backyard / home foundry

[ToyMaker]

Can recycled beverage cans *really* make metal that is suitable for use in machine tools?

I am basically cheap and think it would be great to make add-ons (face plate, chuck adapter, vice, whaterver) for lathe and mill out of scrap. But my time is worth something and I don't want to spend any effort to make more scrap out the scrap I already have .

robotic regards,

Tom

[Ken_Shea]

Hi Toymaker,
Pop cans are pretty much a waste for casting as they are pure aluminum i.e. no real strength, I have read that about 40% of the casting material is slag. I looked into casting some items a while back that needed to be fairly strong and found that automotive pistons are about the best scrap you can use, very strong and cast nicely.

Ken

[ToyMaker]

I mentioned the "pop" cans because that is the most visible aluminum scrap. I also have access to various bits of channel, molding, housings, etc.
If pure Al is less than suitable for castings, what metals will alloy with it to make stronger parts (copper, zinc, lead - - -)?

robotic regards,

Tom

[Ken_Shea]

Most of the stuff around a house like lawn chairs, flashing, siding is pure aluminum so most of that will probably not be all that useful. I am not a metallurgists but I suspect zinc would stiffen it up bit I do not know what ratio I have read 1 to 8%. Most parts off cars would like cylinder heads, brackets, pistons, bicycle parts etc would make great castings. Do a search for alloying pure aluminum and see what you can come up with.

Ken

[gmfoster]

I have read that adding copper will make pure Alum much better. I think the copper will melt into molten Alum. Also when zinc is added you get potmetal which is stronger than Alum..

Garry

[castguy2003]

Take care when trying home mixtures. the percentages of alloying elements can be quite small. Also a good deal of aluminum alloys require an ageing or heat treat cycle.
I agree that scrap pistons would be good source material. They are usually alloyed with silicon.

[Hobbiest]

Just looking through the back issues here. Surface area is mostly impurity (slag), and you remove the impurities before casting. Since pop cans are so thin, the are mostly impurity. It just makes a clump of crap in the bottom of the crucible! There is no such thing as pure aluminum, at least not offered to the public. Every aluminum that you see is alloyed. Some alloys have better charictaristics than others. 60 series is most commonly used for structural components, especially when the need to be machined, because it has good strength charictaristics and is just hard enough to machine easily. Check out a book on machining from your library, and read about the different metals and their machining charicteristics. Almost any part cast will have to be machined too.

[trilect]

Pop cans are a great metal to use if you can melt them cheaply, you'll end up losing 75 percent of a can to oxidation because its so thin when you melt it.

I usually add a 1 inch piece of 1/2 inch copper tubing to a quart of can metal. If you plan on machining it double the copper added to the melt.

street signs are great as well, once again add the same amount of copper and don't get caught.

[shunka]

Best source for scrap aluminum are any castings you can find in this order:
1) Automotive parts:
pistons
transmission bell housings
engine manifolds
engine blocks
"all aluminum" wheels (be carefull of alloys or magneseum)

2) Any commercial casting/forgings
desk chair parts
razor scooters
bicycle parts
lawn mower decks
lawn mower engine parts
gas grill housings

3) other items
signs
tubing (lawn chairs, etc)
extrusions (channels, aluminum door & window frames, etc)

much of the above can be srounged on "garbage day" where legal.

cans are possible, seem to work best if crushed as small as possible and added to existing molten metal, but not the best choice.
-----------------------------
once one has good ingots of reasonably reliable consistancy, one can play with making alloys:

adding sufficient copper makes aluminum bronze

an alloy of 72% zinc, 28% aluminum makes a great low melt ZnAl alloy (super-potmetal) that has the following properties:
melts ~ 950 F
machines easily
excellent bearing properties
tensile strength between 53,000 - 58,000 PSI (mild steel ~ 45,000 PSI,
aluminum ~ 55,000 psi, bronze ~ 65,000 psi, nickle-siver bronze ~ 85,000 psi)
often used for machine castings where temperature is not an issue
polishes to a bright silver finish
takes plating well
possible to "anodize" but not the same process as aluminum

[pyroracing85]

Can chip scrap from a round stock be a useful source of scrap?

[shunka]

the problem with any small scraps (including aluminum cans) is the large surface area exposed to air. when melted, the amount of dross (oxidized metal & impurities) produced really gets excessive. You can also get more "gasses" dissolved in your metal. Some folks have had a certain amount of luck adding chips and shavings to an exist pot of molten metal, but there are 2 problems to keep in mind:
1) this stuff is usually "floor sweepings" and thus filled with "nasty bits" -
ie: contaminants of unkown origin. If oil or chemicals are present, or inflamable "stuff" the resulting "pop" could be hazardous to your health.
2) the "bang per buck" is really quite low - you don't get much "good" metal for your efforts, but I can guarentee you will have a certain amount of hazard, a lot of dross, and a lot of work.

Also, adding anything to a pot of molten metal- even a new ingot - can be inherently dangerous.

If you look about, (dumpster diving!) you may find that there are more "free" castings available than you thought....

melt safely and
best regards
shunka

[DragnsBane]

Most aluminum used in automotive applications is A356 which casts easy and also responses well to a T5 or T6 heat treatment process. A356 is an excellent material for casting.

Also on the "super-potmetal" you may be thinking of ZA-12 which has a tensile strength of high grade cast iron and actually exceed cast iron in some cases. The alloy consists of 88% zinc (pot metal), 11% aluminum, and 1% copper all by weight.

From what I have read most aluminum extrusions are 6061 and do not make a good casting material but I could be wrong on this. Be nice if I was. I could make a killing on trash day around here.