Aluminum Casting
Entry posted by Kzoppistan
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I now present my miniature blast-furnace.
It will be used to melt scrap aluminum. It should be ready to be fired in about 4 days once the curing is completely done (it's been 3 now). It is constructed out of a large steel can and quickcrete. As you can see, I sawed a steel pipe with a hacksaw and inserted it in the bottom by punching out and filing a hole in the bottom of the can before filling the can with concrete.
By first figuring out the volume of the can, and then subtracting the volume of plastic coffee can which was submerged in in it, I managed to calculate how much concrete to use without wasting any. I also had to figure out how many cubic inches a 60 pound bag of mix would first make, then use that number to divide the recommend amount of water in ounces to get the amount of water to add, too.
After it is cured, I will fill it with briquettes, and the steel can crucible, add the scrap aluminum, set it on fire and cover it. The pipe will serve as a way to force air in from a hairdryer (I actually ended up using a cheap roadside tire air compressor) in order to raise the temperature (1220 F) high enough to melt the aluminum.
I expect to get one or two runs out of it before it crumbles. Concrete is not a very good refractory material, but it is cheap and so should serve as a good beginner's test run. A few things may go wrong, such as not reaching a high enough temp. If that doesn't happen, I will feed a propane line through the pipe. Also, very unlikely, but it may actually over heat, melting the crucible and pouring the aluminum melt into the bottom of the can which would pretty much ruin it. Also, with the residual water in the concrete, it might explode. So there's that.
In the meantime, I will be carving a positive of a small decorative gear out of wood to press into the mold, crafting a box and casting a sand mold, and filing the paint off the scrap aluminum.
Then the action begins.
I will post the results when it is all done.
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Done
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Here is the result of my aluminum can melts. I
set up in the park. I got a few curious looks, two people stopped by to
watch and several people shooed their children away. The loudness of
the compressor was my only major concern. It took only
40 minutes for the cops to arrive. Apparently, there is nothing illegal
about constructing a portable mini-foundry in the park, so after
explaining my activities, I was wished a successful adventure by the
inquiring police officer (who was quite friendly... in a nervous sort of way) and left to my own
devices. Very fun.
This is the mold I used. Orginally I wanted to make a decorative gear, but
after putting everything off for a month and not wanting to spend more
time carving the shape to imprint, I finally decided to just make an
ingot mold by hand. I purchased a 50# bag of Hawthorn fireclay from a
local supplier (Mudworks of Lexington, check them out for your pottery
needs). It has been mixed 50/50 with play sand. Next time I'm going to
create a box with removable sides and use an actual carved piece for the
positive.
This was my set up, the air compressor, which acted as the bellows was
powered by my jumpstarter, fed into the pipe at the bottom of the
furnace.
As you can see, at the very center of the crucible is a small glob of
liquid aluminum melt. What I found interesting was that, contrary to my
fears, the aluminum cleaved together and excluded non aluminum
particles.
Here is the pour directly after cooling. Due to excessive foreign materiel
and a sloppy pour, the dross, of mostly al. oxide I reckon, filled in
the top left of the mold.
The final result after removing the dross and doing some filing. The ingot
is extremely light weight. If this weren't my very first attempt, I
would melt it down and use a better mold. But alas, this piece of
mangled metal is my first-born, my own little bit of the tri-force, so I
will keep it for sentimental value.
So there you have it.
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