Abstract
The change in mineral phases during the indurating process was investigated quantitatively for industrially produced dolomite-fluxed pellets and was related to some reducing properties.
The results obtained are summarized as follows:
(1) The mineral phases of the pellets consist of hamatite, magnesioferrite-magnetite s. s., calcium ferrite and silicate slag. Calcium ferrite phase melts incongruently at about 1300°C, resulting in increase of liquid slag, and in consequence, the mineral phase bonding iron oxides changes from calcium ferrite to vitreous silicate slag. The contraction during reduction up to 1100°C, which was proved to be closely related to the actual performance of blast furnace, increases abruptly above this temperature. In order to minimize the contraction during reduction, it is important to keep induration temperature just below the decomposition temperature of calcium ferrite.
(2) The chemical composition of the calcium ferrite solid solution is proposed to be CS-C(F, A)3. It should be noted that this ferrite can solve an appreciable amount of gangue components.
X-ray precession photographs of this crystal show a c-centered monoclinic pseudo-cell with a-9.979Å, b=15.262Å, c=5.307Å, β=100.23° and a possible space group of C2/c.
