| 摘要 |
PROBLEM TO BE SOLVED: To provide a desulfurizing agent not using F and also capable of stably refining an extra-low sulfur steel, and a desulfurizing method using the same.SOLUTION: Provided is a desulfurizing agent for a molten steel having a composition containing, by mass, Cao and Al by 70% or higher in the total of 5 to 20% and at least either or both of metal Al and an Al alloy by 3 to 10% in the total of Al purity in such a manner that the blending amounts of Cao,Aloand Al satisfy inequality (1) and not containing F. Also provided is a desulfurizing method where when the surface of a molten steel sucked to the inside of a reflux type vacuum degassing apparatus is sprayed with the desulfurizing agent together with a carrier gas, and desulfurizing treatment is performed, the composition of the molten steel before being sprayed with the desulfurizing agent is controlled so as to satisfy sol.Al:0.01 to 0.07 mass%, and thereafter, the same is sprayed on the upper face of the molten steel at a feed velocity satisfying inequality 2: 1.3≤(%CaO)/{(%AlO)+0.9×(%Al)}≤2.0(1) and 5≤V×(%Al)≤10(2).SELECTED DRAWING: Figure 1 |
