Development of Automatic Blowing Technique in BOF Based on a Mathematical Model

Abstract

For the endpoint control and the estimation of steel compositions at the end point in BOF with top and bottom blowing, a mathematical model suitable for online application has been developed on the following procedure.
(1) The basic equations of oxygen consumption ratio and temperature increase ratio have been developed. These equations have comprehensive characteristics in both low and high carbon ranges at the final stage of blowing.
(2) An endpoint control model for coinciding the carbon content and temperature at the end point with their aimed values has been developed on the basis of the above mentioned basic equations.
(3) Equations for the estimation of manganese and phosphorus contents at the end point have been developed by using the values obtained by analysis of the steel sampled by sub-lance measurement during blowing and the amount of oxygen which was not consumed for decarburization during the period from sublance measurement to the end point.
At No. 2 BOF shop in Wakayama Steel Works, the models are being used for the automatic blowing and contributes to the reduction of reblow ratio and the improvement of quick tapping ratio.