evil_lurker
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Purification of aluminum...
Suppose I were to melt an engine block and/or transmission (its been done before  ).
And lets say I wanted to refine the unkown alloy.
What would be a good way of doing so? Some kind of flux?
Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in
beer.
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roamingnome
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assuming your melting like the whole thing, a mix of metals.
phase diagrams then show how to crystalize pure metal regions
http://www.thefabricator.com/Articles/Photos/676/fig2.gif
the text book and engine blocks seldom match cleanly i would guess....
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not_important
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Most alloying metals for aluminium are less reactive than Al, it's like trying to get the silver and gold out of lead. It is possible that there is a
flux that Al2O3 is not soluble in, and that can latch on to the alloying metals, most likely you can remove silicon that way.
The basic methods that I know of are
find a metal that has very low solubility in molten Al, and melts at a low enough temperature that it and molten Al can coexist, and that the alloying
metals are soluble in. Mix the two together, allow to separate, remove the other metal, repeat. Don't ask me what metal would work.
electrorefine the aluminium - plate from the impure metal as anode to pure Al cathode, using a suitable electrolyte. This patent is similar in
concept http://www.freepatentsonline.com/RE30330.html
fractional crystallization US Patent 6398845
Passing AlCl3 vapour over Al at a high temperature, which forms AlCl, then leading that through particle filters to a cooler area where the reverse
reaction back to AlCl3 vapour and Al metal occurs; the AlCl3 is recycled but may need a purge and replace ever so oft.
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Eclectic
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The simple way to get fairly pure aluminum from a scrap engine block or transmission would be to take it to your local metal recycler and trade it for
Al electrical cable, 99.5% pure, some Mg, some Si.
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evil_lurker
National Hazard
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Yeah, I'm pretty limited in my capabilities.
Generally I just take a 55 gallon open head drum, burn a hole in the side with an arc welder and drill a 3/4" hole in the bottom, prop it up on
blocks, fill it halfway with good oak or hickory firewood, and set the engine or transmission on top, and finally shove a pipe hooked up to a shop vac
in the hole in the side.
Light it up, turn on the shop vac, and in about 30-40 minutes the whole thing is melted and run out the hole in the bottom. Cheap and effective blast furnace, and usually the drum manages to survive several
heat cycles.
Temp on the outside of the drum can usually get to around orangish, and the copper pipe I use to feed air into the drum usually melts some.
Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in
beer.
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12AX7
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Transmissions and other cast products are around 10% Si and a few total percent other elements. Coincidentially, it's the perfect alloy for
casting...
Tim
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