Difference between revisions of "Foundry"
(→Refractory: Added refractory ingredients)
(→Literature and references: Added Prometheus' guide to metal casting)
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=Literature and references=
=Literature and references=
Revision as of 11:11, 28 November 2014
|Contact||[[Project Contact::Semafoor, Gori]]|
To make a foundry capable of melting reasonably large amounts of metal, more specifically aluminium, brass and bronze. In my wildest dreams also cast iron, but that may not be realistic
Gori made a small foundry out of a soup can, a propane blowtorch and some refractory. This works reasonably well and never fails to gather a crowd. It only melts approximately 0.2 l of aluminium, and this is clearly not enough to do any real work.
Semafoor is gathering materials to build a second, much larger furnace out of a 60 l oil drum. Should look something like this >.
Key points are:
- Movable on its own wheels because it will be heavy
- A lid to reduce the heat loss at the top (big problem in the soup can furnace
- Incorporated device to lift the lid up and to swing it to the side
- Lid will be mounted on a tube that will slide into a larger tube of the frame
- Lever + Cam to lift the lid a couple of cm, to be clear of the bottom part of the furnace
- Same lever will be used to swing the lid sideways
- about 5 cm of refractory all around. Probably a bit more on the lid for rigidity
- Electric blower to provide more air for combustion > more fuel > more heat
- Fuel: Not sure yet. Possiblities are:
- Coal: Low initial investment. Needs a specific design to get the air at the right places. Dirty operation
- Propane: moderate initial investment. Relatively expensive to run. Easy to run. Cleanest fuel.
- Waste oil: Motor oil or vegetable oil. (nearly) free to run. easy to run, quite clean when running. Vegetable oil would be CO2-neutral as well. Most hackable fuel (dedicated fuel system and all)
A 60l oil drum has been acquired. It now needs to be separated into a part for the lid and a part for the lower body. The lid needs some reinforcement to be lifted and to keep the refractory in. The lower body needs a drain hole (in case of crucible failure, to let the molten metal out) and an air intake hole for the burner flame.
The frame needs to
- support the furnace body
- be strong enough to transport the entire furnace on its wheels
- support the lid lifting and lid rotating mechanism
The wheels for the foundry are probably the first thing to cast using this furnace, as an (easily replaceable) aluminium wheel would be sufficiently heat resistant.
Depends on whether propane or waste oil is used
Three blowers are available:
- Low power dual 115V Xerox blower
- medium power domestic heating blower
- reasoably high power forging blower aquired through Pietdv
Good things to have in a refractory
High alumina content
Air pockets (for improved thermal insulation) by adding (Styro-)foam beads
Fireclay (no idea what this is called in Dutch
Grog / ground bits of firestone / chammotte stone
Bad things to have in a refractory
Portland cement: breaks down around 550 degrees Celsius
(silica) sand: At high temperatures the crystal structure expands, resulting in cracked refractory
bentonite: also known as kitty litter box filling. Not sufficiently heat resistant.
Materials that may be good or bad (unsure)
Perlite: good insulation, not super good at high temperatures
Probably sand casting, see