Graphite Electrode - Foundry

How often do you have to renew the electrodes? This might give a hint...of whether any carbon is moving from them into the iron.

actually we charge the graphite electrode block together with foundry coke, cast iron scrap, limestone, ferrosilicon and ferromanganese. but after the melt we have no trace of the graphite electrode and analyzing the carbon content of the liquid metal we found out that the carbon did not pick-up significantly, that is why i wonder how carbon can be picked up by the molten metal in a cupola furnace, does is melt? or what other reaction could possibly occur inside.

I am not familiar with suppliers of these electrodes. Maybe a Google on "arc furnace supplies" might turn up a few hits?

This may happen due to electro-migration and diffusion, some of the graphite atom may moves in to melt,

Diffusion can be observed by putting a solid rod of mild steel in aluminium melt.You can observe significant erosion of rod in day of or two. Thats why ordinary cast iron crucibles are not recommended for electrical grade pressure die casting.

No, the carbon electrode is not hot enough to melt. It it, however, soluble in molten iron. Approximately how much carbon dissolves into the iron can be determined, as stated above, by measuring how quickly the electrode disappears. Theree will be a little converted to CO₂

does this mean that carbon in the electrode maybe recovered by the metal thru diffusion upon contact with liquid metal, and a little chance to react the carbon in the electrode with oxygen to form CO2 and then the CO2 gas will touch the metal surface and absorb carbon from the gas?

I was wondering if it is possible that the carbon in graphite electrode will react to the silicon in ferrosilicon to form silicon carbide (SiC) and this material will be deposited / absorbed in the metal.