The data obtained from 84 heats carried out in a 90-t top blown basic oxyge
n converter were used to study the effects of slag composition and temperat
ure on the activity coefficient and activity of manganous oxide in the slag
as well as on the manganate capacity and the manganese distribution betwee
n slag and metal. In addition, the dependence of manganese activity in the
metal on the concentration of maganese and temperature was also investigate
d.
The present study carried out in wide ranges of temperature, 1350-1690 degr
ees C, and slag basicity expressed as (CaO)/(SiO2), 1.4-10.6, clarifies the
dependence of MnO activity coefficient mainly on temperature. The activity
coefficient of MnO increases by decreasing the temperature. On the other h
and, activity of MnO increases by increasing MnO concentration and temperat
ure. Both activity coefficient and activity of MnO in the slag slightly inc
rease by increasing the slag basicity. At constant temperature, the activit
y of Mn in the molten metal varies linearly with Mn concentration and tends
also to increase with increasing temperature at constant Mn concentration.
The increase in manganese activity by increasing Mn concentration is much
steeper at high temperatures. The manganate capacity as well as manganese d
istribution ratio decrease with increasing temperature at constant basicity
and tend also to slightly decrease with increasing slag basicity at consta
nt temperature. Equations describing the parameters affecting activity coef
ficient and activity of manganous oxide in the slag, manganese activity in
the metal, manganate capacity and manganese distribution ratio have been de
rived.