Aluminum brazing entails the joining of metals with melted aluminum. It produces a much cleaner joint than other joining methods such as welding and eliminates the need for post-processing.
Aluminum brazing is ideal for large flat surface materials, as it uses pressure to reinforce joints. Since it can be used to join parts made of different materials, it is also a cost-effective option for composite or assembled parts.
Because brazing is performed in large furnaces that can accommodate bulk materials, it is particularly well-suited to mass production. If necessary, another brazing material can also be used in the process.
There are two types of aluminum brazing: aluminum dip brazing and aluminum vacuum brazing. Each process offers a distinct set of advantages.
Aluminum Dip Brazing
Aluminum dip brazing involves placing brazing sheets in molten salt to break down metal oxides. The filler metal is initially positioned outside of the joint and heated to molten temperature before it enters it. As it travels through the joint, the filler metal expels the flux from it.
Unlike aluminum vacuum brazing, aluminum dip brazing does not apply pressure to a joint. As a result, it can be used on parts without large flat surfaces or similarly sensitive materials.
Alloys subjected to aluminum dip brazing offer greater strength and an increased resistance to corrosion. Since they conduct heat effectively, they are also particularly useful for heat transfer applications.
Aluminum Vacuum Brazing
Aluminum vacuum brazing uses a clean vacuum environment without a flux. Because it applies pressure to the parts to be joined, it can only be used for flat, horizontal surfaces. In contrast, aluminum dip brazing is designed for parts that are not flat.
During aluminum vacuum brazing, pressure is applied to a metal part to break down its oxide layer. The filler metal is then diffused into the base metal. Because the filler metal is inserted into the joint before brazing begins, the process results in a cleaner and more precise joint.
Aluminum vacuum brazing can be performed on metals with objects and cross-sections with different dimensions, making it a particularly versatile solution. Because it offers greater precision than dip brazing, it’s best suited to any application that requires strict consistency.
Lynch’s Brazing Solutions
Aluminum dip brazing and aluminum vacuum brazing are far better options than other joining methods, providing manufacturers with more durable and effective products. As with any manufacturing technique, however, any prospective user should thoroughly consider their needs to ensure that they invest in the best strategy for their applications.
If you need appropriate equipment for your brazing processes, the experts at Lynch Metal can help. Since 1991, we’ve been a trusted leader in the distribution of flux brazing alloys used in aluminum dip brazing and aluminum brazing fins and sheets used in aluminum vacuum brazing.
Our extensive inventory, specialized processing equipment, and years of experience make us the go-to resource for your aluminum brazing needs. From aerospace to telecommunications, we’re able to provide manufacturers in every major industry with reliable and efficient solutions to their brazing challenges.
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”.
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.
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.