Method of melting ultra-low sulfur ultra-low oxygen ultra-low nitrogen steel

摘要

PPROBLEM TO BE SOLVED: To provide a method for treating molten steel by which S, O, N are reduced simultaneously in an industrical manner. PSOLUTION: In a desulfurize-treatment by injecting a flux mainly containing CaO onto molten steel surface, in an RH type vacuum-degassing treating apparatus to the molten steel composed by mass% of 0.002-0.4% C, 0.1-2% Mn, 0.001-1% Si, 0.005% S, 0.005-1% Al, 0.007% N, 0.005% O; to the molten steel before injecting the flux, one or more kinds selected from a group composed of La, Ce and Nd, are added, and after making the concentration thereof to the molten steel to be 0.0005 mass% total thereof, [N]25 ppm is realized by injecting the above flux onto the molten steel surface, and in the case of being the total concentration of the additional elements to 0.0005-0.008 mass%, [S]10 ppm, [O]15 ppm and [N]25 ppm, are realized. PCOPYRIGHT: (C)2009,JPO&INPIT