The Aluminum Brazing Process Explained

Lynch Metals is proud to be the premier stocking distributor of aluminum brazing sheet in North America, supplying the aerospace, automotive, signage, and telecommunications industries with top-of-the-line, high-performance materials. Our vast inventory includes 1100, 1145, and 3003 aluminum fin, as well as #7, #8, #13, and #14 brazing sheet.Aluminum fin is used to efficiently transfer heat. For instance, Lynch’s 1100, 1145, and 3003 aluminum fin are typically found in air coolers, evaporators, condensers, radiators, humidifiers, and baseboard heaters. Today, aluminum fin is favored over copper, offering lighter weight, better conductivity, and superior corrosion resistance. Lynch’s precision high-speed equipment can run aluminum fin stock as light as 0.001”.

Brazing sheet, on the other hand, is often utilized in vacuum brazing jobs, mostly for aerospace applications.

How the Brazing Process Works

Put simply, brazing is the process in which two or more metal items are joined together by pouring a filler metal into the joint. The filler metal fills the gap between the close-fitting parts via capillary action. The filler is brought just above its melting temperature and is typically protected by a flux, such as borax. This flows over the base metal in a process called wetting, and is cooled to join the pieces together. Flux can be applied as a paste, liquid, or powder, and can also be applied via brazing rods. Brazing sheets can play a critical role in this process, serving as a very convenient method for pre-placing filler metal.

Variables such as temperature, vacuum level, and cycle time are strictly controlled during brazing based on the specific materials being used. There are several types of brazing available, including flux brazing and vacuum brazing — two very popular methods.

During flux brazing, flux pours into the joint, which then is dislodged by the liquid filler to remove oxides on the part, completing the braze. Manual and automatic torch brazing, induction brazing, dip brazing, and controlled atmosphere brazing are common types of flux brazing.

Vacuum aluminum brazing, on the other hand, occurs in a vacuum furnace, or can be performed using inert gas atmospheres. With this method, flux is not needed to create joints due to the vacuum’s clean environment. Magnesium is used as an additive — also known as a “getter” — during the vacuum aluminum brazing process.

The Difference Between Welding and Brazing

During welding, two metals are melted together to join them. During brazing, on the other hand, two or more materials are merged via the use of a third material. The cleanliness of parts is much more important for brazing, and because less heat is used during the process, contaminants are less likely to burn up. Brazing also allows for tighter control over tolerances.

Producing a reliably clean joint, brazing allows non-similar metals to be easily joined together. This technique is also more cost-effective, especially for complex and multipart pieces. Brazing is well-suited for mass production and is simple to automate, allowing for savings on costs and labor.

Learn More About Aluminum Brazing

Ready to get started on your aluminum brazing project, or looking to learn more about the process and how it can benefit your unique application? Contact the experts at Lynch Metals today.


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