Technology of Decreasing the (%T.FE) in Slag at The End Point of Oxygen Blowing in the Converter

by Choi, Jea-Bok

Publisher - POSCO, Gwangyang-si, Korea

Category - General Novel

Recently, activity to improve slab quality and steel yield is continuously being conducted by reducing total Fe (FeO) in slag. The time to reach the required [% P] level is slower than that of the [%C] level so that at the time finishing the blowing the total Fe in slag is increased by the excessive oxygen. Thus, this report is focused on how we decrease total Fe in slag at the end point of blowing in the converter. In double slagging process, the test to improve ability of reducing [P] at 1st oxygen blowing proceeds. Firstly, burned lime was input as proper basicity (A) depends on initial [Si]. As burned lime put into the converter the soda ash was also used. We selected the method of inputting soda ash upward because it is impossible to input it though bottom tuyere of converter (250ton).The soda ash put into the converter twice each first and second blowing. The height of oxygen blowing lance and bottom bubbling flow rate were increased at the end of first oxygen blowing to maximize reaction of reducing [%P]. Finally, we developed the slag stablizer that is containing carbon source. It prohibited overflow of slag from slag pot during de-slagging. In first oxygen blowing, the reaction of reducing [P] could be maximized through setting proper basicity (A) and using soda-ash. So it could be possible to decrease the time to reach required level of [P] at the end of converter operation. Eventually, it made result to reduce the total Fe in slag by decreasing excessive oxygen at the end point of blowing in the converter.

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