JP2000202681A - Aluminum alloy fin material for heat exchanger excellent in brazability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy fin material for heat exchanger excellent in brazability in brazing with using, in particular, fluoride group flux, and good at heat conductivity after brazing, a strength property and a sacrifice anode effect. SOLUTION: An aluminum alloy, which has a composition consisting of, by weight, 0.5-2.0% Mn, 0.1-1.0% Si, 0.1-0.7% Fe, 0.5-4.0% Zn, further one or two kind among 0.006-0.3% Zr and 0.006-0.3% Cr, further a Mg content regulated to <=0.04% as an impurity, and the balance Al with inevitable impurities, is used for a core material, an aluminum alloy brazing filler metal, which has a composition consisting of, by weight, 6-14% Si, 0.006-0.7% Fe, further a Ca content regulated to <=0.006%, a Mg content regulated to <=0.04% and the balance Al with inevitable impurities, is used for a clad material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy fin material for a heat exchanger having excellent brazing properties. More specifically, the fin is brazed to a working fluid passage material such as a car air conditioner, a radiator and a car heater. Alloy fin material used for heat exchangers joined by aluminum, especially for brazing using a fluoride-based flux in an inert gas atmosphere, aluminum for heat exchangers with excellent brazing properties and excellent sacrificial anode effect Related to alloy fin materials.

[0002]

2. Description of the Related Art Heat exchangers such as air conditioners, radiators, intercoolers and oil coolers of automobiles are made of Al-Cu.
It is assembled by brazing a working fluid constituent material composed of a system alloy, an Al-Mn system alloy, an Al-Mn-Cu system alloy, and an Al-Mn system alloy fin material.
The fin material is required to have a sacrificial anode effect in order to prevent corrosion of the working fluid constituent material, and has excellent high-temperature buckling resistance so that it does not deform due to high-temperature heating during brazing and does not penetrate the braze. Required. In addition, the brazing between the fins and the working fluid constituent material is often performed by using an inert gas atmosphere brazing using a fluoride-based flux from the viewpoint of no pollution and low cost. Being superior is also an important requirement.

Conventionally, as clad fin material, Al-
On both surfaces of an aluminum alloy core material obtained by adding Cu, Mg, Zn, Sn, In or the like to a Mn alloy, a brazing material made of an Al-Si alloy, for example, JISBA4343 alloy,
A material obtained by cladding the 4045 alloy or the like is used.

In recent years, there has been an increasing demand for weight reduction and cost reduction of heat exchangers, and it has become necessary to further reduce the thickness of heat exchanger constituent materials such as working fluid passage materials and fin materials. For example, when the fin material is made thinner, the heat transfer performance decreases because the heat transfer cross-sectional area becomes smaller, and there are problems with the strength and durability of the heat exchanger as a product. Further improvement of the strength is desired. Further, when the fin material is thinned, buckling is likely to occur due to high-temperature heating during brazing, and therefore, it is also desired to further improve high-temperature buckling resistance.

In a conventional Al-Mn alloy, Mn works effectively to prevent deformation and erosion of brazing during brazing. However, since Mn forms a solid solution by heating during brazing, the thermal conductivity decreases. There is a problem that. As a fin material that solves this difficulty, an aluminum alloy fin material having a reduced Mn content has been proposed (Japanese Patent Publication No. 63-2322).
No. 60), however, this fin material has insufficient strength after brazing, and has the disadvantage that the fin is likely to collapse or deform during use as a heat exchanger.

As a fin material having improved strength after brazing, improved thermal conductivity and sacrificial anode effect, Al-Mn-
Aluminum alloys in which In, Zn, Ga, Sn, etc. are added to a Si-Mg-Fe alloy have also been proposed (JP-A-4-128337, JP-A-3-20436), and a certain degree of thinning is possible. However, it has not yet been possible to sufficiently satisfy the recent demand for thinner fin materials.

[0007] In recent years, in the brazing of aluminum heat exchangers, brazing using a fluoride-based flux has attracted attention from the viewpoints of pollution-free and low cost. In the brazing to be applied, when an aluminum alloy material containing Mg is used, since the brazing property is inferior, the fin joining rate is reduced, and there is a problem in heat transfer characteristics and durability as a heat exchanger. There is a problem.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems with respect to aluminum alloy fin materials for heat exchangers, satisfies the demand for thinning, and uses a brazing property, particularly a fluoride-based flux. In order to obtain an aluminum alloy fin material with excellent brazing properties in brazing, the effects of alloy components on brazing properties, strength characteristics and sacrificial anode effect, the effects of combinations of alloy components,
It was made as a result of conducting experiments and examinations from various perspectives, and its purpose is to excel in high-temperature buckling resistance during brazing heating, to have high strength after brazing, and to excel in sacrificial anode effect, An object of the present invention is to provide an aluminum alloy fin material for a heat exchanger having excellent brazing properties, particularly in brazing using a fluoride-based flux.

[0009]

According to the present invention, there is provided an aluminum alloy fin material for a heat exchanger having excellent brazing properties according to the first aspect of the present invention, wherein Mn: 0.5 to 2.0%;
Si: 0.1 to 1.0%, Fe: 0.1 to 0.7%, Zn 0.5 to 4.0
%, Zr 0.06 to 0.3%, Cr: 0.06 to
One or two of 0.3%, Mg as an impurity is controlled to 0.04% or less, an aluminum alloy containing the balance of Al and inevitable impurities is used as a core material, and Si: 6 to 14%.
%, Fe: 0.06 to 0.7%, Mg: restricted to 0.04% or less, Ca: restricted to 0.006% or less, and aluminum alloy brazing material consisting of the balance of Al and unavoidable impurities is used as a cladding material. It is characterized by.

[0010] In the aluminum alloy fin material according to the second aspect, the brazing material according to the first aspect further comprises a Bi: 0.01 to
The aluminum alloy fin material according to claim 3 is characterized in that the brazing material further contains 0.5 to 4.0% of Zn: claim 4. The aluminum alloy fin material according to any one of claims 1 to 3, wherein the core material further comprises Cu: 0.05 to 0.3%.
It is characterized by containing.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The significance and the reasons for limiting the alloy components in the aluminum alloy fin material for heat exchangers having excellent brazing properties of the present invention are described below.

<Core alloy> Mn has the effect of increasing the strength. The preferred range is 0.5 to 2.0%. If the content is less than 0.5%, the effect is not sufficient. If the content is more than 2.0%, a coarse compound is formed at the time of casting, and the rolling of the material becomes difficult, and a sound material is obtained. I can't.

[0013] Si has the effect of increasing the strength. A preferred content is in the range of 0.1 to 1.0%, and a content of 0.1 to 1.0%.
If it is less than 1.0%, the effect is not sufficient. If it exceeds 1.0%, the core material may be melted at the time of brazing.

Fe has the effect of increasing the strength. A preferred content is in the range of 0.1 to 0.7%, and a content of 0.1 to 0.7%.
If the amount is less than 0.7%, the self-corrosion resistance of the material deteriorates.

In the case of fluoride flux brazing, Mg (F), a component of the flux, reacts with Mg in the alloy to form a compound such as MgF _2, so that the absolute amount of the flux is insufficient. As a result, the brazing property decreases. When the content of Mg exceeds 0.04%, the effect of reducing the brazing property becomes remarkable. Therefore, the content of Mg is 0.
It is necessary to regulate to below 04%. More preferred content is
0.02% or less.

Zn lowers the potential of the fin material and gives a sacrificial anode effect. The preferred content of Zn is 0.5-4.0%
If the Zn content is less than 0.5%, the effect is not sufficient, and if it exceeds 4.0%, the self-corrosion resistance of the material is deteriorated, the corrosion and wear is remarkable, and the sacrificial anode effect is not maintained for a long time.

Zr and Cr effectively act to improve the high temperature buckling resistance of the fin material, respectively. If the content of each is less than 0.06%, the effect is not sufficient, and if it exceeds 0.3%, a coarse compound is formed at the time of casting, so that rolling of the material becomes difficult and a sound material cannot be obtained. Therefore, Zr and C
The content range of r is preferably 0.06 to 0.3%.

Cu has the effect of improving the strength of the fin material. The preferred content is in the range of 0.05 to 0.3%. If the content is less than 0.05%, the effect is not sufficient, and the content is 0.3%.
Exceeding the potential may make the potential of the fin material noble and impair the sacrificial anode effect.

As other elements, In, Sn, Ga
And the like may be added for the purpose of lowering the potential as a sacrificial anode fin material, but each is preferably 0.1% or less.

<Skin material alloy> Si has the effect of lowering the melting point of the brazing material and increasing the fluidity of the molten brazing material. If the content of Si is less than 6%, the effect is not sufficient. If the content of Si exceeds 14%, the melting point of the brazing material increases, and the workability during the production of the brazing material decreases. Therefore, the content range of Si is 6-14.
% Is preferable.

Fe has the effect of refining the structure of the brazing material after melting and solidifying, and enhancing the fluidity of the molten brazing material. The preferred content is in the range of 0.06 to 0.7%,
If the content is less than 0.7%, the effect is not sufficient. If the content exceeds 0.7%, the effect is saturated and the self-corrosion resistance of the fin after brazing is reduced.

In the case of fluoride flux brazing, Mg is easily concentrated on the fillet surface during the brazing heating process, so that fluorine (F), which is a component of the flux, reacts with Mg in the alloy to form MgF ₂ or the like. Since the compound of formula (1) is generated, the absolute amount of the flux is insufficient and the brazing property is reduced. Therefore, it is necessary to regulate the content of Mg to 0.04% or less. It is more preferably regulated to 0.02% or less.

Since Ca forms a dense oxide on the surface of the brazing filler metal, the wettability and spreadability of the molten solder are reduced, and the brazing property is reduced. If the Ca content exceeds 0.006%, the effect of reducing the brazing property becomes remarkable.
Therefore, it is necessary to regulate the content of Ca to 0.006% or less. It is more preferably regulated to 0.004% or less.

Bi has the effect of lowering the melting point of the brazing material and improving the wettability and flowability of the molten braze. The preferred range of the Bi content is 0.01 to 0.4%. If the content is less than 0.01%, the effect is not sufficient. If the content exceeds 0.4%, the effect is saturated and the self-corrosion resistance of the brazing filler metal decreases. A more preferred content range is 0.1 to 0.4%.

By adding Zn to the brazing alloy, the potential of the brazing alloy is made low, and the fin material has a sacrificial anode effect. The preferred content range is 0.5 to 4.0%,
%, The effect is not sufficient, and if it exceeds 4.0%, the self-corrosion resistance of the fin material is deteriorated, the corrosion and wear are remarkable, and the sacrificial anode effect is not maintained for a long time.

In the skin material of the present invention, as other elements,
In order to improve the brazing properties, a small amount, for example, 0.1% or less of one or more of Be, Sr, Li, and Na may be contained. One or more elements such as In, Sn, and Ga may be added for the purpose of lowering the potential of the brazing filler metal, but each is preferably 0.1% or less. Also, Mn, Cu, Ti, Cr, Zr, Ni
For example, for the purpose of improving the strength of the brazing filler metal, a small amount of such an element may be contained as long as the effects of the present invention are not impaired. However, since the self-corrosion resistance of the brazing filler metal decreases as the added amount increases, the total amount of the added elements is preferably suppressed to 1% or less.

According to the structure of the present invention, Mn and S in the core material
i, to increase the strength after brazing by the inclusion of Fe and Cu, and to lower the potential of the material by including Zn, and to improve the high-temperature buckling resistance by including Zr or Cr, The interaction between these alloy elements enhances the strength after brazing and makes the sacrificial anode effect excellent. Also, by limiting the Mg content,
The reaction between Mg and the flux is prevented, the ratio of the flux that effectively acts in brazing is increased, the fin joining ratio is improved, and a heat exchanger having excellent heat transfer performance and durability can be obtained.

Further, Si as a brazing material constituting the skin material,
By adjusting the combination of the contents of Fe and Bi and limiting the contents of Mg and Ca as impurities, the wettability, spreadability and fluidity of the molten solder are increased, and workability during production is ensured. In addition, an aluminum alloy fin material for a heat exchanger having excellent brazing properties and corrosion resistance can be obtained. Furthermore, by adjusting the amount of Zn added to the brazing material, the sacrificial anode effect can be exhibited by the brazing material, and the sacrificial anode effect of the fin material can be further improved.

The aluminum alloy clad fin material of the present invention is manufactured into an ingot in accordance with a usual melting and casting method, and after homogenization, is subjected to hot rolling, cold rolling, intermediate annealing and cold rolling, and is usually produced in a thickness range. The plate material shall be 0.2 mm or less.
This sheet material is slit to a predetermined width, corrugated, alternately laminated with a working fluid passage material (extruded flat multi-hole tube, etc.) made of an Al-Mn alloy or the like, and heat exchanged by brazing. Unit.

[0030]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 A core material aluminum alloy having the composition shown in Table 1 was melted and continuously cast, and the ingot after the homogenization treatment was chamfered to a thickness of 24 mm to obtain a core material. On the other hand, a brazing alloy having the composition shown in Table 2 was similarly cast, face-cut, and hot-rolled to obtain a skin material having a thickness of 3.0 mm. This skin material was overlaid on both sides of the core material and hot rolled to obtain a clad material having a thickness of 3 mm. After that, cold rolling, intermediate annealing and finish cold rolling were performed to achieve a thickness of 0.
A 12 mm clad fin material (temper: H14) was used.

[0031]

[Table 1]

[0032]

[Table 2]

Next, the obtained fin material was coated with a fluoride-based flux (concentration: 1%) in the same manner as in the brazing using a fluoride-based flux, and then was heated to 600 ° C. in a nitrogen gas atmosphere. For 5 minutes, and a tensile test was performed on the test material after each heating. Further, in order to evaluate the sacrificial anode effect of the fin material after the brazing heat treatment, the fin material was immersed in a 3% NaCl aqueous solution adjusted to pH 3 for 8 hours, and then the natural electrode potential was measured.

Further, the fin material is corrugated,
A corrugated fin material and a JIS 1050 extruded flat multi-hole tube (outer wall thickness: 0.4 mm) were assembled to form a mini core (a miniature model of a heat exchanger core). The brazing of the mini-core was performed in the same manner as the brazing conditions, after applying a fluoride-based flux (concentration: 1%) and then heating at 600 ° C. for 5 minutes in a nitrogen gas atmosphere.

After that, the brazing ratio of the corrugated fin material and the extruded flat multi-hole tube was examined for the mini-core after the brazing and heating, and the brazing property was evaluated from the fin joining ratio. The higher the fin joining ratio, the better the fluidity of the molten braze and the more excellent the brazeability. In the case of brazing a fin material for a heat exchanger for an ordinary vehicle, when the fin joining rate is 70% or less, the performance as a heat exchanger is significantly deteriorated, and the durability is deteriorated due to the unjoined fin material. Therefore, a fin material having a fin joining rate of 70% or less was evaluated as having insufficient brazing properties in a brazing test of a mini core. Further, the rate of change of the fin height before and after brazing was measured, and the high temperature buckling resistance of the fin material was evaluated.

With respect to the evaluation of the corrosion resistance, the mini-core after the above-mentioned brazing heating was subjected to a CASS test according to JIS 86
The test was performed for 2 weeks based on No. 81, and the maximum corrosion depth of the extruded flat multi-hole tube after the test was measured. In addition, the corrosion state of the fin material after the corrosion test was investigated, and the fin material that was significantly depleted due to corrosion (the test material in which 50% or more of the fin material was depleted by corrosion) was evaluated as having a high fin corrosion consumption and insufficient self-corrosion resistance. did. The test, measurement and evaluation results are shown in Tables 3 and 4.

As shown in Tables 3 and 4, fin materials Nos. 1 to 24 satisfying the conditions of the present invention all have a fin bonding ratio.
Excellent brazeability of 85% or more. Further, the natural electrode potential of the fin material of the present invention is as low as −830 mV vs. SCE or less, and the maximum corrosion depth of the extruded flat multi-hole tube after the CASS test is
The thickness was as small as 0.12 to 0.20 mm, indicating that the sacrificial anode effect of the fin material was excellent. Further, the fin material of the present invention is a CAS material.
Corrosion consumption after the S test was small and good self-corrosion resistance was exhibited. Further, the tensile strength corresponding to the fin material of the present invention after brazing (hereinafter, simply referred to as “tensile strength”) showed an excellent strength of 118 MPa or more. In addition, the fin material of the present invention did not have any problem in the productivity of the material, and showed good workability.

[0038]

[Table 3] << Table Note >> Evaluation criteria for high temperature buckling resistance: ○ The rate of change in fin height before and after brazing is 5% or less.

[0039]

[Table 4]

Comparative Example 1 An aluminum alloy for core material having the composition shown in Table 5 was melted, continuously cast, and the ingot after homogenization treatment was chamfered to a thickness of 24 mm to obtain a core material. On the other hand, a brazing alloy having the composition shown in Table 6 was cast, face-cut, and hot-rolled in the same manner to obtain a skin material having a thickness of 3.0 mm. This skin material was overlaid on both sides of the core material and hot rolled to obtain a clad material having a thickness of 3 mm. After that, cold rolling, intermediate annealing and finish cold rolling were performed to achieve a thickness of 0.
A 12 mm clad fin material (temper: H14) was used.

With respect to the obtained fin material, the tensile strength after the brazing heat treatment and the natural electrode potential were measured by the same method as in Example 1, and the fin joining rate and the high-temperature buckling resistance were evaluated. The maximum corrosion depth of the extruded flat multi-hole tube after the CASS test was measured, and the corrosion state of the fin material was investigated. The results are shown in Tables 7 and 8.

[0042]

[Table 5]

[0043]

[Table 6]

[0044]

[Table 7] << Table Note >> Evaluation criteria for high-temperature buckling resistance: ○ when the rate of change in fin height before and after brazing is 5% or less, ○; when rate of change exceeds 5% and when buckling occurs × × * Indicates large fin corrosion consumption

[0045]

[Table 8]

Fin material No. 25 not satisfying the conditions of the present invention
As shown in Tables 7 and 8, none of -47 have sufficient performance as fin materials for heat exchangers. That is, the fin materials Nos. 25, 27, and 29 correspond to the core materials Mn and S, respectively.
Since the contents of i and Fe are small, the tensile strength is low.

The fin materials Nos. 26, 35 and 37 each had a high content of Mn, Cr and Zr in the core material, so that rolling of the material became difficult, and a sound material could not be produced.
In the fin material No. 28, since the core material had a large Si content, local melting occurred during heating during brazing, and buckling occurred in the fin material.

In the fin material No. 30, since the Fe content of the core material is large, self-corrosion of the fin material is severe, corrosion of the fin material after the CASS test becomes remarkable, and the sacrificial anode effect of the fin material is prolonged. Not sustained. Fin material No.31 and No.3
In No. 3, since the Zn content of the core material is small, the natural electrode potential is noble, a through hole is formed in the extruded flat multi-hole tube after the CASS test, and the sacrificial anode effect of the fin material is inferior.

In the fin material No. 32, since the Zn content of the core material was large, the natural electrode potential was extremely low, the fin material was highly corroded, and the fin material was significantly consumed and depleted after the CASS test. Sacrifice anode effect is not maintained for a long time. No. 33 has a high content of Mg in the core material, so a sufficient fillet is not formed, the fin joining rate is low and the brazing properties are poor, and when incorporated in a heat exchanger, the heat transfer characteristics of the heat exchanger descend.

The fin materials Nos. 33, 34 and 36 each had a low Cr or Zr content in the core material, so that their high-temperature buckling resistance was poor, and the fin materials buckled during brazing. Fin material No. 38 has a lower tensile strength than the inventive example containing Cu because the content of Cu in the core material is small.
In No. 39, since the Cu content of the core material was large, the natural electrode potential was noble, a through hole was formed in the extruded flat multi-hole tube after the CASS test, and the sacrificial anode effect of the fin material was inferior.

In the fin material No. 40, since the Si content of the brazing material is small, the fin material is not joined at all (fin joining rate: 0%), and the brazing property is inferior. No.41 is for brazing filler metal Si
, The rollability during the production of the material was not sufficient, and a sound material could not be obtained. No. 42 has a low Fe content in the brazing filler metal, so a sufficient fillet is not formed, the fin joining rate is low and the brazing properties are poor, and when incorporated into a heat exchanger, the heat transfer characteristics of the heat exchanger Lower.

In the fin material No. 43, since the content of Fe in the brazing material is large, the fin material is highly self-corroded, the fin material is significantly consumed by corrosion after the CASS test, and the sacrificial anode effect of the fin material is long. Does not last for hours. In No. 44, the fin material was not joined at all (fin joining rate: 0%) because the Mg content of the brazing material was large, and the brazing property was poor. No.45 is
Since the brazing filler metal contains a large amount of Ca, a sufficient fillet is not formed, the fin joining rate is low and the brazing property is poor, and when incorporated into a heat exchanger, the heat transfer characteristics of the heat exchanger deteriorate.

In the fin materials Nos. 46 and 47, since the contents of Bi and Zn in the brazing material are large, self-corrosion of the fin material is severe, and the corrosion consumption of the fin material after the CASS test becomes remarkable. The sacrificial anode effect is not maintained for a long time. Fin materials No. 42 and No. 45 each had a low fin joint ratio, so the sacrificial anode effect of the fin material on the extruded flat multi-hole tube was insufficient, and the maximum corrosion depth of the extruded flat multi-hole tube after the CASS test Has grown.

[0054]

As described above, according to the present invention, there is provided an aluminum alloy fin material having excellent brazing properties, excellent strength after brazing, and excellent sacrificial anode effect. By using the aluminum alloy fin material, the thickness of the fin material can be reduced, and the weight and the life of the heat exchanger can be reduced.

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Claims (4)

[Claims] 1. Mn: 0.5 to 2.0% (mass%, the same applies hereinafter), Si: 0.1 to 1.0%, Fe: 0.1 to 0.7%, Zn: 0.5
~ 4.0%, Zr: 0.06 ~ 0.3%, Cr:
Containing one or two of 0.06 to 0.3%, limiting Mg as an impurity to 0.04% or less, using an aluminum alloy containing Al and unavoidable impurities as a core material,
1414%, Fe: 0.060.70.7%, Mg: 0.04% or less, Ca: 0.006% or less, aluminum alloy brazing material consisting of balance of Al and unavoidable impurities is used as a cladding material. An aluminum alloy fin material for a heat exchanger having excellent brazing properties. 2. The brazing material constituting the skin material further comprises Bi:
2. The aluminum alloy fin material for heat exchangers having excellent brazing properties according to claim 1, containing 0.01 to 0.4%. 3. The brazing material constituting the cladding material further comprises Zn:
3. The aluminum alloy fin material having excellent brazing properties according to claim 1, wherein the fin material contains 0.5 to 4.0%. 4. The aluminum alloy fin material for a heat exchanger having excellent brazing properties according to claim 1, wherein the core material further contains Cu: 0.05 to 0.3%.