Thursday, July 21, 2022

Can I Use Bronze Filler to Weld Steel?


closeup of a gloved hand welding metal

When it comes to welding steel, bronze is generally not used as a filler in the traditional sense and instead the bronze is used for brazing the two pieces of steel together. By using this process, you can achieve certain results not possible with traditional welding.

Brazing steel with a bronze filler also has several distinct advantages over actually welding steel where the parent materials are melted and bonded together along with the filler material.

In brazing, a bronze or silicon bronze rod is used to join the steel pieces, similar to soldering by using capillary action. This process uses lower heat than a standard weld since the base material is not melted. For some applications this makes brazing the only option as it reduces the stress on the base materials.

Other advantages of using bronze when brazing steel is that you can join dissimilar steels together using this process, which can offer more fabrication freedom.

The most common filler rod used for this process is silicon bronze. This type of bronze is mostly copper as per usual, but there is a small amount of silicon added, generally in the range of 2%-6%. Due to the slower melting temperature of silicone bronze, it makes it a great choice for thin sheet metal and other relatively delicate applications.

Silicon bronze filler can be used to braze using an O/A torch, TIG, and even MIG welders. Although the most common use is with a TIG setup due to the control and consistency it can provide.

When brazing steel with silicon bronze filler rods you need to be especially careful about the heat used. Remember, this isn't welding so the base material should not melt, but you need it hot enough so the bronze filler flows properly. This situation creates a relatively small temperature window to achieve optimum results.

If you run a little too hot and there is very minimal melting of the base metal, that’s OK, but you do risk cracking of the joint and bronze filler if there is too much melting. If you run it too cool, you will have issues with the bronze flowing properly and it will not form a smooth bead.

Once you get the temperature correct for the size and thickness of the steel you are joining, the silicon bronze filler becomes extremely easy and fast to work with. It also creates an aesthetically pleasing bead which can be sanded and finished if needed, just like the base metals being joined.

For certain custom automotive or motorcycle applications, the gold-tinted bead of silicon bronze brazing can be used to add flair to an otherwise standard weld between body panels or other areas, adding a custom look.

With a little bit of experience and practice, using bronze filler to join steel through brazing really opens up options when it comes to metal fabrication. This is especially true when you are joining dissimilar metals or the pieces to be joined have specific restrictions on heat or stress.

So if your next fabrication project requires a strong bond with minimal heat, try brazing using bronze filler. When used for the right application, it can offer very unique benefits over most other forms of welding.