Abstract: A refining method for decarburization by blowing by using a top-blown lance having a gas-supplying pipe of at least one independent line, wherein the absolute secondary pressure P.sub.0 of nozzle of the lance of at least one line is maintained to be not smaller than 0.7 times but not larger than 2.5 times of the properly expanding absolute secondary pressure P.sub.0p of nozzle of the lance, and the oxygen supplying rate is so changed that a maximum value of the absolute secondary pressure of the nozzle is not smaller than 1.1 times of a minimum value thereof. The top-blown lance used here has not less than 2 but not more than 10 shielding portions arranged in the openings at the end of the lance in a concentric polygonal shape or a concentric circular shape in cross section, has a ratio B/h of the length h (mm) of the short side to the length B (mm) of the long side of the openings separated by the shielding portions of from 10 to 225, has slit-like nozzles of which the ratio (B.multidot.h)/R is from 0.

Abstract: A rapid analysis device for analyzing nonmetallic inclusions in steel by a cold crucible method is combined with a mathematical model, and the quality of cast steel is predicted online by simulating the behavior. of the nonmetallic inclusions by calculation. Further, continuous casting process variables are controlled to minimize the amount of nonmetallic inclusions in the cast steel.

Abstract: An annular nozzle for an oxygen lance, e.g. an oxygen lance for blowing steel in a converter, gives an annular hot spot on the liquid steel in the converter. When exiting the nozzle, the annular jet has disruptions that result in ambient atmosphere being sucked towards the center of the annular jet. Thus, a sub-pressure is prevented which would otherwise prevent the jet from diverging conically. In one embodiment, the nozzle can be switched during a blowing operation between forming a tight jet and forming a divergent jet.