Bert Coletti

Measurement of ladle slag oxygen activity using electrochemical sensor

Abstract The oxygen activity of the ladle slag may be measured in situ with an electrochemical sensor. The measurement principle of this sensor needs further clarification. An experimental and computational study has been carried out of the contribution of specific components to the oxygen activity of the slag and of the factors that influence oxygen activity measurement with the sensor. Experiments on an industrial and on a laboratory scale show that FeOx, SiO2 and MnO exert a measurable influence on the results. The measurements also show a marked influence of the dissolved oxygen content in the steel. The oxygen activity of the slags has been calculated thermodynamically and compared with the sensor measurements. A systematic difference is observed. A hypothesis on the working principle of the sensor and on the cause of occasional problematic measurement values is proposed.

Reoxidation during ladle treatment

Abstract Cleanliness of steel is mainly determined by the presence of oxide inclusions. The reoxidation of liquid steel before, during and after ladle treatment at the Sidmar steel plant was quantified for three steel grades, as it is a potential source of inclusions. A mass balance calculation was performed to compare the expected and measured steel composition. The total reoxidation was calculated from the reactions of the dissolved elements. A dissimilarity in behaviour of the steel grades was found. The resultant compositions of the slags were calculated and compared with measured compositions. Some differences between computed slag compositions and average measured values are explained. Finally, the relation between the reoxidation and internal cleanliness at the end of ladle treatment was examined.