JPS55125215A - Production of low nitrogen steel - Google Patents

Abstract

PURPOSE:To suppress the nitrogen absorption in the process from blowing to casting and produce the low-nitrogen steel by applying treatment, such as blowing of gas or sealing with Ar gas, to the inside of the converter from the end period of blowing up to ending, the tapping hole in tapping process, the inside of ladle, etc. CONSTITUTION:Ar gas is blown into a converter 2 from the end period of blowing up to its ending by way of the nozzle 5 mounted to the cover 4 closing the tapping hole 12 of the converter 2 of Fig. A. Next, the corer 4 of the hole 21 is removed as shown by Fig. B and molten steel is poured 21 while Ar gas is being spouted from the uppermost of the cover 61 provided to the top of the ladle 6. Further Ar gas is also spouted 62 from the bottom of the ladle 62 perfectly shut the molten steel from the stmosphere. Nect, at the time of restoring pressure after evacuating the molten steel 63 in the ladle 6 through a vacuum vessel 7 as shown by Fig. C, the shutoff valve 711 of an exhaust system 71 is closed and Ar gas 722 is supplied into the vessel 7 to complete the degassing treatment. Further, at the time of pouring molten steel from the ladle 6 into the mold, Ar gas is blown into the mold. As a result of this, nitrogen absorption may be prevented as far as possible in a series of steel-making processes and the low-nitrogen steel may be stably supplied.