Scrap metals for casting.

I do mostly structural casting for machinery; it's all aluminum. I mix my aluminum scrap: a lot of material from broken bike parts (of which I always have plenty) and from machining scrap, and a lot of scrap aluminum from casting operations. The best material for casting is piston heads from engines. Nothing else is close. This stuff pours so well and takes wonderful detail, has low porosity and good post-casting machining properties. Aluminum pop cans, on the other hand, are nearly useless. They're pure aluminum, so the product formed is not very strong, and the aluminum itself doesn't cast too well. Plus you end up with about 60% slag and 40% aluminum from pop cans. The amount of slag you get is directly proportional to the surface area of the aluminum you're melting, and the amount of metal you get is proportional to the volume of the melt, so what you want is big chunks rather than thin sheets. Even aluminum tubing is not really that great for melting; I melted down five or six old lawn chairs and got a lot of slag from them. It wasn't very rewarding.

In marked contrast, I also got a Subaru engine, which has aluminum cam carriers, heads, and block, as well as pistons. There was no WAY I could fit all the pieces into my crucible, or even into the furnace, so what I did was: I built a pile of bricks around a chunk of engine block, shoved the burner in, and blasted the holy heck out of the block until the aluminum bled (a funky way of putting it, but that is what it looks like: some metal, probably the zinc in the alloy, begins to sweat out of the surface and bead up in pinhead-sized lumps all over the face of the aluminum) at which point I'd shut off the burner, pull the chunk of aluminum out with tongs, put it on concrete, and smack it a few times with a sledge. It would crumble like cottage cheese into small and big chunks of aluminum. The large chunks went straight into the furnace; I had it tilted way over so I'd melt a huge pool of aluminum in the bottom of the furnace, yank the burner out, then tilt the furnace and pour out the burner inlet, into a muffin tin I had. The ingots I made were precisely the right size for the crucible; the one engine block yielded about 70 ingots, each weighing just over a pound. That one block will keep me casting for three years, I suspect.

Copper and cast iron are both doable with this furnace, but they require a whole lot of heat, a long time to melt, and a better crucible than the steel crucible. I've melted some copper in a small crucible I made from a piece of 2" pipe with a cap welded on the end, but there aren't many things I do with cast copper. I've also made a little bit of brass by melting copper with new pennies, but it is not very pleasing; if I find a good source of scrap zinc I'll put a lot more energy into that project. You have to melt the copper first and then add the zinc; their different melting and boiling points are such that the zinc will fume out of the melt before the copper gets fully melted and you end up with just copper. I also did a bunch of recycling; I got large quantities of salvaged wire from old buildings, bundled it up tightly, insulation and all, and stuck it in the furnace. The insulation went away and I was left with nice chunks of copper in the bottom of the furnace. It would be interesting to make some sort of funnel or drip pan so you could collect the copper in a nice round ingot; I might have to do this at some point.

When I was a child I spent a huge amount of time melting lead. This was a bad idea. Lead is nasty stuff to inhale, particularly in gas form, and has a low vapor pressure. Do your brain a favor: don't melt lead.

Magnesium, titanium, osmium, tungsten: nope. Not a chance. Don't even bother trying. Although a bit of magnesium sure does flare up quickly in the furnace.

This page written on 12/15/00, last modified 23 May 2023.

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