by Fomen38 » Fri Feb 27, 2015 1:29 pm
If you have an old propane tank, and a home depot near your house, you can make a foundry for melting scrap aluminum. If you buy a graphite crucible, you can go way beyond just melting aluminum. The refractory cement in the foundry, and the graphite can withstand temps in excess of 4000 degrees. Aluminum melts at 1280 (approx). You can melt steel, stainless steel, brass, bronze, etc.... With this foundry, some good charcoal briquettes, and a good source of forced air (like the "blow port" on a shop vac if equipped with it). I've gotten my foundry so hot that it singed the hair off of my fingers when my hand was 6' above the charging hole in the top. You can also buy the petrobond sand in bulk on ebay. That is the sand you use to cast things. It's pretty awesome, and when packed it will hold it's shape VERY well. You can find endless instructional videos on YouTube. Once you make the foundry, you can use it forever. Also, if you don't have access to refractory cement, you can make your own. It's just a mixture of regular cement, silica sand, and either pearlite or vermiculite (which are the little white balls you see in potting soil). The first time you run your foundry, you will abolish the vermiculite leaving small air pockets in the cement. These in turn create insulation, as air is by far the best insulator. If you are interested in the refractory I used, it's called Mizzou Plus. It comes in 50lb bags, and one bag is PERFECT for making a foundry out of a 5 gallon propane tank.
I cheaped out on the heat source. You can actually buy some basic plumbing parts, and make a forced air furnace with another propane tank as the fuel source. This is definitely the best way to go, as there are no impurities introduced into the inside of the foundry. You also need a degasser and a defluxer. I used soda ash (which is essentially baking soda that has been baked at high temp for about 30 minutes to bake off any moisture), and lite salt (salt substitute). About 1 teaspoon of each. Drop it in, stir it up, and remove the dross from the top. You will have beautiful, molten aluminum that is ready to pour.
Wayyyyy too much info, I know. But if any of you guys are interested, I will make a list of required components. You can use the petrobond sand over and over again as well. It will scorch the sand where the molten metal touches, but you scrape that stuff off, and reuse the rest.
Cheers