The effect of B2O3 on dephosphorization of molten steel by FeOx-CaO-MgOsatd. -SiO2 slags at 1873 K

Abstract

Reducing the exhaust amount of steelmaking slag is strongly required because of the view point of environmental conscious. CaO is often used for steelmaking slag but its high melting point prevents from reuse of slag as resources because free-CaO exists in the melt. Therefore highly dissolution of CaO is the key for reducing steelmaking slag. It was reported that B 2O3 accelerates CaO dissolution into slag, however, few study about B2O3 containing slag has been conducted. The present work measured phosphorus partition ratio between liquid iron and MgO saturated FeOx-CaO-MgOsatd.-SiO2-B 2O3 melts or MgO and CaO doubly saturated FeO x-CaOsatd.-MgOsatd.-SiO2-B 2O3 melts at 1 873 K. If SiO2 was replaced by B2O3, phosphorus partition ratio does not change. The maximum phosphate capacity is 1019.06 for MgO and CaO doubly saturated FeOx-CaOsatd.-MgOsatd.-B 2O3 system. The activity coefficient of PO2.5 is calculated as a function of CaO content and following equation is derived for present experimental conditions. logγPO2.5 =-6.2-0.046×(mass%CaO). © 2005 ISIJ.