Brazing furnace and brazing method for aluminum material

Abstract

A brazing furnace (1) has a preheating chamber (2) and a brazing chamber (3). The preheating chamber (2) has the following: a vacuum pump (21) for reducing the pressure inside the chamber in a state in which the chamber houses a material to be treated (100); a preheating device (22) for preheating the material to be treated (100) under a reduced-pressure atmosphere; and a pressure-restoring gas introducing device (23) that introduces an inert gas for restoring the pressure inside the chamber after preheating. The brazing chamber (3) has a gas substitution device (31) for introducing the inert gas into the chamber and a main heating device (32) that heats the material to be treated (100) to a brazing temperature, and as a result of the foregoing, the brazing joining quality can be easily stabilized with regard to brazing in which the flux application amount is reduced or in which no flux is used.

Description

technical field [0001] The present invention relates to a brazing furnace for brazing aluminum materials and a brazing method for aluminum materials. Background technique [0002] As a brazing method for aluminum materials, the CAB (Controlled Atmosphere Brazing (Controlled Atmosphere Brazing) method of applying flux to the material to be processed and heating the material to be processed under an inert gas atmosphere such as nitrogen to perform brazing is often used. The fluoride-based flux used in the CAB method has a problem that its function as a flux decreases when it is oxidized by heating during brazing. In order to avoid this problem, in the CAB method, usually, a sufficient amount of flux is applied, and the oxygen concentration in the atmosphere is controlled to be 100 ppm or less, more preferably 20 ppm or less, for brazing. [0003] Since the fluoride-based flux is non-corrosive to aluminum, it is not necessary to wash the aluminum material after brazing to remo...

AI Technical Summary

Problems solved by technology

The fluoride-based flux used in the CAB method has the problem that its function as a flux decreases when it is oxidized by heating during brazing

For example, in aluminum heat exchangers represented by automotive heat exchangers, problems such as deterioration of surface treatment properties due to flux residues may occur during manufacture.

In addition, in the use of aluminum heat exchangers, the following problems may occur: clogging of the refrigerant passage by flux, etc., or adverse effects of flux, etc. on electronic components that are in contact with the heat exchanger, etc.

However, as of today, there are basically no examples of practical use of the flux-free soldering method under an inert gas atmosphere.

As the main reasons that hinder the practical use of the fluxless soldering method, the following reasons can be cited: the reason why the bonding ability is inferior compared with the soldering method using flux, and the brazing property is easily affected by the working environment and it is difficult to use it. Reasons for the stable quality of brazing joints

In particular, the latter problem may cause serious joint defects due to the storage environment and / or usage conditions of tools, materials to be processed, and solder, and thus becomes a major factor that hinders the practical use of the fluxless soldering method.

[0016] As described above, in the prior art, there was a problem that it was difficult to stabilize the quality of the soldered joint in soldering with a reduced coating amount of flux or soldering without using flux.

Furthermore, it is considered that moisture, etc. brought into the brazing heating zone evaporates or thermally decomposes due to heating, thereby deteriorating the brazing property.

The above-mentioned (1) to (3) presumptions always have multiple effects on brazability due to compound effects, so it is difficult to find out the cause of the deterioration of brazability, and it also hinders the discovery of a method for improving brazability for a longer period of time. Solutions

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