I tried DCNeg and low current using Silicone Bronze rod. It shows lots of promise. The parts are small so the current has to be low. I am using Lincoln 175. Instead experimenting and learning something improper I rather seek guidance.
It should be the same polarity that you would use for welding. The goal is to get most of the heat on the work, not the tungsten. I understand that the other DC polarity is rarely used for TIG work. When I switch from tig to stick, I reverse the polarity. I use electrode negative for TIG, and electrode positive for stick welding, I added stickers to my machine to remind me which polarity is for which process. I know that there are exceptions to this polarity rule, but I treat it as a rule of thumb. I use AC for aluminum, but on no other metal.
Let's see what the experts say.
Richard
Boris Mohar wrote:
I'm no expert, but it is electrode negative for both TIG and stick. If you're using reversed polarity on stick, you're not getting good penetration.
I think regular MIG is electrode positive, and electrode negative for flux core.
It might make sense to use electrode positive for brazing for the same reason you use reverse polarity on thin sheet metal. It puts most of the heat into the electrode instead of the work piece, which means you can use enough current to keep the arc stable without running the risk of overheating the work piece. With that said, I'd probably still use electrode negative most of the time.
Richard Fergus> It should be the same polarity that you would use for welding. The goal
Um...no. Stick operates in reverse to TIG. DCEN gives you more penetration on TIG, but less on stick. DCEP is for higher penetration for structural welds with 7018, and 6010. DCEN is for 6010, 6011, 6013 or 7014 on light gauge steel to prevent burn through.
Wire feed is also different. MIG, and Gas-shielded Flux-core, run DCEP, while Self-shielded Flux-core runs DCEN.
You can TIG with DCEP, and I have done quite a bit of it. It allows you to TIG weld aluminum when you only have a DC TIG source. Not as civilized as AC TIG for aluminum, but it does work.
What about my original question? What is the best polarity fro TIG brazing small parts?
Regards,
Boris Mohar
Got Knock? - see: Viatrack Printed Circuit Designs (among other things)
I stand corrected. Ernie Leimkuhler and Richard Ferguson have it right. Reverse polarity is much more common in stick welding.
I still stand by my statement that the electrode is hotter, and the work piece colder with electrode positive.
Ernie, I don't doubt you, but can you please explain to me why you would get better penetration stick welding with DCEP? Easier welding and nicer looking bead I can understand, but a deeper weld? I don't get it.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.