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I Forge Iron

Arc furnace as forge

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I was experimenting with making brass today in a small charcoal fire. The process was awfully hassle-some, what with sparks jumping everywhich way and having to feed the fire every half minute. So I went and looked into arc furnaces. They sounded much more convenient. (Ok, plus it was just an excuse to go build something more complicated than a pile of bricks with an air inlet.)

I slapped together some leftover kaowool, a metal can, and some glass tubing (to insulate rods from metal can), stuck some carbon rods inside, and hooked it up to the arc welder. It heats up. I expect even better once I put some itc-100 type-stuff on the walls. Then I got the idea of sticking some iron inside. A crude testing of this shows that it seems to work as a forge. But since I have never heard of this sort of thing being used as anything other than a melting furnace, I thought I would check with you guys for any possible hazards or other problems that I might be missing. So far I've worked out that I'll need to be shielded from the light while in operation, wear a welding mask, and such. Plus it's sort of hard to tell when the steel is hot; It looks dead cold at a medium orange through the welding mask. But that can be worked around. The idea of using this in my air-conditioned basement as opposed to the propane or charcoal forge in the non-cooled shed this summer sounds awfully attractive..

Any thoughts? And pardon if this has been covered before. "arc" was unacceptably short as a search term.

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  • 3 years later...

I built a carbon arc furnace as a kid for science fair. Unfortunately it would only run for a short time before kicking the circuit breaker.

I used a flower pot with holes drilled opposite sides of the pot. I used a curtain rod cut in half with a carbon rod harvested from D cell batterys in one end of each curtain rod. On the opposite end of each curtain rod was not only a wooden board (in and out arc control) but wire. One side went straight to the plug and the other electrodes wire went to s metal can lid in a wide pyrex baking dish, in the opposite side of the dish was another metal can lid connected to another wire that went to the plug as your negative. The glass dish was filled with brine and acted as a rheostat, you would move the can lids closer or farther away from each other in the brine filled dish to control the amount of current in the system.

The boards on each electrode not only held them in position but made for "insulated" in and out electrode adjustment handles.

Anyways all that being said the 1950's science book I found the design in said it was fairly safe.....that was in the 50's though and when I did it was in the 80's.....both far different times.

I wouldn't call the design safe but to me it proved it could work under the right circumstances but as a kid I didn't know enough to fix the issues ur had so I gave up on it. Your design sounds s lot safer I'll say that. My question is though don't most welders have a duty cycle? If so how would you refrain from pushing it past that point?

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So how are you venting the toxic gasses formed?  I know ozone and I'd wonder a lot about some nitrogen compounds.


That is *one* good thing about burning coal---one look and you *KNOW* you shouldn't be breathing that crud!  Unlike coke, propane, NG, arc  where the fumes may be invisible but still can be deadly!

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Back in college, I worked in a silk screening shop and we used a commercial carbon arc to cure photo emulsion on the screens. Our unit had to be vented because the smoke was nasty stuff. They are also high energy users - my preference would be an induction machine over any type of arc rig.

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  • 2 weeks later...

Gunnie -  Funny you ressurected this thread just as I've been getting back into smithing!  It's been 4 years since that experiment, wow.  And  yes, arc welders do have a duty cycle.  I never used this long enough to trip mine, so I can't really say much more than that.  If you give it a shot, don't be fooled into thinking my contraption was safe.  I doubt it was safe at all.  It mostly just seemed like a neat idea at the time.  A good rule of thumb is that if something seems neat, it's probably dangerous.

Thomas - The gases were what ended the experiment.  I realized after a few tests that there was a funny smell lingering afterwards -- oh, right ozone.  darn it!  And put the project on the backburner.

I'm now out in the country, and have a nicely ventilated shed under construction.  I might ressurect the idea someday, but for now I've finally been getting comfortable using coal, have a very cheap supply, and am better adapted to heat than I used to be, so then again, maybe I won't.  

HWooldridge -  I'd definitely prefer induction, too, but this was easier to slap together with materials I had around.  I didn't, and still don't, forsee having 3 or 4 grand around for an induction machine any time in the near future. 

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