JPH0390529A - Aluminum alloy for heat exchanger fin material excellent in thermal conductivity after brazed and sacrificial anode effect - Google Patents

Abstract

PURPOSE:To manufacture the Al alloy for a heat exchanger fin material having high thermal conductivity after brazed and excellent in sacrificial anode effect by preparing an Al alloy contg. specified ratios of Fe, Si, Mn, Zr and Zn. CONSTITUTION:An Al alloy contg., by weight, 0.2 to 1.8% Fe, 0.2 to 0.6% Si, 0.1 to 0.35% Mn, 0.05 to 0.20% Zr and 0.5 to 2.0% Zn, furthermore contg., at need, <=0.3% Cu and the balance Al with inevitable impurities is prepd. In this way, the fin material excellent in high temp. buckling resistance and strength and capable of thinning can be obtd., by which the lightening in weight and the reduction of cost in a heat exchanger can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an aluminum alloy for the fin material of a heat exchanger, such as a radiator or a car air conditioner, in which the fins and the material forming the working fluid passage are joined by brazing. In particular, the present invention relates to an aluminum alloy for fin material that has high thermal conductivity after brazing and excellent sacrificial anode effect.

[Prior Art] In heat exchangers such as radiators, air conditioners, intercoolers, and oil coolers for automobiles, working fluid passage structures such as Al-Cu alloys, Al-Mn alloys, and Al-Mn-Cu alloys are used. The material and the aluminum alloy fin material are assembled by brazing. The fin material is required to have a sacrificial anode effect to prevent corrosion of the working fluid passage material, and also has excellent high-temperature buckling resistance to prevent deformation due to high-temperature heating and corrosion of the solder during brazing. sexuality is required. Adding Mn is effective in preventing deformation and corrosion of the solder during brazing, and Al-Mn alloys such as 3003 alloy and 3203 alloy are used as the fin material. In order to impart a sacrificial anode effect, a method of electrochemically making the Al-Mn alloy less noble by adding Zn5SnS In, etc.
120455), but in order to further improve the high temperature buckling resistance (high temperature sag resistance), Cr5Ti
A method of adding SZr etc. (for example, JP-A-50-118
919) has been proposed.

[Problems to be Solved by the Invention] In recent years, there has been a strong demand for lighter heat exchangers and lower costs. It is now necessary to make the materials thinner (such as materials). However, when the fin material is made thinner, the heat transfer cross-sectional area becomes smaller, which poses a problem in that heat exchange performance is impaired.

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 dissolves in solid solution at high temperatures during brazing, so thermal conductivity There is a significant decrease in the degree of As a fin material with excellent thermal conductivity, Mn2: 0.1 to 0.8%, Zr: 0.02 to
Aluminum alloys containing Si: 0.2% and Si: 0.1 to 0.8% have also been proposed (Japanese Patent Publication No. 83-23280
In this case, since M n Q is small,
The strength after brazing is low, and the fins tend to collapse or deform during use. Furthermore, since the potential of the fin material is not base, the sacrificial anode effect is small. Moreover, Si: 0.03 to 0.3%
, Fe: 0.05-0.6%, Zr:
0.01-0.4%, Mn: 0.01-0.3
Aluminum alloys containing one or two types of
In this case, since the potential of the fin material is not base, the sacrificial anode effect is small. In addition, pure aluminum (10
Attempts have also been made to use fin materials made by adding Zns Sns In or Cr, Ti, Zr, etc. to 50, 1070, etc.; The fins tend to fall down, and this does not fundamentally solve the problem.

The present invention aims to fundamentally solve this problem.

[Means for Solving the Problems] The present inventors have studied various aluminum alloys, and have found that they have improved thermal conductivity without significantly lowering the strength after brazing compared to conventional AI-Mn alloys. We have discovered an aluminum alloy for fin materials that has significantly improved heat resistance, sacrificial anode effect, and high-temperature buckling resistance, and completed the present invention.

That is, in the present invention, Fe: 0.2 to 1.8%
, Si: 0.2-0.8%, Mn: 0.
1-0.35%, Zr: 0.05-0.20%,
Zn: 0.5-2.0% or further Cu: 0.3%
This is an aluminum alloy for heat exchanger fin material having excellent post-brazing thermal conductivity and sacrificial anode effect, containing the following, with the balance being 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, as well as the strength after brazing. Since the present invention alloy contains Mn and 3i, Fe: 0.2
% or more, strength improvement effects appear. If it is less than 0.2%, the effect is not sufficient. On the other hand, if it exceeds 1.8%, coarse crystallized substances will be generated during casting, making it difficult to manufacture plate materials.

Si: Si is At-Mn-5t system or Al-Mn-
A Fe-5i-based compound is produced to reduce the amount of solid solution of Mn and improve thermal conductivity. If the content is less than 0.2%, the effect will not be sufficient (and if it exceeds 0.8%, the thermal conductivity will decrease).

Mn: Like Fe, improves strength before and after brazing. It also improves high temperature buckling resistance and moldability. If it is less than 0.1%, the effect is not sufficient, and 0.35%
When the temperature exceeds 100%, the thermal conductivity decreases.

Zr: Zr improves high temperature buckling resistance. If it is less than the lower limit, the effect will not be sufficient, and if it exceeds the upper limit, the thermal conductivity after brazing will decrease.

Zn: Zn makes the potential of the fin material less noble and provides a sacrificial anode effect. In the case of the alloy of the present invention, Mn makes the potential nobler.
Therefore, the sacrificial anode effect is not sufficient unless the Zn content is 0.5% or more. When it exceeds 2.0%, not only the effect is saturated, but also self-corrosion resistance deteriorates.

Cu: Cu improves strength after brazing.

If it exceeds 0.3%, the potential of the fin material becomes noble and the sacrificial anode effect is impaired.

Other elements may include Mg s Cr, Ti, etc. within a range that does not impair the effects of the alloy of the present invention. however,
As the content of both increases, the thermal conductivity decreases, so
Mg is 0.2% or less, Cr is 0.05% or less, Ti is 0
．． It is desirable to make it 0.5% or less. Since Mg reacts with the flux when fluoride flux brazing is performed, it is desirable to keep it even lower, that is, to 0.1% or less. Ti may be added as an alloying element for crystal refinement during casting or as an Al-Ti-B refiner, but it is desirable to suppress it within the above range.

[Example] Alloy Nos. 1 to 23 having the compositions shown in Table 1 were melted and cast, subjected to homogenization treatment, hot rolling, cold rolling, intermediate annealing, and final cold rolling to a thickness of 0.07 mm. fin material was obtained. In order to obtain the conditions for the obtained fin material after brazing, it was heated in nitrogen gas at 800° C. for 3 minutes in the same manner as during brazing, and then a tensile test and thermal conductivity were measured. Generally, there is a proportional relationship between the thermal conductivity and electrical conductivity of metals, so here we will use electrical conductivity (25℃) instead of thermal conductivity.
was measured. In addition, in order to evaluate the sacrificial anode effect, pH 3
After 8 hours of immersion in a 3% NaCl aqueous solution adjusted to 3%, the natural electrode potential was measured.

Further, the fin material was subjected to corrugation processing, placed on a plate material having 3003 as a core material and 4045 as a skin material (brazing material), and fluoride flux brazing was performed to examine brazing properties. Also, regarding the joint between the fin and the plate, CA
An SS test was conducted for one month based on JISD 0201, the maximum corrosion depth of the plate was measured, and the state of corrosion of the fins was observed.

The results are also listed in Table 1.

Alloy Nos. 1 to 10 materials according to the present invention have a tensile strength of C
Those that do not contain u are 8.0 kgf/lmm2 or more, C
Those containing u had a high electrical conductivity of 8.5 kgf'/1112 or more, and all had high electrical conductivities of 46% or more (conventional material 3003 was 39%), indicating high thermal conductivity.

In addition, the brazing properties are good, and the natural electrode potential is -740.
to -780 mV vs S CE and is electrochemically base. Further, the maximum corrosion depth of the plate material after the CASS test is as small as 0□07 mm or less, and the sacrificial anode effect is excellent. Furthermore, the corrosion of the fins is also normal. On the other hand, comparative alloy No. 11 has a low tensile strength of 7.2 kgf'/in 2 because the Fe content is as low as 0.10%.

In No. 12, since the Fe content was as high as 2.10%, coarse crystallized substances were generated during casting, making rolling difficult, and the test was discontinued.

No. 13 has a low Si content of 0.09%, so
Its electrical conductivity is as low as 42% lAC3, and its thermal conductivity is low.

No. 14 has a high Si content of 0.83%, so the electrical conductivity is low at 42% IACS, and the thermal conductivity is low.

No. 15 has a low Mn content of 0.04%, so
Tensile strength is low at 7.1kgf'/Il+m'.

No. 1B has a high Mn content of 0.49%, so its electrical conductivity is low at 42%lAC3, and its thermal conductivity is low.

No. 17 is 2 "Due to the low content of 0.02%, buckling occurred in the fin during the brazing test. This was due to the erosion of the solder into the fin material.

No. 1B has a high Zr content of 0.25%, so its electrical conductivity is low at 42%lAC3, and its thermal conductivity is low.

In No. I9, since the Zn content is as low as 0.3%, the natural electrode potential is 1700+nV vs S CE, which is electrochemically noble and inferior in sacrificial anode effect. Therefore, the maximum corrosion depth of the plate material also increased to 0.41 mm.

In No. 20, since the Zn content was as high as 2.5%, the self-corrosion resistance of the fin material was poor, and the wear of the fins was significant.

Since No. 21 has a high Cu content of 0.45%, the natural electrode potential is 1690 mV vs S CE, which is electrochemically noble and inferior in sacrificial anode effect. For this reason, the maximum corrosion depth of the plate material also increased to 0°411.

No. 22 is the case of 3003 alloy, which has been used conventionally, and has a low electrical conductivity of 39% IACS and a low thermal conductivity. In addition, the natural electrode potential is 170011IVvsS
It is electrochemically nobler than CE and inferior in sacrificial anode effect. Therefore, the maximum corrosion depth of the plate material is 0.42aa.
It got bigger.

No, 23 is Z in the conventionally used 3003 alloy.
This is the case when n is added, and the natural electrode potential becomes 1740a+VvsS CE due to the inclusion of Zn, and the sacrificial anode effect is improved, but the electrical conductivity is as low as 37% lAC3, and the thermal conductivity is low.

[Effects of the Invention] According to the present invention, a fin material with excellent thermal conductivity, sacrificial anode effect, high-temperature buckling resistance, and strength can be provided, and the fin material can be made thinner, making the heat exchanger lighter. Contributes to cost reduction.

Claims (2)

[Claims] (1) Fe: 0.2 to 1.8% (weight%, same below),
Si: 0.2-0.6%, Mn: 0.1-0.35%,
Zr: 0.05-0.20%, Zn: 0.5-2.0%
An aluminum alloy for a heat exchanger fin material having excellent post-brazing thermal conductivity and sacrificial anode effect, the balance being Al and unavoidable impurities. (2) Fe: 0.2-1.8%, Si: 0.2-0.6
%, Mn: 0.1-0.35%, Zr: 0.05-0.
20%, Zn: 0.5-2.0%, Cu: 0.3% or less, with the remainder consisting of Al and unavoidable impurities.It has excellent thermal conductivity and sacrificial anode effect after brazing. Aluminum alloy for heat exchanger fin material.