**3.4 Chemical equilibrium in the system metal-slag-gas during EML**

Heating, melting and crystallizing a metal melt with slag occur in a controlled gas atmosphere or in vacuum. The exposure time to the onset of chemical equilibrium in the "iron melt-slag melt-gas" system is usually short and does not exceed several minutes. Slag melting occurs due to levitation and heating of iron, liquid slag initially covers a metal drop with a thin film, which can be observed visually, and then it collects in the lower part of the drop and is held in liquid state by interfacial tension. It is this joint behavior of the molten metal and slag plus convection in liquid iron that ensures the rapid achievement of chemical equilibrium in the distribution of sulfur (the usual or radiochemical sulfur isotope 35S). The initial sample for levitation was a capsule of a specially prepared alloy of iron with carbon weighing

~5 g with an opening in which a slag powder weighing 0.35 g was laid; the hole was tightly closed with a thin foil lid of the same alloy. The initial sample was placed in an inductor for subsequent levitation, which, depending on the task, was carried out in vacuum, inert gases and carbon monoxide. After the generator was turned on, levitation and melting of the sample took place with heating to the experimental temperature, and the metal melt took an egg-shaped form, on the lower half of which slag was collected. At the beginning of the experiment, when the capsule was melted, the slag was in the form of a thin film enveloping the entire drop. The experimental time required to reach chemical equilibrium was determined by diffusion in the liquid slag phase.

Using levitation, the sulfur distribution between iron-carbon melts and lime-alumina slag was studied [7, 28, 32]: the dependence of the equilibrium sulfur distribution coefficient on the C content, gas phase composition and temperature.

Experimental results are shown in **Figure 14**. Comparison of the reduced coefficients of the equilibrium distribution of sulfur, obtained by numerical modeling using known thermodynamic data and the experimental equilibrium values of the reduced coefficient of the sulfur distribution, is shown in **Figure 15**. Since the known data for the equilibrium constant of the desulfurization reaction differ by one and a half orders of magnitude, this noticeably affects the reduced sulfur distribution coefficient. On the whole, it is necessary to recognize such a discrepancy as completely admissible and justified. As can be seen in **Figure 15**, in the logarithmic coordinates, the calculated and experimental curves slightly differ in slope, which is due to tolerances in the calculation and experiment [7].

#### **Figure 14.**

*Experimental dependence of the reduced coefficient of distribution of 35S between Fe-C and oxide slag melts on the activity of C in iron. 1—PCo = 1 atm, 2000°C; 2—PHe = 1 atm, 1750°C; 3—PAr = 1 atm, 2000°C.*

#### **Figure 15.**

*Dependence of the experimental (2) and calculated (1) coefficients of the distribution of sulfur between liquid Fe-C and slag on the activity of C in iron at Pco = 1 atm and 2000°C.*

**183**

**Figure 16.**

*Pco = 10<sup>−</sup><sup>7</sup>*

*EBM; 4—Pco = 10<sup>−</sup><sup>7</sup>*

 *atm, 2100°C.*

*Electromagnetic Levitation of Metal Melts DOI: http://dx.doi.org/10.5772/intechopen.92230*

*3.5.1 Melts of Fe-C-O at EML*

**3.5 Reaction of С + О → СО in the melts of Fе and Nb at EML**

alloys in an electron beam setup at 1550°C and a vacuum of 10<sup>−</sup><sup>7</sup>

For comparing EML with crucible melting, the study was made of the influence of the refractory lining on the decarburization kinetics of Fe-C-O samples, which were carried out on melts in corundum crucibles, degassed in vacuum at 1700°С. The data obtained showed that the composition of the products of the decarburization reaction is close to equilibrium; however, the total volume of gases released from the metal depends on the melting method. In melts in a crucible, the gas evolution of CO and CO2 always exceeded the gas evolution during levitation of similar samples. For stable levitation of samples of this system, a setup was used with an inductor inside the chamber; the working pressure in which was 10<sup>−</sup><sup>7</sup>

and a metal temperature of 2000 ± 30°C. The received dependence (see **Figure 16**, area 6) is qualitatively confirmed by the data obtained from the smelting of Fe-C-O

area 3). The calculated dependence of the O content on C for 2000°C confirms the disproportionate relationship between the deoxidation capacity of carbon and the partial pressure of CO in the gas phase. The observed decrease in the O concentration in the metal is due to a change in the deoxidizing ability of C due to a change in Pco. Apparently, the data obtained for melting in an inert atmosphere characterize

The increase in the deoxidizing ability of C dissolved in liquid iron, which occurs as a result of a decrease in Pco over the melt, is observed to a certain limit determined by the kinetics of the CO bubble growth. Since the deoxidizing ability of C is usually expressed by the product of the concentrations of C and O in the metal m = [% C] × [% O], the dependence of the deoxidizing ability on the partial pressure of CO can be expressed by a parabola. Under levitation conditions, when liquid metal does not come into contact with a refractory lining and there is no influence of the lining on the formation of CO bubbles, volume decarburization should prevail, not excluding the evaporation of CO molecules from the surface of a liquid droplet. It is likely that the contribution of evaporation to the removal of CO from a levitated drop of liquid metal should decrease as O adsorption in the surface layer decreases. In low-carbon iron, the formation of CO bubbles in a metal volume is facilitated by thermodynamic and kinetic factors. If the nucleus is comparable in size to large nonmetallic inclusions, the value 2*δ*/*r* is much lower than atmospheric pressure. In this regard, as the partial pressure of CO in the gas phase decreases, the

the maximum possible increase in the deoxidizing ability of C at 2000°C.

*Solubility O in Fe-C-O melts. 1—Pco = 1 atm, 2000°C; 2—Pco = 1 atm, 2000°C; 3—Pco = 10<sup>−</sup><sup>7</sup>*

 *atm, 1600°C (refractory crucible); 5—Pco = 1 atm, 1600°C (refractory crucible); 6—*

atm

atm (see **Figure 16**,

 *atm, 1550°C,* 
