The reduction behavior of calcium ferrite (CF) in commercial sinter in the initial stage was examined by the gravimetric method.
In a previous work, final fractional reduction, Ff, obtained in the reduction stage from hematite to magnetite at GR ≡ VCO/(VCO + VCO2) = 0.2 (V: flow rate) and EPMA, X-ray and microscopic analyses clarified that at 1003 K and more CF was reduced to magnetite but below about 1003 K CF was hardly reduced and Ff_??_0.7 when the oxygen reducible in this stage was assumed to come from hematite and Fe2O3 in CF.
In the present work, influence of both CO ratio GR and reduction temperature T upon the reducibility was studied by changing either GR or T while keeping the counterpart constant. The following "quasiequilibrium line" below which CF was not reduced was found out within the magnetite stable region in the equilibrium diagram for Fe-C-O system:
T = 1030 - 10.2GR - 801GR2 (873≅T≅1023 K)
When GR or T were decreased after CF was reduced, "re-oxidation" took place below this line. Long term reduction curve in twice as much as the period for ordinary experiments demonstrated that eight hours were long enough to judge the reducibility of CF and determine Ff.
