Supporting > Casting
Casting Gray Iron
Casting Iron:
One group that still makes gray iron castings on a regular basis are the various art-iron folks in the States.
A local art-iron group are the ones who taught me how to use resin-bound sand, and ceramic mold wash.
They use cupolets (cupola with a lid) to melt their iron, and because they are typically non-profit art groups, they can readily purchase limited amounts of coke (coal heated in the absence of oxygen) as a fuel.
The generally use old radiators as a scrap source, since that metal has phosphorus in it, and thus has very high fluidity.
The local group has several iron pours every year.
They have helped me with learning how to cast ductile iron.
There is another larger group at the old Sloss foundry in Alabama; and many art groups associated with colleges.
The art of casting gray iron needs to stay alive, for many reasons, but especially to make model engines (in my opinion).
A few photos from a local art-iron pouring event.
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Casting Iron:
The art-iron folks all seem to use cupolas/cupolets, and they were very surprised to hear that I could melt iron with an oil-fired furnace.
I brought my furnace to one of their events, and demontrated how to melt/pour iron with a cupola oil-fired furnace.
This is my 2nd furnace, with a 1" Mizzou hot face, backed up with one layer of soft fire bricks, and two layers of ceramic blanket.
It remains cool to the touch on the exterior beer keg surface. It is actually made of several beer kegs, which were cut and welded to give the same diameter as a 55 gallon drum (I should have just bought a stainless 55 gallon drum, but I did not know they existed at the time I built this furnace).
The Mizzou hot face holds up very well to iron slag and the general abuse that an iron furnace experiences during operation.
Combustion air is provided by a Toro variable speed leaf blower, set to the lowest speed.
The burner is a Delavan siphon nozzle style, with a 10 psi pressurized diesel fuel tank, with 30 psi safety relief valve on the tank.
The PVC valve at the top of the leaf blower is a dump valve that is opened when the burner is first lit, to prevent blowing out the flame, and then slowly closed to provide all the air output to the furnace after the burner is lit.
Casting Iron:
This is my furnace design.
It can be used with a range of crucibles, from very small up to a #20, and with an extension ring, I think I could use a #30 in it.
The Morgan "Salamander Super" clay graphite is the one I use that is rated for ferrous metals and iron temperatures.
This furnace is designed to be modular, so that the hot face can be replaced easily.
I have found a product called "plastic refractory" that is rated 3,800 F, and it basically eliminates the need to replace the hot face, since it can patch any defects.
Plastic refractory is what the art-iron folks use to patch the interior of their cupolets.
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Casting Iron:
The scrap I use is motor end bells.
There is no need to clean gray iron scrap.
You can melt it with paint, oil, heavy rust, etc. and the impurities all come out in the slag.
Using a consistent quality scrap iron is important if you want quality iron castings.
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Casting Iron:
The hot face was made using castable refractory (Mizzou), and I rammed it into the upsidedown form using a wood dowel to pack it in 2" layers.
I dried it slowly with a propane burner, and then brought it up to operating temperaure using a temporary flat lid.
I built a permanent domed lid from 1" Mizzou, so that if it every cracks (the lid has not cracked yet), it will self-support like a Roman arch.
Total weight of the hot face is 70 lbs.
The plinth that the crucible sits on top of is also made from Mizzou refractory.
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