Welding Tips and Tricks

Very new to all this (welding and forums), so bear with me. I've read posts where guys talk about tig brazing with silicon bronze filler. Went to my LWS and bought a 1 pound tube of, what I now see is "low fuming bronze" filler. Can't find anything on tube that says silicon. Is there a difference? If so, what are they? Now, since this is my first post, and I don't want everyone to think I'm this stupid, allow me to explain. I actually did do some OA welding and brazing, and was pretty good at it. Which is why my son told me I would pick up tig welding pretty fast (we shall see about that). But that was 45 years ago, and back in the "old days", you would just ask for brazing rod. Was silicon even around then? Anyway, all answers greatly appreciated. Merry Christmas, JR49

Low fuming bronze (RBCuZn-C) needs flux. Silicon Bronze (ERCuSi-A) does not. Sounds like you bought rods best suited to OA welding

Welcome to the forum! Seems like you should be able to exchange the bronze for silicon-bronze easily enough. What project do you have in mind for the sil-bronze brazing?

Welcome, my path was similar to yours, I never dreamed 40 years ago that tig welders would be cheap enough for me to own one. You might think about starting out tig welding by running a bead on steel without any filler, just to get the hang of controlling the puddle. Then get a filler like ER70S-2 and run a bead. I think adding the complexity of a brazing rod before you really know how to use the tig torch will make things more difficult. Once you get comfortable welding it will be easier to control the heat properly and avoid melting the base metal for brazing.
To answer your question, the rod you bought does have some silicon in it, but it's probably only a few tenths percent. When people talk about silicon bronze filler, the silicon is a much higher percentage alloy, like 3-5%, and it has very different properties.

Your low fuming bronze has zinc in it which will gas out in tig process causing porosity.


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cj737 wrote:Low fuming bronze (RBCuZn-C) needs flux. Silicon Bronze (ERCuSi-A) does not. Sounds like you bought rods best suited to OA welding

So why does one need flux, and the other doesn't?? Is it because of the different properties of each, or is it just because the silicon bronze is used with tig, so has Argon shielding it, and the low fuming bronze is used with OA torch brazing so needs the flux to shield it? If the latter is true, then I would think you could use silicon bronze with flux for torch brazing, and use low fuming bronze for tig without flux as it would be shielded with argon. I'm not trying to be difficult, just trying to understand what I'm missing about this. Thanks, JR49

The composition of the actual filler rod differs between the two, so yes, each requires their own type of "shielding" (flux in the case of Low Fuming, Argon for SilBr).

OA welding rods are not always suitable for use with TIG welding due to the dependency on shielding gas.

Blockade from Harris is a high silicon brazing rod that I have used with oxy acetylene without flux, and I’ve used it with tig without flux. However I have used the white paste flux that’s used for 45%silver braze rod along with the Blockade when there was lots of corrosion.

cj737 wrote:The composition of the actual filler rod differs between the two, so yes, each requires their own type of "shielding" (flux in the case of Low Fuming, Argon for SilBr).

OA welding rods are not always suitable for use with TIG welding due to the dependency on shielding gas.

OK, so now I think I've got it. I should have been more specific and asked for TIG brazing rod. I'll still keep the low fuming rod cause I still have my OA setup with tanks and all. Now just one more question, and I'll have the "supplies" figured out. What about filler rod for mild steel or aluminum?? Is there a difference in rod for tig and OA welding? I suppose I could ask this at the LWS, but frankly, I trust you guys a lot more than the kids at the LWS. Thanks again, JR49

Mild steel TIG rod is normally ER70S-2. TIG welds any carbon steel. Ally is usually 4043, 4943, or 5356. Brazing rods will differ (OA-based). You can “TIG Braze” with SilBr and AluBr but for true TIG welding, use the above listed.