JPH0390274A - Vapor brazing method for al or al alloy - Google Patents

Abstract

PURPOSE:To shorten the production process for the heat exchanger of automobiles, etc., by brazing Al members in a nonoxidative atmosphere where the vapor emitted from the reaction melt of ZnCl2 and Al exists. CONSTITUTION:A rolled plate 2 of Al or Al alloy is brazed to a brazing sheet 1 formed by using Al or Al alloy as a core material and cladding a Al brazing material thereto. The two sheets 1, 2 are brazed in the nonoxidative atmosphere where the vapor emitted from the reaction melt of the ZnCl2 and Al exists. The brazing is executed by heating for 5 minutes at 610 deg.C in an electric furnace contg. a mixture composed of 200g ZnCl2 and 200g Al powder per 1m<3> inside volume of the brazing furnace. The improved quality, such as improved corrosion resistance, is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for brazing Al or Al alloy, and is used to improve the performance of brazed members, for example, in the manufacture of heat exchangers for automobiles. This also reduces the manufacturing cost.

[Conventional technology]

Normally, in brazing Al or Al alloy, the Al or Al alloy members to be joined are fixed together via a brazing filler metal whose melting point is lower than that of Al, etc., and the melting point is higher than that of the brazing filler metal. This is done by heating to a temperature lower than the melting point of the Al or Al alloy members to be joined. Generally, Al-3i alloy is used as the brazing material, and its shape is a plate.

It is used as a laminated material (hereinafter referred to as a plating sheet) in which a wire or powdered brazing material or a core material made of Al or A4 alloy is coated with this brazing material.

As conventional brazing methods, flux brazing, which uses flux to remove an oxide film on the surfaces of 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-based flux is
Since it is corrosive to L, 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 and heating, 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 a fluoride flux has been 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 AtF6 and KAlF4, which is non-hygroscopic and non-corrosive to l, as a flux, and suspends this in water. It is applied to the surfaces of the assemblies to be joined and brazed, and its feature is that since it uses non-corrosive flux, 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 coating and drying steps to adhere the flux to the surface of the assembly. Many items fall off from the assembly during transport, and therefore the flux that can be used effectively is reduced. 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. There were drawbacks such as the treatment, black coating, etc. becoming non-uniform and the 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 must be less than 0.6 wt% (hereinafter wt% is simply 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 J in the Al alloy and fluorine, which is a flux component, 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.
diffuses into the surface layer, increasing the Mg concentration in the surface layer,
This is because phenomena such as flux entering the surface layer of the Al alloy occur and inhibiting the flow of the solder. 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 tube material (3
) is required, which is a factor in increasing manufacturing costs.

[Means to solve the problem]

In view of this, as a result of various studies, the present invention has developed vapor phase brazing properties that do not require the process of directly applying flux to the assemblies to be joined. In the method of attaching Al or Al
The method is characterized in that alloy parts are brazed in a non-oxidizing atmosphere in the presence of steam from a reaction melt of ZnCl2 and Al.

[For production]

By placing the assembly, which is the member to be joined, in a non-oxidizing atmosphere in which steam from the reaction melt of ZnC1z and Al exists, a very small amount of this vapor will uniformly adhere to the assembly and cause its damage. Since it destroys the Al oxide film on the surface, it promotes wetting of the solder, and has the characteristic that the solder flows in a uniform manner and forms a uniform fillet at the joints of the assembly.

To generate this steam, ZnC12 and Al powder are mixed uniformly, or ZnC is placed on an Al tray.
1, placed in advance in the furnace where brazing is to be carried out,
When the temperature of the furnace is raised, the vapor may be simultaneously evaporated using the heat, or it is also possible to generate this steam outside the furnace and supply it into the furnace using nitrogen gas or the like as a carrier. Furthermore, by having this vapor in a non-oxidizing atmosphere, the assembly can be completely covered with vapor, so less vapor density is required and flux consumption is reduced. Note that as the non-oxidizing atmosphere, for example, nitrogen, argon, carbon oxide, or any other atmosphere can be used.

Furthermore, in order to carry out the present invention, it is preferable to use a highly airtight furnace, but even if a furnace with a poor airtightness is used, the assembly to be joined is placed in a container made of stainless steel or the like and ZnCA'2 and A
It can be easily brazed by placing it together with a mixture of ZnCl2 powder or in an Al container together with ZnCl2 and heating it for brazing.

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 of the ZnCA'z melt and the M in the alloy.
This is because it does not react with g.

Furthermore, Zn in the steam diffuses onto the surface of the brazing object during the soldering process,
A Zn diffusion layer with a Zn concentration of 2% and a depth of about 5 (11 m) is formed. Since this layer has a lower potential than the undiffused layer, it is made with corrosion resistance to protect the undiffused layer and prevent through-hole corrosion. Therefore, Zn coating treatment in the pre-brazing process becomes unnecessary.

〔Example〕

The present invention will be described below with reference to Examples.

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, Its＾3003 CAl-Cu
J containing O,05~0.20%-Mnt,[l~l,5%) alloy as a core material and containing Si6,8~8.2% on one side.
ItsB clad with IS 4343 Al alloy brazing filler metal
^Thickness 1 consisting of 12pcs plating sheet (1)
mnc7) Rolled plate Its Al050. JIS A
3003. A 1-thick rolled plate (2) of Al-0°8%Mg was assembled and degreased with an organic solvent.

Then, the assembly was placed on a stainless steel tray containing a mixture of 200 g of ZnCl2 and 200H Al powder per inner volume of the brazing furnace, and the dew point was -40°C.
This assembly was inserted into an electric furnace that was purged with a nitrogen gas atmosphere with an oxygen concentration of 1 ppm and maintained at 610°C, and was heated at 610°C for 5 minutes to perform brazing.

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

In addition, as a conventional method, 10% concentration of KA and gF4 is applied to the above degreased assembly, and after drying, the air is replaced with a nitrogen gas atmosphere with a dew point of -40°C and an oxygen concentration of 1100pp, and the temperature is maintained at 610°C. Insert this assembly into the
Brazing was performed by heating at 10° C. for 5 minutes. The results are summarized in Table 1.

As is clear from Table 1, invention examples No. 1 to No. 0.
In No. 3, the brazing properties were good in all cases, and particularly good brazing was achieved even with the Mg-containing material. On the other hand, brazing was not possible with the AJ-0.8% Mg material of Conventional Example No. 6.

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) JISA3003C
Al-1%Mg) as the core material, and JIS^43 on both sides.
43 CAl-7%Si) cladding material at a ratio of 10% to a thickness of 0. A corrugated fin (4) made of IBM plating sheet is sandwiched, and Al-4,3
%Zn-1.3%Mg alloy connector (5) with AlO? A serpentine type capacitor was assembled by TIG welding using a No. 0 welding rod and degreased with an organic solvent.

Then, this assembly is
The assembly was placed on an Al tray on which 350 g of ZnCl2 was placed, and the assembly was inserted into an electric furnace maintained at 610 °C and purged with a nitrogen gas atmosphere with a dew point of -40 °C and an oxygen concentration of 10 tlppm. The assembly was heated at 610° C. for 5 minutes to perform brazing, taken out from the furnace, cooled, and then washed with hot water at 80° C. for 1 minute to remove traces of CI, and then dried.

The appearance of the surface of the capacitor after brazing was observed, and the brazing condition was examined. The results are shown in Table 2.

Thereafter, chromate treatment and black coating were carried out using conventional methods, and the adhesion properties thereof are shown in Table 2 as chromate properties and paint properties.

Furthermore, in order to evaluate the corrosion resistance of the capacitor after coating, a <CASS test was conducted for 500 hours based on 11588681, and the presence or absence of through pitting corrosion was examined and the results are also listed in Table 2.

As a conventional example, for comparison, the characteristics of the capacitor assembly shown in FIG. 2, which was brazed using a conventional method, were investigated.

That is, after degreasing the assembly shown in Fig. 2 with an organic solvent, a 10% concentration KAlFa suspension was applied and the mixture was heated at 200°C.
Drying was performed for 0 minutes. Thereafter, this assembly was inserted into an electric furnace maintained at 610°C and purged with a nitrogen gas atmosphere with a dew point of -40°C and an oxygen concentration of 1100pp, and brazed by heating with filF for 5 minutes.

The subsequent steps were carried out in the same manner as in the above-mentioned examples of the present invention, and the brazed capacitors were subjected to the same evaluation tests as above, and the results are shown in Table 2.

Table 2 Note 1) Note 2) Bonding rate (%) = ((Total number of fin ridges - Number of unbonded ridges)/Total number of fin ridges)
X 1tlf) Fillet length (mm) refers to the joining length shown by A between the tube material (3) and the fin (4) shown in FIG.

As is clear from Table 2, the surface of the re-brazed capacitor according to 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, the flag residue is thickly and non-uniformly adhered to the entire surface of the capacitor, which is unfavorable in terms of appearance. Furthermore, although the brazing condition was good, the chromate treatment and painting for brazing replacement were uneven, and as for corrosion resistance, through-pitting corrosion occurred in the pipe material.

[Effects of the Invention] As described above, according to the present invention, the manufacturing process for heat exchangers for automobiles, etc., can be shortened compared to conventional brazing properties, resulting in lower manufacturing costs, and the surface of re-brazing can be reduced. Because it is clean, it has good surface treatment properties in post-treatments such as chromate treatment, improves quality such as excellent corrosion resistance, and has remarkable industrial effects such as being able to braze alloys containing a large amount of Mg. It is something.

[Brief explanation of drawings]

Figure 1 is a perspective view of an inverted T-joint test piece, Figure 2 is a perspective view of an example of a serpentine condenser, which is a heat exchanger for air conditioners, and Figure 3 shows the joint between the tube and fin in Figure 2. It is an enlarged side view. l... Placing seat 2... Al alloy 3... Tube material 4... Fin 5... Connector Fig. 1 Fig. 2 Fig. 3 Fig. L-a -J

Claims (1)

[Claims] (1) In a method of brazing Al or Al alloy through an Al alloy brazing material, the Al or Al alloy member is
1. A vapor phase brazing method for Al or Al alloy, characterized in that brazing is carried out in a non-oxidizing atmosphere in the presence of steam from a reaction melt of l_2 and Al.