Technology for Joining Dissimilar Metals by Brazing


Technology for Joining Dissimilar Metals by Brazing

Atago Manufacturing, with support from the government, has developed a technique for the joining of dissimilar metals through electric furnace brazing. This technology enables aluminum to be used for parts of a heat exchanger that can tolerate aluminum, while only the parts that come in contact with water are made of copper. This reduces cost significantly, and also reduces weight.

The heat exchangers in hot water heaters for both home and industrial use are typically made of copper. This is because the exchangers typically are used for drinking water, and very few materials other than copper are used for that. When water is used with aluminum, the aluminum corrodes. It’s also not yet clear what effect aluminum has on the human body.

There are NOCOLOK products specially for joining aluminum, but when joining copper and aluminum, as with the Atago Manufacturing technology, the NOCOLOK flux must be modified. Specific processing conditions, such as temperature, must be determined. Atago Manufacturing’s proprietary brazing materials were developed in partnership with downstream companies to achieve joining of dissimilar metals.

The aluminum and copper temperature conditions must be maintained for a fixed length of time. If it’s any shorter, the brazing will fail. If it is held for too long, the brazing materials, the aluminum and copper, will melt, or form pinholes, which can be a source of leaks. In either case, it has a serious effect on the heat exchanger quality. We had great difficulty achieving stable conditions for brazing that can provide quality control, even in volume production.

This technology makes it possible to optimize the part configuration of radiators and heat exchangers, so they don’t use more copper than is necessary. This technique can be used for heat exchanger fins and refrigerant circuits in freezers or heat pumps. Atago Manufacturing is also looking at applications such as semiconductor manufacturing equipment, high performance computers, and power supply equipment.

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