A ferrous burden loses its permeability in the cohesive zone of a Blast Furnace (BF) which has an effect on the flowof reducing gases. The loss of permeability is caused by a melt onset and deformation of the solid phases due tothe pressure of the burden. Iron ore pellets with various chemical compositions have different softening properties.Due to the occurrence of numerous simultaneous phenomena the clarification of different variables is difficult. Inthis study the effect of Reduction Degree (RD) on the softening behavior of individual acid and olivine fluxed ironore pellets was experimentally tested under inert conditions. The acid pellet softened rapidly at 1150°C andreached about 40 % contraction at 1200°C. The olivine fluxed pellet softened gradually in the range of 1150 and1350°C and reached 30-35 % contraction. The RDs of 50-70 % for acid and 50-65 % for olivine fluxed pellet had nosignificant effect on the softening behavior. However, the highest contraction-% was reached with the lowest RD.The results indicate that softening of the pellets is caused by the softening of the pellet core. The early softening ofthe acid pellet was attributed to high SiO2 content and formation of fayalite slag with high wüstite solubility. Thesuperior properties of the olivine fluxed pellet were attributed to the low SiO2 content and favorable effects of fluxesto prevent wüstite dissolution. FactSage V6.4 -software and its FToxid-database was used to compute the phaseequilibrium of a pre-reduced pellet with a quaternary FeO-SiO2-CaO-MgO system in the core region. The computedphase equilibrium provided additional information about the effects of different components in the phaseequilibrium.
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