OXYGEN SOLUBILITY IN TITANIUM-CONTAINING Fe-Co MELTS

Thermodynamic analysis of oxygen solutions in titanium- containing Fe-Co melts was carried out. The equilibrium constants of interaction of titanium and oxygen dissolved in the Fe-Co melts, the activity coefficients of titanium and oxygen at infinite dilution, and the interaction parameters characterizing these solutions for melts of different composition at 1873 К were determined for the first time. As the cobalt content in the melt grows the equilibrium constants of interaction of titanium and oxygen are decreased from iron (lgK(FeO·TiO₂) = -7,194; lgK(TiO₂) = -6,125; lgK (Ti₃O₅) = -16,793; lgK (Ti₂O₃) = -10.224) to cobalt (lgK (CoO· TiO₂) = -8.580; lgK (TiO₂) = -7.625; lgK (Ti₃O₅) = -20.073; lgK (Ti₂O₃) = -12.005). Titanium contents in equilibrium points of oxide phases (Fe, Со) О· TiO₂. TiO₂, Ti₃O₅ and Ti₂O₃., were determined. The titanium content in equilibrium point (Fe. Со)О · TiO₂ ↔TiO₂ decreases from 1,0· 10^-4 % Тi в in the iron to 1,9-10^-6 % Ti in cobalt. The titanium content in equilibrium point TiO₂ ↔ Ti₃O₅ increases from 0.0011 % Ti in the iron to 0.0095 % Ti in cobalt. The titanium content in equilibrium point Ti₃O₅ ↔ Ti₂O₃, increases from 0.181 % Ti in the iron to 1.570 % Ti in cobalt. The dependences of the oxygen solubility on the contents of cobalt and titanium in the studied melts were calculated. With increasing cobalt content in melt to 20 %, the deoxidation ability of titanium decreases and then rises with the further addition of cobalt. In iron. Fe-20 % Co and Fe-40 % Co alloys deoxidation ability of titanium is practically the same. The curves of the oxygen solubility in titanium-containing iron-cobalt melts pass through a minimum, which shifts toward lower titanium contents with increasing cobalt content of the melt. Further titanium additions leads to an increase in the oxygen concentration in the melt so that with the higher cobalt content in the melt, the increase in the oxygen content after the minimum is steeper as titanium is added to the melt.

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