JP2005139505A - Aluminum alloy fin material, and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy fin material which has excellent self-corrosion resistance while maintaining high strength and electroconductivity after brazing under heating. <P>SOLUTION: In the aluminum alloy fin material, the ratio between the numerical density N<SB>1</SB>of intermetallic compounds with a particle diameter of the equivalent sphere of ≥0.5 μm present in the region A of 1/20 to the sheet thickness from the surface and the numerical density N<SB>2</SB>of intermetallic compounds with a particle diameter of the equivalent sphere of ≥0.5 μm present outside of the region A, N<SB>2</SB>/N<SB>1</SB>, is ≥1.2, and also, the numerical density N<SB>1</SB>of the intermetallic compounds with a particle diameter of the equivalent sphere of ≥0.5 μm present in the region A is ≥2×10<SP>4</SP>pieces/mm<SP>2</SP>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aluminum alloy fin material that is used in heat exchangers such as automobiles and electrical products, has high strength and high thermal conductivity, and has excellent self-corrosion resistance, and a method for producing the same.

  In recent years, aluminum alloys are used for automobile heat exchangers because they are lightweight and have high thermal conductivity. Automotive heat exchangers are mainly manufactured by the brazing method. Usually, brazing is performed at a high temperature of about 600 ° C. using an Al—Si brazing material. Accordingly, there is a need for an aluminum alloy that has high strength, thermal conductivity, and corrosion resistance after brazing.

Aluminum alloy heat exchangers manufactured using brazing are mainly composed of corrugated fins that play a role of heat dissipation and tubes that serve as passages for circulating cooling water and refrigerant. The fins are required to have excellent thermal conductivity in order to release the heat of cooling water and refrigerant flowing in the tube. Also, the fin material strength and the self-corrosion resistance for maintaining the strength of the heat exchanger are very important.
Conventionally, aluminum alloy fin materials used for heat exchangers for automobiles include pure aluminum alloys such as 1050 alloy excellent in thermal conductivity and Al-Mn alloys such as 3003 alloy excellent in strength and buckling resistance. (See, for example, Non-Patent Document 1).

  However, although a pure aluminum alloy is excellent in thermal conductivity, the strength is insufficient, and there arises a problem that fins are crushed when the heat exchanger core is assembled or when brazing is heated. In addition, Al-Mn alloys have improved strength by strengthening the solid solution of Mn, but this causes a decrease in thermal conductivity, lowers the heat exchange rate of the heat exchanger, and reduces its weight and size. Results in hindering.

  Furthermore, the fin plays a role of preventing the corrosion of the tube by the sacrificial anticorrosive action. Sacrificial corrosion protection means that by adding elements such as Zn, Sn, In, etc., the potential of the fin is made lower, a potential difference is established between the tube and the fin corrodes preferentially against the tube, corroding the tube. It is a way to protect from. However, if the corrosion resistance of the fin itself is low, the fin disappears quickly, and the tube cannot be protected by sacrificial protection, and not only the life of the heat exchanger is shortened, such as a hole in the tube, but also its strength and heat exchange rate Cannot be maintained.

  For the above reasons, a material excellent in properties such as strength, thermal conductivity, corrosion resistance and the like is desired for the fin material of the heat exchanger for automobiles. The casting method, the hunter method, the 3C method, etc., which have a fast cooling rate after casting. Fin materials having various compositions using a continuous casting method and manufacturing methods thereof have been proposed (for example, Patent Documents 1 to 5).

  In the continuous casting method, pressure is constantly applied between the molten metal and the mold by the casting roll, so that the thermal conductivity is extremely high, and the cooling rate at the time of casting is other casting methods such as the direct chill method (hereinafter referred to as DC method). Therefore, the microstructure of the slab or cast plate obtained is likely to be fine and uniform, and the aluminum alloy fin material obtained by rolling them is between finely and densely dispersed metals in the alloy. A compound is produced. With this finely dispersed intermetallic compound, an aluminum alloy fin material exhibiting high strength and thermal conductivity after brazing can be obtained (see, for example, Patent Documents 1 and 2).

In patent document 1, the fin material which consists of an Al-Mn-Fe-Si type alloy excellent in intensity | strength and heat conductivity by using the continuous casting rolling method which prescribed | regulated the cooling rate at the time of casting to 10-250 degreeC / sec. Has been proposed. Further, Patent Document 2, by using a continuous casting process, has been shown to be able to produce an aluminum alloy plate having a diameter there is 4μm or more crystallizate 20 / mm ² or more.

  In Patent Documents 3, 4, and 5, the intermetallic compound can be finely and uniformly dispersed in the fin material matrix by making the cooling rate during casting as very high as 15 to 1000 ° C./sec. Promotes the precipitation of solute Mn in the fin matrix and improves the electrical conductivity.

Japan Light Metal Association Aluminum Technical Handbook Editorial Committee, New Edition / Aluminum Technical Handbook, New Edition, Karos Publishing Co., Ltd., November 1996, p. 1063-1074, p. 1146 to 1150 Japanese translation of PCT publication No. 2002-521564 JP-A-9-78168 JP 2002-256402 A JP 2002-256403 A JP 2002-256364 A

  In the invention of Patent Document 1, in order to obtain the optimum combination of precipitation strengthening and solid solution strengthening, strip casting is performed at a high cooling rate, and the amount of Mn added is not reduced so as not to lower the thermal conductivity of the fin material after brazing addition heat. Is defined as 0.3 to 0.5 mass%. When the amount of Mn added is low, the amount of solid solution Mn in the parent phase is reduced, so that a decrease in thermal conductivity is suppressed. However, by reducing the amount of added Mn, a sufficient strengthening effect due to solid solution strengthening and precipitation strengthening cannot be obtained. In order to compensate for this decrease in strength, the crystal grain size of brazing is set to 30 to 80 μm. If the crystal grain size is fine, erosion erosion and droop resistance may be reduced due to diffusion of the brazing material.

  In the invention of Patent Document 2, Cr is added together with Fe in order to make crystal grains finer, and crystallized substances present in the plate material are coarsened. When the crystallized material is coarsened, the strength and conductivity of the resulting aluminum alloy plate are lowered. In addition, since the crystal grains are fine, when used as a fin material for an automobile heat exchanger, erosion erosion may occur due to diffusion of the brazing material during brazing heating.

  Further, the intermetallic compounds found in Patent Documents 3, 4, and 5 are likely to be corrosion starting points because the matrix around the intermetallic compound dissolves if the natural potential is more noble than the natural potential of the fin material matrix. . Furthermore, since the density is very large compared with the DC casting method with a slow cooling rate, the corrosion starting point is increased, and as a result, the self-corrosion resistance of the fin material is lowered.

  In view of these problems, an object of the present invention is to provide an aluminum alloy fin material having high strength and thermal conductivity and exhibiting excellent self-corrosion resistance.

The invention described in claim 1 is the number density N ₁ of the intermetallic compound having a sphere equivalent particle size of 0.5 μm or more existing in the region A 1/20 of the plate thickness from the surface of the aluminum alloy fin material, and other than the region A The ratio between the number density N ₂ of the intermetallic compound having a sphere equivalent particle size of 0.5 μm or more existing in the region of N ₂ / N ₁ is 1.2 or more, and the sphere equivalent particle size existing in the region A The aluminum alloy fin material is characterized in that the number density N ₁ of the intermetallic compound having a thickness of 0.5 μm or more is 2 × 10 ⁴ pieces / mm ² or more.

  The invention according to claim 2 is the aluminum alloy fin material according to claim 1, wherein the intermetallic compound is a crystallized product.

  The invention according to claim 3 is the aluminum alloy fin material, wherein the aluminum alloy fin material is manufactured from an ingot having 80% or more of a region having a dendrite secondary branch interval of 35 μm or less.

  The invention according to claim 4 is an ingot in which the ingot is cast to a thickness of 80 to 300 mm using a casting method including two-stage cooling of primary cooling by a mold and secondary cooling by cooling water. It is a manufacturing method of the aluminum alloy fin material characterized by being.

  The invention according to claim 5 is the method for producing an aluminum alloy fin material according to claim 4, wherein the casting method is a direct chill method.

  According to the present invention, the intermetallic compound existing in the fin material surface layer becomes coarse and sparse, and the intermetallic compound in the center can obtain a fine and dense aluminum alloy fin material. However, it is possible to provide an aluminum alloy fin material having high strength, high thermal conductivity, and excellent corrosion resistance, and has an industrially significant effect.

The present inventors have conducted research to solve the above-mentioned problems, and have found that the presence of a crystallized product composed of an intermetallic compound in the fin material greatly affects the self-corrosion resistance of the fin material.
That is, when a crystallized product of an intermetallic compound is present in the fin material, a potential difference is generated between the crystallized product and the fin material matrix, and the fin material matrix around the crystallized material is dissolved. That is, when the number density of crystallized substances (hereinafter referred to as crystallized substance density) is large, the number of corrosion starting points increases and the self-corrosion resistance of the fin material decreases. Therefore, in order to improve the self-corrosion resistance of the fin material, it is necessary to reduce the crystallized substance density.
This crystallized density greatly depends on the cooling rate at the time of casting, and when the cooling rate is high, the cast structure becomes fine and the crystallized product tends to become fine. On the other hand, if the cooling rate is slow, the cast structure becomes coarse and the crystallized product tends to become coarse.

Therefore, it is important to control the cooling rate, and in order to improve the self-corrosion resistance, it is necessary to use a casting method with a low cooling rate to reduce the crystallized density. However, when the crystallized density is reduced, both strength and thermal conductivity are lowered.
Therefore, the inventors of the present invention, as an aluminum alloy fin material having high strength, good thermal conductivity, and excellent self-corrosion resistance, the surface layer is composed of a phase with a low crystallized density, and the inside has a high crystallized density. The present inventors have found an aluminum alloy fin material composed of phases.

  In order to produce a fin material having a low crystallized surface density and a large internal crystallized density according to the present invention, in the casting process, when the molten metal is solidified, primary cooling with a mold and secondary cooling with cooling water are performed. The desired ingot can be obtained by using a casting method having the two-stage cooling, and can be easily achieved particularly by using the DC method.

The cooling method such as the DC method is not found in other casting methods, and due to the two-stage cooling unique to this DC method, the surface layer has a slower cooling rate during casting than the surroundings, so that the coarse cell layer becomes the surface layer. Generate. This coarse cell layer can make the crystallized material density of a fin material surface layer lower than the inside of a fin material.
Furthermore, the ingot thickness inside fin material is raised by making the ingot thickness into 80-300 mm thinner than the ingot thickness by the conventional DC method. Usually, the thickness of an ingot produced by the DC method is often 400 mm or more. If the thickness is so large, the inside of the ingot is not sufficiently cooled, and the microstructure in the center of the slab becomes very coarse. . Therefore, a fin material in which a high density intermetallic compound exists inside the fin material cannot be obtained. However, by reducing the thickness of the ingot, the cooling rate can be increased to the inside, and a fin material in which a high-density crystallized substance exists in the fin material can be obtained.

  When the thickness of the ingot is thinner than 80 mm, the cooling rate of the entire ingot is too fast, and the intermetallic compound in the produced fin material becomes very fine and dense, which adversely affects the self-corrosion resistance of the fin material. When the ingot thickness exceeds 300 mm, a sufficient cooling rate cannot be obtained up to the inside of the slab, and the microstructure of the slab becomes coarse. As a result, the intermetallic compound in the fin material becomes coarse and sparse, resulting in a decrease in strength, conductivity, and thermal conductivity.

Next, the crystallized substance in the fin material will be more specifically defined.
Sphere sphere equivalent diameter that exists from the surface of the aluminum alloy fin material in the area A of the thickness of 1/20 is present in a region other than the region A and the precipitated crystalline density N ₁ of 0.5μm or more crystallizate The ratio of the crystallization product having an equivalent particle size of 0.5 μm or more to the crystallization product density N ₂ , N ₂ / N ₁ is 1.2 or more, and the crystallization product density N ₁ is 2 × 10 ⁴ / In the case of mm ² or more, good self-corrosion resistance and strength are obtained.
Here, the reason why the crystallized material is limited to 0.5 μm or more is that the crystallized material of 0.5 μm or more is likely to be a starting point of corrosion and lowers the self-corrosion resistance of the fin material. If the crystallized material density N ₁ of the crystallized material having a sphere equivalent particle size of 0.5 μm or more existing in the region A of the fin material is less than 2 × 10 ⁴ pieces / mm ² , the strength, conductivity and heat of the fin material are reduced. Not satisfied with conductivity. Preferably 4 × 10 ⁴ pieces / mm ² or more is preferable.

Further, the crystallized substance density N ₁ of the crystallized substance having a sphere equivalent particle size of 0.5 μm or more existing in the region A and the crystallization having a sphere equivalent particle size of 0.5 μm or more existing in a region other than the region A. When the ratio of N ₂ / N ₁ to the crystallized product density N ₂ of the product is less than 1.2, the crystallized product density of the crystallized product having a sphere equivalent particle size of 0.5 μm or more existing in the region A When N ₁ is increased and the self-corrosion resistance of the fin material is deteriorated, or the crystallized material density N ₂ of the crystallized material having a sphere equivalent particle size of 0.5 μm or more existing in the region other than the region A is decreased. Reduces the strength and thermal conductivity of the material. Preferably 1.4 or more is good.

Next, the dendrite secondary branch interval (hereinafter referred to as DAS) in the 80% region excluding the surface layer region of the ingot obtained is 35 μm or less. The DAS of the ingot is a cooling rate during casting. The strength, conductivity, thermal conductivity, self-corrosion resistance, etc. of the fin material finally obtained greatly depend on the DAS of the ingot.
When the DAS is reduced, the crystallized substances present in the obtained fin material are finely and densely distributed. Accordingly, the strength and thermal conductivity of the fin material are improved. When DAS exceeds 35 μm, the strength and thermal conductivity of the obtained fin material are lowered.

  The casting conditions for obtaining the DAS as described above are such that the cooling rate during casting is as fast as possible. The casting speed is 100 mm / min or more, and more preferably 120 mm / min or more. The amount of cooling water is 2.0 L / cm × min or more, and more preferably 2.50 L / cm × min or more. Next, the produced slab is hot-rolled at a soaking temperature of 440 to 550 ° C. to produce a plate material of 3 to 5 mm. When the soaking temperature is lower than 440 ° C., it becomes difficult to crush the slab by hot rolling, and the equipment load increases. On the other hand, when the soaking temperature is higher than 550 ° C., the intermetallic compound crystallized at the time of casting is coarsened, and the strength and conductivity of the fin material finally produced are lowered.

  Subsequently, the sheet material obtained by hot rolling is cold-rolled, and the cold-rolled sheet material is subjected to intermediate annealing for 6 hours or less at a temperature of 300 to 500 ° C. The formation of precipitates can be promoted, and the strength and electrical conductivity of the manufactured fin material can be improved. When the annealing temperature is lower than 300 ° C., the plate material cannot be completely annealed and is not sufficiently softened, which hinders subsequent processes. When the annealing temperature is higher than 500 ° C., the intermetallic compound existing in the plate material is coarsened, and the strength, conductivity, and thermal conductivity of the fin material finally produced are lowered. Thereafter, the obtained plate material is cold-rolled under a condition where the final rolling rate is 10 to 50% to obtain a fin material having a final plate thickness of 0.05 to 0.1 mm. When the final rolling rate exceeds 50%, the recrystallized grain size after brazing becomes fine, and it becomes difficult to suppress the erosion of the brazing material. Also, the drooping resistance is reduced.

The components of the aluminum alloy used in the present invention are not particularly specified, but in order to satisfy various properties required for the fin material such as corrosion resistance, strength, and thermal conductivity, three elements of Fe, Si, and Mn are added, and the other It is desirable to selectively add elements.
When three elements of Fe, Si, and Mn are added, an Al—Si—Fe—Mn intermetallic compound is formed in the fin material. Since the natural potential of the Al—Si—Fe—Mn intermetallic compound is not significantly different from the natural potential of the matrix, it is considered that the self-corrosion resistance of the fin material is hardly lowered.

  Since the maximum solid solution amount of Fe is very small, it crystallizes out as an intermetallic compound during casting. In combination with the addition of Si, Mn, etc., for example, an Al-Si-Fe-Mn intermetallic compound is produced, and the function of reducing the solid solution amount of Mn and Si in the fin material is reduced, resulting in a decrease in thermal conductivity. In addition, the presence of an intermetallic compound contributes to dispersion strengthening and improves the strength of the fin material. In order to obtain these effects, the Fe content is preferably 0.1 to 2.0 mass%. More preferably, 0.15-1.5 mass% is good.

  By containing Si, it produces an Al-Si-Fe-Mn intermetallic compound together with Fe and Mn, reduces the solid solubility of Mn in the matrix, and increases the conductivity and thermal conductivity of the fin material. Show. In addition, the strength is improved by strengthening the dispersion of the intermetallic compound. Alternatively, the strength can be improved by solid solution in the fin material and solid solution strengthening. In order to obtain these effects, the Si content is preferably 0.5 to 1.5 mass%. More preferably, 0.5 to 1.2 mass% is good.

  Mn contained when producing the fin material is crystallized or precipitated as an intermetallic compound in the production process, and the strength of the produced fin material after brazing can be improved. In addition, by forming an Al-Si-Fe-Mn intermetallic compound together with Si and Fe, the solid solubility of Si can be reduced, the melting point of the fin material can be suppressed, and the conductivity and thermal conductivity can be improved. To do. In order to obtain these effects, the Mn content is preferably 0.5 to 2.0 mass%. More preferably, 0.6 to 1.5 mass% is good.

  By containing Zn, the natural potential of the fin material can be reduced, and the sacrificial anticorrosive effect of the fin material can be improved. In order to obtain this effect, the Zn content is preferably 0.1 to 1.5 mass%. More preferably, 0.5 to 1.5 mass% is good.

  By containing In, the natural potential of the fin material can be reduced as in the case of Zn, and the sacrificial anticorrosive effect of the fin material can be improved. A sufficient sacrificial anticorrosive effect can be obtained by adding a small amount of In. In order to obtain this effect, the content of In is preferably 0.01 to 0.3 mass%. More preferably, 0.05 to 0.15 mass% is good.

  By containing Sn, the natural potential of the fin material can be reduced as in the case of Zn, and the sacrificial anticorrosive effect of the fin material can be improved. In order to obtain this effect, the Sn content is preferably 0.01 to 0.3 mass%. More preferably, 0.05 to 0.2 mass% is good.

  When Cu is contained, solid solution strengthening can be obtained in the same manner as Si and Mn, and the strength of the fin material can be improved. In order to obtain this effect, the Cu content is preferably 0.05 to 0.3 mass%. More preferably, 0.08 to 0.22 mass% is good.

  When Mg is contained, solid solution strengthening can be obtained like Si and Mn, and the strength of the fin material can be improved. In order to obtain this effect, the Mg content is preferably 0.05 to 0.3 mass%. More preferably, 0.08 to 0.15 mass% is good.

  Ni, like Fe, crystallizes out as an intermetallic compound during casting, promotes precipitation of solid solution elements such as Si and Mn, and improves the conductivity of the fin material. Further, when the intermetallic compound is finely crystallized or precipitated in the matrix, dispersion strengthening is obtained, which leads to an improvement in strength. In order to obtain these effects, the Ni content is preferably 0.05 to 1.5 mass%. More preferably, 0.05 to 0.5 mass% is good.

  Zr has a function of coarsening the recrystallized grains of the fin material, suppresses the erosion of the fin material by brazing during brazing, and improves brazing properties. It also has the effect of improving the sag resistance during brazing. In order to obtain these effects, the Zr content is preferably 0.05 to 0.3 mass%. More preferably, 0.05 to 0.15 mass% is good.

Ti, like Si and Mn, is solid-solution strengthened by being dissolved in the matrix, and the strength of the fin material is improved. In order to obtain this effect, the Ti content is preferably 0.05 to 0.3 mass%. More preferably, 0.05 to 0.15 mass% is good.
Hereinafter, the aluminum alloy fin material according to the present invention will be described with reference to examples.

(Example 1)
Alloy No. 1 in Table 1 The ingot thickness was cast to 25 to 500 mm using the component composition of No. 1, and after soaking at a temperature of 440 to 550 ° C., hot rolling was performed at a temperature range of 520 to 280 ° C., and the thickness was 3 The plate material was 5 mm. This plate was cold rolled to 0.076 mm, and then subjected to intermediate annealing at 420 ° C. for 2 hours. The temperature increase rate and temperature decrease rate of this intermediate annealing were 40 ° C./hour. The plate material was subjected to cold rolling with a final rolling rate of 20% to produce an aluminum alloy fin material of 0.061 mm.

The produced aluminum alloy fin material is subjected to a heat treatment corresponding to brazing heating to be cooled to a normal temperature at a cooling rate of 50 to 200 ° C./min after holding at 600 ° C. for 3 minutes in a high purity nitrogen atmosphere, and tensile strength, conductivity region other than the region a of the precipitated crystalline density N ₁ and fin stock crystallizate surface from a sphere-equivalent particle size that exists in the area a of the thickness of 1/20 of above 0.5μm of the fin material The crystallite density N ₂ of a crystallized product having a sphere equivalent particle size of 0.5 μm or more present in N, the ratio N ₂ / N _{1 of} N ₁ and N _2, and the corrosion reduction amount as self-corrosion resistance are shown below. The method was evaluated. The results are shown in Table 2. Details of each evaluation are shown below.

(1) DAS measurement: A cross-sectional structure in the thickness direction of the ingot was observed with an optical microscope, and DAS was measured with a crossing method. The indicated DAS was the average value of DAS in the 80% region excluding 10% of the ingot surface layer region.
(2) Crystallized material density N ₁ , N ₂ and density ratio N ₂ / N ₁ : The crystallized material density in the fin material was examined by observing a cross-section of the fin material using a scanning electron microscope. First, 10 visual fields were observed for each sample, and the density of the intermetallic compound was determined by image analysis of SEM photographs of the respective visual fields. The density and density ratio of the indicated intermetallic compounds were average values obtained from 10 fields of view.
(3) Self-corrosion resistance (corrosion reduction): Based on JIS Z2371, a 200-hour salt spray test was performed, and then the corrosion reduction was measured.
(4) Tensile strength: It was carried out at room temperature according to JIS Z2241 under the conditions of a tensile speed of 10 mm / min and a gauge length of 50 mm.
(5) Conductivity: It was determined by measuring the electrical resistance in a constant temperature soda at 20 ° C. based on JIS H0505.

As is clear from Tables 1 and 2, Example No. of the present invention in which the ingot thickness is within the scope of the present invention. 1-No. The aluminum alloy fin material No. 6 was excellent in tensile strength after brazing heating, electrical conductivity, and self-corrosion resistance.
Among these, the invention example No. 1-No. In No. 4, sufficient characteristics are obtained in terms of strength and conductivity.

On the other hand, Comparative Example No. whose ingot thickness is smaller than the range of the present invention. The aluminum alloy fins 20 and 21 were excellent in tensile strength and electrical conductivity after brazing addition heat, but were inferior in self-corrosion resistance. When the slab thickness is small, the cooling rate at the time of casting becomes high, and the microstructure of the ingot becomes fine. As a result, although tensile strength and electrical conductivity were improved, self-corrosion resistance was hindered by increasing the number of corrosion starting points in the fin material.
Moreover, comparative example No. whose slab thickness is larger than the range of this invention. 22-No. The 24 aluminum alloy fin material could not satisfy the required properties in terms of tensile strength and conductivity after brazing heat. However, the self-corrosion resistance was good. Such a result was obtained due to a decrease in the cooling rate during casting due to the large slab thickness.
From the above, the crystallized substance density N ₁ of the crystallized substance having a sphere equivalent particle size of 0.5 μm or more existing in the region A of the fin material is 2 × 10 ⁴ pieces / mm ² or more, and the crystallized substance density N ₁ and the ratio of the crystallized material density N ₂ of the crystallized material having a sphere equivalent particle size of 0.5 μm or more existing in a region other than the region A of the fin material, and N ₂ / N ₁ is 1.2 or more. In this case, it was found that an aluminum alloy fin material having a good balance in strength, conductivity and self-corrosion resistance of the fin material can be obtained.

(Example 2)
Alloy No. shown in Table 1 Aluminum alloy ingots having a component composition of 1 to 15 were produced by the DC method. The ingot thickness was 100 mm. The ingot was soaked at 450 ° C., and then hot rolled to form a plate having a thickness of 3.5 mm. The plate was cold rolled to a thickness of 0.076 mm, and then subjected to intermediate annealing at 420 ° C. for 2 hours. The temperature increase rate and temperature decrease rate of this intermediate annealing were 40 ° C./hour. The plate material was cold-rolled with a final rolling rate of 20% to produce an aluminum alloy fin material having a thickness of 0.061 mm.
The obtained aluminum alloy fin material was subjected to heating equivalent to brazing heating, and a tensile test, conductivity measurement, and corrosion test were performed. The results are shown in Table 3.

Invention Example No. 7-No. In No. 16, an aluminum alloy fin material having sufficient strength, electrical conductivity, and self-corrosion resistance was obtained. On the other hand, comparative example No. including the thing outside the range of a suitable alloy composition. 25-No. For No. 29, a fin material satisfying all of strength, electrical conductivity, and self-corrosion resistance was not obtained.
Comparative Example No. using an aluminum alloy having a Mn content of more than 1.5 mass%. No. 25 is strengthened by solid solution strengthening with solid solution Mn, but the strength is obtained, but the decrease in conductivity is remarkable, the Mn content is less than 0.5 mass%, and the Fe content is less than 0.1 mass%. , Ni content of more than 1.5 mass% Comparative Example No. In No. 26, the amount of dissolved Mn was small, and sufficient conductivity was obtained due to the precipitation promoting effect by Ni, but the strength was slightly insufficient, and the self-corrosion resistance was reduced by excessive addition of Ni.
Comparative Example No. with a Mn content of less than 0.5 mass%. For 27, a sufficient electrical conductivity was obtained due to a decrease in the amount of dissolved Mn, but the strength was significantly reduced.
Comparative Example No. with a Ti content greater than 0.3 mass% In No. 28, sufficient strength was obtained by solid solution strengthening of the added Ti. However, no necessary characteristics were obtained in terms of conductivity and self-corrosion resistance.
Comparative Example No. having a Si content of less than 0.5 mass% In No. 29, the strength was greatly reduced by reducing the amount of Si added. From the above, in Examples 11 to 15 where the alloy composition is outside the preferred range of the present invention, it is not possible to obtain an aluminum alloy fin material that can satisfy all the properties of tensile strength, conductivity, and self-corrosion resistance. It was.

Claims (5)

Sphere-equivalent grain sphere-equivalent particle size that exists from the surface of the aluminum alloy fin material in the area A of the thickness of 1/20 is present in a region other than the region A and the intermetallic compound has a number density N ₁ above 0.5μm The ratio between the number density N ₂ of the intermetallic compound having a diameter of 0.5 μm or more, N ₂ / N ₁ is 1.2 or more, and the sphere equivalent particle size existing in the region A is between the metals of 0.5 μm or more. The aluminum alloy fin material, wherein the compound has a number density N ₁ of 2 × 10 ⁴ pieces / mm ² or more. The aluminum alloy fin material according to claim 1, wherein the intermetallic compound is a crystallized product. The aluminum alloy fin material, wherein the aluminum alloy fin material is manufactured from an ingot having 80% or more of a region having a dendrite secondary branch interval of 35 μm or less. The aluminum ingot is characterized in that the ingot is an ingot cast to a thickness of 80 to 300 mm using a casting method including two-stage cooling of primary cooling by a mold and secondary cooling by cooling water. Manufacturing method of fin material. The method for producing an aluminum alloy fin material according to claim 4, wherein the casting method is a direct chill method.