Written by Miles Budimir
Senior Editor, WTWH Media
Brazing and welding are metal joining techniques that use heat as the main mechanism to bind together two metals. Both processes also use some kind of flux to inhibit oxidation of the metals. However, this is where the similarities end.
The differences between welding and brazing relate to two key points:
1. The temperatures used.
2. How the temperatures impact the state of the metals.
For instance, welding uses high temperatures, typically 1,000˚ C or much higher. One requirement of welding is that the base metals must be similar. So, for instance, steel is unable to weld to copper.
Welding also differs from brazing in that it melts the base metals that are then fused with the aid of a filler metal. The metals cool and solidify, forming a strong bond. The filler metal, sometimes called a “welding rod,” functions in a similar way to solder in brazing. Brazing temperatures are generally much lower than those used in welding.
This explains another difference. During brazing, the base metals are not melted — only the filler metal (or solder) melts and spreads out over the base metals, joining them together. The filler metal’s melting point must also be below that of the metals to be joined.
In contrast to welding, brazing can be used to join dissimilar metals together, such as copper and aluminum and nickel. Brazing is defined by the American Welding Society as the process where the filler metal has a liquidus above 450˚ C. Liquidus means the temperature above which the metal melts and below which it begins to solidify.
The most common brazing method is torch brazing which uses a gas flame. Other common techniques include furnace brazing, which is conducive to industrial level mass production applications. As for strength, a properly welded joint will typically be stronger than a brazed joint. However, a proper brazed joint will still be stronger than the individual pieces joined together.