Dayang Nissei develops aluminum brazing technology without flux

Daiyang Nissan has partnered with Mitsubishi Aluminum to develop aluminum (Al) brazing technology using fluxes containing magnesium (Mg) under argon (Ar) atmosphere without flux. The technology will be applied to coolers in HEV (Hybrid Electric Vehicles) and EV (Pure Electric Vehicle) control units, as well as automotive and domestic air-conditioning heat exchangers using magnesium-containing high-strength components.

The aluminum brazing method is often used in the production of heat exchangers such as automotive heat exchangers that have a large number of welding spots. Currently, there are two kinds of mainstream aluminum brazing methods, namely, brazing using non-corrosive fluoride flux under a nitrogen atmosphere and vacuum brazing using a vacuum protective atmosphere.

Brazing methods using non-corrosive fluxes are mostly used in automotive heat exchangers. However, the fluorine (F) in the flux reacts with the magnesium in the aluminum alloy and causes poor brazing. Therefore, the brazing method has a problem that it is not suitable for aluminum alloy containing magnesium. Therefore, it cannot be used for high-strength aluminum alloys.

In the vacuum brazing method, the magnesium contained in the solder evaporates when it melts, and the oxide film on the aluminum surface can be reduced and brazed by removing oxygen (O2) and moisture remaining in the furnace. However, in a high-vacuum protective atmosphere, zinc (Zn) contained in the aluminum alloy also evaporates, and therefore there is a problem that the corrosion resistance is lowered.

In order to solve the problems of these two types of brazing methods, Dayang Nitrate started to study brazing techniques that use no flux at atmospheric pressure. As a result, new brazing techniques using magnesium-containing solder without flux in an argon atmosphere have been developed. This new technology eliminates the need for fluxing and can be used in magnesium-containing alloys, as well as avoiding quality degradation due to zinc evaporation.

In addition, since nitrogen (N2) and oxygen in the protective atmosphere have the effect of hindering solder wettability, techniques for controlling the concentration of N2 and O2 in the protective atmosphere of argon have been developed. As a result, the use of argon can be reduced to approximately 40%. (Reporter: Shinoda Yoshihiko)