Taking slag-metal samples at various working periods, (i.e. before slag-off, before tap and in ladle) during melting process of stainless steel in a 30-t basic electric furnace, sulphur partition at each period was examined.
Following results were obtained:
1) The sulphur capacity
Cs, i.e. (% S) /
a [s] [%Si]
1/2 at each period was greater, the higher the molar basicity, which was defined as
N2cao/
Nsio2.
2) The sulphur capacity
Cs was increased linearly with decreasing amount of Cr
2O
3 at he constant N
2Cao/
NSio2. t
It was considered that the higher the Cr
2O
3 in slag, the smaller becomes the slag-off
Cs ven in the case when the slag indicated the same value of
Vm'-
NCao.
3) Though the effect of MgO content of slag on
Cs was rather unobvious as compared with (Cr
2O
3), it was recognized that the sulphur capacity
Cs was increased with increasing amount of MgO at the constant
N2CaO/
NSio2 and Cr
2O
3 content.
4) The sulphur capacity, except in ladle, was correlated statistically with the main slag composition as in the following equation:
Covering the temperature range 1540 to 1680°C,
log [ (%S) /
a [s] [%Si]
1/
2] =0. E867 log [
N2CaO/ (
Nsio2 +
Ncr2O3)] -0.723
5) The sulphur capacity
C'
s, i.e. (%S) (
NFeO) /
a [s] was less closely related to
N2CaO/ (
NSiO2 +
NCr2O3) than
Cs was.
6) The logarithm of sulphur capacity
Cs was increased linearly with increase of the excess base, i.e.
n CaO- (
n SiO
2+
n Cr
2O
3).
No advantage were obtained in replacing the basicity term, i.e.
N2CaO/
NSiO2+
NCr2O3, by the excess base.
7) The logarithm of (
Cs (
NSiO2+
NCr2O3) /
N2CaO) was a linear function of the reciprocal of absolute temperature.
The following equation was statistically obtained:
log (
CS (
NSiO2+
NCr2O3) /
N2CaO) = 3040/
T + 0.704.
8) The sulphur content in pit sample was increased rapidly, with increase of the value of
NFeO (
NSiO2+
NCr2O3)
N2CaO of the final slag composition, if it exceeded above 16×10
-2.
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