Abstract
In Nippon Steel Corporation, various types of hot metal pretreatment processes were developed to fit in the condition of each works. In Kimitsu and Yawata Works, simultaneous dephosphorization and desulfurization treatment by lime base flux injection with torpedo car has been put into practical use. In Oita Works, this treatment was modified to make high productivity by high rate injection with snorkel immersed ladle. In Nagoya Works, by use of top-and-bottom blowing converter, highly productive simultaneous dephosphorization and desiliconization treatment was developed.
By the use of coupled reaction model, based on equilibrium relation at interface and mass transfer equations of each element, the characteristics of these processes were analysed. It was clarified that about the dependence of the efficiency of CaO and oxygen for dephosphorization on the ratio of CaO to oxygen content in flux, the tendency of calculation based on small scale experiment was in good agreement with that of industrial values. The differences amoung each treatment type were caused only by the difference of hot metal composition.
In addition, some new blowing methods of converter by the use of dephosphorized hot metal were introduced.
