crucible for copper and aluminum casting

[happycat]

I think I'm in the wrong place. Can someone point me in the right direction?

When casting in sand with copper or aluminum how do I chose a crucible? I can figure out what size I need but what about the composition? What is the difference between cheap and expensive crucibles? What is the difference between the first three clay graphite ones (links are below)? I see a difference in the shapes but i do not know what that translates into. And finally what is the difference between the first three clay graphite crucibles and the last one a Silicon Carbide crucible. Will there be a noticeable difference or advantage between the clay graphite and the Silicon Carbide?

On one hand I want to buy the cheapest one but I also understand " you get what you pay for"

The crucible will be used in either a charcoal or gas furnace that I will build in the next 2 weeks or so.

Thank you for your reply,


ceramic bonded clay graphite crucible
http://www.lmine.com/mm5/merchant.mvc?S ... Code=17392

Budget graphite
http://www.lmine.com/mm5/merchant.mvc?S ... t_graphite

Premium graphite
http://www.lmine.com/mm5/merchant.mvc?S ... t_graphite


Silicon Carbide Crucible
http://www.lmine.com/mm5/merchant.mvc?S ... _crucibles

 

[fireguy]

This question might be better in the "refining" forum.

Any of those crucibles should work OK for your material. Choosing a proper flux is always important both to remove impurities and to lower melting temperature and make the pour more fluid.

The silicon carbide crucibles will last much longer than the less expensive graphite. However, I would start out with the lower priced crucibles so you get some experience. Monitor any "cracking" or erosion to the crucible wall. You don't want to use the crucible so many times that you burn a hole. This will make a mess.

Be sure and have some "furnace bedding" in the bottom of the furnace to soak up a spill just in case:

http://www.lmine.com/category/furnace_bedding.html