JPH07256481A - Composition for brazing, al material provided with composition for brazing and heat exchanger - Google Patents

Abstract

PURPOSE:To well execute brazing with excellent heat resistance with a small amt. of a flux by specifying a compsn. for brazing. CONSTITUTION:This compsn. for brazing contains the powder of zinc or zinc alloy formed with oxidized films contg. 0.05 to 0.25wt.% O in the powder. The powder of the zinc or zinc alloy has a grain size of 5 to 53mum. the binder is an acylic or methacrylic resin having a mol.wt. of 1000 to 100000. The flux of a fluoride system, such as, for example, KF-AlF3 or RbF-AlF3, is used at the time of brazing. The compounding ratio of such flux is preferably 100/3 to 100/50 in weight ratio of the powder/flux of the zinc or zinc alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique used for heat exchangers such as evaporators, condensers and radiators for automobiles.

[0002]

BACKGROUND OF THE INVENTION Conventionally, a heat exchanger made of aluminum or aluminum alloy material (hereinafter referred to as Al-based material) comprises tubes or fins made of a brazing sheet in which a brazing material is clad, and these are assembled into a predetermined shape. Manufactured by brazing.

To improve the corrosion resistance of the heat exchanger, Zn having a sacrificial anode effect is attached by thermal spraying or the like. However, since the brazing sheet is difficult to manufacture and the yield is low, the cost is high. Moreover, since brazing sheets are not suitable for recycling, waste disposal is expensive. Furthermore, in order to configure the tube with the brazing sheet, special technology such as electric sewing is required,
Further, when the fins are constructed, there is a problem that it is difficult to reduce the size and weight of the heat exchanger because the workability is poor, the jigs and tools are heavily worn, and the wall thickness cannot be reduced.

By the way, Zn, which is effective for improving the corrosion resistance,
Is melted at a lower temperature than an aluminum alloy, and molten Zn diffuses while melting and eroding the aluminum alloy. Then, the generated Zn-Al layer has a characteristic that its melting point is lower than that of the aluminum alloy. Therefore, this Zn-Al layer has a function as a brazing material, and at the same time, the Zn diffusion layer formed on the surface of the base material has a sacrificial anode effect, which is suitable for manufacturing a heat exchanger. it was thought.

From this point of view, Z containing a fluoride-based flux and a particle size of 1 to 100 μm
A heat exchanger has been proposed (JP-A-56-160869) in which a suspension containing n powder is applied on the surface of an Al material, dried and then combined, and brazed in an inert atmosphere. However, it has been pointed out that this product has a problem that the brazing property is poor when the amount of the flux is small and the joint strength between the fin and the tube is insufficient.

[0006]

DISCLOSURE OF THE INVENTION By the way, the above-mentioned proposal is characterized in that a large amount of flux is used as said flux / Zn powder is 4/6 to 9/1. However, if the amount of the flux used is large, the cost is high, and the flux residue is large, so that the appearance is deteriorated. Furthermore, it has been found that there is a problem in that the brazing furnace is deteriorated quickly due to HF generated from excess flux, contamination is caused, and the working environment is deteriorated.

Therefore, it is desired to reduce the amount of flux used. That is, a technique excellent in brazing characteristics is required even with a small amount of flux. As a result of earnestly promoting research in accordance with such a viewpoint, it has been found that the flux amount is influenced by the oxygen amount in the zinc powder. In other words, it has been found that when the zinc powder has a low degree of oxidation, the flux may be small.

[0008] However, as to whether a zinc powder that has not been oxidized at all should be used, it has been found that this is not the case. That is, it was found that brazing can be favorably performed with a small amount of flux when the oxidation is moderate. In particular, O is 0.05 to 0.
When the powder of zinc or zinc alloy having the oxide film formed at 25 wt% was used, the brazing was performed well with a small amount of flux.

The present invention has been achieved based on these results, and an object of the present invention is to provide a brazing technique in which brazing is favorably performed with a small amount of flux and which is also excellent in corrosion resistance. . An object of the present invention is to contain a zinc or zinc alloy powder having an oxide film, in which O in the powder is 0.05 to 0.25 wt%, and a binder. Achieved by

O in the powder is 0.05 to 0.25.
This is achieved by a brazing composition comprising an oxide film-formed zinc or zinc alloy powder of wt%, a binder, and a solvent. Further, it is achieved by an Al-based material characterized in that the above brazing composition is provided on the surface.

A flux may be used by combining the first heat exchanger component and the second heat exchanger component, which are made of an Al-based material on the surface of which the brazing composition is provided. It is achieved by a heat exchanger characterized by being joined by attachment. The zinc or zinc alloy powder having an oxide film with O of 0.05 to 0.25 wt% used in the present invention has an oxygen concentration of 0.02 to 0. 5%
It can be obtained by manufacturing a product having a size of about 5 to 53 μm under the conditions described above. When the oxygen concentration in the atmosphere was too lower than 0.02%, the powder tended to aggregate and become coarse.

It is preferable that the binder used in the present invention has a high tendency to volatilize at a temperature lower than the brazing temperature. Especially, molecular weight 1000
It is preferably an acrylic or methacrylic resin of up to 100,000. For example, molecular weight 1000-1
Examples include 00000 polybutyl acrylate and the like. In order to provide the brazing composition of the present invention on the surface of the Al material, a coating means is generally used. As the coating means, for example, a spray method, a flow coater method, a roll coater method,
Various means such as brush coating can be adopted. And, by such means, the thickness after drying is preferably about 5 to 50.
The brazing composition of the present invention is applied to have a thickness of μm.
More preferably, it is about 10 to 30 μm. Preferred examples of the solvent used for this coating include aliphatic alcohols having 1 to 8 carbon atoms such as methanol, ethanol, propanol, butanol, isopropyl alcohol and pentanol.

The zinc or zinc alloy powder and the binder are preferably mixed in a weight ratio of zinc or zinc alloy powder / binder of 100 / 0.1 to 100/100. More preferably 100 / 5-100 /
Twenty. Further, the mixing ratio of the binder and the solvent is such that the binder / solvent is 100/100 to 100/100 in a weight ratio.
It is preferably 00. More preferably 100/5
It is 00-100 / 2000.

When brazing, for example, KF-AlF
A fluoride-based flux such as ₃ , RbF-AlF ₃ is used. Of course, other flux may be used. The mixing ratio of such flux is 100/3 to 10 by weight ratio of zinc / zinc alloy powder / flux.
It is preferably 0/50. More preferably 100
/ 10 to 100/30. In addition, this flux is
It may be added to the brazing composition from the beginning. Alternatively, it may be added after brazing.

The Al material to which the brazing composition of the present invention is applied may be a component constituting a heat exchanger, that is, a fin or a tube, but is preferably applied to the surface of the tube. . Then, the tubes and the fins thus coated with the brazing composition on the surface are combined into a predetermined one, and then they are joined by brazing using a flux in a vacuum atmosphere or an inert atmosphere, and heat exchange is performed. It is regarded as a vessel.

In the present invention, the powder of zinc or zinc alloy is adopted because it can be worked at room temperature, not at high temperature as in the case of the molten zinc film coat, and therefore the base material is not corroded and the work is safe. . If necessary, various powdery additives (for example, flux for brazing) can be integrally supplied into the brazing material film. The adjustment range of the brazing filler metal supply amount (brazing filler metal film thickness) is wide according to the purpose. Suitable for forming a zinc film required for joining. By powdering zinc, a powder appropriately covered with an oxide film can be used. For this reason, the powder shape is maintained even when the melting point of zinc is reached during brazing, and the oxide film is removed by the flux activated at higher temperature and the melting of the base metal begins for the first time. Corrosion of the base material is less than that of the film coating, and a proper brazing material layer can be formed. For the above reason, stable brazing property can be maintained even if the brazing conditions change to some extent. Then, the brazing condition range can be applied in almost all cases which have been conventionally industrially implemented. This is because the features described above are exhibited.

When the heat exchanger is manufactured, it is not necessary to use a brazing sheet, the cost of the heat exchanger is low, the corrosion resistance is improved, and the clad fin is not required. It is possible to reduce the thickness, reduce the weight, reduce the material cost, and reduce the wear of the jig. Hereinafter, specific examples will be described.

[0018]

[Example] The following table was formed on the surface of an extruded flat multi-hole tube made of A1.
The brazing composition shown in No. 1 was applied. Table-1 Zn-based powder binder solvent flux composition (wt%) size amount ZnAlO (μm) weight part weight part weight part weight part Example 1 99.75 0 0.25 53 100 5 5 40 15 Example 2 99.80 0 0.20 53 100 5 40 10 Example 3 99.75 0 0.25 10 100 20 20 100 30 Example 4 99.80 0 0.20 10 100 20 20 100 20 Example 5 99.85 0 0.15 20 100 100 10 50 10 Example 6 99.90 0 0.10 20 100 10 10 50 10 Example 7 94.75 5 0.25 30 30 100 30 30 100 30 Example 8 94.80 5 0.20 30 100 20 20 100 30 Example 9 94.85 5 0.15 30 100 10 50 20 Example 10 94.90 5 0.10 30 100 10 10 50 15 Comparative Example 1 99.67 0 0.33 20 100 20 100 30 Comparative Example 2 94.67 5 0.33 30 100 20 20 100 30 Comparative Example 3 100 0 0.00 80 100 100 10 50 30 Comparative 4 95 5 0.00 100 100 10 50 30 * binder polybutyl acrylate * solvent having an average molecular weight of 10000 O is 0.00 wt% in isopropyl alcohol * Zn-based powder are those O is not detected.

The brazing composition is about 30 μm.
Combining a corrugated fin made of Al with an extruded flat multi-hole tube provided with a thickness of 600 in a nitrogen atmosphere.
Brazing was performed by holding at 5 ° C for 5 minutes. With respect to the heat exchanger thus obtained, the fin brazing rate and the corrosion resistance were examined, and the results are shown in Table-2.

Table 2 Brazing Bonding Ratio Corrosion Resistance (SWAAT Test) Example 1 98% ○ (20 days pass) Example 2 97% ○ (20 days pass) Example 3 97% ○ (20 days pass) Implementation Example 4 98% ○ (20 days pass) Example 5 98% ○ (20 days pass) Example 6 98% ○ (20 days pass) Example 7 96% ○ (20 days pass) Example 8 97% ○ ( Passed for 20 days) Example 9 98% ○ (Passed for 20 days) Example 10 99% ○ (Passed for 20 days) Comparative Example 1 40% × Comparative Example 2 35% × Comparative Example 3 28% × Comparative Example 4 25% ×

[0021]

[Effect] Brazing is performed well with a small amount of flux,
Moreover, a product having excellent corrosion resistance can be obtained.

Claims (6)

[Claims] 1. O in the powder is 0.05 to 0.25 w.
A brazing composition comprising a zinc or zinc alloy powder having an oxide film of t% and a binder. 2. O in the powder is 0.05 to 0.25 w.
A brazing composition comprising zinc or zinc alloy powder having an oxide film of t%, a binder, and a solvent. 3. The zinc or zinc alloy powder has a particle size of 5
The brazing composition according to claim 1 or 2, wherein the brazing composition has a thickness of ˜53 μm. 4. The binder has a molecular weight of 1,000 to 10,000.
3. The brazing composition according to claim 1 or 2, which is an acrylic or methacrylic resin of No. 0. 5. An Al-based material, characterized in that the brazing composition according to any one of claims 1 to 4 is provided on the surface. 6. A first heat exchanger component, which is made of an Al-based material and whose surface is coated with the brazing composition according to any one of claims 1 to 4, and a second heat exchanger component. A heat exchanger in which the above are combined and joined by brazing using a flux.