JPH05269589A - Al brazing sheet for drawncup type heat exchanger - Google Patents

Abstract

PURPOSE:To obtain an Al brazing sheet for a drawncup type heat exchanger capable of forming a fillet enough for both joining parts of outer and inner surface sides and stably obtaining pressureproof strength above the prescribed value. CONSTITUTION:The brazing sheet has on both sides of core material the brazing filler metal having a composition consisting of, by weight, 7-12% Si, 0.7-1.7% Mg, as required 0.03-0.15% Bi, and the balance Al with inevitable impurities, but the brazing filler metal is of the composition that Si content of the one side surface is >=0.8% larger than that of the other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum brazing sheet used for a drone cup type heat exchanger incorporated in a car air conditioner, an oil cooler or the like.

[0002]

2. Description of the Related Art As shown in FIG. 1, a Delon cup type heat exchanger is constructed by laminating tubular bodies (1) each having a brazing sheet formed into a cup shape, and fins () between the tubular bodies. 2) is arranged and the inside is semi-sealed. Therefore, as shown in FIG. 2, the brazed joint is composed of the joint (3) located on the outer surface and the joint located on the inner surface.
There is (4), and it is necessary to obtain a sufficient brazing joint at both joints.

As a brazing method, a vacuum brazing method is mainly used. Conventionally, a brazing sheet generally used as a brazing sheet for vacuum brazing of a drone cup heat exchanger is a brazing material: Al. The material consists of -10% Si-0.5 to 1.7% Mg (4004), Al-10% Si-0.5 to 1.7% Mg-0.1% Bi (4104), and a core material: 3003.

However, in the Delon cup type heat exchanger made of this material, the brazing property on the outer surface side is almost satisfactory, but the brazing property on the inner surface side is not sufficient to form the fillet, and the predetermined pressure resistance strength is not sufficient. May not be obtained, which is one of the causes of lowering the yield.

Therefore, as a method for improving this, many studies have been made on the brazing material composition. For example, increase in Si content, decrease in Mg content, addition of Sn, Sb, Ba, Be, etc.
(Eg, JP-A-59-85375). However, the present situation is that no satisfactory improvement method has been found yet.

The present invention has been made in view of the problem of the brazing property on the inner surface side of the conventional drone cup type heat exchanger, and it is possible to form a fillet which is satisfactory for both the outer surface side and the inner surface side joints. It is an object of the present invention to provide a brazing sheet that can be obtained and stably obtain a pressure resistance of a predetermined value or more.

[0007]

In order to solve the above-mentioned problems, the present inventor has investigated the cause of the poor brazing property on the inner surface side in the conventional brazing sheet for aluminum drone cup type heat exchangers, and has taken measures against it. As a result of earnest studies, it was found that it is possible to use a brazing material having a composition in which the difference in Si content between the inner and outer surfaces of the core material is 0.8% or more. The present invention has been made here.

That is, according to the present invention, Si: 7 to 12% and Mg: 0.7 to 10% on both surfaces of a core material made of an aluminum alloy.
1.7%, Bi: 0.03 to 0.15 as required
%, With the balance being Al and the brazing material which is an unavoidable impurity, in an aluminum brazing sheet, wherein the brazing material has a Si content in the brazing material on one side and a Si content in the brazing material on the other side. It is a gist of a brazing sheet for a drone cup heat exchanger, which has a composition of 0.8% or more relative to the amount.

The present invention will be described in more detail below.

[0010]

[Action]

Generally, in the vacuum brazing method, Mg in the brazing material evaporates during vacuum heating and reacts with H ₂ O and O ₂ in the atmosphere to cause O ₂ content in the atmosphere, as is called a getter action. To suppress the oxidation of the surface of the material and promote the destruction of the oxide film on the surface, resulting in wetting of the wax, but in the Delon cup heat exchanger the semi-closed structure on the inner side compared to the outer side Therefore, the degree of vacuum becomes inferior to that on the outer surface side, the evaporation amount of Mg is also reduced, and the getter action is weakened. On the other hand, since it is difficult for O _{2 and the} like in the atmosphere to penetrate into the inner surface side, oxidation due to the atmosphere is slower than in the outer surface side, and brazing is possible.

In addition, the flow of the brazing filler metal is connected between the outer surface side and the inner surface side, and tends to move to the side having good wettability, so that the wettability is balanced between both sides. This is important for obtaining good brazing of both the outer surface side and the inner surface side joints.

In the present invention, the balance of the wettability between the outer surface side and the inner surface side is made to be dominant on the inner surface side, so that the brazing of both joints is good and the inner surface side is predominant. Therefore, it has been found that it is necessary to make the composition in which the amount of Si in the brazing material is 0.8% or more larger on the inner surface side than on the outer surface side.

Next, the reasons for limiting the chemical components in the present invention will be explained.

Brazing material

Si: Si is used as an essential component of a brazing material for Al because it lowers the melting point and has good fluidity. Generally, a brazing material having a composition containing 7 to 12% of Si is used. It is used a lot. Also in the present invention, the range of the Si amount may be the same range, and the Si amount is 7 to 12%.

Mg: Mg is an essential element that imparts a getter action in vacuum brazing, and M for the outer surface side.
The higher the g content, and the lower the Mg content on the inner surface,
Good brazing and joining are achieved. Therefore, Mg
The lower limit of the content is 0.7% which is the lower limit that satisfies the brazing property on the outer surface side. As a result, the brazing property is naturally satisfied even on the inner surface side. However, when the content exceeds 1.7%, the effect is saturated, the workability is deteriorated, and
Corrosion of the brazing material to the core material during brazing increases. Therefore, the Mg content is set to 0.7 to 1.7%.

Bi: Furthermore, the brazing filler metal contains S, which is the above-mentioned essential component.
In addition to i and Mg, 0.03 to 0.15% B as required
The inclusion of i is allowed. Bi is contained as necessary because it is effective in preventing brazing deterioration when the degree of vacuum in the furnace deteriorates. Bi is a component having a low melting point, which locally melts prior to the melting of the brazing filler metal when the brazing material is heated, and has the effect of promoting the evaporation of Mg to obtain a getter action. Also has the effect of preventing brazing deterioration. The same effect was obtained at 0.03% or higher, but 0.15%
%, The effect is saturated and the castability and rollability are rather deteriorated. Therefore, the Bi content is 0.03 to 0.0.
It was set to 15%. As the case where the degree of vacuum in the furnace deteriorates, if moisture is brought into the furnace when the outside air environment is humid,
There is a case where a large amount is adsorbed to the furnace wall.
The inclusion of is not essential, but is not essential.

However, in the present invention, the relationship of the Si content in each brazing material coated on both sides of the core material is regulated as follows.

That is, as a brazing material for coating both sides of the core material, the Si content in the brazing material on one side is 0.8% or more higher than the Si content in the brazing material on the other side. Specifically, for example, the amount of Si in the brazing material on one side, which is the inner surface side of the drone cup heat exchanger, is 0.8% within the above range from the amount of Si in the brazing material on the other surface, which is the outer surface side. The above is a large number of combinations.

The brazing property on the inner surface side is considered to be due to an increase in the evaporation amount of Mg as the brazing temperature rises, but it improves. However, there is a problem in practical use because an increase in the brazing temperature of the brazing material on the core material and a rapid increase in deformation buckling of the brazing sheet and the fin material due to the rise in the brazing temperature. In the present invention, the effect of increasing the brazing temperature is achieved by lowering the melting point of the brazing material, and the melting point of the brazing material on the inner surface side is further increased as compared with the brazing material on the outer surface side to increase the Si content. Then, the balance of the brazing property can be shifted to the inner surface side predominantly, and excellent brazing property can be obtained on both the outer surface side and the inner surface side.

The difference in the amount of Si between the brazing materials on both sides is 0.
If it is less than 8%, the effect of being dominant on the inner surface side is small, so the difference is 0.8% or more. In that case, the upper limit is 7 to 12
%, The effect is obtained, but the difference is 2 from the viewpoint of suppressing erosion of the high Si brazing material on the inner surface side as much as possible.
It is preferably within%.

Core material

In the brazing sheet according to the present invention, as the core material, in addition to the generally used 3003 material, an aluminum alloy of any component system and composition may be used as long as it is an aluminum alloy which does not cause burning during brazing. You can

Next, examples of the present invention will be described.

[0026]

【Example】

[Table 1] Brazing filler metal with composition shown in

[Table 2] With the core material (A3003) having the composition shown in FIG. 2, as shown in FIG. 2, a brazing material (5) -core material (6) -brazing material (5 '),
Brazing sheet O material with a clad ratio of 30% (0.6 mm
(Thickness) is manufactured, and this material is processed into a test piece simulating the Delon cup type heat exchanger shown in FIG.
It was carried out by heating at 600 ° C. for 2 minutes under a vacuum of 10 ⁻⁵ Torr. Fig. 5 shows the brazing situation.

The shape of the fillet was examined for the combination of the brazing materials and the outer surface fillet (7) and the inner surface fillet (8) at this time, and the brazing property was evaluated according to the following criteria.
The result

[Table 3] Shown in. ○: Large and uniform fillet formation □… Medium and uniform fillet formation ◇… Partial and non-uniform fillet formation △… Small and non-uniform fillet formation ×… Partial or almost no fillet formation

As is clear from Table 3, the materials of the present invention have excellent brazing properties on both the outer surface side and the inner surface side, whereas the comparative material has a difference in the amount of Si in the brazing material on both surface sides. The brazing property on the inner surface side is not sufficient because it is small.

[0029]

As described in detail above, according to the present invention,
It is possible to provide a brazing sheet in which a satisfactory fillet formation can be obtained in both the outer surface side and the inner surface side joint portions of the Delon cup heat exchanger, and a compressive strength not lower than a predetermined value can be stably obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a Delon cup type heat exchanger.

FIG. 2 is an enlarged view of a portion A in FIG.

FIG. 3 is a cross-sectional view showing a configuration of an aluminum brazing sheet in an example.

FIG. 4 is a view showing a test piece imitating a Delon cup type heat exchanger, showing the whole.

5 is an enlarged view of part B in FIG.

[Explanation of sign]

 DESCRIPTION OF SYMBOLS 1 Tubular body 2 Fins 3 External brazing part 4 Internal brazing part 5 One-side brazing material 5'Other-side brazing material 6 Core material 7 Outer surface fillet 8 Inner surface fillet

Claims (1)

[Claims] 1. On both sides of a core material made of an aluminum alloy, in weight% (hereinafter the same), Si: 7 to 12% and Mg:
It contains 0.7 to 1.7%, and if necessary Bi: 0.03 to
An aluminum brazing sheet coated with a brazing filler metal containing 0.15% and the balance being Al and inevitable impurities, wherein the brazing filler metal has a Si content in the brazing filler metal on one surface side of the brazing filler metal on the other surface side. A brazing sheet for a drone cup type heat exchanger, which has a composition that is 0.8% or more higher than the Si content of.