Assessment of Oxygen Concentration Unit from Measured Oxygen Activity by Oxygen Sensor Based on Metallurgical Thermodynamics

Taking Celox s oxygen sensor from Heraeus Electro-Nite Shanghai Company Limited as an example,the measured oxygen activity by the sensor has been compared with the reported oxygen activity from literatures,the calculated oxygen activity of aluminum-killed molten steel during a 210 t LF refining process based on [Al]-[O] equilibrium and the calculated oxygen activity of molten steel at steelmaking end-point in an 80 t top-bottom combined blown converter based on [C]-[O] equilibrium.The comparison results show that the measured oxygen activity from Celox oxygen sensor as a representative of commercial oxygen sensors is based on 1%(ω) solution as standard state and one part per million,[10-6 O] as oxygen concentration unit,but not 1%(ω),[%O] as oxygen concentration unit.Therefore,the magnitude of measured oxygen activity by the sensor must be treated as 10-4,rather than the displayed 10-6 in the display device of Celox oxygen sensor under the condition of applying 1%(ω),[%O] as oxygen concentration unit.