JP2009183980A - Brazing method for aluminum alloy, and aluminum alloy cladding material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brazing method for an aluminum alloy in which brazing property and corrosion resistance are made consistent, and to provide an aluminum alloy cladding material. <P>SOLUTION: The aluminum alloy cladding material obtained by cladding a sacrificial anode material comprising 3.0 to 6.0% Si and 0.5 to 6.5% Zn, and the balance Al with inevitable impurities at least to one side of a core material is coated with flux composed of potassium silicofluoride with inevitable impurities, and heating is performed in an inert gas. In this way, by Si in the material and Si produced by substitution reaction, brazing can be satisfactory performed even in a small flux adhesion amount. Further, since an aluminum product material after brazing has excellent corrosion resistance, a brazed product having higher quality can be obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an aluminum alloy brazing method and an aluminum alloy clad material in which Si is precipitated from a flux during brazing heating to produce an Al-Si brazing material and brazed, and in particular, an automotive heat exchanger is provided. The present invention relates to an aluminum alloy brazing method and an aluminum alloy clad material, which are constituent tube materials.

For joining aluminum products or aluminum alloy products such as automotive heat exchangers, a brazing method called a Nocolok brazing method is widely used. With Nocolok brazing, KF-AlF _3- based flux such as potassium aluminum fluoride is attached to the aluminum product or aluminum alloy product member and brazing material to be joined, and the flux and brazing material melt in an inert gas atmosphere such as nitrogen gas. This is a method in which a predetermined part is brazed by heating to a predetermined temperature.
As the brazing material, Al-Si JIS 4045 alloy or JIS 4343 alloy is used. Particularly in automotive heat exchangers, a brazing sheet is often used in which an aluminum alloy is used as a core material and a brazing material is laminated on the surface thereof and then clad.

Such automotive heat exchangers are often exposed to the outdoor environment, and therefore it is necessary to ensure corrosion resistance. In particular, when a through-hole is generated due to corrosion, a tube material serving as a refrigerant passage is often subjected to anticorrosion treatment because a refrigerant leaks and does not function as a heat exchanger. In order to prevent corrosion of the tube material, a corrosion-resistant treatment of the tube material is performed by preferentially corroding an alloy that is lower in potential than the tube material as a sacrificial anode material on the surface of the tube material. It has been broken.
For example, a sacrificial anode layer is formed by clad an alloy containing Zn that becomes potential-base on the surface of the tube material. Therefore, when joining a tube material and a bare material, the brazing sheet which clad the brazing material which consists of an Al-Si-Zn type alloy on the surface of a tube material was brazed, and the heat exchanger was comprised.

In recent years, the heat exchanger has been reduced in size and weight, and the tube material of the heat exchanger also tends to be thin. Correspondingly, a tube material with higher corrosion resistance has been required. However, it is difficult to ensure sufficient corrosion resistance in a brazing sheet clad with a brazing material having an Al—Si—Zn-based sacrificial anode function.
When a large amount of Zn is added to the brazing material in order to obtain a sufficient anticorrosive effect, Zn in the eutectic part of the brazing material is concentrated during brazing, so that the Zn-concentrated part is corroded within a short time. And the anticorrosion function is lost.
On the other hand, there is a brazing sheet in which an Al—Zn alloy is clad as an intermediate layer between a core material and an Al—Si brazing filler metal layer. In this brazing sheet, an unmelted Al—Zn-based alloy layer remains as a sacrificial anode layer after brazing, so that it is superior in corrosion resistance to a brazing sheet clad with an Al—Si—Zn-based alloy. However, since the configuration of the brazing sheet is complicated, the material production is difficult and the cost is increased.

  On the other hand, Patent Document 1 and Patent Document 2 propose a method of brazing by applying potassium silicofluoride without cladding an Al—Si brazing material on a tube material. This method is a method in which potassium silicofluoride reacts with an aluminum product or an aluminum alloy product material (hereinafter referred to as “aluminum product material”) during brazing heating to produce an Al—Si alloy and potassium aluminum fluoride and braze. It is. In this method, it is not necessary to clad an Al—Si—Zn brazing alloy, and only an Al—Zn sacrificial anode material needs to be clad, so that good corrosion resistance can be obtained.

JP 08-267229 A JP-A-12-015481

However, a large amount of potassium silicofluoride is required to produce a sufficient amount of Al—Si alloy for brazing from potassium silicofluoride.
Moreover, even if such a large amount of coating is applied, the aluminum product material and non-contact potassium silicofluoride remain on the aluminum product material as an unreacted flux, and a sufficient amount of Al-Si alloy is not generated. The brazeability cannot be ensured.
The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide an aluminum alloy brazing method and an aluminum alloy clad material that have both brazability and corrosion resistance.

  That is, the brazing method of the present invention includes a sacrificial anode containing 3.0 to 6.0% (wt%, the same applies hereinafter) of Si, 0.5 to 6.5% of Zn, and the balance of Al and inevitable impurities. The material is characterized in that a flux composed of potassium silicofluoride and inevitable impurities is applied to an aluminum alloy clad material clad on at least one surface of a core material and heated in an inert gas.

  It is desirable to contain 5-40% potassium aluminum fluoride or 10-40% zinc potassium fluoride.

  Moreover, you may make it contain 15 to 40% of potassium aluminum fluoride and zinc potassium fluoride.

The aluminum alloy clad material used in the brazing method of the present invention contains a sacrificial anode material containing 3.0 to 6.0% Si and 0.5 to 6.5% Zn, with the balance being Al and inevitable impurities. Is clad on at least one surface of the core material, and is used for brazing in an inert gas using a flux mainly composed of potassium silicofluoride.
The thickness of the sacrificial anode material is desirably 25 μm or more.

  According to the brazing method of an aluminum alloy and the aluminum alloy clad material of the present invention, it is possible to braze satisfactorily even with a small amount of flux due to Si generated by substitution reaction from Si and flux in the material. Moreover, the aluminum product or aluminum alloy product after brazing has excellent corrosion resistance.

The present invention is described in detail below.
A method of applying a flux composed of potassium silicofluoride and producing a brazing material by a substitution reaction with an aluminum product material and brazing has been proposed. In general, K ₂ SiF ₆ is used as potassium silicofluoride.

It is considered that the following substitution reaction occurs between the flux applied on the aluminum product material and the aluminum product material during the temperature rise of the brazing heating.
3K ₂ SiF ₆ + 4Al → 3Si + 2K AlF ₄ + 2K ₂ AlF ₅
Since the produced Si produces Al and Al—Si brazing material in the aluminum product material, it is not necessary to use a material previously clad with the Al—Si brazing material. The produced KAlF ₃ and K ₂ AlF ₅ are flux components used in the normal Nocolok brazing method, and are dissolved before the brazing material being brazed is melted to form an oxide film on the surface of the aluminum product material. Removed to allow brazing.

However, in order to produce a sufficient amount of brazing material for brazing from potassium silicofluoride, it is necessary to apply a large amount of potassium silicofluoride. For example, when an Al-10% Si alloy brazing material layer having a thickness of 20 μm is to be generated from a flux of K ₂ SiF ₆ , it can be applied thickly on an aluminum product material at a flux coating amount of 20 g / m ² or more. Necessary. When a heat exchanger is assembled using a tube material coated with a thick flux, dimensional variation during brazing increases, and good brazing performance is often not obtained.
Furthermore, since the substitution reaction between the flux and the aluminum product material occurs only in the area where they are in direct contact with each other, even if the flux is thickly applied, the substitution reaction cannot always be promoted, and it does not contribute to the reaction after brazing. Potassium silicofluoride may remain.

Therefore, in the present invention, a material containing Si is clad on the surface on which the flux is applied, and Si is supplied also from the aluminum product material to produce an Al-Si brazing material sufficient for brazing even with a small potassium fluorosilicate coating amount. Made it possible to do.
When a flux made of potassium silicofluoride is applied onto an aluminum product material containing Si and brazed and heated, a substitution reaction occurs during temperature rise, and Si is generated. Since 3.0 to 6.0% Si originally exists on the aluminum product material, a sufficient amount of brazing material can be obtained even with a small amount of Si generated from the flux. The substitution reaction of the Si-containing material occurs only on the surface layer, and if the potassium silicofluoride is completely consumed by the substitution reaction, no further reaction takes place. Therefore, an unreacted Si-containing layer remains under the Al—Si brazing material layer generated on the surface layer.

  Therefore, the sacrificial anode layer of the Al-Si-Zn alloy is unreacted under the Al-Si brazing material layer by brazing and heating using a clad material in which Zn or the like is added as a sacrificial anode material to the Si-containing material. Therefore, excellent corrosion resistance can be ensured.

The reason why the Si content is 3.0 to 6.0% is as follows.
When the Si content is less than 3.0%, a sufficient amount of Si for brazing cannot be secured, so that the amount of Al—Si brazing material produced is small and brazing performance is lowered.
When the Si content exceeds 6.0%, the total amount of Si supplied from Si and potassium silicofluoride in the sacrificial anode material increases, and a large amount of Al—Si brazing material is generated. For this reason, erosion by the Al—Si brazing material progresses to the inside of the sacrificial anode material, and the number of unreacted sacrificial anode layers is reduced, so that the corrosion resistance is lowered.
Further, even in the unreacted sacrificial anode layer, a part that is partially melted and Zn or the like is generated is generated, so that the self-corrosion resistance of the sacrificial anode layer is remarkably lowered and the corrosion resistance is lowered.
A Si content of 3.0 to 4.5% is more preferable because of a good balance between brazing and corrosion resistance.

Zn is added as a sacrificial anode material in order to reduce the potential.
The reason why the Zn content is set to 0.5 to 6.5% is less than 0.5%, the effect of the sacrificial anode material cannot be sufficiently obtained, so that the corrosion resistance is lowered. Further, if the Zn content exceeds 6.5%, the melting start temperature of the sacrificial anode layer decreases, so that partial melting occurs in the sacrificial anode layer and Zn concentration occurs, and the sacrificial anode layer self- Corrosion resistance decreases. Moreover, Zn concentration also occurs in the brazing filler metal part produced by the reaction with the flux, and the brazed joint part may corrode in a short time and peel off. The Zn content is more preferably 1.0 to 3.0%.

  The thickness of the sacrificial anode material is desirably 25 μm or more. Al—Si brazing material is produced by the substitution reaction between potassium silicofluoride and the surface of the sacrificial anode material, but the Al—Si brazing material produced on the surface diffuses inside the sacrificial anode material. When the thickness of the sacrificial anode material is less than 25 μm, the diffused brazing material reaches the core material, so that the corrosion resistance decreases.

Next, the components of the flux and the reasons for limitation will be described.
The flux component potassium silicofluoride is necessary for brazing by the method of the present invention, and a common component is K ₂ SiF ₆ . If the potassium silicofluoride content in the flux is less than 60%, the amount of Si produced by the reaction with Al during brazing heating is small, so the amount of Al—Si brazing material is reduced and brazing performance is reduced.

Potassium silicofluoride may be used alone, but potassium aluminum fluoride or zinc potassium fluoride can be further added to the flux.
Potassium aluminum fluoride is added as a mixture of KAlF ₄ , K ₂ AlF ₅ , K ₂ AlF ₅ .H ₂ O.
By adding potassium aluminum fluoride, the substitution reaction between potassium silicofluoride and Al is promoted and Si is rapidly generated, so that unreacted residual potassium silicofluoride can be reduced.
Potassium aluminum fluoride has a low melting point and starts melting at a temperature lower than the substitution reaction between potassium silicofluoride and aluminum. This destroys the oxide film on the surface of the sacrificial anode material, increases the contact portion between potassium silicofluoride and Al, and promotes the substitution reaction.
If the added amount of potassium aluminum fluoride exceeds 40%, the amount of Si produced by the reaction with Al during brazing heating is small, so the amount of Al—Si brazing material is reduced and brazing performance is lowered.

As the zinc potassium fluoride, KZnF ₃ is added.
Zinc potassium fluoride reacts with Al to produce Zn on the surface of the aluminum product material. Since the generated Zn diffuses into Al, the Zn concentration of the sacrificial anode material increases, and the sacrificial anode material becomes a lower potential. Therefore, even if the Zn content added to the sacrificial anode material is small, good corrosion resistance can be ensured.
If the amount of zinc potassium fluoride exceeds 40%, the amount of Si produced by the reaction with Al during brazing heating is small, so the amount of Al—Si brazing material is reduced and brazing performance is lowered.

  As the core material, an Al-Mn alloy such as JISA3003 is applied. Furthermore, in order to ensure the potential difference between the sacrificial anode material and the core material, a method of adding Cu to the core material can also be applied. Also, a method of adding elements such as Si, Fe, Ti, Zr, etc. can be applied in order to ensure the strength after brazing. Addition of Mg to the core material is effective for securing the strength after brazing, but the brazing property is greatly reduced because the substitution reaction between potassium silicofluoride and aluminum is hindered. Better.

[Example 1]
Hereinafter, the present invention will be described specifically by way of examples.
An alloy having a composition obtained by adding 0.5% of Cu to the JIS A3003 alloy was die-cast and face-cut to a thickness of 40 mm to produce an ingot for core material.
An alloy having the composition shown in Table 1 was cast for a skin material, and rolled to a predetermined thickness by hot rolling at 500 ° C. The core material and the skin material were combined with the combinations and clad rates shown in Table 2, and rolled to a thickness of 3 mm by hot rolling. Furthermore, it rolled to 0.3 mm by cold rolling, and annealed on the conditions of 360 degreeC x 2 hours, and manufactured the brazing sheet.

The obtained brazing sheet was cut into a length of 100 mm and a width of 20 mm, and then an alcohol suspension of flux was applied to the skin material surface of the brazing sheet. The flux used was a mixture of potassium silicofluoride (K ₂ SiF ₆ ) powder, potassium aluminum fluoride (KAlF ₄ ) powder, and zinc potassium fluoride (KZnF ₃ ) powder shown in Table 2.

The amount of flux applied was 10 g / m ² by weight measurement before and after application. The brazing sheet after flux application was made to correspond to the tube material of the heat exchanger, and a corrugated fin was combined on the flux application surface to produce a simulated core of the heat exchanger. As the fin material, 1% Zn was added to JIS A3003 alloy, a bare material having a plate thickness of 0.1 mm and a width of 20 mm was used, and corrugated with a fin pitch of 3 mm was used. The simulated core was brazed by heating in a nitrogen atmosphere at 600 ° C. for 3 minutes. Further, as a conventional example, a KF-AlF ₃ type flux (KAlF ₄ or the like) generally used in Noclock brazing was applied, and similarly brazed and heated.

  About the simulated core after brazing, the joining rate of a brazing sheet and a corrugated fin was measured. Furthermore, a corrosion resistance test was performed on the simulated core that was brazed. In the corrosion resistance test, the outer surface of the simulated core (the surface without the corrugated fin) was masked, and a CASS test according to JISH8681 was performed for 1000 hours. The corrosion depth of the brazing sheet after the CASS test was measured. Table 2 shows the fin adhesion rate and the maximum pitting corrosion depth after the CASS test.

  As shown in Table 1, the skin materials of Invention Examples A1 to A7 all contain 3.0 to 6.0% Si and 0.5 to 6.5% Zn, and in particular, Invention Example A4 is Si. 5.8% which is close to 6.0% of the upper limit value, while Example A5 of the invention contains 0.6% of Zn which is close to 0.5% of the lower limit value, and Example A7 of the invention contains Zn as the upper limit value. Of 6.4%, which is close to 6.5%.

On the other hand, in the skin material of each comparative example, the comparative example A8 has an Si content of 2.6% and does not reach the lower limit of 3.0% of the present invention, and the comparative example A9 is Si. The content is 6.2%, which exceeds the upper limit of 6.0% of the present invention.
Comparative Example A10 has a Zn content of 0.4% and does not reach the lower limit of 0.5% of the present invention, and Comparative Example A11 has a Zn content of 7.0% and has an upper limit of the present invention. It exceeds the value of 6.5%.
Comparative Example A12 has an Si content of 7.5% and exceeds the upper limit of 6.0% of the present invention, and Comparative Example A13 has an Si content of 10.5% and the upper limit of the present invention. Exceeding 6.0%.

Among each of the brazing sheets using the skin materials of the invention examples A1 to A7 and comparative examples A8 to A13, the invention example No. 1-No. 7 were respectively made of skin material A1 to skin material A7, with a cladding rate of 10%, a cladding thickness of 30 μm, and a coating flux of K ₂ SiF _{6 of} 100%. The fin adhesion rate measured for the bonding rate between these brazing sheets and corrugated fins is the same as that of Example No. of the present invention. 1 was 85%, but Example No. 2-No. 7 was 100% in all cases.
In addition, the maximum pitting corrosion depth measured for the corrosion depth of the brazing sheet after the CASS test is No. 5 was 80 μm, but the present invention example No. 1-No. 4 and Invention Example No. 6, no. 7 was 35 to 60 μm.

Furthermore, Example No. of the present invention. 8, no. No. 9 uses the skin material A2, and the invention example No. 10 is composed of a skin material A6, and has a clad rate of 5 to 15%, a clad thickness of 15 to 45 μm, and a coating flux of K ₂ SiF ₆ 100%. However, the thickness of the skin material is the same as that of Example No. of the present invention. 9 was 45 μm exceeding 25 μm. 8 and Invention Example No. 10 was 15 μm which did not reach 25 μm.
As a result, the fin adhesion rate measured for the bonding rate between these brazing sheets and corrugated fins was determined as No. 1 of the present invention. 9 was 100%, but Example No. 8, no. 10 was 90% in all cases.

In addition, the maximum pitting corrosion depth measured for the corrosion depth of the brazing sheet after the CASS test is No. 8, no. 10 were 80 μm and 75 μm, respectively. 9 was 45 μm.
In addition, Invention Example No. 11, no. No. 12 was formed using the skin material A1, and the cladding ratio was 10% and the cladding thickness was 30 μm. However, the coating flux is No. 11 is K ₂ SiF ₆ 96%, KAlF ₄ 4%, and does not meet the condition of containing 5-40% potassium aluminum fluoride. On the other hand, Invention Example No. No. 12 conforms to the condition that the composition of the coating flux is 94% K ₂ SiF ₆ and ₆ % KAlF ₄ and contains 5 to 40% potassium aluminum fluoride.

As a result, the fin adhesion rate measured for the bonding rate between these brazing sheets and corrugated fins was determined as No. 1 of the present invention. 11 was 85%, but Example No. 12 was 100%.
In addition, the maximum pitting corrosion depth measured for the corrosion depth of the brazing sheet after the CASS test is No. 11, no. 12 were 50 μm and 55 μm, respectively.
In addition, Invention Example No. 13, no. No. 14 was made of skin materials A3 and A4, respectively, with a cladding ratio of 10% and a cladding thickness of 30 μm. In addition, the composition of the coating flux is the example No. of the present invention. 13 is K ₂ SiF ₆ 80% and KAlF ₄ 20%. 14 is K ₂ SiF ₆ 65%, KAlF ₄ 35%, which satisfies the condition of containing 5-40% potassium aluminum fluoride.

As a result, the fin adhesion rate measured for the bonding rate between these brazing sheets and corrugated fins was determined as No. 1 of the present invention. No. 13 is 100%. 14 was 95%.
In addition, the maximum pitting corrosion depth measured for the corrosion depth of the brazing sheet after the CASS test is No. 13, no. 14 were 50 μm and 55 μm, respectively.

In addition, Invention Example No. 15-No. No. 17 was made of a skin material A5 with a cladding ratio of 10% and a cladding thickness of 30 μm. However, the coating flux is No. 15 is K ₂ SiF ₆ 82%, KZnF ₃ 8%, and does not meet the condition of containing 10 to 40% zinc potassium fluoride. On the other hand, Invention Example No. No. 16 conforms to the condition that the composition of the coating flux is 88% K ₂ SiF ₆ and 8% KZnF ₃ and contains 10 to 40% zinc potassium fluoride. Furthermore, Example No. of the present invention. No. 17 conforms to the condition that the composition of the coating flux is 65% K ₂ SiF ₆ and 35% KZnF ₃ and contains 10 to 40% zinc potassium fluoride.

As a result, the fin adhesion rate measured for the bonding rate between these brazing sheets and corrugated fins was determined as No. 1 of the present invention. No. 17 was 90%, but Example No. 15 and 16 were 100%.
In addition, the maximum pitting corrosion depth measured for the corrosion depth of the brazing sheet after the CASS test is No. 16, no. 17 are 50 μm and 40 μm, respectively. 15 was 80 μm.

Furthermore, Example No. of the present invention. 18 is made of a skin material A5, and has a clad rate of 10% and a clad thickness of 30 μm. The coating flux is K ₂ SiF ₆ 82%, KAlF ₄ 6%, KZnF ₃ 12%, potassium aluminum fluoride, and zinc potassium fluoride. To meet the condition of containing 15 to 40%.
As a result, the fin adhesion ratio obtained by measuring the bonding ratio between the brazing sheet and the corrugated fin was determined as No. 1 of the present invention. 18 was 100%.

  The maximum pitting depth measured for the corrosion depth of the brazing sheet after the CASS test is No. 18 was 50 μm.

Comparative Example No. 19-No. Each of the Nos. 22 was made of comparative example skins A8 to A11, with a cladding rate of 10%, a cladding thickness of 30 μm, and a coating flux of K ₂ SiF _{6 of} 100%. The fin adhesion ratio measured for the bonding ratio between these brazing sheets and corrugated fins was compared with that of Comparative Example No. 20-No. No. 21 was 100%, but Comparative Example No. In 19 it was only 20%.
Moreover, the maximum pitting corrosion depth which measured the corrosion depth about the brazing sheet after a CASS test is comparative example No.2. In No. 20, a through hole is formed. No. 21 is 200 μm, Comparative Example No. No. 22 reached 160 μm, and the corrosion resistance was remarkably inferior to each of the inventive examples.

Further, Comparative Example No. 23, no. Reference numeral 24 is formed using a skin material A4, and the cladding ratio is 10% and the cladding thickness is 30 μm. However, the coating flux is No. 23 exceeds K ₂ SiF ₆ 55% and KAlF ₄ 45%, exceeding the upper limit of containing 40% or less of aluminum aluminum fluoride. In addition, Invention Example No. 24 is K ₂ SiF ₆ 55% and KZnF ₃ 45%, which exceeds the upper limit of containing 40% or less of zinc potassium fluoride. For this reason, the adhesion rates of the fins measured for the bonding rate between these brazing sheets and corrugated fins were only 35% and 25%, respectively.

Conventional Example No. 25-No. Reference No. 27 was made of comparative example skins A9, A12, and A13, each having a cladding rate of 10%, a cladding thickness of 30 μm, and a coating flux of K ₂ SiF _{6 of} 100%. The fin adhesion ratio measured for the bonding ratio between these brazing sheets and corrugated fins was compared with that of Comparative Example No. 26, no. 27 was 100%, but Comparative Example No. At 25, only 20%. Moreover, about the brazing sheet after a CASS test, in the measurement of corrosion depth, it is comparative example No. 26, no. In each of 27, through holes were formed.

As is clear from the results shown in Table 2 above, No. In 1-18, it became a high fin adhesion rate, and it was confirmed that it is excellent brazing property. Moreover, as a result of the CASS test, it was confirmed that the progress of pitting corrosion was suppressed by the sacrificial anticorrosive effect. No. In No. 19, since the amount of Si in the skin material is less than the range of the present invention, the amount of brazing material was insufficient with the amount of Si produced from potassium silicofluoride, and good brazing properties were not obtained. No. In No. 20, since the amount of Si in the skin material was larger than the range of the present invention, the skin material was corroded in a short period of time, and a sufficient sacrificial anticorrosive effect could not be obtained. No. . 21 and no. . No. 22 was the result that the sacrificial anticorrosive effect could not be obtained and the corrosion resistance was inferior because the amount of Zn in the skin was outside the scope of the present invention. No. . 23 and no. . No. 24 was a result of inferior brazing because the content of potassium silicofluoride in the coating flux was less than the range of the present invention, and the amount of Al—Si brazing material produced was insufficient.

Claims (6)

A sacrificial anode material containing 3.0 to 6.0% Si (wt%, the same applies hereinafter), 0.5 to 6.5% Zn, and the balance being Al and inevitable impurities is clad on at least one side of the core material A method for brazing an aluminum alloy, comprising: applying a flux composed of potassium silicofluoride and inevitable impurities to the aluminum alloy clad material, and heating in an inert gas. An aluminum alloy clad material in which a sacrificial anode material containing 3.0 to 6.0% Si and 0.5 to 6.5% Zn and the balance being made of Al and inevitable impurities is clad on at least one side of a core material, A method for brazing an aluminum alloy, comprising applying 5 to 40% potassium aluminum fluoride, the balance being composed of potassium silicofluoride and inevitable impurities, and heating in an inert gas. An aluminum alloy clad material in which a sacrificial anode material containing 3.0 to 6.0% Si and 0.5 to 6.5% Zn and the balance being made of Al and inevitable impurities is clad on at least one side of a core material, A method for brazing an aluminum alloy, comprising applying 10-40% zinc fluoride and a flux consisting of potassium silicofluoride and inevitable impurities, and heating in an inert gas. An aluminum alloy clad material in which a sacrificial anode material containing 3.0 to 6.0% Si and 0.5 to 6.5% Zn and the balance being made of Al and inevitable impurities is clad on at least one side of a core material, Aluminum alloy containing 15-40% of potassium aluminum fluoride and potassium potassium fluoride, the remainder being applied with a flux consisting of potassium silicofluoride and inevitable impurities, and heated in an inert gas Brazing method.
Mainly composed of potassium silicofluoride containing 3.0 to 6.0% Si and 0.5 to 6.5% Zn, with the balance being a sacrificial anode material consisting of Al and inevitable impurities on at least one side of the core material. Aluminum alloy clad material used for brazing in inert gas using flux as a component. The aluminum alloy cladding material according to claim 5, wherein the thickness of the sacrificial anode material is 25 μm or more.