Carbon Arc Brazing

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I was wondering if anyone has tried this. If so, did you use a dual electrode torch or did you just use a stinger and run it straight? What braze did you use? Any tips?
Reply:I have brazed with my homemade dual electrode torchusing standard flux coated brazing rods There's a bit of a trick todoing it without boiling the filler or having it spread out allover the part(heat control).You need to experiment and practice.It will never be as good as an o/a set.But for the guy with nothingbut a stick welder it can be a useful addition.Miller a/c-d/c Thunderbolt XLMillermatic 180 Purox O/ASmith Littletorch O/AHobart Champion Elite
Reply:BelowLincoln SA200's... at least 15 - 20. They come and go. Growing partial to the "Short Hoods" in my old age. Last count on Short Hoods was 13 in possession.
Reply:I use this with galvanized sheet metal quite a bit. I just put the carbon in the stinger and roll. I sharpen the carbon like a pencil, with a fairly shallow angle, then dull the end a bit. I keep the arc length just smaller than my rod diameter, then strike on my filler, always keep my arc on the brass as I move. Move the arc to your puddle if you want it to spread, and to the filler rod (forward) if you don't. If you find you are you are moving to fast, turn it down.This is one process transformers seem to outshine most inverters with.Last edited by Davidbrown; 09-30-2012 at 11:40 AM.Constant Current Weldor.
Reply:I've never had much luck with it (dual electrode). The issue is directing / controlling the heat. For brazing I go with an O/A set up every time.Lincoln SA200's... at least 15 - 20. They come and go. Growing partial to the "Short Hoods" in my old age. Last count on Short Hoods was 13 in possession.
Reply:Originally Posted by DavidbrownI use this with galvanized sheet metal quite a bit. I just put the carbon in the stinger and roll. I sharpen the carbon like a pencil, with a fairly shallow angle, then dull the end a bit. I keep the arc length just smaller than my rod diameter, then strike on my filler, always keep my arc on the brass as I move. Move the arc to your puddle if you want it to spread, and to the filler rod (forward) if you don't. If you find you are you are moving to fast, turn it down.This is one process transformers seem to outshine most inverters with.
Reply:I did it years ago with a twin carbon arc torch on an AC buzzbox. The instructions said to use silicon bronze rod without flux, which works pretty well on clean metal.JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:I had the same experience as Jpump5.Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:Originally Posted by slotardI know that for TIG brazing you have to use bronze rather than brass so you don't boil the zinc. Have you ever tried that? What size electrode do you use? What flux?Too bad that transformers are better here. I've got a little HF inverter, 90 amp unit that I paid $60 for. Mostly I use my MIG but I figured it might be nice to be able to braze.
Reply:Come to think of it, should I try some standard copper wire? That way there's no Zinc in it to vaporize...
Reply:I have  never had the alloy separate, or vaporize significantly . You don't  really get It that hot. I never get It hot enough to vaporize the zinc galvanize coating, let alone the zinc in the alloy. Evedure (spelling?) rod is what the old man who taught me called it, and he even ordered It is such, but I can find out the exact alloy for you. There is no "arc" really, you keep your carbon just touching the puddle/rod. It is the energy passing through the metal that melts it, not a gap of resistance. You will need a 5-9 shade lens.Constant Current Weldor.
Reply:Oh, interesting. I assumed the process would be similar to TIG brazing. A friend of mine tried doing that with standard brass brazing rod and had issues with the zinc boiling out.
Reply:Originally Posted by DavidbrownI have  never had the alloy separate, or vaporize significantly . You don't  really get It that hot. I never get It hot enough to vaporize the zinc galvanize coating, let alone the zinc in the alloy. Evedure (spelling?) rod is what the old man who taught me called it, and he even ordered It is such, but I can find out the exact alloy for you. There is no "arc" really, you keep your carbon just touching the puddle/rod. It is the energy passing through the metal that melts it, not a gap of resistance. You will need a 5-9 shade lens.
Reply:I have one of those carbon-rod soldering machines, and the voltage is very low, about 4 or 5V. If you try that with a regular stick welder, it's pretty close to a dead short and the current will be much higher than what is indicated. This may cause transformer-type welders to overheat, and some newer welders may shut off thinking you have a "stuck" rod.BTW, Everdur is a trade name for silicon bronze.JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:Well, I tried it and can get it to work reasonably. I'm using a 1/8" carbon and 1/16" silicon bronze. Running around 30A, this is just laying a bead across some 12g sheet metal that I have sitting around.The problem is that my HF autodark mask keeps cutting out on me, so I need to find a standard mask instead. No way I want to flash myself just for fun.
Reply:that's what I've gotten so far. never brazed before today so it takes some getting used to. I don't feel that bad about the lap joint, obviously the T is pretty horrid - not really asking about it.edit: I tried something suggested on another board: turn up the heat a fair bit and move WAY faster. if I lay the filler rod down and do a quick pass over it's full length, it actually works surprisingly well. I'll get some pictures up sometime tomorrow. This is using ~50A, so I probably need to try somewhere in between and just move fast.Last edited by slotard; 10-02-2012 at 01:41 AM.
Reply:doing a whole lot better today. this is largely applying the heat to the braze itself.
Reply:TIG brazing is a royal PITA compared to using O/A in my experience.With O/A, I use TIG bronze filler and dip it, when hot, in borax for flux.
Reply:You really are coming along quite well!Constant Current Weldor.
Reply:slotardDecades ago on a moneyed project the shop had a dual-electrode torch.  It was branded Toban and held the electrodes in a V.  The armatures weresteel, the handle like bakelite, and it had a thumb actuator top/forward in thehandle.  The thumb controlled the carbon distance [size of arc envelope] and fed the electrodes to one-another as they burnt away.The senior welders on the job said it was for general heating, but specificallyfor soldering/brazing heavy and large sheet metal.I used it several times, but only for open joints.  The arc size can be controlled, but the bottom-only arc path limits it use to flat-work.Toban was an important name in the industrial history of carbon arc application.Opus
Reply:I thought of something, might be stupid but I'd like to know what other people think. Cheap TIG torch, 1/8" collet, but the carbon in there. Run CO2 (due to cost). Any thoughts on this? Would it be worth looking for a cheap TIG torch and modifying it to fit, or will CO2 not work any better than air?If it's worth looking... anyone have a cheap TIG torch they'd be willing to part with?
Reply:slotard  -  You answered your question in the first half of the first sentence  -  Opus
Reply:So CO2 won't be any better than air? Too bad, I was figuring it might be a cheap way to do it.
Reply:keeping your carbon out of the puddle will eliminate the black in the final product. After the initial arc strike, there should be enough arc force to keep the rod pushed back a little. There is only a millimeter or two of acceptable "arc gap"Constant Current Weldor.