I found this on the King of Random youtube channel. It is very interesting and has lots of uses. This particular version uses two microwave oven Transformers on 240 VAC. This outputs about 20 to 40 volts at about 40 to 80 amps.

But, instead of using transformers and wall power, what if you used two reclaimed car batteries wired in series? And, what if you charged them with solar? This would make for a great off-the-grid metal furnace. And, with car batteries and bigger electrodes, you could have a much bigger furnace.