Silicon Bronze MIG Brazing Basics | MillerWelds

Silicon Bronze MIG Brazing Basics

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Get answers to common questions about MIG brazing silicon bronze.
Silicon bronze filler metal creates a gold finish weld on the frame for this rocking chair project.
Silicon bronze filler metal joined a cast iron finial to a steel tube, creating a curtain rod.
Silicon bronze filler metal welds thinner gauge metal in an auto body application.

MIG brazing benefits

MIG brazing may not be a familiar process to many, but it has been around for years. Today, it is gaining popularity due to the benefits it can offer, especially with silicon bronze filler metal.

Learn about MIG brazing, silicon bronze and how to properly set up your welding power source for this process.

Questions and answers

What is MIG brazing?

Brazing processes have traditionally used an oxy-fuel acetylene torch to melt the filler metal, but in MIG brazing, a standard MIG gun is used to run brazing wire. Brazing filler metal melts at 840 degrees Fahrenheit, which is lower than the melting point of the base metals being joined. Due to the lower melting point, the filler metal provides capillary action — fluid being drawn into the weld joint — when brazed.

What is silicon bronze?

Silicon bronze filler metal mostly consists of copper, silicon, tin, iron and zinc. This composition provides some unique benefits such as the ability to weld dissimilar metals together. It also reduces distortion and provide a visually appealing finish.

What are the benefits of MIG brazing silicon bronze?

When braze welding with silicon bronze filler metal, the molten metal bonds the base materials together but does not provide fusion like mild steel filler metal. Because of this, you can use silicon bronze for welding together dissimilar materials such as cast iron to steel.

Another key benefit is the low melting point of silicon bronze, which reduces heat input into the base material. As a result, welders get less distortion and the ability to weld on heat-sensitive materials without compromising the physical properties. It is ideal for joining thinner metals together, filling gaps, and sheet metal work such as HVAC and auto body welding.

When done correctly, a silicon bronze weld will have a gold colored finish that provides contrast to the base metal. Welders often use gold colored welds for aesthetic appeal in metal art applications.

What are the disadvantages?

There are a few disadvantages of the MIG brazing process to consider. For example, silicon bronze wire is generally more expensive than mild steel wire. Also, the wire is softer than a mild steel wire, meaning it can occasionally cause bird-nesting or other feeding issues. It also has a lower tensile strength than mild steel wire.

How do I sent up my machine for MIG brazing?

Welders can MIG braze with short-circuit transfer, and the arc characteristics are similar to a mild steel filler metal arc.

When setting up your machine, several key components must be correct to achieve the best results possible.

  • Shielding gas: It is critical to use 100% argon shielding gas with silicon bronze wire.
  • Drive rolls: Because silicon bronze wire is softer than steel, U-groove drive rolls are recommended, but V-groove drive rolls will also work.
  • Process selection: When setting up this process on your MIG welder or multiprocess welder, set the machine to the C25 setting for the best results.
  • Polarity: Set polarity to DCEP.
  • Gun liner: Use a Teflon liner due to the softness of the wire, but a regular steel liner will also work.
  • Technique: When MIG brazing, use the same welding technique used for short-circuit MIG.