Assimilation Behavior of Calcium Ferrite and Calcium Diferrite with Sintered Al 2 O 3 and MgO
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I.
INTRODUCTION
THE serious overcapacity of iron and steel yield and the decrease of profit make many iron and steel enterprises to use the low-grade ores with harmful elements and gangues to reduce manufacturing cost. As a result, the use of these ores leads to the frequent fluctuation of size distribution and chemical composition of raw materials prior to the sintering strand process. Further, their use affects the liquid formation, assimilation, and solidification during the sintering process Iron ore sintering is a high-temperature physicochemical process that depends on the formation and crystallization of liquid phase to bond the ore particles. The previous studies showed that the Al2O3 and MgO contained in the raw materials have important influence on sinter properties. It was reported that the increase of Al2O3 in the iron ore can result in worse strength and sintering yield.[1–3] Large numbers of researchers[4–12] asserted that the addition of MgO can result in a deterioration of fuel rate, sintering rate, reducibility, and sinter strength, and can also lead to an increase of the first meltdown temperature. The advantages are the improvement of the reduction degradation index and softening-melting characteristics of the sinter.[13–16] On the other hand, as the main bonding phase of high-basicity sinter, the structure and assimilation properties such as wettability of calcium ferrite (CF) series slag
HONGMING LONG, Professor, XUEJIAN WU, Master Student, ZHANXIA DI, Lecturer, and TIEJUN CHUN, Associate Professor, are with the School of Metallurgical Engineering, Anhui University of Technology, Ma’anshan 243002, China. Contact e-mail: springcsu@ 126.com BIN YU, Master Student is with the School of Materials Science and Engineering, Chongqing University, Chongqing 400044, China. Manuscript submitted March 14, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
have great influence on the quality of sinter. Studies[17–20] revealed that in this process, the liquid phase CF first forms and continually spreads along solid interfaces, such as Al2O3 and MgO. During the liquid phase formation process, a certain amount of intermediate product calcium diferrite (CF2) generates in the Fe2O3 enriched region.[21–24] The CF2 has an un-negligible influence on the generation rate of CF. Therefore, the study of the assimilation behavior of CF and CF2 on sintered Al2O3 and MgO is significant in understanding the sinter process and guiding the sinter operation.
II.
EXPERIMENTAL
A. Materials Guaranteed reagents (Aladdin Industrial Co.) were used in this study. The chemical composition of the slag and the size distributions of the raw materials measured using the screen method, are listed in Tables I and II, respectively. The molar ratio of CaO/Fe2O3 was maintained as 1:1, and 1:2 in this study. CaO was replaced with equal moles of CaCO3 because the former exhibits good moisture absorbent ability. At first, 10 grams reagents were weighed, homogeneously mixed and pressed into a cylindrical pellet (/20 mm) in 10 MPa pressure. Then, the pe
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