| 摘要 |
PURPOSE:To improve desulfurization efficiency and to execute degassing simultaneously by blowing a powder desulfurizing agent to a molten steel upon lapse of the specific time after throwing of Al at the time of blowing the desulfurizing agent into the molten steel in the lower part in a vacuum degassing vessel. CONSTITUTION:Al is added as a deoxidizing agent into the molten steel 3 to decrease the concn. of Al2O3 and in this state, the desulfurizing agent is blown from a tuyere 5 into the molten steel together with a carrier gas 8 via a supply pipe 6 from a desulfurizing agent supplying device 7. The powder desulfurizing agent is blown upon lapse of the t-minute expressed by t=0.02W+5 (t: the time since the throwing of Al until the start of blowing of the powder desulfurizing agent, W: the weight of the molten steel) after throwing of the Al. The desulfurization of the molten steel 3 is thereby executed with high efficiency and at the same time, the degassing is executed as well to desulfurize and degas the molten steel 3 to about <=10ppm S and about <=1.0ppm H.
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