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I Need to know what to use for a crucible Answered

Hello and thanks for taking the time to help me. i need to know what to make a good crucible out of. Also can i use a soup can or tomato can to do this? (it's an aluminum foundry)

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Josehf Murchison
Josehf Murchison

5 years ago

When I worked in a Foundry the crucible they used was made out of a steel pot. So I would use a steel or cast iron pot.

Melting points

Steel 2500 to 2800 degrees f

Iron 2060 to 2360 degrees f

Aluminum 1218 degrees f

Steel or Cast Iron will get a little red but it will hold.

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Toga_Dan
Toga_Dan

5 years ago

army surplus store near me has stuff for gold panning. this includes little ceramic crucibles, about 3 inch dia. $3 to $6. gold melts hotter than Al, iirc. so Al should be ok in it.

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gmoon
gmoon

Reply 6 years ago

Link doesn't seem to work...

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blkhawk
blkhawk

Reply 6 years ago

Copy and paste the following link: http://www.amazon.com/Making-Crucibles-Vincent-R-Gingery/dp/1878087274/ref=pd_ys_sf_s_283155_b4_1_p?ie=UTF8&refRID=1235ZX257P6E8VEJ8SDK

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gmoon
gmoon

Reply 6 years ago

Yep, that works, thanks. I've had issues with linking here too (especially two links in one paragraph).

RE: crucibles--I have five, from my father-in-law: two cast iron, three steel. Used, I think, for old-school lead plumbing packing (one still partly filled with lead). But I'd like to try casting Zamak alloy, and that's contaminated by iron...

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Downunder35m
Downunder35m

6 years ago

I am trying to make a small size arc furnace mainly for aluminium.

Getting fire bricks here is a pain in the ....

Fire proof cement would be an option as it is rated for around 1000-1400° Celsius depending on the type of concrete.

Downside is that the firing temps often exeeds those limits.

To overcome this problem I am now seeking alternative building materials from the old days.

Clay I don't really like as, at least in my tests it tends to crack too easy.

Currently I have a new recipe curing:

Normal plaster mix with some extreme heat resistant additions to keep it together with changing temps as well as providing good insulation.

If any of the recipies turn out working fine I will make a short Instructable for it.

I just guess but if it survives a few thausand degrees in an arc furnace it should be good enough for crucible too, at least for low temp metals as aluminium.

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Downunder35m
Downunder35m

Reply 6 years ago

Ok, forget the plaster mix.
It does take quite much to get this mix to melt in the arc but it does expand too much under heat causing cracks to form.
For a cheap alternative check your nearest refractory and get some light weight fire bricks.
You can cut them with a knife or saw and they handle temp of up to 1200° celsius with no problem.
An no, molten metal does not stick to it.

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Di Immortales
Di Immortales

6 years ago

thanks for that idea. but how do i safely empty and cut them open

-Di Immortales

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Downunder35m
Downunder35m

Reply 6 years ago

The Coleman type cylinders have a valve in the top.

Once the gas has been used (cooker, gas lantern...) I use a thin metal pin or srewdriver to let any excess gas out.

For the cutting you can use a thin blade on an angle grinder or a hacksaw.

It is quite soft steel, so not hard to cut.

In case you want to be 100% safe with any gas left in the can:

Drill two holes in the top at low speed and fill the entire canister with water - this will remove any traces of the gas, after that empty and cut.

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Downunder35m
Downunder35m

6 years ago

I prefer the cut open canisters for camping gas, you know the sturdy ones like Coleman.

Cut the top off, make a little dint to pour and you are done.

They last much longer than thin tin cans.

You can also use ceramic or clay if your prefer.

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Di Immortales
Di Immortales

6 years ago

And by soup can I mean what people call "tin cans" but they're actually made of steel