1990 Volume 76 Issue 11 Pages 1940-1947
Hot metal pretreatment system has recently established applicable to virtually all hot metal produced in Chiba Works. Several developments have been made for establishing an optimum and cost-efficient Q-BOP operations with dephosphorized metal.
The main features of the developments are as follows :
1) Final dephosphorization in Q-BOP is possible by non slag-off blowing method with the use of only a slight amount of dolomite used for coating. By this method, reduction of lime consumption in Q-BOP is achieved.
2) By lowering oxygen flow rate at the final stage of blowing, excess oxidation of steel melt is prevented. Figures of ( T. Fe) in slag and [O] in steel at tapping are lowered by 4% and 100 ppm, respectively.
3) Newly introduced post combustion lance is effective for heat compensation and mouth skull melting.
4) Tapping temperature is successfully decreased by 26°C in manufacturing process of ultra low carbon steel with the aid of the development of KTB, the technology of oxygen blowing through top lance in the vacuum vessel. This technology is effective not only for heat compensation during RH treatment but also for enhancing a decarburization rate in higher carbon region.