JPH02307695A - Vapor phase brazing method for al or al alloy - Google Patents

Abstract

PURPOSE:To improve quality, such as good surface treatability, of Al or Al alloy members to be brazed via brazing material and excellent corrosion resistance, by brazing the above-mentioned members in a nonoxidative atmosphere where the vapor of KSnF3 exists. CONSTITUTION:Al tube material 1 formed to a tubular shape by a hot extrusion molding is bent to a zigzag shape by the conventional method and corrugated fins 2 are inserted therebetween, then connectors 3 are mounted thereto to assemble a condenser. The fins 2 consist respectively of the brazing sheets formed by using an Al alloy consisting of specific components as a core material and cladding the same with a facing material. The connectors 3 consist of the Al alloy as well. The joint parts between the tube material 1 and the connectors 3 are previously joined by TIG welding. After this assembly is degreased, the assembly is imposed on a stainless steel tray and further, KSnF3 is placed thereon. The assembly is inserted into a furnace the atmosphere in which is substd. with a gaseous nitrogen atmosphere and which is maintained at a high temp. The brazing is thus executed. The desired quality is obtd. in this way and the production stage is shortened.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for brazing 80 or 10 alloy, and improves the performance of brazed members in the manufacture of heat exchangers for automobiles, for example, and improves the manufacturing efficiency. This reduces costs.

[Conventional technology]

Normally, in brazing AlQ or AlQ alloy, the AlQ or 10 alloy members to be joined are fixed via a brazing filler metal whose melting point is lower than that of AlQ, etc., to form an assembly. This is done by heating to a temperature lower than the melting point of the Al or 10 alloy members to be joined. The brazing filler metal is generally Al-3i.
Brazing material is used in the form of a plate, wire, or powder, or a laminated material (hereinafter referred to as a plating sheet) in which a core material made of AlQ or AlQ alloy is coated with the brazing material. used in form.

Conventional brazing methods generally include flux brazing, which uses flux to remove the acid film on the surface of the parts to be brazed, and vacuum brazing, which does not use flux.

The above-mentioned flux brazing properties include furnace brazing properties, in which the assembly to be joined is immersed in molten chloride-based flux and heated for brazing. However, since this chloride-based flux is corrosive to AlQ, it must be completely removed by cleaning after brazing, making the manufacturing process very complicated.

On the other hand, vacuum brazing, in which the assembly to be joined is placed in a vacuum and heated while brazing, eliminates the need for cleaning as a post-process, and also provides good surfaces after brazing. Although it has advantages, there are problems such as the need for high vacuum and material limitations.

Furthermore, recently, a method of brazing in a furnace using a fluoride flux has become widely used as a method of brazing to solve the above-mentioned problems.

As described in Japanese Patent Publication No. 58-27037, this method uses a mixture of K AlQF, which is non-hygroscopic and non-corrosive to A and 0, and K 3A OF a as a flux, and this is added to water. It is suspended and applied to the surfaces of the assemblies to be joined for brazing. One of its features is that it uses non-corrosive flux, so no post-treatment to remove the flux is required.

[Problem to be solved by the invention]

However, the method described in Japanese Patent Publication No. 58-27037 necessarily requires a coating and drying process to make the flux adhere to the surface of the assembly, and the applied flux is used to transfer the assembly to the next process. Many items fall off from the assembly during transport, resulting in a low yield of effectively used flux. Furthermore, since flux residue remains unevenly on the surface of the joined parts after brazing, the surface becomes dirty compared to conventional vacuum brazing, and the commercial value is inferior. In addition, chromate treatment is performed in the next process to improve corrosion resistance. However, there were drawbacks such as the black coating process becoming uneven and its effects not being fully demonstrated.

Furthermore, since this flux residue is non-conductive, for example, when adopting a corrosion prevention method that protects the pipe body with sacrificial fins in a heat exchanger, the flow of anticorrosion current is obstructed and the corrosion prevention effect cannot be obtained sufficiently. There is.

[Means to solve the problem]

In view of this, as a result of various studies, the present invention has developed the vapor phase brazing properties of A12 or Al alloy, which does not require the process of directly applying flux to the assemblies to be joined.
A method of brazing AlQ or AlQ alloy through a brazing material, which is characterized in that the parts to be brazed are brazed in a non-oxidizing atmosphere in which K S n F:+ vapor is present. .

[Effect]

In this way, by placing the assembly as the members to be joined in a non-oxidizing atmosphere where K S n It adheres and destroys the 80% oxide film on its surface, promoting wetting of the wax, resulting in the wax flowing uniformly and forming a uniform fissure at the joints of the assembly. .

And to generate such steam, K S n F
3 and the parts to be brazed may be placed in the furnace together, or K S n F 3 may be placed in advance in the furnace where the brazing will be performed, and when the temperature of the furnace is raised, the heat will simultaneously It may be evaporated, or it is also possible to generate this vapor outside the furnace and supply nitrogen gas or the like as a carrier into the furnace.

Note that when K S n F 3 is generated in a furnace, not all of the molten K S n F 3 evaporates, but only a part of it evaporates. Therefore, in the case of repeated brazing, there is no need to newly supply KSnF3, and it is sufficient to supply it when the amount of steam generation decreases. Also K S
nF's may be supplied in the form of KF and SnF2, for example.

Furthermore, the presence of K S n F 3 vapor in a non-oxidizing atmosphere allows the assembly to be completely covered with vapor, so that less vapor density is required and flux consumption is reduced.

Examples of non-oxidizing atmospheres include nitrogen, argon, -
It can be used in any atmosphere including carbon oxide.

Further, in order to carry out the present invention, it is preferable to use a furnace with a high degree of airtightness, but even if a furnace with a degree of airtightness is inferior, the assemblies to be joined are placed in a container made of stainless steel or the like together with the steam generated and brazed. It can be easily brazed by heating.

In this way, by using KSnF vapor, it is possible to braze the assembly without applying flux directly to the assembly. For example, it is generally difficult to braze the inside of a heat exchanger that has joints inside the assembly, such as the Dron cup type evaporator shown in Figure 1 or the parallel flow type condenser shown in Figure 2. be. Therefore, in such cases, apply a fluoride flux such as K S n F 3 or potassium fluoroaluminate complex to the joints inside the assembly and dry it, and then apply these fluxes to the joints outside the assembly. KSn without coating
A method of brazing in a non-oxidizing atmosphere in the presence of F3 vapor is effective. In addition, in this way, partial application of fluoride flux such as K S n F 3 or potassium fluoroaluminate complex is not limited to the inside of the assembly, but also to the outside.
For example, if the shape of the joint is complex and it is difficult to braze only with KSnFs vapor, use KSnF partially.
A fluoride flux such as S or potassium fluoroaluminate complex may be directly applied.

〔Example〕

Next, examples of the present invention will be described.

As shown in Fig. 3, a tube material (1) made of JIS A1050 (99.5% or more Al), which has been hot-extruded into a tube shape by a conventional method, is bent into a serpentine shape, and a tube is inserted between the serpentine tube materials (1). 〇A corrugated fin (2) consisting of a plating sheet with a thickness of 0.16 mm made of a core material of ○-1%Mn-1%Zn alloy and cladding with A (2-10%5t-IXZn alloy skin material) on both sides. Sandwich and further A(1)-4%Zn-
A serpentine type capacitor was assembled by attaching a connector (3) made of 1% Mg alloy. Please note that the joint between this pipe material (1) and connector (3) is JI
They were joined by TIG welding using a welding rod of SA1070 (A1299.7% or more).

Next, this assembly was degreased with an organic solvent and placed on a stainless steel tray, and 500 g of KSnFa per 11 internal volumes of the brazing furnace was placed on the tray. Then, the dew point -409C5 oxygen = 7- was replaced with a nitrogen gas atmosphere with a concentration of 1100pp, and 610
This assembly was inserted into the furnace maintained at 610°C for 5 minutes to perform brazing. At this time, K S n F 3 melts and evaporates while being heated to the brazing temperature after being inserted into the furnace, and since it covers the assembly as an atmosphere during brazing, it acts effectively as a flux. Become.

The condenser after the brazing was taken out of the furnace and the appearance of the surface was observed, and the brazing condition was examined. The results are shown in Table 1. After that, chromate treatment is carried out by the usual method.
A black coating was applied, and the adhesion properties of these films are also listed in Table 1 as chromate properties and paintability. In addition, in order to evaluate the corrosion resistance of the capacitor after this coating, JIS H868
A CASS test was carried out for 500 hours based on 1, to examine the presence or absence of through pitting corrosion, and the results are also listed in Table 2.

Furthermore, for comparison, the characteristics of the serpentine type capacitor assembly shown in FIG. 3, which was brazed using the conventional method shown below, were investigated.

That is, after degreasing this assembly with an organic solvent, a 10% KAlQFI suspension was applied and dried at 200°C for 10 minutes. Then dew point -40°C2 oxygen concentration 1
This assembly was inserted into an electric furnace purged with a 100 pp nitrogen gas atmosphere and maintained at 610°C for 5 minutes at 610°C.
Brazing was performed by heating for a minute.

The subsequent steps were carried out in the same manner as in the above invention example, and the brazed capacitor was subjected to the same evaluation tests as above, and the results are shown in Table 1.

As is clear from Table 1, the surface of the capacitor after brazing by the method of the present invention was clean and the brazing condition was good. Furthermore, the chromate property and paintability were also good, and the corrosion resistance was also good.

On the other hand, in the case of a capacitor manufactured by the conventional method, the flux residue is thick and non-uniformly adhered to the entire surface of the capacitor, which is unfavorable in terms of appearance. Although the brazing condition was good, the chromate treatment and painting after brazing were uneven, and with regard to corrosion resistance, through-pitting corrosion occurred at the bent portion (4) of the pipe material (1) in FIG. 3.

〔Effect of the invention〕

As described above, according to the present invention, compared to conventional brazing properties, the manufacturing process of heat exchangers for automobiles, etc. can be shortened, resulting in lower manufacturing costs, and the surface of the parts after brazing is clean. It has good surface treatment properties in post-treatments such as chromate treatment, and has significant industrial effects such as improved quality such as excellent corrosion resistance.

[Brief explanation of the drawing]

Figure 1 is a side view showing an example of a doron cup type evaporator, Figure 2 is a side view showing an example of a parallel flow type condenser, and Figure 3 is an example of a serpentine type condenser, which is a heat exchanger for air conditioners. FIG. 4 is an enlarged side view showing the fin portion of FIG. 3. 1-1-Pipe material 2-Corrugated fin 3-Connector 4-Bent part Fig. 1 Fig. 2

Claims (1)

[Claims] (1) In a method of brazing Al or AlQ alloy through a brazing material, the parts to be brazed are brazed in a non-oxidizing atmosphere in which KSnF_3 vapor is present. Vapor phase brazing method.