Can I use a TIG welder to melt metal in small crucibles?

First of all, I don't have a clue...

Secondly, would it be possible or better to use the stick setting and 2 carbons to melt the metal?

Possibly. The nice aspect of tig is flow of argon, protecting the metal being melted. I am fully open minded here.

Do-it-yourself electric furnace?

Hmm.

This would almost be worth it's own setup. I have the stick welder, now how much would I need for an argon regulator and bottle plus some spare tubing?

How much carbon contamination could one expect, I wonder?

I am not sure I fully understand your question. For myself, since I have argon. electrodes and whatnot, I can always make a separate electric melting setup using tungsten electrodes and argon, and my welder.

One thing that might be a limiting item is the duty cycle on your welder. You might wnat to consider carbon arc instead of using tungsten, that's full-size electric furnace practice.

Stan

My welder has a 100% duty cycle and can weld at its highest setting

Well, sure. if that's better, I can certainly do that.

Yep. I figure, I have plenty of stuff to experiment with. Flowerpots,

I have other mechanical things on my todo list, on top of which is making a DC -> AC inverter for the welder. But maybe in winter I may have a tiny bit of time.

It sounds like it could work. One possible problem I can foresee is this: The arc will generate heat at the top of the metal, and melting down into the crucible will be sort of equivalent to "penetration." There is a likelihood that before you get all the metal heated up and melted, you will overheat the electrode and damage it.

Just curious and throwing gas on the fire here....due to the localized heating aspect of the Tig arc, would there be a problem with uneven thermal expansion of the crucible that could lead to cracking? A standard oven/furnace heats the crucible fairly uniformly but a tig melt would have far from uniform heat distribution.

Koz (who is interested in giving it a try...great idea for small melts)

That's a great question. I do not know what the answer may be.

Keep the tip moving? I wonder how the big boys do it.

I think you may be slightly confused. A stick welder has no facilities for putting the argon in the same place as the electrode. The best you could do would be to spray out the argon somewhere near the electrode. Does anyone know if argon is a heavier than air gas? I'm guessing it is, but it may not be much heavier, and thus difficult to completely cover a crucible.

Absolutely. Later in the thread you say you have 100% duty cycle, and later still you mention 200 amperes. At a typical arc voltage of say 30V, that's a good 6kW burning away the argon. (Which BTW is slightly heavier than air; argon heated to 5000°F however isn't! ;-)

Figure 1kW per pound of steel in a reasonable furnace. You'll need a layer of high-temp kaowool or fiberfrax or whatever to insulate it good, then a hard refractory hearth to melt the steel in; a small crucible wouldn't hurt, but mind if it comes with a protective glaze that'll eat the hell out of the kaowool! The arc obviously has to be enclosed to save heat (your greatest loss at lightbulb temperatures here is radiation, and there's about 6kW of it...), so you'll need another hardened hemisphere enclosing the deal with no gaps for light (heat) to get through.

Two carbon gouging rods will certainly work well here (at 200A, you'll probably want 3/8 to 1/2" dia. rods). You can draw one or two arcs off the metal to each electrode, or use an indirect arc above the melt. Figure a half hour melt time and remember to adjust the electrodes, as they will vaporize! Get good clamps, too- nothing worse than melting the electrodes off the wires!

Speaking of electrodes, they'll give a reducing atmosphere of CO and carbon vapor in nitrogen, so argon isn't really required.

Tim

That's a;; about right.

So, the idea is to just use the arc as a radiating source of heat, right?

I see. Very interesting. I will look around for suitable materials, sometime later. I want to finish an interesting project that I started.

Very nice. CO, though, is not a fun gas.

Nah..not really. It burns off suprisingly well once it gets outside.

I've seen a lot of it, for example when adding a load of charcoal to my furnace (when I used the charcoal fired furnace), the flames from below would choke out on the cold fuel above and give off lots of CO, which burned above in wide, thinly blue, whispy flame. Wish I had a picture of it!

Tim

-- Deep Fryer: a very philosophical monk. Website:

Well jewelers heat with a gas torch all of the time, I don't think that is a whole lot less concentrated is it? jk

Your crucible may need to be graphite to ground your metal for the tig arc to work. Charlie