My first metal melting furnaces were designed to
use charcoal for fuel. These furnaces had a pipe in the bottom center that
air up through the center of the mass of charcoal to maximize the heat. When I switched fuels to oil (and sometimes diesel), I just
let the flame blow into the furnace through the same hole. This is a rather inefficient method of heating the crucible. The flame should
swirl around the inside of the furnace, and thus around the outside of the crucible in order to maximize the the heating of the metal.
Today I finally decided to fix my furnace to correct the air/flame flow.
I started with the existing hole and using a
pneumatic chisel, chipped the refractory away to allow the pipe to swing
toward the inside wall of the furnace. I mixed some high temp refractory ( MINRO-FIREŽ CAST F80 made by Allied
Mineral Products) and pressed it around the hole which is now correctly aimed toward the side of the furnace. I
used a plastic pipe as a form for the hole. This pipe will be removed when the refractory mix sets up.
The following photo shows the inside of the
furnace. Clearly, the flame will follow the correct path now. I used some of
the refractory to patch the inside wall that was damaged by the flame where it hit before the fix.
While I was mixing refractory, I made a new
"stool" using a dvd container as a mold. The stool
(also known as a "plinth" is placed into the furnace and is what the crucible sits on.
Here is the repaired furnace with the burner and stool in place.
The crucible is filled with pieces of aluminum horseshoes and the propane lit to start the melt.
Now the oil is turned on and the real fire
starts! Notice that the flame now wraps around the inside of the furnace.
Wish I had done this sooner. I melted and poured 4 crucibles full of aluminum to make ingots in just an hour.
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