In previous posts, I briefly mentioned the furnace that I built a year ago from repurposed steel cans, but I haven’t talked much about what goes into making one of them. I guess I should start by saying that I didn’t build a steel can furnace, because I built many steel can furnaces, however, I have never had more than one active steel can furnace at a time.
As I mentioned in other metallurgy posts, I realized that I could melt metal very cheaply over coals, but I needed something to contain the coals and something to contain the molten metal. These two items that I needed are called a crucible — the container that holds the molten metal — and a furnace — the container that holds the crucible and contains the heat. I made a makeshift furnace from a steel can by simply placing a large hole toward the bottom of the can, which acts as an air intake to help the charcoal burn; the hole only needed to be as large as the steel pipe that I used to direct the air onto the coals. I then made the crucible from a slightly smaller can that could fit into the furnace by pinching part of the rim to form a spout and making two small holes through which a piece of wire could fit; this wire acted as a crude handle for my crudcible — I mean crucible.
This can furnace was only a temporary measure, but I found that I really enjoyed melting metals in my new furnace, and I continued to use the furnace much longer than I was initially anticipating. As I continued to subject the cans to temperatures exceeding a thousand degrees, I noticed that layers of iron oxide began to flake off, and I eventually discovered that a large hole had developed in the bottom of the cans; this rendered the furnace unable to hold coals and the crucible useless for containing liquid metal. This is because the extremely hot iron reacted with the oxygen in the air and the water that I used to quench the cans (I was too impatient to allow the cans to cool down slowly).
By the time the cans fell apart, I wasn’t ready to quit my metallurgy experimentation, therefore, I made another set of cans, and when those expired, I made another, and so on. I am now left with a stack of 8 destroyed cans. The fact that my temporary can furnace needs to replace often is not something that you may realize if you aren’t the one making it. I didn’t necessarily realize that my cans would disintegrate when I began working with them. This is one reason why I would not recommend making this type of furnace.
Another issue is that I cannot adequately heat the tall walls of the can crucible, which causes metal to cool and solidify on the walls of the crucible as I attempt to pour it. The tall walls also do not allow me to scoop the dross off the metal, which leaves behind a sticky mess of dross and metal in the bottom of each crucible.
I would not recommend that you attempt to make your own furnace out of cans, especially since this is very dangerous and you risk severely burning yourself or catching something on fire due to the lack of insulation. Definitely wear heat resistant gloves when handling anything hot, especially when it is 1,500ºF, like in my case. I know that I haven’t been very responsible about wearing gloves around my furnace in the past, but I have more recently realized just how dangerous this extreme heat can be. Always wear appropriate Personal Protective Equipment (PPE).
Are there any questions you have about my metallurgy experience?
Onward American 