Abstract: Initial and final oxygen potential in simultaneous dephosphori-zation and desulfurization pretreatment with injection of CaO-based fluxes were measured by using of the oxygen sensors of ZrO₂·MgO solid electrolyte in our laboratory and the thermodynamic analysis were considered. The results shown that:(1) initial oxygen potential is Po₂=10^-8.45~10^-9.7 Pa (10^-13.46~10^-14.76 atm) which is 10~10³ times as high as the oxygen potential calculated from the C/O or Si/O equilibrium reaction. (2) final oxygen potential is Po₂=10^-7~10^-9 Pa (10^-12~10^-14 atm) which is 10~10³ times as high as the initial oxygen potenlip.l and is in good agreement with the optimum oxygen potential in the thermodynamic calculation (Po₂=10^-7.88 Pa (10^-12.88 atm). And (3) dcphosphorization ratio increases, final phosphorus content decreases, and dcsulfurization ratio decreases slightly, final sulfur content increases slightly with increasing of oxygen potential in hot metal.
In addition, optimum oxygen-electrode potential range were analyzed in electrochemistry, and the reaction mechanism of simultaneous dephosphorization and desulfurization in injection pretroatmcnt within hot metal ladle was also discussed.