| 摘要 |
PROBLEM TO BE SOLVED: To surely produce a high quality ultra-low carbon steel having≤0.010 mass% [C] and≤0.030 mass% [P] by using the general pig iron. SOLUTION: When the ultra-low carbon steel containing≤0.010 mass% [C] and≤0.030 mass% [P] is produced by using molten pig iron 2 containing≥0.06 mass% [P], in a top-blowing, oxygen is blown so as to satisfy 0.21≤L/L<SB>0</SB>≤0.24 (wherein L is a cavity depth (m); and L0 is a molten steel depth (m)), in the passing through term from the blowing start. Further, thereafter, the oxygen is blown so as to satisfy 0.26≤L/L<SB>0</SB>≤0.28. In a bottom-blowing, the bottom-blowing gas is blown so as to satisfy 0.02-0.04 Nm<SP>3</SP>/min/ton and 0.017-0.030 Nm<SP>3</SP>/min/mm<SP>2</SP>, in the 85-95% of the passing-through term from the blowing start. Further, thereafter, the bottom-blowing gas is blown so as to satisfy 0.08-0.11 Nm<SP>3</SP>/min/ton and 0.060-0.080 Nm<SP>3</SP>/min/mm<SP>2</SP>. COPYRIGHT: (C)2010,JPO&INPIT |
