crucible seasoning

Ok, newbie casting question, I read somewhere that you need to season the
crucibles before melting metals in them. Anyone know if this is fact or
fiction? Thanks in advace. T
Reply to
TomNBanderaTx
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Absolutely true. I've used SiC and clay/graphite crucibles before, both outgas some stinky concoction for a while. The SiC smelled worse for longer. I would presume if you heat it too fast, these resins (or whatever they are) could build pressure and crack the crucible. Also, being ceramic, you should be gentle to them in general. Don't do anything that'll put a big temperature difference across it - adding liquid much hotter or cooler than the crucible's temp, etc.
Modern crucibles can take a lot more punishment than plain 'ol clay.
Anyways, the usual recommendation is to heat the crucible slowly over a period of at least a few minutes to an hour or longer, to about red heat. Just go slowly. I'm not aware of any benefit of doing this alone, i.e. annealing, cooling and then using normally.
Tim
-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @
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Reply to
Tim Williams
I used both silicon carbide and graphite clay crucibles for years. It's important to "season" the graphite/clay type if you don't want it to crack. The idea is to expel any residual moisture it has accumulated, assuming it's been stored on damp concrete, or in a moist environment. Silicon carbide crucibles don't require it and I've never had one fail by putting it directly in service by melting in it.
To season your graphite/clay crucibles, all you have to do is place them where it's warm and dry before putting them in service. It's not a bad idea to place it on the cover of your furnace when it's in operation, avoiding the vent hole. It that's not possible, and your furnace runs quite warm around the perimeter, place it near, sitting on a fire brick that is known to be dry. Make sure you get it up to the boiling point for a while before putting it in service. By doing that, you should avoid cracking.
Harold
Reply to
Harold Vordos
SiC no, Clay graphite yes it does need to be seasoned, or more properly heated before to rid it of any built up moisture. I always place my crucibles be it SiC or CG or steel pipe on top of my furnace for a bvit to heat them up and drive off any moisture......
Another thing you need to do is place a small piece of cardboard under the crucible bottom (between furnace bottom or plinth block and crucible. This will turn to carbon, and prevent a SiC type crucibnle from sticking to the plinth blocks etc. Just a small piece of cardboard from like a shoe box etc will work fine........and it does not hurt the melt.
Nothing like having a SiC crucible stock to a plinth block.
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Reply to
Roy
snip------
I used that trick for years when melting precious metals. Because flux was used in abundance, it was common for the crucible rest to be quite sticky. The carbonized cardboard prevented sticking perfectly. Soap boxes are an excellent source because they're quire large. It was my practice to soak the piece in water just before placing it on the rest if I did repeat melts with the furnace. It prevented the cardboard from instantly igniting.
Harold
Reply to
Harold and Susan Vordos
Ha! I've done many melts where the plinth felt like coming along for the ride.... oops!
Tim
-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @
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Reply to
Tim Williams

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