| 摘要 |
<P>PROBLEM TO BE SOLVED: To eliminate variations of coarse inclusions in molten steel and to stably reduce the number of inclusions. <P>SOLUTION: The molten steel includes 1.0 to 2.0 mass% Mn, less than 0.003 mass% (excluding 0%) S, 0.002 to 0.01 mass% T.Al, and 0.001 to 0.005 mass% T.O (total oxygen concentration), and is added with Ti in an amount of 0.6 kg/ton or less each time. After Ti is added, the molten steel is agitated for 10 to 20 minutes by the agitation power density of 2 to 4 W/ton to adjust molten steel components to be 0.015 to 0.040 mass% Ti and 0.001 to 0.005 mass% T.O. Then, rare earth elements and/or Zr are added to the component-adjusted molten steel in a range satisfying a relation: 10×A/V<[W<SB POS="POST">(REM)</SB>+0.8×W<SB POS="POST">(Zr)</SB>]/T.O<70×A/V, and the molten steel is agitated for 3 to 7 minutes by the agitation power density of 2 to 3 W/ton after the addition, wherein A is contact area (m<SP POS="POST">2</SP>), V is molten steel volume (m<SP POS="POST">3</SP>), W<SB POS="POST">(REM)</SB>is an addition amount of rare earth elements (kg/ton), and W<SB POS="POST">(Zr)</SB>is an addition amount of Zr (kg/ton). <P>COPYRIGHT: (C)2012,JPO&INPIT |
