Anyone ever tried melting aluminum (for casting) in their woodstove?

[tradergordo]

Aluminum melts at 1218F, so I don't see why it would be a problem melting some for metal casting, inside your firebox, without over-firing, but I couldn't find anyone talking about this either on this forum or in a google search. Just curious if anyone has tried it? I have been meaning to build a little foundry for backyard metal casting for a couple of years now, but just have never gotten around to it, and now all of a sudden I sort of have a real need to cast something in aluminum for a project I'm working on... I know I should probably just build the proper refractory lined "furnace", but heck the woodstove is already there and won't cost me any time or money.

I'd assume you'd want to build a huge coal bed first, either that or keep the crucible covered to keep fly ash out, but then you wouldn't be able to watch the progress which could make things very difficult.

 

[PunKid8888]

I would think the contamination factor would be very high. The other problem is your going to need sustain +1200F in order to melt the aluminum, a good bed of coals will probably only hold that temp for 30mins or so. So now you have the problem of trying to reload the stove with this crucible in the way. I see it having a very slim chance of working, but hey try it out and let us know.

 

[karl]

I don't know about a whole crucible, but it burns the aluminum from my Marlboro packs very welll. What are you trying to make. I like to fool around with cast from time to time.

 

[annette]

Hi:

My BF has melted down aluminum in a fireplace--he says it's actually easier to do it in a fireplace than a woodstove. The hot spots are hotter in a fireplace, and air is fed from the bottom, which you want. In the woodstove he's tried melting aluminum a couple of times without success.

He built a little furnace out of old firebrick. He says you could maybe use regular brick if you're just melting aluminum. He likes the yahoo group called castinghobby.

Good luck, and what're you making?

 

[madrone]

Seems like more trouble than it's worth. On top of the difficulties you mentioned, there's not a whole lot of room to maneuver. I'd hate to spill a crucible of aluminum in my stove, or worse, out of my stove. If it were me, I'm sure I'd accidentally overfire trying to make sure it's hot enough.

I've used a very simple setup using expanded steel wrapped around into a cylinder about 20" in diameter and about as tall, with a circle of expanded steel on top. Wire some kaowool to it inside, and cut out a hole for a propane weed burner at the bottom of the cylinder. You can simply lift it off to get at the crucible. Easy to build. I'd say cheap, too, except for the kaowool. You can size it to your crucible. It's probably better to do this outside anyway. ;-)

 

[woodgeek]

I melted some Al years ago in a little electric oven I built. I just scored the heating elements off an old electric range, stacked 3 of them in the bottom of a sand-filled steel bucket (no galvanized), with a sheet steel lid and wrapped the works with fiberglass (doing it again, since glas outgasses I would use rockwool or build the whole thing out of firebrick). For a crucible I used a cheap 6" cast iron skillet (I sawed the handle off so it would fit in a smaller space); for a lid I used a terracotta dish that would normally go under flowerpots, to which I attached a wire bail. Total investment <$50. I ran it a bunch of times and cast lots of little Al objects.

Good times.

 

[tradergordo]

Thanks for the comments. I'm trying to do about the most basic thing you probably can do with molten metal - just trying to fill a gap. I'm building a giant steam pasteurization chamber out of a steel drum - but like most drums, it has a lip on the bottom, I want the bottom to be flat - so the first thing that came to mind was to just pour molten aluminum in there to produce a nice flat surface that also acts as an excellent heat sync. It doesn't have to look pretty, or even be very pure. If I was going to heat the pasteurizer with propane when actually using it to pasteurize, I wouldn't want the aluminum there because it would melt, but I actually intend to put the finished product right on top of my woodstove to heat it (like a giant pressure cooker). This is another idea I could find no one else on the internet saying they've tried before...

Harbor Freight has those propane torches for melting ice and flame weeding:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=91033

Maybe I could just directly melt the aluminum using one of those, without even using a crucible at all? I have no idea, I've never played around with this stuff. It says it gets to 3000 degrees. I guess for $17 its worth a try, can always use it for weeding

 

[madrone]

Harbor Freight has those propane torches for melting ice and flame weeding:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=91033

Maybe I could just directly melt the aluminum using one of those, without even using a crucible at all? I have no idea, I've never played around with this stuff. It says it gets to 3000 degrees. I guess for $17 its worth a try, can always use it for weeding

That's the one! It'll work just fine. It will be easier to do in some kind of container. I like the cast iron pot idea. Those are cheap in any thrift store.

 

[Corey]

Though it is an interesting project, I think I see what you're after, but I don't think this method is going to work.

First, it's hard to get a pot of water to boil on a stove...sure, the stove top is hot, but not real hot compared to a glowing orange electric burner or blue-hot gas flame. Secondly, building a heat sink in this way isn't going to gain much, if anything for thermal transfer. For good transfer, you need smooth polished mating surfaces, pure metal, and ideally a thermal transfer compound, aka 'heat sink grease'. Your cast metal is going to be full of porosity, it's going to have a rough surface where it meets the stove (the stove surface itself is pretty rough in the thermal transfer sense) and the casting going to shrink when it cools, so it's not going to mate to the drum end either. With all the air space between the drum, stove, and in the metal itself, it's probably going to be more of an insulator than a heat sink.

If you're set to burn wood for this project, I would make a stand to hold the drum ~16-18 inches off the ground and build a wood fire under it. Or you could get really fancy with some refractory brick and build a little chamber to help trap more heat. If you can stand propane, you might be able to use a gas burner a'la deep fried turkey set-up.

 

[polaris]

I cast lead alloy to mold pour for conicals in 54.,58,and 72 calibers a couple of times a year in the Vogelzang "box of death" stove and that's scary enough for me even in an unfinished cabin.
Joe

 

[tradergordo]

Yea, you might be right. I have used the woodstove before to run a small pressure cooker - but it can take a long time to get that water boiling. But I'm not actually trying to pressure cook with this drum. I wanted to take advantage of super low cost (free) heat, but I suppose there are other ways to do that (waste oil for example) that would let me move the operation outdoors where I can do it year round anyway instead of only in the winter with the stove. The nice thing about using the woodstove is that I don't really have to do anything extra, just put the drum on top, light a big fire, and let it sit overnight. It would be a huge hassle to light a fire outdoors under the pasteurizer using wood every time I needed to pasteurize, and it would go cold in a fraction of the time compared to the woodstove. It doesn't have to get very hot inside the pasteurizer, just 160 degrees, its the time factor that is more important (8 hours at 160 is perfect). The more I think about it, the more the woodstove seems perfect for this application. But not being able to use it year round is probably not good. I guess another option would be to run a natural gas line outside the house and just use a burner outside when the woodstove is not being used - that should be cheaper than using propane and I wouldn't have to worry about running out or refilling.

Though it is an interesting project, I think I see what you're after, but I don't think this method is going to work.

First, it's hard to get a pot of water to boil on a stove...sure, the stove top is hot, but not real hot compared to a glowing orange electric burner or blue-hot gas flame. Secondly, building a heat sink in this way isn't going to gain much, if anything for thermal transfer. For good transfer, you need smooth polished mating surfaces, pure metal, and ideally a thermal transfer compound, aka 'heat sink grease'. Your cast metal is going to be full of porosity, it's going to have a rough surface where it meets the stove (the stove surface itself is pretty rough in the thermal transfer sense) and the casting going to shrink when it cools, so it's not going to mate to the drum end either. With all the air space between the drum, stove, and in the metal itself, it's probably going to be more of an insulator than a heat sink.

If you're set to burn wood for this project, I would make a stand to hold the drum ~16-18 inches off the ground and build a wood fire under it. Or you could get really fancy with some refractory brick and build a little chamber to help trap more heat. If you can stand propane, you might be able to use a gas burner a'la deep fried turkey set-up.