JPH02284767A - Vapor phase soldering method of al or al alloy - Google Patents

Abstract

PURPOSE:To inexpensively obtain a soldering member having excellent performance by subjecting Al or Al alloy to a vapor phase soldering in a nonoxidative atmosphere in which the vapor of a fluoride and the vapor of Zn exist. CONSTITUTION:Members consisting of the Al or Al alloy are subjected to the vapor phase soldering in the nonoxidative atmosphere where the vapor of the fluoride consisting of, for example, potassium fluoroaluminate complex and/or cesium fluoroaluminate complex and the vapor of the Zn exist. These vapors stick extremely little and uniformly to the assembly of the above-mentioned members and breaks the Al oxide films of the surfaces thereof to accelerate the wetting with solder. As a result, the solder flows uniformly and forms uniform fillets at the joining points of the assembly. The vapor of the Zn diffuses in the surface layer of the assembly. The production process is shortened and the production cost is reduced according to this vapor phase soldering method. The soldered members improved in corrosion resistance are thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for brazing 80 or Al alloy, which improves the performance of brazed parts and reduces manufacturing costs, for example in the manufacture of heat exchangers for automobiles. This makes it cheaper.

[Conventional technology]

Normally, when brazing Al or Al alloys, the A(11 or A(1) alloy members to be joined are fixed via a brazing filler metal whose melting point is lower than that of these Al, etc. to form an assembly. Al or A to be bonded
This is done by heating the alloy member to a temperature lower than its melting point. Generally, Al-3i alloy is used as the brazing material, and the shape of the brazing material is plate-shaped, linear, or powdered, or a composite material in which a core material made of Al or an Al alloy is coated with this brazing material. (hereinafter referred to as praising sheet).

As conventional brazing methods, a flux brazing method using a flux to remove an oxide film on the surface of the parts to be brazed and a true nitrous brazing method not using the flux are generally used.

Examples of the above-mentioned flux brazing method include a furnace brazing method in which an assembly to be joined is immersed in molten chloride-based flux and heated for brazing. However, this chloride-based flux is corrosive to Al, so the wax 1
It must be completely removed by post-washing, making the manufacturing process very complicated.

On the other hand, according to the vacuum brazing method, which involves placing the assembly to be joined in a vacuum and adding heat to the solder, there is no need for cleaning as a post-process, and the surface of the parts after brazing is also good. However, there are problems such as the need for high vacuum and material limitations.

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

This method uses, as a flux, a mixture of KAlFI, which is non-hygroscopic and non-corrosive to Al, and AlF, as described in Japanese Patent Publication No. 58-27037.
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-processing is required to remove the flux. It will be done.

[Problem to be solved by the invention]

However, the method described in the above-mentioned Japanese Patent Publication No. 58-27037 necessarily requires a coating and drying process for adhering the flux to the surface of the assembly, and the applied flux does not damage the assembly. Many of the fluxes fall off from the assembly during transport to the next process, which reduces the yield of flux that can be effectively used.Furthermore, flux residue remains unevenly on the surface of the joined parts after brazing, so conventional Compared to the vacuum brazing method, the surface is dirty and the commercial value is inferior, and the chromate treatment and black paint treatment performed in the next process to improve corrosion resistance become uneven, making their effects insufficient. There were drawbacks such as the fact that it was no longer available.

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.

Furthermore, for example, in the servo-tine type capacitor shown in FIG. 4, a method is adopted in which the tube is coated with Zn prior to brazing to improve corrosion resistance. As a coating method, zincate treatment, Zn thermal spraying treatment, etc. are used, but either method is a complicated process and increases the cost.

Furthermore, when brazing Mg-containing Al alloy members in a furnace using the above-mentioned fluoride flux, the brazing method is inferior to the conventional one, so in order to obtain an industrially stable brazing method, it is necessary to The Mg content in the Al alloy that is the member is 0.6
It must be less than wtX (hereinafter wtX is simply abbreviated as %).

Furthermore, with an Al alloy member containing 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 flux react during the brazing heat, and as a result, the composition of the flux changes and its effectiveness as a flux is lost.
This is because the Mg in the Al alloy diffuses into the surface layer, increasing the Mg concentration in the surface layer, and phenomena such as flux entering the surface layer of the Al alloy occur and inhibit the flow of the solder. It is.

The fact that Al alloy members with 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.

[Means to solve the problem]

In view of this, as a result of various studies, the present invention has developed a vapor phase brazing method for Al or Al alloy that does not require the process of directly applying flux to the assemblies to be joined.
A method of brazing C or Al alloys through a brazing material, which is characterized by brazing the parts to be brazed in a non-oxidizing atmosphere in which fluoride vapor and Zn vapor are present. It is effective that the fluoride vapor consists of one or both of a potassium fluoroaluminate complex and a cesium fluoroaluminate complex.

[Effect]

In this way, the members to be bonded are placed in a non-oxidizing atmosphere in which fluoride vapor, particularly vapor consisting of one or two of potassium fluoroaluminate and cesium fluoroaluminate complex, and Zn vapor are present. By placing the assembly as a base, these vapors will uniformly adhere to the assembly in a very small amount and destroy the Al oxide film on its surface, promoting acclimatization of the wax, and as a result, the wax will flow uniformly. , a uniform fillet is formed at the joint of the assembly and Z
n vapor diffuses into the surface layer of the assembly. Since this diffused layer has a lower potential than the undiffused layer, it becomes a sacrificial layer and has the characteristic of improving corrosion resistance. Furthermore, this vapor combines with moisture and oxygen in the atmosphere to make the atmosphere more non-oxidizing, which has the effect of preventing oxidation of the material surface.

Further, as a potassium fluoroaluminate complex that can be used in the brazing method of the present invention, the specific chemical formula is KAlF
4. General formula K, A of KtAlFs, AlF6, etc.
Vapors of compounds represented by OF −, 3, KAlF, +KzAlFs, which are mixtures thereof.

KAlF4+ KyAlFe, KzAlFs+KvAl
Fs.

KAlF, + to -+A (2F, , 2 and 2AlF
, + contains vapors such as 2AlF, , and further K
Also included are vapors generated from mixtures such as AlF4+KtAlF5.H20. In order to generate the vapor of potassium fluoroaluminate complex, KF and A, which are the raw materials for generation, are required.
A mixture of IF3 or, for example, KBF4. 2ZnF
=, a mixture of a metal complex containing K and F but excluding Al, such as KzZrFa, KzSiF6, etc., and metal Al, or K F + Z r F 4゜K F + K B F
4. K F + L i F, K F + S
nF2.

By heating and melting a mixture of a fluoride containing KF such as KF+ZrF or 10-NaF and metal A&, KAl
Any device that generates a vapor of potassium fluoroaluminate complex containing F as a main component can be used.

In addition, the specific chemical formula of the cesium fluoroaluminate complex that can be used in the brazing method of the present invention is C8Al
F 4 , Cs 2 A OF s or cssAlF
Vapors of compounds represented by the general formula Cs, AOF-)3 such as 6, C5AlF which is a mixture thereof, +C
52AlF 5+ C3A0F t +CSa AlF
s, C52AlF s+Cs3A (?Fa, C5A
(llF++cs, -+AlF, , 2 and C5zA
This includes vapors such as IFs+C5a-zAlF, ++, and also includes vapors generated from mixtures such as C5AlF4+C52AlF5.H=O. Note that in order to generate vapor of cesium fluoroaluminate complex, CsF and Al
A mixture containing F3 and another fluoride such as KF can also be used as long as the vapor of the cesium fluoroaluminate complex is substantially generated. For example, LiF+Na
F+CsF, LiF+CsF, CsF+PbF2. KF
Even if it is a mixture such as +CsF, CsF+ZrFs, etc., by heating and melting it in the coexistence with metal Al,
Any device that generates vapor of cesium fluoroaluminate complex can be used.

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

Furthermore, by having vapors of such potassium fluoroaluminate complexes or cesium fluoroaluminate complexes present in a non-oxidizing atmosphere, the assembly can be completely covered with vapor, resulting in lower vapor density and reduced flux consumption. can be reduced. Note that as the non-oxidizing atmosphere, for example, nitrogen, argon, carbon oxide, or any other atmosphere can be used.

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.

Furthermore, according to the present invention, even Al-Mg alloys containing more than 0.6% Mg can be brazed. This is because the vapor of the potassium fluoroaluminate complex and the senium fluoroaluminate complex is extremely small, and 17 also adheres uniformly to the assembly. For this reason, the reaction between the vapor of the cesium fluoroaluminate complex, which acts as a flux, and the Mg in the material is extremely small.
Therefore, the effect of the vapor as a flux is not inhibited,
In addition, Mg does not diffuse into the surface layer within the Mg-containing material, causing a difference in Mg concentration within the material (furthermore, since the amount of flux components that penetrate into the surface layer of the material is small, the wax flow does not occur). This is because it will not be hindered.

If the vapors of potassium fluoroaluminate complex or cesium fluoroaluminate complex are used in this way, it is possible to braze without directly applying flux to the assembly, but due to the structure of the assembly, these vapors are not present. Heat exchangers that have 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, have difficult joints. Internal brazing is generally difficult. Therefore, in such a case, a fluoride such as potassium fluoroaluminate complex or cesium fluoroaluminate complex is applied to the joints inside the assembly in advance and dried, and the joints outside the assembly are kept in a non-condensed area where the vapor is present. An effective method is brazing in an oxidizing atmosphere. In addition, partial application of fluorides such as potassium fluoroaluminate complex or cesium fluoroaluminate complex is not limited to the inside of the assembly, but can also be applied to the outside of the assembly, for example, if the shape of the joint is complex, it may be difficult to apply only these vapors. If brazing is difficult, a fluoride such as potassium fluoroaluminate complex or cesium fluoroaluminate complex may be directly applied to the part.

〔Example〕

Next, examples of the present invention will be described.

<Example 1> As shown in Fig. 3, JIS A3003 (A to '-C1
l 0.05-0.20%-Mn 1. (]-11,5
%A□J containing 6.8 to 8.2% Si on one side of the alloy core material
IS A4343 JI clad with Al alloy brazing filler metal
Thickness 1 made of plating sheet of S BA12PC
One end edge of the rolled plate (1) of mm is each 1III in thickness as shown in Table 1! Assemble a reverse 1゛ joint test piece on the A<7 alloy plate (2) surface of 1 with both plates (1) and (2) in contact with each other at right angles, and perform brazing under the conditions shown below. , the brazing situation was investigated.

That is, 1. shown in Table 1. : 45xKF-55! %A
A mixture of 8 parts lF v and 2 parts Zn powder, 12% K F-52% C5F-36''%
Mixture of AlFs mixture at a ratio of 8 parts and Zn powder to 2 parts L7 [compound or ha 50XK B F, -50% Al
Weigh out 500 g of a mixture of 8 parts powder and 2 parts Zn powder per internal volume l111' of the brazing part, place it in the brazing part, and in each case, place it inside this furnace. Dew point -40℃, oxygen concentration 110℃
The furnace was replaced with a 0pp nitrogen gas atmosphere, and the inside of the furnace was heated to 610℃.
It was kept at °C. Then, the inverted T-joint test piece shown in Figure 3 using the Al alloy plate shown in Table 1 was inserted into this furnace after being degreased with an organic solvent, and the assembly was heated at 610°C for 5 minutes to braze it. was carried out. At this time, as shown in Table 1, it is the steam generated from the above mixture that acts as a flux for each test piece.

After that, take out the inverted T-joint joint of the brazed part above outside the furnace and check the brazing condition.
These results are shown in Table 1, with marks marked as "X" and those with poor brazing conditions marked as "X". Furthermore, the surface of the wax area was observed, and those that were clean were marked O, and those that were dirty with a lot of residue were marked X, and they were also listed in Table 1.

In addition, the bonded products were subjected to the <CASS test for 200 hours based on JIS 28681, and those with a pitting depth of less than 2007a are marked with an ○, and those with a pitting depth of 200 or more are marked with an X, and are also listed in Table 1.

In addition, as a conventional method, the above-mentioned rolled plate (1) and the Al alloy plate (2) in Table 1 are assembled into an inverted T-joint test piece as shown in Fig. 3, and after degreasing, this assembly is coated with KAlF at lo% concentration. After that, the assembly was inserted into an electric furnace which was replaced with a nitrogen gas atmosphere with a dew point of -40°C and an oxygen concentration of 1100pp as described above, and the inside of the furnace was maintained at 610°C. Brazing is performed by heating at 610°C for 5 minutes,
Similarly, the brazing situation was investigated and the results are also listed in Table 1.

As is clear from Table 1, the present invention method No. 1 to N.

, 8 had good brazing methods, and particularly good brazing was achieved even with Mg-containing materials. Furthermore, the surface appearance was clean and the corrosion resistance was also good.

On the other hand, conventional method No. 9 was able to perform brazing, but had uneven residue adhering to the surface and was poor in corrosion resistance.

Also, conventional method No. 10 A12-1. (Brazing was not possible with 1% Mg material.

<Example 2> As shown in FIG. 4, a JIS A1050 tube material (3) hot-extruded into a tubular shape by a conventional method is bent into a serpentine shape, and Al-IXMn is inserted between the serpentine tube material (3). -4%Z
n alloy as the core material, Al-10%5t-1% on both sides
A corrugated fin (4) made of a plating sheet with a thickness of 0.16 m+a clad with Zn alloy skin material is sandwiched between the corrugated fins (4) and
g A serpentine type capacitor was assembled by attaching the alloy colored connector (5). Note that the joint between this corrugated fin (4) and connector (5) is JIS A1070 (A (1199, 70X or higher)).
They were joined by TMG welding using a welding rod.

This assembly was then degreased with an organic solvent and then 50% KAl
Weigh out 500 g of a mixture of F, -50% C5AlF, mixed at a ratio of 8 to 2 parts Zn powder per 1 m3 of internal volume of the brazing part, place it in the brazing electric furnace, and reduce the dew point to -40°C. This assembly was inserted into the above-mentioned furnace which was purged with a nitrogen gas atmosphere having an oxygen concentration of 1100 pp and maintained at 610°C, and the assembly was heated at 610°C for 5 minutes to perform brazing.

The capacitor in the brazing metal portion was taken out of the furnace and the appearance of the surface was observed, and the brazing condition was also examined, and the results are shown in Table 2. 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 2 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 1000 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. 4 brazed by the conventional method shown below were investigated.

That is, this assembly was degreased with an organic solvent (and then 10%
A concentrated KAlF4 suspension was applied and dried at 200° C. for 10 minutes. Then the dew point was -40°C.

Replaced with a nitrogen gas atmosphere with an oxygen concentration of 1.00 ppm,
This assembly was inserted into an electric furnace maintained at 610°C and heated at 610°C for 5 minutes to perform brazing.

The subsequent steps were carried out in the same manner as in the invention example described above, 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 also 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 thick and unevenly adhered to the entire surface, 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 (6) of the pipe material (3) in FIG. 4.

〔Effect of the invention〕

As described above, according to the present invention, compared to the conventional brazing method, 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 excellent surface treatment properties in post-treatments such as chromate treatment, has improved quality such as excellent corrosion resistance, and is also capable of brazing alloys containing a large amount of Mg, providing remarkable industrial effects. It is something.

[Brief explanation of drawings]

Fig. 1 is a side view showing an example of a Dron cup type evaporator, Fig. 2 is a side view showing an example of a parallel flow type condenser, Fig. 3 is a perspective view showing an inverted T-joint test piece, and Fig. 4 is a side view showing an example of a parallel flow type condenser. FIG. 5 is a perspective view showing an example of a serpentine type condenser which is a heat exchanger for an air conditioner, and FIG. 5 is a side view showing an enlarged fin portion of FIG. 4. l - Rolled plate 2 - Al alloy plate 3 Tube material 4 - Corrugated fin 5 - Connector 6 - Bent part Fig. 2 Fig. 3 Fig. 4 Fig. 5

Claims (2)

[Claims] (1) In a method of brazing Al or Al alloy through a brazing material, the parts to be brazed are heated with fluoride vapor and Zn.
A vapor phase brazing method for Al or Al alloy, characterized by brazing in a non-oxidizing atmosphere in the presence of steam. (2) The method for vapor phase brazing of Al or Al alloy according to claim (1), wherein the fluoride vapor comprises one or both of a potassium fluoroaluminate complex and a cesium fluoroaluminate complex.