Development of Prefused Synthetic Flux for Basic Oxygen Steel Making through Micro-Pelletization and Sintering of Iron Oxide Fines Jagannath Pal,  Satadal Ghorai, Pasumarthi Venkatesh, Manik Chandra Goswami, and Debajyoti Bandyopadhyay Calcined lump lime is used as flux material in basic oxygen furnace (BOF) steel making. Due to its high melting point and poor dissolution property, slag formation takes a long time. Since, Fe 2 O 3 –CaO has eutectic melting point of 12308C at the composition of 22% CaO, material containing Fe 2 O 3 and CaO can easily melt and form basic oxidizing slag at the very beginning of the blowing to make the refining process faster. A partially prefused synthetic flux in combination of mainly CaO and Fe 2 O 3 has been prepared through micro- pelletization and sintering (MPS) of waste iron oxide fines generated in steel plant. The fines were converted to strong micropellets to make it suitable for sintering. Cold handling strength in micropellets was imperted by a novel CO 2 treatment technique at room temperature and cold compressive strength up to 9kg/pellet with a good abrasion resistance could be observed. The sintering of the developed micropellets was carried out without using coke breeze and produced sinter showed good handling strength, resistance to thermal shock and weathering, low softening temperature and thus qualifying it as a suitable alternate flux material for BOF towards fast formation of oxidizing and basic slag. 1. Introduction Steel scrap and burnt lump lime are traditionally used as coolant and flux materials, respectvely in basic oxygen steel making furnace (BOF). Iron ore is also used as coolant for its better chemical consistency and ease of availability, but suffers from poor recovery and tend to make the slag foaming. Sometimes lime stone employed as a coolant as well as a flux. Lime stone calcination is a kinetic driven process and delays dissolution when employed. On the other hand, burnt lime has high melting point (27008C), poor dissolution property, tendency of fines generation and hygroscopic nature. Since, Fe 2 O 3 –CaO has an eutectic melting point of 12308C at the composition of 22% CaO, [1] a prefused flux, containing Fe 2 O 3 and CaO can easily melt and form basic oxidizing slag at the very earliest stage of the blowing in BOF and make the refining process faster. Several investigators have used briquettes, pellets, and sinter of iron oxides in BOF as coolant as well as to increase iron oxide content in slag for faster dissolution of lump lime. Some investigators [2–9] in India, have recycled LD sludge as well as other iron oxides in BOF in form of cold bonded briquettes and reported faster refining as well as improved metallic yield. However, preparation of cold bonded briquettes require high percentage of binders and forms fines due to disintegration at high temperature. Further, these briquettes contain significant amount of moisture attached with the lime which may form hydrogen at high temperature of converter with the risk of explosion. [9] Cold bonded pellets prepared from iron oxides has also been tried by investigators [8,10] however, it also contained costly binders and took a long curing time (28 days for cement bonding). Most of these agglomerates could be used as a replacement of iron ore only but not as lime-iron oxide flux. In a study, [11] lime pellet with iron oxide coating yielded encouraging results during refining. However, difficulties encountered in coating of lime pellets restrict its large scale use. Irmler et al. [12] reported the use of fluxed sinters containing iron oxides and lime, limestone or dolomite fines to form low melting slag and found encouraging results in faster slag formation, phosphorous removal and sulfur removal. However, their making proc- ess has not been revealed in the paper. Investigators [13,14] [  ] Dr. J. Pal, S. Ghorai, P. Venkatesh, M. C. Goswami, D. Bandyopadhyay CSIR-National Metallurgical Laboratory, Jamshedpur-831007, India Email: jgpal2003@yahoo.co.in DOI: 10.1002/srin.201200324 www.steel-research.de ß 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim steel research int. 84 (2013) No. 11 1115 FULL PAPER