JPH07102451B2 - Method of manufacturing aluminum material for brazing, and brazing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum product manufactured by brazing specifications, such as an automobile radiator, an evaporator and a condenser for a car air conditioner,
Aluminum materials for brazing to be used for other aluminum heat exchangers for other electric and industrial machines, or aluminum brazing products such as aluminum intake manifolds for automobiles, a manufacturing method thereof, and a brazing method using the material. Regarding

[0002]

2. Description of the Related Art When manufacturing an aluminum product as described above by brazing, a method of brazing and joining constituent members using a non-corrosive fluoride type flux is often used. Conventionally, when performing such non-corrosive fluoride-based flux brazing, the aluminum material is first press-molded or cut as needed to temporarily assemble it into a product shape, and then the aqueous suspension solution of the flux is applied to the surface of the aluminum material. After that, it was pre-dried and then brazed by heating to the brazing temperature in a non-oxidizing atmosphere. At this time, recently, a continuous furnace in which a flux pre-drying furnace and a brazing furnace are connected has become the mainstream. The normal non-corrosive fluoride flux brazing flux film is formed by immersing it in a suspension, so it is easy to have extremely uneven thickness, and the thickness is about 100 μm in thick areas, so it is brittle. And other treatments cause partial peeling, making it impossible to braze that portion. Therefore, usually, as described above, the product is assembled into a complicated product shape, and the work of applying and drying the suspension is performed immediately before brazing. However, in such a method, the work efficiency is not good because the work of applying and drying the suspension is required after assembling into a complicated product shape. In addition, since there is a drying process immediately before the brazing process, if this process is not performed for a sufficient time, the generated moisture is brought into the brazing furnace and the dew point in the brazing atmosphere is lowered, which deteriorates the brazing property. On the other hand, there is a dilemma that if the drying process takes too much time, it will be the rate-determining process for the entire line. Also, since it is applied in a complicated product shape, the application amount tends to be non-uniform, and there is no choice but to apply a large amount for safety, so there is a tendency that the amount of flux attached to the aluminum member generally increases. When the brazing furnace is contaminated or the molten flux in the furnace is dropped and accumulated in the furnace and the metal furnace wall is corroded, the brazing furnace is frequently cleaned and overhauled. There was also the problem of being forced to do so. Furthermore, the non-corrosive fluoride-based flux components that are normally used become a liquid phase at the brazing temperature, so excess flux flows, and the excess flux locally remaining on the surface of aluminum products after brazing is gray. There is also a problem that not only the appearance of white spots occurs and the color tone becomes uneven and the appearance is impaired, but also the subsequent surface treatment is hindered. Further, excessive flux application has been a problem in terms of cost. Further, in brazing using a non-corrosive fluoride-based flux, when an aluminum material containing Mg is used, F in the flux and Mg in the aluminum material react rapidly to form MgF ₂ having poor wettability. A material containing more than 2% of Mg could not be used, and the user's needs of improving strength and reducing thickness and weight were encountered.

On the other hand, vacuum brazing without using flux is also widely used. When brazing aluminum in a vacuum, add Mg to the brazing material, and add M when brazing.
The oxide film formed on the surface by the evaporation of g is destroyed to improve the brazing flow and brazing. However, when Mg is added to the brazing filler metal, there is a drawback that the inside of the vacuum furnace is contaminated due to the evaporation of Mg and cleaning takes time.
Therefore, there is also a demand for a method capable of vacuum brazing without using a Mg getter material. However, the usual non-corrosive fluoride-based flux becomes a liquid phase at the brazing temperature and easily corrodes and contaminates the brazing furnace. Furthermore, it cannot be used for vacuum brazing because it easily vaporizes and contaminates the entire vacuum system.

In order to solve these problems, there is an improved technique for solving these problems by performing a surface treatment on an aluminum material in advance. As a method close to the non-corrosive fluoride flux brazing, the aluminum material is brought into contact with a treatment solution containing potassium and fluorine, and K ₂ A is produced on the surface of the aluminum material by a chemical reaction.
A method of brazing after forming the IF ₅ layer has been proposed. (JP-A-60-83771). Further, as a method of promoting the above reaction to form a K ₂ AlF ₅ layer in a short time, a method of electrolytically converting an aluminum material in the above treatment solution has been proposed. (Japanese Patent Laid-Open No. 61-52984
issue). According to these methods, the amount of flux attached to the aluminum material can be reduced, and the problems of contamination in the furnace and appearance of the appearance after brazing can be improved. However, the former method has a problem that productivity is low because the reaction is slow, and thus the electrolytic treatment apparatus and the like are required as in the latter method, and there is a problem that the cost is too high. Further, even in the case of this flux, there is a problem that not only the appearance is impaired because it becomes a liquid phase at the brazing temperature, but also the subsequent surface treatment is hindered.
There is also proposed a brazing method in which a flux film is formed by a dry method (a flux component is volatilized in a vacuum and a brazing object is put therein and vapor-deposited) (JP-A-4-111968). However, since this method is carried out in a vacuum system, there are disadvantages that the equipment is very large and the cost is too high.

[0005]

Therefore, the inventor of the present application
By avoiding the above-mentioned problems of ordinary non-corrosive fluoride flux brazing caused by assembling a complex product shape and then applying flux, M as a getter material is avoided.
A method of brazing that enables vacuum brazing without including a large amount of g as in the conventional method and has improved all of the problems of the above-mentioned improved technology such as productivity, equipment cost, surface properties, and fillet forming ability. In order to obtain a flat plate, there is no problem even if it is formed by a flat plate and then subjected to press working or other handling. A substitute for a flux film and a vacuum brazing method that does not contain a large amount of Mg as a getter material can be used. I sought.

[0006]

As a result, the present inventors have found that when an aluminum material is treated with hydrogen fluoride or an aqueous solution containing an inorganic acid such as nitric acid, sulfuric acid, phosphoric acid or chromic acid, it is etched and fluorinated at the same time. The present invention has been completed by finding that an aluminum film is formed and that this film has preferable characteristics. That is, the aluminum material for brazing according to claim 1, which is treated with an aqueous solution of hydrogen fluoride having a concentration of 0.01% to 40% at a temperature of 5 ° C to 70 ° C for 1 second to 20 minutes. Method of manufacturing wood. The aluminum material according to claim 2, containing hydrogen fluoride in a concentration of 0.01% to 40%, and one or two of nitric acid, sulfuric acid, phosphoric acid and chromic acid in total of these inorganic acids excluding hydrogen fluoride. 0.01
% To 40% in an aqueous solution containing 1% at a temperature of 5 ° C. to 70 ° C.
A method for producing an aluminum material for brazing, which comprises treating for 20 seconds to 20 minutes. The aluminum material according to claim 3,
0.01% for each coil or flat cut plate
Characterized by treatment with an aqueous solution of hydrogen fluoride having a concentration of ~ 40% at a temperature of 5 ° C to 70 ° C for 1 second to 20 minutes, and after the necessary processing, temporary assembly and brazing in a non-oxidizing atmosphere. And brazing method. The normal Al- as a brazing material according to claim 4.
A brazing product made of a Si-based alloy and using at least a part of an aluminum alloy containing Mg of more than 0.2% as a structural member, at least a brazing filler metal and a fillet in contact with the brazing filler metal. The surface of the member that contributes to the formation is 0.
An aqueous solution of hydrogen fluoride having a concentration of 01% to 40% is used at 5 ° C to 70 ° C.
After processing for 1 second to 20 minutes at a temperature of ℃, after the necessary processing,
A brazing method characterized by temporarily assembling and brazing in a nitrogen atmosphere. The formation of a fillet at least in contact with a brazing material and a brazing material of a brazed product brazed using an Al-Si brazing material containing Mg at all or less than 0.5% as a brazing material according to claim 5. The surface of the member that contributes to the
With a hydrogen fluoride aqueous solution having a concentration of 0.01% to 40%,
A brazing method, characterized in that the brazing is performed at a temperature of 70 ° C. for 1 second to 20 minutes, and after necessary processing, temporary assembly and vacuum brazing. The aqueous solution according to claim 6 contains hydrogen fluoride at a concentration of 0.01% to 40%, and one or two of nitric acid, sulfuric acid, phosphoric acid, and chromic acid is 0 in total of these inorganic acids excluding hydrogen fluoride. The brazing method according to claim 4, wherein the brazing method is an aqueous solution containing 0.01% to 40%. Is.

[0007]

In the present invention, the aluminum fluoride film is formed on the surface of the aluminum material. When this film is formed by treatment with an aqueous solution containing an inorganic acid such as nitric acid, sulfuric acid, phosphoric acid, chromic acid, etc., in addition to hydrogen fluoride, some nitrogen elements, sulfur elements, phosphorus elements and chromium elements may be contained. However, although other elements may be contained depending on the impurities of the aqueous solution used, a film mainly made of aluminum fluoride may be used. If the thickness of the aluminum fluoride film is less than 0.001 μm, the antioxidation effect is poor and the brazing property deteriorates. Even if a film having a thickness of more than 5 μm is formed, no further effect can be expected, and it takes a long time to process and productivity is deteriorated.
Therefore, the film thickness is set to 0.001 to 5 μm. Specifically, the method of forming this film is performed by using 0.01% aluminum material.
Treatment with an aqueous solution of hydrogen fluoride having a concentration of -40% at a temperature of 5 ° C to 70 ° C for 1 second to 20 minutes is performed by
The immersion method or the spray method may be used. The formation of an aluminum fluoride film on the surface of an aluminum material in a hydrogen fluoride aqueous solution is basically a substitution reaction, and the thickness is determined by the balance between etching and film growth. Considering industrial productivity, it is suitable that the concentration of the hydrogen fluoride aqueous solution is 0.01% to 40% and the treatment temperature is 5 to 70 ° C. If the treatment temperature is higher than 70 ° C. or the concentration exceeds 40%, etching proceeds but the film is hard to grow. On the other hand, if the treatment temperature is lower than 5 ° C. or the concentration is lower than 0.01%, neither etching nor film formation reaction proceeds. Further, in order to obtain the above-mentioned film thickness, the treatment time is 1 second at the shortest if the maximum concentration and the highest temperature are combined, but the treatment time is up to 20 minutes if the minimum concentration and the lowest temperature are combined. Therefore, the processing time is set to 1 second to 20 minutes. It should be noted that the treatment aqueous solution contains 0.01% to 4%.
In addition to 0% concentration of hydrogen fluoride, nitric acid, sulfuric acid, phosphoric acid, and chromic acid may be contained in an amount of 0.01% to 40% in total of these inorganic acids excluding hydrogen fluoride. . If these inorganic acids are included, the reaction with the aluminum material becomes more moderate. Therefore, it is better to add the above-mentioned inorganic acid in order to form a uniform film, and the more uniform the film, the better the brazing property. For efficiency of treatment, the aluminum material in the form of a coil or a flat cut plate is usually treated with hydrogen fluoride or an aqueous solution containing an inorganic acid such as nitric acid, sulfuric acid, phosphoric acid or chromic acid. However, if attention is paid to this point, this process may be performed on a temporarily assembled product after necessary processing such as cutting and molding.

According to the present invention, an aluminum alloy constituent member containing more than 0.2% of Mg, which is not possible with an ordinary non-corrosive fluoride type flux (even a brazing sheet core material, can be used as a brazing sheet). Other facing members may be brazed in a nitrogen atmosphere. This is because unlike the non-corrosive fluoride-based flux, the aluminum fluoride coating of the present invention has a high melting point and does not become a liquid phase but remains a solid phase near the brazing temperature.
This is because it is difficult to react with g and does not form MgF ₂ having poor wettability, so that the flow of wax is good. Further, in the vacuum brazing, if the treatment of the present application is applied, it is not necessary to forcefully contain the getter material in the brazing material, and the brazing material does not contain Mg at all or contains less than 0.5% of Al-Si.
Vacuum brazing is also possible using a system brazing material.

Before treatment with hydrogen fluoride or an aqueous solution containing an inorganic acid such as nitric acid, sulfuric acid, phosphoric acid or chromic acid, sodium silicate, sodium phosphate or sodium silicate is used to remove stains and oxide film on the surface of the material. Alkali degreasing such as sodium hydroxide and / or acid degreasing such as sulfuric acid or nitric acid is preferable. However, if the material is not contaminated, hydrogen fluoride or inorganic such as nitric acid, sulfuric acid, phosphoric acid or chromic acid is directly applied. You may process with the aqueous solution containing an acid.

The aluminum material on which such a film has been formed is then cut into a required size or subjected to a forming process such as pressing, and then temporarily assembled into a final product shape and brazed. Brazing is performed in a non-oxidizing atmosphere, that is, in a nitrogen atmosphere or vacuum. When brazing in a nitrogen atmosphere using this material, it is preferable that the oxygen concentration is 100 ppm or less and the dew point temperature is -20 ° C or less, and a normal Al-Si alloy is used as the brazing material. When vacuum brazing is performed using this material, it is preferable to set the atmospheric pressure to 10 ⁻⁴ Torr = 1.33 Pa or less, and as described above, Mg lower than that of a normal brazing material for vacuum brazing is used as the brazing material. Al-containing no Mg or less than 0.5% Mg
A Si-based brazing material can be used. Of course, even in vacuum brazing, an aluminum alloy containing more than 0.2% of Mg can be used as a structural member. The aluminum fluoride film may of course be formed on the entire surface of the aluminum material, but it is necessary to form the aluminum fluoride film on at least the brazing material and the surface of the member which contributes to the formation of the fillet in contact with the brazing material. Since this aluminum fluoride film is a thin and dense film, unlike ordinary non-corrosive fluoride fluxes for brazing, the film peels off even if it is formed in a coil or flat cut plate state and then molded and handled. Etc. are few. Also,
Film formation in the state of a coil or flat cut plate is a treatment on a flat surface, so it is easy to form a uniform film and most of the water can be removed with a squeezing roll, etc. High productivity. This aluminum fluoride remains in the solid phase at the brazing temperature and the coefficient of thermal expansion is different from that of the aluminum material, so the film is destroyed, and therefore an unoxidized aluminum surface appears and the wettability is improved, enabling brazing. it is conceivable that. Further, since it hardly volatilizes, it has no adverse effect on the brazing furnace and vacuum system when used for vacuum brazing, and in this case, the Mg content of the brazing material is less than 0.5% (including 0%). Brazing is possible.

The case of processing aluminum plates and strips before temporary assembly in the brazing process has been described above.
Even if the brazed product is temporarily assembled and then treated, the coating and drying efficiency is inferior, but other advantages can be enjoyed. Furthermore, since the only component consumed in the reaction is F and hydrogen fluoride is a single compound, K ₂ can be contacted with a treatment solution containing K and F ₂
Method for producing AlF ₅ (JP-A-60-83771;
As compared with JP-A-61-25984), the bath management is simpler, and the usual brazing non-corrosive fluoride-based flux (NOCOLOK) or K-F element is essential.
The cost is lower than those of JP-A-83771 and JP-A-61-25984.

[0012]

The present invention will be described in more detail based on the following examples. (Invention Examples 1 to 11) Aluminum clad material for brazing having a plate thickness of 1.0 mm (Al-10% Si / 3003 /
Al-10% Si, and 3003 core material with 0.3 Mg
%, 0.5%, 1.0% added) while unwinding the coil, degreasing the surface with an alkaline degreasing agent, then treating under the conditions shown in Table 1 and then washing with water / pure water After removing water with a squeezing roll, the coil was wound again while being dried with hot air of 100 ° C. After that, the pieces were cut into a required size, and cup-formed pieces were alternately assembled in four stages.

[0013]

[Table 1]

(Comparative Example 1) The same aluminum clad material for brazing as in Invention Example 1 was cut to a required size, cup-molded, degreased with a solvent (methyl ethyl ketone), and then assembled. Then, the assembly was dipped in a suspension of non-corrosive fluoride flux (Nocolok) dispersed in water, dried at 120 ° C. for 20 minutes, and coated with 3.0 g / m ² of flux. . (Comparative Example 2) A material which was treated in the same manner as Comparative Example 1 except that the same material as that of Invention Example 4 was used.

The appearance of each of the invention examples 1 to 11 and the comparative examples 1 to 2 was visually observed in a flat plate state before cutting, and the results are shown in Table 2 together with the evaluation of economical efficiency and efficiency. The evaluation criteria for the appearance before brazing are ◎ There is no unevenness after coating. ○ Area ratio of unevenness after film treatment is 5% or less. △ Uneven area ratio after coating treatment is more than 5 and 20% or less. × The uneven area ratio after coating treatment exceeds 20%. Economical evaluation before brazing is ◎ Equipment is simple and the running cost of a consumable chemical can be reduced. × The running cost of a consumable drug is high. Evaluation of efficiency before brazing ◎ Plates in a coiled state can be continuously and quickly processed. × Inefficient in temporary assembly processing. Further, the temporary heat exchanger assembly of each model cup was replaced with nitrogen at atmospheric pressure to obtain an oxygen concentration of 50 ppm in the furnace and a dew point temperature of -40.
C., brazing temperature 600.degree. C., brazing for 10 minutes in a nitrogen atmosphere, and visually observing the brazability of the brazed product when brazing immediately after the treatment and after brazing after leaving the coating for a while. At the same time, the appearance and surface treatment properties were evaluated only when the brazing was performed immediately after. As for surface treatment, each brazing material should be treated with 45% Alodine # 1200 solution.
After dipping at 2 ° C. for 2 minutes for chemical conversion treatment, dipping coating was performed using an acrylic paint and baking and drying. Then, a tape peeling test was carried out by marking 100 squares of 1 mm each on the flat surface of the brazed product, 10 squares on each side, 10 squares on each side, and evaluated by the number of squares remaining on the coating. The results are shown in Table 2. Evaluation of appearance after brazing is ◎ No unevenness after brazing. ○ The uneven area ratio after brazing is 5% or less. △ The uneven area ratio after brazing exceeds 5 and is 20% or less. × The uneven area ratio after brazing exceeds 20%. Evaluation of brazing property: ◎ Fillet formation and brazing flow are very good. ○ Good flow of fillet formation and wax. △ Fillet formation and wax flow are slightly inferior. × Incomplete flow of fillet formation and wax. The evaluation of the furnace contamination was rated as ⊚ when there was no flux dripping after brazing for 5 batches in succession, and as × when flux dripping was observed.

[0016]

[Table 2]

Comparative Example 1 is inferior in economic efficiency and efficiency before brazing due to the treatment after the temporary assembly with the usual suspension of the non-corrosive fluoride type flux, and the flux coating is not uniform. Furthermore, since this flux becomes a liquid phase during brazing, the appearance after brazing becomes uneven, and a film is formed even after brazing and does not fall off even after washing, so surface treatability (coating adhesion) Is inferior. When the same flux as in Comparative Example 2 is used, but when it is used for an aluminum material containing Mg in the core material, in addition to the drawbacks of Comparative Example 1, the flux and Mg react and the wettability deteriorates, resulting in poor fillet formation. Inventive Examples 1 to 6 are hydrogen fluoride aqueous solutions (hereinafter referred to as HF).
However, the appearance before brazing is a little inferior and the brazing property is a little inferior because the reaction is severe and the coating is not uniform, but it is at a sufficiently practical level. In particular, Invention Example 6 has a large amount of Mg in the core material and does not contain an inorganic acid other than HF, so that the brazing property is slightly inferior, but it is at a practical level. All of the other invention examples evaluated were good, and invention examples 7 to 11 containing an inorganic acid in addition to HF were particularly good in appearance and brazability after brazing. From the above results, the brazing aluminum material of the present invention having the aluminum fluoride coating formed by the precoating treatment (treatment in the state of the coil or the flat cut plate) has a good surface appearance and a uniform coating. Has been formed. It was confirmed that the product of the present invention not only achieved good nitrogen atmosphere brazing, but also that the obtained brazed product had a good surface condition.

(Invention Examples 12 to 15) While unwinding the coil of the same aluminum clad material for brazing as in Invention Example 1, the surface was degreased with an alkaline degreasing agent, then treated under the conditions shown in Table 3 and then washed with water. After washing with pure water, water was removed with a squeezing roll, and then the coil was wound again while being dried at 100 ° C. After that, the pieces were cut into a required size, and cup-formed pieces were alternately assembled in four stages.

[0019]

[Table 3]

(Comparative Example 3) Aluminum clad material for vacuum brazing (Al-10% Si-) having a plate thickness of 1.0 mm
1.2% Mg / 3003 / Al-10% Si-1.2%
Mg) was cut to a required size, cup-molded, degreased with a solvent (methyl ethyl ketone), and then assembled.

The molded articles obtained in each of the above-mentioned examples subjected to the pre-coating treatment, the post-coated comparative examples and the comparative example of the Mg-containing brazing material were evaluated in terms of appearance, economy and efficiency. Also, each heat exchanger temporary assembly of the model cup was brazed by heating it in a vacuum furnace in 5 × 10 ⁻⁵ Torr at 600 ° C. for 3 minutes.

For each brazed product obtained as described above, the brazing properties of the brazed product immediately after the treatment and the brazing properties of the brazing product after being left for a while after the film treatment were visually observed and the appearance was observed only when the brazing product was brazed immediately after. Then, the surface treatment property was evaluated. As for surface treatment, each brazed product is Alodine # 1
After dipping in 200 solution at 45 ° C. for 2 minutes for chemical conversion treatment, dip coating was performed using acrylic paint and baking and drying were performed. Then, on the flat surface of the brazed product, 1
A tape peeling test was carried out with 100 squares each having 10 squares in each of the vertical and horizontal directions, and the number of squares remaining in the coating film was evaluated. Further, the contamination of the vacuum furnace was also evaluated by the following method. That is, a glass plate was erected in the furnace to treat a certain amount of the test material and then taken out, and the adhesion of Mg was observed. The case where the adhesion was not recognized was marked with ⊚, and the case where the adhesion was recognized was marked with x. The results are shown in Table 4.

[0023]

[Table 4]

In Comparative Example 3, the getter for normal vacuum brazing is a material containing Mg in the brazing material, so the brazing property is good, but the Mg contaminates the furnace. On the other hand, in the invention examples, all the evaluated items are good. From the above results, the brazing aluminum material of the present invention having the aluminum fluoride film formed by the precoating treatment not only achieves good brazing even in vacuum brazing using a brazing material containing no Mg, It was confirmed that the obtained brazed product had a good surface condition.

[0025]

[Effect] The present invention enables formation of a chemical conversion treatment film in a flat material shape.
Since it is a film that remains in a solid phase during brazing with little change over time, it has many advantages as described below. That is, in the non-corrosive fluoride-based flux brazing performed in A nitrogen atmosphere. Eliminate the productivity hindrance factors that result from flux application and drying after assembling into a complicated product shape. 2. When a continuous furnace is used, the brazing property is prevented from deteriorating due to water being brought into the brazing furnace from the drying furnace. Due to the tendency to apply a large amount of flux,
3. Avoid all the disadvantages of brazing furnace contamination, cleaning of the brazing furnace for this purpose, increased frequency of overhaul and increased costs. Furthermore, it eliminates the poor appearance of the product surface after brazing and the adverse effects on the subsequent surface treatment due to the flux becoming a liquid phase at the brazing temperature. 5. No need for large-scale equipment for processing, The Mg-containing aluminum alloy can be used for the constituent members.

Furthermore, in the case of B vacuum brazing: 1. Contamination of the brazing furnace is prevented by enabling brazing without adding a large amount of getter material such as Mg to the brazing material. Alternatively, the inefficient surface treatment just before brazing is not required, and the production efficiency can be improved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C23C 22/56 (56) References JP-A-2-89590 (JP, A) JP-B 4- 54560 (JP, B2)

Claims (6)

[Claims] 1. An aluminum material is treated with an aqueous solution of hydrogen fluoride having a concentration of 0.01% to 40% at a temperature of 5 ° C. to 70 ° C. for 1 second to 2 seconds.
A method for producing an aluminum material for brazing, which comprises treating for 0 minutes. 2. An aluminum material containing hydrogen fluoride at a concentration of 0.01% to 40% and containing nitric acid, sulfuric acid, phosphoric acid or chromic acid.
The total amount of these inorganic acids excluding hydrogen fluoride is 0.1.
A method for producing an aluminum material for brazing, which comprises treating the aluminum material for brazing at a temperature of 5 ° C. to 70 ° C. for 1 second to 20 minutes with an aqueous solution containing 01% to 40%. 3. An aluminum material, in the form of a coil or a flat cut plate, is treated with an aqueous solution of hydrogen fluoride having a concentration of 0.01% to 40% at a temperature of 5 ° C. to 70 ° C. for 1 second to 20 minutes. The brazing method is characterized in that after the necessary processing, it is temporarily assembled and then brazed in a non-oxidizing atmosphere. 4. A brazed product comprising a normal Al—Si alloy as a brazing material and an aluminum alloy containing Mg exceeding 0.2% as a structural member at least in part. , At least the brazing material and the surface of the member which is in contact with the brazing material and contributes to the formation of the fillet, in the state of a coil or a flat cutting plate, respectively, is 0.01% to 40%.
A brazing method, which comprises: treating with an aqueous solution of hydrogen fluoride having the above concentration at a temperature of 5 ° C. to 70 ° C. for 1 second to 20 minutes, and then, after necessary processing, temporarily assembling and brazing in a nitrogen atmosphere. 5. Mg as a brazing filler metal, or 0.5%
A brazed product brazed using an Al-Si brazing material containing less than less than at least the brazing material and the surface of the material which contributes to the formation of the fillet in contact with the brazing material are in the state of a coil or a flat cut plate, respectively. And 0.01% to 4
A brazing method, characterized in that a hydrogen fluoride aqueous solution having a concentration of 0% is treated at a temperature of 5 ° C. to 70 ° C. for 1 second to 20 minutes, and after necessary processing, temporary assembly and vacuum brazing are performed. 6. An aqueous solution containing hydrogen fluoride in a concentration of 0.01% to 40%, and one or two of nitric acid, sulfuric acid, phosphoric acid and chromic acid.
The total amount of these inorganic acids excluding hydrogen fluoride is 0.01% to
The brazing method according to claim 4, wherein the brazing method is an aqueous solution containing 40%.