Build a foundry and sand-cast aluminum.

Step 8 Destroying your aluminum cans.

It is important to seperate the parts of the can, as they all produce different amounts of dross (trash in the metal which has to be removed), and should be melted at different points in each smelting.

The 3 sections which have to be seperated are the top, the sides, and the bottom of the can.

My favorite method for destroying the cans is illustrated in the pictures. Unfortunately, I can't get the image notes to work, so you'll have to read the procedure up here and follow along with the pictures below.

1. Cut or rip the can in half.
2. Make a slit in the top half, perpindicular to the lid.
3. Tear along the slit and pull the siding off of the can top.
4. Make a slit in the bottom half of the can, at an angle to the bottom.
5. Tear as close to the bottom as you can, and remove siding.

This goes much faster if you form a production line with some friends in which one person has one of the steps above assigned to him/her.

I sort the cans into boxes of halves, siding, tops, and bottoms, with the occasional box for cans with painted tops or bottoms.

Once you're done with your cans, it's time to ready your foundry.

Comments

[TimmyMiller]

what if you just removed the paint from the cans?

[pfred2]

I just smash the cans and pack them into my crucible as they melt. I do get a lot of dross but cannot imagine how tearing cans apart changes that any. Cans are drossy because they have a lot of surface area so they have a lot of oxide on them to begin with. Now someone suggested to get a puddle of molten aluminum then plunge the cans into that in order to cut down on further oxidization. If you do that though the cans had better be 100% dry or it'll blow up in your face!

[Fenris The bbw]

I do do that and all I get is steam. I still wouldn't reccomend it though because getting cold water on the aluminum cools chunks of it down. I cut the cans up so that I can use the parts with the least paint (the tops and bottoms) first. They produce less dross. When I have a large aluminum puddle, I then put the cans sides in. They have more surface area-to-volume so putting them in last cuts down on oxidization.

[jtobako]

I'm sorry for the argument going on below. This is a much better instructable on the subject than others here. I'll shut up now : X

[jtobako]

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[pfred2]

Then they cannot be too wet. Water and extremely high temperatures usually don't mix too well. I have had it happen even with molten lead, which is half the temperature of molten aluminum.

[jtobako]

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[sharpstems]

I am going to violate the "be nice" policy. This is a stupid and dangerous thing to say. Adding water to molten aluminum is extremely dangerous. -And very different than adding aluminum to wet greensand.

Anyone who knows anything about metal work - or elementary physics - can explain why -and explain why all of your examples are foolish. There is no need to debate the question here. Just because you havent gotten hurt yet dosen't mean you should tell amature metalcasters not to worry about adding water to their crucible.
Before you run your mouth off anymore, read "PREVENTING MOLTEN ALUMINUM-WATER EXPLOSIONS" at http://www1.eere.energy.gov/industry/aluminum/pdfs/explosions.pdf

Have a nice day.

[pfred2]

That must be why they never tried dumping water on the outside of steam engine cylinders. Don't you think? You want steam energy you have to confine it, then things get interesting. Water plunged under the surface of most molten metals becomes confined steam real fast.

[jtobako]

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[sharpstems]

Good idea. A bad idea would be to replace the water with MOLTEN METAL (a thick liquid) And to replace the air hoses -around 120psi?- at 8bar which means it will expand about eight times ---- with water that expands sixteen-hundred times as it flashes into steam.

Why on earth would you compare sticking an air hose in a bucket of water -- to steam expansion in molton metal?

"be nice"

[pfred2]

Good luck to you. Liquid metal is hardly a bucket of water, nor is compressed air spontaneous steam. But whatever.

[jtobako]

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[sharpstems]

No, we can't. However, I can post some information from people who actually know what they are talking about. This is from an Alcoa publication.

During casting operations, there is a risk of a sudden release of molten metal due to process upsets onto casting equipment, pit walls or the pit bottom where water accumulates. As molten aluminum contacts the water, a steam film forms on the surface of the metal. The steam film can destabilize as the molten aluminum contacts other surfaces in the pit. When this occurs, the water spontaneously transforms from a liquid to steam leading to a high pressure steam explosion. While these explosions are infrequent, the possible consequences are a major concern for safe aluminum casting.

[zimmemic25]

if you put water into liquid metal, it gets very hot very quickly. this produces very much steam very quickly. if it was enough water to get under some of the metal the steam can accellerate them like if they would explode.

[jtobako]

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[pfred2]

When water changes into steam it expands in volume 1,600 times. Do the math. It wouldn't take too many drops to throw your entire crucible into the air!

I wouldn't plunge anything into a puddle of molten aluminum that had a sweat of moisture on it, let alone actual liquid.

The puddle of metal is a seal. You can pop the top of your can and it won't make any difference at all. I can only guess that so far you have been lucky and have not trapped any steam in molten metal.

An epic steam explosion?

http://en.wikipedia.org/wiki/1883_eruption_of_Krakatoa

[jtobako]

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[sharpstems]

Good point. How long does it take for a drop of water stuck to a piece of beer can to turn into steam when you submerge it in MOLTEN ALUMINUM....? It happens immediately--That's why pfred2 left it out of the equation. THere's not really a time delay And your equation "left out" how much time it takes for the average city to receive the equivalent energy of an atomic bomb from sunlight. --It's about a year. The whole point of that example is that IF the energy was released instantaneously (kind like water turning to steam)- THEN it WOULD be catastrophic. Yes, it's all a mater of scale. And that scale is 1600/1

[jtobako]

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[pfred2]

How much time do you think it takes to heat up an aluminum can at 1600F ? Darwin is waiting for you!

http://www.darwinawards.com/

[jtobako]

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[pfred2]

Is this how you always argue, by putting words into others mouths? Maybe it works with your friends but not with people like me. You do wish you lived in my world, but we have a minimum IQ requirement. OK then so just how much water is safe to plunge into molten aluminum? And if anyone is hurt by your sage advise just who are you exactly so that you can be held accountable? Backpedal faster, I am a busy individual. The simple fact is most of us have better things to do than count the dew drops in our beer cans.

[jtobako]

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[pfred2]

You can copy and paste, congratulations. Now where did I say (water sinks in a heavier liquid) I was discussing materials plunged into a puddle. Or (temperature change is instantaneous) it does not need to be. Or (where gas cannot escape a liquid)? Your words again! It escapes and can take molten metal with it, that is the problem. Where did I say from above? Your words not mine. I did not say any of those things. Maybe you should work on your reading comprehension skills? P.S. There are many different kinds of IQ tests. Apparently your only experience is with fake online tests. Real ones do not typically even involve text. Spooky huh? And no, you don't want to know how I know. It'd be more bad news for you. (something to do with me actually taking real IQ tests and my results I'm sure!) From here on in I am going to have to consider the source and ignore you. You have absolutely no credibility left. I'm sorry but that is just how it is.

[jtobako]

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[me835]

these are only answers to the questions that you pose above. How does the water get under the aluminum for the steam to push it upwards if it does not sink? the water is contained on bends and curves on your can pieces that are being pushed under the molten metal. How do you assume a buildup of gas pressure in a liquid without undue speed in temperature change? both aluminum and water have exceedingly high thermal conductivities, transferring heat very quickly. then, that expansion of water into steam generates a considerable amount of kinetic energy, which, according to a principle whose name i can't remember, is transfered by the fluid (steam) equally to the surrounding matter (aluminum). most of this energy passes through the aluminum into the crucible walls and bottom, but the upward energy from the steam will fling the aluminum upwards, although how much and how high will depend on the amount of moisture involved. again, I am only addressing the questions that you yourself posed.

[jtobako]

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[jtobako]

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[me835]

i didn't realize the 'steam jacket' thing, so thank you for pointing out something i didnt know before. however, i assume nothing even remotely close to this 'aluminum shell' concept you propose here. i know that that is impossible. i am not assuming an explosion in its truest sense, but more a high speed shove from the newly expanded steam. that's all. and, check out this link:

http://en.wikipedia.org/wiki/Steam_explosion

see the second paragraph, second and third sentences. it describes this perfectly. the rest of the article is semi-relevant as well.

[Fenris The bbw]

Hey can all you guys stop arguing on my instructable? It's getting kind of annoying. I think I'll do us all a favor and make an instructable on molten-aluminum safety. Untill then, please go bicker somewhere else.

[pfred2]

Two reasonable points of view are required for an argument so that is not going on here. Lacking an argument invalidates bickering. Happy now? It really is all about semantics isn't it?

[Fenris The bbw]

The points of view don't have to be reasonable. One person can have a reasonable point of view but be unwise or insecure enough to continuously argue with someone who doesn't.

(hint hint)

I've been a little too busy to check on my instructable lately, my family and I are renovating a new house, and I don't have much free time.

If I was here to take part in this discussion here's what I would have said:

Steam explosions are very real, and a very real concern to all who work with molten metals. They are caused by water becoming trapped within a molten metal and then rising to the surface, shooting from the metal in an explosion of steam that carries molten metal with it.

Sounds scary right?

It should, it's F@$#ing dangerous.

Trapping even an ounce of water within a molten metal could end with destructive drops of molten alumimum flying everywhere, searing flesh and burning everything they touch! (This is what pfred2 is describing)

OMG PANIC!

However, a can with a few drops of water on it will cause (if anything) very tiny, very harmless, bubbles. (such as jtobako describes)

OMG PANI-whoa hold on a sec....those are actually kinda cute.

In fact, even if (IF!) there was an extraordinarily large bubble that shot a little aluminum towards you, that's not as dangerous as everyone seems to think. If you wear the proper safety gear (lots of thick leather and some form of face protection) the drops will not burn through to your skin, but will stick to your clothes instanty hardening into a cool little dot of aluminum

I take precautions against trapping water by cutting up my cans. Having open cans allows me to wash away all the incredibly sugary soda (a breeding ground for various fungi & bacteria) and not trap water in the cans. I can store them however I want and all the water evaporates away.

As I said in my previous comment, I plan on making some form of instructable that illustrates molten aluminum safety, which will of course show some molten metal explosions and how to prevent them. It might take me awhile to get around to it because I have a very busy summer, but I assure you it will get done.

If you have any requests or suggestions regarding what I include in the instructable please respond.

[pfred2]

Thanks I lost the will.

[pfred2]

Proof that William Deresiewicz is right!

[jtobako]

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[pfred2]

how many standard deviations part us? The more you know the more you know that you don't know.

[cvandeve]

I sometimes work with a small commercial aluminum smelter making 60lb ingots. If you get water in them, they will throw molten metal many feet. It is a lot hotter. If you throw an aluminum can into it, the can vaporizes before it hits the bottom. Always be careful around hot metal, it can set fires or melt stuff before you can react.