The article describes the trend towards increased use of induction crucible furnaces for cast iron smelting. The use of gas cupola’s duplex

process – induction crucible furnace – has been proved the effective direction of scientific and technical advance in the foundry industry.

Gas cupolas and induction furnaces are used for cast iron smelting at the Penza Compressor Plant where in the 1960s the author developed

and introduced gas cupolas for the first time in the world. In the article, the author represents the findings of the investigation on

thermodynamics of crucible reduction of silicon, which is pivotal when choosing the technological mode for cast iron smelting in

induction furnaces. The author proposes a new reaction crucible diagram with due account of both partial pressure and activity of the

components involved into the process. For the first time ever, the electrochemical mechanism of a crucible reaction has been studied and

the correctness of the proposed diagram has been confirmed.