PRODUCTION OF EXTRA-LOW PHOSPHORUS STEEL

摘要

PURPOSE:To produce an extra-low phosphorus steel surely and easily by tapping a molten steel which is subjected to converter blowing to have an adequate phosphorus concn. into a ladle and adding an adequate ratio of CaC-CaF2 NaO2.SiO2-FeO flux to the molten steel during the tapping period. CONSTITUTION:A molten iron is charged into a converter 1 and the dephosphorizing flux is added to the molten iron. The molten iron is stirred by the gaseous Ar blown from tuyeres 3 at the furance bottom and gaseous oxygen is blown from a lance 4 to the molten iron to execute oxygen blowing. The molten steel 2 having <=100ppm phosphorus concn. is thus obtd. Such molten steel 2 is tapped into the ladle 5 and the CaO-CaF2-Na2O.SiO2-FeO flux is added at 3-6wt% of the amt. of the converter slag into the molten steel 2 in the ladle 5. The molten steel 2 is stirred and mixed with the flux by the flow during tapping and is dephosphorized to about <=30ppm phosphorus conc. The slag 6 formed by the above-mentioned slag forming is removed by a vacuum suction pipe 7 of VSC by which the rephosphorization is averted.