JPH11269590A - High strength aluminum alloy fin material for heat exchanger, excellent in brazability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an aluminum alloy fin material having superior brazability, excellent in strength after brazing, thermal conductivity, and sacrificial anode effect, and capable of reducing the thickness of a fin. SOLUTION: This material has a composition which consists of 0.8-2.0% Mn, 0.4-1.3% Si, Mg and Cu as impurities in the amounts limited to <0.01% and <0.02%, respectively, and the balance Al with inevitable impurities and in which the ratio between Mn content and Si content (Mn/Si) is specified to 1.0-3.5. Further, either or both of 0.06-0.25% Zr and 0.06-0.25% Cr can be added.

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 brazing properties.
Aluminum alloy fin material used for heat exchangers in which fins and working fluid path constituent materials are joined by brazing, such as radiators, car heaters, car air conditioners, etc.
In particular, the present invention relates to an aluminum alloy fin material for a heat exchanger which is excellent in brazing property in a fluoride flux brazing, has high thermal conductivity and strength after brazing, and has excellent sacrificial anode effect.

[0002]

2. Description of the Related Art Heat exchangers such as automobile radiators, air conditioners, intercoolers, oil coolers, etc.
It is assembled by brazing a working fluid constituent material such as a Cu-based alloy, an Al-Mn-based alloy, an Al-Mn-Cu-based alloy, and an Al-Mn-based alloy fin.
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, in order to braze the fin and the working fluid constituent material, brazing using a fluoride-based flux is often applied from the viewpoint of no pollution and low cost, and in this case, the brazing property is excellent. It is an important factor.

[0003] Al-Mn based aluminum alloys such as JIS 3003 and JIS 3203 are used as fin materials.
This is because it works effectively to prevent deformation during brazing and erosion of the brazing. In order to impart a sacrificial anode effect to the Al-Mn alloy fin material, Zn, Sn, I
a method of electrochemically lowering the concentration by adding n
In order to further improve the high-temperature buckling resistance (high-temperature sag resistance), a method of incorporating Cr, Ti, Zr, etc. into an Al-Mn alloy (Japanese Patent Laid-Open No. 1
No. 18919).

However, recently, weight reduction and cost reduction of heat exchangers have been increasingly required, and materials for working fluid passages,
It is necessary to further reduce the thickness of the heat exchanger constituent materials such as fin materials.For example, if the fins are made thinner, the heat transfer cross-sectional area becomes smaller, resulting in a decrease in heat exchange performance. Since the strength and durability of the exchanger also have problems, further improvement in heat transfer performance and strength after brazing is desired.

[0005] In the conventional Al-Mn alloy, there is a problem that Mn is dissolved by heating at the time of brazing, so that the thermal conductivity is reduced. As a fin material that solves this difficulty, the Mn content is limited to 0.8% or less, and Zr 0.02 to 0.2
Aluminum alloys containing 0.1% to 0.8% Si and 0.1 to 0.8% Si have been proposed. (Japanese Patent Publication No. 63-23260) Although this alloy has improved thermal conductivity, the strength after brazing is not sufficient due to the small amount of Mn, and the fins are likely to collapse or deform during use as a heat exchanger. In addition, there is a disadvantage that the sacrificial anode effect is small because the potential is not sufficiently low.

Mn 0.3-2.5%, Si 0.5-1.5%, M
Al alloy fins containing g 0.01 to 1%, Zr 0.01 to 0.3%, and Zn 0.1 to 3% have also been proposed (JP-A-8-1439).
However, this fin material is inferior in brazing property in fluoride flux brazing. Mn 0.01-0.3%,
One or two kinds of Zr 0.01-0.4%, Si 0.03
Aluminum alloys for fins containing 0.3 to 0.3% Fe and 0.05 to 0.6% Fe have also been proposed (JP-A-63-45352).
This alloy also has a small sacrificial anode effect because the potential is not sufficiently low. In addition, pure aluminum with high thermal conductivity (JIS 1050,
Attempts to improve the high temperature buckling resistance by adding Zn, Sn, In to ZnO or adding Cr, Ti, Zr, etc. have been made. Although the heat transfer performance is excellent, the strength after brazing is not always sufficient.

[0007] As a fin material with improved strength after brazing, Al, Mn-Si-Mg-Fe-based alloys are added to In and Zn.
Aluminum alloys added with Ga and Sn added with Ga, Sn, etc. have also been developed (JP-A-4-128337).
Japanese Patent Application Laid-Open No. Hei 3-20436), it is possible to reduce the thickness to some extent, but it has not yet sufficiently satisfied the recent demand for thinner fin materials. In addition, when brazing using a fluoride-based flux is applied, the alloy material containing Mg is inferior in brazing properties, so that the fin joining rate is reduced, which causes a problem in heat transfer characteristics as a heat exchanger. There are points.

[0008]

SUMMARY OF THE INVENTION The present invention provides an aluminum alloy fin material which satisfies the demand for thinner fin materials for heat exchangers and which is excellent in brazing properties, in particular, brazing properties using a fluoride flux. The purpose of the development was to examine the effects of alloy components on the strength characteristics, heat transfer performance, sacrificial anode effect and brazing properties, and the effects of combinations of alloy components from various perspectives. To provide an aluminum alloy fin material for heat exchangers that has high strength and thermal conductivity after brazing, has an excellent sacrificial anode effect, and has good brazing properties, particularly in brazing using a fluoride-based flux. is there.

[0009]

The high-strength aluminum alloy fin material for a heat exchanger according to the present invention for achieving the above object contains 0.8 to 2.0% of Mn and 0.4 to 1.3% of Si,
The ratio of the Mn content to the Si content (Mn / Si) is 1.0 to
3.5, Mg as an impurity is less than 0.01%, and Cu is 0.1%.
The first feature is that the content is limited to less than 02%, the balance being Al and unavoidable impurities, Mn 0.8-2.0%, Si 0.4-
1.3%, Zr 0.06-0.25%, Cr 0.06-
Mn content and S content including one or two of 0.25%
The second feature is that the ratio (Mn / Si) to the i content is 1.0 to 3.5, Mg as an impurity is limited to less than 0.01%, Cu is limited to less than 0.02%, and the balance consists of Al and unavoidable impurities. I do.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The significance of alloy components in an aluminum alloy fin material for a heat exchanger of the present invention and the reasons for limitation will be described. Mn forms an Al-Mn-Si-based compound by coexisting with Si. In addition, the strength of the alloy material before and after brazing is improved, and the high-temperature buckling resistance and the formability are improved. If the Mn content is less than 0.8%, the effect is not sufficient. If the Mn content is more than 2.0%, coarse crystals are formed during casting of the alloy, making it difficult to produce a sheet material.
The amount of solid solution of n increases and the thermal conductivity decreases. Therefore, a preferable content range is 0.8 to 2.0%. A more preferred content range of Mn is 1.0 to 1.6%.

Si is coexisted with Mn and Al—Mn—Si
System compounds to improve the strength and improve the Mn
To improve the thermal conductivity by reducing the amount of solid solution. If the Si content is less than 0.4%, the effect is not sufficient, and if it exceeds 1.3%, the fin material may be melted at the time of brazing. Therefore, the preferred content range is 0.4 to 1.3%. A more preferred content of Si is more than 0.6% and 1.2%
The range is as follows.

Mn and Si are, as described above, Al-Mn.
-Has a function of generating a Si-based compound to reduce the solid solution amount of Mn and Si, and to improve thermal conductivity.
When the ratio (Mn / Si) between the content and the Si content is less than 1.0, the amount of solid solution of Si increases and the thermal conductivity decreases, and when it exceeds 3.5, the amount of solid solution of Mn increases and the thermal conductivity increases. Decrease. Therefore, the ratio of the Mn content to the Si content (Mn / Si) is
A range of 1.0 to 3.5 is preferred. The more preferable range of Mn / Si is 1.3 to 2.5.

Zr and Cr are elements that function to improve the high temperature buckling resistance of the fin material.
If it is less than 0.25%, the effect is small, and if it exceeds 0.25%, the workability is reduced and the production of the plate material becomes difficult. Therefore,
The preferred contents of Zr and Cr are respectively 0.06 to 0.
It is in the range of 25%.

[0014] Mg affects the brazing property, and the content of Mg is 0.
If it exceeds 01%, brazing properties may be impaired. In particular, in the case of the brazing of a flux based on a fluoride, the fluorine (F) as a component of the flux easily reacts with Mg in the alloy, so that a compound such as MgF ₂ is formed, which effectively acts at the time of brazing. Insufficient amount of flux is generated, and poor brazing is likely to occur. Therefore, the content of Mg as an impurity is limited to less than 0.01%.

Cu makes the potential of the material noble and reduces the sacrificial anode effect. In particular, when elements such as Zn, In, Sn, and Ga that give a sacrificial anode effect by making the potential low are not added, the effect of making the potential noble even when Cu is contained in a small amount is remarkable. In order to maintain the potential of the material low and to have a sacrificial anode effect, the Cu content must be reduced.
Preferably it is limited to less than 0.02%, more preferably
It shall be less than 0.01%.

Regarding impurity components other than Mg and Cu,
Zn, In, Sn, and Ga make the potential of the material low, increase the self-corrosion, and deteriorate the recyclability.
It is preferable to limit the content of In, Sn, and Ga to less than 0.1%, respectively. Further, Fe is preferably set to 0.4% or less to increase self-corrosion.

The aluminum alloy fin material of the present invention is formed into an ingot according to a usual melting and casting method, and after homogenization,
It is manufactured through hot rolling, cold rolling, intermediate annealing and finish cold rolling, and is usually a sheet material having a thickness of 0.1 mm or less. This plate material was corrugated after slitting to a predetermined width, and was coated with a working fluid passage material, for example, a brazing material.
A heat exchanger unit is formed by alternately stacking flat tubes made of clad plates made of 3003 alloy or the like and brazing them.

According to the structure of the present invention, the coexistence of Mn and Si produces an Al—Mn—Si compound, and the (Mn / Si) ratio is adjusted to reduce the amount of solid solution of Mn and Si. By adding at least one of Zr and Cr, the high-temperature buckling resistance of the material is improved, and the strength and thermal conductivity after brazing are enhanced by the interaction of these alloy elements, and the sacrificial anode effect is improved. It shall be assumed. In addition, the sacrificial anode effect is maintained by limiting the Cu content, the reaction between Mg and flux is prevented by limiting the Mg content, and the ratio of the flux that effectively acts in brazing is increased to increase the fin joint rate. It is possible to improve the heat transfer performance and durability of the heat exchanger.

[0019]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 An aluminum alloy ingot having a composition shown in Table 1 was homogenized, hot-rolled, cold-rolled, intermediately annealed, and finish-cold-rolled according to a conventional method to obtain a fin material having a thickness of 0.07 mm. After applying the fluoride flux (concentration 1%) to the obtained fin material, heat it at 600 ° C for 3 minutes in the same condition as brazing, that is, in a nitrogen gas atmosphere. A tensile test was performed.

The thermal conductivity of the test material after heating was evaluated by measuring the electrical conductivity at 25 ° C. In the fin material of the present invention, similarly to general metal materials, it is recognized that there is a proportional relationship between thermal conductivity and electrical conductivity, and that thermal conductivity can be evaluated by measuring electrical conductivity. I have. Further, in order to evaluate the sacrificial anode effect, 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.

Next, the fin material is subjected to corrugation, and a core material of Al-1.2% Mn-0.5% Cu alloy is used.
Placed on a 0.4 mm thick plate material with the alloy as a skin material (brazing material), and performing a flux flux brazing,
Investigate the percentage of the brazing joint between the corrugated fin material and the plate material, evaluate the brazing properties from the fin joining rate,
The CASS test for the joint between the fin and the plate
The test was conducted for one month based on H8681 to measure the maximum corrosion depth of the plate and to observe the corrosion state of the fin. The rate of change in fin height before and after brazing was measured to evaluate the fin's high-temperature buckling resistance. Table 2 shows the test, measurement, and evaluation results.

[0022]

[Table 1]

[0023]

[Table 2] << Table Note >> High temperature buckling resistance: ◎: less than 4.0% change in fin height before and after brazing; ○: 4.0 to 8.0%

As shown in Table 2, all of the test materials No. 1 to No. 11 according to the present invention have excellent tensile strengths equivalent to 120 MPa or more after brazing. The electric conductivity of conventional JIS 3005 fin material is 36% IA
In all cases, the electrical conductivity was 40% IACS or more, whereas the CS was CS, indicating that the thermal conductivity was good. The fin bonding ratio was 98% or more, indicating that the brazing property was excellent. The natural electrode potential is also in the range of -730 to -745 mV vs SCE,
Plate core alloy (Mn 1.2%, Cu 0.5%, balance Al
And the impurity) have a base potential of at least 50 mV with respect to the natural potential of -675 mV. The maximum corrosion depth of the plate after the CASS test is as shallow as 0.13 to 0.19 mm, indicating that the fin has an excellent sacrificial anode effect. Admitted.

Comparative Example An aluminum alloy ingot having a composition shown in Table 3 was homogenized, hot rolled, cold rolled, intermediately annealed and finish cold rolled under the same conditions as in Example 1 to obtain a 0.07 mm thickness. Fin material was obtained. For the obtained fin material, the tensile strength, electric conductivity, and natural electrode potential were measured, and the high-temperature buckling resistance and brazing resistance of the fin material were evaluated. The maximum corrosion depth after the CASS test was measured. Table 4 shows the results.

[0026]

[Table 3]

[0027]

[Table 4] << Table Note >> High temperature buckling resistance: ◎: less than 4.0% change in fin height before and after brazing; ○: 4.0 to 8.0%

As shown in Table 4, none of the aluminum alloy fins satisfying the conditions of the present invention has sufficient performance as heat exchanger fins. Test material No.1
In the case of 2, the tensile strength is not sufficient because the content of Mn is small, and the solid solubility of Si increases because the (Mn / Si) ratio is small, the electrical conductivity decreases, and the thermal conductivity is insufficient. It became. In No. 13, since the Mn content was too large, hot rolling was difficult and a sound fin material could not be produced.

Test material No. 14 had a low Si content and thus had insufficient tensile strength, and a large (Mn / Si) ratio, which increased the solid solution amount of Mn and increased the electrical conductivity. As the thermal conductivity becomes insufficient, the natural potential becomes noble, the potential difference from the plate is insufficient, and the sacrificial anode effect is inferior, so the corrosion depth of the plate material after the CASS test is 0.
29mm deep. In No. 15, since the content of Si was too large, local melting of the fin material occurred during heating during brazing. No.16, No.17, No.18 and No.19 have a high Mg content, so their brazing properties are inferior, the joining ratio of the fins is low, and when incorporated into a heat exchanger, Thermal properties are degraded.

No. 17, No. 18 and No. 19 are JIS
Corresponds to 3203, 3003, and 3005 alloy materials, all of which have a high Cu content, and the natural potential is noble, the potential difference with the plate material is insufficient, and the sacrificial anode effect is inferior, and the corrosion depth after the CASS test Is getting bigger. In addition, No. 19 had insufficient tensile strength due to low Si content, and (Mn / S
i) Since the ratio was large, the amount of solid solution of Mn was increased and the electric conductivity was lowered, and the heat conductivity became insufficient. No.20
, No. 21 each had a large content of Zr and Cr, so that hot rolling was difficult and a sound fin material could not be produced.

[0031]

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

Claims (2)

[Claims] 1. An alloy containing Mn 0.8 to 2.0% (mass%, the same applies hereinafter) and Si 0.4 to 1.3%, wherein the ratio of Mn content to Si content (Mn / Si) is 1.0 to 3.5, Limiting Mg as an impurity to less than 0.01% and Cu to less than 0.02%,
A high-strength aluminum alloy fin material for heat exchangers having excellent brazing properties, comprising a balance of Al and unavoidable impurities. 2. Mn content: 0.8 to 2.0% of Mn, 0.4 to 1.3% of Si, and one or two of 0.06 to 0.25% of Zr and 0.06 to 0.25% of Cr. And the content of Si and Si content (Mn / Si) is set to 1.0 to 3.5, Mg as an impurity is limited to less than 0.01%, Cu is limited to less than 0.02%, and the balance consists of Al and unavoidable impurities. High strength aluminum alloy fin material for heat exchangers with excellent attachment properties.