JPS61266174A - Brazing method for aluminum material - Google Patents

Abstract

PURPOSE:To suppress the evaporation rate of zinc and to prevent the decrease of a corrosion preventive effect by subjecting an Al material, etc. coated with zinc to a preliminary heating treatment for the prescribed time in the atm. prior to soldering of said material in a furnace. CONSTITUTION:A condenser core 1 is tentatively assembled of a core material and fins constituted of the Al or Al alloy material. The core is first put into a preheating furnace 2 and is preheated for 5-60min at 400-580 deg.C. The zinc of the surface layer of the tube is oxidized and an oxide film is formed thereon. The preheated condenser core 1 is fed into a brazing furnace 3 in which an inert gaseous atmosphere of gaseous nitrogen is maintained. The core is heated to the prescribed temp. and is brazed via a non-corrosive flux. The oxide film formed by the preheating decreases considerably the evaporation rate of zinc. The decrease of the corrosion preventive effect arising from the decrease in the quantity of zinc is thus prevented.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a method of brazing aluminum or aluminum alloy materials coated with zinc or zinc alloy in a furnace, and particularly to a method for brazing zinc or aluminum alloy coated aluminum materials in a furnace. It is designed to suppress the

(B) Conventional technology Conventionally, as shown in Fig. 4, the method of soldering each assembly part of a condenser core made of aluminum material, for example, is to add a brazing material (skin material) to the core material. Fins made of clad plating sheet material and tubes made of aluminum or aluminum alloy coated with zinc or zinc alloy are assembled to form capacitor core a, and after degreasing, fluoride-based Apply flux, put it into a brazing furnace, and then introduce nitrogen gas into the furnace for 30 to 40 nm. The temperature was increased while being pumped at a rate of 580°C to 620°C as shown in Figure 5.
The brazing process is performed by heating at a brazing temperature of 3 to 20 minutes to obtain a brazed product C.

In addition, aluminum fluoride (AlF2)-potassium fluoride (KF2), which is disclosed in U.S. Pat. A non-corrosive flux mainly consisting of a complex compound of the above type is used, and the brazing process is performed in an inert gas atmosphere.

In addition, fins made of plating sheet clad with aluminum alloy solder such as A4004, and A107
60 as a brazing method for capacitor cores, etc., which are assembled with tubes made of grade 0 aluminum alloy material.
There is also a method of brazing by heating in a vacuum of 0°C1 about 10 Torr for 3 minutes. Furthermore, here,
The degree of vacuum is usually 10-3 to 10-5 Torr.
□ (C) Problems to be Solved by the Invention] In the conventional method described in 1 above, it is difficult to find a means for suppressing zinc evaporation in the aluminum material that constitutes the capacitor core. However, since an inert gas such as nitrogen gas is pumped into the brazing furnace, the flow of the inert gas accelerates the formation of zinc and prevents the evaporation of zinc during the brazing process. The amount reaches over 30%. As a result, there is a problem that a zinc diffusion layer is not sufficiently formed on the surface of the aluminum material, and the corrosion prevention effect of zinc on the aluminum material is reduced. I had to. In addition, the interior of the furnace becomes contaminated due to increased zinc evaporation, which not only impairs the brazing function of the furnace but also causes problems in the need for earlier maintenance.

In addition, in the method of brazing aluminum materials in a vacuum using an aluminum alloy brazing shrine, in order to vacuum the furnace, the flux mainly composed of the i4H arsenide is used in an inert gas atmosphere. Compared to the brazing method, the amount of zinc evaporated is even greater, reaching 90% or more, and there are problems similar to those described above.

The present invention has been made to solve the above-mentioned conventional problems, and it suppresses the evaporation of zinc during brazing of aluminum or aluminum alloy materials coated with zinc or zinc alloy, and improves the corrosion prevention effect of aluminum materials. The purpose of the present invention is to provide a method for brazing aluminum materials that can improve the performance of brazing aluminum materials.

3) Means for Solving the Problems The method for brazing aluminum materials according to the present invention includes a method for brazing aluminum materials coated with zinc or zinc alloy before brazing the aluminum materials or aluminum alloy materials in a furnace. Preliminary heat treatment is performed in the atmosphere at 400'C to 580C for 5 to 60 minutes.

(e) Effect In the present invention, by preheating the aluminum material or aluminum alloy material to be brazed in the atmosphere before the brazing treatment, zinc oxidation is achieved on the surface of the aluminum material or aluminum alloy material. A film is formed, which suppresses evaporation of zinc during the brazing process.

(to) Examples of the invention Hereinafter, embodiments of the method of the present invention will be described based on the drawings.

FIG. 1 shows the steps of the method of the present invention, and 1 indicates A300
A fin consisting of a plating sheet made of a 0 series alloy (e.g. A3003 alloy) as a core material and clad with an aluminum alloy-mounted solder of A4343 alloy or A4004 alloy, and a 1000 series alloy (e.g. Al050 alloy).
alloy, A1070 alloy), A3000 series alloy (e.g. A
3003 alloy), 2 is a capacitor core preheating furnace in an atmospheric atmosphere, and 3 is a solder in an inert atmosphere such as nitrogen gas for brazing the preheated capacitor core 1. 4 is the capacitor core after brazing.

The temporarily assembled capacitor core I is first heated in a preheating furnace 2 at 400°C to 580°C for 5 to 60 minutes, preferably 500°C to 550°C for 210 to 15 minutes.

At this time, zinc on the tube surface layer is oxidized and an oxide film is formed. This oxide film makes the surface layer a barrier against zinc evaporation, and suppresses zinc evaporation during brazing. At the same time, the zinc coated on the aluminum material starts to diffuse, forming a desired diffusion layer during the preheating time.

Here, the preheating temperature of the capacitor core is 400°C.
The reason for this is that the melting point of zinc is 419°C, and the formation of an oxide film is promoted in a short time from around this point. Further, the reason why the temperature is set to 580° C. or less is to prevent the brazing material from being melted in the preheating stage and to prevent the brazing material from being damaged in the subsequent process.

Next, the capacitor core I that has been preheated as described above is sent into the brazing furnace 3 under an inert atmosphere of nitrogen gas, and the KFA7! Each tube and fin is brazed with a non-corrosive flux made from F3 at a temperature of 580°C to 620°C for 3 to 20 minutes. Then, it is sent to the next process as a brazed capacitor core 4.

Next, the measurement results of the amount of zinc evaporated by the above brazing method will be described with reference to FIG.

Figure 2 shows the preheating time on the horizontal axis and the amount of zinc evaporation on the vertical axis. When the capacitor core is brazed in an inert atmosphere without preheating, the amount of zinc evaporated is However, when the same capacitor core was preheated at 400°C for 5 to 60 minutes and then brazed, the amount of zinc evaporated during the brazing process was as shown in Figure 2. The results are shown in curve I, confirming that the amount of zinc evaporation can be suppressed to a maximum of 20%.

In addition, the curve ■ in Figure 2 is the measurement result when the preheating temperature is set to 500°C, and the curve ■ is the measurement result when the preheating temperature is set to 550'C. As is clear from (1) and (2), it was confirmed that the amount of zinc evaporation could be suppressed to a maximum of 17% at 500°C, and to a maximum of 10% at 550°C.

Therefore, according to the above brazing method, if the capacitor core is preheated for 5 to 60 minutes before the brazing process, the amount of zinc evaporated will be 3.
The amount of zinc evaporated can be significantly reduced to 20 to 70% compared to conventional brazing methods. For this reason, compared to conventional capacitor cores, the amount of zinc deposited is reduced and the same corrosion prevention effect can be obtained, and since there is less zinc deposited inside the furnace, it is possible to reduce the amount of zinc deposited on the furnace wall. Product defects and early deterioration of the cooling pipes and furnace walls in the furnace can be prevented, and the maintenance period can be at least doubled. Furthermore, the process of drying the flux becomes unnecessary.

Furthermore, the method of the present invention is not limited to brazing in the above-mentioned inert atmosphere, but can also be applied to brazing in vacuum using a ternary alloy solder of Aβ-31-Mg.

This brazing method uses an aluminum material made of A3003 alloy and A4004 alloy brazing material, and an A10
This test was applied to a capacitor core made of an aluminum alloy material consisting of 50 alloy and Al070 alloy, and the results of measuring the amount of zinc evaporation in this case are shown in 3rd ffl.

In FIG. 3, the horizontal axis shows the preheating time, and the vertical axis shows the amount of zinc evaporated. As is clear from the figure,
If vacuum brazing is performed without preheating, the amount of zinc evaporated will be over 90% as shown by the black circle, but 4
When brazing was performed by preheating at 0.00"C for 5 to 60 minutes, the amount of zinc evaporation was as shown by curve (2) in FIG. 3, and the amount of zinc evaporation could be suppressed to about 49% at maximum.

Further, when preliminary heat treatment was carried out at 500°C for 5 to 60 minutes, the result was as shown by curve (2), and the amount of zinc evaporation at that time could be suppressed to about 44% at maximum. Furthermore, 5 to 60 at 550℃
When the preliminary heat treatment was performed for a minute, the amount of zinc evaporation was as shown by curve (2), and it was confirmed that the amount of evaporation could be suppressed to about 37% at maximum.

As is clear from the above results, the amount of evaporation of zinc during vacuum brazing can be suppressed to about 62 to 37%,
Accordingly, the amount of zinc evaporation can be reduced to 30 to 60% compared to conventional vacuum brazing.

In the method for brazing aluminum materials according to the present invention, plating or thermal spraying is suitable as a means for coating aluminum or aluminum alloy with zinc or zinc alloy, but the method is not limited thereto.

In addition, zinc is not limited to pure zinc, for example, zinc is
It may also be a zinc alloy containing 1% gold. Furthermore, the aluminum used as the base material is not limited to pure aluminum, for example, A1050. A]070. A300
3 etc. can be arbitrarily selected according to the purpose. Also, as a brazing filler metal, A4343°A4045. A4
004. There are brazing materials such as A4005, and the brazing temperature of these brazing materials is 580 to 620°C.

In addition, in the above embodiments, the explanation was made regarding the capacitor core, but the invention is not limited to this, and can also be used to suppress zinc evaporation in A-1,Q~3.0χZn, etc. used in the fin material of a radiator, for example. Of course, it can also be applied to brazing evaporators, oil coolers, etc.

(G) Effects of the Invention As described above, according to the present invention, aluminum material or aluminum alloy material coated with zinc or zinc alloy is heated at 400°C to 580°C in the atmosphere before being brazed in a furnace. ~
By adding a preheating process for 60 minutes to form a zinc oxide film and a diffusion layer on the surface of the aluminum material or aluminum alloy material, evaporation of zinc during brazing can be significantly suppressed and the product This reduces the amount of zinc deposited and provides the same anti-corrosion effect as before. In addition, it is possible to prevent product defects due to falling of zinc adhering to the furnace walls, early deterioration of the cooling piping in the furnace, early deterioration of the furnace walls, etc., and the maintenance period can be at least doubled.

[Brief explanation of drawings]

Figure 1 is a process explanatory diagram showing an example of the method for brazing aluminum materials according to the present invention, and Figure 2 is a diagram showing the relationship between preheating time and amount of zinc evaporation during inert atmosphere brazing in the present invention. Fig. 3 is a measurement explanatory diagram showing the relationship between the preheating time and the amount of zinc evaporated during vacuum brazing in the present invention, and Fig. 4 is a measurement explanatory diagram showing the relationship between the preheating time and the amount of zinc evaporated during vacuum brazing in the present invention. An explanatory diagram showing the brazing treatment process, and FIG. 5 is a graph showing the heating time. 1... Temporarily assembled capacitor core, 2... Preheating furnace, 3... Brazing furnace, 4... Brazed capacitor core. 8

Claims (3)

[Claims] (1) When brazing aluminum materials or aluminum alloy materials coated with zinc or zinc alloy in a furnace, the brazing process must be performed at 400°C to 580°C in the atmosphere for 5 to 6 hours.
A method for brazing aluminum materials, characterized by preheating treatment for 0 minutes. (2) The method for brazing aluminum according to claim 1, wherein the brazing atmosphere after the preheating treatment is inert or vacuum. (3) The aluminum brazing method according to claim 1, wherein the zinc or zinc alloy is coated on the aluminum material or aluminum alloy material by plating or thermal spraying.