Determination of Al 2 O 3 Activity by Reference Slag Method in CaO–SiO 2 –Al 2 O 3 –MgO Melts for Blast Furnace Slag with High Al 2 O 3 at 1873 K

With the increase in using high Al 2 O 3 iron ore, the content of Al 2 O 3 in blast furnace slag has increased sharply in recent years. Thus, the activity of high Al 2 O 3 slag in the blast furnace slag system needs further study. Herein, the activity of Al 2 O 3 ( a ( Al 2 O 3 )) in CaO–SiO 2 –Al 2 O 3 –MgO slag equilibrated with molten Cu at 1873 K is determined by applying the reference slag method. Isoactivity contours for Al 2 O 3 in the (CaO + MgO)–SiO 2 –Al 2 O 3 pseudoternary system are achieved for blast furnace slag, and the effects of R (mass% CaO/mass% SiO 2 ) and MgO/Al 2 O 3 on the activity of Al 2 O 3 are discussed. When Al 2 O 3  = 20 wt% and MgO/Al 2 O 3  = 0.4, with R increasing from 1.10 to 1.30, the activity of Al 2 O 3 decreases from 0.0423 to 0.0244. When Al 2 O 3  = 20 wt% and R  = 1.25, with MgO/Al 2 O 3 increasing from 0.35 to 0.55, the activity of Al 2 O 3 decreases from 0.0470 to 0.0366. The reference slag method, herein, is feasible based on the experimental results and the reference slag method is simple, reasonable, and of high accuracy.