Distribution Equilibria of Phosphorus and Sulfur between Liquid Iron and <Na_2> O Base Slags.

点击翻译按钮获取中文摘要

1. IntroductionIn order to extend a market for steel materials, it is necessary to make steels high grade. Especially, the very low-phosphorus-steel and very low-sulfur-steel are strongly in demands. Desulfurization proceeds efficiently in the process of hot metal pretreatment, which has been fixed in every steel making plant, whereas dephosphorization is carried out in converter or ladle refining furnace. The ladle refining, in the stage of final steel making processes, is considered to be an advantageous process to obtain P+S<50ppm. In the present work, the possibility of the simultaneous dephosphorization-desulfurization by the <Na_2> O-based fluxes was investigated.2. ExperimentThe experiments were carried out in a Tammann furnace (static bath, Fe-P-S alloy/ <Na_2> O-CaO- <SiO_2> flux ratio = 30g/300g) and a high frequency induction furnace (stirring bath, ratio = 100g/1200g) in an atmosphere of Ar at 1600゜C. The obtained results were discussed from the thermodynamic point of view. The relationships among slag compositions ( <Na_2> O/ <SiO_2> , <Na_2> O/CaO ratios), oxygen potential of molten steels, degrees of dephosphorization and desulfurization, <C_P> and <C_S> were made clear. The stirring effect of molten steel was also discussed.3. Results(1) The <Na_2> O/ <SiO_2> ratio of final slags varied from 0.4 to 1.1. The degrees of dephosphorization and desulfurization increased with increasing in this ratio. (2) The <Na_2> O/CaO ratio of initial fluxes was set from 4 to 2. The degree of desulfurization decreased markedly, whereas that of dephosphorization was constant at a high lebel, with decreasing in this ratio. The ability of CaO to desulfurize molten steels was lower than that of <Na_2O> . The <Na_2O> -equivalence of CaO was determined to be 0.8 for dephosphorization and 0.3 for desulfurization. (3) By the stirring of molten steel, both of dephosphorization and desulfurization improved markedly.