Evaporation of Copper from Iron Melts

Abstract

The Knudsen-cell mass spectrometry and the integral Knudsen effusion technique under ultra-high neutral vacuum were used to study evaporation of pure Fe, Cu and molten Fe-Cu alloys containing up to 10.1 mol% Cu in the temperature range of 1 440 to 1 916 K. Standard sublimation enthalpies of Fe and Cu and thermodynamic characteristics of the Fe-Cu liquid solution were calculated. The obtained results and literature data were applied for assessment of potentialities of steel decopperizing technology based on evaporation. The time required for a decrease in Cu concentration from 0.6 to 0.3 wt% through evaporation from the exposed surface of a 160-tons ladle into vacuum of 100 Pa amounts to 5 h. Decopperizing can be accelerated by combination of vacuum treatment with blowing neutral gases through the molten metal. Two processes are responsible for removal of copper in this case: transfer into gas bubbles, free-rising from the ladle bottom to its surface, and evaporation from molten metal surface, turbulized by blowing-through gas. The length of treatment required for the above decrease in copper concentration under the most favorable conditions (the highest vacuum over the ladle and the highest velocity of gas-stream blowing through the molten metal used in metallurgy) reduces to 1.5 h.

Potentialities of Simultaneous Removal of Tin and Copper from Molten Iron through Evaporation

“…2 and Table 3. Tin vapor pressure found in the present work and iron vapor pressure from the earlier reports 6,25) were used for the purpose. As all studied alloys are Fe-based solutions, iron vapor pressures measured over the alloys of different composition are closely related and the coefficients A and B in the approximating equation does not practically depend on composition (Table 1).…”

“…(3) and the description of the Fe-Cu system from Ref. 6) and assuming that the Cu-Sn melt is a regular solution, the excess Gibbs energy (in kJ/mol) of the ternary solution was expressed as …”

“…As in Ref. 6), a ladle of 160 metric tons in capacity and of 3.18 m in inner diameter, filled with metal to the height of 2.91 m will be considered here. The analysis will be carried out for 1 873 K and the pressure, p atm.…”

“…The real vaporization rate of copper under pressure in the gaseous phase changing from 0.2 MPa to 100 Pa were also assessed in Ref. 6) on the bases of data 34) and Eq. (10) It was found that for the pressure range under consideration k(Cu) is equal to 7.4 · 10 Ϫ7 m/s at 1 873 K. Unfortunately there are no data similar to Ref.…”

“…An active search is underway now for technology of removal of these elements founded on evaporation. [1][2][3][4][5] On the basis of the detailed study of the thermodynamics of Fe-Cu solution the potentialities of decopperizing through evaporation were recently analyzed 6) and it was shown that this type technology is feasible although quite time consuming. For consideration of simultaneous refinement of steel from Cu and Sn, data on the thermodynamic properties of Fe-Cu-Sn and Fe-Sn liquid solutions are required.…”