Author Topic: Crucible for melting aluminum over a fire  (Read 1052 times)

Loren Ver

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Crucible for melting aluminum over a fire
« on: April 08, 2018, 04:16:30 PM »
Hello,
I am looking at buying DH a crucible for his upcoming birthday.  He has been talking about melting aluminum in our fire pit for months.  There isn't a master plan involved as to what to make, he just wants to melt down some cans and other aluminum bits and make a block. If history serves, once he starts doing this, he will start making all kinds of amazing things.   

So I have started the process of finding a reasonably priced crucible, but this is not my area of expertise.  From searching around, I know the fire can be around 1100C, maybe more (?).  More searching has led me to clay graphite crucibles, but those all read "kiln" and/or "furnace" and if they give a heat rating its around 850C - 1600C.  There also seem to be sizes specifically for soda cans (which are easy to find and free).

Is this what I should be looking at? Can these go in a fire?  I really want to get the right thing for very obvious reasons (melting metal...). 

Someone with more practical experience and knowledge that is willing to share would be much appreciated.

Thank you!

Loren

px4shooter

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Re: Crucible for melting aluminum over a fire
« Reply #1 on: April 08, 2018, 08:27:29 PM »
1200 F or slightly more is the melting point. How much are you looking to spend? With the low melting point, there are a ton of DIY type of ones out there. Making the kiln isn't that hard and you can use the propane torches for heating.

We made one with the steel water bucket from Home Depot as the mold. Made the clay inside and then a lid.

CupcakeGuru

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Re: Crucible for melting aluminum over a fire
« Reply #2 on: April 09, 2018, 04:55:58 AM »
My daughter and I made a metal foundry out of a steel bucket and some plaster. I did buy an actual crucible, I think it was a 4kg graphite crucible and it was around $20-$25. It is big enough to fit the whole can and has held up nicely. We also made a battery operated foam cutter which allowed DD to cut things out and use the melted aluminum to make awesome shapes etc.

There is a guy on youtube called King of Random that has some fun videos on how to make the foundry as well as other cool projects. We have had a blast making these things. I hope your son enjoys it!

Loren Ver

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Re: Crucible for melting aluminum over a fire
« Reply #3 on: April 09, 2018, 06:09:10 AM »
You two are awesome!  I really like the DYI!

I was looking in the $30 ish dollar range.  We tried using a cast iron pan he found at goodwill, but the surface area was really high and we couldn't get it hot enough in the fire to melt the cans consistently.   

We don't currently have a propane torch but maybe that and a smaller pan could work.  Then we could work with different sized objects we find.

Think think think.

SwordGuy

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Re: Crucible for melting aluminum over a fire
« Reply #4 on: April 09, 2018, 06:51:40 AM »
Lots of damn good books at this site, including Making Crucibles.

http://gingerybookstore.com/

Great series of books on making your own metal shop tools from scratch.  Working with fire that way is definitely in my FIRE plans...

SwordGuy

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Re: Crucible for melting aluminum over a fire
« Reply #5 on: April 09, 2018, 07:08:27 AM »
Also here:

https://www.youroldtimebookstore.com/


Individual book descriptions are a hoot to read.

ncornilsen

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Re: Crucible for melting aluminum over a fire
« Reply #6 on: April 09, 2018, 07:50:59 AM »
I build one using an old propane tank, a purpose made refractory cement, and Kaowool. You can buy crucibles for this use on Amazon, or spend some time on a metal casting forum to find the best deals.

Note that steel will dissolve in melted aluminum. Weirdest thing but a cast iron pot won't last long.

Note:
Pop cans are a terrible source of aluminum - the alloy is wrong, and since it's so thin, you oxideize so much of the surface you loose alot of metal. You also need to avoid wrought aluminum - 6061 stock, swaure bars, etc. These alloys don't cast well.

The best source for aluminum to cast, is formerly cast aluminum.
Go to a junkyard - intake manifolds, aluminum wheels, etc are great sources for raw metal.

Loren Ver

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Re: Crucible for melting aluminum over a fire
« Reply #7 on: April 09, 2018, 08:11:58 AM »
Wow, I'm learning quite a lot just being there.  Thank you. 


ditheca

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Re: Crucible for melting aluminum over a fire
« Reply #8 on: April 09, 2018, 03:08:41 PM »
How to make a mini metal foundry:

https://www.youtube.com/watch?v=hHD10DjxM1g

Same channel also has some ideas for experiments to try once you have one.  Using styrofoam and sand to cast molten aluminum is pretty slick!

Loren Ver

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Re: Crucible for melting aluminum over a fire
« Reply #9 on: April 09, 2018, 03:20:08 PM »
Wow!  Thank you for the link!

tralfamadorian

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Re: Crucible for melting aluminum over a fire
« Reply #10 on: April 11, 2018, 06:47:27 AM »
Variety of crucibles in your price range on rio grande (jeweler's supply) such as this:
https://www.riogrande.com/product/clay-silica-melting-crucible-and-handle-11-ozt/704119

GreenEggs

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Re: Crucible for melting aluminum over a fire
« Reply #11 on: May 19, 2018, 03:47:57 PM »
If you want to just melt aluminum one time you can use a steel can for a single melt.  I've used an old coffee can.  You can probably use a ceramic mug for a few melts. 
I only needed a simple part that was only about the size of a medium size ashtray.

Assay crucibles are pretty cheap and made for melting metal.  They are available in a variety of shapes & capacities.  I'm not sure what types of metals graphite crucibles are used for, but I think ceramic is what is used in aluminum foundries.  I'm a glassblower and we use ceramic for melting glass.  There are a variety of ceramic formulas, and different ones are better for melting certain materials.

I'd just use an old soup can or coffee can first.  I'd also stop by a scrap yard and buy some cast aluminum scrap, because it's an alloy that was formulated for casting.  Get small chunks, so they'll fit in the can and also so it will melt quicker.  They scrap yards have big hydraulic shears & crunching tools that break it up easily. 

If your husband likes melting stuff he can learn a lot on Youtube.  DIY propane burners and furnaces are cheap and simple to make.