Using a DC welder for melting 100g of (stainless) steel works fine, but it takes up carbon from the crucible. So I made a DIY cruible from cell concrete lined with 1600 C rated mortar and drilled a hole through the bottom in which I put a twisted 2mm steel wire which is connected to the (+) of the welder and acts as an anode. The wire has contact with the steel in the crucible. Holding a carbon rod connected to the (-) of the welder creates an arc which melts the steel, and rather quickly. But it still absorbs carbon from the cathode making it more brittle. In order to melt fully carbon free I tried to replace the carbon rod with a steel bar on the anode but the arc is not sustainable anymore. Why ? Steel vaporizes even easier than carbon, so ionized vapor would work. Or does the steel vapor not ionize (which I doubt, otherwise the nice familiar blue color of welding would not be there) ? Attached pictures of the small crucibles, (outer) size is about 10cm (4").
This is a really wild guess, In my teenage years I worked for a drive in theater that used carbon arc projectors, they had two carbons against each other. the light off those projectors was pour white, the carbons were about 3/8 inch and about 4" long they would last all night on a triple header movie, you had to adjust them but they didn't burn away like they do when using a carbon arc torch against iron. I'm wondering if they are not mostly inert against each other but reactive when against iron kind of like carbon a battery. Just a thought Art B
My experience is similar Art's, I used to work at a place that used a carbon arc light source to expose litho plates and I don't remember those carbon rods getting replaced very frequently either.
It is not a question about carbon rod consumption (which is not that quick when using the rod as cathode), but replacing the carbon rod cathode by a steel cathode. In the latter case, the arc cannot be sustained.
I didn't make the point I was trying to, The Carbon may be carrying a polarity into the melt, In the Alcoa aluminum plant that shut down about 25 years ago, they used copper electrodes in the melting of the aluminum. I don't know if that would work in iron or not. Art B
