| 摘要 |
PURPOSE:To produce inexpensively and stably an extra-low phosphorus steel by adding alloy iron and quicklime as well as iron oxide-contg. flux into a molten low P steel and stirring the molten steel under temp. control in a refining stage thereby dephosphorizing the steel. CONSTITUTION:A molten steel 2 having <=0.020% P level is produced by oxygen blowing in a converter 1, etc. The molten steel is tapped into a ladle 3, etc. Alloy iron 5 and quicklime as well as flux 6 contg. iron oxide such as mill scale or the like are added to the molten steel. The ladle 3 completed of tapping is transferred to a refining stage of a ladle furnace, etc. The molten steel is electrically heated by an electrode 7 and argon or the like is passed to the molten steel from a porous plug 10 mounted in the bottom to stir the molten steel. Dephosphorization reaction is progressed during this time and the treatment is ended at about 1,600 deg.C target temp. The extra-low phosphorus steel contg. <=0.005% P is obtd. by the above-mentioned method. |
