Graphite crucible and its reducing effect

[Ayham Hafez]

As I understand, cheap graphite crucible only made from graphite and binder, unlike good quality graphite crucible like Salamander which is made from graphite, carbide silicon and fire clay.

Graphite which used in graphite crucible is made from calcined coke, which itself is a reduction agent since its formula is C element, so does graphite crucible always reacts with oxides and reduce them? So metal oxides short life the crucible?

 

[Ayham Hafez]

@4metals need you're help here

Do you have any idea?

 

[snoman701]

It depends on the amount of oxides. It's all based upon surface area. The surface area of a crucible isn't as great as the surface area of a couple grams of powdered organic material that is mixed in with the melt.

Traditionally, the pure graphite crucibles are best for strictly metal melts only. No smelting.

 

[4metals]

Do you have any idea?

The only crucibles that I have had extensive experience with are clay graphite. These work well in gas furnaces and low frequency induction furnaces.

And the only melts I have done which counted on the flux entirely to reduce the charge was when melting Silver Chloride. And Silver Chloride melts seemed more efficient in clay graphite furnaces.

And a clay graphite crucible should not be confused with a pure graphite crucible. Pure graphite crucibles are used as the inner crucible in a high frequency induction furnace when the outer crucible is a ceramic composite which adds strength to the pure graphite liner.