JPH067928A - Method for brazing mg-containing aluminum material - Google Patents

Abstract

PURPOSE:To eliminate the residual flux deposit and to improve the brazing property and the surface treatability by regulating moisture concn., oxygen concn. and flux concn. in the atmosphere in a brazing furnace to specific values, respectively. CONSTITUTION:Inner part of the brazing furnace is adjusted to the atmosphere containing the flux gas and the joining part of an aluminum containing 0.5-2.5wt.% Mg is heated at a prescribed temp. in this atmosphere and a brazing filler metal for joining is melted to execute the brazing. Then the moisture concn., the oxygen concn. and the flux gas concn. are regulated in the atmosphere to <=120ppm, <=120ppm and <=200ppm respectively. Thus, the flux quantity can be restrained to the necessary min. limit. Therefore, even in the case of using the fluoride-series flux as the flux, by reducing the consumption of the flux, the reacting product between Mg and element contained in the flux and the residual flux deposit on the aluminum material surface after brazing can be eliminated, and the aluminum brazed product having excellent appearance quality and high commertial value is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a brazing method for an aluminum material containing 0.5 to 2.5 wt% of Mg, for example,
The present invention relates to a brazing method for an aluminum material which is preferably used for manufacturing an aluminum heat exchanger.

In this specification, the term "aluminum" is used to include its alloy.

[0003]

2. Description of the Related Art Since Mg-containing aluminum materials have high strength, they are widely used as materials for various aluminum products that require strength.

However, since the Mg-containing aluminum material is inferior in brazing property, particularly flux brazing property, its application as a material for brazing products such as automobile radiators, car cooler evaporators and capacitors is limited. was there.

That is, in the past, in general, flux brazing was carried out by applying a flux suspension to an aluminum material to be joined, drying it, and then heating it to a predetermined temperature. Therefore, when a non-corrosive fluorinated flux is used as the flux, the flux reacts with Mg in the aluminum material to cause MgF ₂ or KMgF
A cotton-like reaction product such as ₃ is formed. Since this reduces the flux effect, sufficient brazing cannot be performed, and this has been a cause of hindering the expansion of application of Mg-containing aluminum materials to brazing products. Also,
There is also a problem that the reaction product and the residual flux adhere to the surface of the product, resulting in deterioration of appearance quality and surface processability.

Therefore, in recent years, a method of brazing an Mg-containing aluminum material in an atmosphere in which a chloride-based or fluoride-based flux is gasified has been proposed. The flux gas is 0.05 mmHg or more and less than 3.5 mmHg. A method of brazing in an existing non-oxidizing atmosphere has been proposed. (JP-A-3-114667).

[0007]

However, even when the Mg-containing aluminum material is brazed in the flux gas-containing atmosphere as described above, since the flux concentration is high, the Mg-containing aluminum material is also contained in the flux. For example, it reacts with F to form a cotton-like reaction product of MgF ₂ or KMgF ₃ to reduce the flux effect, and these reaction products and residual flux adhere to the product surface, resulting in appearance quality and surface treatment. However, there is still a problem that it deteriorates the property.

The present invention has been made in view of such circumstances, and in brazing an aluminum material containing Mg even when a fluoride flux is used,
It is an object of the present invention to provide a brazing method for an Mg-containing aluminum material which is excellent in brazing property, and is excellent in appearance quality and surface treatment property by eliminating the formation of a reaction product with a flux.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the inventors have conducted various experiments and researches, and as a result, the reaction between Mg and the flux on the surface of the brazed product which occurs in the atmosphere containing the flux gas described above. It was found that the product adhesion and the flux residue were caused by the high water and oxygen concentrations in the brazing atmosphere. That is, when the moisture and oxygen concentrations in the atmosphere are high, the concentration of flux gas must be increased in order to obtain good brazing properties, and as a result, the amount of adhered flux on the surface of the brazed product increases and It was found that the reaction between the Mg contained in the material and the element (for example, F) contained in the flux is promoted and the surplus flux remains on the surface of the brazed product.

The present invention has been made on the basis of such knowledge, and the flux gas concentration is lowered by controlling the moisture concentration and the oxygen concentration in the atmosphere to be low, and
This enables good brazing of the g-containing aluminum material. More specifically, the inside of the brazing furnace is adjusted to an atmosphere containing a flux gas, and the atmosphere is 0.5 to 2.5 w.
In a brazing method of an Mg-containing aluminum material, which comprises heating an aluminum joining member containing t% of Mg to a predetermined temperature and melting a brazing material for joining to perform brazing, the water concentration in the atmosphere is 120 ppm or less, Oxygen concentration is 120p
The gist is a brazing method for an aluminum material, wherein the flux gas concentration is regulated to pm or less and 200 ppm or less, respectively.

The aluminum material which is the object of the brazing method according to the present invention contains 0.5 to 2.5 wt% of Mg, and more specifically 0.5 to 2.5 wt% of Al containing Mg.
-Mg alloy, Al-Mg containing 0.5 to 2.5 wt% Mg
-Zn alloy, 0.5-2.5 wt% Mg-containing Al-Si
-Mg alloy, 0.5-2.5 wt% Mg-containing Al-Si
-Zn-Mg alloy and the like. The Mg content is 0.5
Brazing is possible by the conventional brazing method for Al alloys less than wt%, and according to the present invention for Al alloys over 2.5 wt% because the reaction between Mg and flux is promoted. Attaching is difficult.

Generally, the brazing atmosphere is an inert gas atmosphere such as N ₂ gas. In this atmosphere, the water concentration exceeds 120 ppm, or the oxygen concentration is 120 ppm.
When it exceeds, the growth of the oxide film on the surface of the aluminum material is promoted and the oxide film is regenerated despite the oxide film removing action of the flux gas. Therefore, in order to sufficiently remove the oxide film, the flux gas concentration must be increased rapidly, which causes the white flux to remain on the surface of the aluminum brazed product after brazing, and also to the aluminum material. The reaction product between the contained Mg and the flux-containing element (for example, F) leads to a reduction in the flux effect, a reduction in the appearance quality, and a reduction in the surface processability in the subsequent steps. Therefore, in the present invention, the water concentration in the brazing atmosphere is 120 ppm or less,
The oxygen concentration must be specified below 120 ppm. The smaller the water concentration and oxygen concentration, the smaller the amount of flux gas, and the risk of residue of flux adhesion on the surface of the brazed product and the risk of formation of reaction products between Mg-flux-containing elements are also reduced. It is particularly preferable that the moisture concentration in the atmosphere is 20 ppm or less and the oxygen concentration is 40 ppm or less. Since the moisture concentration increases due to the release of adsorbed moisture of the product, it is necessary to sufficiently remove the moisture in the preheating zone before the brazing zone. Further, it is desirable that the N ₂ gas as the atmosphere gas does not contain water and oxygen.

Under the water concentration and oxygen concentration regulations as described above, the flux gas concentration in the atmosphere is 20.
Must be specified below 0 ppm. When the flux gas concentration exceeds 200 ppm, the amount of the flux is too large to promote the formation of cotton-like reaction products between the Mg-flux-containing elements, and a white color due to a large amount of flux remaining on the surface of the brazed product. There is a risk that it will change.
Therefore, by defining the flux gas concentration within the range of 200 ppm or less, a reaction product between the Mg-flux-containing element is not formed, a sufficient flux effect is brought about, and good brazing joining can be realized. The residual flux of aluminum material after brazing is 0.2g
/ M ² or less, preferably 0.05 g / m ² or less. A particularly preferable flux gas concentration is 65
It is below ppm. Since brazing itself becomes difficult if the flux gas concentration is too low, it is preferable to secure the flux gas concentration of 1 ppm or more.

Here, the flux gas means a gas in which the flux is vaporized. The type of the flux is not particularly limited, but a non-corrosive fluoride-based flux such as KAlF ₄ or other aluminum fluoride (AlF ₃ ) component and potassium fluoride (KF) component is used as a eutectic composition or A complex mixture or the like which is substantially complexed by being included in a composition range close to it can be mentioned. Most preferably, KAlF is used in terms of good flux action and easy gasification.
_It is better to use ₄ .

When KAlF ₄ is used as the flux, it is preferable to set the concentration ratio of the moisture and the flux gas in the atmosphere to be more than the flux gas concentration of 1 with respect to the moisture concentration of 1. This is due to moisture in the atmosphere and KAlF
4 and KAl react with each other in the same amount as shown in the following chemical formula.
This is because F ₄ may disappear, so that the amount of KAlF ₄ is set to be larger than the amount of water and KAlF ₄ is left in the atmosphere even when the reaction is completed. Particularly preferably, the concentration ratio of water to flux gas is 1:
It is better to set it to 1.1 or higher.

3KAlF ₄ + 3H ₂ O → 6HF + K ₃ AlF ₆ + Al ₂ O ₃ By the way, when HF is contained in the atmosphere, HF reacts with Al of the aluminum material to form a dense film such as AlF _3. In order to inhibit the wettability of the solder, it is preferable to regulate the HF concentration in the brazing atmosphere to 60 ppm or less.

The means for adjusting the brazing atmosphere or the like to the atmosphere containing the flux gas is not particularly limited, and the flux may be gasified outside the furnace and supplied into the furnace, or the flux may be contained. The container may be placed in the furnace and vaporized and gasified in the furnace. However, in terms of easiness of adjusting the flux gas concentration, it is most preferable to gasify the gas outside the furnace and supply this gas into the furnace.

As described above, after adjusting the atmosphere in the furnace to the water concentration, the oxygen concentration and the flux gas concentration in the predetermined ranges, the aluminum material having a lower melting point than that of the aluminum joining member is used in this atmosphere, Similarly 590
The brazing filler metal is melted by heating at about 610 ° C. for about 1 to 15 minutes, and brazing of the Mg-containing aluminum material is achieved.

[0019]

In the present invention, since the flux gas concentration can be set low by controlling the water concentration and the oxygen concentration in the atmosphere to be low, Mg contained in the aluminum joining member and elements contained in the flux gas can be set. It does not form a cotton-like reaction product with and does not cause residual flux adhesion on the product surface after brazing.

[0020]

【Example】

(Example 1) A6063 (Mg content 0.79 wt%)
A reverse T-joint test piece was prepared by using a base material made of an alloy and having a thickness of 2 mm, and a double-sided brazing sheet material having a clad ratio of 10% and a core material of A3003 alloy and Al-8 wt% Si alloy, and a thickness of 1 mm. Assembled Then, the assembly is subjected to a water concentration of 40 ppm, an oxygen concentration of 30 ppm, and a KA.
Brazing was performed by heating at 605 ° C. for 5 minutes in an N ₂ atmosphere adjusted to an IF ₄ flux gas concentration of 50 ppm.

(Example 2) As a base material in the assembly of Example 1, an A5052 alloy (Mg content 2.47 wt.
%) Was used for brazing under the same conditions as in Example 1.

Example 3 Using the alloy of A6063 alloy with 2 wt% Zn added as a base material in the assembly of Example 1, brazing was performed under the same conditions as in Example 1.

Example 4 A substrate made of an A3003 alloy (Mg content of 0.01 wt% or less) having a thickness of 3 mm, and A
Using 3003 alloy as the core material, 4004 alloy (Al-9.3w
An inverted T-joint test piece was assembled using a double-sided brazing sheet having a clad ratio of 9% and a thickness of 1 mm, which was made of t% Si-1.9wt% Mg) as a skin material. Then, the assembly is subjected to a water concentration of 10 ppm, an oxygen concentration of 4 ppm, and KAlF ₄
Brazing was performed by heating at 605 ° C. for 5 minutes in an N ₂ atmosphere adjusted to a flux gas concentration of 20 ppm.

(Example 5) As a skin material for the brazing sheet in the assembly of Example 4, 1w was added to 4004 alloy.
Brazing was performed under the same conditions as in Example 4 using an alloy to which t% Zn was added.

(Example 6) An assembly similar to that in Example 4 was used, in which the water concentration was 100 ppm and the oxygen concentration was 90 pp.
Brazing was performed by heating at 605 ° C. for 5 minutes in an N ₂ atmosphere adjusted to have a KAlF ₄ flux gas concentration of 145 ppm.

(Comparative Example 1) The same assembly as in Example 1 was used, with a water concentration of 150 ppm and an oxygen concentration of 200 p.
Brazing was performed by heating at 605 ° C. for 5 minutes in an N ₂ atmosphere adjusted to 290 ppm of KAlF ₄ flux gas concentration of pm.

(Comparative Example 2) An assembly similar to that in Example 4 was used, with a water concentration of 120 ppm and an oxygen concentration of 100 p.
Brazing was performed by heating at 605 ° C. for 5 minutes in an N 2 atmosphere adjusted to a PF, KAlF ₄ flux gas concentration of 360 ppm.

With respect to the brazed product obtained as described above, the brazing property and the appearance state were visually observed, and the surface treatment property was evaluated. As for surface treatment, each brazing product was treated with phosphoric acid chromate and spray-coated with an acrylic resin, and then a 1 mm square square was marked on the coating surface and a tape peeling test was carried out. Was evaluated (cross-cut test).
The evaluation results are shown in Table 1.

[0029]

[Table 1] From the results of Table 1, according to the present invention, even with an aluminum material containing Mg, good brazing can be performed without lowering the flux effect, and Mg-flux on the surface of the aluminum material after brazing It was confirmed that the formation of the reaction product between the contained elements and the residual adhesion of the flux can be eliminated, and the coating film has good adhesion and surface treatment property can be improved.

[0030]

According to the present invention, the inside of the brazing furnace is adjusted to the atmosphere containing the flux gas, and the aluminum joining member containing 0.5 to 2.5 wt% of Mg is specified in the atmosphere. In a brazing method for an aluminum material, which is performed by heating to a temperature and melting the brazing material for joining, the moisture concentration in the atmosphere is 120 ppm or less, the oxygen concentration is 120 ppm or less, and the flux gas concentration is 200 pp.
Since it is characterized in that each is specified to m or less, the amount of flux can be suppressed to a necessary minimum. Therefore, even if the flux is a fluoride-based flux, it is possible to eliminate the formation of reaction products between the Mg-flux-containing elements and the flux residue on the surface of the aluminum material after brazing due to the reduction in the amount of flux used. It is possible to provide aluminum brazed products with excellent appearance quality and high commercial value. Therefore, the application of the Mg-containing aluminum material having excellent strength to a brazed product can be expanded. Not only that, even when a surface treatment such as corrosion resistance treatment and coating is performed after brazing, the film and the coating film can have excellent adhesion without peeling.

Moreover, since the concentration of the flux gas is low, the brazing furnace is less damaged and the frequency of maintenance is low, which is extremely economically advantageous.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoichi Sato 6-224 Kaiyamacho, Sakai City, Osaka Prefecture Showa Aluminum Co., Ltd.

Claims (1)

[Claims] 1. The brazing furnace is adjusted to an atmosphere containing a flux gas, and 0.5 to 2.5 wt% of Mg is contained in the atmosphere.
The aluminum joining member containing is heated to a predetermined temperature,
In a brazing method for an Mg-containing aluminum material, which comprises brazing a brazing filler metal by brazing, a moisture concentration in the atmosphere is 120 ppm or less, an oxygen concentration is 120 ppm or less, and a flux gas concentration is 200 ppm.
A method for brazing an Mg-containing aluminum material, wherein the brazing method is regulated to ppm or less.