Sam or Mary Yancy on thu 22 dec 05
When I was into heat treating steel many years ago, the company I worked for had several electric furnaces.
They were about 10 feet across and about 15 ft deep - buried in the ground. Touter wall was about 1 ft thick of fire brick. Then inside that the heating elements which were strip metal of some sort, Then there was a large cast stainless steel tube inside that. The bottom had a cast stainless steel grate it rested on. The lid of the furnace (crane moved) was sealed to the top of the furnace with a bed of sand in a U channel.
We used these furnnaces up to to 2300F degrees (for hardning stainless steel) but usually ran them at 1900F degrees. To harden and deep carburize the steel we made a carburized atsmosphere by dropping/dripping pure kerosene into it abour two drops a munute (one way to make a carburized atsmospjhere - But be carfull - only injec it over 1300 degrees or so. We had a vent fan at the bottom with a spiral exhaust and a small spiral intake at the top to circulate the atmosphere. Kilns wer never Soot dirty - the stainless steel inner liner seel to be pure clean and neve any soot from the kerosine drip.
They worked extremely well - and we never got them down below about 600 degrees except for maintenance yearly. turned themn off, Opened them up. pulled the load, closed the lid. Inserted the mew load at around 300F started them up again. All material going into the kln was mounted on a single support and "crained' into and out of the kiln.
Seems like some of the design in these furnaces/kilns would work for us clay-arters. Sam In Daly.
P.S. I got hazardous pay for working there - Wore asbestos clothes when opening and " quenching" a Load at 1200 degrees (into a mmoving oil bath with a roaring fire). Learned so much about properties of metal there.