Investigation of the Effects of Al₂O₃ Content and Cooling Rate on Crystallization in Fe₂O₃–CaO–Al₂O₃ System Using In Situ Confocal Laser Scanning Microscopy

Abstract

Sinter is a major Fe source, that is, used extensively in blast furnace processes worldwide. The chemical and physical properties of sinter are crucial factors that affect the operating stability of blast furnaces. The quality of sinter is largely determined by the phase fraction of the silico-ferrite of calcium and aluminum (SFCA), which is a low-melting-point bonding phase formed during sintering. Calcium ferrite (CF)-containing alumina is known to be the structural basis for SFCA and SFCA-1, and provides basic information regarding the influence of Al 2 O 3 on the formation of CF solid solutions. In this work, experiments are conducted to investigate the crystallization behaviors of an Fe 2 O 3 -CaO-Al 2 O 3 system based on its Al 2 O 3 content and cooling rate. The effects of Al 2 O 3 additions are used to analyze changes in the phase formation temperature, phase ratio, and rate of decrease by using an in situ confocal laser-scanning microscope, optical microscope, electron probe micro analyzer, and horizontal tube furnace. The temperatures at which the primary phase forms for various Al 2 O 3 contents and cooling rates differ from the equilibrium temperatures, and the phase-formation temperature ranges vary with the cooling rate.

Influence of Al2O3 Content and Cooling Rate on Crystallization in Fe2O3–CaO–SiO2–Al2O3 Systems

“…The mixed powders of each composition were homogenized by pre-melting in a muffle furnace at 1773 K for 12 h in a N 2 atmosphere. Previous studies suggest that the equilibrium state of the molten slag can be achieved by using a holding time of more than 2 h [26][27][28]. Therefore, having being subjected to holding times of 12 h at 1773 K, the premelted slags used in this study were at equilibrium.…”

Distinct Difference in High-temperature Characteristics between Limonitic Nickel Laterite and Ordinary Limonite

“…[30][31][32] The formation characteristics of SFCA is mainly dominated by the factors such as the chemical compositions of iron ores, sinter basicity, gas atmosphere and cooling rate. [33][34][35][36][37] Normally, the higher sinter basicity, iron grade and SiO 2 content of iron ores and oxygen partial pressure contribute to the formation of SFCA while the excessive Al 2 O 3 and MgO contents of iron ores and overquick cooling rate during sintering are adverse to the formation of SFCA. In general, SFCA can be divided into two types on the basis of the composition, morphology and crystal structure, i.e.…”

Effect of Bonding Area Formation During Sintering on the Reaction Characteristics of Iron Ores

“…[ 1–3 ] The typical properties of sintered ore mainly include the reducibility, mechanical strength, and reduction degradation, which are influenced most by its composition and structure of the bonding phases during heating and cooling in the sinter process. [ 4–10 ] Thus, improving the sintered ore quality should be fundamentally based on understanding the properties of raw materials, especially in terms of the mineralogical characteristics of iron ores. [ 11,12 ]…”