JPS55107715A - Blowing method of dephosphorizer to bottom blowing converter - Google Patents

Abstract

PURPOSE:To achieve dephosphorization effect with less lime use amount and reduce the amount of slag formation by adding part of quicklime for desulfurization at the time when the C content of the bath has decreased at the end period of blowing, at the bottom blowing converter operation. CONSTITUTION:In producing steel by oxidation refining molten iron in the bottom blowing converter, quicklime powder as a slag forming material is blown together with oxygen for refining through the bottom tuyere. Since the FeO formed by the oxygen blown near the tuyere is used preferentially for oxidation decarbonation reaction of C in the bath at the initial period of refining, the oxidation of P in the bath by FeO begins on a full scale from about final 20% of the time when the decarbonation reaction progresses and has entered low carbon region. Hence, at this timing, i.e., at the time when the greater part of the decarbonization reaction ends upon lapse of 80% of blowing time, CaO as flux for dephosphorization slag is blown 4-20kg per ton of molten steel together with oxygen through the bottom tuyere. Slag amount can be less, hence the losses of FeO into the slag are reduced.