TIG Brazing With Silicon Bronze

Why a lower melting point makes for a cleaner joint

• Less heat, less warping: Lower melting temps mean less heat, which equals less warping when compared to TIG with, say, an ER70 rod. The silicon bronze rod’s lower melting point makes it ideal for joining together thin sheet metal, galvanized steel, and nuts and bolts, too.
• Better finish: After blazing, you can still sand and paint it just like the surrounding metal.
• Fewer issues with galvanized steel: You won’t get the “popping” and tungsten blowouts that are normally associated with TIG welding galvanized steel because the silicon bronze flows at a temperature lower than the zinc-heavy coating. Zinc is relatively nasty stuff that causes a mess.

Silicon bronze brazed joint durability

Silicon bronze offers excellent wear properties for dissimilar metals. For example, I rebuilt my dad’s snowblower using a “cold” braze — just warm enough for the silicon bronze to bond. After filing the teeth to fit, those gears have worked perfectly for five or six seasons.

Joining dissimilar metals

One of the biggest advantages of TIG brazing with silicon bronze is flexibility. You can join metals that normally don’t bond well, opening creative and practical possibilities.

Here are some of the materials that you can braze together with silicon bronze:

• Mild steel
• Stainless steel
• Galvanized steel
• Copper
• Brass
• Bronze
• Cast iron

Tips for welders new to TIG brazing

Although TIG brazing and TIG welding share similarities, the filler reacts differently to the base metal. Here’s what to keep in mind:

Heat control vs. welding

The melting window is smaller. Too cold, and the filler balls up; too hot, and you risk “hot cracking” by melting into the base metal excessively.

Base metal melting — how much is okay?

A little melting is fine, but too much can fracture the joint down the middle. Overall, TIG brazing silicon bronze feels a lot like TIG welding steel in terms of machine settings and techniques. The filler is pretty much the only variable that changes from a process standpoint.

Using DC vs. AC polarity

• DC negative: Common choice for TIG brazing with silicon bronze, like TIG welding steel.
• AC option: Alternating current’s cleaning process helps when brazing some materials.

Pro tip: Experiment with both settings to see what works best. Machines like the Multimatic® 220 AC/DC multiprocess welder offer flexibility for both AC and DC TIG.

Key takeaways

If you can TIG weld and want to try TIG brazing, just grab some silicon bronze and go to town. You'll notice some slight differences, but overall, it's a pretty simple process. Just remember:

• Control the heat at a lower temperature. You don’t need to melt the base metals, and you don’t want to overheat the silicon bronze rod.
• A brazed joint is not as strong as a weld. Because the base metals are not fused and the filler material melts at a lower temperature, brazed joints are not to be used where structural integrity is needed.