THERMODYNAMIC PRECONDITIONS OF ALLOYING EFFECT WHEN MODIFYING LOW-CHROMIC CAST IRON

Abstract

It is studied the thermodynamic aspects of alloying effects during the treatment the low сhromium (3 − 5 % Cr) cast iron with Fe−Si−Mg inoculants. This effect is displayed at transformation of phase at cast iron structure. Instead ledeburite eutectic with cementite carbides Fe3C and (Fe, Cr) 3C the eutectic with carbide (Cr, Fe)7C3 is formed. Such carbide usually is formed at Chromium content no less 8 – 9 %. It is showed, what it caused the quasi-equilibrium state of cast iron during of it treatment with inoculants. On one side, the melt is the non equilibrium, because of into it presence the many microzones with higher content of Si and Mg. But on the other side the melt state at the microzones can to consider as quasi-equilibrium. In that microzones because of high carbon activity are created the conditions for carbide (Cr, Fe)7C3 forming. Such possibility it is confirmed by thermodynamic calculations. The application of the exposed effect is cause without the significantly expense to provide the substantial increasing of cast iron properties.