Arc Furnace

[aggie_67]

Anyone have any experience, links, etc to using a AC/DC welder for an arc furnace; two carbon electrodes inside a crucible???

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[ignatz]

I found this link awhile back...

Is that what you had in mind?

[damae]

Really, the electric arc furnace seems to be very appealing:

1. Cheap to build (old welder + carbon electrodes + crucible)
2. Melts steel
3. Melts just about anything

In particular, it seems to solve a gap we hobbyists have -- we can melt aluminum and brass, but nothing much hotter. A lot of us, myself included, would love to melt steel and iron to make simple castings. It's a perfect complimient to the CNC hobby.

For instance, cut a foam pattern on the CNC router, slip coat with drywall compound, pour yourself a cast iron widget and finish machine on your CNC. There, we've come full circle with the hobby.

In any case, casting steel and iron sounds like fun. Heavy castings have a satisfying feel and may serve structural applications that our typical aluminum castings just won't.

That brings me to a question. What is the drawback to melting steel or iron this way? Do the carbon electrodes leave too much carbon in the steel soup? Do castings from this process have questionalble strength? Does it require argon or some other inert gas?

I already figured that the UV radiation would be bad... so that needs to be contained in the crucible. Are there other drawbacks? Does it not scale well for small home foundries?

So, I invite any answers or experience you folks can offer. Even more questions. Give a shout out if you're interested in a DIY arc furnace.

Wouldn't it be great to have the equivalent of JRGO plans for an arc furnace?

[ignatz]

This is the best DIY arc furnace information that I've found online: Arc Furnace Experimenter

Also, there is the old/new Modern Mechanix page.

[HelicalCut]

Did it when I was a kid only a small 4KW input furnace, power is what you need and lots of it, at a guess 10Kw for a few Kg melt, If you can get one of the large flux cored or sub arc wire feeders lincoln ln7 comes to mind and a roll of scrap fence wire, getting a crucible full of iron is doable, preheat with gas then start the wire feed, need to water cool the contact tip and seal the furnace, argon or CO2 blanket would be ideal (careful the CO2 will become CO +O2). As for a power source any heavy duty MIG, I have a DC600 which would work fine 100% duty @ 600A

Light duty home welder, forget it, most have only 20% duty or so at 140A, AC welders need considerable power factor correction to get the full KW out of your supply Industrial duty machines are usually rated at 60% duty so a 300 or 400 amp machine will be fine for most use. US users are lucky in this respect in that 240V high power welders are common as are 240V supplies, in Australia they are usually 415V requiring 2 or 3 phase power.

In short a MiG power source will work fine as a consumable electrode arc furnace power source and a electrode power source will work fine as a carbon electrode power source. Visit the local scrap yard or clearance auction for a power source. Call a carbon supplier for graphite electrodes. Water cool the electrode clamps, they get very hot otherwise

[itanc]

i have had pleasing success with very little effort on this front. I too have progressed through aluminium to brass and copper and also have longed to break the iron ceiling. i have built four traditional furnaces of various designs but all in the fuel, air, refractory and crucible type and have tried charcoal, coke, propane, paraffin and veg oil, and various blowers. i have once seen the first layers of a mild steel charge run off but never got iron or steel to properly melt.

and then there was the diy dc electric arc furnace.

a 240V dc arc welder at 175A (32A supply), 2 6mm gouging rods (@25p), a catering size bean tin full of playground sand and a small clay graphite crucible pushed into the sand such that the top of the crucible sits just above the top of the sand.

the carbon rods are held in earth clamps and a mild steel charge (approx 500g) was placed in the crucible. the arc was established by striking the rods and then manipulated towards the pieces of scrap. the entire charge was melted in a couple of minutes. once a pool is established one rod can be pushed to the bottom of the pool and the other is hovered above the pool surface at which point it seemed that the heat transfer was more effective. further pieces of scrap were added until the crucible looked like it had enough to pour. during this process i had to stop a couple of times to let the gloves cool down and change the rods. i placed a brick on top to keep the heat in. immediately prior to the pour the pool was extremely fluid and a lovely orange.

the resulting metal when cooled grinds off fine but i cant get a drill through it and i have broken a few trying so dont want to risk a cobalt one.



i then tried the same with a broken up cast iron sewing machine as the charge and the result is the same except that i can drill it with satisfying ease.


in each case the entire campaign took less than 15 minutes. i stopped it at that as the leads were not matched and one was melting. i think it could go for longer and melt a larger quantity provided heat loss to atmosphere is minimised and several pairs of gloves are at hand.


all in all its a goer. the time it saves in not having to heat up is worth it alone. the whole kit including moulding boxes and sand fits in a suitcase. its quiet. its less of a fire risk. the consumable cost is next to nothing. and it can pour seemingly hardened steel in less than your average tea break on a tiny 'tee nut for my lathe' scale.


i am taking this one as far as i can, the next stage is to cast a refractory crucible with a tapered hole and plug in the bottom which is lifted to achieve a bottom pour thus negating the need to lift the crucible and maybe some non human electrode holders so you dont have to stand right above it.

all in all i have been smiling for a month or so on this one. my 5 yr old son and i have a growing collection of really heavy and utterly useless LEGO.

regards