Influence of Bath Stirring Intensity and Top Blown Oxygen Supply Rate on the Decarburization of High Chromium Molten Iron

Abstract

A basic study was conducted on the decarburization of high chromium molten iron under top-and-bottom combined blowing condition using a small high-frequency induction furnace.
(1) Decarburization is divided into stage I (high carbon region) and stage II (low carbon region). The critical carbon concentration at transfer from stage I to stage II decreases when the oxygen supply rate is restrained or when the bath stirring intensity is increased.
(2) At stage I, when the oxygen supply rate is decreased, although the decarburization rate decreases, the Cr loss also decreases. When the bath stirring intensity is increased, the Cr loss decreases, and the decarburization rate increases. The Cr loss is determined by the balance of bath stirring intensity and oxygen supply rate from top lance.
(3) At stage II, the decarburization rate and the Cr loss are also determined in relation to the oxygen supply rate and the bath stirring intensity, but since the rate of decarburization is controlled by carbon transfer rate in the bath to the reaction zone, the Cr loss increases with the progress of decarburization.
(4) The total oxygen content in the bath during blowing becomes gradually larger than the dissolved oxygen content as [%C] decreases, and suspended oxides of composition similar to FeO·Cr₂O₃ appear in the bath correspondingly.
(5) Coarse oxide particles exist on the bath surface in the low carbon period and fine oxide particles of the FeO·Cr₂O₃ composition are observed to be dispersed into the bath from the coarse particle as the starting point.