REFINING METHOD OF MOLTEN STEEL UNDER VACUUM CONDITION, AND TOP-BLOWING LANCE FOR REFINING

摘要

PROBLEM TO BE SOLVED: To efficiently and rapidly perform decarbonization refining by blowing gaseous oxygen to a molten steel from a top-blowing lance under a vacuum condition at a pressure lower than the atmospheric pressure, and to reduce deposition of a base metal on a refining equipment.;SOLUTION: When performing decarbonization refining by blowing gaseous oxygen under the atmosphere at a pressure lower than the atmospheric pressure by using a top-blowing lance having a Laval nozzle 16 installed on a tip thereof, the top-blowing lance having the Laval nozzle of the outlet diameter De (mm) determined by formula (3): De²/Dt²=0.259/[(Pe/Po)^5/7×[1-(Pe/Po)^2/7]^1/2], where Po (kPa) is the nozzle back pressure determined by the oxygen supply rate and the throat diameter Dt, Pe(kPa) is the design atmospheric pressure higher than the average value of the atmospheric pressure Pes when oxygen supply is started from the top-blowing lance and the atmospheric pressure Pee when oxygen supply is completed, and Dt (mm) is the throat diameter.;COPYRIGHT: (C)2006,JPO&NCIPI