JP2510950B2 - Aluminum material for brazing, manufacturing method thereof, 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, the generated moisture is brought into the brazing furnace if the process is not performed for a sufficient time, 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. Also, as a nitrogen atmosphere brazing method, a brazing material containing no gettering agent such as Mg is clad to form a laminated plate, which is washed with dilute hydrofluoric acid and then assembled into a heating furnace to reduce residual oxygen with a vacuum pump. After that, a method is proposed in which nitrogen gas is sealed and heated (Japanese Patent Application Laid-Open No. 56-50780).
issue). However, even though dilute hydrofluoric acid is used, hydrofluoric acid is very reactive and corrodes the surface of the aluminum material, so that the surface may be roughened and the fillet formation may become uneven.

Further, by vacuum brazing, the brazing material is Mg
A method in which the oxide film is previously removed with sodium hydroxide or sulfuric acid before brazing with a material without addition of aluminum (JP-A-51-132).
No. 148) is also proposed. However, since the aluminum surface is a new surface and is active in the above method, if the oxide film is left for a long time after the oxide film is removed, the oxide film grows and the brazing property is poor unless it is treated immediately before brazing. There is a drawback that. Therefore, since the continuous treatment with the coil cannot be performed, the efficiency is poor and the cost is high.

[0006]

Therefore, the inventor of the present application has
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.

[0007]

As a result, the present inventors have found that when aluminum materials are treated with ammonium fluoride or an aqueous solution containing an inorganic acid such as nitric acid, sulfuric acid, phosphoric acid, or chromic acid, they are simultaneously etched and fluorinated. The present invention has been completed by finding that an aluminum film is formed and that this film has preferable characteristics. That is, according to claim 1, the aluminum fluoride film is formed on the surface of the aluminum material by 0.0
An aluminum material for brazing, which is formed to have a thickness of 1 μm to 5 μm. The aluminum material for brazing according to claim 2, wherein the aluminum material is treated with an ammonium fluoride aqueous solution having a concentration of 0.01% to 40% at a temperature of 5 ° C to 70 ° C for 1 second to 20 minutes. Production method. The aluminum material according to claim 3, containing ammonium fluoride in a concentration of 0.01% to 40%, and one or more of nitric acid, sulfuric acid, phosphoric acid and chromic acid in total of these inorganic acids excluding fluoride. 0.0
A method for producing an aluminum material for brazing, which comprises treating with an aqueous solution containing 1% to 40% at a temperature of 5 ° C. to 70 ° C. for 1 second to 20 minutes. The aluminum material according to claim 4, which is in the form of a coil or a flat cut plate, is treated with an ammonium fluoride aqueous solution having a concentration of 0.01% to 40% at a temperature of 5 ° C to 70 ° C for 1 second to 20 minutes. Then
After that, after the necessary processing, the brazing method is characterized by performing temporary assembly and brazing in a non-oxidizing atmosphere. A brazed article according to claim 5, wherein a normal Al-Si alloy is used as a brazing material, and an aluminum alloy containing Mg exceeding 0.2% is used as at least a part as a structural member. , At least the brazing filler metal and the surface of the component that is in contact with the brazing filler metal and contributes to the formation of the fillet, in the state of a coil or a flat cut plate, with an ammonium fluoride aqueous solution having a concentration of 0.01% to 40% at 5 ° C to 1 second to 2 at a temperature of 70 ° C
A brazing method characterized by performing 0 minute treatment, then performing necessary processing, temporarily assembling, and brazing in a nitrogen atmosphere. The formation of a fillet at least in contact with the brazing material and the brazing material of the brazed product according to claim 6, which is brazed using an Al-Si based brazing material containing Mg at all or less than 0.5% as the brazing material. The surface of the member that contributes to the above is treated with an ammonium fluoride aqueous solution having a concentration of 0.01% to 40% at a temperature of 5 ° C to 70 ° C for 1 second to 20 minutes, respectively in the state of a coil or a flat cut plate, A brazing method characterized by temporarily assembling and vacuum brazing after necessary processing. The aqueous solution according to claim 7 contains ammonium fluoride in a concentration of 0.01% to 40%, and one or more of nitric acid, sulfuric acid, phosphoric acid and chromic acid are added in a total amount of 0. 01% to 4
The brazing method according to claim 4, wherein the brazing method is an aqueous solution containing 0%. Is.

[0008]

When the thickness of the aluminum fluoride film is less than 0.01 μm, the anti-oxidation 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 0.01 to 5 μm. In addition, this film is composed of ammonium fluoride or nitric acid, as described below.
When produced by treatment with an aqueous solution containing an inorganic acid such as sulfuric acid, phosphoric acid, or chromic acid, some nitrogen elements may be contained, and depending on the aqueous solution used, other elements may be contained. Any film made of aluminum fluoride may be used. Specifically, the method of forming this film involves treating an aluminum material with an ammonium fluoride aqueous solution having a concentration of 0.01% to 40% at a temperature of 5 ° C to 70 ° C for 1 second to 20 minutes. The treatment method may be an immersion method or a spray method. The formation of an aluminum fluoride film on the surface of an aluminum material in an aqueous solution of ammonium fluoride is
It 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 ammonium 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,
With the combination of maximum concentration and maximum temperature, the processing time is as short as 1
It only takes seconds, but if the combination of the minimum concentration and the minimum temperature is used, the processing time will take up to 20 minutes. Therefore, processing time is from 1 second to 20
Minutes. In addition, 0.01% to 40% in the aqueous solution for treatment
In addition to ammonium fluoride having a concentration of 0.01% to 40% in total of one or more kinds of nitric acid, sulfuric acid, phosphoric acid and chromic acid, excluding fluoride, in total.
If these inorganic acids are included, the reaction with the aluminum material becomes more moderate. For efficiency of treatment, an aluminum material in the form of a coil or a flat cut plate is usually treated with ammonium 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 a usual non-corrosive fluoride-based flux (even if a brazing sheet core material, it faces a brazing sheet, The component 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 with poor wettability, and the flow of the brazing material 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 ammonium 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 in order to remove dirt and oxide film on the surface of the material. It is preferable to perform alkaline degreasing such as sodium hydroxide and / or acid degreasing such as sulfuric acid and nitric acid, but when the material is not dirty, ammonium fluoride or inorganic such as nitric acid, sulfuric acid, phosphoric acid or chromic acid is directly added. 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 dense, once formed, it prevents new oxidation of the aluminum surface even after a long time.
Also, unlike ordinary non-corrosive fluoride fluxes for brazing, this film is a thin and dense film, so there is little peeling of the film even if it is formed in the state of a coil or flat cut plate and then molded and handled. . In addition, since the film formation in the coil or flat cut plate state is a treatment on a flat surface, it is easy to form a uniform film, and most of the water can be removed with a squeezing roll, etc. It is very productive. This aluminum fluoride remains in the solid phase at the brazing temperature and the coefficient of thermal expansion is different from that of aluminum, so the film is destroyed, and therefore an unoxidized aluminum surface appears and the wettability improves and brazing can be performed. Conceivable. Further, since it hardly volatilizes, it has no adverse effect on the brazing furnace and the vacuum system even when used for vacuum brazing, and in this case, the Mg content of the brazing material is 0.5%.
Even if less than (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. Since ammonium fluoride used in the present invention is less reactive than hydrofluoric acid, a more uniform film is formed on the aluminum surface than hydrofluoric acid, and the appearance and fillet forming ability are good. Furthermore, since the only component consumed in the reaction is F and ammonium fluoride is a single compound, it can be contacted with a treatment solution containing K and F to obtain K.
₂ Method for producing AlF ₅ (Japanese Patent Laid-Open No. 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 10) 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 Examples 1 and 2) While rewinding the coil of the same aluminum clad material for brazing as in Inventive Example 1, the surface was 40 ° C. in 1% hydrofluoric acid aqueous solution (Comparative Example 1) or 1% hydrofluoric acid + 2% fluorocarbon. After being treated with an aqueous solution of potassium iodide (Comparative Example 2), washed with water, washed with pure water, water was removed with a squeeze roll, and then the coil was wound again while being dried with warm air at 100 ° C. After that, the pieces were cut into a required size, and cup-formed pieces were alternately assembled in four stages. (Comparative Example 3) The same aluminum clad material for brazing as in Inventive Example 1 was cut to a required size, cup-molded, degreased with a solvent (methyl ethyl ketone), and then assembled. Then, the assembly is immersed in a suspension of a non-corrosive fluoride flux (Nocolock) dispersed in water, and then 120 ° C.
It was dried for 20 minutes and a flux of 3.0 g / m ² was applied. (Comparative Example 4) A material treated in the same manner as in Comparative Example 3 except that the same material as that of Inventive Example 4 was used.

The appearance of each of the invention examples 1 to 10 and the comparative examples 1 to 4 was visually observed in a flat plate state before cutting, and the results are shown in Table 2 together with the evaluations 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. Table 2 shows the results. 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]

In Comparative Example 1 treated with a highly reactive HF aqueous solution, the surface of the aluminum plate was melted and the appearance before brazing became uneven due to a non-uniform film, so that the appearance after brazing was also inferior. If the brazing is carried out immediately after the film is treated, the brazing is not uniform, but if the brazing property is long, the brazing becomes poor. In Comparative Example 2 which was treated with a mixed aqueous solution of HF and KF, K contained in the film and became a liquid phase during brazing, resulting in a pattern-like uneven appearance after brazing, and a film was formed even after brazing and was cleaned. Even if it does not fall off, the surface treatment property (coating film adhesion) is poor. Comparative Example 3 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 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. The same flux as in Comparative Example 3 was used, but when used in an aluminum material containing Mg in the core material, Comparative Example 3
In addition to the above-mentioned drawback, the flux and Mg react to deteriorate wettability, resulting in poor fillet formation. On the other hand, in Inventive Example 5, since the amount of Mg in the core material is large, the brazing property is slightly inferior, but it is at a practical level. In other invention examples, all the evaluated items are good.
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 brazing in a nitrogen atmosphere without aging even after being left for a long time after the film treatment, but also confirmed that the obtained brazed product had a good surface condition. I got it.

(Invention Examples 11 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 5) While rewinding the same coil of brazing aluminum clad material as in Invention Example 1,
The surface was treated with a 1% aqueous solution of hydrofluoric acid, washed with water, washed with pure water, removed of water with a squeeze roll, and then rewound on the coil 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.

(Comparative Example 6) While rewinding the same coil of brazing aluminum clad material as in Invention Example 1,
The surface was treated with a 10% NaOH aqueous solution at 40 ° C. for 60 seconds, then washed with water, desmutted with 20% HNO ₃ at 40 ° C. for 30 seconds, washed with water, washed with pure water, and then removed with a squeezing roll to remove water, then 100 The coil was rewound while drying at ℃. After that, the pieces were cut into a required size, and cup-formed pieces were alternately assembled in four stages.

(Comparative Example 7) 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 appearance, economy and efficiency of the molded articles obtained in the above-mentioned pre-coated examples, post-coated comparative examples and Mg-containing brazing filler metal comparative examples were evaluated. 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 above, visually observe the brazing property when brazing immediately after treatment and when brazing after leaving for a while after film treatment, and only when brazing immediately after appearance, surface treatment The sex was evaluated. As for surface treatment, each brazed product has Alodine # 120
After performing a chemical conversion treatment by immersing it in a 0 solution at 45 ° C. for 2 minutes, an acrylic coating was used for dip coating and baking and drying. Then, 1m on the coating surface in the flat part of the brazed product
A tape peeling test was carried out by marking 100 m-th squares, 10 each in the vertical and horizontal directions, and evaluated by the number of squares remaining in the coating film. 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.

[0024]

[Table 4]

In Comparative Example 5, which was brazed in a nitrogen atmosphere and treated with the same highly reactive HF aqueous solution as in Comparative Example 1, the surface of the aluminum plate was melted and became uneven due to a non-uniform film, and therefore, after vacuum brazing. The appearance is also inferior. If the brazing is carried out immediately after the film is treated, the brazing is not uniform, but if the brazing property is long, the brazing becomes poor. Comparative Example 6, which was treated with an aqueous solution of NaOH and desmutted with HNO ₃ , was able to be coiled and the original oxide film was dissolved and removed. Therefore, the economy, efficiency, and appearance before brazing were good. Although brazing is good, if the standing time before brazing becomes long, an oxide film grows and the brazeability deteriorates. Comparative Example 7 is a material that contains Mg in the brazing material as a getter for normal vacuum brazing, and thus has good brazing properties, 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.

[0026]

[Effect] The present invention enables formation of a chemical conversion treatment film in the form of a flat material, and because this chemical conversion treatment film 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. 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 C23C 22/56 (56) Reference JP-A-2-89590 (JP, A) Special features Kaihei 1-99794 (JP, A) JP-B 4-54560 (JP, B2) JP-B 7-102451 (JP, B2)

Claims (7)

(57) [Claims] 1. An aluminum material for brazing, characterized in that an aluminum fluoride film is formed on the surface of the aluminum material in a range of 0.01 μm to 5 μm. 2. An aluminum material for brazing, which is treated with an aqueous solution of ammonium fluoride having a concentration of 0.01% to 40% at a temperature of 5 ° C. to 70 ° C. for 1 second to 20 minutes. Production method. 3. An aluminum material containing ammonium fluoride at a concentration of 0.01% to 40%, and one or more of nitric acid, sulfuric acid, phosphoric acid and chromic acid in total of these inorganic acids excluding fluoride. An aqueous solution containing 0.01% to 40% and 5 ° C to 7 ° C.
A method for producing an aluminum material for brazing, which comprises treating at a temperature of 0 ° C. for 1 second to 20 minutes. 4. An aluminum material, in the form of a coil or a flat cut plate, is treated with an aqueous solution of ammonium 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. 5. 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: performing treatment with an aqueous solution of ammonium fluoride having a concentration of 5 ° C. to 70 ° C. for 1 second to 20 minutes, then performing necessary processing, then temporarily assembling and brazing in a nitrogen atmosphere. 6. Mg as a brazing filler metal at all or 0.5%
A brazed product brazed with 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
Aqueous ammonium fluoride solution with a concentration of 0%, 5 ° C to 70 ° C
A brazing method, characterized in that the brazing method is carried out at a temperature of 1 second to 20 minutes, after which necessary processing is performed, and then temporary assembly and vacuum brazing are performed. 7. Aqueous solution containing ammonium fluoride in a concentration of 0.01% to 40%, and one of nitric acid, sulfuric acid, phosphoric acid and chromic acid.
The brazing method according to claim 4, wherein the brazing method is an aqueous solution containing 0.01% to 40% in total of these inorganic acids excluding fluorides or two or more species.