| 摘要 |
PURPOSE:To attain degassing as well as to improve the efficiency of dephosphorization by regulating the amount of free oxygen in molten steel to a specified value and directly flowing a powdery dephosphorizing agent into the molten steel at the lower part of a vacuum degassing vessel. CONSTITUTION:A powdery dephosphorizing agent in a feeder 7 is directly blown into molten steel 3 during degassing in a vacuum degassing vessel 1 from a tuyere 5 through a feed pipe 6 with a carrier gas 8. At this time, the dephosphorizing agent is blown into the molten steel 3 in an undeoxidized state in the early stage of vacuum degassing and the molten steel 3 is dephosphorized after the amount of free oxygen in the molten steel 3 is regulated to 100-800ppm. Thus, dephosphorization and dehydrogenation are simultaneously carried out and high quality steel is obtd.
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