JP2000273565A - High strength aluminum alloy fin material for heat exchanger excellent in thermal conductivity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high strength aluminum alloy fin material for a heat exchanger excellent in thermal conductivity and strength characteristics after brazing and also good in brazing properties and sacrificial anode effect. SOLUTION: This fin material has a compsn. contg. 0.5 to 2.0% Mn, >0.4 to 2% Si and 0.1 to 1.0% Ni, furthermore contg. one or >= two kinds among 0.1 to 1.0% Zn, 0.005 to 0.1% In and 0.01 to 0.1% Sn, and the balance Al with impurities. The ratio of the Mn content to the Si content (Mn/Si) is preferably controlled to 1.0 to 2.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength aluminum alloy fin material for a heat exchanger having excellent heat conductivity, and more particularly to an aluminum alloy heat exchanger joined by brazing, such as a radiator, a heater or an evaporator of a car air conditioner. Used as fins, with excellent thermal conductivity and strength especially after brazing, and excellent sacrificial anode effect,
The present invention relates to a high-strength aluminum alloy fin material for a heat exchanger having good brazing properties.

[0002]

2. Description of the Related Art Aluminum alloy heat exchangers are widely used as heat exchangers for automobile radiators, oil coolers, intercoolers, heaters, and evaporators and condensers for air conditioners. It is assembled by brazing a working fluid passage forming material made of an Al-Cu-based alloy, an Al-Mn-Cu-based alloy or the like, and an Al-Mn-based alloy fin material.

[0003] The fin material is required to have thermal conductivity in order to ensure heat exchange performance, and to have a sacrificial anode effect in order to prevent corrosion of the working fluid constituent material. In addition, good brazing properties are required so that the molten braze does not penetrate during brazing to cause buckling. In recent years, there has been a strong demand for lighter heat exchangers and lower manufacturing costs, and it is necessary to further reduce the thickness of heat exchanger materials such as fin materials. However, since the heat exchange performance deteriorates and the strength and durability of the heat exchanger become problematic, it is desired to further improve the heat conductivity and the strength after brazing of the fin material.

[0004] JI conventionally used as a fin material
Al- such as S 3003 alloy and JIS 3203 alloy
In Mn-based alloys, Mn works effectively to prevent deformation and brazing of brazing, but there is a drawback that Mn is solid-dissolved by heating during brazing, so that thermal conductivity is reduced. In order to solve the difficulties, an aluminum alloy fin material having a reduced Mn content has been proposed (Japanese Patent Publication No. 63-23260). However, the strength of this fin material after brazing is insufficient, and When used as an exchanger, the fins are likely to collapse or deform.

As an aluminum alloy for fins, which has improved strength after brazing and has improved thermal conductivity and sacrificial anode effect, Al-Mn-Si-Mg-Fe alloys have
Aluminum alloys to which n, Zn, Ga, Sn and the like are added have been proposed (Japanese Patent Application Laid-Open Nos. 4-128337 and 3-20436), and although a certain degree of thinning is possible, recent thinning is possible. Has not yet been fully answered.

[0006] In the brazing of aluminum alloy heat exchangers, brazing using a fluoride-based flux has recently attracted attention from the viewpoints of no pollution and low cost. In the brazing joining using a system flux, when an aluminum alloy material containing Mg is used, the brazing property is inferior, so that the fin joining rate is reduced and a problem occurs in the heat transfer characteristics as a heat exchanger.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems in an aluminum alloy fin material for a heat exchanger and obtains an aluminum alloy fin material satisfying the recent demand for thinning. It is a result of repeated experiments and studies on the effects of alloy components and their combinations on various characteristics required for exchanger fins, and the purpose is to achieve high thermal conductivity and strength after brazing. It is an object of the present invention to provide a high-strength aluminum alloy fin material for a heat exchanger having excellent sacrificial anode effect and good brazing property.

[Means for Solving the Problems]

According to the first aspect of the present invention, there is provided a high-strength aluminum alloy fin material for a heat exchanger having excellent thermal conductivity according to the present invention, wherein Mn: 0.5 to 2.0%, Si:
More than 0.4% and 2% or less, Ni: 0.1 to 1.0%, Zn: 0.1 to 1.0%, In: 0.005 to 0.1%, Sn: 0.0
1 to 0.1% of one or more kinds, the balance being A
1 and impurities.

The high-strength aluminum alloy fin material for heat exchangers having excellent thermal conductivity according to claim 2 has a ratio of Mn content to Si content (Mn / S
i) is set to 1.0 to 2.5.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The significance of alloy components in a high-strength aluminum alloy fin material for a heat exchanger according to the present invention and the reasons for limiting the same will be described. Mn coexists with Si to produce an Al-Mn-Si-based compound, improves the strength of the fin material before and after brazing, and improves high-temperature buckling resistance and formability. The preferred range of Mn content is 0.5% to 2.0%. If the content is less than 0.5%, the effect is small. If the content exceeds 2.0%, a coarse compound is formed at the time of casting, which impairs the rolling processability. It is difficult to obtain a clad material, and the amount of solid solution of Mn increases to impair thermal conductivity. A more preferred content range of Mn is 0.5 to 1.6%.
It is.

Si is coexisted with Mn and Al—Mn—Si
System compounds to improve the strength and improve the Mn
To increase the thermal conductivity of the fin material. S
The preferred content range of i is more than 0.4% and not more than 1.5%. If it is more than 0.4%, the effect is not sufficient. If it exceeds 1.5%, the melting point is lowered, and local melting of the fin material is likely to occur during brazing. Become. A more preferred content range of Si is
0.5-1.3%.

Mn and Si are, as described above, Al-Mn.
-Has a function of generating a Si-based compound to reduce the solid solution amounts of Mn and Si, and to improve the thermal conductivity, but has a ratio of Mn content to Si content (Mn / Si) Is less than 1.0, the amount of solid solution of Si increases and thermal conductivity decreases, and when (Mn / Si) exceeds 2.5, the amount of solid solution of Mn increases and thermal conductivity decreases. Therefore, (Mn / S
i) is preferably adjusted in the range of 1.0 to 2.5. A more preferred range of (Mn / Si) is 1.0 to
2.0.

Ni forms fine intermetallic compounds in the alloy matrix and functions to increase the strength without significantly reducing the thermal conductivity. The preferred content of Ni is in the range of 0.1 to 1.0%. If the content is less than 0.1%, the effect is not sufficient. If the content exceeds 1.0%, coarse crystals are formed during casting to reduce workability. Is difficult to manufacture. It also lowers self-corrosion resistance. The more preferable content range of Ni is 0.3 to 1.0%.

Zn makes the potential of the fin material lower and gives a sacrificial anode effect. The preferred content of Zn is 0.1-1.0%
The effect is small at less than 0.1%, 1.0%
%, The self-corrosion resistance decreases, and the thermal conductivity decreases due to the solid solution of Zn. A more preferred range of Zn content is 0.1% or more and less than 0.5%.

In and Sn lower the potential without substantially reducing the thermal conductivity of the fin material, and provide a sacrificial anode effect. Preferred contents of In and Sn are in the range of 0.005 to 0.1% and 0.01 to 0.1%, respectively.
If each is less than the lower limit, the effect is not sufficient, and if each exceeds the upper limit, the effect is saturated and the self-corrosion resistance and the rolling workability are reduced.

In the fin material of the present invention, impurities such as Fe, Cu, Cr, Zr, Ti, V, and Mg may be contained in addition to the above-mentioned alloy components as long as the effects of the present invention are not impaired. . However, Cu is used in order to make the potential of the fin material noble.
It is preferable to limit it to not more than 03%.
Since V significantly reduces the thermal conductivity of the fin material even in a small amount, V is preferably limited to 0.03% or less.

Further, when the brazing using a fluoride-based flux is applied to the assembly of the heat exchanger,
A compound such as MgF ₂ is easily formed by reacting with the fluorine component of the flux component. Due to this, the absolute amount of the flux that works effectively at the time of brazing is insufficient, which causes poor brazing. It is preferable to limit to the following.

The high-strength aluminum alloy fin material for a heat exchanger according to the present invention is obtained by, for example, forming an aluminum alloy having adjusted components by semi-continuous casting, homogenizing, then hot rolling, cold rolling, and intermediate annealing. And finished cold rolling, but it can also be manufactured through continuous casting rolling, cold rolling, intermediate annealing and finish cold rolling.

For example, a fin material finish-rolled to a thickness of 0.1 mm or less is slit into a predetermined width and then corrugated to form fins. For example, a flat plate of a composite plate material obtained by cladding a brazing material with 3003 alloy is used. The working fluid passages are alternately laminated and brazed to form a heat exchanger unit.

[0020]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 An aluminum alloy having the composition shown in Table 1 was ingoted by semi-continuous casting, and subjected to homogenization, hot rolling, cold rolling, intermediate annealing, and finish cold rolling according to a conventional method. 0
The fin material was 7 mm. About the obtained fin material,
The following tests were performed.

Tensile test: A fin material is cut into a predetermined width to obtain a test material, and a fluoride-based flux (concentration: 1%) is applied to the surface of the test material. At 600 ° C. for 3 minutes, and a tensile test was performed on the test material after heating.

Evaluation of thermal conductivity: The electrical conductivity of the test material heated as described above is measured at 25 ° C. In the fin material of the present invention, similarly to general metal materials, there is a proportional relationship between thermal conductivity and electrical conductivity, and it can be seen that thermal conductivity can be evaluated by measuring electrical conductivity. ing.

Evaluation of sacrificial anode effect: The fin material was adjusted to pH 3
After immersion in a 3% aqueous NaCl solution adjusted for 8 hours for 8 hours, the self potential was measured.

Evaluation of brazeability: The fin material was corrugated, and this was added to an aluminum alloy core material containing 1.2% Mn and 0.5% Cu, the balance being Al and impurities.
Plate material (0.3mm) clad with 45 alloy brazing material
Thickness), brazing using a fluoride-based flux is performed, and the brazing joint between the fin and the plate is determined based on the buckling of the fin and the local melting of the fin by observing the cross section of the joint. evaluated.

CASS test: The brazing joint between the fin and the plate is based on JIS H8681.
The CASS test was performed for one month, the maximum corrosion depth of the plate was measured, and the corrosion state of the fin was observed. Table 2 shows the evaluation results.

[0026]

[Table 1]

[0027]

[Table 2] << Table Note >> Brazing performance ○: No local melting, buckling, poor bonding

As can be seen from Table 2, the test material according to the present invention exhibits excellent tensile strength after brazing of 120 MPa or more, electrical conductivity of 45% IACS or more, and the conventional JIS. It has better thermal conductivity than 3N23 alloy fin material (electrical conductivity 35% IACS). It is also excellent in brazing properties, has a self potential of -760 to -800 mV vs SCE, is electrochemically sufficiently low, and has a maximum corrosion depth of 0.08 to 0.11 mm after the CASS test. This indicates that the fin has an excellent sacrificial anode effect.

Comparative Example 1 An aluminum alloy having a composition shown in Table 3 was ingoted by continuous casting, and an aluminum alloy fin material having a thickness of 0.07 mm was obtained by the same process as in Example 1 above. Regarding the fin material, the tensile strength, thermal conductivity, sacrificial anode effect, brazing property,
The corrosion resistance of the joint was evaluated. Table 4 shows the evaluation results. In Table 3, those out of the conditions of the present invention are underlined.

[0030]

[Table 3]

[0031]

[Table 4] << Table Note >> Brazing properties ○: No local melting, buckling, poor bonding ×: Any of local melting, buckling, poor bonding

As shown in Table 4, the test material No. 13 is M
Since the amount of n is small, the tensile strength is insufficient. Test material N
o. In No. 14, since the Mn content was large, hot rolling was difficult and a sound material could not be produced. Test material No. 1
In No. 5, the tensile strength is not sufficient because the amount of Si is small. Test material No. No. 16 buckled due to local melting of the fins during brazing heating due to high Si content.

Test material No. No. 17 has insufficient tensile strength because of a small Ni content. Test material No. 18 is Ni
Due to the large content, hot rolling became difficult and a sound material could not be produced. Test material No. 19 is Zn, I
Since the content of n and Sn was small and the natural electrode potential was noble, the sacrificial anode effect was inferior, and a through-hole was formed in the plate in the CASS test. The test material No. 19 is (M
Since the (n / Si) ratio was small, the amount of solid solution of Si increased and the electrical conductivity decreased, resulting in poor thermal conductivity.

Test material No. 20, no. 21, no. 2
In No. 2, since the contents of Zn, In, and Sn are large, the natural electrode potential becomes too low, the self-corrosion is increased, and the corrosion consumption of the fin material becomes remarkable, and the sacrificial anode effect of the fin material is not maintained. The test material No. In No. 20, since the (Mn / Si) ratio was large, the solid solution amount of Mn was increased, the electric conductivity was lowered, and the heat conductivity became insufficient.

Test material No. 23, no. 24, no. 2
No. 5 corresponds to JIS3003 alloy, 3203 alloy and 3N23 alloy, respectively, does not contain Ni, has a small amount of Si, has insufficient tensile strength, and has a large (Mn / Si) ratio. And the electrical conductivity decreased, resulting in poor thermal conductivity. The test material No.
In No. 25, since the Zn content is large, the natural electrode potential becomes too low, the self-corrosion becomes large, and the corrosion consumption of the fin material becomes remarkable, and the sacrificial anode effect of the fin material is not maintained.

Test material No. 26 corresponds to a JIS 3005 alloy and contains a large amount of Mg, so that the brazing property is degraded and the bonding failure of the fins is increased, and the (Mn / Si) ratio is large, so that the amount of Mn solid solution increases and the The conductivity was low, and the thermal conductivity was poor. The test material No.
23, no. 24 and No. 26 is Zn, In, S
Since no n was contained and the natural potential was noble, a through hole was formed in the plate.

[0037]

According to the present invention, there is provided a high-strength aluminum alloy fin material for a heat exchanger having excellent heat conductivity and strength characteristics after brazing, and also having good brazing properties and a sacrificial anode effect. By using the fin material, the thickness of the fin can be reduced, and the weight and the life of the heat exchanger can be reduced.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Taketoshi Toyama 1-1-1, Showa-cho, Kariya-shi, Aichi Pref. Denso Corporation (72) Inventor Yoshihiko Kamiya 1-1-1, Showa-cho, Kariya-shi, Aichi Co., Ltd. Within Denso (72) Inventor Masaji Bibo 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industries Co., Ltd. (72) Inventor Yuji Hisatomi 5-113-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Within Metal Industry Co., Ltd. (72) Inventor Hiroshi Ikeda 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industry Co., Ltd.

Claims (2)

[Claims] 1. Mn: 0.5 to 2.0% (weight%, the same applies hereinafter), Si: more than 0.4%, 2% or less, Ni: 0.1 to 1.0%, Zn: 0.1 to 1.0%, In: 0.005 ~ 0.1
%, Sn: 0.01 to 0.1%. A high-strength aluminum alloy fin material for heat exchangers having excellent thermal conductivity, comprising one or more of 0.01 to 0.1% and the balance of Al and impurities. 2. The ratio of Mn content to Si content (Mn / S
2. The method according to claim 1, wherein i) is 1.0 to 2.5.
A high-strength aluminum alloy fin material for a heat exchanger having excellent heat conductivity as described above.