Clay molds for aluminum casting?

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dorin
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Clay molds for aluminum casting?

Postby dorin » Sun Feb 26, 2017 2:01 pm

Suppose you made a mold from clay and fired it in a kiln...would you be able to successfully pour aluminum into it, or would the kiln firing deform the mold?
(Or are there other problems I am not even thinking of?)
Thank you,
MIke

OddDuck
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Re: Clay molds for aluminum casting?

Postby OddDuck » Sun Feb 26, 2017 4:21 pm

Shrinkage would be a major concern. This is done, by the way, with lost wax, aka investment casting. These are one-shot deals, too. The mold is destroyed to remove the casting. If you are talking about a permanent or semi permanent mold thermal shock would be the biggest problem. When you poured the metal in, unless the mold was heated to near pour temp it could potentially crack.
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

jscarmozza
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Re: Clay molds for aluminum casting?

Postby jscarmozza » Mon Feb 27, 2017 6:11 pm

Have you thought about molding your pattern in core material rather than green sand? I've had some success doing that, but you'll get the sand cast, not the smooth invest cast finish.

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steamin10
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Re: Clay molds for aluminum casting?

Postby steamin10 » Mon Feb 27, 2017 10:16 pm

Not so! Using a hardening core mold can, and then giving it a wash of clay (slip) or even sugar and starch as a wash, will refine the surface. It will also make the sand tighter, which may effect the gas off during a pour, but change the finish.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
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dorin
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Re: Clay molds for aluminum casting?

Postby dorin » Tue Feb 28, 2017 7:29 am

I have not thought of core material.
The only success I have had is with kinetic sand, but it gets a little pricey.
It does leave a pattern..but not too bad.

Could not find an image of the original casting, but here it is cleaned up a bit.

Starting to think of spring and trying again. Our last poor was too late in the year...a cold day with a cold wind.
The aluminum solidified in the crucible...or at least starting too...giving us ugly results.

-MIke
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jscarmozza
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Re: Clay molds for aluminum casting?

Postby jscarmozza » Tue Feb 28, 2017 9:07 am

Right again Big Dave, I forgot how well the finish was on the sprues and runners when I applied the core wash when pouring the cab roof. They had a better finish than the casting! Dorin, check out the advice Big Dave and OddDuck give on making cores in the pouring thin sections post. John


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