1982 Volume 68 Issue 10 Pages 1513-1522
The mechanism of the degradation of agglomerates during the reduction was studied for experi-mentally made pellets and the change in mineral phases by some oxides, affecting the degradability, was examined quantitatively by the synthetic system of chemical reagents.
The results obtained are summarized as follows:
(1) The microscopic observation suggests that cracking occurs at skeletal hematite and calcium ferrite phases. By the analysis of line-broadening measurements of X-ray diffraction, no strain is detected in both bulky and skeletal hematites regardless of the solution of alumina. Micropores are generated in magnetite reduced from hematite to bring stress for the reduction at low temperatures and stress concentrations are considered to occur around inclusions of small radius of curvature to cause cracking of skeletal hematite grains.
(2) Quarternary calcium ferrite is reduced to metallic iron in the blast furnace through dicalcium ferrite or wustite. Nonferrous oxides form gehlenite and β-dicalcium silicate.
(3) The amount of skeletal hematite depends mainly on the degree of supersaturation of iron ions in slag and the dissociation temperature of hematite. This is influenced by nonferrous oxides such as MgO, Al2O3, and TiO2.