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

Abstract

The Knudsen-cell mass spectrometry was used to study evaporation and thermodynamics of pure liquid Sn, Fe-Sn and Fe-Cu-Sn molten alloys containing up to 20.3 mol% Sn or up to 5 mol% Cu and Sn in a wide temperature range. The thermodynamic properties of the binary melt were approximated by means of the subregular solution model with temperature dependent parameters. The properties of the ternary melt were represented with accuracy not worse than the experimental one by combination of the characteristics of the binary constituents. The obtained results were applied to assessment of the potentialities of simultaneous copper and tin removal from molten steel by means of evaporation. Combination of vacuum treatment of a 160-tons ladle with blowing through the molten metal neutral gases was considered as an example. Two processes are responsible for removal of copper and tin: transfer into gas bubbles, free-rising from the ladle bottom to its surface, and evaporation from molten metal surface, turbulized by blowing-through gas. It was shown that duration of the treatment necessary for a decrease in Cu concentration from 0.6 to 0.3 wt% amounts to ∼1.5 h and is not practically affected by variations in tin content in the range of 0.01 to 0.6wt%. During this time concentration of tin changes insignificantly at any initial content: from 0.6 to ∼0.51, from 0.1 to ∼0.086 or from 0.01 to ∼0.0086 wt%.