Temperature failure rating on certain materials:
I'd like to get failure temps for certain materials; IE, how hot something can get before cracking, exploding, ect. when molten metal is poured on/into it.
Would any of these last as a mould if you dumped hot lead, aluminium, bismuth and the like into them.
Hardened and cured plaster casts.
Quickrete.
Concrete.
Cement.
Ceramic mould.
Would any of these last as a mould if you dumped hot lead, aluminium, bismuth and the like into them.
Hardened and cured plaster casts.
Quickrete.
Concrete.
Cement.
Ceramic mould.
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Mar 29, 2010. 10:22 AMMillenniumMan (author)
says:
Ok, then a paper mache' positive inside the sandcast mould?
Obviously, the thing would catch fire and whatnot, but what would that do to the mould and the end product?
Obviously, the thing would catch fire and whatnot, but what would that do to the mould and the end product?
Lead in plaster (well dried) would work the once, probably not much more than once though.
I'm not sure about the rest - what sort of things are you wanting to cast in which metal?
L
I'm not sure about the rest - what sort of things are you wanting to cast in which metal?
L
Mar 17, 2010. 12:42 PMMillenniumMan (author)
says:
Looking to cast aluminium plates (2" thick) and customized parts. As well as use bismuth for its ablative properties.
I thought about sandcasting, but those moulds are temporary and I need to be able to reproduce replacement parts from time to time (IE highly extreme impacts)
I thought about sandcasting, but those moulds are temporary and I need to be able to reproduce replacement parts from time to time (IE highly extreme impacts)
If you're casting that much metal, you should go with ork'.
L
L
Mar 17, 2010. 1:54 PMorksecurity
says:
When sandcasting, you're making the sand mold from a positive. The mold is single-use, but the positive is reused as many times as necessary. Keeping it on file is no harder than keeping a mold on file.
I'd pitch all of 'em and use sand. Sand doesn't usually explode.
Mar 17, 2010. 2:48 PMBurf
says:
I would advise against Portland cement based materials. They are all hygroscopic in nature and the high heat of molten metals will turn the water into steam and cause the concrete to spall. A ceramic mold however, should work fine.
Mar 17, 2010. 2:43 PMRe-design
says:
One thing you must do whatever material you use for your mold is make sure that it is absolutely dry.
The melting temp of aluminum is 1250 f. or so and any water trapped in the mold will be instantly and violently turned into steam and your mold and molten metal will be turned into shrapnel.
The melting temp of aluminum is 1250 f. or so and any water trapped in the mold will be instantly and violently turned into steam and your mold and molten metal will be turned into shrapnel.
With composites and amorphous solids (all of the above), absolute temperature is less of an issue for failure as differential temperature. These materials do not conduct heat well, so if you pour hot metal onto them you have very localized heating, while the rest of the material stays cool(er). So you get differential expansion, and consequent fracture.
If you reduce the temperature differences, for example, by heating the mold itself slowly up to the work temperature, then you can avoid that problem. You'll probably want to use refractory cement for such an application, for stability.
If you reduce the temperature differences, for example, by heating the mold itself slowly up to the work temperature, then you can avoid that problem. You'll probably want to use refractory cement for such an application, for stability.
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