Oxygen activities in Cr‐containing Fe and Ni‐based melts

Plug‐type, ZrO 2 ‐based oxygen sensors have been used for long‐term measurements of oxygen activity in Fe–O–Cr and Ni–O–Cr melts. In these melts, equilibrated with chromium oxide, oxygen activities a O were determined as a function of Cr content. From the experimental results, data were derived for activity coefficients f O and of 1st and 2nd order interaction parameters e O Cr and r O Cr . Cr 2 O 3 has been identified as the oxide phase in equilibrium with the metal melt at ≥ 5 wt.% Cr in the case of iron and at ≥ 0.2 wt.% Cr in the case of nickel. Oxygen activities and oxygen contents in Cr‐containing iron melts are lowered with increasing additions of nickel. Further investigations were directed to a O determination in Fe–O–Cr–C and Fe–O–Cr–Al melts.