JPH091390A - Synthesis of flux for soldering aluminum - Google Patents

Abstract

PURPOSE: To produce Al brazed products with which long-term reliability is assured by adding a specific ratio of zinc, potassium hydroxide, etc., at a specific temp. into a specific aq. soln to react these materials. CONSTITUTION: Aluminum hydroxide is dispersed into the water. Hydrofluoric acid is then added under stirring and cooling to the dispersion to synthesize an aq. fluoroaluminate soln. At this time, the content of the aluminum hydroxide is specified to 2 to 40mol% and that of the hydrofluoric acid to 10 to 80mol% and the reaction temp. is specified to 10 to 120 deg.C. Either of both of the metal zinc and oxide are thereafter added thereto and in succession, total 5 to 50mol% of one or >=2 kinds of potassium hydroxide, potassium carbonate, potassium fluoride and acidic potassium fluoride are added to the soln. at 10 to 150 deg.C temp. to effect reaction. As a result, stages are drastically shortened in flux production.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention makes it possible to join aluminum-based materials by brazing by forming zinc fluoride in the brazing flux of aluminum-based materials, and at the same time diffuse zinc into the aluminum-based materials. The present invention relates to a synthesis method for obtaining a flux powder by fluorinating a flux intended to at least form a sacrificial corrosion layer by a single wet synthesis using hydrofluoric acid.

[0002]

2. Description of the Related Art Conventionally, for brazing aluminum-based materials, aluminum-silicon alloys having a melting point slightly lower than that of the materials have been mainly used as a brazing material.
Further, in order for the brazing material to bond well with the material, the melting point lower than that of the brazing material is removed for the purpose of removing dirt and oxide film on the surface of the material and preventing reoxidation of the surface during brazing. A flux that is stable to the material is used.

As a flux used for aluminum materials, potassium tetrafluoroaluminate (KAl
F ₄ ) and potassium tetrafluoroaluminate (KAl
F ₄ ) and potassium pentafluoroaluminate (K ₂ Al
It is known that a mixture of F ₅ ) or a mixture of potassium tetrafluoroaluminate (KAlF ₄ ) and potassium hexafluoroaluminate (K ₃ AlF ₆ ) is useful. These complex salts can be obtained by mixing and dissolving potassium fluoride (KF) and aluminum fluoride (AlF ₃ ), or reacting them with water interposed. In addition, JP-A-60-170596
The publication describes that aluminum hydroxide (Al (OH) ₃ ), hydrofluoric acid (HF) and potassium hydroxide (KOH) can also be synthesized.

Since these fluxes are used in a non-oxidizing atmosphere, are essentially inert to metallic aluminum, have no hygroscopicity, and require no post-cleaning, they are fluxes for brazing aluminum-based materials. Has excellent properties.

However, when aluminum-based materials are brazed using these fluxes, the obtained products, for example, automobile condensers and radiators composed of tubes and fins, have holes formed by chlorine-based salts such as snow-melting salt or seawater. It is susceptible to erosion, and the tube may cause through pitting corrosion.

In order to prevent this phenomenon, a method of forming a zinc layer on the surface of the tube material has been adopted. However, the method of forming the zinc layer on the surface of the aluminum material requires a special process such as metal vapor deposition or metal spraying, which is one of the causes of cost increase. Further, it is difficult to control the amount of zinc adhered, and zinc adhered in a large amount preferentially corrodes, so that the tubes and the fins may peel off at an early stage, and there is a problem in the reliability of the capacitor.

As a method of forming zinc layer on the surface of aluminum material by allowing zinc to be present in the flux, a method of using potassium fluoroaluminate mixed with zinc fluoride or zinc oxide (JP-A-59) 232694) and a method of using zinc, zinc oxide, and zinc fluoride mixed with a mixture of potassium tetrafluoroaluminate and aluminum fluoride (JP-A-60-37293).

[0008]

However, in those methods, first, a step of synthesizing potassium fluoroaluminate or a mixture of potassium tetrafluoroaluminate and aluminum fluoride, drying and pulverizing, and zinc, zinc oxide, After mixing with zinc fluoride, there is a step of drying and crushing,
It has the drawback of increasing the number of steps until the flux is obtained, which is the main cause of the cost increase of the flux. In addition, the flux obtained by the above method has a brazing property and Z
The uniformity of the diffusion amount of n and the zinc concentration was insufficient, and it was not suitable for use in actual operation.

[0009]

The present invention reduces the number of manufacturing steps of the above zinc-containing flux to reduce the cost of the flux, and also provides a flux having excellent brazing property and Zn diffusibility which can be used in actual operation. The present invention has been made for the purpose of providing a method for obtaining a flux mixture containing zinc by a single wet synthesis. In addition, the process can be significantly shortened, and the raw materials used can be inexpensive industrial materials that are generally distributed. Therefore, it is possible to manufacture aluminum brazed products at low cost and with long-term reliability. did.

That is, the first of the synthetic methods of the present invention is 2-40% mol of aluminum hydroxide (hereinafter mol% is simply referred to as%).
And hydrofluoric acid 20 to 80% are reacted at a temperature of 10 to 120 ° C., and 0.1 to 40% of one or two kinds of zinc and zinc oxide, potassium hydroxide, potassium carbonate and potassium fluoride are added to this aqueous solution. And a total of 5 to 50% of one or more kinds of acidic potassium fluoride at a temperature of 10 to 150 ° C. for reaction.

The second of the synthetic methods of the present invention is to react 0.1 to 40% of one or two of zinc and zinc oxide with 20 to 80% of hydrofluoric acid at a temperature of 10 to 120 ° C. Add 2 to 40% aluminum hydroxide to the aqueous solution and add 10 to 120 ° C.
At a temperature of 10 to 150 ° C, and then 5 to 50% in total of one or more of potassium hydroxide, potassium carbonate, potassium fluoride and acidic potassium fluoride is added at a temperature of 10 to 150 ° C to react. It is a feature.

The third synthetic method of the present invention is a total of 5 to 50% of one or more of potassium hydroxide, potassium carbonate, potassium fluoride and acidic potassium fluoride and hydrofluoric acid of 20 to 80%. % At the temperature of 10-120 ℃, add 2-40% aluminum hydroxide to this aqueous solution,
The reaction is performed at a temperature of 120 ° C., and then 0.1 to 40% of one or two types of zinc or zinc oxide is added at a temperature of 10 to 150 ° C. for reaction.

Further, the fourth method of the present invention is that one or more of potassium hydroxide, potassium carbonate, potassium fluoride and acidic potassium fluoride, 5 to 50% in total, and hydrofluoric acid, 20 to 80%. % At a temperature of 10 to 120 ° C,
Add one or two of zinc and zinc oxide to this aqueous solution.
It is characterized in that 0.1 to 40% is added and reacted, and then 2 to 40% aluminum hydroxide is added and reacted at a temperature of 10 to 150 ° C.

[0014]

The raw materials used in the present invention are aluminum hydroxide (Al (OH) ₃ ), hydrofluoric acid (HF), metallic zinc (Zn) and / or zinc oxide (ZnO), potassium hydroxide. (KOH), potassium carbonate (K ₂ C
O ₃ ), potassium fluoride (KF) and one or more kinds of acidic potassium fluoride (KHF ₂ ), and there are no special raw materials.

The reason for limiting the blending amount of these raw materials used will be described below. 2-40% aluminum hydroxide,
The hydrofluoric acid content of 20 to 80% is a necessary amount for producing a fluoroaluminic acid aqueous solution, and in compositions other than the above range, aluminum or fluorine is excessive or insufficient, and there are raw materials that do not contribute to the reaction. Because these are wasted.

One or two of zinc and zinc oxide
The reason why the content is 0.1 to 40% is that if the content is less than 0.1%, the zinc content in the flux is insufficient and it becomes impossible to form a sacrificial corrosion layer on the surface of the aluminum material. Further, even if added in excess of 40%, the anticorrosion effect due to sacrificial corrosion saturates, and the melting point of the flux rises, so the brazeability deteriorates.

The reason for limiting the total amount of one or more of potassium hydroxide, potassium carbonate, potassium fluoride and acidic potassium fluoride to 5 to 50% is that the melting point of the flux is higher than that of the brazing material. This is to lower it. However, if the amount of potassium mixed is less than the above, the melting point is not sufficiently lowered, and brazing using an aluminum-silicon brazing material becomes difficult. On the other hand, when the amount of potassium mixed exceeds the above amount, potassium becomes excessive, the melting point of the flux rises again, and the brazing property deteriorates.

Further, as a composition for obtaining a sacrificial corrosion layer sufficient for good brazing property and aluminum corrosion protection, aluminum hydroxide is 3 to 20% and hydrofluoric acid is 50 to 50%.
75% and one or two of zinc and zinc oxide 0.5 to
20% and 10% to 30% of one or two kinds of potassium hydroxide and potassium carbonate, or aluminum hydroxide 4 to 30
%, Hydrofluoric acid 30-75%, zinc and zinc oxide 1
0.5 to 20% of seeds or 2 and potassium fluoride 10 to 30
%, Or aluminum hydroxide 5 to 35%, hydrofluoric acid 20 to 60%, one or two kinds of zinc and zinc oxide 0.5 to 30%, and potassium acid fluoride 20 to 45% Is desirable.

Next, the first procedure of the synthesis method of the present invention will be described in more detail. First, aluminum hydroxide is dispersed in water, and hydrofluoric acid is added while stirring and cooling to synthesize an aqueous fluoroaluminate solution. At this point, if the temperature of the synthesis liquid is less than 10 ° C, the reaction proceeds too slowly, and if it exceeds 120 ° C, the aluminum fluoride trihydrate (β, which is insoluble in water during the operation of adding the zinc source and the potassium source (β -AlF ₃ · 3H
₂ O) precipitates. This fluoroaluminic acid aqueous solution is
Β-AlF ₃ · 3.5H ₂ O or α soluble in water
It can be obtained by dissolving -AlF ₃ .3H ₂ O in hydrofluoric acid, but all of them are unstable, and the handling temperature and time are limited, which is not common in industrial handling.

Thereafter, either or both of metallic zinc and zinc oxide are added, followed by potassium hydroxide, potassium carbonate,
One or more of potassium fluoride and acidic potassium fluoride are added. At this point, if the temperature of the synthesis liquid is less than 10 ° C, the reaction proceeds too slowly, and if it exceeds 150 ° C, it becomes fine particles and the filterability during solid-liquid separation deteriorates.

In the second procedure of the present invention, first, zinc or zinc oxide is dispersed in water, and hydrofluoric acid is added while stirring and cooling to synthesize an aqueous solution. At this point, the temperature of the synthetic solution is
If the temperature is lower than 10 ° C, the reaction proceeds too slowly, and if it exceeds 120 ° C, the aqueous solution bumps and the synthesis becomes dangerous. Next, aluminum hydroxide is added and reacted with the aqueous solution. At this point, if the temperature of the synthesis solution is less than 10 ° C, the reaction proceeds too slowly, and if it exceeds 120 ° C, the aqueous solution bumps and the synthesis becomes dangerous. Subsequently, potassium hydroxide, potassium carbonate, potassium fluoride or potassium acid fluoride is added. At this point, if the temperature of the synthesis liquid is less than 10 ° C, the reaction proceeds too slowly, and if it exceeds 150 ° C, it becomes fine particles and the filterability during solid-liquid separation deteriorates.

In the third procedure of the present invention, first, potassium hydroxide, potassium carbonate, potassium fluoride, or potassium acid fluoride is reacted with hydrofluoric acid to synthesize an aqueous solution. At this point, if the temperature of the synthesis solution is less than 10 ° C, the reaction proceeds too slowly, and if it exceeds 120 ° C, the aqueous solution bumps and the synthesis becomes dangerous. Next, aluminum hydroxide is added and reacted with the aqueous solution. At this point, if the temperature of the synthesis solution is less than 10 ° C, the reaction proceeds too slowly, and if it exceeds 120 ° C, the aqueous solution bumps and the synthesis becomes dangerous. Subsequently, metallic zinc or zinc oxide is added. At this point, if the temperature of the synthesis liquid is less than 10 ° C, the reaction proceeds too slowly, and if it exceeds 150 ° C, it becomes fine particles and the filterability during solid-liquid separation deteriorates.

In the fourth procedure of the present invention, first, potassium hydroxide, potassium carbonate, potassium fluoride or acidic potassium fluoride is reacted with hydrofluoric acid to synthesize an aqueous solution. At this point, if the temperature of the synthesis solution is less than 10 ° C, the reaction proceeds too slowly, and if it exceeds 120 ° C, the aqueous solution bumps and the synthesis becomes dangerous. Next, metallic zinc or zinc oxide is added to synthesize a transparent aqueous solution. Subsequently, aluminum hydroxide is added. At this point, if the temperature of the synthesis liquid is less than 10 ° C, the reaction proceeds too slowly, and if it exceeds 150 ° C, it becomes fine particles and the filterability during solid-liquid separation deteriorates.

[0024]

EXAMPLES Table 1 shows the invention samples No. 1 to No. 32 and the comparative sample No.
The compounding ratios of the raw materials 1 to 14 are shown below. And in any of these raw materials, first put aluminum hydroxide and water in a polypropylene beaker, add hydrofluoric acid while stirring and cooling and hold at about 90 ° C., then stop cooling, zinc , Or zinc oxide, followed by addition of an aqueous potassium hydroxide solution, an aqueous potassium carbonate solution, potassium fluoride or potassium acid fluoride. At this time, the synthesis temperature
Care was taken not to exceed 150 ° C. After stirring for 2 hours, dehydration, drying and pulverization were performed to obtain flux powder.

[0025]

[Table 1]

Table 2 shows the invention examples No. 41 to No. 72 and the comparative example N.
The compounding ratio of o.41 to No.54 is shown. In any of these raw materials, the Zn-based additive and water were first placed in a polypropylene beaker, hydrofluoric acid was added while stirring and cooling, and then aluminum hydroxide was added and maintained at about 90 ° C. Subsequently, K-based additives were added, and the synthesis temperature was
Paying attention not to exceed 150 ° C, the mixture was stirred for 2 hours, dehydrated, dried and pulverized to obtain a flux powder.

[0027]

[Table 2]

Table 3 shows the compounding ratios of the invention examples No. 81 to No. 112 and the comparative examples No. 81 to No. 94. In any of these raw materials, K-based additives and water were first placed in a polypropylene beaker, hydrofluoric acid was added while stirring and cooling, and then aluminum hydroxide was added and the temperature was kept at about 90 ° C. Subsequently, a Zn-based additive was added, taking care that the synthesis temperature at this time did not exceed 150 ° C., stirred for 2 hours, dehydrated, dried and pulverized to obtain a flux powder.

[0029]

[Table 3]

Table 4 shows the compounding ratios of the invention examples No. 121 to No. 152 and the comparative examples No. 121 to No. 134. In any of these examples, the K-based additive and water were first put in a polypropylene beaker, hydrofluoric acid was added while stirring and cooling, and then the Zn-based additive was added and kept at about 90 ° C. . Subsequently, aluminum hydroxide was added thereto, taking care not to let the synthesis temperature exceed 150 ° C., stirring for 2 hours, dehydration, drying and pulverization to obtain a flux powder.

[0031]

[Table 4]

Conventional Example 1 Potassium fluoroaluminate and zinc fluoride were produced by a conventional method, and after mixing them with stirring, moisture absorbed at 120 ° C. was evaporated and pulverized to obtain a flux powder of a conventional example.

Conventional Example 2 Potassium fluoroaluminate and zinc oxide were each produced by a conventional method, and after mixing them with stirring, moisture absorbed at 120 ° C. was evaporated and pulverized to obtain a flux powder.

Conventional Example 3 A mixture of potassium tetrafluoroaluminate and aluminum fluoride and zinc fluoride were produced by a conventional method, and after mixing them with stirring, moisture absorbed at 120 ° C. was evaporated and pulverized to obtain zinc. A flux powder containing flux was obtained.

Table 5 shows the time taken to produce the flux of the present invention, comparative example and conventional example. The production of the flux according to the example of the present invention was completed in about half the time as compared with the production of the flux according to the conventional example.

[0036]

[Table 5]

Next, JIS A1050 (Al9
9.50 wt% or more) Aluminum extrusion tube and JIS
A3003 Aluminum alloy (Al-0.15wt% Cu-1.1w
JIS A4343 alloy (Al-7.5wt)
% Si) as a brazing material on both sides with a thickness of 10% and a brazing sheet having a plate thickness of 0.12 mm and corrugated, and assembled as a fin in the sample of the present invention No. 1
~ 32, Comparative Examples No. 1 to 14 and Conventional Examples 1 to 3 were each added with water to prepare a suspension having a concentration of 5%, which was spray-coated on the above sample and dried at 120 ° C for 30 minutes. Brazing was performed by heating at 600 ° C. for 5 minutes in a nitrogen gas atmosphere. And brazing property was evaluated about each sample.

The brazing property is evaluated by the bonding rate of the fin material. When the bonding rate is 90% or more, it is "○", and when it is less than 90%, it is 70%.
If the above is “△”, if less than 70% is “×”,
Table 6 shows the results.

The surface zinc diffusion was evaluated by the line analysis of the cross section of the JIS A1050 tube by EPMA and the zinc content at the depth of 10 μm from the surface. This is because the amount of zinc in the outermost layer cannot be distinguished from the zinc in the flux attached to the surface and the zinc diffused in the surface. 3 for each sample
The point was measured and the average value was calculated. The average value must be 0.5% or more in order to obtain sufficient sacrificial protection. The results are shown in Table 6.

[0040]

[Table 6]

Further, with respect to the invention examples No. 41 to 72 and the comparative examples No. 41 to 54 shown in Table 2, the same brazing property test and surface zinc diffusion amount measurement as above were carried out, and these results are shown in Table 7. Show.

[0042]

[Table 7]

Further, the brazing test and the surface zinc diffusion amount were similarly measured for the invention examples No. 81 to 112 and the comparative examples No. 81 to 94 shown in Table 3, and the results are shown in Table 8.

[0044]

[Table 8]

The brazability test and the amount of zinc diffusion on the surface of the invention samples No. 121 to 152 and the comparative samples No. 121 to 134 shown in Table 4 were also carried out, and the results are shown in Table 9.

[0046]

[Table 9]

In all of the examples of the present invention, good brazing properties and surface zinc diffusion amount were obtained, but in the comparative examples and conventional examples, good brazing properties and sufficient surface zinc diffusion amount were not obtained at the same time.

[0048]

As described above, according to the present invention, since a flux mixture containing zinc can be obtained by a single wet synthesis, it is possible to significantly shorten the steps in the production of flux, and the raw materials used are generally distributed. Since it is possible to use inexpensive industrial materials, it is possible to reduce the cost, obtain excellent brazing properties and a uniform Zn diffusion layer, and manufacture aluminum brazed products that secure long-term reliability. It has a remarkable effect.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Yanagawa 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Inventor Seiichi Tanikawa 2141 Higashi-ansu, Ikoma-gun, Nara Prefecture (72) ) Inventor, Masahiro Hattori, Sagami-ku, Kyoto-shi, Kyoto, Isomi-dori, Kawabata, Higashi-sansuji, Namba-cho 202 (72) Inventor, Keiki Kitao 16-2, Tanabe-Minamita, Tanabe-cho, Tsusuki-gun, Kyoto (72) Inventor, Masayo Kato 1-1, Showa-machi, Kariya, Aichi Prefecture, Nihon Denso Co., Ltd. (72) Inventor Taketoshi Toyama 1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd.

Claims (4)

[Claims] 1. Aluminum hydroxide (2-40 mol%) and hydrofluoric acid (20-80 mol%) are reacted at a temperature of 10-120 ° C., and 0.1 or 1 or 2 kinds of zinc and zinc oxide is added to this aqueous solution.
-40 mol% and one or two kinds of potassium hydroxide, potassium carbonate, potassium fluoride and acidic potassium fluoride in total of 5 to 50 mol% are added at a temperature of 10 to 150 ° C. for reaction. Method for synthesizing flux for aluminum brazing. 2. One or two of zinc and zinc oxide
0.1-40 mol% and hydrofluoric acid 20-80 mol% are reacted at a temperature of 10-120 ° C, and aluminum hydroxide 2 is added to this aqueous solution.
-40 mol% is added and reacted at a temperature of 10-120 ℃, and then one or more of potassium hydroxide, potassium carbonate, potassium fluoride and potassium acid fluoride, for a total of 5
A method for synthesizing a flux for aluminum brazing, characterized in that -50 mol% is added at a temperature of 10-150 ° C and reacted. 3. A total of 5 to 50 mol% of one or more of potassium hydroxide, potassium carbonate, potassium fluoride and acidic potassium fluoride and 20 to 80 mol% of hydrofluoric acid in an amount of 10 to 12
The reaction was carried out at a temperature of 0 ° C, 2-40 mol% of aluminum hydroxide was added to this aqueous solution, and the reaction was carried out at a temperature of 10-120 ° C.
A method for synthesizing a flux for aluminum brazing, characterized in that 0.1 to 40 mol% is added at a temperature of 10 to 150 ° C. and reacted. 4. A total of 5 to 50 mol% of one or more of potassium hydroxide, potassium carbonate, potassium fluoride and acidic potassium fluoride, and 10 to 12 of hydrofluoric acid 20 to 80 mol%.
The reaction is carried out at a temperature of 0 ℃, 0.1 to 40 mol% of one or two kinds of zinc and zinc oxide is added to this aqueous solution to react, and then 2 to 40 mol% of aluminum hydroxide is added to 10 to 150 ℃.
A method for synthesizing a flux for aluminum brazing, which comprises adding and reacting at the temperature of.