JP6617012B2 - Aluminum alloy fin material for heat exchangers excellent in strength, conductivity and brazing properties, and heat exchanger provided with the aluminum alloy fin materials for heat exchangers - Google Patents

Description

The present invention is strength for use in automobile heat exchanger, conductive, it relates to a heat exchanger comprising an aluminum alloy fin material contact and heat exchange aluminum alloy fin material excellent in brazeability.

  The fin material for automobile heat exchangers is required to have high strength, high conductivity and brazing after brazing. However, since these characteristics are in a trade-off relationship, it is conventionally difficult to satisfy all the characteristics. In the past, for example, Patent Document 1 and Patent Document 2 have proposed fin materials having excellent strength and conductivity after brazing. The fin material proposed in Patent Document 1 and Patent Document 2 has a very fast slab cooling rate at the time of casting, such as several tens of degrees centigrade / s or more, and a continuous casting rolling method (CC method) in which a thin plate is directly produced from a molten metal. It is produced by a manufacturing method based on the above.

On the other hand, for example, a fin material using a semi-continuous casting method (DC method) with a slab cooling rate of 10 ° C./s or less at the time of casting cannot obtain a fine crystallization product as continuous casting at the time of casting. The object size tends to be coarsened to 1 μm or more. In this case, the coarse crystallized material present in the material becomes a recrystallization nucleation site during the heat of brazing, so that the crystal grains are easily refined, and the wax erosion from the crystal grain boundary is likely to occur. Inferiority.
Further, in the semi-continuous casting method, a heat treatment at a high temperature of about 500 ° C. generally called a homogenization treatment is applied for the purpose of homogenizing segregation of the ingot obtained by casting. Furthermore, a soaking treatment at 500 ° C. or higher is essential before hot rolling in order to reduce deformation resistance during cracking and to suppress the occurrence of cracks.

JP 2008-038166 A JP 2001-335901 A JP 2012-26008 A

However, due to the heat treatment applied to the material by the DC method, precipitation of additive elements dissolved in supersaturation at the time of casting occurs, but when the heat treatment temperature is higher than 500 ° C., the second phase particles are likely to be coarsened and the strength is reduced. The impact on the environment is inevitable.
As described above, in the DC method which is the most general casting method, it is difficult to achieve both high strength, high conductivity, and brazability.
For example, in Patent Document 3, high strength and high electrical conductivity after brazing are defined in Patent Document 3 by defining the composition ratio of Mn, Si, and Fe, the type of intermetallic compound, and the dispersion state. A fin material that achieves the above has been proposed. However, although these fin materials have a high conductivity after brazing of about 48% IACS, the strength after brazing is only about 130 MPa, which is not a sufficient characteristic.

  The present invention has been made against the background of the above circumstances, and the aluminum alloy fin has further improved strength and brazeability by crystal grain coarsening while ensuring a conductivity of 42% IACS or higher after brazing. An object is to provide a material and a heat exchanger.

Here, as the aluminum strengthening mechanism, “solid solution strengthening” with additive elements, “precipitation strengthening” in which a large number of extremely fine hard particles are dispersed by heat treatment, and “crystal grain refinement strengthening” in which crystal grains are refined are common. Can be considered. However, solid solution strengthening causes a decrease in electrical conductivity, and crystal grain refinement strengthening has a problem of causing a decrease in brazing. In the present invention, attention is paid to “precipitation strengthening” as a strengthening mechanism. "Precipitation strengthening" contributes to strength improvement by the fact that fine second-phase particles become a strong obstacle to dislocations, and the solid solubility of the additive elements decreases, so the specific resistance decreases and the conductivity improves. . In addition, these fine second-phase particles are less likely to become nucleation sites for recrystallization, and also have the effect of delaying recrystallization and coarsening by suppressing the dislocation during recrystallization and the moving speed of grain boundaries.
“Homogenization treatment” during the manufacturing process in the semi-continuous casting method (DC method) and “soaking treatment before hot rolling” in order to obtain the ideal dispersion state of the second phase particles in order to make the most of these precipitation strengthening ”.

  In other words, the present invention focuses on the dispersion state of fine intermetallic compounds in the material and precipitates by stably presenting fine, dense second-phase particles that have never existed with the optimum chemical composition and optimum production process. Achieved high levels of strengthening by strengthening, high conductivity by reducing the amount of solid solution, and coarsening of grains by fine precipitation. Until now, semi-continuous casting methods could not be achieved only by optimizing chemical components. A fin material excellent in strength, conductivity, and brazing properties has been obtained.

That is, among the aluminum alloy fin materials for heat exchangers of the present invention, the first present invention is mass%, Mn: 1.2 to 2.0%, Cu: 0.05 to 0.20%, Si: 0.5 to 1.30%, Fe: 0.05 to 0.5%, Zn: 1.0 to 3.0%, and the balance is made of an aluminum alloy having a composition composed of Al and inevitable impurities. The temperature rises from room temperature to 600 ° C. at an average rate of temperature increase of 40 ° C./min, is held at 600 ° C. for 3 minutes, and is cooled at a rate of temperature decrease of 100 ° C./min. It is characterized by 140 MPa or more, proof stress 50 MPa or more, conductivity 42% IACS or more, average crystal grain size 150 μm or more and less than 700 μm, and potential −800 mV or more and −720 mV or less.

  The aluminum alloy fin material for a heat exchanger according to the second aspect of the present invention is the aluminum alloy fin material according to the first aspect of the present invention, wherein the aluminum alloy is further in mass%, Ti: 0.01 to 0.20%, Cr: 0.01 It is characterized by containing 1 type (s) or 2 or more types among -0.20% and Mg: 0.01-0.20%.

The aluminum alloy fin material for a heat exchanger according to the third aspect of the present invention has a tensile strength of 90 MPa or more and a proof stress of 40 MPa or more at a high temperature strength at 115 ° C. after the heat treatment in the first or second aspect of the present invention. It is characterized by that.

The aluminum alloy fin material for a heat exchanger according to a fourth aspect of the present invention is the material according to any one of the first to third aspects, wherein the electrical conductivity before brazing is 45% IACS or more, and the equivalent circle diameter before brazing. Al-Mn-based, Al-Mn-Si-based and Al-Fe-Si-based crystals having a crystallized size of 1.0 μm or more and less than 5.0 × 10 ⁴ pieces / mm ² and 0.01 to 0.10 μm Two-phase particles are present at 5.0 × 10 ⁴ particles / mm ² or more.

An aluminum alloy fin material for a heat exchanger according to a fifth aspect of the present invention is the Al-Mn type Al or Mn-based alloy having an equivalent circle diameter of 0.01 to 0.10 μm after the heat treatment in any of the first to fourth aspects of the present invention. -Mn-Si-based and Al-Fe-Si-based second phase particles are present at 1.0 × 10 ⁴ particles / mm ² or more.

  The aluminum alloy fin material for heat exchangers of the sixth aspect of the present invention is characterized in that, in any of the first to fifth aspects of the present invention, the plate thickness is 80 μm or less.

The aluminum alloy fin material for a heat exchanger according to a seventh aspect of the present invention is the aluminum alloy fin material for a heat exchanger according to any one of the first to sixth aspects, wherein the temperature range from the start to the end of recrystallization with respect to brazing addition heat is 350 ° C to 550 ° C. Ah is, proof stress is the recrystallization starting temperature the temperature begins to decrease more than 20% from the previous brazing strength, recrystallization completion temperature begins to decrease until the proof stress value + 20% within compared to proof stress after heating brazing Assuming that the brazing heat is a brazing heat, the temperature is raised from room temperature to 600 ° C. at a constant rate of 100 ° C./min. After reaching the temperature, the brazing heat is cooled to room temperature .

A heat exchanger according to an eighth aspect of the present invention includes the aluminum alloy fin material for a heat exchanger according to any one of the first to seventh aspects of the present invention.

  Below, the reason for limitation of the composition etc. prescribed | regulated by this invention is demonstrated. In addition, all content of each component in the following is shown by the mass%.

Mn: 1.2 to 2.0%
Mn is included for precipitating an Al— (Mn, Fe) —Si intermetallic compound and obtaining strength after brazing by dispersion strengthening. However, if it is less than 1.2%, the effect of dispersion strengthening by the Al— (Mn, Fe) —Si intermetallic compound is small, and the desired strength after brazing cannot be obtained. On the other hand, if it exceeds 2.0%, the solid solution amount of Mn becomes large, and the desired conductivity after brazing cannot be obtained, so that the thermal conductivity is inferior. Moreover, the Al- (Mn, Fe) -based coarse intermetallic compound increases, and the cutting processability at the time of fin forming deteriorates. For the same reason, it is desirable to set the lower limit to 1.5% and the upper limit to 1.8%.

Cu: 0.05-0.20%
Cu forms an intermetallic compound, and the strength is improved by dispersion strengthening and solid solution strengthening. However, when the content is less than 0.05%, the influence on dispersion strengthening and solid solution strengthening is small, and the effect of improving the strength is small. On the other hand, if the Cu content exceeds 0.20%, the solid solubility in the matrix increases, the conductivity after brazing decreases, the thermal conductivity decreases, and the corrosion resistance of the fin alone decreases. For the same reason, it is desirable that the lower limit is 0.06% and the upper limit is 0.15%.

Si: 0.5-1.30%
Si is added to precipitate an Al— (Mn, Fe) —Si intermetallic compound and obtain strength after brazing by dispersion strengthening. However, if the content is less than 0.5%, the effect of dispersion strengthening by the Al— (Mn, Fe) —Si intermetallic compound is small, and the desired strength after brazing cannot be obtained. On the other hand, when the content exceeds 1.30%, the solid solution amount of Si increases, and the desired conductivity after brazing cannot be obtained, so that the thermal conductivity is inferior. Moreover, since the solid solution amount of Si is increased, the solidus temperature (melting point) is lowered, and remarkable brazing erosion is likely to occur during brazing. For the same reason, it is desirable to set the lower limit to 0.7% and the upper limit to 1.2%.

Fe: 0.05 to 0.5%
Fe is added to precipitate Al— (Mn, Fe) —Si and Al— (Mn, Fe) intermetallic compounds and obtain strength after brazing by dispersion strengthening. However, if the content is less than 0.05%, the effect of dispersion strengthening by Al- (Mn, Fe) -Si and Al- (Mn, Fe) intermetallic compounds is small, and the desired strength after brazing can be obtained. Absent. In addition, the proportion of Al-Mn-Si-based fine intermetallic compounds is relatively increased, and these are liable to be re-dissolved during brazing at about 600 ° C., so that the conductivity after brazing is lowered and heat conduction Sex is reduced. On the other hand, if the content exceeds 0.5%, the crystallized product at the time of casting becomes coarse, and the productivity (rollability) decreases. In addition, since the intermetallic compound is coarsened, mold wear during fin molding is greatly reduced. For the same reason, it is desirable to set the lower limit to 0.10% and the upper limit to 0.35%.

Zn: 1.0-3.0%
Zn has an effect of lowering the potential of the aluminum alloy, and is contained in order to obtain a sacrificial anode effect. However, if the content is less than 1.0%, the potential is not sufficiently low, so that the desired sacrificial anode effect cannot be obtained, and the corrosion depth of the combined tube increases. On the other hand, if the content exceeds 3.0%, the potential becomes excessively low, and the corrosion resistance of the fin alone is lowered. For the same reason, it is desirable to set the lower limit to 1.2% and the upper limit to 2.2%.

One or more of Ti: 0.01-0.20%, Cr: 0.01-0.20%, Mg: 0.01-0.20% Ti, Cr, Mg are intermetallic compounds Since the strength is improved by dispersion strengthening and solid solution strengthening, one or more are optionally contained. However, when the content is less than the lower limit, the influence on dispersion strengthening and solid solution strengthening is small, and the effect of improving the strength is small. When Ti and Cr exceed the respective upper limits, the crystallized product at the time of casting becomes coarse, and the productivity decreases. Moreover, Mg will reduce brazing property, if it exceeds an upper limit.
Therefore, the respective contents are determined within the above ranges. For the same reason, Ti, Cr, Mg: It is desirable to set the lower limit to 0.03% and the upper limit to 0.15%.

Tensile strength after brazing is 140 MPa or more With the thinning of members, high strength materials are required. If the strength of the fin material after brazing is low, fin breakage is likely to occur due to repeated vibration applied to the heat exchanger when mounted on the vehicle and expansion and compression of cooling water. In such a broken portion, the effect of suppressing the tube expansion and compression of the fin cannot be obtained, and the tube expands like a drum, leading to early breakage, that is, leakage of internal cooling water. In the past results, it has been found that even when the fin plate thickness is 80 μm or less, if the tensile strength after brazing is 140 MPa or more, fin breakage in the market can be greatly reduced.

The yield strength after brazing is 50MPa or more. The yield strength indicates the elastic limit. If the yield strength after brazing is low, the original shape is retained by plastic deformation due to repeated vibration when mounted on the vehicle, even if the fin does not break. However, the core contraction is caused by the deformation of the fins in a plurality of stages. It has been found that even when the fin plate thickness is 80 μm or less, the influence can be reduced if the proof stress after brazing is 50 MPa or more.

Conductivity after brazing is 42% IACS or more In order to ensure the desired thermal conductivity, the conductivity after brazing is 42% IACS or more.

If the average crystal grain size after brazing is 150 μm or more and less than 700 μm, the average crystal grain size after brazing is less than 150 μm, and if it is fine, braze erosion (erosion) occurs through the crystal grain boundary and fin buckling is likely to occur. Become. On the other hand, when the average crystal grain size is coarse and is 700 μm or more, the influence on the yield strength is increased due to the so-called Hall Petch relationship. In particular, in the case of a thin-walled material, it is necessary to set the optimum crystal grain size range in consideration of brazability and high strength.

The potential after brazing is -800 mV or more and -720 mV or less. When the potential of the fin material is less than -800 mV, the potential of the fin member is excessively low (low) with respect to other members to be joined. It will accelerate. When the potential of the fin exceeds -720 mV, the potential is not sufficiently low (low) with respect to the other members to be joined, so the sacrificial anode effect cannot be obtained, and for example, corrosion of the tube material is accelerated.

Plate thickness of 80 μm or less In order to achieve weight reduction, the fin material plate thickness is desirably 80 μm or less, and the effect of improving the strength becomes remarkable. The lower limit is 25 μm.

At high temperature strength at 115 ° C. after brazing, the tensile strength is 90 MPa or more and the proof stress is 40 MPa or more. Heat exchangers such as radiators rise to a maximum of about 115 ° C. when used in the market. Since the material strength of the aluminum member decreases as the temperature increases, the strength level at a high temperature is also important in an actual environment. Even if the normal temperature strength after brazing is high, the effect is halved if the high temperature strength is low.

Conductivity before brazing is 45% or more IACS (International Annealed Copper Standard) The solid solubility of each additive element in the present invention is high even in the state before brazing. Will increase. The higher the solid solubility, the lower the electrical conductivity. Therefore, if the electrical conductivity of the aluminum alloy fin material before brazing is less than 45% IACS, the desired electrical conductivity after brazing cannot be ensured. Conductivity cannot be secured. Moreover, when the electrical conductivity before brazing is less than 45% IACS, the amount of precipitation of each additive element is small, so the effect of dispersion strengthening by each compound is small, and the desired strength after brazing cannot be obtained. For the same reason, it is desirable to set the lower limit to 48% IACS. The upper limit is actually 58% IACS.

Al-Mn-based and Al-Mn-Si-based crystals having an equivalent circle diameter of 1.0 μm or more before brazing are less than 5.0 × 10 ⁴ pieces / mm ² and 0.01 to 0.10 μm, Al × Fe—Si second phase particles are 5.0 × 10 ⁴ particles / mm ² or more. The dispersion state of the intermetallic compound before brazing largely affects the recrystallization behavior during brazing. If there is a large proportion of coarse crystals with an equivalent circle diameter of 1.0 μm or more, they become nucleation sites for recrystallization, which promotes recrystallization during brazing and makes the crystal grain size finer. Adhesivity is reduced). On the other hand, fine second-phase particles with an equivalent circle diameter of 0.01 to 0.10 μm suppress the transition to the recrystallization site and the accumulation of subgrain boundaries, so the recrystallization is delayed and the crystal grains become coarse (Brassability is improved).

Recrystallization temperature (350-550 ° C)
The recrystallization temperature range in the brazing heat greatly affects the brazing property of the fin. In general, the brazing heat is performed in a temperature range around 600 ° C., but in the temperature rising process from room temperature, the temperature rising rate is large on the low temperature side below 350 ° C. descend. Here, since the rate of temperature increase is large in the former temperature range, a temperature difference occurs between each member of the heat exchanger, thin-walled fins that tend to rise in actual temperature expand, and thermal stress is generated between the fins and the tube. To do. Further, if the recrystallization of the fin proceeds in this temperature range, the strength of the fin is lowered, and there is a problem that a brazing failure is likely to occur due to buckling without being able to withstand the thermal stress. Therefore, it is desirable that the recrystallization start temperature at the time of brazing addition heat be 350 ° C. or higher. On the other hand, when the recrystallization end temperature is 550 ° C. or higher, the sag property is greatly reduced due to the change in structure during recrystallization and the increase in high temperature creep. Therefore, it is desirable that the recrystallization temperature range during brazing addition heat is 350 ° C. to 550 ° C.
The recrystallization start temperature is a temperature at which the proof stress value starts to decrease by 20% or more compared to that before brazing (raw material), and the end temperature is the proof stress value that starts to decrease to within + 20% compared to after the brazing addition heat. Defined as temperature.

More than 1.0 × 10 ⁴ / mm ^{2 of} Al—Mn, Al—Mn—Si, and Al—Fe—Si second phase particles having an equivalent circle diameter of 0.01 to 0.10 μm after brazing heat The dispersion state of the intermetallic compound after brazing largely affects the material strength. Precipitation strengthening by fine second phase particles having an equivalent circle diameter of 0.01 to 0.10 μm can be expected.

Homogenization treatment at a treatment temperature of 350 ° C. to 480 ° C. and a treatment time of 1 to 10 hours By the treatment under predetermined conditions, an ideal dispersion state of each intermetallic compound is uniformly obtained in a matrix. When the temperature is lower than the above range or for a short time, it is not preferable because sufficient precipitation does not proceed in the homogenization treatment and non-uniform precipitation proceeds in the subsequent heat treatment step. Further, on the high temperature side or the long time side from the above range, the second phase particles are easily coarsened, and a desired dispersed state of the intermetallic compound cannot be obtained.

The soaking process before hot rolling is carried out at a temperature equal to or lower than the homogenization temperature and processing time. By the treatment under predetermined conditions, an ideal dispersion state of each intermetallic compound can be obtained uniformly in the matrix. As a result, the alloy of this component range can achieve characteristics excellent in strength, conductivity and brazing. It was found that when the temperature and time of soaking are higher and longer than the homogenization treatment, the dispersion state of the intermetallic compound obtained by the homogenization treatment cannot be maintained due to the influence of the subsequent soaking treatment.

  As described above, the aluminum alloy fin material for heat exchanger of the present invention is in mass%, Mn: 1.2 to 2.0%, Cu: 0.05 to 0.20%, Si: 0.5 to 1.30%, Fe: 0.05-0.5%, Zn: 1.0-3.0%, the balance is made of an aluminum alloy having a composition consisting of Al and inevitable impurities, and heat of brazing addition Later tensile strength is 140 MPa or more, yield strength is 50 MPa or more, conductivity is 42% IACS or more, average crystal grain size is 150 μm or more and less than 700 μm, electric potential is −800 mV or more and −720 mV or less, semi-continuous casting method (DC method) ), It has properties excellent in strength, conductivity and brazing.

Hereinafter, an embodiment of the present invention will be described.
The fin material of the present invention can be produced by, for example, a conventional method, and is prepared to the composition of the present invention to melt an aluminum alloy. The melting can be performed by a semi-continuous casting method. The obtained aluminum alloy ingot is homogenized under predetermined conditions. That is, the homogenization treatment conditions are a treatment temperature of 350 ° C. to 480 ° C. and a treatment time of 1 to 10 hours. Thereafter, a fin material (test material) of grade H14 can be obtained with a plate thickness of 80 μm or less through soaking, hot rolling, cold rolling and the like. The soaking is preferably performed at a temperature equal to or lower than the temperature and processing time of the homogenization treatment, and a temperature of 350 to 480 ° C. and a holding time of 1 to 10 hours. In cold rolling, cold rolling can be performed at 75% or more, intermediate annealing can be performed at a temperature of 300 to 400 ° C., and then final rolling at a rolling rate of 20 to 45% can be performed. The intermediate annealing may not be performed.

  Thereafter, the fin material obtained by the cold rolling or the like can be subjected to corrugating or the like as necessary. The corrugating process can be performed by passing between two rotating molds, can be processed satisfactorily, and exhibits excellent formability.

The fin material obtained above is used for brazing as a constituent member of a heat exchanger in combination with other constituent members (tube, header, etc.). The conditions for brazing (such as brazing temperature, atmosphere, presence / absence of use of flux, type of brazing material, etc.) are not particularly limited, and can be performed by conventional methods.
The heat exchanger produced above is used for applications such as automobiles. Since the fin part of the heat exchanger uses the fin material obtained as described above, the fin part has high strength and high thermal conductivity while being thinned.

Hereinafter, an embodiment of the present invention will be described in comparison with a comparative example.
An aluminum alloy brazing material having the composition shown in Table 1 (the balance Al + inevitable impurities) was melted and cast by a semi-continuous casting method. In addition, the cooling rate of slag was 0.5-3.5 degree-C / sec. Furthermore, the obtained ingot was homogenized under the conditions shown in Table 2 (the heating rate was 25 to 75 ° C./hour and the cooling rate was 20 to 50 ° C./hour). Then, soaking was performed under the conditions shown in Table 2 (temperature increase rate was 25 to 75 ° C./hour, cooling rate was 20 to 50 ° C./hour), and processing was performed in the order of hot rolling and cold rolling. Went.

  In the cold rolling process, after cold rolling at 75% or more, intermediate annealing is performed at 350 ° C. for 6 hours, and then final rolling at a rolling rate of 40% is performed. A plate material (test material) was obtained. About the obtained test material, the number density | concentration of the crystallized substance with an equivalent circle diameter of 1.0 micrometer or more and second phase particle | grains with an equivalent circle diameter of 0.01-0.10 micrometer was obtained by the method shown below. Calculated and shown in Table 2. Also, brazing equivalent heating is performed under the following conditions, and the heated fin material is subjected to tensile strength, yield strength, conductivity, crystal grain size, potential, high temperature tensile strength, high temperature yield strength, and circle by the following methods. The number density of the second phase particles having an equivalent diameter of 0.01 to 0.10 μm was evaluated.

(Brazing process)
The temperature was increased from room temperature to 600 ° C. at an average temperature increase rate of 40 ° C./min, held at 600 ° C. for 3 minutes, and then subjected to brazing equivalent heating under the conditions of heat treatment for cooling at a temperature decrease rate of 100 ° C./min.

(conductivity)
Before and after brazing, it was measured with a double-bridge type conductivity meter according to the conductivity measuring method described in JIS H-0505.

(Distribution state of material compounds)
For the specimens before and after brazing, the number density (pieces / μm ² ) of crystallized matter (equivalent circle diameter is 1.0 μm or more) and second phase particles (equivalent circle diameter is 0.01 to 0.10 μm). It was measured with a transmission electron microscope (TEM). Before brazing, the material is subjected to salt bath annealing at 400 ° C for 15 seconds to remove deformation strain and make it easy to observe the compound. Then, a thin film is prepared by mechanical polishing and electrolytic polishing by ordinary methods. The crystallized product was photographed at 3000 times and the second phase particles were photographed at 30000 times with a transmission electron microscope. For 3000 times, one field of view was 50 μm × 50 μm, 50 fields in total, and for 30000 times, 1 field of view was 5 μm × 5 μm, 5 fields in total, and the size and number density of dispersed particles were measured by image analysis.

(Recrystallization temperature)
Assuming brazing heat, the temperature was raised from room temperature to ˜600 ° C. at a constant rate of 100 ° C./min, and after reaching each temperature, it was cooled to room temperature. Thereafter, a JIS No. 5 test piece was prepared, a tensile test was performed, and the proof stress was measured. The tensile speed was 15 mm / min. The temperature at which the proof stress value starts to decrease by 20% or more compared to the proof stress before brazing is defined as the recrystallization start temperature, and the temperature at which the proof stress value starts to decrease to within + 20% relative to the proof stress after brazing addition heat is defined as the recrystallization end temperature. It is shown in Table 2.

(Strength after brazing)
A sample was cut out in parallel to the rolling direction on a specimen subjected to brazing equivalent heating to produce a JIS13B-shaped test piece, a tensile test was performed at room temperature, and tensile strength and proof stress were measured. The tensile speed was 3 mm / min. Similarly, the high temperature strength was subjected to a tensile test and a proof stress at a test temperature of 115 ° C. using the brazed sample. The tensile speed during the high temperature tensile test was 1 mm / min.

(Natural potential)
A sample for potential measurement was cut out from the fin material subjected to brazing equivalent heat treatment, immersed in a 5% NaOH solution heated to 50 ° C. for 30 seconds, then immersed in a 30% HNO ₃ solution for 60 seconds, and tap water, After washing with ion-exchanged water and without drying, the natural potential after immersion for 60 min in a 5% NaCl solution (adjusted to pH 3 with acetic acid) at 25 ° C. (the reference electrode was a silver-silver chloride electrode (saturated)) was measured. .

(Crystal grain size)
For specimens that have undergone heat treatment equivalent to brazing, the surface of the sample is exposed by etching the sample surface with a mixed solution of hydrochloric acid, hydrofluoric acid, and nitric acid. The crystal grain size was measured by the method.

  The examples of the present invention all showed high strength, high conductivity, and high brazeability as compared with the comparative example, whereas the comparative examples showed all of high strength, high conductivity, and high brazeability. I couldn't meet. In Comparative Example 2, the fin material could not be manufactured, and in Comparative Example 4, when the brazing equivalent heating was performed, it was locally dissolved and could not be evaluated.

  Although the present invention has been described based on the above embodiments and examples, appropriate modifications can be made to the above embodiments and examples without departing from the scope of the present invention.

Claims (8)

In mass%, Mn: 1.2 to 2.0%, Cu: 0.05 to 0.20%, Si: 0.5 to 1.30%, Fe: 0.05 to 0.5%, Zn: 1.0 to 3.0%, and the balance is made of an aluminum alloy having a composition composed of Al and inevitable impurities. The temperature is increased from room temperature to 600 ° C. at an average temperature increase rate of 40 ° C./min. After a heat treatment equivalent to brazing in which the temperature is lowered at a rate of 100 ° C./min after holding for 3 minutes, the tensile strength is 140 MPa or more, the proof stress is 50 MPa or more, the conductivity is 42% IACS or more, and the average crystal grain size is 150 μm. An aluminum alloy fin material for a heat exchanger that is excellent in strength, conductivity, and brazeability, characterized by being less than 700 μm and a potential of −800 mV to −720 mV.   Further, the aluminum alloy may be one or two of Ti: 0.01 to 0.20%, Cr: 0.01 to 0.20%, Mg: 0.01 to 0.20% by mass%. The aluminum alloy fin material for heat exchangers having excellent strength, electrical conductivity, and brazing properties according to claim 1, comprising at least a seed. The high temperature strength at 115 ° C. after the heat treatment has a tensile strength of 90 MPa or more and a proof stress of 40 MPa or more. Aluminum alloy fin material. The electrical conductivity before brazing is 45% IACS or more, and the crystallized product having an equivalent circle diameter of 1.0 μm or more before brazing is less than 5.0 × 10 ⁴ pieces / mm ² and 0.01 to 0.00. The Al-Mn-based, Al-Mn-Si-based, and Al-Fe-Si-based second phase particles of 10 µm are present in an amount of 5.0 x 10 ⁴ particles / mm ² or more. The aluminum alloy fin material for heat exchangers excellent in strength, conductivity and brazing properties according to claim 1. After the heat treatment , there are 1.0 × 10 ⁴ particles / mm ² or more of Al—Mn, Al—Mn—Si, and Al—Fe—Si second phase particles having an equivalent circle diameter of 0.01 to 0.10 μm. The aluminum alloy fin material for heat exchangers according to any one of claims 1 to 4, which is excellent in strength, conductivity, and brazeability.   The aluminum alloy fin material for heat exchangers according to any one of claims 1 to 5, wherein the plate thickness is 80 µm or less, and the strength, conductivity, and brazing properties are excellent. Temperature range 350 ° C. to 550 ° C. der from the start to the end of the recrystallization for brazing heat is, proof stress is the recrystallization starting temperature the temperature begins to decrease more than 20% from the previous brazing strength, brazing The temperature at which the proof stress value starts to drop to within + 20% compared to the proof stress after heating is defined as the recrystallization end temperature, and the brazing heat is assumed to be brazing heat, at a constant rate of 100 ° C / min from normal temperature to 600 ° C. The aluminum alloy fin material for heat exchangers according to any one of claims 1 to 6, wherein the aluminum alloy fin material is excellent in strength, conductivity, and brazing properties , wherein the temperature is increased and the temperature is reached and then cooled to room temperature. .   A heat exchanger comprising the aluminum alloy fin material for a heat exchanger according to claim 1.