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Induction brazing is a process for joining two metal pieces using a filler material in a molten state achieved through induction heating. Such heating is accomplished by placing the work inside an induction coil and running electrical current through the coil. This gives rise to electrical currents, known as eddy currents, in the materials being joined. Heat is generated due to the electrical resistance to the eddy currents of the materials being joined. Such heat is used to melt the filler material for use in joining the two metal pieces, but these pieces remain in a solid state throughout the process.
To begin an induction brazing operation, the first step usually is to treat the parts being joined with a material known as flux. Filler material is then positioned on the work, generally with the aid of some kind of form to keep it in place. Alternatively, the brazing material may be applied to the work once the parts have been brought up to the necessary temperature.
The work is placed inside an induction coil, through which a high frequency electrical current is run. As currents are induced in the surfaces of the pieces being joined, their inherent electrical resistances oppose those currents, and the pieces heat up. The filler material melts under this heat and forms a bond between the two pieces as the assembly cools.
While the filler material melts, the pieces being joined remain in a solid state. This means that the melting temperature of the filler material must be below those of the materials being joined. Silver and silver alloys, as well as copper, are frequently used as filler materials for this reason.
One of the main benefits of induction brazing is that the heating is rapid, localized, and precisely controlled. This leads to a very reproducible process suitable for high rate production. Induction brazing is also an environmentally friendly practice that consumes less energy consumption than other joining methods, and it produces no combustion byproducts since no flame is involved. Highly localized heating in induction brazing minimizes distortion or other physical changes to the parts being joined.
Similar metals are most easily joined with induction brazing. Dissimilar metals can be joined, but this requires much more consideration. The different resistances to current of different materials mean the pieces will heat up at different rates and to different temperatures. They may also have different rates of thermal expansion, which further complicates the operation.
Induction brazing operations may take place in a variety of environments. Pieces may be joined while submerged in a liquid, in air or another gaseous atmosphere, or even in a vacuum. Many types of brazing tasks can be accomplished with induction brazing. Applications range widely and include such examples as production of dental tools and orthodontic components as well as fabrication of fuel pipes and brake parts in automotive assembly.
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