Abstract
Isothermal softening tests of pre-reduced sinters under a constant load were carried out in order to clarify their softening properties in terms of softening viscosity.
(1) Softening viscosity decreases with decrease in sinter size and shows a minimum at a certain prereduction degree.
(2) Softening viscosity of slag phase is smallest in the mineral phases which compose the sinter. It is suggested that formation of slag phase having high softening viscosity improves softening properties of sinter.
(3) Softening properties are improved by controlling gangue minerals, especially by increase in CaO/SiO2 ratio.
(4) Shrinkage degrees during reduction process under simulated conditions of temperatures and gas compositions in a real blast furnace are in good agreement with the values obtained by integrating the shrinkage rate based on the softening viscosity with respect to the shrinking time.
