A few questions about maximising the efficiency of a mini forge for melting and ingot casting

[boltguntotheface]

Hi team!

Relatively new to the hobby, and I'm hoping to ask for a few insights by a few of you learned gentlemen!

 

The Context:

I'm quite fixated on creating as much of my tools and equipment myself as possible (not including safety gear, for that only the best I can buy). I've got quite a collection of Aluminium cans. I live in a relatively small apartment, so no room for a workshop just yet, and most of my foundary needs to be portable so I can transport it to somewhere that it's safe to actually work with molten metal. More than that, my scope of projects is quite limtied due to space constraints. But what I can do, is melt down all these cans into ingots, so they're easier to store, and ready to work with when I have space for a proper work space!

The Goal:

As said before, for my first project I'm planning to melt several hundred cans down into Aluminium ingots. THe reason I've chosen this project is because, well, the cans are there. I already have them. And that means that I effectively have a source of cheap metal that I can use for my next few projects, that I won't shed a tear over if I mangle or waste. I just need to make them easier to store, by changing the shape of them into ingots.

The Forge:

I'm building a small mini forge. Because it's so small, and I don't have the space, budget or no-how (yet) to build something bigger, I'm trying to improve the efficiency of this one before I test it with my first melt. It'll be hot enough to melt Aluminium, but not much else. It's also going to be running on propane, so I'm very concious about keeping forging times to a minimum due to fuel concerns. 

The Questions:

I'm looking for some insight into things I can do to increase the amount of Aluminium I actually reclaim from these cans, and reduce the amount that's lost due to Oxide forming. Right now my plan is to create a small pool in the bottom of my crucible by way of balling up some Aluminium foil. I then intend to slowly feed cans into the pool, until it's big enough to pour. I intend to use salt as a flux to try and keep the metal from mixing with the slag. 

Prior to the melt, I intend to crush my cans up. I've read that reducing surface area reduces waste. In addition to crushing the cans, would it be worth my time to cut the crushed cans even smalled with a pair of tin snips? I'm aware it's labour intensive, but I could do it while catching up on some much needed Netflix viewing, and besides, I'm in this for the experience, so some extra time doesn't really bother me. I was thinking if I cut the crushed cans even further, I could not only reduce surface area, but also pack more into the crucible and hopefully reduce the total time it takes to melt, and therefore hopefully reduce the fuel used. 

My next question is in regards to the slag. My understanding is that it's essentially a waste product, but one with very high heat resistance. Would it be worth saving a bunch of it in a tub, and then adding it to the refractory lining of my next forge? If it's not going to melt in a forge hot enough to melt Aluminium, then it's not really worthless, is it? Would adding it into a refractory lining of a future forge be beneficial? The way I see it, I could cut it in in small amounts to reduce future material costs. It doesn't actually take any additional time to just throw some into a 9l storage tub before I dispose of the rest, I'm just wondering if it's worth it. 

My last question is on quenching. Once I've cast my Aluminium ingots, I see a lot of people online putting them in buckets of water. Does this actually do anything when only casting ingots, or is it just a way to cool them faster and let them be handled with bare hands sooner? Since I'm just converting this metal into ingots for easier storage and transport, I'm not particularly concerned about the properties of the metal; they'll all be remelted eventually anyway. 

 

Thanks in advance for any insight you can all offer! Hopefully I'll be posting my own write ups of how it all went soon!

[JHCC]

7 hours ago, boltguntotheface said:

a few of you learned gentlemen

And ladies!

[ThomasPowers]

Well first off: what is it that you want to use the resultant Al for?   Cans get a premium price at the scrapyard as they are preferentially recycled into *cans* and there is a large market for those.   If you want to cast Al, items that have been cast are generally a better alloy for melting and casting.  As you have mentioned Al cans are mainly Al oxide with a sliver of metal between them.    Any chance of turning them in at a recycling place and getting better casting scrap?  With the time and fuel you will be getting quite EXPENSIVE Al not cheap metal!

You ought to be able to  find a 5 USGallon steel pail and build a fibrous refractory insulated melting furnace fired with a propane burner.  Be sure to coat the refractory with rigidizer and a good wall of castable refractory for wearproofing.  It should still end up carriable by the bail; especially if you build a removeable lid.

Have you read the archives at backyard metal casting.com? Or the currently active forums at thehomefoundry.org?   I Forge Iron is primarily a blacksmithing oriented group and so you might do better with one dedicated to casting.

[Frosty]

Welcome aboard, glad to have you. Do you have a name, nick name, web handle, etc. that's less cumbersome than your login we can address you with? 

Welcome to the club! Lots of folks have the idea of melting aluminum cans, thinking any number of myths are a good thing. Lets see: first, Scrappers will give you much less per lb. kg. etc. for your ingots than for cans. Cans are covered in printing, no? The way they make the pigments stick is by anodizing the aluminum first, oxidizing the surface so the paint, ink, whatever, actually penetrates the surface and stays. So, not only is the surface already oxidized there are all the elements in the pigments to contaminate the ingots, for example White is titanium oxide. That's just what happens to any value as to scrap value.

Then there's the aluminum alloy itself. Cans are NOT a casting alloy they are an extrusion alloy, a tiny pellet of alloy is dropped into the female die and the male die is pressed in hard enough the aluminum pellet becomes plastic and is squirted into the space between the dies making the can. This alloy has very different properties than a casting alloy. 

You can buy a good refractory to make your melter much cheaper than the cost of the propane necessary to make enough aluminum oxide to do anything useful, not to mention the expense of processing your slag into useful form of aluminum oxide. 

If all you're doing is casting aluminum a Gingery melter works a treat, we're talking fire bricks and charcoal melter. Killing time around the camp fire on field jobs I used to melt aluminum debris in the camp fire for giggles. It's a low temp melt.

If you must use salvaged aluminum use salvaged castings, Thin section castings like engine cooling fins or transmission cases are low viscosity alloys and produce fine detailed castings. It became a game in high school metal shop class to put a fingerprint in the green sand mold to sign castings. 

NO, do NOT cool castings in water unless you WANT mostly aluminum oxide! People posting videos on the internet don't need anymore expertise than a camera and youtube account. Cooling any casting in water is a red flag that they don't know what they're doing. 

As suggested there are casting fora where you can learn to do what you want just by reading.

Frosty The Lucky.