METHOD OF CONVERTER STEELMAKING Russian patent published in 2003 - IPC

FIELD: ferrous metallurgy; converter melting of steel at very low content of phosphorus. SUBSTANCE: proposed method includes pouring molten cast iron into converter, delivery of solid metal charge and slag-forming materials, upward oxygen lancing of melt at two stages with intermediate flushing of slag, change of height of lance in the course of lancing above level of melt in killed state and tapping steel from converter. Total consumption of oxygen at first period of lancing is determined from the following relationship: Q₁ = K•(P_is-P_st)•(l•Si+m+n)/P_is•T, where Q_q is total specific consumption of oxygen at first stage of lancing, cu m/t of molten steel; P_is is content of phosphorus in molten cast iron, mass-%; P_st is required content of phosphorus in steel tapped from converter, mass-%; l is specific consumption of molten cast iron, kg/t of molten steel; m is specific consumption of solid metal charge, kg/t of molten steel; n is total specific consumption of slag-forming materials, kg/t of molten steel; Si is content of silicon in molten cast iron, fraction; T is temperature of molten cast iron, C; K is empirical coefficient equal to 12.7-65.3, cu m.C/kg. Duration of first period of lancing is set between 0.1 and 0.8 of total duration of lancing. By the end of 1st and 2nd periods of lancing, lance is lowered from initial upper position to final lower position through distance equal to 0.2-0.6 of initial distance between lance and level of melt in bath in killed state.. After intermediate flushing of slag, at 2nd stage, lancing is performed at total consumption of oxygen Q₂ between 10 and 50 cu m/t of molten steel. Lime and magnesium-containing materials may be used as slag-forming materials at consumption of 55-80 and 10/40 kg/t of molten steel, respectively. It is good practice to deliver slag-forming materials to converter in the amount of 0.4-0.8 of their total specific consumption at first stage of lancing. EFFECT: reduced melting losses. 3 cl, 2 tbl, 1 ex