin wear is remarkable.

No. 12 has a large natural electrode potential of -720 mVvs SCE due to the large amount of Cu, and the maximum corrosion depth of the plate material is large at 0.43 mm, so the sacrificial anode effect is not sufficient. N0.13 is the case of JIS3003 alloy to which Mn and Cu have been added, which has been used as a fin material in the past, and has low electric conductivity of 38% IACS and low thermal conductivity. In addition, the natural electrode potential is noble at -700 mVvsSCE, the maximum corrosion depth of the plate material is as large as 0.46 mm, and the sacrificial anode effect is not sufficient. N0.14 contained 1.4% Mn 32
Although it is the case of 03 alloy, it has almost the same performance as No.13.

[Advantages of the Invention] According to the present invention, a fin material having excellent thermal conductivity, sacrificial anode effect, high temperature buckling resistance, and strength can be provided, the fin material can be thinned, and the weight of the heat exchanger can be reduced. Contributes to cost reduction.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaji Mifusa 3-12-12, Chiennen, Minato-ku, Nagoya, Aichi Prefecture, Sumitomo Light Metal Industry Co., Ltd. Technical Research Institute (72) Kenji Kato, Chitose, Minato-ku, Aichi Prefecture 3-12, Sumitomo Light Metal Industries, Ltd. Technical Research Laboratory (56) Reference JP-A-55-119146 (JP, A) JP-A-62-182244 (JP, A)

Claims (1)

[Claims] 1. Fe: more than 1.0% and 1.8% or less (% by weight, the same applies hereinafter), Zr: 0.05 to 0.20%, Zn: 0.3 to 2.0%, Cu: 0.3% or less, and the balance Al and unavoidable An aluminum alloy for a fin material of a heat exchanger, which is excellent in thermal conductivity after brazing and a sacrificial anode effect, which is made of impurities.