JPH0335874A - Vapor phase brazing method for al or al alloy - Google Patents

Abstract

PURPOSE:To shorten a stage and to improve the quality by brazing Al or Al alloys in a nonoxidative atmosphere where the vapor emitted from the melt of ZnCl2 exists in the case of brazing the Al or Al alloys via a brazing material of an Al-Si system. CONSTITUTION:The assembly of the Al or Al alloy members is placed in the nonoxidative atmosphere where the vapor consisting of the melt of the ZnCl2 exists, by which the vapor is extremely slightly and uniformly stuck to the assembly. Since the oxide film of the Al on the surface is broken, the wetting of the solder is accelerated to maintain the uniform flow of the solder. A uniform fillet is formed at the joint point of the assembly. The production stage is shortened and the quality is improved in the way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for brazing Al or Al alloy, and is used to improve the performance of brazed parts, for example, in the manufacture of automobile heat exchangers. At the same time, manufacturing costs can be reduced.

[Conventional technology]

Normally, in brazing Al or Al alloy, the Al or Al alloy members to be joined are fixed together through a brazing filler metal whose melting point is lower than that of AA+, etc., and the melting point is higher than that of the brazing filler metal, This is done by heating the At or Al alloy member to a temperature lower than its melting point. As the brazing material, an Al-Si alloy is generally used, and its shape is a plate.

It is used as a brazing material in the form of a wire or powder, or as a laminated material (hereinafter referred to as a plating sheet) in which a core material made of Al or A7 alloy is coated with the brazing material.

As conventional brazing methods, flux brazing, which uses flux to remove the oxide film on the surface of the parts to be brazed, and vacuum brazing, which does not use flux, are commonly used. The above-mentioned flux brazing properties include furnace brazing properties in which a chloride-based flux is applied to the assembly and heated for brazing. However, this chloride flux is Al
On the other hand, since it is corrosive, 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 subjected to brazing heat, does not require cleaning as a post-process, and the surface of the parts after brazing is also good. There are problems such as the need for high vacuum and material limitations.

Furthermore, recently, a method of brazing in a furnace using fluoride-based flux has come to be 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 KAlF4, which is non-hygroscopic and non-corrosive to Al, and 3^IF6 as a flux.
This is suspended in water 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 is required to remove the flux. .

[Problem to be solved by the invention]

However, the method described in Japanese Patent Publication No. 58-27037 necessarily requires coating and drying steps to adhere the flux to the surface of the assembly. Many items fall off from the assembly during transport, and as a result, the yield of effectively used flux is low. In addition, 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. There were drawbacks such as the black coating treatment becoming non-uniform and its effects not being fully exhibited.

Furthermore, since 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, making it impossible to obtain a sufficient corrosion protection effect. There are cases.

Furthermore, when brazing Mg-containing Al alloys in a furnace using fluoride flux, the brazing properties are inferior to conventional ones, so in order to obtain industrially stable brazing properties, it is necessary to
The content of W1% must be less than 9.5v1% (hereinafter W1% will simply be abbreviated as %). If the Al alloy contains more Mg than this, brazing becomes difficult even if the amount of flux applied is increased. The cause of this is that the Mg in the Al alloy and the fluorine in the flux react with each other during brazing heat, and as a result, the composition of the flux changes and its effectiveness as a flux is lost.
This is because phenomena such as g diffusing into the surface layer increases the Mg concentration in the surface layer, and phenomena such as flux entering the surface layer of the Al alloy and inhibiting the flow of the solder occur. The fact that Al alloys with such a high Mg content cannot be used as a material for heat exchangers has been a major obstacle in terms of durability and weight reduction of heat exchangers.

Furthermore, when manufacturing the capacitor shown in FIG. 2, for example, in order to improve corrosion resistance, the pipe material (
3) requires a step of coating the surface with Zn, which is a factor in increasing manufacturing costs.

Means for Solving Problem c] In view of this, as a result of various studies, the present invention has developed vapor phase brazing properties of Al or Al alloy that do not require the process of directly applying flux to the assemblies to be joined. With things, i
Alternatively, a method of brazing an Al alloy through an Al-3i alloy brazing filler metal is characterized in that these members are brazed in a non-oxidizing atmosphere in which vapor from ZnCl□ is present.

[Effect]

By placing the assembly as the members to be joined in a non-oxidizing atmosphere containing vapor from the molten znCI2, this vapor adheres uniformly to the assembly in a very small amount and removes the Al on its surface. Since it destroys the oxide film, it promotes wetting of the wax and has the characteristic that the wax flows like a wax and forms a uniform fillet at the joints of the assembly.

To generate this steam, ZnCl□ can be placed in advance in the furnace where the brazing will be carried out, and when the temperature of the furnace is raised, it can be evaporated at the same time, or this steam can be generated outside the furnace. It is also possible to generate nitrogen gas and supply it into the furnace using nitrogen gas or the like as a carrier.

Furthermore, the presence of this vapor in a non-oxidizing atmosphere allows the assembly to be completely covered with vapor, thereby requiring less vapor density and reducing flux consumption. Note that the non-oxidizing atmosphere is, for example, nitrogen or argon.

- Can be used in any atmosphere including carbon oxide.

Although it is preferable to use a highly airtight furnace to carry out the present invention, even in a less airtight furnace, the assembly to be joined is 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.

Furthermore, according to the present invention, even Al--Mg alloys containing more than 0.6% of Mg can be brazed. This is due to the steam coming out from the melt of zIIC12 and the Mg in the alloy.
This is because they do not react.

Furthermore, Zn in the steam diffuses onto the surface of the brazed object during brazing,
A Zn diffusion layer with a Zn concentration of 2% and a depth of about 50 μm is formed. Since this layer is potentially less noble than the undiffused layer,
Corrosion resistance is improved because it protects the undiffused layer and prevents through-pitting corrosion.

Therefore, Zn coating treatment in the pre-brazing process becomes unnecessary.

If XnC1□ steam is used in this way, it is possible to braze without directly applying flux to the assembly, but due to the structure of the assembly, there are some problems with the heat exchanger having joints inside the assembly. It is generally difficult to braze the internal parts of these materials using steam. Therefore, in such cases, conventional chloride-based flux or fluoride-based flux such as potassium fluoroaluminate complex is applied in advance to the joints inside the assembly and dried, and these fluxes are applied to the joints outside the assembly. An effective method is to perform brazing in a non-oxidizing atmosphere in the presence of XnC12 vapor without coating. In addition, partial application of chloride-based flux or fluoride-based flux is not limited to the inside of the assembly, but can also be applied to the outside, for example, if the joint shape is complex and it is difficult to braze only with steam. Alternatively, these conventional fluxes may be applied directly.

〔Example〕

Next, examples of the present invention will be described.

Example 1 The inverted T-joint test piece shown in FIG. 1 was assembled and brazed together by the method of the present invention. That is, jlsA3003 (A I-Cu
U with O, O5~0.20%-Mn 1.0~1.5% gold alloy as the core material, and both sides of this core material clad with JIS 4343 AJ gold alloy filler material containing Si6.8~8.2%.
Thickness 1 consisting of plating sheet of S B^12PC
■ Rolled plate (1) and JIS Al050. IIs
A3003゜A#-0.8%Mg alloy thickness 1iw+
The rolled plates (2) were assembled and degreased with an organic solvent.

Then, the assembly is brazed at 500 g per 1 d of internal volume of the furnace.
of zaClz was placed on a stainless steel tray. Then, this assembly was inserted into an electric furnace maintained at 610°C and replaced with a nitrogen gas atmosphere with a dew point of -40°C and an oxygen concentration of 10 Opp-, and the assembly was heated at 610°C for 5 minutes to perform brazing. did.

The re-brazed joints were taken out of the furnace and examined for their brazing conditions, and the results are shown in Table 1, with good brazing conditions marked as ○ and poor brazing conditions marked as X.

As a conventional method, KAlFJ at a concentration of 10% is applied to the degreased assembly, and after drying, the dew point is -40°C.

It was replaced with a nitrogen gas atmosphere with an oxygen concentration of 1100 pp, and
This assembly was inserted into an electric furnace maintained at 10° C., and the assembly was heated at 610° C. for 5 minutes to perform brazing. The results are summarized in Table 1.

Table 1 As is clear from Table 1, the method of the present invention, PkLl-Nα3, had good brazing properties, and particularly good brazing was achieved even with Mg-containing materials. In contrast, Al-0 of conventional method M6
, 8%Mg alloy material could not be brazed.

Example 2 As shown in Fig. 2, an Al-0.5% Cu alloy tube (3) hot-extruded into a tubular shape by a conventional method is bent into a serpentine shape, and between the serpentine tubes (3) 11SA3003 (
1-1% Mn- (1,1% Cu alloy) is used as the core material, and JISA4343 (Al-7% Si alloy) is used as the skin material on both sides, each cladding at a ratio of 10% to a thickness of 0. l
A corrugated fin (4) made of 6nn++ plating sheet is sandwiched, and An-4,3%Zn-IJ%
A Mg-all-Mg connector (5) was TIG welded using a ^1070 welding rod, a serpentine type capacitor was assembled, and it was degreased with an organic solvent.

This assembly was then brazed by the method of the present invention. In other words, the total weight of the assembly is 500g per internal volume ITd of the brazing furnace.
2nC1□ was placed on a stainless steel tray. This assembly was then inserted into an electric furnace maintained at 610°C and replaced with a nitrogen gas atmosphere with a dew point of -40°C and an oxygen concentration of 1100pp, and the assembly was heated at 610°C for 5 minutes to perform brazing. , a trace amount of CI after being taken out of the furnace and cooled.
! To remove this, the sample was washed with hot water at 80°C for 1 minute and dried.

Regarding this, the appearance of the capacitor surface was observed, and the brazing condition was also investigated, and the results are shown in Table 2.

The joining rate in the brazing situation is expressed as [(total number of fins - number of unbonded fins)/total number of fins x 1θO, and the length of the fillet in the brazing situation is determined by the tube material ( 3) and the fin material (4) are expressed by the length A at the joint portion.

Thereafter, chromate treatment and black coating were performed using a conventional method, and the adhesion properties thereof are also listed in Table 2 as chromate properties and paint properties.

In addition, in order to evaluate the corrosion resistance of the capacitor after this coating, the CASS test was conducted at 50[1] based on JISHg6g+.
The test was carried out for several hours to determine the presence or absence of through pitting corrosion, and the results are also listed in Table 2.

For comparison, the characteristics of the capacitor assembly shown in FIG. 2, brazed using a conventional method, were investigated.

That is, after degreasing the assembly shown in Figure 2 with an organic solvent, a 10% concentration X^IL suspension was applied, and the mixture was heated at 200°C for
Drying was performed for minutes. Thereafter, this assembly was inserted into an electric furnace maintained at 610°C and purged with a nitrogen gas atmosphere having a dew point of -40°C and an oxygen concentration of 1100pp, and brazing was performed by heating at 610°C for 5 minutes.

The subsequent steps were carried out in the same manner as in the above invention method, and the brazed capacitor was subjected to the same evaluation tests as above, and the results are shown in Table 2.

As is clear from Table 2, 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 capacitor manufactured by the conventional method, flux residue is thickly 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 as for corrosion resistance, through-pitting corrosion occurred in the pipe material.

〔Effect of the invention〕

As described above, according to the present invention, compared to conventional brazing properties, the manufacturing process for heat exchangers for automobiles, etc. can be shortened, resulting in lower manufacturing costs, and the surface after brazing is clean, making it easier to use chromate. It exhibits remarkable industrial effects, such as improved surface treatment properties in post-treatments, superior corrosion resistance, and the ability to braze alloys containing a large amount of Mg.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of an inverted T-joint test piece, Figure 2 is a perspective view of an example of a serpentine type condenser, which is a heat exchanger for air conditioners, and Figure 3 is an enlarged view of the fin portion of Figure 2. FIG. Blazing Sea Al Alloy Tube Fin Connector

Claims (1)

[Claims] A method of brazing Al or Al alloy through an Al-Si alloy brazing material, which is characterized in that these parts are brazed in a non-oxidizing atmosphere in which vapor from ZnCl_2 is present. Vapor phase brazing method.