Generally speaking, sulphur is considered a harmful element for steel quality, reason why all the technological steps are being taken in order to eliminate it from the metal bath. This paper deals ...with the influence of the chemical composition, on the slag quantity and of the bath stirring condition upon the desulphurization process in the casting ladle by treatment with synthetic slag. The experiments were made at an open-hearth plant with the steel tapping in two ladles (the desulphurization was made with synthetic slag at one ladle while the other one was considered standard) and at the electric steel plant and for the synthetic slag formation a mix was used, made, according to several receipts, of: lime (50-75%), fluorine (0-17%), bauxite (0-32%) and aluminous slag (8-22%). The data were processed in the calculation programs EXCEL and MATLAB, which resulted in a series of correlations between the desulphurization degree and the chemical composition of the slag, respectively the slag quantity both for the charges bubbled with Argon and the unbubbled ones.
To resolve the difficulty in slag formation during steelmaking with low silicon hot metal and to increase productivity, a new 5-hole lance was developed by increasing oxygen flow from 50 000 m^3/h to ...60 000 m^3/h. Synthetic slag was added to adjust the slag composition. The problems such as difficulty in dephosphorization and slag adhesion to oxygen lance and hood were settled. Steel production and metal yield were increased and the nozzle life was prolonged through these techniques.
Based on the results for the time dependence of F, Ca, Si and Al amount dissolved from hot metal pretreatment slags, the behavior of fluorine dissolution has been examined. It was found that the ...amount of fluorine dissolved from hot metal pretreatment slag depends on CaO/SiO2 mass ratio and fluorine content in slag. This trend is obvious in the case of synthetic slags. Fluorine ion in solution is incorporated into CaO-SiO2-H2O and CaO-SiO2-Al2O3-H2O gels during the formation of these gels. Therefore, it was found difficult to estimate the amount of fluorine in solution from the amount of F-containing mineral phases and slag compositions.
Ladle desulphurization of aluminium-deoxidized steel by means of a synthetic slag is an example of a mass-transfer-controlled pyrometallurgical operation. Literature data indicate that mass transfer ...of sulphur in the liquid steel is rate-determining. In this work, the rate of desulphurization in an argon-stirred ladle was calculated, incorporating literature correlations for the mass-transfer coefficient of sulphur in the liquid metal, and thermodynamic data on the activities of relevant species dissolved In the liquid steel and synthetic slag.
Herein an innovative process to develop a potential vitreous material with cementing properties is proposed. This process paves a production path through melting industrial waste and subsequently ...cooling the casting in water. The idea erases the need to reduce the environmental impact of the cement industry in terms of natural resources consumption as well as the re-utilization of abandoned wastes from other industries. The recycled industrial wastes were selected according to the amount of waste produced in the industrial field and its suitable chemical composition, such as construction and demolition waste and/or shells from shellfish. As a main result, the mechanical properties showed by our novel material were worse than those reported by blast furnace slag (25⁻28 MPa for two different proportions) for seven days and better (43⁻52 MPa for two different proportions) for 28 days. The rest of the properties evaluated were in agreement with the standards' requirements. Hence, this novel process would help to minimize the environmental impact of these wastes at the same time that their use in the cement industry would reduce the consumption of raw materials.
The simplex lattice method of planning experiments is used to study the viscosities of CaO–SiO
2
–Al
2
O
3
–8% MgO–4% B
2
O
3
slags in a wide chemical composition range. For each viscosity, we ...developed an adequate mathematical model in the form of a reduced third-order polynomial. The results of mathematical simulation are presented in composition–viscosity diagrams. Composition regions with a high fluidity of slags, the viscosities of which are 0.8–1.2 Pa s in the temperature range 1500–1600°C, are indicated in the diagrams.
High-lime synthetic slags for refining steels in the ladle–furnace unit are investigated. The content of the slag mixtures is as follows: 60 wt % CaO, 7 and 8 wt % MgO, 7–23 wt % Al
2
O
3
, and 9–18 ...wt % SiO
2
, with additions of 8 wt % CaF
3
and 5–15 wt % Na
2
O. Polymer theory is used to calculate the composition of the anionic subsystem in the slag melts. The log-mean polymerization constants
K
p
*
for multicomponent melts are calculated from the known polymerization constants in binary systems. It is found that
K
p
*
≈ 10
–3
–10
–2
in the range 1500–1600°C. In that range, the melt’s degree of polymerization is 3 × 10
–4
–8 × 10
–3
. In the most polymerized melt, the ionic content of the dimers Si
2
O
7
6-
and Al
2
O
7
8-
is no more than 0.1 and 1.5% of the values for the corresponding monomers. Therefore, we assume, with an error of about 2%, that the structural units of the anionic subsystem are monomers AlO
4
5-
and SiO
4
4-
simple O
2–
and F
–
ions (slag 7). The cationic subsystem consists of Ca
2+
, Mg
2+
, Na
+
, and Al
3+
ions in octahedral coordination with oxygen (less than 3% of all the Al atoms). In all the melts, the concentrations of free oxygen ions O
2–
and Ca
2+
ions are similar. In half the cases, the content of O
2–
ions is greater than the content of Ca
2+
ions. The mean mobility
U
and self-diffusion coefficient
D
for all the cations are calculated from data for the electrical conductivity and the density. With increase in temperature from 1500 to 1600°C,
U
and
D
increase by 50 and 60%, respectively, in all the slags. With increase in the mutual substitution of the components in the slag mixtures
M
=
n
(Na
2
O, CaF
2
)/
n
(Al
2
O
3
+ SiO
2
), mol/mol, at 1600°C,
U
increases from 1.14 × 10
–8
to 1.46 × 10
–8
m
2
/(V s) for slags 1–6 (0 ≤
M
≤ 1.1) and from 1.01 × 10
–8
to 1.66 × 10
–8
m
2
/(V s) for slags 7–10 (0.25 ≤
M
≤ 0.65). Correspondingly, D increases from 9.2 × 10
–10
to 12.8 × 10
–10
m
2
/s for slags 1–6 and from 8.2 × 10
–10
to 14.3 × 10
–10
m
2
/s for slags 7–10. The temperature dependence of
U
and
D
may be approximated by an Arrhenius equation with activation energies
E
U
and
E
D
. With increase in
M
in the given ranges,
E
U
declines from 146 to 100 kJ/mol (slags 1–6) and from 124.5 to 109 kJ/mol (slags 7–10). Likewise,
E
D
declines from 159 to 116.5 kJ/mol (slags 1–6) and from 139.5 to 124 kJ/mol (slags 7–10). The mean values of
E
U
and
E
D
correlate with the mean distance between the cations in the melts. On the basis of the proposed alternative model of the conductivity, the O
2–
ions may also transfer electric charge. Preliminary estimates show that the oxygen transport number at 1600°C may exceed 0.1 in some slags.
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