| 摘要 |
<p>PURPOSE: To improve denitrizing efficiency by achieving vacuum degassing after deoxidation is achieved so that the oxygen content in the molten steel may be below a prescribed range according to the sulphur content when achieving the denitrizing treatment of the molten alloy steel when scrap is melted in an electric furnace. CONSTITUTION: When scrap is melted in an electric furnace, and the molten steel whose nitrogen content [N] is >=0.0005(mass%) is denitrized, an alloy is added so as to obtain a prescribed composition under the atmospheric or vacuum condition. Then, in order to increase the denitrizing rate constant dependent on the oxygen content [O] and sulphur content [S] in the molten steel, the deoxidation is achieved so that the oxygen content [O] may be below a range indicated by the inequality I according to the sulphur content [S], and then, Ar gas is blown into the molten steel under the vacuum condition. The denitrizing efficiency becomes >=40% to allow the economical and efficient denitrization. The alloy may bee added after the denitrizing treatment unless the nitrogen content is increased, and the denitrization is achieved by a normal method in which metal Al is only added or metal Al and Ti are successively added.</p> |
