Can it be true? That I hold here in my mortal hands, a splat of purest crud?

Today, a semi-successful experiment. I tried to make a small arc furnace using an arc welder, a graphite crucible and some inanimate carbon gouging rods. The goal was to melt aluminium successfully enough to do some casting. The idea behind using the arc welder is that it’s accessible and doesn’t require faffing around with fire, and getting the consumables brought in (gas, for example). The whole thing ought to be less messy and quicker to set up and tear down.

The furnace consists of a solid, 4kg sized graphite crucible (remarkably inexpensive) sitting in a badly welded, but very stable steel holder steel holder:

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An arc furnace. The white stuff on the inside is alumina fumes which settled on the side.

The idea was to strike an arc with the crucible and a copper clad carbon rod (a gouging electrode). It kinda worked, but the arc was pretty unreliable and surprisingly weedy even on the highest setting on the welder. I had much better luck striking the arc between two carbon rods and moving that around as a heat source.

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The rods are very much a consumable!

That kinda worked, and I was certainly able to get some melting (as you can see in the splat). Enough to prove the principle but not enough to actually do some casting. The summary is kind of:

  • Someone stole my flux (own brand lo-salt), so I got a lot of aluminium oxide for my troubles.
  • The welder doesn’t like the 16A breaker for the outdoor power socket. Works fine on the other 16A breaker in the basement but keeps tripping out.
  • Not enough insulation, a rather large crucible, repeated cutouts and cold weather meant I couldn’t retain enough heat to make a pour.

The thing to do now it appears is to make the furnace by hollowing out an alumina firebrick. They’re very porous and so excellent insulators (one video has the person picking up his brick with bare hands with a pool of molten aluminium in the central hole).

Nonetheless, it proves the principle. The 400 and 600A (one of each) crocodile clip style rod holders hold the carbon rods well. The rods work, strike an arc and provide aluminium melting heat.

 

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